开关电源拓扑结构详解

Vin
Boost 升压
Vout Load 负载 (R)
D' Boosts the input to a higher voltage. 把输入升至一个较高的电压。 Like the buck, but inductor, switch and diode are rearranged. 与降压一样，但重新安排了电感、开关和二极管。 Output is always greater than or equal to the input. 输出总是比大于或等于输入。 – (neglecting the forward voltage drop of the diode). ( 忽略二极管的正向压降 ) 。 Input current is smooth. 输入电流平滑。 Output current is discontinuous (chopped). 输出电流不连续 ( 斩波 ) 。
TON
TOFF TS
Duty Cycle = Duty Ratio = D = TON 占空比 = 负荷比 D' = 1 - D = TOFF TON TOFF =
TON TOFF TOFF TS
=
TON TS
Buck 降压
Vin Vout Load 负载 (R)
Vout = D Vin
Bucks the input down to a lower voltage. 把输入降至一个较低的电压。 Perhaps the simplest of all. 可能是最简单的电路。 The inductor/capacitor filter averages the rectangular wave from the switch. 电感 / 电容滤波器滤平开关后的方波。 Output is always less than or equal to the input. 输出总是小于或等于输入。 Input current is discontinuous (chopped). 输入电流不连续 ( 斩波 ) 。 Output current is smooth. 输出电流平滑。
Forward 正激
Vin i1
Vout Load (R)
n
1
负载
iRESET 复位
m
Vout =
D n
Vin
The transformer-coupled version of the buck. 降压电路的变压器耦合形式。 – Discontinuous input current; smooth output current. 不连续的输入电流，平滑的输出电流。 Because of the transformer, the output can be less or greater than the input and of either polarity. 因为采用变压器，输出可以大于或小于输入，可以是任何极性。 Multiple outputs are possible be adding secondary windings and circuits. 增加次级绕组和电路可以获得多个输出。 The transformer core must be reset during each switching cycle. A popular way to do this is to add another winding with the same number of turns as the primary. 在每个开关周期中必须对变压器磁芯去磁。常用的做法是增加一个与初级绕组匝数相同的绕组。 – Energy stored in the primary inductance during the “on” time of the switch is discharged through the extra winding and diode during the “off” time. 在开关接通阶段存储在初级电感中的能量，在开关断开阶段通过另外的绕组和二极管释放。
Vout =
1
Vin
Vin
Buck-Boost 降压 - 升压
Vout Load 负载 (R)
Vout =
Another arrangement of the inductor, switch and diode. 电感、开关和二极管的另一种安排方法。 Combines negative characteristics of both the buck and the boost. 结合了降压和升压电路的缺点。 – Input current is discontinuous (chopped). 输入电流不连续 ( 斩波 ) 。 – Output current is also discontinuous (chopped). 输出电流也不连续 ( 斩波 ) 。 Output is always inverted from the input (note capacitor polarity), but can be of less or greater magnitude. 输出总是与输入反向 ( 注意电容的极性 ) ，但是幅度可以小于或大于输入。 The “flyback” converter is actually an isolated (transformer coupled) version of the buck-boost. “ 反激”变换器实际是降压 - 升压电路隔离（变压器耦合）形式。
ຫໍສະໝຸດ Baidu
Vin
Full-Bridge 全桥
Vout
1 n 1 Vout = D n Vin
Vin
Half-Bridge 半桥
Vout
1 n 1 Vout = D Vin 2n
Load 负载 (R)
Very popular topology for higher-power converters. 较高功率变换器极为常用的拓扑结构。 The switches (FETs) are driven out of phase and pulse-width modulated (PWM) to regulate the output voltage. 开关（ FET ）的驱动不同相，进行脉冲宽度调制（ PWM ）以调节输出电压。 Good transformer core utilization---power is transferred on both half-cycles. And---primary winding utilization is better than push-pull. 良好的变压器磁芯利用率 --- 在两个半周期中都传输功率。而且初级绕组的利用率优于推挽电路。 Full-wave topology; output ripple frequency is twice the transformer frequency. 全波拓扑结构 , 所以输出纹波频率是变压器频率的两倍。 Voltage stress on the FETs is equal to the input voltage. 施加在 FET 上的电压与输入电压相等。
Details of the Circuit Operatio 电路工作的细节
The Basic Pulse-Width Modulated Waveform 基本的脉冲宽度调制波形
These topologies all relate to switched-mode circuits. 这些拓扑结构都与开关式电路有关。 Definition of the basic pulse-width modulated waveform is as follows: 基本的脉冲宽度调制波形定义如下：
Vin
Two-Transistor Forward 双晶体管正激
Vout Load (R)
负载
Vout =
D n
Vin
The two switches operate simultaneously. 两个开关同时工作。 When they turn off, the energy stored in the transformer reverses the polarity of the primary, causing the diodes to conduct. 开关断开时，存储在变压器中的能量使初级的极性反向，使二极管导通。 Major advantages: 主要优点： – The voltage on each switch never exceeds the input voltage. 每个开关上的电压永远不会超过输入电压。 – No reset winding is needed. 无需对绕组磁道复位。
安 森 美 半 导 体
Power Supply Topologies 电源拓扑结构
The Most Popular Topologies 最常见的拓扑结构
Buck 降压 Boost 升压 Buck-Boost 降压 - 升压 Flyback 反激 Forward 正激 Two-Transistor Forward 双晶体管正激 Push-Pull 推挽 Half Bridge 半桥 Full Bridge 全桥 SEPIC C’uk
Push-Pull 推挽
Vout
n
Vin
1 1 Vout = D n Vin
Load 负载 (R)
n
The switches (FETs) are driven out of phase and pulse-width modulated (PWM) to regulate the output voltage. 开关（ FET ）的驱动不同相，进行脉冲宽度调制（ PWM ）以调节输出电压。 Good transformer core utilization---power is transferred on both half-cycles. 良好的变压器磁芯利用率 --- 在两个半周期中都传输功率。 Full-wave topology, so output ripple frequency is twice the transformer frequency. 全波拓扑结构 , 所以输出纹波频率是变压器频率的两倍。 Voltage stress on the FETs is twice the input voltage. 施加在 FET 上的电压是输入电压的两倍。
-D Vin D'
Flyback 反激
Vin
Vout Load (R)
n
1
负载
Vout =
D n D'
Vin
Operates like the buck-boost, but the inductor has two windings and performs both as a transformer and inductor. 如降压 - 升压电路一样工作，但是电感有两个绕组，而且同时作为变压器和电感。 – Output can be either positive or negative, depending on the polarity of the winding and diode. 输出可以为正或为负，由线圈和二极管的极性决定。 – Output voltage can be either less than or greater than the input voltage, depending on the turns ratio of the transformer. 输出电压可以大于或小于输入电压，由变压器的匝数比决定。 This is the simplest of the isolated topologies. 这是隔离拓扑结构中最简单的。 Multiple outputs are possible with additional secondary windings and circuits. 增加次级绕组和电路可以得到多个输出。