开关电源拓扑结构详解.pdf

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1、安森美半导体PowerSupplyTopologies电源拓扑结构TheMostPopularTopologies最常见的拓扑结构BuckPush-Pull降压推挽BoostHalfBridge升压半桥Buck-BoostFullBridge降压-升压全桥FlybackSEPIC反激C’ukForward正激Two-TransistorForward双晶体管正激DetailsoftheCircuitOperatio电路工作的细节TheBasicPulse-WidthModulatedWaveform基本的脉冲宽度调制波形Thesetopologi

2、esallrelatetoswitched-modecircuits.这些拓扑结构都与开关式电路有关。Definitionofthebasicpulse-widthmodulatedwaveformisasfollows:基本的脉冲宽度调制波形定义如下：TTONOFFTSTTONONDutyCycle=DutyRatio=D==TTT占空比=负荷比ONOFFSTTOFFOFFD'=1-D==TTTONOFFSBuck降压VinVoutLoad负载(R)Vout=DVinBuckstheinputdowntoalowervoltage.把输入降至一

3、个较低的电压。Perhapsthesimplestofall.可能是最简单的电路。Theinductor/capacitorfilteraveragestherectangularwavefromtheswitch.电感/电容滤波器滤平开关后的方波。Outputisalwayslessthanorequaltotheinput.输出总是小于或等于输入。Inputcurrentisdiscontinuous(chopped).输入电流不连续(斩波)。Outputcurrentissmooth.输出电流平滑。Boost升压VinVoutLoad负载(

4、R)1Vout=VinD'Booststheinputtoahighervoltage.把输入升至一个较高的电压。Likethebuck,butinductor,switchanddiodearerearranged.与降压一样，但重新安排了电感、开关和二极管。Outputisalwaysgreaterthanorequaltotheinput.输出总是比大于或等于输入。–(neglectingtheforwardvoltagedropofthediode).(忽略二极管的正向压降)。Inputcurrentissmooth.输入电流平滑。Out

5、putcurrentisdiscontinuous(chopped).输出电流不连续(斩波)。Buck-BoostVin降压-升压VoutLoad负载(R)-DVout=VinD'Anotherarrangementoftheinductor,switchanddiode.电感、开关和二极管的另一种安排方法。Combinesnegativecharacteristicsofboththebuckandtheboost.结合了降压和升压电路的缺点。–Inputcurrentisdiscontinuous(chopped).输入电流不连续(斩波)。–

6、Outputcurrentisalsodiscontinuous(chopped).输出电流也不连续(斩波)。Outputisalwaysinvertedfromtheinput(notecapacitorpolarity),butcanbeoflessorgreatermagnitude.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”converterisactuallyanisolated(transformercoupled)versionofthebuck-boost.“反激”变换器实际是降压-

7、升压电路隔离（变压器耦合）形式。Flyback反激VoutVinn1Load(R)负载DVout=VinnD'Operateslikethebuck-boost,buttheinductorhastwowindingsandperformsbothasatransformerandinductor.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。–Outputcanbeeitherpositiveornegative,dependingonthepolarityofthewindinganddiode.输出可以为正或为负，

8、由线圈和二极管的极性决定。–Outputvoltagecanbeeitherlessthanorgreaterthantheinputv