关闭

关闭

关闭

封号提示

内容

首页 Switch-Mode Power Supplies Spice Simulations an…

Switch-Mode Power Supplies Spice Simulations and Practical Designs.pdf

Switch-Mode Power Supplies Spic…

上传者: xjy0431 2010-12-18 评分 0 0 0 0 0 0 暂无简介 简介 举报

简介:本文档为《Switch-Mode Power Supplies Spice Simulations and Practical Designspdf》,可适用于IT/计算机领域,主题内容包含INTRODUCTIONTOPOWERCONVERSIONUserfriendlinessisakeyfactorforthecommercials符等。

INTRODUCTIONTOPOWERCONVERSIONUserfriendlinessisakeyfactorforthecommercialsuccessofanysimulationprogramThegrowingcomplexityofintegratedcircuitsandequipmentmakesthisaspectmoreandmoreimportantDespitenumerouspublicationsdevotedtotheSimulationProgramwithIntegratedCircuitEmphasis(SPICE),itstillscaresthenovicewhenitsnameismentionedDevelopedinthemidsbytheUniversityofCalifornia,Berkeley,theSPICEprogram’smainaimwastofulfilltheneedsoftheelectronicindustry––mainlyintegratedcircuitmakersHowever,withthesupportandfundsfromprivateeditors,theSPICEprogramhasevolvedoveranumberofyearsintomanypracticalandaffordablepackages,withemphasisonprovidingbothlowpricedandfriendlyaccesstobeginnersTheperformanceofSPICEcansignificantlyhelpyouspeedupthedesignphaseoftheequipmentyouarecurrentlyworkingon,evenifSPICEisnotabletogenerateanelectronicschematicbyitself!SPICEisinherentlyefficientbecauseifyoustartworkingwithanunfamiliarconcept,itwillquicklyenableyoutograspthefullmeaningofanyparticulararchitecturebyunveilingitspeculiarwaveformsYoucanthususethesimulatortogaininsightintothecircuityouhavetobuildandalsoensureallparametersaretakenintoaccountbeforethebreadboardphaseThisbookhasbeenwrittenforpowersupplydesigners,expertsintheirfields,butalsoforbeginnerswhowouldliketounderstandthesecretsofswitchmodepowerconversionManipulatingvirtualcomponentsonacomputerscreen,withoutthehazardofhighvoltage,offersaninterestingandsafewaytolearnthetechniqueFurthermore,the“experience”gainedinsimulation,anditisalsotrueforexpertssimulatinganovelconcept,willletyoufeelmorecomfortablewhenbreadboardingonthebench“DOYOUREALLYNEEDTOSIMULATE”HowmanytimeshaveyouheardthisquestionwhenaskingforasimulationpackageoranewcomputerThefollowingstatementsdonotrepresentanexhaustivelistofprosaboutcomputersimulation,buttheycancertainlybethoughtasa“helplist”availableduringthenegotiations:Hereisanargument:simulationcanavoidwasteoftimeandmoneyWithitsinherentiterativepower,SPICEcoversnumerousapplicationcasesinwhichyoucouldeasilydetectanydesignflaworproductweaknessThestabilityofaclosedloopSMPSrepresentsatypicalapplicationwhensomekeyfeedbackelementsaremoving(ie,thevariableloadthataffectsapole)orstarttodegradewithtemperatureandaging(astheelectrolyticequivalentseriesresistor)Moreover,designideascanalsobetestedorassessedinasnapshotthroughacomputerand,iftheyareworthtrying,furtherrefinedinthelabCHAPTERBassoCHqxd:PMPageDownloadedfromDigitalEngineeringLibraryMcGrawHill(wwwdigitalengineeringlibrarycom)CopyrightTheMcGrawHillCompaniesAllrightsreservedAnyuseissubjecttotheTermsofUseasgivenatthewebsiteSource:SWITCHMODEPOWERSUPPLIESYoucanstarttoworkonaprojectbydownloadingcomponentsmodelsandbecomefamiliarwiththekeyelements,beforegoingtothebenchorwaitingforthesamplestobedeliveredOncetheyarrive,youwillhavealreadygainedinsightandthedebugphaseonthebenchwillclearlyhavebeenbeneficial!Simulatetestmeasurementswheneveryoudonotowntheadequateequipment:bandwidthmeasurementsrepresentagoodexampleIfyoucannotaffordanetworkanalyzer,thenaprovensmallsignalmodelcanstarttohelpyourefineyourfeedbackloopWhenrunonthefinalprototype,stabilityassessmentswillbefasterandmoreefficientPowerlibrariesaresafe:theyletyouexperiment“whatif”whenamperesandkilovoltsareflowinginthecircuitwithoutblowingupinthecaseofawrongconnection!Also,theyletyouseehowyourdesignreactstoashortcircuitoftheoptocoupler,ortheopeningofaresistorSPICEcanbegintogiveyoutheanswerWHATYOUWILLFINDINTHEFOLLOWINGPAGESThisbookthoroughlydetailstheadvantagesoftheSPICEpowertoletyouunderstand,simulate,test,andfinallyimprovetheswitchmodepowersupply(SMPS)youwanttodesignByprovidingyouwithspecificsimulationrecipes,thisworkintendstofacilitateasmuchaspossibleyourSMPSdesignUnlikeinotherbooks,theauthorhasstriventobalancethetheoreticalcontent,necessarytounderstandandquestionsimulationresults,andtheneedforpracticaldesignexamplesThisisdevelopedthroughouttheeightchaptersofthebookChapterexplainsswitchmodepowersupplytechniquesandtypesofconverters,anditintroducesafewimportantresultstohelpyoubetterunderstandaveragingtechniquesChapterexplainshowaveragemodelswerederived,anddifferenttypesaredescribedAgoodcomprehensionofthischapterisfundamental:itwillhelpyouquestioncertainweirdSPICEdata,resultingfromabadmodelimplementationIfyoudonotunderstandthewaythemodelhasbeenderived,youwillobviouslyfacesomedifficultiesinresolvingtheseissuesInChap,youwillalsolearnthewaytowireanaveragemodelandrunbasicsimulationsClosingtheloopisobviouslyanimportantaspectofconverterdesignandisoftenoverlookedThisisnotthecasehere,andChapwillguideyouthroughcontrolloopdesign,againusingpracticalexampleswithaTLandnotopampsonly,asoftenseenintheliteratureSincenoteveryintegratedcircuitalwayscomeswithaSPICEmodel,ChapdescribeshowthegenericswitchedmodelswerederivedThereadingofthischapterwillinterestthepersonwhowantstostrengthenherorhisknowledgeinSPICEmodelwritingChapterdescribespracticaldesignsofthethreebasicnonisolatedtopologies,includingthefrontendfilterBeforeanalyzingofflineconverters,ChapshowshowtodesigntherectifyingsectionandspendstimeonthevariouspowerfactorcorrectiontechniquesChapterisentirelydedicatedtotheflybackconverter,withspecificdesignexamplesattheendFinally,theforwardconverterappearsinChap,againassociatedwithadesignexampleWhenoneisdiscussingSPICEsimulations,oneofthegreatestissuesfindsitsrootintheversionsyntaxMostSPICEeditorsdealwithaproprietarysyntax,sometimesSPICEconformant,thatmakestranslationfromoneplatformtoanotheradifficultandpainfulexerciseToallowtheuseofdifferentsimulators,thestandardmodelspresentedthroughoutthepagesarecompatiblewithIntusoftIsSpice(SanPedro,Calif)andCADENCE’sPSpice(Irvine,Calif)Tohelpyouquicklycopyandpastetheexamples,wehaveincludedaCDROMinthisbookSomeselectedsimulationexamplesareofferedinIsSpiceandPSpicesyntax,andyoucaneasilyloadthemonyourcomputerifyouareequippedwithoneofthesesoftwareprogramsCHAPTERONEBassoCHqxd:PMPageDownloadedfromDigitalEngineeringLibraryMcGrawHill(wwwdigitalengineeringlibrarycom)CopyrightTheMcGrawHillCompaniesAllrightsreservedAnyuseissubjecttotheTermsofUseasgivenatthewebsiteINTRODUCTIONTOPOWERCONVERSIONForstudentsornewcomerstotheSPICEworld,weaddthedemonstrationversionsoftheseeditorsTheyletyouopentheaforementionedfilesandsimulatesomeofthem(thosedemosaresizelimited)togiveyouatasteofwhatthefullversioncandoOtherdemonstrationversionsalsofindaplaceintheCDROM,suchasPSIM,Transim,Tina,Multisim,PowerBSpice,MicroCap,SpiceandTopSPICEForprofessionalpowersupplydesigners,anotherdiskisseparatelydistributedThisdiskcontainsthedesignexamplespresentedinthebookplusnumerousotherindustrialapplicationsusingrealcontrollersPleasevisittheauthor’swebsitefordistributiondetails(http:persoorangefrcbassoSpicehtm)WHATYOUWILLNOTFINDINTHISBOOKThisbookdoesnotdescribethewaySPICEoperates,nordoesitsolvetypicalelectriccircuitsItassumesthatthereaderisalreadyfamiliarwiththebasicsofSPICEsimulationsNumerousbooksandpapersareavailableonthesubjectasthegivenReferencessectiondetails,Wheneverpossible,theextendedbibliographywillguideyourchoiceifyouwishtostrengthenyourknowledgeinaparticulardomain,suchassometopologiesthatyouareunfamiliarwithIfsometheoreticalresultsaresometimesdeliveredjust“asis,”westronglyencouragethereadertodigfurtherintotheappropriateliteratureandacquirethetheorythatprecedestheresultThebookalsoonlyfocusesonasystemapproachNoSPICEdescriptionoftypicaldiscretepowerelementssuchasdiodes,MOSFETs,etc,isproposedFinally,hereistheimportantstatement,probablythemostinterestingone!SPICEdoesnotreplacethebreadboardphase,nordoesitshieldyoufromwritingequationsorunderstandingelectronicsItlookslikeasimplesentence,buttheauthorhasoftenbeenconfrontedbydesignersshowingboardsinthetrashandclaiming,“ButSPICEsaiditwouldwork!!”Yes,allideasworkonpaperuntiltheyfacethesolderingironcondemnationUseSPICEasadesigncompanion,acircuitinsiderthatcanrevealwaveformsdifficulttoobserveButalwaysquestionthedelivereddata:isthistherealbehavior,haveIbeenmisledsomewhere,doesasimplecalculationmoreorlessconfirmwhatIseeAfterthisbriefintroduction,itistimetoplungeintotheintricacyoftheSwitchModePowerSupplydesignandsimulationwithSPICECONVERTINGPOWERWITHRESISTORSIntheelectronicsworld,differenttypesofcircuitriesmustcohabit:logicdevices,analogcircuits,microprocessors,andsoonUnfortunatelyforthedesigner,thesecircuitsdonotcopewithasingle,fixed,powersupplyrail:amicroprocessororadigitalsignalprocessor(DSP)willneedastableVsourceorless,afrontendacquisitionboardwillrequireVandperhapssomelogicgluearoundastandardVForthefinalboardbeingsuppliedfromasinglepowerpoint,eg,themainsoutletorabattery,howisonetoadaptanddistributeallthesedifferentvoltagestotheconcernedportionsThesolutionconsistsofinsertingasocalledconvertertoadaptthevoltagedistributiontothecircuitneedsAssociatingResistorsFigureportraysthesimplestoptionadesignercanthinkof:resistivedividers!IfourDSPconsumesmAoverV,thenitcanbereplacedbyaresistor,thesameasforourINTRODUCTIONTOPOWERCONVERSIONBassoCHqxd:PMPageDownloadedfromDigitalEngineeringLibraryMcGrawHill(wwwdigitalengineeringlibrarycom)CopyrightTheMcGrawHillCompaniesAllrightsreservedAnyuseissubjecttotheTermsofUseasgivenatthewebsiteINTRODUCTIONTOPOWERCONVERSIONmA,VlogiccircuitviatheresistorFromaVsource,wecanthencalculatethedroppingresistors:()()Beforegoingfurther,pleasenotethatAorAwas,respectively,notedinthecalculationasmormThisisdonetoretaintheSPICEnotationforunits,withoutanyspaceItadherestothefollowingrulesandwillbeextensivelyusedintheremainingportionsofthebook:ppiconnanoumicrommillikkiloMegmega•Bewarenottomixmegaandmilli,averycommonmistake:mm,MMegUnfortunately,theseresistorswillbetheseatofapermanentvoltagedrop,andpowerdissipation(inheat)willoccurThedissipatedpowerforeachresistoris(a)(b)Fromthesevalues,wecannowevaluatethesystemefficiencyobtainedbydividingthedeliveredoutputpowerPoutbythepowertakenawayfromthesourcePin:(a)(b)PinmmWPoutmmmWP()mWP()mWRmRmCHAPTERONEFIGUREThesimplestvoltagedistributionviaresistorsRRloadVinVRRloadVlogicVDSPBassoCHqxd:PMPageDownloadedfromDigitalEngineeringLibraryMcGrawHill(wwwdigitalengineeringlibrarycom)CopyrightTheMcGrawHillCompaniesAllrightsreservedAnyuseissubjecttotheTermsofUseasgivenatthewebsiteINTRODUCTIONTOPOWERCONVERSIONTheefficiency,representedbytheGreekletteror“eta,”canbecomputedbydividingPoutbyPin,or()whichisanextremelypoorperformance!Theloss,dissipatedinheat,issimplythedifferencebetweenthepowerdeliveredbythesourceandthepower,convertedastherealwork,Pout()Inourexample,thelossismWAClosedLoopSystemIftheloadchanges,oriftheinputvoltagedrifts,whatisgoingtohappenWell,sinceourinputtooutputtransferratio,denotedM,isfixed,theoutputvoltagewillalsovaryTherefore,weneedtothinkofakindofregulatedsystemthatpermanentlyobservestheoutputpowerdemandandadjuststheseriesresistortomaintainaconstantoutputvoltage,iftheoutputvoltagerepresentsthevariableofinterestForawelldesignedsystem,theconvertermustalsoensureaproperregulationindependentlyfrominputvoltagevariationsToreachthisgoal,weneedtouseseveralparticularcomponentssuchas•AreferencevoltageVref:Thisvoltageisbydefinitionextremelystableintemperatureandpreciseinvalue(eg,)Aprogrammableshuntregulator,suchasaTLadjustablezener,coulddothejob•Anoperationalamplifier(opamp):Thisdevicewillobserveaportionoftheoutputvoltage(Vout)andcompareittothereferenceVrefItwillactually“amplify”theerror,thedifferencebetweenVoutandVref,todriveaseriespasselementTheerrormonitoredbytheopampisusuallydenominatedbytheGreeklettereor“epsilon”:•Aseriespasselement:ItcanbeaMOSFETorabipolartransistorbutworkinginalinearmode,playingtheroleofthenecessaryvariableresistorIfitisaMOSFET,thestaticdrivingpowerisForabipolar,thereisaneedtosupplyasufficientamountofbasecurrenttodelivertherightcollectororemittercurrentThisiscalledthebiascurrentFigurefinallyshowshowourresistiveconvertercouldbeimproved,let’ssayfortheVsectionTheerroramplifierismadeviaavoltagecontrolledvoltagesource(Eprimitive)andfeaturesagainofk(ordB)Oneofitsinputreceivesthevoltagereferencewhereastheotherone,theinvertinginput,isbiasedbyaportionoftheoutputvoltageThisisactuallyalinearregulator,however,limitedintheinputvoltagerangesinceVinshallbeaboveVoutbyaVbe,atleast,toguaranteeaproperdriveforQIfVoutisbelowthetarget(Vinourexample),EoutputincreasesandstrengthensQbiascurrent:VoutgoesupOntheotherhand,supposetheloadhassuddenlybeenreduced,thereforeVoutexceedsVThankstoE,Qbiascurrentgoesdown,reducingtheoutputvoltageuntilregulationismetagainTheoutputvoltageobservation,whichdeliversVout(afractionoftheoutputvoltage),isobtainedthrougharesistivedividermadeofRupperandRlowerCalculatingtheirvaluesisstraightforward:LetusfixacurrentcirculatinginthedividerbridgeSincethereisnobiasingcurrentforEintheexample(thisisthecaseformostMOSbasedtechnologies),wecouldtakeIbA,forexampleAlowervalueisacceptable,butdegradesthenoiseimmunityinanoisyenvironmenteaVoutVrefPlossPinPoutPoutPoutPoutabPoutPinINTRODUCTIONTOPOWERCONVERSIONBassoCHqxd:PMPageDownloadedfromDigitalEngineeringLibraryMcGrawHill(wwwdigitalengineeringlibrarycom)CopyrightTheMcGrawHillCompaniesAllrightsreservedAnyuseissubjecttotheTermsofUseasgivenatthewebsiteINTRODUCTIONTOPOWERCONVERSIONIbequalsAandentirelycirculatesinRlowerThankstothecontrolloop,Vis“seen”acrossRlowerTherefore,ThevoltagedropacrossRupperisVoutVrefThus,IfweneglectthepowerneededtodriveQ,thenallthesourcecurrentIinflowsintotheloadasIoutTherefore,applyingEq(),wecanderivetheefficiencyforthislinearregulator:()Ifwenowplottheefficiencyversustheinputvoltage,wecanseehowdifficultthesituationbecomesinthepresenceofsmallMratios(Fig)Forthesereasons,resistivedividertypeofconverters,thatistosayseriespassregulators,arelimitedtoapplicationwhereMdoesnotfallbelowOtherwisetheheatdissipationburdenshallbecomearealhandicapOnthePoutPinVoutIoutVinIin<VoutVinMRupperVoutVrefIbukRlowerukCHAPTERONEInputvoltage(V)Efficiency()FIGUREAssoonasMdiminishes,theefficiencydramaticallydrops(VoutV)QNVinEkVrefRlowerkRupperkRloadIinIoutVoutIb––FIGURETheadditionofanerroramplifierbringsregulationtothecircuit:wehavebuiltalinearregulatorBassoCHqxd:PMPageDownloadedfromDigitalEngineeringLibraryMcGrawHill(wwwdigitalengineeringlibrarycom)CopyrightTheMcGrawHillCompaniesAllrightsreservedAnyuseissubjecttotheTermsofUseasgivenatthewebsiteINTRODUCTIONTOPOWERCONVERSIONotherhand,whentheuserreallyneedstooperatehisregulatortoratiosMcloserto(VinveryclosetoVout),thelowdropout(LDO)regulatormadewithaPNPbecomesagoodchoiceTheinputlowlimitisnowlinkedtothetransistorVce(sat)(afewhundredmillivolts,orless)ratherthanitsVbe(aroundmVatroomtemperature,C)Toclosethestudyonregulatorefficiency,wecantakethreedifferentoutputexampleswithlinearregulators,whereoutputandinputconditionsvary:VinVVoutVVVinVoutVVinVVoutVVVinVoutVVinVVoutVVVinVoutVAsaresult,onecanseethatahighefficiencycanbeobtainedwithalinearregulatorifVissmall(asplottedinFig),butalsoifVoutVDerivingUsefulEquationswiththeLinearRegulatorFigureisinterestingbecausewecanuseittoderivegeneralstatements,pertinenttotheclosedloopworldwearegoingtoenter,linear,orswitchedSupposethatweremovetheerroramplifierandreplaceitbyafixedvoltagesourceofV,ouractualopampoutput(lookatFigvalues)asFigashowsTheregulatorbecomesasimpleemitterfollowercircuit,affectedbyanoutputimpedanceandanoutputvoltageAssuch,itcanbedescribedwithitsequivalentThéveningenerator,whatFigbsuggestsRs,OLrepresentstheopenloopoutputimpedanceandVth,thevoltagedeliveredwhenbiasedbyacontrolvoltageVc,ourfixedVintheapplicationLetusnowusethisrepresentationandredrawourclosedloopregulatoraroundit,ignoring,fornow,theinputvoltagecontribution:InFig,Vout(s)iscomparedtoVref(s)viaaresistivedivideraffectedbyatransferratioof

用户评论(1)

0/200

精彩专题

上传我的资料

每篇奖励 +2积分

资料评价:

/49
仅支持在线阅读

意见
反馈

立即扫码关注

爱问共享资料微信公众号

返回
顶部