开关电源基础之拓朴结构.

WelcometoH&T开关电源基础之PowerSupplyTopologies电源拓扑结构企业愿景：做令人尊敬的企业企业精神：敏锐敏捷，认同认真技术方针：把握先导技术，占有核心技术，转化实用技术经营方针：稳健专注，守正出奇TheMostPopularTopologies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Push-Pull推挽HalfBridge半桥FullBridge全桥SEPICC’uk软开关拓扑LLC与有源钳位DetailsoftheCircuitOperatio电路工作的细节TheBasicPulse-WidthModulatedWaveform基本的脉冲宽度调制波形Thesetopologiesallrelatetoswitched-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：TSTONTOFFD'=1-D=TONTOFFTOFFTOFFTS=DutyCycle=DutyRatio=D=TONTSTONTONTOFF=Buck降压Buckstheinputdowntoalowervoltage.把输入降至一个较低的电压。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。Load(R)VinVoutVout=VinD负载Boost升压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。Outputcurrentisdiscontinuous(chopped).输出电流不连续(斩波)。Load(R)VinVout1Vout=VinD'负载Buck-Boost降压-升压Anotherarrangementoftheinductor,switchanddiode.电感、开关和二极管的另一种安排方法。Combinescharacteristicsofboththebuckandtheboost.结合了降压和升压电路的特点。–Inputcurrentisdiscontinuous(chopped).输入电流不连续(斩波)。–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-升压电路隔离（变压器耦合）形式。Load(R)VinVoutVout=VinD'-D负载Flyback反激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，由线圈和二极管的极性决定。–Outputvoltagecanbeeitherlessthanorgreaterthantheinputvoltage,dependingontheturnsratioofthetransformer.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。Thisisthesimplestoftheisolatedtopologies.这是隔离拓扑结构中最简单的。Multipleoutputsarepossiblewithadditionalsecondarywindingsandcircuits.增加次级绕组和电路可以得到多个输出。Load(R)VinVoutVout=VinDnD'n1负载Forward正激Thetransformer-coupledversionofthebuck.降压电路的变压器耦合形式。–Discontinuousinputcurrent;smoothoutputcurrent.不连续的输入电流，平滑的输出电流。Becauseofthetransformer,theoutputcanbelessorgreaterthantheinputandofeitherpolarity.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。Multipleoutputsarepossiblebeaddingsecondarywindingsandcircuits.增加次级绕组和电路可以获得多个输出。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。–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。i1Load(R)VinVoutiRESETVout=VinDnn1m负载复位Two-TransistorForward双晶体管正激Thetwoswitchesoperatesimultaneously.两个开关同时工作。Whentheyturnoff,theenergystoredinthetransformerreversesthepolarityoftheprimary,causingthediodestoconduct.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。Majoradvantages:主要优点：–Thevoltageoneachswitchneverexceedstheinputvoltage.每个开关上的电压永远不会超过输入电压。–Noresetwindingisneeded.无需绕组复位。Load(R)VinVoutVout=VinDn负载Push-Pull推挽Theswitches(FETs)aredrivenoutofphaseandpulse-widthmodulated(PWM)toregulatetheoutputvoltage.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。Goodtransformercoreutilization---poweristransferredonbothhalf-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-wavetopology,sooutputripplefrequencyistwicethetransformerfrequency.全波拓扑结构,所以输出纹波频率是变压器频率的两倍。VoltagestressontheFETsistwicetheinputvoltage.施加在FET上的电压是输入电压的两倍。Load(R)VinVoutVout=VinDnnn11负载Half-Bridge半桥Verypopulartopologyforhigher-powerconverters.较高功率变换器极为常用的拓扑结构。Theswitches(FETs)aredrivenoutofphaseandpulse-widthmodulated(PWM)toregulatetheoutputvoltage.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。Goodtransformercoreutilization---poweristransferredonbothhalf-cycles.And---primarywindingutilizationisbetterthanpush-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-wavetopology;outputripplefrequencyistwicethetransformerfrequency.全波拓扑结构,所以输出纹波频率是变压器频率的两倍。VoltagestressontheFETsisequaltotheinputvoltage.施加在FET上的电压与输入电压相等。Load(R)VinVoutVout=VinD2nn11负载Mostpopulartopologyforhigh-powerconverters.较高功率变换器最为常用的拓扑结构。Theswitches(FETs)aredrivenindiagonalpairsandpulse-widthmodulated(PWM)toregulatetheoutputvoltage.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。Goodtransformercoreutilization---poweristransferredonbothhalf-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-wavetopology;outputripplefrequencyistwicethetransformerfrequency.全波拓扑结构，所以输出纹波频率是变压器频率的两倍。VoltagestressontheFETsisequaltotheinputvoltage.施加在FETs上的电压与输入电压相等。Foragivenpower,primarycurrentishalfthatofthehalf-bridge.在给定的功率下，初级电流是半桥的一半。Load(R)VinVoutVout=VinDn11n负载Full-Bridge全桥SEPIC(Single-EndedPrimaryInductorConverter)（单端初级电感变换器）Outputvoltagecanbeeitherlessthanorgreaterthantheinput.输出电压可以大于或小于输入电压。Liketheboost,theinputcurrentissmoothandoutputcurrentisnot.与升压电路一样，输入电流平滑，但是输出电流不连续。Energyistransferredfrominputtooutputthroughacapacitor.能量通过电容从输入传输至输出。Requirestwoinductors.需要两个电感。Load(R)VinVoutVout=VinD'D负载C’uk(BySlobodanC’uk)(SlobodanC’uk的专利)Outputisinverted.输出反相