感应加热器教程 3kw

感应加热器教程 3kwInduction Heater TutorialAn induction heater is an interesting device, allowing one to rapidly 迅速的 heat a metal object. With enough power, one can even甚至 melt 熔化 metal. The induction heater works without the need for fossil化石 fuels, and can anneal退火 and heat objects of various各种各样 shapes 形状. I set out to make an induction heater that could melt steel and aluminum. So far迄今为止 I have been able to feed an input power of over 3 kilowatts! Now that I have done this I would like to share how it works, and how you can build one. At the end of the tutorial I will discuss 论述 and show you how to build a levitation coil that will allow you to boil煮沸 metals while suspended in mid air! 一台感应加热器是一台有趣的设备,可以迅速加热金属工件.功率够高时,可以融化金属.感应加热器不需要石化燃料,可以对工件退火处理,还可以加热各种形状的工件.我制造了一台可以融化钢和铝的感应加热器.现在功率已经达到了3千瓦!我来教你怎么造一台.在教程的最后,我将教你造一个可以在半空中融化金属的磁悬浮加热线圈. My induction heater is an inverter. An inverter takes a DC power source and converts it into AC power. The AC power drives a transformer which is coupled耦合 to a series LC tank. The inverter frequency is set to the tank's resonant共振 frequency, allowing the generation of very (high currents高安培电流) within the tank's coil. The coil is coupled to the workpiece工件 and sets up (eddy currents涡电流). These currents, traveling through a conductive, but slightly微小 resistive电阻的workpiece, heat the piece. Remember, Power = Heat = R*I^2. The workpiece is like a one-turn coil; the work coils has several数个 turns圈. Thus 这样, we have a (step-down transformer降压器), so even higher currents are generated in the workpiece.这样电流就流进工件里去了. 我的感应加热器有一个逆变器.逆变器可以把直流电转换为交流电.交流电被变压器耦合到感应线圈和电容组一起组成的振荡器上.逆变器的工作频率决定振荡器的振荡频率.振荡器的感应线圈会感应出非常大的电流.感应线圈又将这些电流产生的磁场耦合到工件上产生涡流电.工件中的电阻,阻碍涡流电的流动,导致工件发热.(详细原理参照变压器中的涡流电).记住,功率=热=R乘以I的平方.工件可以看成一个只有一圈的线圈,而感应线圈有多个线圈,这样一来就可以把感应线圈和工件看成一个变压器回路,工件的电压低,电流就从感应线圈流向工件去了.I would like to acknowledge鸣谢 the invaluable无法估计的 help from John Dearmond and Tim Williams for helping me understand this topic话题. Now, before we talk more, let's see some pictures of what it can do. 谢谢 John Dearmond 和 Tim William大量的帮助,帮我弄明白这个话题.先来看几张图.Later, I will give a link to a video showing it running. Here is the inverter. 下图是逆变器:What I will now do is go over each part. Then, I will give the schematics 电路图, go over them and how you can build this device. 我将介绍每一个部分.然后给出电路图.然后你就明白怎么造了.Induction Heater Components 感应加热器的组成部分We will talk about each component部分( making up组成) the induction heater. First, there is the workcoil. This is what heats the workpiece. The workcoil will get very hot from the high current going through it and the radiation of heat from the workpiece. 我们将讨论感应加热器的零件话题.首先是感应线圈, 它有高压电流,被加热的工件会将热回传到感应线圈上. The workcoil is attached to the LC tank. This can either be a series or parallel (resonant tank谐振回路). The tank and coil need to be cool, so I implemented a plumbing水管装置-type design that allows me to pump water through the coil using a fountain喷水 pump. 感应线圈与电容组组成振荡器.它可以是串联振荡器也可以是并联振荡器.我搞了个泵抽水来冷却电容组和感应线圈. The resonant tank is coupled to the power source with a (coupling transformer耦合变压器). The transformer is connected to the inverter. 