Vol.30,No.2JournalofSemiconductorsFebruary2009AhighefficiencyPWMCMOSclass-Daudiopoweramplifier∗ZhuZhangming(朱樟明)1,†,LiuLianxi(刘帘曦)1,YangYintang(杨银堂)1,andLeiHan(雷晗)2(1InstituteofMicroelectronics,XidianUniversity,Xi’an710071,China)(2Xi’anPower-RailMicroCo.,Ltd,Xi’an710075,China)Abstract:Basedonthedifferenceclose-loopfeedbacktechniqueandthedifferencepre-amp,ahighefficiencyPWMCMOSclass-Daudiopoweramplifierisproposed.Arail-to-railPWMcomparatorwithwindowfunctionhasbeenembeddedintheclass-Daudiopoweramplifier.DesignresultsbasedontheCSMC0.5µmCMOSprocessshowthatthemaxefficiencyis90%,thePSRRis–75dB,thepowersupplyvoltagerangeis2.5–5.5V,theTHD+Nin1kHzinputfrequencyislessthan0.20%,thequiescentcurrentinnoloadis2.8mA,andtheshutdowncurrentis0.5µA.Theactiveareaoftheclass-Daudiopoweramplifierisabout1.47×1.52mm2.Withthegoodperformance,theclass-Daudiopoweramplifiercanbeappliedtoseveralaudiopowersystems.Keywords:class-Daudioamplifier;PWM;CMOS;highefficiency;rail-to-railcomparator;differenceDOI:10.1088/1674-4926/30/2/025001EEACC:1210;1220;12901.IntroductionConventionalclass-A,B,orABaudioamplifiersdirectlyamplifytheanalogsignalsandmustworkinthetriodere-gion.Althoughclass-ABaudioamplifiershavehighfidelity,theirpowerdissipationisobviousandconversionefficiencyisbelow50%,whichhardlysatisfytherequirementofenergy-saving.Somemethods(suchasemployingpush-pulloutputstage)areappliedtocompensateclass-ABamplifiers,butwhenthepowerishigh,powerdevicesarestillthreatenedandpoweroutputislimited,therebythepracticalconversioneffi-ciencyis30%–40%nomatterthatthetheoreticalvaluewouldbe78.5%,leadingtoaseriousenergywasteproblem.Atthesametimewemustincreasethechipareaorevenaddaplusradiatingflangefortheeliminationofheat,thustoomuchareaistakenandalsothecostisunaffordable.Ontheotherhand,class-DamplifiershavemanyadvantagesovertheclassA,B,orABmentionedabove,thecharacteristicworkingontheswitchingstatemakethetheoreticefficiencycouldbe100%,thepracticalvaluecouldbeover80%,andsopowerdissipa-tion,chipareaandareatakenbyPCBcouldbegreatlyre-duced.Sincepresentelectronicindustryaimsatsmallvolume,lowpowerandhighefficiency,class-Damplifiershaveabrightfuture[1−9].Atpresent,class-DaudiopoweramplifiershavealreadybeenusedinconsumerelectronicproductssuchasDVD,LCD-TV,MP4andcellphone.Comparedtotheconventionalclass-ABaudiopoweramplifier,itsgreatestadvantageisthehighefficiency,thepracticalefficiencywouldbeover80%,andthetheoreticalefficiencywouldbe100%.Intheclass-Daudiopoweramplifier,wecomparetheaudiosignalandhighfrequencyconstantsignal,thenmodulatethiscomparedresultusingtheconstantfrequencycarrierwaves,thusdigitalsignalisconvertedintoPWMsignal,whichisofchangeablepulsewidthandconstantcarrierfrequency(hundredskHzgener-ally).ThePWMsignalisamplifiedbyMOSFET,andtheam-plifiedPWMsignalcarrierfrequencyisremovedbyLClow-passfilter,therebytheoriginalbasebandaudiosignaldrivespeakerisobtained.Basedonthedifferenceclosed-loopfeedbacktechniqueandthedifferencepre-amp,ahighefficiencyPWMCMOSclass-Daudiopoweramplifierisproposed,andarail-to-railcomparatorwithwindowfunctionisproposedasPWMcom-parator.TheentirecircuitissimulatedandverifiedbasedonCSMC0.5µmCMOSprocess,andisprovedtobeofhighefficiencyandlowpowerconsumption.2.HighefficiencyPWMclass-Daudiopoweram-plifierSincethatsystemstabilityandnoisecharacteristicoftheclosedloopsystemaremuchbetterthan...