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1、外文翻译外文文献Switched-modepowersupplyAswitched-modepowersupply(alsoswitching-modepowersupply,SMPS,orsimplyswitcher)isanelectronicpowersupplyunit(PSU)thatincorporatesaswitchingregulator.Whilealinearregulatormaintainsthedesiredoutputvoltagebydissipatingexcesspowerinapasspowertransistor,the
2、switched-modepowersupplyswitchesapowertransistorbetweensaturation(fullon)andcutoff(completelyoff)withavariabledutycyclewhoseaverageisthedesiredoutputvoltage.Itswitchesatamuch-higherfrequency(tenstohundredsofkHz)thanthatoftheACline(mains),whichmeansthatthetransformerthatitfeedscanbem
3、uchsmallerthanoneconnecteddirectlytotheline/mains.Switchingcreatesarectangularwaveformthattypicallygoestotheprimaryofthetransformer;typicallyseveralsecondariesfeedrectifiers,seriesinductors,andfiltercapacitorstoprovidevariousDCoutputswithlowripple.Themainadvantageofthismethodisgreat
4、erefficiencybecausetheswitchingtransistordissipateslittlepowerinthesaturatedstateandtheoffstatecomparedtothesemiconductingstate(activeregion).Otheradvantagesincludesmallersizeandlighterweight(fromtheeliminationoflowfrequencytransformerswhichhaveahighweight)andlowerheatgenerationduet
5、ohigherefficiency.Disadvantagesincludegreatercomplexity,thegenerationofhighamplitude,highfrequencyenergythatthelow-passfiltermustblocktoavoidelectromagneticinterference(EMI),andaripplevoltageattheswitchingfrequencyandtheharmonicfrequenciesthereof.AnoteaboutterminologyAlthoughtheterm
6、"powersupply"hasbeeninusesinceradioswerefirstpoweredfromtheline/mains,thatdoesnotmeanthatitisasourceofpower,inthesensethatabatteryprovidespower.Itissimplyadevicethat(usually)acceptscommercialACpowerandprovidesoneormoreDCoutputs.Itwouldbemorecorrectlyreferredtoasapowerconverter,butlo
7、ngusagehasestablishedtheterm.ClassificationSMPScanbeclassifiedintofourtypesaccordingtotheinputandoutputwaveforms:ACin,DCout:rectifier,off-lineconverterinputstageDCin,DCout:voltageconverter,orcurrentconverter,orDCtoDCconverter11外文翻译ACin,ACout:frequencychanger,cycloconverter,transform
8、erDCin,ACout:invert