谐振回路靠耦合变压器来与逆变器相连. The inverter chops the DC power source at a particular特定的 frequency. This is the (resonant frequency 谐振频率) of the tank. Now, as the workpiece heats and goes through its (curie point居里温度点) - the temperature when the metal is no longer ferromagnetic - the resonant frequency changes. The inverter needs to stay locked on as closely as possible to the current resonant frequency to achieve获得 the fullest power. Some will do this manually手动, using an oscilloscope示波器 to monitor the waveforms, or using a voltmeter伏特计 on the tank and tuning the frequency to the highest tank voltage. Another method is using a phase locked loop (PLL) to monitor the (phase relationship相位关系) of the inverter voltage and tank voltage. This is the method I use and I will discuss论述 this in detail later on. 逆变器将直流电转换成交流电的频率是振荡器的谐振频率.工件温度升高并穿过居里点,本身特有磁性消失,会改变振荡器的谐振频率.逆变器必须将直交流变换频率锁定在当前振荡器的谐振频率以获得最大功率.这项工作可以手工进行,用示波器和电压表对振荡器的波形和电压调整来调谐振荡频率以获得振荡器最大工作电压.另一种方法是用锁相环通过相位关系来控制逆变器和振荡器的电压.这种方法等会儿说. Let's start with how to easily make a workcoil. We will be using frequencies in the 10s to 100s of kilohertz (kHz), so metals will conduct传导 the current only slightly (below the surface深入). This is the (skin effect趋肤效应). The current depth深度 in mm is 先来做个感应线圈.频率范围10khz~100khz.电流透入工件的深度有趋肤效应用下式计算. Depth (mm) = 76/√(F) 深度(毫米)=76除以根号(频率) So, the wider the tubing, the lower the resistance. We also want to use tubing so we can water-cool the coil. I purchased购买 some refrigerator水箱 3/8" copper tubing from Home Depot. You will also need some 1/2" copper pipe and the necessary fittings配件 so you can feed water through one end,have it circulate循环 through the coil, and come out the other end. Ihave (brass fittings黄酮配件) with nipples接头 so I can attach some tubing to my fountain pump, and a return tube to my ice water bath. 大铜管小电阻.铜管可以水冷.我从五金商店买了些3/8''的铜管.你还要买些1/2''的铜管,和铜接头,把它们焊在一起连上泵,就能让水循环了. This is the tubing I got from Home Depot. 铜管.LC Tank: (Polypropylene Film Capacitor Bank聚丙烯薄膜电容器组) 振荡器The induction heater uses a workcoil as a step-down transformer. This transformer steps the voltage down, but increases增大 the available可用的 current to the workpiece, which is the one-turn coil that completes the transformer. The (magnetic flux磁通量) is coupled to our workpiece. The better the coupling, the more efficient效率高的 is our workcoil. The closer the workpiece is to the coil the better the energy transfer. 感应线圈是个变压器,工件的电压低,电流都往工件跑,工件是个一圈的感应线圈,电流以电磁的形式耦合到工件.好的耦合,高的效率,就是我们的线圈.工件与线圈越近能量传送效率越高. This is the workcoil and tank. The capacitors are high voltage metallized power film snubbers. 下面是线圈,还有这些电容器是高压金属化薄膜功率缓冲器.The workcoil is made from shaping the 3/8" copper tubing. I use brass compression fittings to attach it to the LC tank. The tank is made fromtwo 1" x 3/16" thick厚 copper bars. I drill holes in the bars to accommodate容纳 the capacitors. We need a capacitor that can handle several hundreds of amps安培 of current. I purchased购买 some (pulse capacitors脉冲电容) with (current ratings现行定额) of 14A, 3000vdc, 750vac. With 20 capacitors this is close to 300A average平均 current. The coupling transformer (fits over安上) the copper tubing. If you look closely, you will see the fountain pump submerged淹没的 in water. This pumps ice water through the tank and back out into the bucket. Water flows in from the bottom left, through the copper pipe soldered to the bus bar, through the coil, over the bank to the upper left, and through the tubing connected to the other bus bar, and out on theupper right. You should also take note where the workcoil connects with the capacitor bank. (It does not connect both leads at the front end; instead不是连结每个头在最前端), the coil connects to (opposite ends相反一头的前端). This ensures确保 that the capacitors share an equal 相等 (current load海量电流). Otherwise否则, if both end connected to the front, the capacitors closest to the coil would handle the brunt冲击力 of current because the resistance would be the least. When you are dealing with hundreds of amps, small changes in R are significant重要的. 