LLC的原理与应用--课件

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1、LLC的原理与应用的原理与应用IndexvLLC简介简介v工作模式分析工作模式分析vLLC的特点的特点v3K LLC Demo Board介绍介绍v设计步骤设计步骤v与与Push-pull的对比的对比v损耗分析损耗分析v效率优化效率优化LLC简介简介-1LLC：三元件谐振半桥：三元件谐振半桥/全桥全桥v线路图线路图v变频工作，电压反馈变频工作，电压反馈v50Duty驱动驱动v副边不需电感副边不需电感LLC简介简介-2SRC电路与增益曲线电路与增益曲线vSRC电路的直流增益总是小于电路的直流增益总是小于1v轻载调整率，高的谐振能量，以及高输入电压时的较轻载调整率，高的谐振能量，以及高输入电压时的

2、较大关断电流大关断电流LLC简介简介-3Advantages of adding LmvCurrent LagvZVSvBoostvWide rangevBest use of resonant pointvHigh EfficiencyDrawbacksvIncreasing resonant tank circle currentvAdditional magnetic component,but easy to realize(integration)LLC简介简介-4工作在谐振频率时等效电路分析工作在谐振频率时等效电路分析v副边电阻折算到原边副边电阻折算到原边vLm被输出电压箝位被输出

3、电压箝位v电流滞后于电压电流滞后于电压v电容直流偏压电容直流偏压Vin-nVo=Vin/2vFHA approach(first harmonic approximation)LLC简介简介-5一些公式一些公式v存在存在2个谐振频率个谐振频率Fr1和和Fr2v其余归一化参数其余归一化参数LLC简介简介-6增益特性增益特性v在谐振点在谐振点Fr1，在所有负载条件下增益是固定的，在所有负载条件下增益是固定的v峰值增益在峰值增益在Fr2和和Fr1之间之间v存在存在ZCS区和区和ZVS区区需要限制最低频率v空载时，增益无法降得更低空载时，增益无法降得更低用跳周期解决Buck区区Boost区区谐振区谐振

4、区LLC简介简介-7MOSFET ZVS的实现的实现v在死区时间内需要有足够的电流抽取在死区时间内需要有足够的电流抽取MOSFET结电结电容上的能量；容上的能量；v死区时间结束时，电流不能过零；死区时间结束时，电流不能过零；v即使在无负载的情况下也能零电压开关；即使在无负载的情况下也能零电压开关；的含义的含义v谐振电感与励磁电感的比值：谐振电感与励磁电感的比值：Lr/Lmv越大，调节能力越强，增益曲线越陡峭越大，调节能力越强，增益曲线越陡峭v越大，增益范围越大越大，增益范围越大LLC简介简介-8不同时增益曲线的变化（图中不同时增益曲线的变化（图中k1/）LLC简介简介-9Diode ZCS的实

5、现的实现v能量传递过程能量传递过程vSpike&Ratingv损耗损耗v反向恢复反向恢复LLC简介简介-9副边副边Diode耐压耐压TopologyItemsReverseRecoveryVoltage stress for DiodeDC gainFlybackY4VoForwardY4VoCenter-tap FB/HBY4VoBridge rectifier FB/HBY2VoCenter-tap LLCN2VoMBridge rectifier LLCNVo2MLLC简介简介-10工作波形（谐振区）工作波形（谐振区）Q1电流电流流过流过Lr的电流的电流D1电流电流流过流过Lm的电流的电

6、流Q1导通时，导通时，Lr、Lm电流上升；电流上升；Q1关断时，关断时，Lr电流恰好等于电流恰好等于Lm电电流，流，D1 ZCS；死区时间内死区时间内Im对对Q1的结电容充电，的结电容充电，对对Q2的结电容放电；的结电容放电；Q2的体二极管会续流直到的体二极管会续流直到Q2被驱动被驱动导通导通,Q2 ZVS开通。开通。Q2先流过反向电流，再流正向电流，先流过反向电流，再流正向电流，工作模式与工作模式与Q1相同相同LLC拓扑形式拓扑形式分体电容分体电容分体电容分体电容&绕组绕组原边全桥原边全桥副边全桥副边全桥多路输出多路输出LLC的工作模式分析的工作模式分析谐振区、谐振区、Buck区、区、Boo

7、st区区v波形波形v分段介绍分段介绍v特点特点v等效电路等效电路v总结总结Q1 ONQ2 OFFQ1 OFFQ2 ONQ1 OFFQ2 ONOperating Sequence at resonance(Phase 1/6)VinVoutQ1Q2LsLpCrn:1:1D1D2Coss1Coss2nQ1 is ON,Q2 is OFFnD1 is ON,D2 is OFFnLp is dynamically shorted.nCr resonates with Ls,fr1 appearsnI(Ls)flows through Q1s RDS(on)back to Vin(Q1 is worki

8、ng in the 3rd quadrant)nPhase ends when I(Ls)=0Cout1/6VgVcI(lp)I(ls)ImosIdQ1 ONQ2 OFFQ1 OFFQ2 ONQ1 OFFQ2 ONOperating Sequence at resonance(Phase 2/6)2/6VinVoutQ1Q2LsLpCrn:1:1D1D2Coss1Coss2nD1 is ON,D2 is OFFnLp is dynamically shortednCr resonates with Ls,fr1 appearsnEnergy is taken from Vin and goes

