Abstract—A rigorous mathematical analysis and a comparative study of carrier-frequency modulation (CFM) techniques for the conducted electromagnetic interference (EMI) suppression in pulsewidth-modulated converters is presented. CFM techniques dither the

TSEetal.:CARRIER-FREQUENCYMODULATIONTECHNIQUESbeendeveloped.Inaddition,duetothefinitebandwidthoftheresolutionfilterinEMCanalyzers,discrepanciesbetweenthetheoreticalandexperimentalresultshavebeenexplained.SelectionsofthemodulationfrequencyandthefrequencydeviationinPCFMhavebeendiscussed.Finally,theoreticalpredictionsareconfirmedbyexperimentalresultsofabuckconverteroperatingincontinuousconductionmode.

REFERENCES

[1]M.D.Heerema,“Designingforelectromagneticcompatibility,”inProc.

Hewlett-PackardSeminar,1996,pp.1–29.

[2]H.Chung,S.Y.R.Hui,andK.K.Tse,“Reductionofpowerconverter

EMIemissionusingsoft-switchingtechnique,”pat.,vol.40,pp.282–287,Aug.1998.

[3]F.LinandD.Y.Chen,“ReductionofpowersupplyEMIemissionby

switchingfrequencymodulation,”IEEETrans.PowerElectron.,vol.9,pp.132–137,Jan.1994.

[4]T.G.HabetlerandD.M.Divan,“Acousticnoisereductioninsinusoidal

PWMdrivesusingarandomlymodulatedcarrier,”IEEETrans.PowerElectron.,vol.6,pp.356–363,July1991.

[5]A.M.Stankovic,G.C.Verghese,andD.J.Perreault,“Analysisandsyn-thesisofrandomisedmodulationschemesforpowerconverters,”IEEETrans.PowerElectron.,vol.10,pp.680–693,Nov.1995.

[6]K.K.Tse,H.Chung,S.Y.R.Hui,andH.C.So,“Acomparativeinvesti-gationontheuseofrandommodulationschemesfordc/dcconverters,”IEEETrans.Ind.Electron.,vol.47,pp.245–252,Apr.2000.

[7]D.StoneandB.Chambers,“Theeffectsofcarrierfrequencymodulation

ofPWMwaveformsonconductedEMCproblemsinswitchedmodepowersupplies,”EPEJ.,vol.5,no.3/4,pp.32–37,Jan.1996.

[8]M.Bech,F.Blaabjerg,andJ.Pederson,“Randommodulationtechniques

withfixedswitchingfrequencyforthree-phasepowerconverters,”IEEETrans.PowerElectron.,vol.15,pp.753–761,July2000.

[9]C.R.WylieandL.C.Barrett,AdvancedEngineeringMathe-matics.NewYork:McGraw-Hill,1995.

[10]A.B.Carlson,CommunicationSystems:AnIntroductiontoSignaland

NoiseinElectricalCommunication.NewYork:McGraw-Hill,1986.[11]G.Kennedy,ElectronicCommunicationSystems.NewYork:Mc-Graw-Hill,1985.

[12]R.A.Witte,SpectrumandNetworkMeasurements.EnglewoodCliffs,

NJ:Prentice-Hall,1991.

[13]HP8590EMSeriesUser’sGuide,HewlettPackardCo.,PaloAlto,CA,

1995.

K.K.Tse(M’00)receivedtheB.Eng.(Hons.)degreeinelectricalengineeringfromTheHongKongPoly-technicUniversity,HongKong,andthePh.D.degreefromCityUniversityofHongKong,HongKong,in1995and2000,respectively.

HeservedasaLecturerattheHongKongInstituteofVocationalEducation(TsingYi)(formerlyTech-nicalCollege)in1998.From1999to2001,hewasaResearchFellowintheElectronicEngineeringDe-partment,CityUniversityofHongKong.SinceJune2001,hehasbeenwithJohnsonElectric,HongKong,

whereheiscurrentlyaTechnicalSpecialistintheR&Darea.Hehasauthoredmorethan20publishedtechnicalpapersintheareasofhisresearchinterests,whichincludenewnumericalmodelmethodsandcomputer-aidedsimulationtechniques,EMIreductionusingrandomswitchingschemesfordc–dccon-verters,andnewmaximumpowertrackingtechniquesforPVcells.