用3/8''的铜管做线圈.用铜接头把它和电容组连接.电容组用两条1X3/16''厚的铜板固定.铜板上打了洞来放电容.我们需要能通过数安培电流的电容.我买了些高压脉冲电容,参数是14A,3000VDC,750AC.20个电容,这样就差不多能承载300A电流.耦合变压器安在铜管上.近看,泵在水里.泵把水泵过电容组和铜管,水再回到水桶里.水从左下进,右上出.你要注意线圈怎么和电容组连接的.线圈和电容组是不对称连接的,看上图.有耦合变压器(黑陀陀)的那条铜管,它是转了个弯才和线圈连接的.这样做是为了保护靠近线圈的电容,可以使电流平均的承栽到电容上.如电容不迂回连接,靠近线圈的电容的电阻最小,会过流大电流而烧毁.当你使用数百安培的电流时,你得注意电阻稍微改变的后果.These are the bars with the holes drilled in them. The tank uses 20capacitors, but you can use any number that gives you the capacitance and current handling capacity that you require. 打了洞的铜条.可以安20个电容.,你可以自行决定电容的数量,和电流大小.First, you need to determine决定 what operating工作的 frequency you will use. Higher frequencies have greater skin effect (less penetration穿透) and are good for smaller objects. Lower frequencies are better for larger objects and have greater penetration. Higher frequencies have greater (switching losses开关损耗), but there is less current going through the tank. I choose a frequency near 70khz and wound up with about 66khz. My capacitor bank is 4.4uf and can handle over 300A. My coil is near 1uH. The capacitors are from Illinois Capacitors. Mine are0.22uf/3000vdc. The model number is 224PPA302KS. 你先得决定机器的工作频率.高频率对工件的穿透能力低适合加工小物件.低频率相反.高频率有大的开关损耗.但穿过电容组的电流小.我选择70KHZ到66KHZ之间.我的电容组的电容量是4.4微法可以通300多安电流.我的线圈的电感量是1微亨.电容的生产厂是Illinois Capacitors.每个的参数都是0.22uf/3000vdc.型号是224PPA302KS. Fres = 1/2π√(LC) 频率=1除2乘以派乘以根号(电感量乘以电容量) Once you wind卷绕 your coil you can get an idea of its value by making a simple RLC circuit with it and connect it to a (function generator 函数信号发生器) and scope. I used a 1R resistor and a 500pf capacitor.I increased增强 my function generator sine wave and measured the voltage across R(R两端的电压). At resonance the LC (impedance drops阻抗降) and the voltage drop across R peaks达到峰值. This gave me a ballpark大致正确的 figure计算, but you can just go by the calculation估计. 线圈的电感量可以用简单的RLC电路,联上函数信号发生器来确定.我用1欧电阻和500皮法电容.我增强函数信号发生器发出的正弦波然后量电阻两端的电压降.谐振时LC的阻抗变低,R两端电压变(可能高也可能低,得看怎么连接了). Now, as far as the workcoil goes you can form the workcoil by driving a piece of PVC tubing into the ground. I used a 1" pipe (1.5" OD).( Take the copper tubing and fill it with sand or salt在铜管里装满沙或者盐). Make sure it is completely filled填满的. This way it will act like a solid实心的 tube and will not collapse塌陷 when you bend弯曲 it. Fix one end with something like a heavy vice and work the tubing around your PVC tube until you have your desired渴望的 number of turns. Four to five turns at 1.5-2" will give you a coil with an inductance感应系数 between 0.8 - 1.3 uH. 用PVC管来饶线圈,把一根1.5''外径( outer diameter)的PVC管插在地上.在铜管里装满沙或盐.确定填满.实心的铜管绕时不会扁.把铜管绕在PVC管上,你想绕几圈就绕几圈.绕4~5圈就可以有0.8~1.3微亨的电感量.You can see how nicely令人满意的 the coil forms around the pipe. Once you are happy with the turns and shape you can blow the sand out with an air compressor.你可以绕个你爱的线圈.绕好后把沙或盐用压缩机吹出来.Power Supply: Voltage double and regulated source 电源:倍压和稳压电源I need to talk about two power supplies for the unit. One is the high voltage DC that the inverter converts to AC for feeding the tank. You need an unregulated未调制的, smoothed平滑 source. You can use 110vac througha rectifier整流器 and smoothed with a 1000uf-1500uf capacitor for a supply of 170vdc. I used a (voltage multiplier倍压器) to convert it to 320vdc. Below are some basic schematics for a (voltage doubler倍压器).I used the third variation变种 for mine. Make sure you have your rectifier on a large (heat sink散热片) because it will be conducting a lot of amperes. My rectifier is rated for 25A/500vac. 