开关电源设计及其英文翻译
开关稳压电源外文文献及翻译(英文)
DC Switching Power Supply Protection TechnologyPosted:2006—2—26 10：57:00 visit：665 chinese Version Related NewsAbstract：The DC switching power supply protection system is proposed to protect the system design principles and machine protection measures，analysis of switching power supply in the range of protected characteristics and design method, introduced several practical protection of circuit.Keywords：switching power supply protection circuit system design1 IntroductionDC switching regulator used in the price of more expensive high—power switching devices, the control circuit is also more complex，In addition, the load switching regulators are generally used a large number of highly integrated devices installed electronic systems. Transistors and integrated device tolerance of electricity, less heat shocks。
开关电源设计及其英文翻译
开关电源设计及其英文翻译Switching Power Supply DesignSwitching power supply work in high frequency, high pulse state, are analog circuits in a rather special kind. Cloth boards to follow the principle of high-frequency circuit wiring.1, layout:Pulse voltage connection as short as possible, including input switch connected to the transformer, output transformer to the rectifier tube cable. Pulse current loop as small as possible such as the input filter capacitor is returned to the transformer to the switch capacitor negative. Some out-ended output transformers are the output rectifier to the output capacitor back to transformer circuit X capacitor as close as possible to the input switching power supply, input lines should be avoided in parallel with other circuits, should be avoided. Y capacitor should be placed in the chassis ground terminal or FG connectors. A total of touch induction and transformer to maintain a certain distance in order to avoid magnetic coupling. Such as poor handling of feeling in between inductor and transformer plus a shield, over a number of EMC performance for power supply to the greater impact.General the output capacitor can be used the other two a close rectifier output terminal should be close to, can affect the power supply output ripple index, two small capacitor in parallel results should be better than using a large capacitor. Heating devices to maintain a certain distance, and electrolytic capacitors to extend machine life, electrolytic capacitors is the switching power supply bottleneck life, such as transformers, power control, high power resistors and electrolytic to maintain the distancerequired between the electrolyte leaving space for heat dissipation , conditions permitting, may be placed in the inlet.Control part to pay attention to: Weak signal high impedance circuit connected to sample the feedback loop as short as in the processing as far as possible avoid interference, the current sampling signal circuits, in particular the current control circuit, easy to deal with some unexpected bad The accident, which had some skill, now to 3843 the circuit example shown in Figure (1) Figure 1 better than Yu Figure 2, Figure 2 Zai full time by observing the current waveform oscilloscope Mingxian superimposed spikes, Youyuganrao limited flow ratio design Zhi Dian low, Figure 1 there is no such phenomenon, there are switch drive signal circuit, switch resistance should be close to the switch driver can switch the work to improve the reliability of this and the high DC impedance voltage power MOSFET driver characteristics.Second, routingAlignment of current density: now the majority of electronic circuit board using insulated copper constitute tied. Common PCB c opper thickness of 35μm, the alignment valuecan be obtained in accordance with 1A/mm experience the value of current density, the specific calculations can be found in textbooks. T o ensure the alignment principles of mechanical strength should be greater than or equal to the width of 0.3mm (other non-power supply circuit board may be smaller minimum line width). PCB copper thickness of 70μm is also common in switching power supply, then the current density can be higher.Add that, now Changyong circuit board design tool design software generally items such as line width, line spacing, hole size and so dry plate Guo Jin Xing parameters can be set. In thedesign of circuit boards, design software automatically in accordance with the specifications, can save time, reduce some of the workload and reduce the error rate.Generally higher on the reliability of lines or line density wiring can be used double panel. Characterized by moderate cost, high reliability, to meet most applications.The ranks of some of the power module products are also used plywood, mainly to facilitate integration of power devices such as transformer inductance to optimize wiring, cooling and other power tube. Good consistency with the craft beautiful, transformer cooling good advantage, but its disadvantage is high cost, poor flexibility, only suitable for industrial mass production.Single-sided, the market circulation of almost universal switching power supply using single-sided circuit board, which has the advantage of lower costs in the design and production technology are also taken some measures to ensure its performance.Single PCB design today to talk about some experience, as a single panel with low cost, easy-to-manufacture features, the switching power supply circuit has been widely used, because of its side tied only copper, the device's electrical connections, mechanical fixation should rely on the copper layer, the processing must be careful.To ensure good performance of the mechanical structure welding, single-sided pad should be slightly larger to ensure that the copper and substrate tied good focus, and thus will not be shocked when the copper strip, broken off. General welding ring width should be greater than 0.3mm. Pad diameter should be slightly larger than the diameter of the device pins, but not too large, to ensure pin and pad by the solder connection betweenthe shortest distance, plate hole size should not hinder the normal conditions for the degree of investigation, the pad diameter is generally greater than pin diameter 0.1-0.2mm. Multi-pin device to ensure a smooth investigation documents can also be larger.Electrical connection should be as wide as possible, in principle, should be larger than the width of pad diameter, special circumstances should be connected in line with the need to widen the intersection pad (commonly known as Generation tears), to avoid breaking certain conditions, line and pad. Principle of minimum line width should be greater than 0.5mm.Single-board components to be close to the circuit board. Need overhead cooling device to device and circuit board between the pins plus casing, can play a supporting device and increase the dual role of insulation to minimize or avoid external shocks on the pad and the pin junction impact and enhance the firmness of welding. Circuit board supporting the weight of large parts can increase the connection point, can enhance joint strength between the circuit board, such as transformers, power device heat sink.Single-sided welding pins without affecting the surface and the shell spacing of the prior conditions, it can be to stay longer, the advantage of increased strength of welded parts, increase weld area and immediately found a Weld phenomenon. Shear pin long legs, the welding force smaller parts. In T aiwan, the Japanese often use the device pins in the welding area and the circuit board was bent 45 degrees, and then welding process, its reasoning Ibid. Double panel today to talk about the design of some of the issues, in relatively high number of requests, or take the line density of the larger application environments usingdouble-sided PCB, its performance and various indicators of a lot better than a single panel.Two-panel pad as holes have been high intensity metal processing, welding ring smaller than a single panel, the pad hole diameter slightly larger in diameter than pins, as in the welding process solder solution conducive to penetrate through the top hole solder pad to increase the welding reliability. But there is a disadvantage if the hole is too large, wave soldering tin when the jet impact in the lower part of the device may go up, have some flaws.High current handling of alignment, line width in accordance with pre-quote processing, such as the width is not enough to go online in general can be used to increase the thickness of tin plating solution, the method has a good variety of1. Will take the line set to pad property, so that when the circuit board manufacturing solder alignment will not be covered, the whole hot air normally be tin plated.2. In the wiring by placing pads, the pad is set to take in line shape, pay attention to the pad holes set to zero.3. In the solder layer placed on line, this method is the most flexible, but not all PCB manufacturers will understand your intentions, needed captions. Place the line in the solder layer of the site will not coated solder tinning line several methods as above, to note that, if the alignment of a very wide all plated with tin in solder after the solder will bond a lot and distribution is very uneven, affecting appearance. Article tin can be used generally slender width in the 1 ~ 1.5mm, length can be determined according to lines, tin part of the interval 0.5 ~ 1mm Double-sided circuit board for the layout, the alignment provides a very selective, make wiring more reasonable. On theground, the power ground and signal ground must be separated, the two to converge in filter capacitors, in order to avoid a large pulsed current through the signal ground connection instability caused by unexpected factors, the signal control circuit grounding point as far as possible, a skill, as far as possible the alignment of the non-grounded wiring layer in the same place, the last shop in another layer of earth.Output line through the filter capacitors, the general first, and then to the load, input line must also pass capacitor, to the transformer, the theoretical basis is to ripple through trip filter capacitor.Voltage feedback sampling, in order to avoid high current through the alignment of the feedback voltage on the sampling point must be the most peripheral power output to increase the load effect of target machine.Alignment change from a wiring layer to another wiring layer generally used hole connected, not through the pin pad device to achieve, because the plug in the device may be damaged when the relationship between this connection, there is current in every passage of 1A, at least two through-hole, through hole diameter is greater than the principle of 0.5mm, 0.8mm generally processed ensure reliability.Cooling devices, in some small power supply, the circuit board traces can be and cooling, characterized by the alignment as generous as possible to increase the cooling area is not coated solder, conditions can even be placed over holes, enhanced thermal conductivity .Today to talk about the aluminum plate in the switching power supply application and multilayer printed circuit in the switching power supply applications.Aluminum plate by its own structure, has the following characteristics: very good thermal conductivity, single Mianfu copper, the device can only be placed in tied copper surface, can not open electrical connection hole so as not to place jumper in accordance with a single panel.Aluminum plate is generally placed patch device, switch, the output rectifier heat conduction through the substrate to go out, very low thermal resistance, high reliability can be achieved. Transformer with planar chip structure, but also through substrate cooling, the temperature is lower than the conventional, the same size transformer with a large aluminum plate structure available output power. Aluminum plate jumper bridge approach can be used. Aluminum plate power are generally composed by the two PCB, another one to place the control circuit board, through the physical connection between the two boards is integrated.As the excellent thermal conductivity of aluminum plate, in a small amount of manual welding more difficult, solder cooling too fast and prone to problems of a simple and practical way of existing, an ironing ordinary iron (preferably temperature regulation function), over and iron for the last, fixed, and t emperature to 150 ℃ and above the aluminum plate on the iron, heating time, and then affix the components according to conventional methods and welding, soldering iron temperature is appropriate to the device easy to , is too high when the device may be damaged, or even copper strip aluminum plate, the temperature is too low welding effect is not good, to be flexible.Recent years, with the multi-layer circuit board applications in switching powersupply circuit, printed circuit transformer makes it possible,due to multilayer, smaller spacing also can take advantage of Bianya Qi window section, the main circuit board can be re- Add 1-2 formed by the multilayer printed coil to use the window, the purpose of reducing circuit current density, due to adopt printed coil, reducing manual intervention, transformers consistency, surface structure, low leakage inductance, coupling good . Open-type magnetic core, good heat dissipation. Because of its many advantages, is conducive to mass production, it is widely used. But the research and development of large initial investment, not suitable for small-scale health.Switching power supply is divided into, two forms of isolation and non-isolated, isolated here mainly to talk about switching power supply topologies form below,non-specified, are to isolate the power. Isolated power supply in accordance with the structure of different forms, can be divided into two categories: a forward and flyback. Flyback transformer primary side means that when the Vice-edge conduction cut-off, transformer storage. Close of the primary, secondary side conduction, the energy released to the load of work status, general conventional flyback power multiplex, twin-tube is not common. Forward refers to the primary conduction in transformer secondary side while the corresponding output voltage is induced into the load, the direct transfer of energy through the transformer. According to specifications can be divided into conventional forward, including the single-transistor forward, Double Forward. Half-bridge, bridge circuits are all forward circuit.Forward and flyback circuits have their own characteristics in the process of circuit design to achieve optimal cost-effective, can be applied flexibly. Usually in the low-power flyback can beadopted. Slightly larger forward circuit can use a single tube, medium-power can use Double Forward circuit or half-bridge circuit, low-voltage push-pull circuit, and the half-bridge work in the same state. High power output, generally used bridge circuit, low voltage can be applied push-pull circuit.Flyback power supply because of its simple structure, and to cut the size of a similar size and transformer inductance, the power supply in the medium has been widely applied. Presentation referred to in some flyback power supply can do dozens of watts, output power exceeding 100 watts would be no advantage to them difficult. Under normal circumstances, I think so, but it can not be generalized, PI's TOP chips can do 300 watts, an article describes the flyback power supply can be on the KW, but not seen in kind. Power output and the output voltage level.Flyback power transformer leakage inductance is a critical parameter, because the power needs of the flyback transformer stored energy, to make full use of transformer core, the general must be open in the magnetic circuit air gap, the aim is to change the core hysteresis back line of the slope, so that transformers can withstand the impact of a largepulse current, which is not core into saturation non-linear state, the magnetic circuit in the high reluctance air gap in the state, generated in the magnetic flux leakage is much larger than completely closed magnetic circuit .Transformer coupling between the first pole is the key factor determining the leakage inductance, the coil to be very close as far as possible the first time, the sandwich can be used around the law, but this would increase the distributed capacitance transformer. Use core as core with a long window, can reduce the leakage inductance, such as the use of EE, EF, EER, PQ-based EItype magnetic core effective than good.The duty cycle of flyback power supplies, in principle, the maximum duty cycle of flyback power supply should be less than 0.5, otherwise not easy loop compensation may be unstable, but there are some exceptions, such as the U.S. PI has introduced the TOP series chip can work under the conditions of duty cycle is greater than 0.5.Duty cycle by the transformer turns ratio to determine former deputy side, I am an anti-shock view is, first determine the reflected voltage (output voltage reflected through the transformer coupling the primary voltage value), reflecting a certain voltage range of voltage increase is duty cycle increases, lower power loss. Reduce the reflected voltage duty cycle decreases, increases power loss. Of course, this is a prerequisite, when the duty cycle increases, it means that the output diode conduction time, in order to maintain output stability, more time will be to ensure that the output capacitor discharge current, the output capacitor will be under even greater high-frequency ripple current erosion, while increasing its heat, which in many circumstances is not allowed.Duty cycle increases, change the transformer turns ratio, transformer leakage inductance will increase, its overall performance change, when the leakage inductance energy large enough, can switch to fully offset the large account space to bring low-loss, no further increase when the meaning of duty, because the leakage inductance may even be too high against the peak voltage breakdown switch. Leakage inductance as large, may make the output ripple, and other electromagnetic indicators deteriorated. When the duty hours, the high RMS current through the switch, transformer primary current rms andlowered the converter efficiency, but can improve the working conditions of the output capacitor to reduce fever. How to determine the transformer reflected voltage (duty cycle) Some netizens said switching power supply feedback loop parameter settings, work status analysis. Since high school mathematics is rather poor, "Automatic Control Theory," almost on the make-up, and for the door is still feeling fear, and now can not write a complete closed-loop system transfer function, zero for the system, the concept of feeling pole vague, see Bode plot is only about to see is a divergence or convergence, so the feedback compensation can not nonsense, but there are a number of recommendations. If you have some mathematical skills, and then have some time to learn then the University of textbooks,"Principles of Automatic Control" digest look carefully to find out, combined with practical switching power supply circuit, according to the work of state for analysis. Will be harvested, the Forum has a message, "coach feedback loop to study the design, debugging," in which CMG good answer, I think we can reference.Then today, on the duty cycle of flyback power supply (I am concerned about the reflected voltage, consistent with the duty cycle), the duty cycle with the voltage selection switch is related to some early flyback switching power supply using a low pressure tube, such as 600V or 650V AC 220V input power as a switch, perhaps when the production process, high pressure tubes, easy to manufacture, or low-pressure pipes are more reasonable conduction losses and switching characteristics, as this line reflected voltage can not be too high, otherwise the work order to switch the security context of loss of power absorbing circuit is quite impressive.Reflected voltage 600V tube proved not more than 100V, 650V tube reflected voltage not greater than 120V, the leakage inductance voltage spike when the tubes are clamped at 50V 50V working margin. Now that the MOS raise the level of manufacturing process control, flyback power supplies are generally used 700V