开关电源拓扑结构详述.ppt

1、Power Supply Topologies电源拓扑结构,AMOI 家用系统设计部,Power Supply Topologies电源拓扑结构,AMOI 家用系统设计部,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 Cuk,Details of the Circuit Operatio电路工作的细节,The Basic

2、 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：,占空比=负荷比,Buck降压,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

3、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。,负载,Boost升压,Boosts the input to a higher voltage.

4、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 (choppe

5、d).输出电流不连续 (斩波)。,负载,Buck-Boost 降压-升压,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

6、 (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。,负载,Flyback 反激,Operates

7、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

8、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。,负载,Forward正激,The transformer-cou

9、pled 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

10、 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

11、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。,负载,复位,Two-Transistor Forward双晶体管正激,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,

12、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。,负载,Push-Pull推挽,The switches (FETs) are driven out of phase and pulse-width modulated (PWM) to re

13、gulate 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

14、 twice the input voltage.施加在FET上的电压是输入电压的两倍。,负载,Half-Bridge半桥,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 utili

15、zation-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 inp

16、ut voltage.施加在FET 上的电压与输入电压相等。,负载,Most popular topology for high-power converters.较高功率变换器最为常用的拓扑结构。 The switches (FETs) are driven in diagonal pairs and pulse-width modulated (PWM) to regulate the output voltage.开关（FET）以对角对的形式驱动，进行脉冲宽度调制（PWM）以调节输出电压。 Good transformer core utilization-power is transf

17、erred 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; 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 FETs上的电压与输入电压相等。 For a given power, primary current is half that of the half-bridg

18、e.在给定的功率下，初级电流是半桥的一半。,负载,Full-Bridge全桥,SEPIC (Single-Ended Primary Inductor Converter) （单端初级电感变换器）,Output voltage can be either less than or greater than the input.输出电压可以大于或小于输入电压。 Like the boost, the input current is smooth and output current is not.与升压电路一样，输入电流平滑，但是输出电流不连续。 Energy is transferred f

19、rom input to output through a capacitor.能量通过电容从输入传输至输出。 Requires two inductors.需要两个电感。,负载,Cuk (By Slobodan Cuk) (Slobodan Cuk的专利),Output is inverted.输出反相。 Magnitude of output voltage can be less or greater than the input.输出电压的幅度可以大于或小于输入。 Input current and output current are both smooth.输入电流和输出电流都是平

20、滑的。 Energy is transferred from input to output through a capacitor.能量通过电容从输入传输至输出。 Requires two inductors.需要两个电感。 Inductors can be coupled to achieve zero-ripple inductor current.电感可以耦合获得零纹波电感电流。,负载,Details of the Circuit Operation电路工作的细节,Buck regulator:降压调整器： Continuous conduction连续导电 Critical cond

21、uction临界导电 Discontinuous conduction不连续导电 Boost regulator (continuous conduction)升压调整器 (连续导电) Transformer operation变压器工作 Flyback transformer反激变压器 Forward transformer正激变压器,Inductor current is continuous.电感电流连续。 Vout is the average of the voltage at its input (V1).Vout 是其输入电压 (V1)的均值。 Output voltage is

22、 the input voltage times the duty ratio (D) of the switch.输出电压为输入电压乘以开关的负荷比 (D)。 When switch in on, inductor current flows from the battery.接通时，电感电流从电池流出。 When switch is off, it flows through the diode.开关断开时电流流过二极管。 Neglecting losses in the switches and inductor, D is independent of load current.忽略开

23、关和电感中的损耗, D与负载电流无关。 A characteristic of buck regulators and its derivatives: 降压调整器和其派生电路的特征是： Input current is discontinuous (chopped), and output current is continuous (smooth).输入电流不连续 (斩波), 输出电流连续 (平滑)。,Buck Regulator降压调整器 (Continuous Conduction)(连续导电),负载,时间,Inductor current is still continuous, b

24、ut just “touches” zero as the switch turns on again.电感电流仍然是连续的，只是当开关再次接通时 “达到”零。 This is called “critical conduction.”这被称为 “临界导电”。 Output voltage is still equal to the input voltage times D.输出电压仍等于输入电压乘以D。,Buck Regulator降压调整器 (Critical Conduction)(临界导电),负载,时间,Buck Regulator降压调整器 (Discontinuous Condu

25、ction)（不连续导电）,In this case, the current in the inductor is zero during part of each period.在这种情况下，电感中的电流在每个周期的一段时间中为零。 Output voltage is still (as always) the average of v1.输出电压仍然 (始终)是 v1的平均值。 Output voltage is NOT the input voltage times the duty ratio (D) of the switch.输出电压不是输入电压乘以开关的负荷比 (D)。 Whi

26、le the load current is below the critical value, D varies with load current (while Vout remains constant).当负载电流低于临界值时，D 随着负载电流而变化 (而 Vout 保持不变)。,负载,时间,Boost Regulator升压调整器,Output voltage is always greater than (or equal to) the input voltage.输出电压始终大于（或等于）输入电压。 Input current is continuous, and output

27、 current is discontinuous (the opposite of a buck regulator).输入电流连续，输出电流不连续（与降压调整器相反）。 Relationship of the output voltage to the duty ratio, D, is not as simple as in the buck regulator. In the continuous-conduction case, it is:输出电压与负荷比（D）之间的关系不如在降压调整器中那么简单。在连续导电的情况下：,In this example, Vin = 5,在本例中，V

28、in = 5, Vout = 15, and D = 2/3.Vout = 15，D = 2/3.,负载,时间,Transformer Operation变压器工作 Including Effect of Primary Inductance包括初级电感的作用,Transformer is shown as an ideal transformer, with its primary (magnetizing) inductance as an inductor in parallel with the primary.变压器看作理想变压器，它的初级（磁化）电感与初级并联。,负载,匝数比：,时

29、间,Flyback Transformer反激变压器 (Really a Multi-Winding Inductor)（实际是多绕组电感）,Here, the primary inductance is intentionally low, to determine the peak current and hence the stored energy. When the primary switch is turned off, the energy is delivered to the secondary.此处初级电感很低，用于确定峰值电流和存储的能量。当初级开关断开时，能量传送到次级。,负载,匝数比：,时间,Forward