给逆变器供电,我用第三张图的,整流器要求25A/500VAC.电容1000~1500微法.第三张图的过程是,整流,倍压,再到逆变器.The second power supply you will need will be a 15vdc regulated控制 source. It is imperitive that it is regulated because the PLL has a (voltage controlled oscillator压控振荡器). The VCO determines the output frequency based on input voltage it receives. The frequency range it can generate is based on its supply voltage, Vss. If the supply voltage wanders 迷失, the oscillator frequency will wander and this will definitely肯定的 throw you out of resonance. 给锁相环供电,要求可以控制电压的电源,最大15伏.锁相环的输出频率是基与输入电压的.频率变化范围是基于电源电压的,如果电源电压错乱,振荡频率肯定也错乱.RCL Theory理论 and (Transformer Coupling耦合) RCL理论和变压器耦合I guess the best way to understand what is going on is to start with the wor kcoil and work backwards. Remember from earlier I said that the workcoil is the (primary end初级的一端) of a step-down transformer. We have hundreds of amps flowing through here and this creates产生 a voltage in the workpiece. We achieve获得 these high currents because the RCL tank is at resonance. This means that the (inductive reactance感抗) and (capacitive reactance容抗)( cancel out抵消), and all we are left with is the small, real resistance. 解析加热线圈的工作的背后的原理.我说过工件和加热线圈组成一个变压器回路,加热线圈看成是初级,工件是次级,电流流过初级,次级产生感应电压.RCL在谐振时我们获得大电流.前一句的意思是感抗容抗抵消,只剩电阻的阻值无法抵消. Below we have a RCL circuit with a resistance of 4R, Zl = 4ohms and Cl = 3ohms. The reactive反应 impedance 阻抗 cancels抵消 to 1ohm, giving us a phase shift of 18degrees leading. The inductor wins and the inductor voltage leads the current. There is only one current running through the series circuit. You can also say the inductor voltage leads the voltage across the resistor, because the voltage and current of the resistor are (in phase同相). Remember, the voltage drop across an inductor is a reaction反作用力 against抵抗 a change in current through it. The( instantaneous voltage瞬时电压) is zero when the current is at a peak because the change in current is zero, (manifested by the zero slope表现在零坡度). 下图表示一个RCL电路,电阻4欧,感抗4欧,容抗3欧.电路启动后阻抗抵消,剩1欧,得到一个相位超前18度角的波.电感的感抗没和容抗抵消完,导致电感的电压的波的相位超前电流的波的相位.这里只有一种电流.你可以说电感的电压的波的相位超前电阻两端的电压的波的相位.电阻的电压和电流的波的相位是同相.电感因为电磁感应的一些原因,它两端的电压会阻碍交流电流穿过.当电流达到最大值时,顺时电压为0,因为电流还未变化.下图的部分表示前一句话的图解.If the inductive and capacitive reactance cancel out the phase shift is zero. The current in the circuit is in phase with the voltage. 电感的电抗和电容的电抗抵消,电流与电压的波的相位是同相.Now here is an important point. The maximum power transfer传输 will occur 发生 when the current is in phase with the voltage. 上图意思电流和电压的波同相位,得到最大功率. So, at resonance, the current in the series circuit is in phase with the voltage source. If we are out of resonance( the current phase is shifted from zero with respect to the voltage电流相位和电压相位将错开). If there is more inductive reactance the (currentlags the voltage电流相位滞后于电压相位); if there is more capacitive reactance the (current leads the voltage电流相位超前于电压相位). You can also say the capacitor voltage lags the current. 在串联电路里,谐振时电流和电压源的波的相位相同.如果失谐,电流的波的相位和电压的波的相位将错开.感抗多,电流的波的相位滞后与电压的.容抗多,电流的波的相位超前与电压的.