开关电源外文文献翻译 原文及译文.docx

开关电源外文文献翻译 原文及译文.docx

《开关电源外文文献翻译 原文及译文.docx》由会员分享，可在线阅读，更多相关《开关电源外文文献翻译 原文及译文.docx（15页珍藏版）》请在冰点文库上搜索。

开关电源外文文献翻译

（含：

英文原文及中文译文）

英文原文Switched-modepowersupply

Aswitched-modepowersupply（alsoswitching-modepowersupply,SMPS,orsimplyswitcher）isanelectronicpowersupplyunit（PSU）thatincorporatesaswitchingregulator.Whilealinearregulatormaintainsthedesiredoutputvoltagebydissipatingexcesspowerinapasspowertransistor,theswitched-modepowersupplyswitchesapowertransistorbetweensaturation（fullon）andcutoff（completelyoff）withavariabledutycyclewhoseaverageisthedesiredoutputvoltage.Itswitchesatamuch-higherfrequency（tenstohundredsofkHz）thanthatoftheACline（mains）,whichmeansthatthetransformerthatitfeedscanbemuchsmallerthanoneconnecteddirectlytotheline/mains.Switchingcreatesarectangularwaveformthattypicallygoestotheprimaryofthetransformer;typicallyseveralsecondariesfeedrectifiers,seriesinductors,andfiltercapacitorstoprovidevariousDCoutputswithlowripple.

Themainadvantageofthismethodisgreaterefficiencybecausetheswitching

transistordissipateslittlepowerinthesaturatedstateandtheoffstatecomparedtothesemiconductingstate（activeregion）.Otheradvantagesincludesmallersizeandlighterweight（fromtheeliminationoflowfrequencytransformerswhichhaveahighweight）andlowerheatgenerationduetohigherefficiency.Disadvantagesincludegreatercomplexity,thegenerationofhighamplitude,highfrequencyenergythatthelow-passfiltermustblocktoavoidelectromagneticinterference（EMI）,andaripplevoltageattheswitchingfrequencyandtheharmonicfrequenciesthereof.

Anoteaboutterminology

Althoughtheterm"powersupply"hasbeeninusesinceradioswerefirstpoweredfromtheline/mains,thatdoesnotmeanthatitisasourceofpower,inthesensethatabatteryprovidespower.Itissimplyadevicethat（usually）acceptscommercialACpowerandprovidesoneormoreDCoutputs.Itwouldbemorecorrectlyreferredtoasapowerconverter,butlongusagehasestablishedtheterm.Classification

SMPScanbeclassifiedintofourtypesaccordingtotheinputandoutputwaveforms:

ACin,DCout:

rectifier,off-lineconverterinputstage

DCin,DCout:

voltageconverter,orcurrentconverter,orDCtoDCconverter

ACin,ACout:

frequencychanger,cycloconverter,transformer

DCin,ACout:

inverter

Inputrectifierstage

IftheSMPShasanACinput,thenthefirststageistoconverttheinputtoDC.Thisiscalledrectification.Therectifiercircuitcanbeconfiguredasavoltagedoublerbytheadditionofaswitchoperatedeithermanuallyorautomatically.Thisisafeatureoflargersuppliestopermitoperationfromnominally120voltor240voltsupplies.TherectifierproducesanunregulatedDCvoltagewhichisthensenttoalargefiltercapacitor.ThecurrentdrawnfromthemainssupplybythisrectifiercircuitoccursinshortpulsesaroundtheACvoltagepeaks.Thesepulseshavesignificanthighfrequencyenergywhichreducesthepowerfactor.SpecialcontroltechniquescanbeemployedbythefollowingSMPStoforcetheaverageinputcurrenttofollowthesinusoidalshapeoftheACinputvoltagethusthedesignershouldtrycorrectingthepowerfactor.AnSMPSwithaDCinputdoesnotrequirethisstage.AnSMPSdesignedforACinputcanoftenberunfromaDCsupply（for230VACthiswouldbe330VDC）,astheDCpassesthroughtherectifierstageunchanged.It'showeveradvisabletoconsultthemanualbeforetryingthis,thoughmostsuppliesarequitecapableofsuchoperationeventhoughnothingismentionedinthedocumentation.However,thistypeofusemaybeharmfultotherectifierstageasitwillonlyutilizehalfofdiodesintherectifierforthefullload.Thismayresultinoverheatingofthesecomponents,andcausethemtofailprematurely.

Ifaninputrangeswitchisused,therectifierstageisusuallyconfiguredtooperateasavoltagedoublerwhenoperatingonthelowvoltage（~120VAC）rangeandasastraightrectifierwhenoperatingonthehighvoltage（~240VAC）range.Ifaninputrangeswitchisnotused,thenafull-waverectifierisusuallyusedandthedownstreaminverterstageissimplydesignedtobeflexibleenoughtoacceptthewiderangeofdcvoltagesthatwillbeproducedbytherectifierstage.Inhigher-powerSMPSs,someformofautomaticrangeswitchingmaybeused.

