Prof. S. Ben-Yaakov , DC-DC Converters [4- 1] Forward and ...

1 1 Prof. S. Ben-Yaakov , DC-DC Converters [4- 1] Forward and flyback ( Converters with isolation) Transfer of DC current via Voltage transfer Magnetization inductance Transformer Reset of Forward Coupled Voltage transfer flyback with multiple Characteristics of FlybackProf. S. Ben-Yaakov , DC-DC Converters [4- 2]Is transfer of DC current possible?Iots1tLinRnV s2 IoVin1:nRLVoS1S22 Prof. S. Ben-Yaakov , DC-DC Converters [4- 3]Replacing S2by a DiodeIoVinD1:nRLVoS1 Prof. S. Ben-Yaakov , DC-DC Converters [4- 4]D1D2 LILICIRCR1:nVinSVoTForward :zT is a transformerzOutput section: BuckzBuck derivedForward Converter3 Prof.

2 S. Ben-Yaakov , DC-DC Converters [4- 5]tSONtVXtV2nVin 1D2VV TsOND1D2 LILICIRCR1:nVinSVoVXV2At steady state, over one switching cycle: ;LV0=oninonDVV0SS= =+ +;t)VnV(Sonoin +;t)V(Soffo Voltage transfer functionProf. S. Ben-Yaakov , DC-DC Converters [4- 6]Magnetization Inductance ProblemVLmt?VinSVin1:nLmideal4 Prof. S. Ben-Yaakov , DC-DC Converters [4- 7]Transformer ResetVinttofftonVintton)VV(inreset VLVL offinresetoninD)VV(DV =SVinLmVresetProf. S. Ben-Yaakov , DC-DC Converters [4- 8]Applying a Reset WindingonDninVnresetVoffD13 Reset RequirementsVresetSVinn1n2n3Lm1 VinILVresetONOFF5 Prof.

3 S. Ben-Yaakov , DC-DC Converters [4- 9]Applying same sourceonDninVoffDninV13>offDonDnn<13 VresetSVinn1n2n3 Prof. S. Ben-Yaakov , DC-DC Converters [4- 10]Assignment Given: <Don< will be the voltage stress on S?VresetSVinn1n2n36 Prof. S. Ben-Yaakov , DC-DC Converters [4- 11]Reset of ForwardCalculation of n3zCalculation can be done by looking at any of the windings n1, n2, n3D1D2 LILICIRCRD3n1n2n3 VinSProf. S. Ben-Yaakov , DC-DC Converters [4- 12]Fundamental requirement:n1 Lmn2n3ovwinding=zExample: Looking at n1S1S2t1nVtontoffS1S2ttontofftt1nVinVinV 31innnVS1=S2 LmI12 LmI7 Prof.

4 S. Ben-Yaakov , DC-DC Converters [4- 13]onin31offinDVnnDV onoff13 DDnn offoff13D1 Dnn S1S2t1nVtontoffS1S2ttontofftt1nVinVinV31 innnVS1=S2 LmI12 LmIVTProf. S. Ben-Yaakov , DC-DC Converters [4- 14]Voltage on switch when off in31insVnnVV+=]D1D1[VVmaxonmaxonins +=t1nVDonDoffinV31innnVVT8 Prof. S. Ben-Yaakov , DC-DC Converters [4- 15]21nnn=zprimary current is a reflection of I2 plus ImttontoffTSIpkI2ttoffI1pkInpk2 InSwitch CurrentD1D2 LILICIRCRD3n1n2n3 VinI1I2 SReset windingProf. S. Ben-Yaakov , DC-DC Converters [4- 16]Taking into account LmD1D2 LCRD3n1n2n3 VinILmI2 SLmtttILmI2nISI2n+ILm9 Prof.

5 S. Ben-Yaakov , DC-DC Converters [4- 17]Question 1: How does In3look ?tTS3nIIpk?toffQuestion 2: If Dmax= Calculate n1 Find maximum voltage on switchononin31inresetonon31D1 DVnnVVD1 Dnn == =Reset CurrentProf. S. Ben-Yaakov , DC-DC Converters [4- 18]Coupled inductorL1L2L1L2n1n222121nnLL =10 Prof. S. Ben-Yaakov , DC-DC Converters [4- 19]S1S2ttS1S2V1V2I1I21:1 Current in a Winding CAN be Interrupted !Prof. S. Ben-Yaakov , DC-DC Converters [4- 20]S1S2I1I21pkILV2LV12pkItStSttttAt transition2121pk2pk1pkpkININII==S1S2V1V2 I1I21:1(not in wires)Energy stored in core11 Prof.

6 S. Ben-Yaakov , DC-DC Converters [4- 21]Problem: Leakage inductance (will be discussed later)S1S2I1I21pkILV12pkItStSttttLnV22nI InI1I2121pkpkpkpk= = S1S2V1V2I1I21:nLCoupled windingsProf. S. Ben-Yaakov , DC-DC Converters [4- 22]110 VnV =220Vn1V=(negative voltage)S1V11:nS1V1V21:nV20S2V1V2V101:nD iode replace a switch12 Prof. S. Ben-Yaakov , DC-DC Converters [4- 23]Buck BoostPolarity Reversal0 DVDV offoonin=+offoninoDDVV =SVinDLCRVoProf. S. Ben-Yaakov , DC-DC Converters [4- 24]FlybackBuck BoostIsolated Back-BoostFlybackSVinDLCRVoSVinDCRVo13 Prof.

7 S. Ben-Yaakov , DC-DC Converters [4- 25] flyback convertertontoffD1CR1:nVinSVoCR1:nVinSVo nVinCR1:nVinSVoVonVonVinIProf. S. Ben-Yaakov , DC-DC Converters [4- 26]Voltage transfer functionThe average voltage methodVoltage across primaryV1tofft-VintonTsnVooffoonintnVtV = offooninDnVDV = offoninoDDnVV=D1CR1:nVinSVoV114 Prof. S. Ben-Yaakov , DC-DC Converters [4- 27]Voltage transfer functionThe I methodD1 CRVinSVoI1I2L1n1L2n2tonTstttI11I 1I 212 Inn;tLVntLVnInInoff2o2on1in12211= = offonoffonino2112 DDttVVLLnn==offonino22112 DDVV nnnn= offon12inoDDnnVV=Prof.

8 S. Ben-Yaakov , DC-DC Converters [4- 28] flyback with multiple outputsVinSD1Vo1D2Vo2C1R1R2C2n1n215 Prof. S. Ben-Yaakov , DC-DC Converters [4- 29]tontoff21o2o1 VnVn=VinVo1Vo2C1R1R2C2n1n2 VinVo1Vo2C1R1R2C2n1n2 FlybackProf. S. Ben-Yaakov , DC-DC Converters [4- 30]Characteristics of FlybackzIsolationzStep-up or Step-downzDiscontinuous current at input and output (Buck-Boost Derived)zMultiple outputs (economical)16 Prof. S. Ben-Yaakov , DC-DC Converters [4- 31]ExerciseV2TD = 0TF = = 10uPER = 20uV1 = 0TR = = 15 DbreakD1out_gnd0gateL2{L1*(n*n)}0RL{Load }drainV1{Vin}R410megout0C1220uIC = 6KK1 COUPLING = 1K_LinearL1 = l1L2 = l2 PARAM ET ERS:n = = 12 Load = 10L1 = 300u+-+-SbreakS1L1{L1}zFind by simulation Llkg and Lm of the magnetic body if k=.

9 9zCalculate Ap of magnetic element