or 750V or 800-900V the switch. Like this circuit, overvoltage capability against a number of switching transformer reflected voltage can be done a bit higher, the maximum reflected voltage in the 150V is appropriate, to obtain better overall performance.TOP PI's recommendation for the 135V chipset with transient voltage suppression diode clamp. But his evaluation board generally reflected voltage to be lower than the value at around 110V. Both types have their advantages and disadvantages: Category: shortcomings against over-voltage, low duty cycle is small, a large pulse current transformer primary. Advantages: small transformer leakage inductance, electromagnetic radiation and low ripple index higher switch loss, the conversion efficiency is not necessarily lower than the second.The second category: a large number of shortcomings of power loss, a large number of transformer leakage inductance, the ripple worse. Advantages: Some strong against over-voltage, large duty cycle, lower transformer losses and efficiency higher.Reflected voltage flyback power supply and a determining factorReflected voltage flyback power supply with a parameter related to that is the output voltage, output voltage, the lower the larger the transformer turns ratio, the greater the transformer leakage inductance, switch to withstand higher voltage breakdown switch is possible to absorb power consumption ishigher, has the potential to permanently absorb the circuit power device failure (particularly with transient voltage suppression diode circuits). In the design of low-voltage low-power flyback power output optimization process must be handled with care, its approach has several:1, using a large core of a power level lower leakage inductance, which can improve the low-voltage flyback power conversion efficiency, reduce losses, reduce output ripple and improve multi-output power of the cross regulation in general is common in household appliances with a switch power, such as CD-ROM drive, DVB set-top boxes.2, if the conditions were not increased core, can reduce the reflected voltage, reducing the duty cycle. Reduce the reflected voltage can reduce the leakage inductance but may reduce the power conversion efficiency, which is a contradiction between the two, must have an alternative process to find a suitable point, replace the transformer during the experiment can detect the transformer original side of the anti-peak voltage, peak voltage to minimize the anti-pulse width, and magnitude of the work safety margin increase converter. Generally reflected voltage 110V when appropriate.3, enhance the coupling, reducing losses, the introduction of new technologies, and the routing process, transformers to meet the security specifications will between the primary and secondary side to insulation measures, such as pad tape, plus side air insulation tape. These will affect the performance of transformer leakage inductance, the reality can be used in production around the primary winding secondary wrapping method. Or sub-system with a triple insulated wire wound to remove the insulation between the initial level, can enhance thecoupling, even use wide copper winding.The article refers to low voltage output is less than or equal to 5V output, as this type of small power supply, my experience is that the power output of more than 20W output can use a forward, get the best value for money, of course, this is not the right decision , and personal habits, relationship between the application environment, the next time to talk about the flyback power supply with a magnetic core, magnetic circuit air gap opening some understanding, I hope you receive adequate guidance.Flyback power transformer core magnetization state at work in one way, it needs to open the air gap magnetic circuit, similar to the pulsating direct current sensor. Part of the magnetic coupling through the air gap. Why I understand the principle of open air gap as follows: As the power ferrite also has a similar rectangle of the operating characteristics (hysteresis loop), operating characteristics curve in the Y-axis magnetic induction (B), now the general production process saturation point in 400mT above, the general value in the design of this value should be more appropriate in the 200-300mT, X-axis magnetic field strength (H) the value of current intensity is proportional to the magnetization. Open magnetic circuit air gap equal to the magnetic hysteresis loop to the X axis tilt, in the same magnetic induction intensity, can withstand a greater magnetizing current, equivalent to core store more energy, this energy cut-off switch When spilled into the load through the transformer secondary circuit, flyback power core to open the air gap is twofold. One is to transfer more energy, and the second to prevent the core into saturation.Flyback Power Transformer magnetization state in one way,not only to pass through the magnetic coupling energy, is also responsible for input and output isolation voltage transform multiple roles. Therefore, the treatment gap need to be very careful, the air gap leakage inductance can become too large, increase the hysteresis loss, iron loss, copper loss increases, affecting the power of the whole performance. Air gap is too small has the potential to transformer core saturation, resulting in damage to powerThe so-called flyback power supply is continuous and discontinuous mode transformer working conditions, working in full load condition in the power transformer complete transfer, or incomplete transmission mode. General design of the working environment, conventional flyback power supply should work in continuous mode, this switch, circuit loss are relatively small, and can reduce the stress of work input and output capacitors, but that there are some exceptions.Requires in particular that: As the characteristics of the flyback power supply is also more suitable for design into a high-voltage power supply, and high-voltage power transformers generally work in discontinuous mode, I understand the need for as high voltage power supply output voltage of the rectifier diodes. Because of the manufacturing process characteristics, high-tension diode, reverse recovery time is long, low speed, the current continuous state, the diode has a positive bias in the recovery, reverse recovery energy loss is very large, is not conducive to converter performance increase, ranging from reduced conversion efficiency, rectifiers, severe fever, weight is even burnt rectifier. As in the intermittent mode, the diode is reverse biased under zero bias, loss can be reduced to a relatively low level. Therefore, high voltage power supply work indiscontinuous mode, and the frequency can not be too high.Another type of flyback power supply work in the critical state, the general type of power supply work in FM, or FM-width-modulated dual-mode, a number of low-costself-excitation power (RCC) is often used this form in order to ensure stable output transformer As the operating frequency, output current or input voltage change, close to the fully loaded transformer is always maintained at between continuous and intermittent, this power is only suitable for small power output, otherwise the handling characteristics of electromagnetic compatibility will be a headacheFlyback switching power supply transformer should work in continuous mode, it required relatively large winding inductance, of course, is to some extent continuous, excessive pursuit of absolute continuity is not realistic, may need a great core, very much coil turns, accompanied by a large leakage inductance and distributed capacitance, worth the trouble. So how does this parameter to determine, through repeated practice, and analysis of peer design, I think, in the nominal voltage input, the output reached 50% and 60% transformer from intermittent, continuous state of transition to more appropriate. Or at thehighest input voltage state, the full output, the transformer can transition to the continuous state on it.开关电源状态，电源工作在高频率，高脉冲的模拟电路的一个比较特殊的一种。
开关电源翻译5-9页
IntroductionThe never-ending drive towards smaller and lighterproducts poses severe challenges for the power supply designer. In particular, disposing of excess heat generated by power semiconductors is becoming more and more difficult. Consequently it is important that the power supply be as small and as efficient as possible, and over the years power supply engineers have responded to these challenges by steadily reducing the size and improving the efficiency of their designs.Switching power supplies offer not only higher efficiencies but also greater flexibility to the designer. Recent advances in semiconductor, magnetic and passive technologies make the switching power supply an ever more popular choice in the power conversion arena.This guide is designed to give the prospective designer an overview of the issues involved in designing switchmode power supplies. It describes the basic operation of the more popular topologies of switching power supplies, their relevant parameters, provides circuit design tips, and information on how to select the most appropriate semiconductor and passive components. The guide also lists the ON Semiconductor components expressly built for use in switching power supplies.Linear versus SwitchingPower SuppliesSwitching and linear regulators use fundamentally different techniques to produce a regulated output voltage from an unregulated input. Each technique has advantages and disadvantages, so the application will determine the most suitable choice.Linear power supplies can only step-down an input voltage to produce a lower output voltage. This is done by operating a bipolar transistor or MOSFET pass unit in its linear operating mode; that is, the drive to the pass unit is proportionally changed to maintain the required output voltage. Operating in this mode means that there is always a headroom voltage, Vdrop, between the input and the output. Consequently the regulator dissipates a considerable amount of power, given by (Vdrop Iload).This headroom loss causes the linear regulator to only be 35 to 65 percent efficient. For example, if a 5.0 VSMPSRM A low drop-out (LDO) regulator uses an improved output stage that can reduce Vdrop to considerably less than 1.0 V. This increases the efficiency and allows the linear regulator to be used in higher power applications.Designing with a linear regulator is simple and cheap, requiring few external components. A linear design is considerably quieter than a switcher since there is no high-frequency switching noise. Switching power supplies operate by rapidly switching the pass units between two efficient operating states: cutoff, where there is a high voltage across the pass unit but no current flow; and saturation, where there is a high current through the pass unit but at a very small voltage drop. Essentially, the semiconductor power switch creates an AC voltage from the input DC voltage. This AC voltage can then be stepped-up or down by transformers and then finally filtered back to DC at its output. Switching power supplies are much more efficient, ranging from 65 to 95 percent.The downside of a switching design is that it is considerably more complex. In addition, the output voltage contains switching noise, which must be removed for many applications.Although there are clear differences between linear and switching regulators, many applications require both types to be used. For example, a switching regulator may provide the initial regulation, then a linear regulator may provide post-regulation for a noise-sensitive part of the design, such as a sensor interface circuit.Switching Power Supply FundamentalsThere are two basic types of pulse-width modulated(PWM) switching power supplies,forward-mode and boost-mode. They differ in the way the magnetic elements are operated. Each basic type has its advantages and disadvantages.The Forward-Mode ConverterThe forward-mode converter can be recognized by thepresence of an L-C filter on its output. The L-C filter creates a DC output voltage, which is essentially the volt-time average of the L-C filter's input AC rectangular waveform. This can be expressed as:regulator has a 12 V input and is supplying 100 mA, itmust dissipate 700 mW in the regulator in order todeliverVout [ Vin @ duty cycle (eq. 1)500 mW to the load , an efficiency of only 42 percent. The cost of the heatsink actually makes the linear regulator uneconomical above 10 watts for small applications. Below that point, however, linear regulators are cost-effective in step-down applications. The switching power supply controller varies the duty cycle of the input rectangular voltage waveform and thus controls the signal's volt-time average.The buck or step-down converter is the simplest forward-mode converter, which is shown in Figure 1.5SMPSRML OSWV inI on D I offR loadC outPower Switch ONV satPower Switch OFFPower Switch ONPower SwitchOFFTIMEV fwdI pkI loadI minPower SWDiode Power SW DiodeTIMEFigure 1. A Basic Forward-Mode Converter and Waveforms (Buck Converter Shown)Its operation can be better understood when it is broken into two time periods: when the power switch is turned on and turned off. When the power switch is turned on, the input voltage is directly connected to the input of the L-C filter. Assuming that the converter is in a steady-state, there is the output voltage on the filter'sclamped when the catch diode D becomes forwardbiased. The stored energy then continues flowing to the output through the catch diode and the inductor. Theinductor current decreases from an initial value i pk and isgiven by:output. The inductor current begins a linear ramp from aniL(off) + ipk * Voutt L0 v t v toff(eq. 3)initial current dictated by the remaining flux in the inductor. The inductor current is given by:The off period continues until the controller turns the power switch back on and the cycle repeats itself. iL(on) + Vin * Vout t ) iinit( L )0 v t v ton(eq. 2)The buck converter is capable of over one kilowatt ofoutput power, but is typically used for on-board regulatorDuring this period, energy is stored as magnetic flux within the core of the inductor. When the power switch is turned off, the core contains enough energy to supply the load during the following off period plus some reserve energy.When the power switch turns off, the voltage on the input side of the inductor tries to fly below ground, but isapplications whose output powers are less than 100 watts. Compared to the flyback-mode converter, the forward converter exhibits lower output peak-to-peak ripple voltage. The disadvantage is that it is a step-down topology only. Since it is not an isolated topology, for safety reasons the forward converter cannot be used for input voltages greater than 42.5 VDC.6SMPSRM The Flyback-Mode Converter different fashion from the forward-mode converter. TheThe basic flyback-mode converter uses the same most elementary flyback-mode converter, the boost orcomponents as the basic forward-mode converter, but in step-up converter, is shown in Figure 2.a different configuration. Consequently, it operates in aLDC outV in SW R loadI load I onI offV inPower Switch ON V flbk(V out)PowerSwitchON PowerV sat Diode Switch DiodeON ON ONTIMEI pkI loadTIME Figure 2. A Basic Boost-Mode Converter and Waveforms (Boost Converter Shown)Again, its operation is best understood by considering the "on" and "off" periods separately. When the power switch is turned on, the inductor is connected directly across the input voltage source. The inductor current thenrises from zero and is given by: the output rectifier when its voltage exceeds the output voltage. The energy within the core of the inductor is then passed to the output capacitor. The inductor current during the off period has a negative ramp whose slope isgiven by:iL(on) + Vint L v t v 0on (eq. 4)iL(off) +(Vin * Vout)L (eq. 6)Energy is stored within the flux in the core of theinductor.The peak current, i pk, occurs at the instant the power switch is turned off and is given by: The energy is then completely emptied into the output capacitor and the switched terminal of the inductor fallsipk + VinLton (eq. 5) back to the level of the input voltage. Some ringing is evident during this time due to residual energy flowingWhen the power switch turns off, the switched side of through parasitic elements such as the stray inductancesthe inductor wants to fly-up in voltage, but is clamped by and capacitances in the circuit.7SMPSRMWhen there is some residual energy permitted to remain within the inductor core, the operation is called continuous- mode . This can be seen in Figure 3.Energy for the entire on and off time periods must be stored within the inductor. The stored energy is defined by:to a 50 percent duty cycle. There must be a time period when the inductor is permitted to empty itself of its energy .The boost converter is used for board-level (i.e., non-isolated) step-up applications and is limited to less than 100-150 watts due to high peak currents. Being a non-isolated converter, it is limited to input voltages ofEL + 0.5L @ ipk2(eq. 7)less than 42.5 VDC. Replacing the inductor with a The boost-mode inductor must store enough energy tosupply the output load for the entire switching period (t on+ t off ). Also, boost-mode converters are typically limitedV inPower transformer results in a flyback converter, which may be step-up or step-down. The transformer also provides dielectric isolation from input to output.V flbk (V out )PowerSwitch Diode Switch Diode ON ON ON ON TIMEV satI pkTIMEFigure 3. Waveforms for a Continuous-Mode Boost ConverterCommon SwitchingPower Supply TopologiesA topology is the arrangement of the power devices and their magnetic elements. Each topology has its own merits within certain applications. There are five major factors to consider when selecting a topology for aparticular application. These are:1. Is input-to-output dielectric isolation required forthe application? This is typically dictated by the safety regulatory bodies in effect in the region.2. Are multiple outputs required?3. Does the prospective topology place a reasonablevoltage stress across the power semiconductors?4. Does the prospective topology place a reasonablecurrent stress upon the power semiconductors?5. How much of the input voltage is placed acrossthe primary transformer winding or inductor?Factor 1 is a safety-related issue. Input voltages above 42.5 VDC are considered hazardous by the safety regulatory agencies throughout the world. Therefore, only transformer-isolated topologies must be used above this voltage. These are the off-line applications where the power supply is plugged into an AC source such as a wall socket.Multiple outputs require a transformer-based topology. The input and output grounds may be connected together if the input voltage is below 42.5 VDC. Otherwise full dielectric isolation is required.8Factors 3, 4 and 5 have a direct affect upon the reliability of the system. Switching power supplies deliver constant power to the output load. This power is then reflected back to the input, so at low input voltages, the input current must be high to maintain the output power. Conversely, the higher the input voltage, the lower the input current. The design goal is to place as much as possible of the input voltage across the transformer or inductor so as to minimize the input current.Boost-mode topologies have peak currents that are about twice those found in forward-mode topologies. This makes them unusable at output powers greater than 100-150 watts.SMPSRM Cost is a major factor that enters into the topology decision. There are large overlaps in the performance boundaries between the topologies. Sometimes the most cost-effective choice is to purposely design one topology to operate in a region that usually is performed by another. This, though, may affect the reliability of the desired topology.Figure 4 shows where the common topologies are used for a given level of DC input voltage and required output power. Figures 5 through 12 show the common topologies. There are more topologies than shown, such as the Sepic and the Cuk, but they are not commonly used.1000Half-Bridge100 42.510FlybackNon-Isolated Full-BridgeBuckFull-BridgeVery HighPeak Currents10 100 1000OUTPUT POWER (W)Figure 4. Where Various Topologies Are Used9i L(off)=i pk -V out t / L 0≤ t≤ t off (eq.3) i L(on) = V in t / L ≤ t ≤ 0on(eq.4) i pk = V in t on / L (eq.5)i L(off) = (V in - V out) / L (eq.6)E L = 0.5L · i pk2(eq.7)。