你可以直接说电容电压滞后与电流. What is the voltage source for the series tank It is our (coupling transformer耦合变压器). I am experimenting with different materials and turns圈数, but right now I am using an iron powered core from Amidon Corp made from Type 3 material. This material is good from frequencies between 0.05Mhz and 0.5Mhz. I used two toroids环形的. Each is 2.25" in diameter直径 and 0.565" thick. I wound 14g wire around for 20-26 turns. I am still trying to (figure out 弄明白) the optimum最适宜的 turns and the best material. The( lower the turns减少圈数) the( greater greater the exciting voltage励磁电压越大) to the tank. However, magnetization current goes up as does the load on the inverter逆变器开始负载电磁流. 给振荡器供电的是谁呢是耦合变压器.我用不同的材料和不同的线圈圈数实验耦合变压器,我现在用的是Amidon Corp 的3型铁芯磁环.支持的频率是0.05MHZ~0.5MHZ.我用两个每个直径2.25''厚度0.565''.我用14号(gauge)规格的电线绕20~26圈.我试了很多次才确定绕线的圈数和铁芯材料.减少偶合变压器饶线的圈数,到振荡器的感应电压越大.不管怎么样,逆变器开始工作了. Below are the two toroids. I use two to (prevent saturation防止饱和). I wonder how three would do 下图两磁环.我用两个是为防止饱和.不知用三个怎么样.Here I have wound 14g wire around. The transformer does not impart告知 (a phase shift if place on the tank correctly相移在磁环上恰当). If you (flip it around胡绕) you will introduce a 180 degree shift which will prevent 阻止the PLL from locking onto the frequency. Just turn it around. Which way is the right way Use the right-hand rule. 我用14号线绕.不能胡绕,胡绕锁相环就失控了.那该怎么绕呢用右手法则.Here is a solenoid螺线管 with the current flowing in the direction shown. Put your right thumb拇指 in the direction of the current and your fingers curl卷曲 in the direction of the B field(假装右手拿了一个透明玻璃杯的样子,不包括拇指). The field outside of the coil is not important to us; the field inside the solenoid sums to one large field going from right to left. If we had a metal bar or part of the toroid圆的's arc弧形物inside, the field场 would travel through it. 下图红色箭头是电流,黑线是电线,右手拇指指向红色箭头的方向,其他四指半弯曲,指向头上有小箭头的字母B.电磁场就从你的手掌穿过,电流的方向是拇指指的方向,磁场的方向是其它四指指的方向.So here is a (mock-up教学模型) of the coupling transformer. The current travels to the (positive terminal正极) of our toroid环形 transformer output. Using the right hand rule we can realize实现 the direction of the B field for each turn. The black arrow on the toroid shows the direction the field travels in the core. Using the right-hand rule again we see that the current travels through the copper tubing from left to right towards 朝 the positive terminal of our RLC tank. We will use this as the positive 正极 lead for monitoring our tank capacitor voltage later. If you are unsure which end is which you can wind卷绕 a few turns of wire as a secondary and scope区分范围 the ends如果你不确定是哪一端,你可以随便卷绕几圈来确定是哪一端. The voltages in and out should be in phase. 下图是一个耦合变压器的简单模型.图中黑色的电线,电流就是打+号(正极)流过黑电线绕成的线圈,从-号(负级)流出.现在我们知道了电流方向,用右手定则来确定磁场方向,图中白环上有一个黑箭头,那就是磁场方向,磁场在磁环的肚子里.图中黄灿灿的铜管会感应到耦合变压器产生的磁场,而产生感应电压,电流又会从+到-.流过铜管流到振荡线圈.Oscilloscope Tracings追踪示波The inverter outputs a drive voltage to the coupling transformer. The current in is in phase with the current out. When the tank is at resonance, the tank current is in phase with the drive current of the coupling transformer, and is in phase with the inverter input voltage. If anything, you want the current to slightly lag the voltage because the mosfets 金属氧化物半导体场效应晶体管 behave表现 better when facing an inductive感应的, (rather than a capacitive而不是一个电容), load. This has to do with the mosfets conducting in the (reverse direction反向). The tracing below is clean and allows me to reach到达 very high power levels while maintaining relatively cool mosfets同时保持相对的冷. 逆变器输出一个驱动电压到耦合变压器.电流全程同相.当振荡器谐振,振荡器电流和耦合变压器电流同相还有逆变器输入电压.如果你想电流滞后电压,那么场效应管比电容效果好,特别是在感抗高的时候.上机.场效应管用反向导通.下图显示没有杂波,我可以用大功,率场效应管还不烫.Now, if the tanks (is above超出...