Phase-Shifted Full Bridge DC/DC Power Converter …

1 Phase-ShiftedFull BridgeDC/DCPowerConverterDesignGuideAbst ractThe phaseshiftedfull Bridge (PSFB)converteris usedfor DC-DCconversionin variousapplications,forexamplein telecomsystemsto converta high voltagebus to an intermediatedistributionvoltage,typicall ycloserto well as isolationfromthe line voltage,sincethistopologyincludesa documentpresentsthe implementationdetailsof a digitallycontrolledPSFB systemimplementedonthe HVPSFBkit kit convertsa 400 VDC inputto a regulated12V DC outputand is ratedfor operationsup to (PCMC)and voltagemodecontrol(VMC)implementationsar e (ZVS)and varioussynchronousrectificationschemes, generatingcomplexgatedrivewaveforms,requ iredby thesecontrolschemes,and intelligenttimingcontrol,to optimizesystemperformanceunderchangingop eratingconditions, step by step guideto run and get familiarwith the HVPSFB projectis also systemefficiencyabove10%ratedload,novelP CMC waveformgenerationbasedon on-chip hardwaremechanisms,and simplesystemimplementationare the highlightsof this.

2 If you wouldlike to quicklyevaluatethis kit withoutgoingthroughthe implementationdetails,pleasefollowthe accompanyingquickstartguide( )insteadof IMPORTANTNOTICEat the end of this TI referencedesignaddressesauthorizeduse, intellectualpropertymattersand otherimportantdisclaimersand May 2014 Phase-ShiftedFullBridgeDC/DCPowerConvert erDesignGuideSubmitDocumentationFeedback Copyright 2014, (TI HV EVM)UserSafetyGuidelinesAlwaysfollowTI s setupand applicationinstructions,includinguse of all interfacecomponentswithintheirrecommende delectricalratedvoltageand electricalsafetyprecautionsto helpensureyourpersonalsafetyand thoseworkingaroundyou.

3 ContactTI's ProductInformationCenterhttp:// warningsand instructionsfor followwarningsand instructionsmayresultin personalinjury,propertydamage,ordeathdue to electricalshockand termTI HV EVMrefersto an electronicdevicetypicallyprovidedas an openframed, isintendedstrictlyfor use in developmentlaboratoryenvironments,solely for qualifiedprofessionalusershavingtraining ,expertiseand knowledgeof electricalsafetyrisksin developmentand applicationof otheruse and/orapplicationare strictlyprohibitedby TexasInstruments. If you are not suitablequalified,you shouldimmediatelystop fromfurtheruse of the HV WorkAreaSafety(a) Keepworkareacleanand orderly.

4 (b) Qualifiedobserver(s)mustbe presentanytimecircuitsare energized.(c) Effectivebarriersand signagemustbe presentin the areawherethe TI HV EVMand its interfaceelectronicsare energized,indicatingoperationof accessiblehigh voltagesmay be present,for thepurposeof protectinginadvertentaccess.(d) All interfacecircuits,powersupplies,evaluati onmodules,instruments,meters,scopesand otherrelatedapparatususedin a developmentenvironmentexceeding50 Vrms/75 VDCmustbeelectricallylocatedwithina protectedEmergencyPowerOff EPOprotectedpowerstrip.(e) Use stableand nonconductiveworksurface.

5 (f) Use adequatelyinsulatedclampsand wiresto attachmeasurementprobesand ElectricalSafetyAs a precautionarymeasure,it is alwaysa goodengineeringpracticeto assumethat the entireEVMmay havefully accessibleand activehigh voltages.(a) De-energizethe TI HV EVMand all its inputs,outputsand electricalloadsbeforeperforminganyelectr icalor TI HV EVMpowerhas beensafelyde-energized.(b) Withthe EVMconfirmedde-energized,proceedwith requiredelectricalcircuitconfigurations, wiring,measurementequipmentconnection,an d otherapplicationneeds,whilestill assumingtheEVMcircuitand measuringinstrumentsare electricallylive.

