1、开关电源功率电路分析要点开关电源功率电路分析要点1.电容的电压不能突变,电感的电流不能突变2.流经电容的电流平均值为零,电感两端电压的平均值为零3.理想变压器电压与匝数成比且同名同极性,电流与匝数成反比且点进点出4.电容恒流充电的公式为 ,电感恒压储能的公式为5.变压器与电感的伏秒积必须平衡TIUC*TUIL*Buck-Boost电路工作原理:电路工作原理:VinVoDLIoS1S1S2ULILVin-VooIIoD1-DT根据L的伏秒平衡原则:Vin*DT=(Vo+2Vd)*(1-D)TVo=Vin*D/(1-D)-2VdL*Io=(Vo-2Vd)(1-D)TVds1根据L在(1-D)T时间
2、的基本方程:Io=(Vo-2Vd)(1-D)T/LDS2Vds2VinVo00.10.20.30.40.50.60.70.80.91012345678910Vo D()DVo/Vin=D/(1-D)Buck-Boost电路的输入输出关系:电路的输入输出关系:三种基本的非隔离开关电源:三种基本的非隔离开关电源:VinVoLIoSDVinVoDLIoS1DS2VinVoDLIoSVo=Vin*D/(1-D)Vo=Vin*DVo=Vin/(1-D)VoVin,升压型电路VoVin,当DVin 当D0.5 升降压型电路三种基本的隔离开关电源:三种基本的隔离开关电源:VinVoSLmDVinVoLSD1
3、D2VinVoLS1D1D2S2正激型变换器反激型变换器桥式变换器反激变换器(反激变换器(Flyback)工作原理工作原理(电流连续模式):(电流连续模式):VgsIDVdsD1-DTIpIoVinVin+nV o根据变压器的伏秒平衡:ImIoVinVoGDSLmDn:1TDnVoDTVin)1(*)1(*DnDVinVoCoVLVin-nVonVoVinVds)1(DVinVdsID-p反激变换器(反激变换器(Flyback)工作原理工作原理(电流断续模式):(电流断续模式):VgsIDVdsD1-DTIoVinVin+nV o根据变压器的伏秒平衡:ImIoVinVoGDSLmDn:1)1(
4、*DnDVinVoCoVLVin-nVoID-p-nVoVoVo TRVoLmIp2221根据能量守恒:LmVinDTIpVinDLmRTVo2反激变换器(反激变换器(Flyback)工作原理:工作原理:VgsIDVdsD1-DTIpIoVinVin+nV oImVrVLVin-nVo221221LkIpCdsVr nIIppDID-p21DopDIDIIVr=?IoVinVoGDSLmDn:1LkCoLmTDVoID/)1(IpCdsLkVr*反激变换器(反激变换器(Flyback)工作原理:工作原理:IoVinVoGDSLmDn:1LkCoVcVcRPloss=(Vc-Vin)2/RGDS
5、LkVcRPloss=(Vc)2/R反激变换器(反激变换器(Flyback)工作原理:工作原理:VgsIDVdsD1-DTIpIoVinVin+nV oImVrICoID-pVo=?IoVinVoGDSLmDn:1LkCo)1/(DIIIopDCo-IoVoDTIVCOOCDTIVOO/根据Co在DT时间的基本方程:反激变换器(反激变换器(Flyback)工作原理:工作原理:VinVo1GLmNpLkVo2Ns2Ns1多路输出的反激变换器:多路输出的反激变换器:)1(*11DNpDVinNsVo)1(*22DNpDVinNsVo减小交叉调整率的措施:减小交叉调整率的措施:1.尽量减少两个绕组之
6、间的漏感。2.在辅助输出一路中加入尖峰抑制器(饱和电感)3.主路输出工作于电流连续模式。4.采用双路加权反馈的控制方式反馈控制反激变换器(反激变换器(Flyback)特征总结:特征总结:VinVo1GLmNpLkVo2Ns2Ns1缺点:缺点:1.输出纹波电流大。2.输出控制特性非线性。3.通常需要辅助的吸收回路。4.转换效率较低。反馈控制优点:优点:1.电路简单。2.输入电压范围广。3.容易实现多路输出。谐振复位正激变换器(谐振复位正激变换器(Resonant Reset Forward):Ion:1VinVoLoGDSVgsILVdsD1-DTIpVLIoVin/n-Vo-VoImVinIL
7、 ILLmLkCrt0t1 t2 t3t4Ipt0,t1t5LmVinDTIm/LoDTVonVinIL/)/(LmPInII谐振复位正激变换器(谐振复位正激变换器(Resonant Reset Forward):Ion:1VinVoLGDSVgsILVdsD1-DTIpVLIoVin/n-Vo-VoImVinIL ILLmLkCrt0t1 t2 t3t4Ipt1,t2t5LmLkIIVVmpc211VcV谐振复位正激变换器(谐振复位正激变换器(Resonant Reset Forward):Ion:1VinVoLGDSVgsILVdsD1-DTIpVLIoVin/n-Vo-VoImVinIL
