模拟电子线路-[英文课件]--杨凌【英文】机械工业出版-chpt-11

Chap11,TeachingMaterialsofAnalogCircuits,Chapter10VoltageRegulators,10.0PreviewTherequirementforareliablesourceofconstantvoltageinvirtuallyallelectronicsystemshasledtomanyadvancesinpowersupplydesign.Designershaveusedfeedbackandoperationalamplifiers,aswellaspulsecircuittechniquestodevelopreliableconstantvoltage(andconstant-current)powersuppliers.Avoltageregulatorisacircuitordevicethat,10.0Preview,provideaconstantvoltagetoaload.Theoutputvol-ageiscontrolledbytheinternalcircuitryandisrel-ativelyindependentoftheloadcurrentsuppliedbytheregulator.AbasicdiagramofadcpowersupplyisshowninFigure10.1.,10.0Preview,Webrieflyconsideredconstant-voltagecircuitsorvoltageregulators,WhenwestudieddiodecircuitsinChapter1,InthisChapter,WewilldiscussexamplesofICvoltageregulators.,Figure10.2,10.1RectifierandFilter,一、Single-PhaseBridgeRectifier,VL=0.9V2(10-1),10.1RectifierandFilter,二、Filters,RippleVoltage,andDiodeCurrentIfacapacitorisaddedinparallelwiththeloadresistorofabridgerectifiertoformasimplefiltercircuit,asshowninFigure10.4.,10.1RectifierandFilter,Figure10.4,Td=RLC(35)2(10-6),VL=(1.11.2)V2(10-7),Thediodeinafilteredrectifiercircuitconductsforabriefintervalnearthepeakofthesinusoidalinputsignal.(Figure10.5),10.1RectifierandFilter,10.1RectifierandFilter,Figure10.6,三、InductanceFilterExample10.1YangP339Example11-1,10.2SeriesFeedbackRegulators,Thefundamentalclassesofvoltageregulatorsarelinearregulatorsandswitchingregulators.Bothoftheseareavailableinintegratedcircuitform.Therearetwobasictypesoflinearregulator.Oneistheseriesregulatorandtheotheristheshuntregulator.Inthissection,wewilllookattheseriesregulator.一、QualityIndexVO=f(VI,IO,T)(10-8),10.2SeriesFeedbackRegulators,orVO=KVVI+RoIO+STT,1.,VoltageRegulation,VOVOVOVO=VI+IO+TVIIOT,10.2SeriesFeedbackRegulators,2.OutputResistance,Voltage-RegulationCoefficient,3.TemperatureCoefficient,10.2SeriesFeedbackRegulators,二、SeriesFeedbackRegulatorsThebasiccomponentsofseriesfeedbackregula-torsareshownintheblockdiagraminFigure10.8.,10.2SeriesFeedbackRegulators,Noticethatthecontrolelementisinserieswiththeloadbetweeninputandoutput.Theoutputsamplecir-cuitsensesachangeintheoutputvoltage.Theerrordetectorcomparesthesamplevoltagewithareferencevoltageandcausesthecontrolelementtocompensateinordertomaintainaconstantoutputvoltage.Abasicop-ampseriesregulatorcircuitisshowninFigure10.9.TheresistivevoltagedividerformedbyR1andR2sensesanychangeintheoutputvoltage.,10.2SeriesFeedbackRegulators,VI(IL)VOVFVB(IC)VCEVO,R2VF=VOR1+R2,R1VO(1+)VREFR2,(10-13),RL,10.2SeriesFeedbackRegulators,WhentheoutputtriestodecreasebecauseofadecreaseinVIorbecauseofachangeinloadcurrent.Aproportionalvoltagedecreaseisappliedtotheop-amp,sinvertinginputbythedivider.Sincethezenerdiode(DZ)holdtheotherop-ampinputatanearlyfixedreferencevoltage,VREF,asmalldifferencevolt-age(errorvoltage)isincreasedacrosstheop-amp,sinputs.Thisdifferencevoltageisamplified,andtheop-amp,soutputvoltageincreases.Thisincreaseis,10.2SeriesFeedbackRegulators,appliedtothebaseofT,causingthecollector-emittervoltageVCEtodecrease,andtheoutputvoltageVOtoincreaseuntilthevoltagetotheinvertinginputagainequalsthereference(zener)voltage.Thisactionoffsetstheattempteddecreaseinoutputvoltage,thuskeepingitnearlyconstant.Thepowertransistor,T,isusedwithaheatsinkbecauseitmusthandlealloftheloadcurrent.Forhighestaccuracy,DZisreplacedwithanICreference.AsshowninFigure10.10.,10.2SeriesFeedbackRegulators,CJ336,CJ329;MC1403,AD580.,VREF=VBE3+IC2RC2,VTIC1IC2=()ln()RE2IC2,VTRC2IC1VREF=VBE3+ln()RE2IC2,EGVREF=1.205V(10-14)q,10.3Three-TerminalRegulator,一、FixedThree-TerminalRegulatorInthissection,wewillanalyzeanexampleofathree-terminalpositivevoltageregulatorfabricatedasanIC.Theequivalentcircuit,showninFigure10.11,ispartofthe78LXXseries,inwhichtheXXdesign-ationindicatestheoutputvoltageoftheregulator.Forexample,an78L05isan5Vregulator.1.Start-upCircuitOncethebiascurrentisestablished,Zenerdiode,10.3Three-TerminalRegulator,Figure10.11,10.3Three-TerminalRegulator,DZ2providesthebasicreferencevoltage.TransistorT1andT2anddiodeDZ1formastart-upcircuitthatappliestheinitialbiastothereferencevoltagecircuit.VIVDZ1T1T2,T3,T4T5VDZ2AsthevoltageacrossDZ2reachestheZenervol-tage,transistorT2turnsoff,sincetheB-Evoltagegoestozero(DZ1andDZ2areidentical)and,thestart-upcircuitistheneffectivelydisconnectedfromtherefer-encevoltagecircuit.,10.3Three-TerminalRegulator,2.ReferencevoltageThereferenceportionofthecircuitiscomposedofZenerdiodeDZ2andtransistorT4、T3、D2、D1、andresistanceR1、R2、R3.T3、D2andD1,whichareusedfortemperaturecompensation.ZenerdiodeDZ2isbiasedbythecurrent-sourcetransistorT4.Thetemperature-compensatedportionofthereferencevol-tageatthenodebetweenR1andR2isappliedtothebaseofT7,whichispartoftheerroramplifier,10.3Three-TerminalRegulator,ThebiascurrentinT4isestablishedbythecur-rentinT5,whichisamultiple-collectortransistor.Tr-ansistorT5isbiasedbythecurrentinT3,whichiscontrolledbytheZenervoltageacrossDZ2andtheB-EjunctionvoltagesofT3,D2andD1,Consequently,thebiascurrentsinthereferenceportionofthecir-cuitbecomealmostindependentoftheinputsupplyvoltage.Thisisinturnmeansthatthereference,VZ23VBEVREF=R1+2VBE(10-15)R1+R2+R3,10.3Three-TerminalRegulator,voltage,andthustheoutputvoltageareessentiallyindependentofthesupplyvoltage.Theoverallresultisverygoodlineregulation.3.TheErrorAmplifierandTheSamplecircuitTheerroramplifieristhedifferentialpairT7andT8,biasedbyT6andR6,TheerroramplifieroutputistheinputtothebaseofT9,whichisconnectedasanemitterfollowerandformspartofthedrivefortheseries-passtransistors.Theseries-passoutput,10.3Three-TerminalRegulator,transistorsT10andT11areconnectedinaDarlingtonemitter-followerconfiguration.Afractionoftheoutputvoltage,determinedbythevoltageR12andR13,isfedbacktothebaseofT8,whichistheerror-amplifierinvertingterminal.Iftheoutputvoltaheisslightlybelowitsnormalvalue,thenthebasevoltageatT8issmallerthanthatatT7,andthecurrentinT7becomesalargerfractionofthetotaldiff-ampbiascurrent.Theincreased,10.3Three-TerminalRegulator,currentinT7inducesalargercurrentinT10,whichinturnproducesalargercurrentinT11andincreasestheoutputvoltagetothepropervalue.Theoppositeprocessoccursiftheoutputvoltageisaboveitsnormalvalue.4.ProtectionDevicesTransistorsT13andT14andresistorR3inthere-gulatorinFigure10.11providethermalprotection.Usually,theB-EvoltageofT14isapproximatly,10.3Three-TerminalRegulator,330mV,whichmeansthatbothT14andT13areeff-ectivelycutoff.Asthetemperatureincreases,thecombinationofanegativeB-Etemperaturecoeffi-cientandanincreaseinIC3causesT14tobeginconducting,whichinturncausesT13toconduct.ThecurrentinT13shuntscurrentawayfromtheoutputseries-passtransistorsandproducesthermalshutdown.,10.3Three-TerminalRegulator,OutputcurrentlimitingisprovidebytransistorT12andresistorR11,aswesawpreviouslyinop-ampoutputstages.ThecombinationofresistorsR14andR15anddiodeDZ3andDZ4produceswhatiscalledafoldbackcharacteristic.Thevastmajorityofthepowerdissipatedintheregulatorisusuallyduetotheoutputcurrent.Theoutputcurrentlimit,topreventpowerdissi-pationfromreachingitsmaximumvaluePCM.,10.3Three-TerminalRegulator,R14+R15R15IO=VBE12(VIVO)VZ3VZ4(10-17)R11R14R14R11,二、AdjustableThree-TerminalRegulatorTheLM317isanexampleofathree-terminalpositiveregulatorwithanadjustableoutputvoltage.ThestandardconfigurationisshowninFigure10.12.,(VIVO)(VCE10-11)IOPCPCM,10.3Three-TerminalRegulator,VREFVO=VREF+(+Iadj)R2R1,R2=VREF(1+)+IadjR2R1,Iadj,R2VOVREF(1+)R1,(10-17),10.3Three-TerminalRegulator,TheLM337isthenegativeoutputcounterpartoftheLM317isagoodexampleofthistypeofICregulator.LiketheLM317,theLM337requirestwoexternalresistorsforoutputvoltageadjustment.三、ApplicationsofThree-TerminalRegulator1.FixedThree-TerminalRegulatorFigure10.13showsthebasiccircuitconfigur-ationofafixedthree-terminalregulator.Insomeapplications,capacitorsmaybeinsertedacrossthe,10.3Three-TerminalRegulator,Figure10.13,inputandoutputterminals.,10.3Three-TerminalRegulator,Figure10.14,IO=IO1+IO2,IOIO1VR3T3T2(saturation)VBE1IC1,2.AdjustableThree-TerminalRegulator,10.3Three-TerminalRegulator,Figure10.15,10.3Three-TerminalRegulator,R10.1,Summary,1.Bridgerectifiercircuitconvertasinusoidalsignaltoanapproximatedcsignal.Adcpowersupply,whichisusedtobiaselectroniccircuitsandsystems,utilizethesetypesofcircuits.Acapacitorcanbeconnectedtotheoutputoftherectifiercircuittoreducetherip-pleeffect.Theripplevoltageiscausedbythecharg-inganddischargingofthefiltercapacitor.2.Voltageregulatorskeepaconstantdcoutputvol-tagewhentheinputorloadvarieswithinlimits.,Summary,3.Zenerdiodeoperateinthereversebreakdownregion.Sincethebreakdownvoltagenearlyconstantoverawiderangeofcurrents,thesedevicesareusefulinvoltagereferenceorregulatorcircuits.4.Abasicvoltageregulatorconsistsofarefer-encevoltagesource,anerrordetector,asa