6 (c) AfterEVMreadinessis complete,energizethe EVMas :WHILETHEEVMIS ENERGIZED,NEVERTOUCHTHEEVMOR ITS ELECTRICALCIRCUITSAS THEYCOULDBE AT HIGHVOLTAGESCAPABLEOF PersonalSafety(a) Wearpersonalprotectiveequipment(for example,latexglovesor safetyglasseswith side shields)or protectEVMin an adequatelucentplasticbox with interlocksto safeuse:EVMsare not to be usedas all or part of a May 2014 SubmitDocumentationFeedbackCopyright 2014, Bridge (PSFB)DC-DCconvertersare usedfrequentlyto step downhigh DC busvoltagesand/orprovideisolationin mediumto high powerapplicationslike serverpowersupplies,telecomrectifiers,ba tterychargingsystems,and ,micro-controllershavebeenrestrictedto only performingsupervisoryor communicationstasksin high performingmicro-controllerdevices,it is now possibleto use micro-controllersforclosingcontrolloopsi n thesesystems.

7 In additionto handlingthe digitalpowercontrolmeansthat functionsthat werepreviouslyimplementedin hardwarearenow implementedin additionto the flexibilitythis addsto the system,this implementadvancedcontrolstrategiesto optimallycontrolthepowerstageunderdiffer entconditionsand also PSFB converterconsistsof four powerelectronicswitches(like MOSFETsor IGBTs)that forma full -bridgeon the primaryside of the isolationtransformerand dioderectifiersor MOSFET switchesforsynchronousrectification(SR)o n the topologyallowsall the switchingdevicestoswitchwith zerovoltageswitching(ZVS)

8 Resultingin lowerswitchinglossesand an work,ZVSfor switchesin the one leg of the full bridgeand zeroor low voltageor Low VoltageSwitchingfor switchesin the otherleg is achievedacrossthe completeload range,by changingdead-timesfor primaryside switchesbasedon load suchan isolatedtopology,signalrectificationis requiredon the systemswith lowoutputvoltageand/orhigh outputcurrentratings,implementingsynchro nousrectificationinsteadof dioderectificationachievesthe best possibleperformanceby this work,currentdoublersynchronousrectificat ionis implementedon the secondaryside with differentswitchingschemesto achieveoptimumperformanceundervaryingloa d DC-DCconvertersystemcan be controlledin variousmodeslike voltagemodecontrol(VMC),averagecurrentmo decontrol(ACMC)or peakcurrentmodecontrol(PCMC).

9 Implementingthesedifferentcontrolmodesfo r controllingthe samepowerstagetypicallyrequiresredesigni ngthe controlcircuitalongwithsomechangesto the microcontrollerbasedsystem,all thesemodescan be experimentedwith on the samedesignwith minimalor no systemisimplementedhereusingVMCand a highlydesiredcontrolschemefor powerconvertersbecauseof its inherentvoltagefeedforward,automaticcycl eby cyclecurrentlimiting,flux balancingand a PSFB systemrequirescomplexPWMwaveformgenerati onwith newapproachto this waveformgenerationis presentedusingTMS320F2802xand TMS320F2803x(TexasInstrumentsPiccoloseri es)

10 Microcontrollerswithoutrequiringany usedto provideappropriateslopecompensationthat guaranteesopenloop stabilityand eliminates/limitssub-harmonicoscillation sat the a micro-controller,the regulatedoutputvoltageis dependenton the amountofoutputvoltageripple,whichin turn is dependenton the relationis explainedin detailanddifferentsolutionsare efficiencygreaterthan90%downto 10%load is achievedwith May 2014 Phase-ShiftedFullBridgeDC/DCPowerConvert erDesignGuideSubmitDocumentationFeedback Copyright 2014, showsa simplifiedcircuitof a phaseshiftedfull , QB, QC and QDformthe full -bridgeon the primaryside of the transformerT1.