8、 ILLmLkCrt0t1 t2 t3t4Ipt2,t3t51VcVcVrminCLDTV2谐振复位正激变换器(谐振复位正激变换器(Resonant Reset Forward):Ion:1VinVoLGDSVgsILVdsD1-DTIpVLIoVin/n-Vo-VoImVinIL ILLmLkCrt0t1 t2 t3t4Ipt3,t4t5LmCrtt 14Lm,Cr的选取原则:22max2)1(1*TDCrLm谐振复位正激变换器(谐振复位正激变换器(Resonant Reset Forward):Ion:1VinVoLGDSVgsILVdsD1-DTIpVLIoVin/n-Vo-VoImVi
9、nIL ILLmLkCrt0t1 t2 t3t4Ipt4,t5t5(Vin/n-Vo)DT=Vo(1-D)T根据电感的伏秒平衡:Vo=VinD/n谐振复位正激变换器(谐振复位正激变换器(Resonant Reset Forward)特征:特征:VinVoCr缺点:缺点:1.原边开管电压应力较高。2.谐振电容的损耗大。3.宽范围输入效率很难兼顾。优点:优点:1.电路简单。2.线性输出控制特性。3.不需要辅助的吸收回路。VinVoCrVinVoCrS1,S2VpVinDVds100 50%Duty Cycle ZVS for Low side switchExcitingResetResonant
10、 Reset Dual Switch ForwardVinLS2S1Sa1CrD1D2有源钳位正激变换器(有源钳位正激变换器(Active Clamped Forward):Ion:1VinVoLoGDSSaILVdsDTIpVTIoVin/n-Vc/nImVinIL ILLmLkCrt0t1 t2 t3t4Ipt0,t1t5LmVinDTIm/LoDTVonVinIL/)/(LmPInIIS1S1Sa1-D+VT-有源钳位正激变换器(有源钳位正激变换器(Active Clamped Forward):Ion:1VinVoLoGDSSaILVdsDIpVTIoVin/n-Vc/nImVinIL
11、 ILLmLk-Vc+t0t1 t2 t3t4Ipt1,t2t5LkIpttVcIm)()12(S1S1Sa1-D+VT-VcLknIott/*)/()12(1td2td*副边电压的死区跟Lk和Io有关,跟原边开管的死区无关有源钳位正激变换器(有源钳位正激变换器(Active Clamped Forward):Ion:1VinVoLoGDSSaILVdsDIpVTIoVin/n-Vc/nImVinIL ILLmLk-Vc+t0t1 t2 t3t4Ipt2,t3t5S1S1Sa1-D+VT-)12(1tttd1td2tdSa在零电压条件下开通*原边开管的死区时间需满足:有源钳位正激变换器(有源钳
12、位正激变换器(Active Clamped Forward):Ion:1VinVoLoGDSSaILVdsDIpVTIoVin/n-Vc/nImVinIL ILLmLk-Vc+t0t1 t2 t3t4Ipt3,t4t5S1S1Sa1-D+VT-1td2td激磁电流反向,变压器被复位LmTDVcIm/)1(有源钳位正激变换器(有源钳位正激变换器(Active Clamped Forward):Ion:1VinVoLoGDSSaILVdsDIpVTIoVin/n-Vc/nImVinIL ILLmLk-Vc+t0t1 t2 t3t4Ipt4,t5t5S1S1Sa1-D+VT-1td2td激磁电流对主
13、开关的输出电容放电。t6=t0有源钳位正激变换器(有源钳位正激变换器(Active Clamped Forward):Ion:1VinVoLoGDSSaILVdsDIpVTIoVin/n-Vc/nImVinIL ILLmLk-Vc+t0t1 t2 t3t4Ipt5,t6t5S1S1Sa1-D+VT-1td2tdt5时刻副边二极管钳位主开关的输出电容放电结束。t6时刻新的周期开始t6=t0有源钳位正激变换器(有源钳位正激变换器(Active Clamped Forward):Ion:1VinVoLoGDSSaILVdsDIpVTIoVin/n-Vc/nImVinIL ILLmLk-Vc+t0t1
14、 t2 t3t4Ipt5S1S1Sa1-D+VT-1td2tdt6=t0(Vin/n-Vo)DT=Vo(1-D)T根据电感的伏秒平衡:Vo=VinD/nVinDT=Vc(1-D)T根据变压器的伏秒平衡:Vc=VinD/(1-D)Vds=Vc+VinVds=Vin/(1-D)有源钳位正激变换器(有源钳位正激变换器(Active Clamped Forward):00.10.20.30.40.50.60.70.80.91012345678910Vc D()Vds D()DVc=VinD/(1-D)Vds=Vin/(1-D)Vin有源钳位正激变换器(有源钳位正激变换器(Active Clamped
