Power Supply Fundamental

AgendaAgenda•Non-isolatedDC-DCTopologyTypesInductiveDC-DC•ControlLoopUnderstandingPWMWorkingmechanismPowerStageLoopFeedbackLoop•Simplytojudgestabilityofconverter•BuckConverterDesignExample•PCBLayoutconsideration•TypicalApplicationPowerStructureandHeroProducts•BackupTraditionalBuckConverterEfficiencyAnalysisTraditionalBuckConverterEfficiencyAnalysis+LDCoRVO+-VINQ1iQ2+VDiQ2+LCoRVO+-VINQ1+VQ2Non-SynchronousBuckSynchronousBuckMOSFETDiodeDDSON2QPPVRiHigherEfficiency:ParallelwithanexternalSchottkydiodeLongerBatteryRun-TimeDQ2iQ2+LCoRVO+-VINQ1+VLiQ1Q2iLVPHiQ1iLVIN-Vbdt1t2t3t4iQ2IoTsIQ2RQ2Ton=DTsDeadtimeVL-VoVIN-VoDVVTD1VDTVVINososoINVolt-SecondbalanceacrossLOptimizedIdealBuckConverterSteadyStateAnalysis(CCM)OptimizedIdealBuckConverterSteadyStateAnalysis(CCM)ActualBuckConverterAnalysis:DutyCycleActualBuckConverterAnalysis:DutyCyclevsvsRds_onRds_onandLoadandLoad1Q2QoINLQ2ooRRIVRRIVD VoltageGainINoVVVOMAX1VOMAX2VOMAX0DTraditionalBoostConverterStructureTraditionalBoostConverterStructure+LDCoRVO+-VINQ1iQ1+VDOptimizedBoostConverterStructureOptimizedBoostConverterStructure+LDCoRVO+-VINQ1iQ1+VDDMOSFETDDSON2QPPThenVRiIFHigherEfficiencyLongerBatteryRun-Time+LCoRVO+-VINQ1iQ2+VQ2Q2VPHiQ1iLVo+VbdiQ2t1t2t3t4Vo-VINVINIoVLDeadtimeTsTon=DTst5OptimizedIdealBoostConverterSteadyStateAnalysis(CCM)OptimizedIdealBoostConverterSteadyStateAnalysis(CCM)+LCoRVO+-VINQ1iQ2+VLQ2iQ1iLVPHD11VVTD1VVDTVINosINosINVolt-SecondbalanceacrossLinSteady-stateandCCMNegativeBuckNegativeBuck--BoostConverterBoostConverter•Inverter|Vo|=Vin*D/(1-D)VINVOUTINOUT0VD1VD*VINOUTControlLoopUnderstanding:ControlLoopUnderstanding:PWMWorkingMechanismSample:PWMWorkingMechanismSample:SynchronousBuckConverterwithVoltageModeControlSynchronousBuckConverterwithVoltageModeControlVOLPWMComparator-+-+VREFD=dutycycleCompensatorVINRCoQ1Q2+RESRGatedriverZiZfVcompVPH+-tonVINVrampVcompTsVPHsonTtDControlLoopUnderstanding:ControlLoopUnderstanding:PWMWorkingMechanismSample:PWMWorkingMechanismSample:InputVoltageFeedInputVoltageFeed--ForwardFunctionGoodLineRegulationForwardFunctionGoodLineRegulationVOL-+-+VINRQ1Q2+ZiZfVcompVPH+-DPWMRampPWMComparatorVREFVIN1VrampVcompVPHD1•PWMRampamplitudeisproportionaltoVIN�D=Vo/VIN�FastLineStepTransientResponseDoesNotrelyontheregulationloopVP0.5VPVIN2D2DutyCycledoubledwhenVINdropsbyhalfD2=2D1ControlLoopUnderstanding:ControlLoopUnderstanding:ACModelforBuckConverterACModelforBuckConverter+ReferenceVoltageCompensationBulkCapacitance*CeramichelpsathighfrequencyFilterCircuit:PowerStageVOUTVINPWMGain(V/V)++E/ARCCRDRIVEQ2QQ++R5C8C7REFR3C6R2R4VOSAWTOOTHREFERENCEVEPWMCOMPARATORQ1VI+LControlLoopUnderstanding:ControlLoopUnderstanding:PowerStageLoopPowerStageLoop•PWMisjustagainstage•OutputfilterisanLCresponse•OutputcapacitorESRwilladdazeroORCL21fDoublepoleatresonantfrequencyESRofOutputCapacitor,ZeroOESR_ZeroCESR21fSlopeis-40dB/decadeSlopeis-20dB/decade12*L1C1GNDVinVoCPZ1VREFVOUTRZ1RP1RSETCZ2+RPZ2CP2VCMP2Z2PZ2ZCR21f-20dB/decade2P2PZ2PCR21f1PZ1Z1ZCR21f1PZ1P1PCR21f20dB/decade•TypeIII:bestloadtransientandregulation,widestbandwidth,butverycomplexdesign–Threepolesoneatorigin,onesetbyRPZ2&CP2andonebyRP1&CPZ1–TwozerosonesetbyCZ2&RPZ2andonebyRZ1&CPZ1ControlLoopUnderstanding:ControlLoopUnderstanding:CompensationNetworkTypeIIIAnalysisCompensationNetworkTypeIIIAnalysisControlLoopUnderstanding:ControlLoopUnderstanding:PowerStageloop+CompensationLoop=StableLoopPowerStageloop+CompensationLoop=StableLoop-60.0-50.0-40.0-30.0-20.0-10.00.010.020.030.01001000100001000001000000Frequency-HzGain-dBDoublepoleESRZeroESR=0.Slope=-40dB/decadeESR=0.0095Ohms.Slope=-20dB/decadeDoublezeroPole1Pole2fcofP1fP2fZ1,fZ2PowerStageLoop+PowerStageLoop+CompensationLoopCompensationLoop-60.00-50.00-40.00-30.00-20.00-10.000.0010.0020.0030.0040.001001000100001000001000000Frequency-HzGain-dBCompensationResponsePWM&LCResponse(ESR=0).PWM&LCResponse(ESR=0.0095)OverallSystemResponse(ESR=0)OverallSystemResponse(ESR=0.0095)GBWfco1fco2OutputcapacitorESRzeroFinalcurveFinalcurveStabilityDesignRules:1.Fcross-over=1/10~1/5Fsw2.Phase-MarginatFcro45degree3.Gain-MarginatFcro|-20dB|,thisvaluemustbenegativemeansnegativefeedback.4.Crossoverfrequencymeanstheunit-gainis1or0dBwhengaincurvecross-overthisfrequencyFcroFcroHeroPowerProductswithErrorAmplifierHeroPowerProductswithErrorAmplifierSimplifiedloopcompensationdesignSimplifiedloopcompensationdesignTPS54622TPS54622……………………Upto17Vin,6A,QFN14PackageUpto17Vin,6A,QFN14PackageTPS54521TPS54521……………………Upto17Vin,5A,QFN14PackageUpto17Vin,5A,QFN14PackageTPS54320TPS54320……………………Upto17Vin,3A,QFN14PackageUpto17Vin,3A,QFN14PackageTPS54(2/3)1TPS54(2/3)1………………Upto28Vin,2A~3A,SOICUpto28Vin,2A~3A,SOIC--8Package8PackageTPS54(0/1/2)40TPS54(0/1/2)40…….Upto42Vin,0.5A~2.5A,MSOP10Package.Upto42Vin,0.5A~2.5A,MSOP10PackageTPS54(0/1/2)60TPS54(0/1/2)60…….Upto60Vin,0.5A~2.5A,MSOP10Package.Upto60Vin,0.5A~2.5A,MSOP10Package•Synchronousbucksample:1)CheckthewaveformVDS(VPH)oflow-MOSFETQ2ofconverter2)Loadtransienttest(option)+LCoRVO+-VINQ1iQ2+VLQ2iQ