Dr.TsereceivedtheFirstPrizein1998intheIEEEPostgraduateStudentPaperContest,HongKongSection,andtheThirdPrizeinthe1999Region10IEEEPostgraduateStudentPaperContest.HewasarecipientofTheCroucherFoundationFellowshipin2000.InDecember2000,hereceivedtheSilverAwardintheYoungInventorCompetition,jointlyorganizedbytheFarEasternEconomicReviewandHewlettPackard

Company.

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HenryShu-HungChung(S’92–M’95)receivedtheB.Eng.(withfirstclasshonors)degreeinelectricalengineeringandthePh.D.degreefromTheHongKongPolytechnicUniversity,HongKong,in1991and1994,respectively.

Since1995,hehasbeenwithCityUniversityofHongKong,HongKong,whereheiscurrentlyanAssociateProfessorintheDepartmentofElectronicEngineering.Hisresearchinterestsincludetime-andfrequency-domainanalysisofpowerelectroniccir-cuits,switched-capacitor-basedconverters,random-switchingtechniques,digitalaudioamplifiers,soft-switchingconverters,andelectronicballastdesign.Hehasauthoredfourresearchbookchaptersandmorethan130technicalpapers,including65refereedjournalpapersinthecurrentre-searcharea,andistheholderoftwoU.S.patents.

Dr.ChungiscurrentlytheIEEEStudentBranchCounseloratCityUniversityofHongKongandwasTrackChairoftheTechnicalCommitteeonPowerElec-tronicsCircuitsandPowerSystemsoftheIEEECircuitsandSystemsSocietyin1997–1998.HeispresentlyanAssociateEditoroftheIEEETRANSACTIONSONCIRCUITSANDSYSTEMSI.HewasawardedtheGrandAppliedResearchEx-cellenceAwardin2001fromCityUniversityofHong

Kong.

S.Y.RonHui(SM’94)wasborninHongKongin1961.HereceivedtheB.Sc.(Hons.)degreein1984fromtheUniversityofBirmingham,Birmingham,U.K.,andtheD.I.C.andPh.D.degreein1987fromImperialCollegeofScienceandTechnology,UniversityofLondon,London,U.K.

HewasaLecturerinpowerelectronicsattheUniversityofNottingham,Nottingham,U.K.,in1987–1990.In1990,hetookupalectureshipattheUniversityofTechnology,Sydney,Australia,wherehebecameaSeniorLecturerin1991.Hejoined

theUniversityofSydneyin1993andwaspromotedtoReaderofElectricalEngineeringandDirectorofthePowerElectronicsandDrivesResearchGroupin1996.HeiscurrentlyaChairProfessorofElectronicEngineeringandanAssociateDeanoftheFacultyofScienceandEngineeringatCityUniversityofHongKong,HongKong.Hehasauthoredmorethan150publishedtechnicalpapers,includingmorethan80refereedjournalpublications.Hisresearchinterestsincludeallaspectsofpowerelectronics.

Prof.HuireceivedtheTeachingExcellenceAwardin1999andtheGrandAp-pliedResearchExcellenceAwardin2001fromCityUniversityofHongKong.HehasbeenappointedanHonoraryProfessorbytheUniversityofSydneysince

2000.

H.C.SowasborninHongKong.HereceivedtheB.Eng.degreefromCityUniversityofHongKong,HongKong,andthePh.D.degreefromChineseUni-versityofHongKong,HongKong,in1990and1995,respectively,bothinelectronicengineering.

From1990to1991,hewasanElectronicEngineerintheResearchandDevelopmentDivision,EverexSystemsEngineeringLtd.HewasthenaPost-Doc-toralFellowatChineseUniversityofHongKongforoneyear.From1996to1999,hewasaResearchAs-sistantProfessorintheDepartmentofElectronicEn-gineering,CityUniversityofHongKong.Currently,heisanAssistantProfessorintheDepartmentofComputerEngineeringandInformationTechnology,CityUniversityofHongKong.Hisresearchinterestsincludeadaptivefiltertheory,detectionandestimation,wavelettransform,andsignalprocessingforcommu-nicationsandmultimeda.