Inverterstage

TheinverterstageconvertsDC,whetherdirectlyfromtheinputorfromtherectifierstagedescribedabove,toACbyrunningitthroughapoweroscillator,whoseoutputtransformerisverysmallwithfewwindingsatafrequencyoftensorhundredsofkilohertz（kHz）.Thefrequencyisusuallychosentobeabove20kHz,tomakeitinaudibletohumans.Theoutputvoltageisopticallycoupledtotheinputandthusverytightlycontrolled.Theswitchingisimplementedasamultistage（toachievehighgain）MOSFETamplifier.MOSFETsareatypeoftransistorwithalowon-resistanceandahighcurrent-handlingcapacity.Sinceonlythelaststagehasalargedutycycle,previousstagescanbeimplementedbybipolartransistorsleadingtoroughlythesameefficiency.Thesecondlaststageneedstobeofacomplementarydesign,whereonetransistorchargesthelastMOSFETandanotheronedischargestheMOSFET.Adesignusingaresistorwouldrunidlemostofthetimeandreduceefficiency.Allearlierstagesdonotweightintoefficiencybecausepowerdecreasesbyafactorof10foreverystage（goingbackwards）andthustheearlierstagesareresponsibleforatmost1%oftheefficiency.ThissectionreferstotheblockmarkedChopperintheblockdiagram.

Voltageconverterandoutputrectifier

Iftheoutputisrequiredtobeisolatedfromtheinput,asisusuallythecaseinmainspowersupplies,theinvertedACisusedtodrivetheprimarywindingofahigh-frequencytransformer.Thisconvertsthevoltageupordowntotherequiredoutputlevelonitssecondarywinding.Theoutputtransformerintheblockdiagramservesthispurpose.

IfaDCoutputisrequired,theACoutputfromthetransformerisrectified.Foroutputvoltagesabovetenvoltsorso,ordinarysilicondiodesarecommonlyused.Forlowervoltages,Schottkydiodesarecommonlyusedastherectifierelements;theyhavetheadvantagesoffasterrecoverytimesthansilicondiodes（allowinglow-lossoperationathigherfrequencies）andalowervoltagedropwhenconducting.Forevenloweroutputvoltages,MOSFETsmaybeusedassynchronousrectifiers;comparedtoSchottkydiodes,thesehaveevenlowerconductingstatevoltagedrops.

Therectifiedoutputisthensmoothedbyafilterconsistingofinductorsandcapacitors.Forhigherswitchingfrequencies,componentswithlowercapacitanceandinductanceareneeded.

Simpler,non-isolatedpowersuppliescontainaninductorinsteadofatransformer.Thistypeincludesboostconverters,buckconverters,andthesocalledbuck-boostconverters.Thesebelongtothesimplestclassofsingleinput,singleoutputconverterswhichutilizeoneinductorandoneactiveswitch.Thebuckconverterreducestheinputvoltageindirectproportiontotheratioofconductivetimetothetotalswitchingperiod,calledthedutycycle.Forexampleanidealbuckconverterwitha10Vinputoperatingata50%dutycyclewillproduceanaverageoutputvoltageof5V.Afeedbackcontrolloopisemployedtoregulatetheoutputvoltagebyvaryingthedutycycletocompensateforvariationsininputvoltage.Theoutputvoltageofaboostconverterisalwaysgreaterthantheinputvoltageandthebuck-boostoutputvoltageisinvertedbutcanbegreaterthan,equalto,orlessthanthemagnitudeofitsinputvoltage.Therearemanyvariationsandextensionstothisclassofconvertersbutthesethreeformthebasisofalmostallisolatedandnon-isolatedDCtoDCconverters.Byaddingasecondinductorthe?

ukandSEPICconverterscanbeimplemented,or,byaddingadditionalactiveswitches,variousbridgeconverterscanberealised.

OthertypesofSMPSsuseacapacitor-diodevoltagemultiplierinsteadofinductorsandtransformers.Thesearemostlyusedforgeneratinghighvoltagesatlowcurrents（Cockcroft-Waltongenerator）.Thelowvoltagevariantiscalledchargepump.

Regulation

Afeedbackcircuitmonitorstheoutputvoltageandcomparesitwithareferencevoltage,whichissetmanuallyorelectronicallytothedesiredoutput.Ifthereisanerrorintheoutputvoltage,thefeedbackcircuitcompensatesbyadjustingthetimingwithwhichtheMOSFETsareswitchedonandoff.Thispartofthepowersupplyiscalledtheswitchingregulator.TheChoppercontrollershownintheblockdiagramservesthispurpose.Dependingondesign/safetyrequirements,thecontrollermayormaynotcontainanisolationmechanism（suchasopto-couplers）toisolateitfromtheDCoutput.Switchingsuppliesincomputers,TVsandVCRshavetheseopto-couplerstotightlycontroltheoutputvoltage.

Open-loopregulatorsdonothaveafeedbackcircuit.Instead,theyrelyonfeedingaconstantvoltagetotheinputofthetransformerorinductor,andassumethattheoutputwillbecorrect.Regulateddesignscompensatefortheparasiticcapacitanceofthetransformerorcoil.Monopolardesignsalsocompensateforthemagnetichysteresisofthecore.

Thefeedbackcircuitneedspowertorunbeforeitcangeneratepower,soanadditionalnon-switchingpower-supplyforstand-byisadded.

Transformerdesign

SMPStransformersrunathighfrequency.Mostofthecostsavings（andspacesavings）inoff-linepowersuppliescomefromthefactthatahighfrequencytransformerismuchsmallerthanthe50/60Hztransformersformerlyused.

Thereareseveraldifferencesinthedesignoftransformersfor50Hzvs500kHz.Firstlyalowfrequencytransformerusuallytransfersenergythr