15、Forward)特征:特征:VinVoVinVoVinVoSaSaSa缺点:缺点:1.钳位电压建立较慢,启动过程变压器易偏磁。2.对输入电压的动态响应慢。优点:优点:1.变压器最优化复位(电压应力低)。2.输入电压范围宽。3.线性输出控制特性。4.不需要辅助的吸收回路。有源钳位正激变换器(有源钳位正激变换器(Active Clamped Forward):Asymmetrical Full Bridge DC/DC ConverterVinVoLS1D1D2S2半桥变换器桥式变换器(桥式变换器(Bridge Type Converter):VinVoLS1D1D2S2全桥变换器VinVoLS1
16、D1D2S2推挽变换器VinVoS1D2S2半桥变换器(倍流整流)VinVoLoS1D1D2S2桥式变换器(桥式变换器(Bridge Type Converter):n:1+1LmLkIpIoCBVTS1ILVds1DIpVTIoVin/2n-Vin/2nImVinIL t0t1t2t3 t4 t5S2Dt6=t0T/2T/2Vct0,t1变换器正半周工作,Ip,Im增加;Vc减少。LmDTVinIm/2)12/()/(CDTnIoVcC1C1VinVoLoS1D1D2S2桥式变换器(桥式变换器(Bridge Type Converter):n:1+1LmLkIpIoBVTS1ILVds1DI
17、pVTIoVin/2n-Vin/2nImVinIL t0t1t2t3 t4 t5S2Dt6=t0T/2T/2VcC1CC1Vin/2t1,t2S1关断,变压器副边续流,原边漏感能量被S2体二极管钳位。VinVoLoS1D1D2S2桥式变换器(桥式变换器(Bridge Type Converter):n:1+1LmLkIpIoBVTS1ILVds1DIpVTIoVin/2n-Vin/2nImVinIL t0t1t2t3 t4 t5S2Dt6=t0T/2T/2VcC1CC1Vin/2t2,t3S1,S2全部关断,变压器副边续流,Lm保持不变,D1,D2电流之差为Lm。VinVoLoS1D1D2S2
18、桥式变换器(桥式变换器(Bridge Type Converter):n:1+1LmLkIpIoABS1ILVds1DIpVTIoVin/2n-Vin/2nImVinIL t0t1t2t3 t4 t5S2Dt6=t0T/2T/2Vin/2VTVct3,t4变换器负半周工作,Ip,Im减少;Vc增加。LmDTVinIm/2)12/()/(CDTnIoVc VinVoLoS1D1D2S2桥式变换器(桥式变换器(Bridge Type Converter):n:1+1LmLkIpIoABS1ILVds1DIpVTIoVin/2n-Vin/2nImVinIL t0t1t2t3 t4 t5S2Dt6=t
19、0T/2T/2Vin/2VTVct4,t5S2关断,变压器副边续流,原边漏感能量被S1体二极管钳位。VinVoLoS1D1D2S2桥式变换器(桥式变换器(Bridge Type Converter):n:1+1LmLkIpIoBVTS1ILVds1DIpVTIoVin/2n-Vin/2nImVinIL t0t1t2t3 t4 t5S2Dt6=t0T/2T/2VcC1CC1Vin/2t5,t6S1,S2全部关断,变压器副边续流,Lm保持不变,D1,D2电流之差为Lm。t0,t1LoDTVonVinIL/)2(t1,t3LoTDVoIL/)2/1(DnVinVo 5.0DVinVoLoS1D1D2
20、S2桥式变换器(桥式变换器(Bridge Type Converter)特征:特征:n:1+1LmLkIpIoBVTC1CC1DnVinVo 5.0DLoTDVoIL/)2/1()12/()/(CDTnIoVc 缺点:缺点:1.变压器结构复杂。2.输入电压范围较小。优点:优点:1.变压器正负工作,不需要辅助的复位电路。2.输出纹波频率是开关频率的两倍,所需电感量小。3.线性输出控制特性。4.电路平衡对称。几种隔离式变换器之比较:几种隔离式变换器之比较:变压器复位方式原边开管电压应力输出特性占空比范围输出纹波频率输出纹波电流适用范围反激输出电压复位Vds=Vin/(1-D)0D1f小功率,宽范围输入,多路输出谐振复位正激谐振电容电压复位Vds=Vin+Vc0D1f小功率,低电压输入有源钳位正激钳位电容电压复位Vds=Vin/(1-D)0D1f中小功率,宽范围输入,高效率半桥正负半周工作,自动复位Vin0D0.52f较大功率,较小输入范围,快速响应)1(DnVinDVonVinDVo nVinDVo nVinDVo DIIoo1LoTDVIoo)1(LoTDVIoo)1(LoTDVIoo2)21(