开关电源英文原著对应中文翻译
TOP200-4/14TOPSwitch系列三端离线式PWM开关产品的优点离散开关的低成本替代品• 比其他产品少20到50个组件-降低了成本，提高了可靠性• 源连接选项卡和受控导通的MOSFET可以降低电磁干扰，减少电磁干扰滤波的成本• 在重量和体积方面减少了50%• 在功率超过5瓦的领域内有较强的低耗能竞争力高达90％的反激拓扑效率• 内置启动和电流限制减少直流损耗• 低电容700 V的MOSFET削减交流损耗• CMOS控制器/栅极驱动器功耗仅为6毫瓦• 70％的最大占空比减少传导损耗简化设计缩短上市时间• 支持多种参考设计板• 将PWM控制器和700 V的MOSFET集成在符合行业标准的3引脚TO-220封装里• 只需一个外部电容用作补偿、分路器和启动/自动重启职能系统级故障保护特点• 自动重启和逐周期电流限制功能能够同时处理初级和次级故障• 片上闭锁热关机功能能够防止系统过载高度通用性• 实现降压、升压、反激或转移拓扑结构• 可轻松地与光电元件和初级反馈进行联接• 支持连续或间断的运作模式描述TOPSwitch系列（仅用三个引脚）实现了离线开关式控制系统所必需的所有功能：带受控导通门驱动器的高压N沟道功率MOSFET ；集成了100KHz振荡器的电压模式PWM控制器；高压启动偏置电路；基准电压参考点；偏置并联稳压器/误差放大器用于环路补偿和故障保护电路。
相比离散的MOSFET和控制器或自振荡（RCC）开关转换器的解决方案，TOPSwitch集成电路可以降低总成本，元件数量，尺寸，重量同时提高了效率和系统的可靠性。
这些设备用于在0到100瓦（普通0到50瓦）范围内提供100/110/230伏离线电源和在0到150瓦范围提供230/277伏离线功率因数校正（PFC）功能。
图1 典型应用图2 功能块图引脚功能描述漏引脚输出MOSFET的漏极连接。
在启动过程中通过一个内置的开关高压电流源提供内部偏置电流，内部电流检测点。
开关电源中英文翻译
Switching Power SupplySwitching power supply is a voltage conversion circuit, the main work is the step-up and step-down, are widely used in modern electronic products. Always work because the switching transistor in the "on" and "off" state, so called switching power supply. Switching power supply in real terms is an oscillator circuit, the conversion of electrical energy not only used in power circuit, the circuit in other applications are also common, such as LCD backlight circuits, such as fluorescent lamps. Switch the source compared with the transformer high efficiency, good stability, small size and other advantages, disadvantages is the relatively small power, and high-frequency interference on the circuit, circuit complexity, such as easy maintenance.Talking about switching power supply before you familiar with the feedback oscillator circuit transformer, can produce a regular pulse current or voltage of the circuit is called oscillation circuit, transformer feedback oscillator circuit is able to meet these conditions the circuit; it in the basic amplifier circuit with a feedback loop composed of C2, L1 election to form a parallel resonant frequency circuit, the instantaneous power in the circuit turn-VT, this time in the C2, L1, composed of parallel resonant circuits have a very rich harmonic, when the plus parallel resonance frequency and the natural frequency of the same circuit, the circuit to enter a state of oscillation, and VT through L3 feedback to further enlarge the base, and ultimately the formation of a regular pulse current or voltage output to the load RL. Switching power supply is around the transformer and the feedback oscillator circuit design, but the basis of the original increase in the number of protection and control circuits, analysis of our oscillation circuit can be used to analyze the method of switching power supply.Switching Power Supply vibration by way of sub-swing can be divided into self-excited and it excited the two, since there is no need for plus-excited self-oscillation signal source, since the excitation can see it as a feedback oscillator circuit transformer, and it is excited is totally dependent on the outside to maintain the oscillation, in the practical application of self-excitation of a comprehensive range of applications. According to the structure of incentives signal classification; can be divided into pulse-width-modulated pulse amplitude modulation and two pulse-width-modulated signal to control the width, that is, frequency, pulse amplitude modulation control signal of the magnitude of the role of the two the same so that oscillation frequency is maintained at within a certain range, to the effect of voltagestability. Winding transformer can be divided into three types in general, a group involved in the primary winding of the oscillation, a group is to maintain the oscillation of the feedback winding, there is a group of the load windings. Household appliances used in switching power supply,after the AC to 220V bridge rectifier, converted into about 300V DC, filter into the transformer is added after the switch to high-frequency oscillations of the collector, feedback winding back to the base to maintain the oscillation circuit, load sensor windings of the electrical signal, by rectification, filtering, the DC voltage regulator has been to provide power to the load. Winding in the provision of electric power load, but also take up the capacity of voltage stability, the theory is then a circuit voltage output voltage sampling devices to monitor the output voltage changes, timely feedback to adjust the oscillation frequency oscillator circuit to achieve the voltage stability The purpose of the circuit in order to avoid interference, the feedback voltage to the oscillator circuit will be isolated optocoupler. Most switches have a standby power circuit, switching power supply in standby mode still oscillating, but the frequency of normal working hours than lower.Some switching power supply are complex, numerous components, many protection and control circuit, in the absence of technical support, maintenance is a headache with the matter. I face this kind of situation is, first of all, I will find the switch and its participation in the external oscillation circuit, it separated from the circuit to see if it met the conditions for oscillation, such as detection bias and whether it is normal, whether positive feedback failure, as well as its own switches, switching power supply has very large protection, after exclusion of the prosecution and load control and protection circuit.the control circuit while output from the sample, with the set standards, then controlled inverter, change its frequency or pulse width output achieve stability, on the other hand, according to test data provided by the circuit by circuit protection identification, Control circuit for the unit for various protection measures.SMPS developments and trends in the United States in 1955 Roje (GH.Roger) invention of the self-excited oscillation push redeem transistor single transformer DC converters, high-frequency conversion is the beginning of control circuit, 1957 United States investigation tournament (Jen Sen) since the invention of the push-pull double Flyback transformers, 1964 American scientists proposes to abolish the frequency transformer series switching power supply scenario, This power to the right size and weight of the decline was a fundamental way. To the 1969 high-power silicon transistor because the pressure increase diode reverse recovery time shortened, andother components improve, and finally turned into a 25 kHz switching power supply.Currently, switching power supply to small, Light volume and the characteristics of high efficiency has been widely used in electronic computer-driven variety of terminal equipment, Communications equipment almost all electronic equipment, the electronic information industry indispensable to the rapid development of a power mode. Currently the market for sale in the switching power supply using bipolar transistors made of 100kHz. use made of 500kHz MOS power, though practical, but its frequency to be further enhanced. To improve the switching frequency, it is necessary to reduce the switching loss, and to reduce the switching loss, you need to have high-speed switching devices. However, the switching speed, will be affected by the circuit inductance and capacitance diode or stored charge arising from the impact of the surge or noise. This will not only affect the surrounding electronic equipment, but also greatly reduce the reliability of the power supply itself. Among them, with the switch to prevent Kai-closed by the voltage surge, it is R-C or L-C Composite bumpers, and the storage charge by the diode current surge caused by the use made of amorphous cores such as magnetic bumper. However, the high frequency of 1 MHz and above, using resonant circuit, Switch to enable the voltage or current through the switch was a sine, which could reduce the switching loss, This can also control the surge occurred. Switches such as resonant mode switching. Currently such SMPS of very active, because this means no significant increase switching speed can theoretically put switching loss fall to zero. and the noise is small, is expected to become high-frequency switching power supply of one of the main ways. At present, many countries in the world are working on several trillion Hz converter practical research.开关电源开关电源是一种电压转换电路，主要的工作内容是升压和降压，广泛应用于现代电子产品。
开关电源专业电子中英文词汇
开关电源专业电子中英文词汇Absorber Circuit 吸收电路AC/AC Frequency Converter 交交变频电路AC power control交流电力控制AC Power Controller交流调功电路AC Power Electronic Switch交流电力电子开关Ac Voltage Controller交流调压电路Asynchronous Modulation异步调制Baker Clamping Circuit 贝克箝位电路Bi-directional Triode Thyristor双向晶闸管Bipolar Junction Transistor-- BJT双极结型晶体管Boost-Buck Chopper 升降压斩波电路Boost Chopper 升压斩波电路Boost Converter 升压变换器Bridge Reversible Chopper 桥式可逆斩波电路Buck Chopper 降压斩波电路Buck Converter 降压变换器Commutation 换流Conduction Angle 导通角Constant Voltage Constant Frequency --CVCF 恒压恒频Continuous Conduction—CCM （电流）连续模式Control Circuit 控制电路Cuk Circuit CUK 斩波电路Current Reversible Chopper 电流可逆斩波电路Current Source Type Inverter--CSTI 电流（源）型逆变电路Cycloconvertor 周波变流器DC-AC-DC Converter直交直电路DC Chopping 直流斩波DC Chopping Circuit 直流斩波电路DC-DC Converter 直流－直流变换器Device Commutation 器件换流Direct Current Control 直接电流控制Discontinuous Conduction mode （电流）断续模式displacement factor 位移因数distortion power 畸变功率double end converter 双端电路driving circuit 驱动电路electrical isolation 电气隔离fast acting fuse 快速熔断器fast recovery diode 快恢复二极管fast revcovery epitaxial diodes快恢复外延二极管fast switching thyristor 快速晶闸管field controlled thyristor 场控晶闸管flyback converter 反激电流forced commutation 强迫换流forward converter 正激电路frequency converter 变频器full bridge converter 全桥电路full bridge rectifier 全桥整流电路full wave rectifier 全波整流电路fundamental factor 基波因数gate turn-off thyristor——GTO可关断晶闸管general purpose diode普通二极管giant transistor——GTR电力晶体管half bridge converter 半桥电路hard switching 硬开关high voltage IC 高压集成电路hysteresis comparison 带环比较方式indirect current control 间接电流控制indirect DC-DC converter 直接电流变换电路insulated-gate bipolar transistor-----IGBT绝缘栅双极晶体管intelligent power module-------IPM智能功率模块integrated gate-commutated thyristor------IGCT集成门极换流晶闸管inversion 逆变latching effect 擎住效应leakage inductance 漏感light triggered thyristo---LTT光控晶闸管line commutation 电网换流load commutation 负载换流loop current 环流Schottky Barrier Diode 肖特基二极管。
5开关电源英文
Switching-Mode Power Supply Design 开关模式电源设计What is a switching-mode power supply什么是开关模式电源A power supply is a buffer circuit that provides power with the characteristics required by the load 电源是一种缓冲电路提供电量特性被负载需要from a primary power source with characteristics incompatible with load. it makes the load 主电源特性不兼容的负载compatible with power source.Example :A power supply si sometimes called a power converter and the process is called power conversion. It is also sometimes caller a power conditioner and the process is called power conditioning. The power manufacturers association is handbook of standardized terminology for the power source industry gives this definition of a power supply.Power supply-A device for the conversion of available power of characteristics to another set of characteristics to meet specified requirements. Typical application of power supplies include to convert raw input power to a controller or stabilized voltage and current for the operation of electronic equipment.Power supplies belong to the field of power electronics, the use of electronics for the control and conversion of electrical power. The ieee power electronics society provides a more formal definition of power electronics in their constitution.Power Electronics-This technology encompssses the dffdctive use of electronic components, the application of circuit theory and design techniques, and the development of analytical tool toward efficient electronic conversion, control, and conditioning of electric power.A switching-mode power supply is a power supply that provides the power function through low loss components such as capacitors, inductors, and transformers –and the use of switches that are of two states , on or off. The advantage is that the switch dissipates very little power in either of these two states and power conversion can be accomplished with minimal power loss, which equates to high efficiency. The term switch-mode was widely used for this type of power supply until Motorola, inc, who used the trademark SWITCHMODE TM for products aimed at the switching-mode power supply market, started to enforce their trademark. Others used the term switching power supply, which seems to be the more popular term. PSMA does not define either switching-mode power supply or switching power supply, which seems to be the more popular term. PSMA dose not define either switching-mode power supply or switching power supply, bu does define switching regulator.Off line power supply---1 A power supply in which the ac line voltage is rectified and filtered and filtered without using a line frequency isolation transformer. 2 A power supply switched into service upon line loss to provide power to the load without significant interruption. Also called off line switching.Switching regulator-A switching circuit that operates in a closed loop system to regulate the power supply output.Power factor correction—1 technique of increasing the power factor so that the phase angle between the voltage and current approaches zero in an accircuit. 2 addition of capacitors to an inductive circruit that operates in a closed loop system to regulate the power supply output.Power factor correction---1 technique of increasing the power factor so that the phase angle between the voltage and current approaches zero in an accircuit. 2 Addition of capacitors to an inductive circuit to offset reactance.The purpose of this tutorial, power factor is real power controlled by apparent power and power factor rrection is making this ratio approach one.The full bridge converter converterFull bridge converters operate in a similar fashion to half bridge converters, but as shown in the diagram below, instead of single switches being switches being switched in turn, a pair of switches is used. This enables the full DC input voltage of Vd to be applied to the transformer is primary winding sequentially positive and negative. By applying Vd instead of Vd, better use is made of the transformer core. Higher switching frequencies can be used, while still applying rated flux to the core.Since double the voltage is applied to the transformer core when compared with a half bridge, the turns ratio for a particular input-output voltage pair can be halved. Therefore, Although the switches in both converters need to block the full supply voltage. Only half the current is required to be carried by the switches in the full bridge. This results in much lower stress levels on the switching components and allows lower rated switches to be used. Lower rated switches usually have reduced internal losses and therefore by their use, losses in the switches can be reduced.To improve output power capabilities further, a full bridge diode rectifier was used on the secondary of the high frequency transformer. As the audio amplifier application calls for both positive and negative rails having their own inductances. A capacitive filter is used as the final stage of the first-order output filter.Available switching devicesA number of options were available for the converter circuits. The switches are required to handle the voltage levels of a rectified mains supply and its inherent fluctuations. In addition, the switches must be capable of conducting the high peak currents required and yet be able to be accurately switched on and off at the required frequency of 200KHz. Only a few years ago this decision would have been limited, with the switches being required to block up to 400V and carry a relatively significant current. The high switching frequency also causes problems with switch driving which would have made the converter even more difficult to implement. The advancement in semiconductor technology has brought with it an increased choice in switching devices.The switches required must be able to be turned on and off by a switching signal these are termed controllable switches. Thyristors can be fired to turn on at a particular instant, but only switch off once current through them drops to zero. This characteristic is useful in some forms of resonant switching such as zero current switching. Here it is desired for switching to occur at a level when the current is negligible in order to reduce losses, but for this application being able to control switch off precisely is important. For instance, if we are to avoid both switches in a leg of a bridge converter being closed during the same interval we need to be able to ensure one switch is opened before the other is closed. This is most easily accomplished using a controllable switch.The ideal controllable switch would hace the following characteristics:1. Block arbitrarily large forward/reverse voltages with no current flow when off.2. Conduct arbitrarily large currents with no voltage drop when on.3. Switch from one state to another instantanously when triggered.4. Require minimal power from the control source to trigger the switch.Of course these ideal properties are not attainable but an appropriate switch must be chosen toachieve as close as possible to these ideal characteristics.The physical properties of real switching devices govern their suitability to a particular application. A switch must be able to block the required voltage level when open. This blocking level is determined by the construction of the device itself. When closed, a switch has a certain level of resistance across its terminals – this results in power dissipation due to I2R losses. One of the major areas of losses in switched mode supplies is due to the finite time it takes for a switch to close or open. The power dissipated during switch on/off can be a limiting factor of a Switched Mode Power Supply. These losses are constant for each transition and hence are proportional to switching frequency.Bipolar Junction Transistors are controlled by a current signal. Power BJTs have been optimized to handle the higher power levels and hence, typically have fairly low values for the DC current gain Hfe. This means that if it is desired to drive a transistor to allow a collector current of 20A to flow, the base of the transistor may need to be supplied with a continuous current of up to 4A for the entire time the transistor is on. Some heavy power electronic is required just for base drive and the associated losses are high, due the large currents involved. BJTs also take a significant time at turn off to sweep electrons out of the base area and to stop current flowing. This time can become significant due to the implied frequency limitations and also results in losses associated with the extended time to turn off. Another problem with BJTs is the fact that they have a negative temperature coefficient. This can lead to thermal runaway, where the temperature of the device increases and hence the resistance across the device drops allowing more current to flow, heating the BJT further…MOSFETs however are voltage-controlled devices. Their gates appear as capacitances, which must be charged for ON state and discharged for OFF. This implies that current need only flow during the short time it takes to charge/discharge the small gate capacitor. This leads to very short switching times, making MOSFETs highly suitable for high frequency applications. Due to their construction, a MOSFETs ON resistance increases rapidly with the device is blocking rating, but the speed with which MOSSFETs are capable of switching, often offsets these losses. MOSFETs also have a positive temperature coefficient.GTOs have a number of favourable properties, but their slow switching speed means that they are not suitable for this SMPS application.IGBTs offer the best characteristics of MOSFERs, BJTs, and GTOs. The IGBT has an easily