《功率因数校正开关电源的研究与设计》外文翻译

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1、《功率因数校正开关电源的研究与设计》外文翻译SwitchingPowerSupplyDesign(开关电源设计)CHAPTER3Half-andFull-BridgeConverterTopologies3.1IntroductionHalf-bridgeandfull-bridgetopologiesstresstheirtransistorstoavoltageequaltotheDCinputvoltagenottotwicethisvalue,asdothepush-pull,single-ended,andinterleavedforwardconverte

2、rtopologies.Thusthebridgetopologiesareusedmainlyinofflineconverterswheresupplyvoltagewouldbemorethantheswitchingtransistorscouldsafelytolerate.BridgetopologiesarealmostalwaysusedwherethenormalACinputvoltageis220Vorhigher,andfrequentlyevenfor120-VACinputs.Anadditionalvaluablefeatureofthe

3、bridgetopologiesisthatprimaryleakageinductancespikes(Figures2.1and2.10)areeasilyclampedtotheDCsupplybusandtheenergystoredintheleakageinductanceisreturnedtotheinputinsteadofhavingtobedissipatedinaresistivesnub-berelement.3.2Half-BridgeConverterTopology3.2.1BasicOperationHalf-bridgeconver

4、tertopologyisshowninFigure3.1.Itsmajoradvantageisthat,likethedouble-endedforwardconverter,itsubjectsthe“off”transistortoonlyVdcandnottwicethatvalue.ThusitiswidelyusedinequipmentintendedfortheEuropeanmarket,wheretheACinputvoltageis220V.FirstconsidertheinputrectifierandfilterinFigure3.1.I

5、tisuseduniversallywhentheequipmentistoworkfromeither120-VACAmericanpoweror220-VACEuropeanpower.Thecircuitalwaysyieldsroughly320-VrectifiedDCvoltage,whethertheinputis120orFIGURE3.1Half-bridgeconverter.OneendofthepowertransformerprimaryisconnectedtothejunctionoffiltercapacitorsC1,C2viaasm

6、allDClockingcapacitorCb.TheotherendisconnectedtothejunctionofQ1,Q2,whichturn“on”and“off”onalternatehalfcycles.WithS1intheclosedposition,thecircuitisavoltagedoubler;intheopenposition,itisafull-waverectifier.Ineithercase,therectifiedoutputisabout308to336Vdc.220VAC.ItdoesthiswhenswitchS1is

7、settotheopenpositionfor220-VACinput,ortotheclosedpositionfor120-VACinput.TheS1componentisnormallynotaswitch;moreoftenitisawirelinkthatiseitherinstalledfor120VAC,ornotfor220VAC.Withtheswitchintheopen220-VACpositionthecircuitisafullwaverectifier,withfiltercapacitorsC1andC2inserie