之外) resonance we have more inductive reactance. The tank's net current will lag the (driving voltage励磁电压) from the coupling transformer. Since the input and output current of the coupling transformer are in phase, the tank's current is lagging the inverter driving voltage. Below you can see the dominating inductive reactance results in the inverter current (trianglelooking wave) is almost 90 degrees lagging the inverter voltage (square wave). 如果高于谐振频率,感抗变大.振荡器的电流滞后于耦合变压器传来的感应电压.由于耦合变压器的输入输出电流同相,振荡器的电流也滞后于逆变器的电压.下图,感抗高的结果是逆变器电流(三角波)差不多滞后逆变器电压90度角(方波).If we are below低于 the resonant frequency capacitive reactance results in the current leading the inverter voltage. Also, there is ringing振铃波 in the current waveform and at the inverter voltage transitions. This noise gets worse with higher power levels and can result in mosfet failure. 低于谐振频率,容抗变大,结果电流超前逆变器电压.下图有些振铃波在电流波形和逆变器电压波形上.这些噪声在大功率时更糟,还会使场效应管损坏.I would like just mention提及 that the inductive waveforms is really an (exponential curve指数). If we can approximate近似的 the tank above resonant as a RL circuit (responding to回答) a (step response阶跃响应) 我还想提一下,电感性波形是一个指数曲线.我们可以RL电路响应跃阶响应来模拟振荡器谐振.The solution解答 toOscilloscope Tracings II 示波 IILet's continue our discussion讨论 of oscilloscope tracings so we can better understand how the inverter is going to work and lock onto resonance. From the last page I mentioned提及 that voltage across the tank capacitor lags the current by 90 degrees. At resonance, the tank current has a zero phase shift with respect to source (inverter) tank voltage because the inductive and capacitive reactance cancel out. If you display the invertervoltage and capacitor voltage together, you can see the sinusoidal正弦曲线 capacitor voltage lags the inverter voltage by 90 degrees. The square wave is the inverter voltage, but you would get the same relationship关联 if you scoped the voltage output of the toroid transformer. 继续弄明白逆变器和锁相环怎么工作.上页说到振荡器的电容电压滞后电流90度.谐振时振荡器电流与逆变器和振荡器自己的电压是同相.下图,如果你把逆变器电压和电容电压放在一起观察,电容电压波是正弦曲线,滞后逆变器电压90度.方波是逆变器电压,你监测耦合变压器的输出电压,就可以得到一些关联.We will monitor this relationship. We are at resonance when our PLL chip keeps Vc ninety90 degrees lagging behind Vinverter. Now, we can easily exceed超过 the chips maximum input voltage, so we need to clip修剪 the top and the bottom the capacitor voltage, and keep it to a maximum of 15v. We do this with some clamping钳位 diodes二极管 yeilding捕获 this waveform, which will be the signalin input on pin 14 of the HEF4046锁相环芯片. 我们来看这些联系.谐振时锁相环保持电容电压滞后于逆变器电压90度.这样很容易超过锁相环芯片的输入电压,我们需要电容电压维持在最大15V,我们用钳位2极管钳位电容的波的电压,再输入进HEF4046的第14脚.Below is a diagram图解 of the scoped voltages. Using a (differential probe差分探头), the positive lead goes to the positive inverter lead going to the toroid and the negative to the negative lead. Using a second differential probe we scope区分 the + and - ends端 of the capacitor tank. Vc will lag Vinv or Vtank. We will have to invert使反转 the Vc waveform, that is shift it 180 degrees, (in order合乎程序的) for the PLL to work, which I will discuss shortly. 下图解释监测电压.用差分探头,正极插到逆变器和耦合变压器正极之间,负极到负极.第2个差分探头到电容,我们得注意电容的正负极.VC滞后VINV或VTANK.我们反转VC的波形,相移180度,进锁相环工作.Now, we are ready to talk about the phase locked loop chip - the HEF4046. After this discussion, we will have enough information to understand the workings of the inverter and how it maintains保持 a lock on the resonance. 该说锁相环HEF4046了.