driven, high impedance gate like a MOSFET, a small ON state voltage drop like a BJT and can be designed to block negative voltages like a GTO. They have fast turn on/off transitions and can have very high power ratings.IGBTs present as the most logical choice for the final high power product, but the required switching speed is too fast for all but the very latest IGBTs. For simplicity and due to the wide selection available, MOSFETs were chosen as the switches for the product. MOSFETs are not only easily available. But due to their popularity, a wide range of driver integrated circuits has been developed, optimized for their switching needs. Also, hardware for a half bridge converter using MOSFETs was available for testing purposes.Drive of switching elements---- isolationIn order to satisfy the requirements of input to output voltage isolation, there must be no electrical connection between input and output. On the power level, in a bridge converter, the high frequency transformer provides isolation. On a control and drive level, we need to provide switching signals for the MOSFETs on the primary side, while monitoring the output voltage. Therefore some additional isolation is required.If the controller is to be placed on the primary side with the switches, isolation needs to be provided for the feedback signal. If the controller is placed on the secondary side, then electrical isolation must be provided in the path to the switches MOSFETs are swetched by providing a voltage differential between gate and source in order to charge their gate. In a half bridge converter, the upper MOSFET is source is sitting at a different potential to that of the lower device-this implies that the upper MOSFET needs to be floated.The floating or isolation of the upper switch can be achieved in a number of ways. A specially designed MOSFET bridge driver could be used. this device accepts TTL control signals from some form of controller and converts them directly into dual higher voltage MOSFET drive signals the upper switch, some forms of these bridge drivers also contain appropriate logic to ensure that potentially destructive switch combinations are avoided. Some of these devices actually convert their drive power directly from the higher supply rails, eliminating the requirement of a lower voltage supply specifically for switch drive.Another method is to use a small pulse transformer. A pulse transformer not only allows signals to be transmitted across an isolation boundary, but also allows power to travel across the boundary. This is the solution that was deemed most suitable for this application. Through the use of a single pulse transformer with dual secondary windings, both transistors could be driven in the required complementary fashion by simply connecting the transformer secondaries to the MOSFETs in opposite polarities. This method allowed both switches to be driven from a single control signal and also allowed for all switch control to be situated on the secondary of the transformer. The necessary isolation would be provided, while avoiding corrupting the feedback signal to the controller with isolation devices. Had a bridge driver IC been used, isolation would still have had to be provided. This could have been achieved through the use of optocouplers or the transformers referred to earlier. The chosen method of isolation eliminates the need for need for primary side drive circuitry.Drive of Switching Elements-MOSFET Drive RequirementsIn a switched mode power supply, losses are minimized by avoiding the dissipative active region of the semiconductor switches used. This active region lies between the two states that we use, hence it is desirable ensure the switch spends as little time as possible in this region.MOSFETs, as with other semiconductor switches, have a finite switching time. This time to change states is a hardware limitation and arises from the construction of the device. Through careful selection of switching device, we can choose a switch with transitional times as short as possible. For example, the MOFETs used in the in existing hardware have switching times of around 25ns.In order to take advantage of the possible rapid turn on/off times of which MSFETs are capable, we need to charge and discharge their input gate capacitances as rapidly as possible. Toperform this function, very rapid changes in voltage are required. The gate capacitance of the IRF740 is typically around 1nF. If we want to charge this gate in 25nS to a voltage of the 10V, a peak current of almost half an amp is required for each transition. Some sort of dedicated drive circuitry is required in order to charge these gates with sufficient speed if the control circuitry outputs a TTL signal.These are a number of commercially available devices specifically designed to meet the needs of MOSFETs drive. Some, like the afore-mentioned bridge drivers take care of the drive requirements in addition to the floating of the upper MOSFET. Others, designed as generic MOSFET drivers, simply act as a high current buffer between signal and arrive voltage levels. The ICL7667 is such a device and was used for initial testing purposes. It is simply an inverting buffer with two TTL inputs and dual MOSFET drive outputs. It was used in conjunction with the pulse transformer mentioned earlier to provide appropriate MOSFET drive from TTL control signals. Selecting a controller with in-built drive circuitry eliminated the need for a stand-alone MOSFET driver in the final design.Converter Control---Using the SwitchesPhysical switching of devices has been covered, but a method of switch utilization to change input to output voltage levels is now required.By varying the time each switch is on, compared with the time it is off, the average voltage of this square pulse train can be varied. For example, if a switch is on for only a short time, but is off for a longer time, the average voltage after the switch will be lower than for the situation where on and off times are equal. This is known as varying the duty cycle of the switches. The average voltage is recovered by passing the signal through an integrating filter.Duty cycle is defined as the percentage of the total switching cycle that a switch is on. By varying the duty cycle of the switches in our half bridge converter. We can vary the average value of the energy transferred across the transformer. The transformer is designed so that its turns ratio gives the majority of the voltage conversion and the duty cycle variation can be used for finer adjustments.By varying the duty cycle appropriately in response to a change in input voltage or output current requirements, we can maintain the output voltage, for a wide variety of input/output situations. This is known as regulation by PWM.Converter Control----Pulse Width ModulationThere are a number of different methods for implementing Pulse Width Modulation. These can be divided into two major sections: whose where switching frequency is kept constant and those where it is varied. In variable frequency PWM, there are a number of different ways to vary the average output voltage.Variable frequency PWM poses a serious problem in output filter design – it is difficult to design a filter if the desired frequency response is unknown. For this reason I will be focusing on the fixed on the fixed frequency form of PWM.In fixed frequency PWM, the total time for a cycle is kept constant. Duty cycle is varied by changing both the time on and time off for a switch..Such that: Ts=Ton+ToffComparing an amplified error signal with some repetitive waveform generates the fixed frequency PWM control signal to the switches.Comparing the output voltage of the converter with some precise reference corresponding tothe desired output value generates the error signal Vc. It can be seen from the figure 7, that when the repetitive waveform is greater than the error signal, the switchs are turned on and when the error signal id of a lower value than the sawtooth, the switches are turned off. When a pair of switches is involved, as in a bridge converter, they are switched alternately. Each switch must have a duty cycle of less than 50% in order to avoid the destructive shoot-through condition.This fixed frequency PWM can be performed by a number of means : an analogue circuit built up of individual components, an analogue PWM IC, or ever increasingly, by digital means.The following figures show a block diagram and the switching waveforms of a PWM IC, but the majority of controllers operate in a similar manner.The High Frequency TransformerThe high frequency transformer provides the input to output isolation in the power stage of the converter. As with their low frequency counterparts, high frequency transformers provide a reliable and efficient form of converting one voltage level to another. It is for this reason that a transformer is turns ratio is favoured over PWM to produce the major changes in voltage level often required in converters. In order to minimize switching stresses, the high frequency transformer of a bridge-type SMPS is designed to operate at just under a 50% duty cycle on the switches. This allows for fluctuations in load and supply to be dealt with by decreasing or increasing the switch duty cycleOperation at high frequencies exemplifies many of the shortfalls of line frequency transformers. Just as low frequency transformer cores need to be laminated to reduce losses, high frequency cores need to be made of special materials.Although an essential component in many switching converters, the broad range of tasks set down for high frequency transformers to perform means that there cannot be an off the shelf ferrite transformer that will perform as desired. In the vast majority of cases, transformers must be custom built for each application.There are available, from companies such as Philips, high frequency transformer kits, consisting of coil formers and cores in a wide variety of styles and ferrite materials to suit most applications. These kits allow the engineer to design a transformer to suit their needs using well-documented components and standard materials with known properties. These are a number of standard ferrite materials available to the designer in different shapes and sizes. The different materials are suited to different operating frequency ranges.At higher frequencies, losses in the magnetic material become more significant. There are two major classes of core materials used for magnetic components: those comprising primarily iron and small amounts of other elements. Ferrite materials have a significantly higher electrical resistivity than their iron derivative counterparts and hence exhibit no significant eddy current characteristics-ferrite materials have only hysteresis loss, but their saturation flux densities are quite low. These properties mean that they are the material of choice for high frequency applications. Care must be taken, however to avoid saturation of the transformer. This can have catastrophic effects and can quickly occur if there is a volt-second imbalance between positive and negative excitations on the transformer primary.A wide variety of different materials with different properties exist in the ferrite materials, and a material must be carefully chosen appropriate to the operational frequency of the application.The copper windings also require more careful design than for their low frequency cousins. As operating frequencies become elevated, the skin effect in the windings becomes increasingly significant, shifting the distribution of current in a conductor to only close to the surface. This reduces the effective conductor cross section, which results in the conductor having an AC resistance significantly higher than its usually-quoted DC resistance.In order to avoid problems associated with this effect, a number of interesting winding techniques have been developed whereby wires with diameters not exceeding a skin depth at the operating frequency are used. Litz wire is designed to minimize skin effect problems while changing traditional wire winding techniques as little as possible. This is achieved by replacing a wire of a single core with multiple fine cores, woven into a single thin cable. Copper foil is another good way of eliminating these parasitic problems. The traditional copper wire is replaced effectively by a conductor of rectangular cross section the depth of which not exceeding a skin depth.A relative to the copper foil method is the exciting new field of planer cores. Planer cores are narrow ferrite cores, which sandwich a printed circuit board, on which the windings are etched. Windings can be etched across multiple layers of a single board, or multiple thin boards can be stacked together make up a complete set of windings. Not only does this make the transformer more compact, but winding errors can be completely eliminated from a production run, and most importantly, flux linkages between the windings are excellent. I believe that a planer core, if designed correctly would be the ideal solution for future projects on my application.。
史上最全的开关电源专业英语词汇
史上最全的开关电源专业英语词汇史上最全的开关电源专业英语词汇母线:Busbar输电线:TransmissionLine发电厂:power plant断路器:Breaker刀闸(隔离开关):Isolator分接头:tap电动机:motor状态参数有功:active power无功:reactive power电流:current容量:capacity电压:voltage档位:tap position有功损耗:reactive loss无功损耗:active loss功率因数:power-factor功率:power功角:power-angle电压等级:voltage grade空载损耗:no-load loss铁损:iron loss铜损:copper loss空载电流:no-load current阻抗:impedance正序阻抗:positive sequence impedance负序阻抗:negative sequence impedance零序阻抗:zero sequence impedance电阻:resistor电抗:reactance电导:conductance电纳:susceptance无功负载:reactive load 或者QLoad有功负载: active load PLoad遥测:YC(telemetering)遥信:YX励磁电流(转子电流):magnetizing current定子:stator功角:power-angle上限:upper limit下限:lower limit并列的:apposable高压: high voltage低压:low voltage中压:middle voltage电力系统 power system发电机 generator励磁 excitation励磁器 excitor电压 voltage电流 current母线 bus变压器 transformer升压变压器 step-up transformer高压侧 high side输电系统 power transmission system输电线 transmission line固定串联电容补偿fixed series capacitor compensation稳定 stability电压稳定 voltage stability功角稳定 angle stability暂态稳定 transient stability电厂 power plant能量输送 power transfer交流 AC装机容量 installed capacity电网 power system落点 drop point开关站 switch station双回同杆并架double-circuit lines on the same tower变电站 transformer substation补偿度 degree of compensation高抗 high voltage shunt reactor无功补偿reactive power compensation故障 fault调节 regulation裕度 magin三相故障 three phase fault故障切除时间 fault clearing time极限切除时间 critical clearing time切机 generator triping高顶值 high limited value强行励磁 reinforced excitation线路补偿器LDC(line drop compensation)机端 generator terminal静态 static (state)动态 dynamic (state)单机无穷大系统 one machine - infinity bus system机端电压控制 AVR电抗 reactance电阻 resistance功角 power angle有功(功率) active power无功(功率) reactive power功率因数 power factor无功电流 reactive current下降特性 droop characteristics斜率 slope额定 rating变比 ratio参考值 reference value电压互感器 PT分接头 tap下降率 droop rate仿真分析 simulation analysis传递函数 transfer function框图 block diagram受端 receive-side裕度 margin同步 synchronization失去同步 loss of synchronization 阻尼 damping摇摆 swing保护断路器 circuit breaker电阻:resistance电抗:reactance阻抗:impedance电导:conductance电纳:susceptance导纳:admittance电感:inductance电容: capacitance电源英语词汇(三)coupling 耦合intermittent 周期的dislocation 错位propeller 螺旋桨switchgear 配电装置dispersion 差量flange 法兰盘dielectric 介电的binder 胶合剂alignment 定位elastomer 合成橡胶corollary 必然的结果rabbet 插槽vent 通风孔subtle 敏感的gearbox 变速箱plate 电镀crucial 决定性的flexible 柔性的technics 工艺ultimate 最终的resilience 弹性vendor 自动售货机partition 分类rigid 刚性的prototype 样机diagram 特性曲线interfere 干涉compatible 兼容的simulation 模拟clutch 离合器refinement 精加工fixture 夹具torque 扭矩responsive 敏感的tensile 拉伸cushion 减震器rib 肋strength 强度packing 包装metallized 金属化stress 应力mitigate 减轻trade off 折衷方案yield 屈伸line shaft 中间轴matrix 母体inherent 固有的spindle 主轴aperture 孔径conformance 适应性axle 心轴turbulence 扰动specification 规范semipermanent 半永久性的enclosure 机壳specialization 规范化bolt 螺栓oscillation 振幅calling 职业nut 螺母anneal 退火vitalize 激发screw 螺丝polymer 聚合体revelation 揭示fastner 紧固件bind 凝固dissemination 分发rivit 铆钉mount 支架booster 推进器hub 轴套distortion 变形contractual 契约的coaxial 同心的module 模块verdict 裁决crank 曲柄slide 滑块malfunction 故障inertia 惰性medium 介质allegedly 假定active 活性的dissipation 损耗controversy 辩论lubrication 润滑assembly 总装dictate 支配graphite 石墨encapsulate 封装incumbent 义不容辞的derivative 派生物adhesive 粘合剂validation 使生效contaminate 沾染turbine 涡轮procurement 收购asperity 粗糙bearing 支撑架mortality 失败率metalworking 金属加工isostatic 均衡的shed light on 阐明viscous 粘稠的osculate 接触adversely 有害的grinding 研磨imperative 强制的consistency 连续性corrosin 侵蚀lattice 晶格fitness 适应性flush 冲洗fracture 断裂warrant 保证inhibitor 防腐剂diffusivity 扩散率turning 车工dispersant 分散剂vice versa 反之亦然ways 导轨deteriorate 降低tribological 摩擦的hybrid 混合物neutralize 平衡screen 屏蔽ID=inside diameterpulley 滑轮exclusion 隔绝OD=outside diameter hydraulic 液压的insulation 绝缘reciprocate 往复运动delicate 精密的elaborate 加工dress 精整dampen 阻尼incontrovertible 无可争议的by and large 大体上pivotal 中枢的luminous 发光的plastic 塑胶utilitarian 功利主义out of round 失园organic 有机的grass root 基层premature 过早的film 薄膜state-of-the -art 技术发展水平guard 防护罩polyester 聚酯blade 托板permeate 渗入epoxy 环氧的carrier 载体spillage 溢出polypropylene 聚丙烯chuck 卡盘erosion 浸蚀photoconductive 光敏的infeed 横向进给routine 程序miniaturization 小型化lapping 抛光postprocess 后置处理asynchronism 异步milling 洗削solder-bump 焊点synchronization 同步speciality 专业grid 栅格respond 响应stroke 行程impedance 阻抗feedback 反馈attachment 备件approximately 大约aberrance 畸变tapered 楔形的purported 据说steady 稳态的casting 铸件consumable 消费品dynamic 动态的index 换档inductance 电感transient 瞬态的stop 挡块capacitance 电容coordinate 坐标contour 轮廓resistance 电容curve 曲线machine center 加工中心audion 三极管diagram 特性曲线capitalize 投资diode 二极管history 关系曲线potentiometer 电位器transistor 晶体管gradient 斜率know-how 实践知识choker 扼流圈parabola 抛物线potted 封装的filter 滤波器root 根mechatronics 机电一体化transformer 变压器eigenvalue 特征值stem from 起源于fuse 保险丝function 函数rule-based 基于规则的annular core 磁环vector 向量consolidation 巩固radiator 散热器reciprocal 倒数energize 激发regulator 稳压器virtual value 有效值synchronous 同时发生bobbin 骨架square root 平方根socket 插孔tape 胶带cube 立方polarity 极性ceramic capacitor 瓷片电容integral 积分armature 电枢electrolytic C 电解电容differential 微分installment 分期付款self-tapping screw 自攻螺丝hisgram 直方图lobe 凸起footprint 封装ratio 比率plunge 钻入resin 松香grade down 成比例降低servo 伺服机构solderability 可焊性proportion 比例dedicated 专用的shock 机械冲击inverse ratio 反比interpolation 插补endurance 耐久性direct ratio 正比compensation 校正initial value 初始值plus 加upload 加载flashing 飞弧subtract 减overload 过载canned 千篇一律的multiply 乘lightload 轻载lot 抽签divide 除stagger 交错排列parallel 并联impedance 阻抗traverse 横向in series 串联damp 阻尼longitudinal 纵向的equivalent 等效的reactance 电抗latitudinal 横向的terminal 终端admittance 导纳restrain 约束creep 蠕动susceptance 电纳square 平方Hyperlink 超级连接spring 触发memo 备忘录wastage 损耗presentation 陈述principle 原理binder 打包planer 刨床source program 源程序Client-Server Model客户机server 服务器table 表query 查询form 表单report 报表macro 宏module 模块field 字段record 记录。
最新开关电源设计及其英文翻译
