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1、外文翻译外文文献Switched-modepowersupplyAswitched-modepowersupply(alsoswitching-modepowersupply,SMPS,orsimplyswitcher)isanelectronicpowersupplyunit(PSU)thatincorporatesaswitchingregulator.Whilealinearregulatormaintainsthedesiredoutputvoltagebydissipatingexce
2、sspowerinapasspowertransistor,theswitched-modepowersupplyswitchesapowertransistorbetweensaturation(fullon)andcutoff(completelyoff)withavariabledutycyclewhoseaverageisthedesiredoutputvoltage.Itswitchesatamuch-higherfrequency(tenstohundredsofkHz)thanth
3、atoftheACline(mains),whichmeansthatthetransformerthatitfeedscanbemuchsmallerthanoneconnecteddirectlytotheline/mains.Switchingcreatesarectangularwaveformthattypicallygoestotheprimaryofthetransformer;typicallyseveralsecondariesfeedrectifiers,seriesindu
4、ctors,andfiltercapacitorstoprovidevariousDCoutputswithlowripple.Themainadvantageofthismethodisgreaterefficiencybecausetheswitchingtransistordissipateslittlepowerinthesaturatedstateandtheoffstatecomparedtothesemiconductingstate(activeregion).Otheradva
5、ntagesincludesmallersizeandlighterweight(fromtheeliminationoflowfrequencytransformerswhichhaveahighweight)andlowerheatgenerationduetohigherefficiency.Disadvantagesincludegreatercomplexity,thegenerationofhighamplitude,highfrequencyenergythatthelow-pas
6、sfiltermustblocktoavoidelectromagneticinterference(EMI),andaripplevoltageattheswitchingfrequencyandtheharmonicfrequenciesthereof.AnoteaboutterminologyAlthoughtheterm"powersupply"hasbeeninusesinceradioswerefirstpoweredfromtheline/mains,thatdoesnotmean
7、thatitisasourceofpower,inthesensethatabatteryprovidespower.Itissimplyadevicethat(usually)acceptscommercialACpowerandprovidesoneormoreDCoutputs.Itwouldbemorecorrectlyreferredtoasapowerconverter,butlongusagehasestablishedtheterm.ClassificationSMPScanbe
8、classifiedintofourtypesaccordingtotheinputandoutputwaveforms:ACin,DCout:rectifier,off-lineconverterinputstageDCin,DCout:voltageconverter,orcurrentconverter,orDCtoDCconverter11外文翻译ACin,ACout:frequencychanger,cycloconverter,transformerDCin,ACout:invert