说完锁相环还有逆变器如何维持谐振.Phase Locked Loop (PLL) Basics基本原理锁相环的基本原理When you read about induction heaters and inverters you will probably (come across遇到) the term术语 phase locked loop. The people writing the tutorials will assume假装 you know all about these. I will make the opposite assumption and give you a brief understanding of the concept so you can understand how this will help maintain resonance with our induction heater.我将作出相反的假设,并给您一个简单的概念,以便你能理解这将如何帮助我们维持感应加热器的振荡. 一个你可能不清楚的术语,锁相环.别的教程都假装你懂.我将作出相反的假设,并给您一个简单的概念,以便你能理解这将如何帮助我们维持感应加热器的振荡. A PLL (consists of由...组成) three parts: a voltage controlled oscillator (VCO), a (loop filter环路滤波器LPF) and a (phase detector鉴相器PD). The VCOout drives the device, or (inverter gate反向门) in our case. It also closes the loop by feeding itself back into the phase detector so it can get (compared with与...相比) a (reference signal参考信号). PPL由3部分组成:压控振荡器VCO.环路滤波器.鉴相器.VCOout用来驱动某些设备或反向门.下图,VCO用个环来将输入输出信号进行比较.The VCO generates a 50% (duty cycle占空因数) square wave; the frequency depends on the input voltage to the VCO. The higher the VCOinput (pin 9) voltage the higher the VCOoutput frequency; the lower the voltage the lower the frequency. The PLL phase detector compares the phases of two inputs: the reference signal on pin 14 and the VCOout frequency. The phase detector has two options for outputs: PCA1 and PCA2. We use the former 前者, which is a XOR异或 gate. VCO发出50%占空比的方波,频率由输入电压决定.VCO的第9脚如果输入高电压,VCO的输出频率就高,反之输出频率低.PD比较相位用两个脚,参考信号在14脚,和VCOOUT脚输出频率.PD还有2个选项PCA1和PCA2.我门用前者异或门.The logic is high if one of the two inputs is high; otherwise it is low. It will generate a square wave (whose width is based on其宽度是根据) the (phase difference相位差) of the two signals. If the two waves are 90 degrees out of phase the (average value平均值) of Vphi is Vdd/2. The loop filter takes the phase detector output and converts this to the input voltage to the VCO. The simplest filter is a RC low-pass filter. The (cut-off frequency截至频率) will determine判定 how sensitive the PLL is to phase changes, and how well it stays locked on the reference signal. 异或门,输入两个信号,其中一个高,输出就高,如果不是,输出都低.我将产生一个方波,脉宽根据相位差决定.如果被比较的两个波相位差90度,(PD)比较后的电压VPHI差不多是芯片的工作电压VDD的2分之1.LPF又将VPHI转换成一个输入电压到VCO,兼输出.LPF是一个RC低通滤波器.截止频率将判断PPL相位什么时候改变,什么时候锁住谐振信号. So what happens At resonance the tank current is real and in phase with the coupler transformer voltage, which is in phase with the inverter voltage. The tank capacitor voltage lags the tank current by 90 degrees; therefore由此得出, it lags the inverter voltage by 90 degrees. Now as the workpiece heats its ferromagnetic铁磁体 properties性质 change. The workcoil becomes变成 a (variable inductor可变电感线圈) and affects影响 the resonant frequency of the tank. If the effective事实上的 resonance goes down, it seems好像 to the circuit that we increased增强 on drive frequency to the tank. This makes the tank more inductive. Inductance causes the source voltage lead the tank current. That is, the tank current is forced to lag the inverter voltage. The capacitor voltage initially lagged the current by 90 degrees. This means the capacitor voltage lags the inverter voltage even more as shown below.这意味着电容电压滞后于逆变器电压更甚,如下所示. 谐振时,振荡器的电流和耦合变压器的电压同相,还有逆变器的电压.振荡器的电容电压滞后于振荡器电流90度.由此看来,它也落后逆变器电压90度.工件受热后,它的铁磁性质发生了改变.加热线圈成了一个可变电感线圈.这种变化影响了振荡器的谐振频率.如果振荡器停机,可能是我们的电路给振荡器提高了频率..电感变大了.会导致振荡器电流强制滞后于逆变器电压.电容电压开始就滞后于电流90度.这意味着电容电压滞后于逆变器电压更甚,如下所示.Below we can see the relationships关系 with Vinv, Vcap and Vphi. Vphi is high Vinv or Vcap is high, but not both. 下面是VINV逆变器电压,VCAP 电容电压,VPHI(PD)比较后的电压,的关系.vphi高,VINV或VCAP就高,但不是同时三个一起高.。