开关电源设计及其英文翻译Switching Power Supply DesignSwitching power supply work in high frequency, high pulse state, are analog circuits in a rather special kind. Cloth boards to follow the principle of high-frequency circuit wiring.1, layout:Pulse voltage connection as short as possible, including input switch connected to the transformer, output transformer to the rectifier tube cable. Pulse current loop as small as possible such as the input filter capacitor is returned to the transformer to the switch capacitor negative. Some out-ended output transformers are the output rectifier to the output capacitor back to transformer circuit X capacitor as close as possible to the input switching power supply, input lines should be avoided in parallel with other circuits, should be avoided. Y capacitor should be placed in the chassis ground terminal or FG connectors.A total of touch induction and transformer to maintain a certain distance in order to avoid magnetic coupling. Such as poor handling of feeling in between inductor and transformer plus a shield, over a number of EMC performance for power supply to the greater impact. General the output capacitor can be used the other two a close rectifier output terminal should be close to, can affect the power supply output ripple index, two small capacitor in parallel results should be better than using a large capacitor. Heating devices to maintain a certain distance, and electrolytic capacitors to extend machine life, electrolytic capacitors is the switching power supply bottleneck life, such as transformers, power control, high power resistors and electrolytic to maintain the distance required between the electrolyte leaving space for heat dissipation , conditions permitting, may be placed in the inlet.Control part to pay attention to: Weak signal high impedance circuit connected to sample the feedback loop as short as in the processing as far as possible avoid interference, the current sampling signal circuits, in particular the current control circuit, easy to deal with some unexpected bad The accident, which had some skill, now to 3843 the circuit example shown in Figure (1) Figure 1 better than Yu Figure 2, Figure 2 Zai full time by observing the current waveform oscilloscope Mingxian superimposed spikes, Youyuganrao limited flow ratio design Zhi Dian low, Figure 1 there is no such phenomenon, there are switch drive signal circuit, switch resistance should be close to the switch driver can switch the work to improve the reliability of this and the high DC impedance voltage power MOSFET driver characteristics.Second, routingAlignment of current density: now the majority of electronic circuit board using insulated copper constitute tied. Common PCB copper thickness of 35μm, the alignmentvalue can be obtained in accordance with 1A/mm experience the value of current density, the specific calculations can be found in textbooks. To ensure the alignment principles of mechanical strength should be greater than or equal to the width of 0.3mm (other non-power supply circuit board may be smaller minimum line width). PCB copper thickness of 70μm is also common in switching power supply, then the current density can be higher. Add that, now Changyong circuit board design tool design software generally items such as line width, line spacing, hole size and so dry plate Guo Jin Xing parameters can be set. In the design of circuit boards, design software automatically in accordance with the specifications, can save time, reduce some of the workload and reduce the error rate.Generally higher on the reliability of lines or line density wiring can be used double panel. Characterized by moderate cost, high reliability, to meet most applications.The ranks of some of the power module products are also used plywood, mainly to facilitate integration of power devices such as transformer inductance to optimize wiring, cooling and other power tube. Good consistency with the craft beautiful, transformer cooling good advantage, but its disadvantage is high cost, poor flexibility, only suitable for industrial mass production.Single-sided, the market circulation of almost universal switching power supply using single-sided circuit board, which has the advantage of lower costs in the design and production technology are also taken some measures to ensure its performance.Single PCB design today to talk about some experience, as a single panel with low cost, easy-to-manufacture features, the switching power supply circuit has been widely used, because of its side tied only copper, the device's electrical connections, mechanical fixation should rely on the copper layer, the processing must be careful.To ensure good performance of the mechanical structure welding, single-sided pad should be slightly larger to ensure that the copper and substrate tied good focus, and thus will not be shocked when the copper strip, broken off. General welding ring width should be greater than 0.3mm. Pad diameter should be slightly larger than the diameter of the device pins, but not too large, to ensure pin and pad by the solder connection between the shortest distance, plate hole size should not hinder the normal conditions for the degree of investigation, the pad diameter is generally greater than pin diameter 0.1-0.2mm. Multi-pin device to ensure a smooth investigation documents can also be larger.Electrical connection should be as wide as possible, in principle, should be larger than the width of pad diameter, special circumstances should be connected in line with the need to widen the intersection pad (commonly known as Generation tears), to avoid breaking certain conditions, line and pad. Principle of minimum line width should be greater than 0.5mm.Single-board components to be close to the circuit board. Need overhead cooling device to device and circuit board between the pins plus casing, can play a supporting device and increase the dual role of insulation to minimize or avoid external shocks on the pad and the pin junction impact and enhance the firmness of welding. Circuit board supporting the weight of large parts can increase the connection point, can enhance joint strength between the circuit board, such as transformers, power device heat sink.Single-sided welding pins without affecting the surface and the shell spacing of the prior conditions, it can be to stay longer, the advantage of increased strength of welded parts, increase weld area and immediately found a Weld phenomenon. Shear pin long legs, the welding force smaller parts. In Taiwan, the Japanese often use the device pins in the welding area and the circuit board was bent 45 degrees, and then welding process, its reasoning Ibid. Double panel today to talk about the design of some of the issues, in relatively high number of requests, or take the line density of the larger application environments using double-sided PCB, its performance and various indicators of a lot better than a single panel.Two-panel pad as holes have been high intensity metal processing, welding ring smaller than a single panel, the pad hole diameter slightly larger in diameter than pins, as in the welding process solder solution conducive to penetrate through the top hole solder pad to increase the welding reliability. But there is a disadvantage if the hole is too large, wave soldering tin when the jet impact in the lower part of the device may go up, have some flaws.High current handling of alignment, line width in accordance with pre-quote processing, such as the width is not enough to go online in general can be used to increase the thickness of tin plating solution, the method has a good variety of1. Will take the line set to pad property, so that when the circuit board manufacturing solder alignment will not be covered, the whole hot air normally be tin plated.2. In the wiring by placing pads, the pad is set to take in line shape, pay attention to the pad holes set to zero.3. In the solder layer placed on line, this method is the most flexible, but not all PCB manufacturers will understand your intentions, needed captions. Place the line in the solder layer of the site will not coated solder tinning line several methods as above, to note that, if the alignment of a very wide all plated with tin in solder after the solder will bond a lot and distribution is very uneven, affecting appearance. Article tin can be used generally slender width in the 1 ~ 1.5mm, length can be determined according to lines, tin part of the interval 0.5 ~ 1mmDouble-sided circuit board for the layout, the alignment provides a very selective, make wiring more reasonable. On the ground, the power ground and signal ground must be separated, the two to converge in filter capacitors, in order to avoid a large pulsed current through the signal ground connection instability caused by unexpected factors, the signal control circuit grounding point as far as possible, a skill, as far as possible the alignment of the non-grounded wiring layer in the same place, the last shop in another layer of earth. Output line through the filter capacitors, the general first, and then to the load, input line must also pass capacitor, to the transformer, the theoretical basis is to ripple through trip filter capacitor.Voltage feedback sampling, in order to avoid high current through the alignment of the feedback voltage on the sampling point must be the most peripheral power output to increase the load effect of target machine.Alignment change from a wiring layer to another wiring layer generally used hole connected, not through the pin pad device to achieve, because the plug in the device may be damaged when the relationship between this connection, there is current in every passage of 1A, at least two through-hole, through hole diameter is greater than the principle of 0.5mm, 0.8mm generally processed ensure reliability.Cooling devices, in some small power supply, the circuit board traces can be and cooling, characterized by the alignment as generous as possible to increase the cooling area is not coated solder, conditions can even be placed over holes, enhanced thermal conductivity .Today to talk about the aluminum plate in the switching power supply application and multilayer printed circuit in the switching power supply applications.Aluminum plate by its own structure, has the following characteristics: very good thermal conductivity, single Mianfu copper, the device can only be placed in tied copper surface, can not open electrical connection hole so as not to place jumper in accordance with a single panel.Aluminum plate is generally placed patch device, switch, the output rectifier heat conduction through the substrate to go out, very low thermal resistance, high reliability can be achieved. Transformer with planar chip structure, but also through substrate cooling, the temperature is lower than the conventional, the same size transformer with a large aluminum plate structure available output power. Aluminum plate jumper bridge approach can be used. Aluminum plate power are generally composed by the two PCB, another one to place the control circuit board, through the physical connection between the two boards is integrated.As the excellent thermal conductivity of aluminum plate, in a small amount of manual welding more difficult, solder cooling too fast and prone to problems of a simpleand practical way of existing, an ironing ordinary iron (preferably temperature regulation function), over and iron for the last, fixed, and temperature to 150 ℃ and above the aluminum plate on the iron, heating time, and then affix the components according to conventional methods and welding, soldering iron temperature is appropriate to the device easy to , is too high when the device may be damaged, or even copper strip aluminum plate, the temperature is too low welding effect is not good, to be flexible.Recent years, with the multi-layer circuit board applications in switching power supply circuit, printed circuit transformer makes it possible, due to multilayer, smaller spacing also can take advantage of Bianya Qi window section, the main circuit board can be re- Add 1-2 formed by the multilayer printed coil to use the window, the purpose of reducing circuit current density, due to adopt printed coil, reducing manual intervention, transformers consistency, surface structure, low leakage inductance, coupling good . Open-type magnetic core, good heat dissipation. Because of its many advantages, is conducive to mass production, it is widely used. But the research and development of large initial investment, not suitable for small-scale health.Switching power supply is divided into, two forms of isolation and non-isolated, isolated here mainly to talk about switching power supply topologies form below, non-specified, are to isolate the power. Isolated power supply in accordance with the structure of different forms, can be divided into two categories: a forward and flyback. Flyback transformer primary side means that when the Vice-edge conduction cut-off, transformer storage. Close of the primary, secondary side conduction, the energy released to the load of work status, general conventional flyback power multiplex, twin-tube is not common. Forward refers to the primary conduction in transformer secondary side while the corresponding output voltage is induced into the load, the direct transfer of energy through the transformer. According to specifications can be divided into conventional forward, including the single-transistor forward, Double Forward. Half-bridge, bridge circuits are all forward circuit.Forward and flyback circuits have their own characteristics in the process of circuit design to achieve optimal cost-effective, can be applied flexibly. Usually in the low-power flyback can be adopted. Slightly larger forward circuit can use a single tube, medium-power can use Double Forward circuit or half-bridge circuit, low-voltage push-pull circuit, and the half-bridge work in the same state. High power output, generally used bridge circuit, low voltage can be applied push-pull circuit.Flyback power supply because of its simple structure, and to cut the size of a similar size and transformer inductance, the power supply in the medium has been widely applied. Presentation referred to in some flyback power supply can do dozens of watts, output power exceeding 100 watts would be no advantage to them difficult. Under normalcircumstances, I think so, but it can not be generalized, PI's TOP chips can do 300 watts, an article describes the flyback power supply can be on the KW, but not seen in kind. Power output and the output voltage level.Flyback power transformer leakage inductance is a critical parameter, because the power needs of the flyback transformer stored energy, to make full use of transformer core, the general must be open in the magnetic circuit air gap, the aim is to change the core hysteresis back line of the slope, so that transformers can withstand the impact of a large pulse current, which is not core into saturation non-linear state, the magnetic circuit in the high reluctance air gap in the state, generated in the magnetic flux leakage is much larger than completely closed magnetic circuit .Transformer coupling between the first pole is the key factor determining the leakage inductance, the coil to be very close as far as possible the first time, the sandwich can be used around the law, but this would increase the distributed capacitance transformer. Use core as core with a long window, can reduce the leakage inductance, such as the use of EE, EF, EER, PQ-based EI type magnetic core effective than good.The duty cycle of flyback power supplies, in principle, the maximum duty cycle of flyback power supply should be less than 0.5, otherwise not easy loop compensation may be unstable, but there are some exceptions, such as the U.S. PI has introduced the TOP series chip can work under the conditions of duty cycle is greater than 0.5.Duty cycle by the transformer turns ratio to determine former deputy side, I am an anti-shock view is, first determine the reflected voltage (output voltage reflected through the transformer coupling the primary voltage value), reflecting a certain voltage range of voltage increase is duty cycle increases, lower power loss. Reduce the reflected voltage duty cycle decreases, increases power loss. Of course, this is a prerequisite, when the duty cycle increases, it means that the output diode conduction time, in order to maintain output stability, more time will be to ensure that the output capacitor discharge current, the output capacitor will be under even greater high-frequency ripple current erosion, while increasing its heat, which in many circumstances is not allowed.Duty cycle increases, change the transformer turns ratio, transformer leakage inductance will increase, its overall performance change, when the leakage inductance energy large enough, can switch to fully offset the large account space to bring low-loss, no further increase when the meaning of duty, because the leakage inductance may even be too high against the peak voltage breakdown switch. Leakage inductance as large, may make the output ripple, and other electromagnetic indicators deteriorated. When the duty hours, the high RMS current through the switch, transformer primary current rms and lowered the converter efficiency, but can improve the working conditions of the output capacitor to reduce fever. How to determine the transformer reflected voltage (duty cycle)Some netizens said switching power supply feedback loop parameter settings, work status analysis. Since high school mathematics is rather poor, "Automatic Control Theory," almost on the make-up, and for the door is still feeling fear, and now can not write a complete closed-loop system transfer function, zero for the system, the concept of feeling pole vague, see Bode plot is only about to see is a divergence or convergence, so the feedback compensation can not nonsense, but there are a number of recommendations. If you have some mathematical skills, and then have some time to learn then the University of textbooks, "Principles of Automatic Control" digest look carefully to find out, combined with practical switching power supply circuit, according to the work of state for analysis. Will be harvested, the Forum has a message, "coach feedback loop to study the design, debugging," in which CMG good answer, I think we can reference.Then today, on the duty cycle of flyback power supply (I am concerned about the reflected voltage, consistent with the duty cycle), the duty cycle with the voltage selection switch is related to some early flyback switching power supply using a low pressure tube, such as 600V or 650V AC 220V input power as a switch, perhaps when the production process, high pressure tubes, easy to manufacture, or low-pressure pipes are more reasonable conduction losses and switching characteristics, as this line reflected voltage can not be too high, otherwise the work order to switch the security context of loss of power absorbing circuit is quite impressive.Reflected voltage 600V tube proved not more than 100V, 650V tube reflected voltage not greater than 120V, the leakage inductance voltage spike when the tubes are clamped at 50V 50V working margin. Now that the MOS raise the level of manufacturing process control, flyback power supplies are generally used 700V or 750V or 800-900V the switch. Like this circuit, overvoltage capability against a number of switching transformer reflected voltage can be done a bit higher, the maximum reflected voltage in the 150V is appropriate, to obtain better overall performance.TOP PI's recommendation for the 135V chipset with transient voltage suppression diode clamp. But his evaluation board generally reflected voltage to be lower than the value at around 110V. Both types have their advantages and disadvantages:Category: shortcomings against over-voltage, low duty cycle is small, a large pulse current transformer primary. Advantages: small transformer leakage inductance, electromagnetic radiation and low ripple index higher switch loss, the conversion efficiency is not necessarily lower than the second.The second category: a large number of shortcomings of power loss, a large number of transformer leakage inductance, the ripple worse. Advantages: Some strong against over-voltage, large duty cycle, lower transformer losses and efficiency higher.Reflected voltage flyback power supply and a determining factorReflected voltage flyback power supply with a parameter related to that is the output voltage, output voltage, the lower the larger the transformer turns ratio, the greater the transformer leakage inductance, switch to withstand higher voltage breakdown switch is possible to absorb power consumption is higher, has the potential to permanently absorb the circuit power device failure (particularly with transient voltage suppression diode circuits). In the design of low-voltage low-power flyback power output optimization process must be handled with care, its approach has several:1, using a large core of a power level lower leakage inductance, which can improve the low-voltage flyback power conversion efficiency, reduce losses, reduce output ripple and improve multi-output power of the cross regulation in general is common in household appliances with a switch power, such as CD-ROM drive, DVB set-top boxes.2, if the conditions were not increased core, can reduce the reflected voltage, reducing the duty cycle. Reduce the reflected voltage can reduce the leakage inductance but may reduce the power conversion efficiency, which is a contradiction between the two, must