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1、外文翻译外文文献Switched-modepowersupplyAswitched-modepowersupply(alsoswitching-modepowersupply,SMPS,orsimplyswitcher)isanelectronicpowersupplyunit(PSU)thatincorporatesaswitchingregulator.Whilealinearregulatormaintainsthedesiredoutputvoltagebydissipatingexcesspowerina
2、passpowertransistor,theswitched-modepowersupplyswitchesapowertransistorbetweensaturation(fullon)andcutoff(completelyoff)withavariabledutycyclewhoseaverageisthedesiredoutputvoltage.Itswitchesatamuch-higherfrequency(tenstohundredsofkHz)thanthatoftheACline(mains)
3、,whichmeansthatthetransformerthatitfeedscanbemuchsmallerthanoneconnecteddirectlytotheline/mains.Switchingcreatesarectangularwaveformthattypicallygoestotheprimaryofthetransformer;typicallyseveralsecondariesfeedrectifiers,seriesinductors,andfiltercapacitorstopro
4、videvariousDCoutputswithlowripple.Themainadvantageofthismethodisgreaterefficiencybecausetheswitchingtransistordissipateslittlepowerinthesaturatedstateandtheoffstatecomparedtothesemiconductingstate(activeregion).Otheradvantagesincludesmallersizeandlighterweight
5、(fromtheeliminationoflowfrequencytransformerswhichhaveahighweight)andlowerheatgenerationduetohigherefficiency.Disadvantagesincludegreatercomplexity,thegenerationofhighamplitude,highfrequencyenergythatthelow-passfiltermustblocktoavoidelectromagneticinterference
6、(EMI),andaripplevoltageattheswitchingfrequencyandtheharmonicfrequenciesthereof.AnoteaboutterminologyAlthoughtheterm"powersupply"hasbeeninusesinceradioswerefirstpoweredfromtheline/mains,thatdoesnotmeanthatitisasourceofpower,inthesensethatabatteryprovidespower.I
7、tissimplyadevicethat(usually)acceptscommercialACpowerandprovidesoneormoreDCoutputs.Itwouldbemorecorrectlyreferredtoasapowerconverter,butlongusagehasestablishedtheterm.ClassificationSMPScanbeclassifiedintofourtypesaccordingtotheinputandoutputwaveforms:ACin,DCou
8、t:rectifier,off-lineconverterinputstageDCin,DCout:voltageconverter,orcurrentconverter,orDCtoDCconverter11外文翻译ACin,ACout:frequencychanger,cycloconverter,transformerDCin,ACout:invert