have an alternative process to find a suitable point, replace the transformer during the experiment can detect the transformer original side of the anti-peak voltage, peak voltage to minimize the anti-pulse width, and magnitude of the work safety margin increase converter. Generally reflected voltage 110V when appropriate.3, enhance the coupling, reducing losses, the introduction of new technologies, and the routing process, transformers to meet the security specifications will between the primary and secondary side to insulation measures, such as pad tape, plus side air insulation tape. These will affect the performance of transformer leakage inductance, the reality can be used in production around the primary winding secondary wrapping method. Or sub-system with a triple insulated wire wound to remove the insulation between the initial level, can enhance the coupling, even use wide copper winding.The article refers to low voltage output is less than or equal to 5V output, as this type of small power supply, my experience is that the power output of more than 20W output can use a forward, get the best value for money, of course, this is not the right decision , and personal habits, relationship between the application environment, the next time to talk about the flyback power supply with a magnetic core, magnetic circuit air gap opening some understanding, I hope you receive adequate guidance.Flyback power transformer core magnetization state at work in one way, it needs to open the air gap magnetic circuit, similar to the pulsating direct current sensor. Part of the magnetic coupling through the air gap. Why I understand the principle of open air gap as follows: As the power ferrite also has a similar rectangle of the operating characteristics (hysteresis loop), operating characteristics curve in the Y-axis magnetic induction (B), now the general production process saturation point in 400mT above, thegeneral value in the design of this value should be more appropriate in the 200-300mT, X-axis magnetic field strength (H) the value of current intensity is proportional to the magnetization. Open magnetic circuit air gap equal to the magnetic hysteresis loop to the X axis tilt, in the same magnetic induction intensity, can withstand a greater magnetizing current, equivalent to core store more energy, this energy cut-off switch When spilled into the load through the transformer secondary circuit, flyback power core to open the air gap is twofold. One is to transfer more energy, and the second to prevent the core into saturation.Flyback Power Transformer magnetization state in one way, not only to pass through the magnetic coupling energy, is also responsible for input and output isolation voltage transform multiple roles. Therefore, the treatment gap need to be very careful, the air gap leakage inductance can become too large, increase the hysteresis loss, iron loss, copper loss increases, affecting the power of the whole performance. Air gap is too small has the potential to transformer core saturation, resulting in damage to powerThe so-called flyback power supply is continuous and discontinuous mode transformer working conditions, working in full load condition in the power transformer complete transfer, or incomplete transmission mode. General design of the working environment, conventional flyback power supply should work in continuous mode, this switch, circuit loss are relatively small, and can reduce the stress of work input and output capacitors, but that there are some exceptions.Requires in particular that: As the characteristics of the flyback power supply is also more suitable for design into a high-voltage power supply, and high-voltage power transformers generally work in discontinuous mode, I understand the need for as high voltage power supply output voltage of the rectifier diodes. Because of the manufacturing process characteristics, high-tension diode, reverse recovery time is long, low speed, the current continuous state, the diode has a positive bias in the recovery, reverse recovery energy loss is very large, is not conducive to converter performance increase, ranging from reduced conversion efficiency, rectifiers, severe fever, weight is even burnt rectifier. As in the intermittent mode, the diode is reverse biased under zero bias, loss can be reduced to a relatively low level. Therefore, high voltage power supply work in discontinuous mode, and the frequency can not be too high.Another type of flyback power supply work in the critical state, the general type of power supply work in FM, or FM-width-modulated dual-mode, a number of low-cost self-excitation power (RCC) is often used this form in order to ensure stable output transformer As the operating frequency, output current or input voltage change, close to the fully loaded transformer is always maintained at between continuous and intermittent, thispower is only suitable for small power output, otherwise the handling characteristics of electromagnetic compatibility will be a headacheFlyback switching power supply transformer should work in continuous mode, it required relatively large winding inductance, of course, is to some extent continuous, excessive pursuit of absolute continuity is not realistic, may need a great core, very much coil turns, accompanied by a large leakage inductance and distributed capacitance, worth the trouble. So how does this parameter to determine, through repeated practice, and analysis of peer design, I think, in the nominal voltage input, the output reached 50% and 60% transformer from intermittent, continuous state of transition to more appropriate. Or at the highest input voltage state, the full output, the transformer can transition to the continuous state on it.开关电源状态，电源工作在高频率，高脉冲的模拟电路的一个比较特殊的一种。
电气外文文献及翻译--开关电源设计
外文文献：Switching Power Supply DesignSwitching power supply work in high frequency, high pulse state, are analog circuits in a rather special kind. Cloth boards to follow the principle of high-frequency circuit wiring.First, layout:Pulse voltage connection as short as possible, including input switch connected to the transformer, output transformer to the rectifier tube cable. Pulse current loop as small as possible such as the input filter capacitor is returned to the transformer to the switch capacitor negative. Some out-ended output transformers are the output rectifier to the output capacitor back to transformer circuit X capacitor as close as possible to the input switching power supply, input lines should be avoided in parallel with other circuits, should be avoided. Y capacitor should be placed in the chassis ground terminal or FG connectors. A total of touch induction and transformer to maintain a certain distance in order to avoid magnetic coupling. Such as poor handling of feeling in between inductor and transformer plus a shield, over a number of EMC performance for power supply to the greater impact.General the output capacitor can be used the other two a close rectifier output terminal should be close to, can affect the power supply output ripple index, two small capacitor in parallel results should be better than using a large capacitor. Heating devices to maintain a certain distance, and electrolytic capacitors to extend machine life, electrolytic capacitors is the switching power supply bottleneck life, such as transformers, power control, high power resistors and electrolytic to maintain the distance required between the electrolyte leaving space for heat dissipation , conditions permitting, may be placed in the inlet.Control part to pay attention to: Weak signal high impedance circuit connected to sample the feedback loop as short as in the processing as far as possible avoid interference, the current sampling signal circuits, in particular the current control circuit, easy to deal with some unexpected bad The accident, which had some skill,now to 3843 the circuit example shown in Figure (1) Figure 1 better than Yu Figure 2, Figure 2 Zai full time by observing the current waveform oscilloscope Mingxian superimposed spikes, Youyuganrao limited flow ratio design Zhi Dian low, Figure 1 there is no such phenomenon, there are switch drive signal circuit, switch resistance should be close to the switch driver can switch the work to improve the reliability of this and the high DC impedance voltage power MOSFET driver characteristics. Second, routingAlignment of current density: now the majority of electronic circuit board using insulated copper constitute tied. Common PCB copper thickness of 35μm, the alignment value can be obtained in accordance with 1A/mm experience the value of current density, the specific calculations can be found in textbooks. To ensure the alignment principles of mechanical strength should be greater than or equal to the width of 0.3mm (other non-power supply circuit board may be smaller minimum line width). PCB copper thickness of 70μm is also common in switching power supply, then the current density can be higher.Add that, now Changyong circuit board design tool design software generally items such as line width, line spacing, hole size and so dry plate Guo Jin Xing parameters can be set. In the design of circuit boards, design software automatically in accordance with the specifications, can save time, reduce some of the workload and reduce the error rate.Generally higher on the reliability of lines or line density wiring can be used double panel. Characterized by moderate cost, high reliability, to meet most applications.The ranks of some of the power module products are also used plywood, mainly to facilitate integration of power devices such as transformer inductance to optimize wiring, cooling and other power tube. Good consistency with the craft beautiful, transformer cooling good advantage, but its disadvantage is high cost, poor flexibility, only suitable for industrial mass production.Single-sided, the market circulation of almost universal switching power supply using single-sided circuit board, which has the advantage of lower costs in thedesign and production technology are also taken some measures to ensure its performance.Single PCB design today to talk about some experience, as a single panel with low cost, easy-to-manufacture features, the switching power supply circuit has been widely used, because of its side tied only copper, the device's electrical connections, mechanical fixation should rely on the copper layer, the processing must be careful.To ensure good performance of the mechanical structure welding, single-sided pad should be slightly larger to ensure that the copper and substrate tied good focus, and thus will not be shocked when the copper strip, broken off. General welding ring width should be greater than 0.3mm. Pad diameter should be slightly larger than the diameter of the device pins, but not too large, to ensure pin and pad by the solder connection between the shortest distance, plate hole size should not hinder the normal conditions for the degree of investigation, the pad diameter is generally greater than pin diameter 0.1-0.2mm. Multi-pin device to ensure a smooth investigation documents can also be larger.Electrical connection should be as wide as possible, in principle, should be larger than the width of pad diameter, special circumstances should be connected in line with the need to widen the intersection pad (commonly known as Generation tears), to avoid breaking certain conditions, line and pad. Principle of minimum line width should be greater than 0.5mm.Single-board components to be close to the circuit board. Need overhead cooling device to device and circuit board between the pins plus casing, can play a supporting device and increase the dual role of insulation to minimize or avoid external shocks on the pad and the pin junction impact and enhance the firmness of welding. Circuit board supporting the weight of large parts can increase the connection point, can enhance joint strength between the circuit board, such as transformers, power device heat sink.Single-sided welding pins without affecting the surface and the shell spacing of the prior conditions, it can be to stay longer, the advantage of increased strength of welded parts, increase weld area and immediately found a Weld phenomenon. Shearpin long legs, the welding force smaller parts. In Taiwan, the Japanese often use the device pins in the welding area and the circuit board was bent 45 degrees, and then welding process, its reasoning Ibid. Double panel today to talk about the design of some of the issues, in relatively high number of requests, or take the line density of the larger application environments using double-sided PCB, its performance and various indicators of a lot better than a single panel.Two-panel pad as holes have been high intensity metal processing, welding ring smaller than a single panel, the pad hole diameter slightly larger in diameter than pins, as in the welding process solder solution conducive to penetrate through the top hole solder pad to increase the welding reliability. But there is a disadvantage if the hole is too large, wave soldering tin when the jet impact in the lower part of the device may go up, have some flaws.High current handling of alignment, line width in accordance with pre-quote processing, such as the width is not enough to go online in general can be used to increase the thickness of tin plating solution, the method has a good variety of1. Will take the line set to pad property, so that when the circuit board manufacturing solder alignment will not be covered, the whole hot air normally be tin plated.2. In the wiring by placing pads, the pad is set to take in line shape, pay attention to the pad holes set to zero.3. In the solder layer placed on line, this method is the most flexible, but not all PCB manufacturers will understand your intentions, needed captions. Place the line in the solder layer of the site will not coated solder tinning line several methods as above, to note that, if the alignment of a very wide all plated with tin in solder after the solder will bond a lot and distribution is very uneven, affecting appearance. Article tin can be used generally slender width in the 1 ~ 1.5mm, length can be determined according to lines, tin part of the interval 0.5 ~ 1mmDouble-sided circuit board for the layout, the alignment provides a very selective, make wiring more reasonable. On the ground, the power ground and signal ground must be separated, the two to converge in filter capacitors, in order to avoid a large pulsed current through the signal ground connection instability caused by unexpectedfactors, the signal control circuit grounding point as far as possible, a skill, as far as possible the alignment of the non-grounded wiring layer in the same place, the last shop in another layer of earth. Output line through the filter capacitors, the general first, and then to the load, input line must also pass capacitor, to the transformer, the theoretical basis is to ripple through trip filter capacitor.V oltage feedback sampling, in order to avoid high current through the alignment of the feedback voltage on the sampling point must be the most peripheral power output to increase the load effect of target machine.Alignment change from a wiring layer to another wiring layer generally used hole connected, not through the pin pad device to achieve, because the plug in the device may be damaged when the relationship between this connection, there is current in every passage of 1A, at least two through-hole, through hole diameter is greater than the principle of 0.5mm, 0.8mm generally processed ensure reliability.Cooling devices, in some small power supply, the circuit board traces can be and cooling, characterized by the alignment as generous as possible to increase the cooling area is not coated solder, conditions can even be placed over holes, enhanced thermal conductivity .Today to talk about the aluminum plate in the switching power supply application and multilayer printed circuit in the switching power supply applications.Aluminum plate by its own structure, has the following characteristics: very good thermal conductivity, single Mianfu copper, the device can only be placed in tied copper surface, can not open electrical connection hole so as not to place jumper in accordance with a single panel.Aluminum plate is generally placed patch device, switch, the output rectifier heat conduction through the substrate to go out, very low thermal resistance, high reliability can be achieved. Transformer with planar chip structure, but also through substrate cooling, the temperature is lower than the conventional, the same size transformer with a large aluminum plate structure available output power. Aluminum plate jumper bridge approach can be used. Aluminum plate power are generally composed by the two PCB, another one to place the control circuit board, through thephysical connection between the two boards is integrated.As the excellent thermal conductivity of aluminum plate, in a small amount of manual welding more difficult, solder cooling too fast and prone to problems of a simple and practical way of existing, an ironing ordinary iron (preferably temperature regulation function), over and iron for the last, fixed, and temperature to 150 ℃ and above the aluminum plate on the iron, heating time, and then affix the components according to conventional methods and welding, soldering iron temperature is appropriate to the device easy to , is too high when the device may be damaged, or even copper strip aluminum plate, the temperature is too low welding effect is not good, to be flexible.Recent years, with the multi-layer circuit board applications in switching power supply circuit, printed circuit transformer makes it possible, due to multilayer, smaller spacing also can take advantage of Bianya Qi window section, the main circuit board can be re- Add 1-2 formed by the multilayer printed coil to use the window, the purpose of reducing circuit current density, due to adopt printed coil, reducing manual intervention, transformers consistency, surface structure, low leakage inductance, coupling good . Open-type magnetic core, good heat dissipation. Because of its many advantages, is conducive to mass production, it is widely used. But the research and development of large initial investment, not suitable for small-scale health.Switching power supply is divided into, two forms of isolation and non-isolated, isolated here mainly to talk about switching power supply topologies form below, non-specified, are to isolate the power. Isolated power supply in accordance with the structure of different forms, can be divided into two categories: a forward and flyback. Flyback transformer primary side means that when the Vice-edge conduction cut-off, transformer storage. Close of the primary, secondary side conduction, the energy released to the load of work status, general conventional flyback power multiplex, twin-tube is not common. Forward refers to the primary conduction in transformer secondary side while the corresponding output voltage is induced into the load, the direct transfer of energy through the transformer. According to specifications can be divided into conventional forward, including the single-transistor forward, DoubleForward. Half-bridge, bridge circuits are all forward circuit.Forward and flyback circuits have their own characteristics in the process of circuit design to achieve optimal cost-effective, can be applied flexibly. Usually in the low-power flyback can be adopted. Slightly larger forward circuit can use a single tube, medium-power can use Double Forward circuit or half-bridge circuit, low-voltage push-pull circuit, and the half-bridge work in the same state. High power output, generally used bridge circuit, low voltage can be applied push-pull circuit. Flyback power supply because of its simple structure, and to cut the size of a similar size and transformer inductance, the power supply in the medium has been widely applied. Presentation referred to in some flyback power supply can do dozens of watts, output power exceeding 100 watts would be no advantage to them difficult. Under normal circumstances, I think so, but it can not be generalized, PI's TOP chips can do 300 watts, an article describes the flyback power supply can be on the KW, but not seen in kind.Power output and the output voltage level.Flyback power transformer leakage inductance is a critical parameter, because the power needs of the flyback transformer stored energy, to make full use of transformer core, the general must be open in the magnetic circuit air gap, the aim is to change the core hysteresis back line of the slope, so that transformers can withstand the impact of a large pulse current, which is not core into saturation non-linear state, the magnetic circuit in the high reluctance air gap in the state, generated in the magnetic flux leakage is much larger than completely closed magnetic circuit .Transformer coupling between the first pole is the key factor determining the leakage inductance, the coil to be very close as far as possible the first time, the sandwich can be used around the law, but this would increase the distributed capacitance transformer. Use core as core with a long window, can reduce the leakage inductance, such as the use of EE, EF, EER, PQ-based EI type magnetic core effective than good.The duty cycle of flyback power supplies, in principle, the maximum duty cycle of flyback power supply should be less than 0.5, otherwise not easy loopcompensation may be unstable, but there are some exceptions, such as the U.S. PI has introduced the TOP series chip can work under the conditions of duty cycle is greater than 0.5.Duty cycle by the transformer turns ratio to determine former deputy side, I am an anti-shock view is, first determine the reflected voltage (output voltage reflected through the transformer coupling the primary voltage value), reflecting a certain voltage range of voltage increase is duty cycle increases, lower power loss. Reduce the reflected voltage duty cycle decreases, increases power loss. Of course, this is a prerequisite, when the duty cycle increases, it means that the output diode conduction time, in order to maintain output stability, more time will be to ensure that the output capacitor discharge current, the output capacitor will be under even greater high-frequency ripple current erosion, while increasing its heat, which in many circumstances is not allowed.Duty cycle increases, change the transformer turns ratio, transformer leakage inductance will increase, its overall performance change, when the leakage inductance energy large enough, can switch to fully offset the large account space to bring low-loss, no further increase when the meaning of duty, because the leakage inductance may even be too high against the peak voltage breakdown switch. Leakage inductance as large, may make the output ripple, and other electromagnetic indicators deteriorated. When the duty hours, the high RMS current through the switch, transformer primary current rms and lowered the converter efficiency, but can improve the working conditions of the output capacitor to reduce fever. How to determine the transformer reflected voltage (duty cycle)Some netizens said switching power supply feedback loop parameter settings, work status analysis. Since high school mathematics is rather poor, "Automatic Control Theory," almost on the make-up, and for the door is still feeling fear, and now can not write a complete closed-loop system transfer function, zero for the system, the concept of feeling pole vague, see Bode plot is only about to see is a divergence or convergence, so the feedback compensation can not nonsense, but there are a number of recommendations. If you have some mathematical skills, and then have some timeto learn then the University of textbooks, "Principles of Automatic Control" digest look carefully to find out, combined with practical switching power supply circuit, according to the work of state for analysis. Will be harvested, the Forum has a message, "coach feedback loop to study the design, debugging," in which CMG good answer, I think we can reference.Then today, on the duty cycle of flyback power supply (I am concerned about the reflected voltage, consistent with the duty cycle), the duty cycle with the voltage selection switch is related to some early flyback switching power supply using a low pressure tube, such as 600V or 650V AC 220V input power as a switch, perhaps when the production process, high pressure tubes, easy to manufacture, or low-pressure pipes are more reasonable conduction losses and switching characteristics, as this line reflected voltage can not be too high, otherwise the work order to switch the security context of loss of power absorbing circuit is quite impressive.Reflected voltage 600V tube proved not more than 100V, 650V tube reflected voltage not greater than 120V, the leakage inductance voltage spike when the tubes are clamped at 50V 50V working margin. Now that the MOS raise the level of manufacturing process control, flyback power supplies are generally used 700V or 750V or 800-900V the switch. Like this circuit, overvoltage capability against a number of switching transformer reflected voltage can be done a bit higher, the maximum reflected voltage in the 150V is appropriate, to obtain better overall performance.TOP PI's recommendation for the 135V chipset with transient voltage suppression diode clamp. But his evaluation board generally reflected voltage to be lower than the value at around 110V. Both types have their advantages and disadvantages: Category: shortcomings against over-voltage, low duty cycle is small, a large pulse current transformer primary. Advantages: small transformer leakage inductance, electromagnetic radiation and low ripple index higher switch loss, the conversion efficiency is not necessarily lower than the second.The second category: a large number of shortcomings of power loss, a large number of transformer leakage inductance, the ripple worse. Advantages: Some strongagainst over-voltage, large duty cycle, lower transformer losses and efficiency higher.Reflected voltage flyback power supply and a determining factorReflected voltage flyback power supply with a parameter related to that is the output voltage, output voltage, the lower the larger the transformer turns ratio, the greater the transformer leakage inductance, switch to withstand higher voltage breakdown switch is possible to absorb power consumption is higher, has the potential to permanently absorb the circuit power device failure (particularly with transient voltage suppression diode circuits). In the design of low-voltage low-power flyback power output optimization process must be handled with care, its approach has several:1, using a large core of a power level lower leakage inductance, which can improve the low-voltage flyback power conversion efficiency, reduce losses, reduce output ripple and improve multi-output power of the cross regulation in general is common in household appliances with a switch power, such as CD-ROM drive, DVB set-top boxes.2, if the conditions were not increased core, can reduce the reflected voltage, reducing the duty cycle. Reduce the reflected voltage can reduce the leakage inductance but may reduce the power conversion efficiency, which is a contradiction between the two, must have an alternative process to find a suitable point, replace the transformer during the experiment can detect the transformer original side of the anti-peak voltage, peak voltage to minimize the anti-pulse width, and magnitude of the work safety margin increase converter. Generally reflected voltage 110V when appropriate.3, enhance the coupling, reducing losses, the introduction of new technologies, and the routing process, transformers to meet the security specifications will between the primary and secondary side to insulation measures, such as pad tape, plus side air insulation tape. These will affect the performance of transformer leakage inductance, the reality can be used in production around the primary winding secondary wrapping method. Or sub-system with a triple insulated wire wound to remove the insulation between the initial level, can enhance the coupling, even use wide copper winding.The article refers to low voltage output is less than or equal to 5V output, as thistype of small power supply, my experience is that the power output of more than 20W output can use a forward, get the best value for money, of course, this is not the right decision , and personal habits, relationship between the application environment, the next time to talk about the flyback power supply with a magnetic core, magnetic circuit air gap opening some understanding, I hope you receive adequate guidance.Flyback power transformer core magnetization state at work in one way, it needs to open the air gap magnetic circuit, similar to the pulsating direct current sensor. Part of the magnetic coupling through the air gap. Why I understand the principle of open air gap as follows: As the power ferrite also has a similar rectangle of the operating characteristics (hysteresis loop), operating characteristics curve in the Y-axis magnetic induction (B), now the general production process saturation point in 400mT above, the general value in the design of this value should be more appropriate in the 200-300mT, X-axis magnetic field strength (H) the value of current intensity is proportional to the magnetization. Open magnetic circuit air gap equal to the magnetic hysteresis loop to the X axis tilt, in the same magnetic induction intensity, can withstand a greater magnetizing current, equivalent to core store more energy, this energy cut-off switch When spilled into the load through the transformer secondary circuit, flyback power core to open the air gap is twofold. One is to transfer more energy, and the second to prevent the core into saturation.Flyback Power Transformer magnetization state in one way, not only to pass through the magnetic coupling energy, is also responsible for input and output isolation voltage transform multiple roles. Therefore, the treatment gap need to be very careful, the air gap leakage inductance can become too large, increase the hysteresis loss, iron loss, copper loss increases, affecting the power of the whole performance. Air gap is too small has the potential to transformer core saturation, resulting in damage to powerThe so-called flyback power supply is continuous and discontinuous mode transformer working conditions, working in full load condition in the power transformer complete transfer, or incomplete transmission mode. General design of the working environment, conventional flyback power supply should work incontinuous mode, this switch, circuit loss are relatively small, and can reduce the stress of work input and output capacitors, but that there are some exceptions.Requires in particular that: As the characteristics of the flyback power supply is also more suitable for design into a high-voltage power supply, and high-voltage power transformers generally work in discontinuous mode, I understand the need for as high voltage power supply output voltage of the rectifier diodes. Because of the manufacturing process characteristics, high-tension diode, reverse recovery time is long, low speed, the current continuous state, the diode has a positive bias in the recovery, reverse recovery energy loss is very large, is not conducive to converter performance increase, ranging from reduced conversion efficiency, rectifiers, severe fever, weight is even burnt rectifier. As in the intermittent mode, the diode is reverse biased under zero bias, loss can be reduced to a relatively low level. Therefore, high voltage power supply work in discontinuous mode, and the frequency can not be too high.Another type of flyback power supply work in the critical state, the general type of power supply work in FM, or FM-width-modulated dual-mode, a number of low-cost self-excitation power (RCC) is often used this form in order to ensure stable output transformer As the operating frequency, output current or input voltage change, close to the fully loaded transformer is always maintained at between continuous and intermittent, this power is only suitable for small power output, otherwise the handling characteristics of electromagnetic compatibility will be a headache Flyback switching power supply transformer should work in continuous mode, it required relatively large winding inductance, of course, is to some extent continuous, excessive pursuit of absolute continuity is not realistic, may need a great core, very much coil turns, accompanied by a large leakage inductance and distributed capacitance, worth the trouble. So how does this parameter to determine, through repeated practice, and analysis of peer design, I think, in the nominal voltage input, the output reached 50% and 60% transformer from intermittent, continuous state of transition to more appropriate. Or at the highest input voltage state, the full output, the transformer can transition to the continuous state on it.中文译文：开关电源设计开关电源状态，电源工作在高频率，高脉冲的模拟电路的一个比较特殊的一种。
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Switching Power Supply DesignSwitching power supply work in high frequency, high pulse state, are analog circuits in a rather special kind. Cloth boards to follow the principle of high-frequency circuit wiring.1, layout:Pulse voltage connection as short as possible, including input switch connected to the transformer, output transformer to the rectifier tube cable. Pulse current loop as small as possible such as the input filter capacitor is returned to the transformer to the switch capacitor negative. Some out-ended output transformers are the output rectifier to the output capacitor back to transformer circuit X capacitor as close as possible to the input switching power supply, input lines should be avoided in parallel with other circuits, should be avoided. Y capacitor should be placed in the chassis ground terminal or FG connectors. A total of touch induction and transformer to maintain a certain distance in order to avoid magnetic coupling. Such as poor handling of feeling in between inductor and transformer plus a shield, over a number of EMC performance for power supply to the greater impact.General the output capacitor can be used the other two a close rectifier output terminal should be close to, can affect the power supply output ripple index, two small capacitor in parallel results should be better than using a large capacitor. Heating devices to maintain a certain distance, and electrolytic capacitors to extend machine life, electrolytic capacitors is the switching power supply bottleneck life, such as transformers, power control, high power resistors and electrolytic to maintain the distance required between the electrolyte leaving space for heat dissipation , conditions permitting, may be placed in the inlet.Control part to pay attention to: Weak signal high impedance circuit connected to sample the feedback loop as short as in the processing as far as possible avoid interference, the current sampling signal circuits, in particular the current control circuit, easy to deal with some unexpected bad The accident, which had some skill, now to 3843 the circuit example shown in Figure (1) Figure 1 better than Yu Figure 2, Figure 2 Zai full time by observing the current waveform oscilloscope Mingxian superimposed spikes, Youyuganrao limited flow ratio design Zhi Dian low, Figure 1 there is no such phenomenon, there are switch drive signal circuit, switch resistance should be close to the switch driver can switch the work to improve the reliability of this and the high DC impedance voltage power MOSFET driver characteristics.Second, routingAlignment of current density: now the majority of electronic circuit board using insulated copper constitute tied. Common PCB copper thickness of 35μm, the alignment valuecan be obtained in accordance with 1A/mm experience the value of current density, the specific calculations can be found in textbooks. To ensure the alignment principles of mechanical strength should be greater than or equal to the width of 0.3mm (other non-power supply circuit board may be smaller minimum line width). PCB copper thickness of 70μm is also common in switching power supply, then the current density can be higher.Add that, now Changyong circuit board design tool design software generally items such as line width, line spacing, hole size and so dry plate Guo Jin Xing parameters can be set. In the design of circuit boards, design software automatically in accordance with the specifications, can save time, reduce some of the workload and reduce the error rate.Generally higher on the reliability of lines or line density wiring can be used double panel. Characterized by moderate cost, high reliability, to meet most applications.The ranks of some of the power module products are also used plywood, mainly to facilitate integration of power devices such as transformer inductance to optimize wiring, cooling and other power tube. Good consistency with the craft beautiful, transformer cooling good advantage, but its disadvantage is high cost, poor flexibility, only suitable for industrial mass production.Single-sided, the market circulation of almost universal switching power supply using single-sided circuit board, which has the advantage of lower costs in the design and production technology are also taken some measures to ensure its performance.Single PCB design today to talk about some experience, as a single panel with low cost, easy-to-manufacture features, the switching power supply circuit has been widely used, because of its side tied only copper, the device's electrical connections, mechanical fixation should rely on the copper layer, the processing must be careful.To ensure good performance of the mechanical structure welding, single-sided pad should be slightly larger to ensure that the copper and substrate tied good focus, and thus will not be shocked when the copper strip, broken off. General welding ring width should be greater than 0.3mm. Pad diameter should be slightly larger than the diameter of the device pins, but not too large, to ensure pin and pad by the solder connection between the shortest distance, plate hole size should not hinder the normal conditions for the degree of investigation, the pad diameter is generally greater than pin diameter 0.1-0.2mm. Multi-pin device to ensure a smooth investigation documents can also be larger.Electrical connection should be as wide as possible, in principle, should be larger than the width of pad diameter, special circumstances should be connected in line with the need to widen the intersection pad (commonly known as Generation tears), to avoid breaking certain conditions, line and pad. Principle of minimum line width should be greater than 0.5mm.Single-board components to be close to the circuit board. Need overhead cooling device to device and circuit board between the pins plus casing, can play a supporting deviceand increase the dual role of insulation to minimize or avoid external shocks on the pad and the pin junction impact and enhance the firmness of welding. Circuit board supporting the weight of large parts can increase the connection point, can enhance joint strength between the circuit board, such as transformers, power device heat sink.Single-sided welding pins without affecting the surface and the shell spacing of the prior conditions, it can be to stay longer, the advantage of increased strength of welded parts, increase weld area and immediately found a Weld phenomenon. Shear pin long legs, the welding force smaller parts. In T aiwan, the Japanese often use the device pins in the welding area and the circuit board was bent 45 degrees, and then welding process, its reasoning Ibid. Double panel today to talk about the design of some of the issues, in relatively high number of requests, or take the line density of the larger application environments using double-sided PCB, its performance and various indicators of a lot better than a single panel.Two-panel pad as holes have been high intensity metal processing, welding ring smaller than a single panel, the pad hole diameter slightly larger in diameter than pins, as in the welding process solder solution conducive to penetrate through the top hole solder pad to increase the welding reliability. But there is a disadvantage if the hole is too large, wave soldering tin when the jet impact in the lower part of the device may go up, have some flaws.High current handling of alignment, line width in accordance with pre-quote processing, such as the width is not enough to go online in general can be used to increase the thickness of tin plating solution, the method has a good variety of1. Will take the line set to pad property, so that when the circuit board manufacturing solder alignment will not be covered, the whole hot air normally be tin plated.2. In the wiring by placing pads, the pad is set to take in line shape, pay attention to the pad holes set to zero.3. In the solder layer placed on line, this method is the most flexible, but not all PCB manufacturers will understand your intentions, needed captions. Place the line in the solder layer of the site will not coated solder tinning line several methods as above, to note that, if the alignment of a very wide all plated with tin in solder after the solder will bond a lot and distribution is very uneven, affecting appearance. Article tin can be used generally slender width in the 1 ~ 1.5mm, length can be determined according to lines, tin part of the interval 0.5 ~ 1mmDouble-sided circuit board for the layout, the alignment provides a very selective, make wiring more reasonable. On the ground, the power ground and signal ground must be separated, the two to converge in filter capacitors, in order to avoid a large pulsed current through the signal ground connection instability caused by unexpected factors, the signal control circuit grounding point as far as possible, a skill, as far as possible the alignment of the non-grounded wiring layer in the same place, the last shop in another layer of earth.Output line through the filter capacitors, the general first, and then to the load, input line must also pass capacitor, to the transformer, the theoretical basis is to ripple through trip filter capacitor.Voltage feedback sampling, in order to avoid high current through the alignment of the feedback voltage on the sampling point must be the most peripheral power output to increase the load effect of target machine.Alignment change from a wiring layer to another wiring layer generally used hole connected, not through the pin pad device to achieve, because the plug in the device may be damaged when the relationship between this connection, there is current in every passage of 1A, at least two through-hole, through hole diameter is greater than the principle of 0.5mm, 0.8mm generally processed ensure reliability.Cooling devices, in some small power supply, the circuit board traces can be and cooling, characterized by the alignment as generous as possible to increase the cooling area is not coated solder, conditions can even be placed over holes, enhanced thermal conductivity .Today to talk about the aluminum plate in the switching power supply application and multilayer printed circuit in the switching power supply applications.Aluminum plate by its own structure, has the following characteristics: very good thermal conductivity, single Mianfu copper, the device can only be placed in tied copper surface, can not open electrical connection hole so as not to place jumper in accordance with a single panel.Aluminum plate is generally placed patch device, switch, the output rectifier heat conduction through the substrate to go out, very low thermal resistance, high reliability can be achieved. Transformer with planar chip structure, but also through substrate cooling, the temperature is lower than the conventional, the same size transformer with a large aluminum plate structure available output power. Aluminum plate jumper bridge approach can be used. Aluminum plate power are generally composed by the two PCB, another one to place the control circuit board, through the physical connection between the two boards is integrated.As the excellent thermal conductivity of aluminum plate, in a small amount of manual welding more difficult, solder cooling too fast and prone to problems of a simple and practical way of existing, an ironing ordinary iron (preferably temperature regulation function), over and iron for the last, fixed, and temperature to 150 ℃ and above the aluminum plate on the iron, heating time, and then affix the components according to conventional methods and welding, soldering iron temperature is appropriate to the device easy to , is too high when the device may be damaged, or even copper strip aluminum plate, the temperature is too low welding effect is not good, to be flexible.Recent years, with the multi-layer circuit board applications in switching powersupply circuit, printed circuit transformer makes it possible, due to multilayer, smaller spacing also can take advantage of Bianya Qi window section, the main circuit board can be re- Add 1-2 formed by the multilayer printed coil to use the window, the purpose of reducing circuit current density, due to adopt printed coil, reducing manual intervention, transformers consistency, surface structure, low leakage inductance, coupling good . Open-type magnetic core, good heat dissipation. Because of its many advantages, is conducive to mass production, it is widely used. But the research and development of large initial investment, not suitable for small-scale health.Switching power supply is divided into, two forms of isolation and non-isolated, isolated here mainly to talk about switching power supply topologies form below,non-specified, are to isolate the power. Isolated power supply in accordance with the structure of different forms, can be divided into two categories: a forward and flyback. Flyback transformer primary side means that when the Vice-edge conduction cut-off, transformer storage. Close of the primary, secondary side conduction, the energy released to the load of work status, general conventional flyback power multiplex, twin-tube is not common. Forward refers to the primary conduction in transformer secondary side while the corresponding output voltage is induced into the load, the direct transfer of energy through the transformer. According to specifications can be divided into conventional forward, including the single-transistor forward, Double Forward. Half-bridge, bridge circuits are all forward circuit.Forward and flyback circuits have their own characteristics in the process of circuit design to achieve optimal cost-effective, can be applied flexibly. Usually in the low-power flyback can be adopted. Slightly larger forward circuit can use a single tube, medium-power can use Double Forward circuit or half-bridge circuit, low-voltage push-pull circuit, and the half-bridge work in the same state. High power output, generally used bridge circuit, low voltage can be applied push-pull circuit.Flyback power supply because of its simple structure, and to cut the size of a similar size and transformer inductance, the power supply in the medium has been widely applied. Presentation referred to in some flyback power supply can do dozens of watts, output power exceeding 100 watts would be no advantage to them difficult. Under normal circumstances, I think so, but it can not be generalized, PI's TOP chips can do 300 watts, an article describes the flyback power supply can be on the KW, but not seen in kind. Power output and the output voltage level.Flyback power transformer leakage inductance is a critical parameter, because the power needs of the flyback transformer stored energy, to make full use of transformer core, the general must be open in the magnetic circuit air gap, the aim is to change the core hysteresis back line of the slope, so that transformers can withstand the impact of a largepulse current, which is not core into saturation non-linear state, the magnetic circuit in the high reluctance air gap in the state, generated in the magnetic flux leakage is much larger than completely closed magnetic circuit .Transformer coupling between the first pole is the key factor determining the leakage inductance, the coil to be very close as far as possible the first time, the sandwich can be used around the law, but this would increase the distributed capacitance transformer. Use core as core with a long window, can reduce the leakage inductance, such as the use of EE, EF, EER, PQ-based EI type magnetic core effective than good.The duty cycle of flyback power supplies, in principle, the maximum duty cycle of flyback power supply should be less than 0.5, otherwise not easy loop compensation may be unstable, but there are some exceptions, such as the U.S. PI has introduced the TOP series chip can work under the conditions of duty cycle is greater than 0.5.Duty cycle by the transformer turns ratio to determine former deputy side, I am an anti-shock view is, first determine the reflected voltage (output voltage reflected through the transformer coupling the primary voltage value), reflecting a certain voltage range of voltage increase is duty cycle increases, lower power loss. Reduce the reflected voltage duty cycle decreases, increases power loss. Of course, this is a prerequisite, when the duty cycle increases, it means that the output diode conduction time, in order to maintain output stability, more time will be to ensure that the output capacitor discharge current, the output capacitor will be under even greater high-frequency ripple current erosion, while increasing its heat, which in many circumstances is not allowed.Duty cycle increases, change the transformer turns ratio, transformer leakage inductance will increase, its overall performance change, when the leakage inductance energy large enough, can switch to fully offset the large account space to bring low-loss, no further increase when the meaning of duty, because the leakage inductance may even be too high against the peak voltage breakdown switch. Leakage inductance as large, may make the output ripple, and other electromagnetic indicators deteriorated. When the duty hours, the high RMS current through the switch, transformer primary current rms and lowered the converter efficiency, but can improve the working conditions of the output capacitor to reduce fever. How to determine the transformer reflected voltage (duty cycle)Some netizens said switching power supply feedback loop parameter settings, work status analysis. Since high school mathematics is rather poor, "Automatic Control Theory," almost on the make-up, and for the door is still feeling fear, and now can not write a complete closed-loop system transfer function, zero for the system, the concept of feeling pole vague, see Bode plot is only about to see is a divergence or convergence, so the feedback compensation can not nonsense, but there are a number of recommendations. If you have some mathematical skills, and then have some time to learn then the University of textbooks,"Principles of Automatic Control" digest look carefully to find out, combined with practical switching power supply circuit, according to the work of state for analysis. Will be harvested, the Forum has a message, "coach feedback loop to study the design, debugging," in which CMG good answer, I think we can reference.Then today, on the duty cycle of flyback power supply (I am concerned about the reflected voltage, consistent with the duty cycle), the duty cycle with the voltage selection switch is related to some early flyback switching power supply using a low pressure tube, such as 600V or 650V AC 220V input power as a switch, perhaps when the production process, high pressure tubes, easy to manufacture, or low-pressure pipes are more reasonable conduction losses and switching characteristics, as this line reflected voltage can not be too high, otherwise the work order to switch the security context of loss of power absorbing circuit is quite impressive.Reflected voltage 600V tube proved not more than 100V, 650V tube reflected voltage not greater than 120V, the leakage inductance voltage spike when the tubes are clamped at 50V 50V working margin. Now that the MOS raise the level of manufacturing process control, flyback power supplies are generally used 700V or 750V or 800-900V the switch. Like this circuit, overvoltage capability against a number of switching transformer reflected voltage can be done a bit higher, the maximum reflected voltage in the 150V is appropriate, to obtain better overall performance.TOP PI's recommendation for the 135V chipset with transient voltage suppression diode clamp. But his evaluation board generally reflected voltage to be lower than the value at around 110V. Both types have their advantages and disadvantages:Category: shortcomings against over-voltage, low duty cycle is small, a large pulse current transformer primary. Advantages: small transformer leakage inductance, electromagnetic radiation and low ripple index higher switch loss, the conversion efficiency is not necessarily lower than the second.The second category: a large number of shortcomings of power loss, a large number of transformer leakage inductance, the ripple worse. Advantages: Some strong against over-voltage, large duty cycle, lower transformer losses and efficiency higher.Reflected voltage flyback power supply and a determining factorReflected voltage flyback power supply with a parameter related to that is the output voltage, output voltage, the lower the larger the transformer turns ratio, the greater the transformer leakage inductance, switch to withstand higher voltage breakdown switch is possible to absorb power consumption is higher, has the potential to permanently absorb the circuit power device failure (particularly with transient voltage suppression diode circuits). In the design of low-voltage low-power flyback power output optimization process must be handled with care, its approach has several:1, using a large core of a power level lower leakage inductance, which can improve the low-voltage flyback power conversion efficiency, reduce losses, reduce output ripple and improve multi-output power of the cross regulation in general is common in household appliances with a switch power, such as CD-ROM drive, DVB set-top boxes.2, if the conditions were not increased core, can reduce the reflected voltage, reducing the duty cycle. Reduce the reflected voltage can reduce the leakage inductance but may reduce the power conversion efficiency, which is a contradiction between the two, must have an alternative process to find a suitable point, replace the transformer during the experiment can detect the transformer original side of the anti-peak voltage, peak voltage to minimize the anti-pulse width, and magnitude of the work safety margin increase converter. Generally reflected voltage 110V when appropriate.3, enhance the coupling, reducing losses, the introduction of new technologies, and the routing process, transformers to meet the security specifications will between the primary and secondary side to insulation measures, such as pad tape, plus side air insulation tape. These will affect the performance of transformer leakage inductance, the reality can be used in production around the primary winding secondary wrapping method. Or sub-system with a triple insulated wire wound to remove the insulation between the initial level, can enhance the coupling, even use wide copper winding.The article refers to low voltage output is less than or equal to 5V output, as this type of small power supply, my experience is that the power output of more than 20W output can use a forward, get the best value for money, of course, this is not the right decision , and personal habits, relationship between the application environment, the next time to talk about the flyback power supply with a magnetic core, magnetic circuit air gap opening some understanding, I hope you receive adequate guidance.Flyback power transformer core magnetization state at work in one way, it needs to open the air gap magnetic circuit, similar to the pulsating direct current sensor. Part of the magnetic coupling through the air gap. Why I understand the principle of open air gap as follows: As the power ferrite also has a similar rectangle of the operating characteristics (hysteresis loop), operating characteristics curve in the Y-axis magnetic induction (B), now the general production process saturation point in 400mT above, the general value in the design of this value should be more appropriate in the 200-300mT, X-axis magnetic field strength (H) the value of current intensity is proportional to the magnetization. Open magnetic circuit air gap equal to the magnetic hysteresis loop to the X axis tilt, in the same magnetic induction intensity, can withstand a greater magnetizing current, equivalent to core store more energy, this energy cut-off switch When spilled into the load through the transformer secondary circuit, flyback power core to open the air gap is twofold. One is to transfer more energy, and the second to prevent the core into saturation.Flyback Power Transformer magnetization state in one way, not only to pass through the magnetic coupling energy, is also responsible for input and output isolation voltage transform multiple roles. Therefore, the treatment gap need to be very careful, the air gap leakage inductance can become too large, increase the hysteresis loss, iron loss, copper loss increases, affecting the power of the whole performance. Air gap is too small has the potential to transformer core saturation, resulting in damage to powerThe so-called flyback power supply is continuous and discontinuous mode transformer working conditions, working in full load condition in the power transformer complete transfer, or incomplete transmission mode. General design of the working environment, conventional flyback power supply should work in continuous mode, this switch, circuit loss are relatively small, and can reduce the stress of work input and output capacitors, but that there are some exceptions.Requires in particular that: As the characteristics of the flyback power supply is also more suitable for design into a high-voltage power supply, and high-voltage power transformers generally work in discontinuous mode, I understand the need for as high voltage power supply output voltage of the rectifier diodes. Because of the manufacturing process characteristics, high-tension diode, reverse recovery time is long, low speed, the current continuous state, the diode has a positive bias in the recovery, reverse recovery energy loss is very large, is not conducive to converter performance increase, ranging from reduced conversion efficiency, rectifiers, severe fever, weight is even burnt rectifier. As in the intermittent mode, the diode is reverse biased under zero bias, loss can be reduced to a relatively low level. Therefore, high voltage power supply work in discontinuous mode, and the frequency can not be too high.Another type of flyback power supply work in the critical state, the general type of power supply work in FM, or FM-width-modulated dual-mode, a number of low-costself-excitation power (RCC) is often used this form in order to ensure stable output transformer As the operating frequency, output current or input voltage change, close to the fully loaded transformer is always maintained at between continuous and intermittent, this power is only suitable for small power output, otherwise the handling characteristics of electromagnetic compatibility will be a headacheFlyback switching power supply transformer should work in continuous mode, it required relatively large winding inductance, of course, is to some extent continuous, excessive pursuit of absolute continuity is not realistic, may need a great core, very much coil turns, accompanied by a large leakage inductance and distributed capacitance, worth the trouble. So how does this parameter to determine, through repeated practice, and analysis of peer design, I think, in the nominal voltage input, the output reached 50% and 60% transformer from intermittent, continuous state of transition to more appropriate. Or at thehighest input voltage state, the full output, the transformer can transition to the continuous state on it.开关电源状态，电源工作在高频率，高脉冲的模拟电路的一个比较特殊的一种。