9、 to VoutnPhase ends when Q1 is switched offCoutVgVcImosIdI(lp)I(ls)Q1 ONQ2 OFFQ1 OFFQ2 ONQ1 OFFQ2 ONOperating Sequence at resonance(Phase3/6)3/6VinVoutQ1Q2LsLpCrn:1:1D1D2Coss1Coss2nQ1 and Q2 are OFF(dead-time)nD1 and D2 are OFFntransformers secondary is opennI(Ls+Lp)charges COSS1 and discharges COSS

10、2,until V(COSS2)=0nPhase ends when Q2 is switched onCoutVgVcI(lp)I(ls)ImosIdQ1 ONQ2 OFFQ1 OFFQ2 ONQ1 OFFQ2 ONOperating Sequence at resonance(Phase 4/6)4/6VinVoutQ1Q2LsLpCrn:1:1D1D2Coss1Coss2nQ1 is OFF,Q2 is ONnD1 is OFF,D2 is ONnLp is dynamically shortenOutput energy comes from Cr and LsnPhase ends

11、when I(Ls)=0CoutVgVcI(lp)I(ls)ImosIdOperating Sequence at resonance(Phase 5/6)Q1 ONQ2 OFFQ1 OFFQ2 ONQ1 OFFQ2 ON5/6VinVoutQ1Q2LsLpCrn:1:1D1D2Coss1Coss2nQ1 is OFF,Q2 is ONnD1 is OFF,D2 is ONnLp is dynamically shortednOutput energy comes from Cr and LsnPhase ends when Q2 is switched offCoutVgVcI(lp)I(l

12、s)ImosIdQ1 ONQ2 OFFQ1 OFFQ2 ONQ1 OFFQ2 ONOperating Sequence at resonance(Phase 6/6)VinVoutQ1Q2LsLpCrn:1:1D1D2Coss1Coss2nQ1 and Q2 are OFF(dead-time)nD1 and D2 are OFFntransformers secondary is opennI(Ls+Lp)charges COSS2 and discharges COSS1,until V(COSS2)=Vin;nPhase ends when Q1 is switched onCout6/

13、6VgVcI(lp)I(ls)ImosId Waveforms at resonance(fsw=fr1)Gate-drivesignalsTransformercurrentsDead-timeDiodevoltagesDiodecurrentsMagnetizing current is triangularOutput currentTank circuit current is sinusoidalCCM operationHB mid-pointVoltageResonant capvoltageVgOperating Sequence above resonance(Phase1/

14、6)Q1 ONQ2 OFFQ1 OFFQ2 ONQ1 OFFQ2 ON1/6VinVoutQ1Q2LsLpCrn:1:1D1D2Coss1Coss2nQ1 is OFF,Q2 is ONnD1 is OFF,D2 is ONnLp is dynamically shortedCr resonates with Ls,fr1 appearsnOutput energy comes from Cr and LsnPhase ends when Q2 is switched offCoutVgVcI(lp)I(ls)ImosIdOperating Sequence above resonance(P

15、hase 2/6)VinVoutQ1Q2LsLpCrn:1:1D1D2Coss1Coss2nQ1 and Q2 are OFF(dead-time)nD1 and D2 are OFFntransformers secondary is openV(D2)reverses as I(D2)goes to zeronPhase ends when Q1 is switched onCoutQ1 ONQ2 OFFQ1 OFFQ2 ONQ1 OFFQ2 ON2/6VgVcI(lp)I(ls)ImosIdOperating Sequence above resonance(Phase 3/6)VinV

16、outQ1Q2LsLpCrn:1:1D1D2Coss1Coss2nQ1 is ON,Q2 is OFFnD1 is ON,D2 is OFFnLp is dynamically shortednCr resonates with Ls,fr1 appearsnPhase ends when I(Ls)=0CoutQ1 ONQ2 OFFQ1 OFFQ2 ONQ1 OFFQ2 ON3/6VgVcI(lp)I(ls)ImosIdQ1 ONQ2 OFFQ1 OFFQ2 ONQ1 OFFQ2 ONOperating Sequence above resonance(Phase4/6)4/6VinVout

17、Q1Q2LsLpCrn:1:1D1D2Coss1Coss2nQ1 is ON,Q2 is OFFnD1 is ON,D2 is OFFnLp is dynamically shorted Cr resonates with Ls,fr1 appearsnEnergy is taken from Vin and goes to VoutnPhase ends when Q1 is switched offCoutVgVcI(lp)I(ls)ImosIdQ1 ONQ2 OFFQ1 OFFQ2 ONQ1 OFFQ2 ONOperating Sequence above resonance(Phase

18、 5/6)5/6VinVoutQ1Q2LsLpCrn:1:1D1D2Coss1Coss2nQ1 and Q2 are OFF(dead-time)nD1 and D2 are OFFntransformers secondary is opennPhase ends when Q2 is switched onCoutVgVcI(lp)I(ls)ImosIdQ1 ONQ2 OFFQ1 OFFQ2 ONQ1 OFFQ2 ONOperating Sequence above resonance(Phase 6/6)6/6VinVoutQ1Q2LsLpCrn:1:1D1D2Coss1Coss2nQ1

19、 is OFF,Q2 is ONnD1 is OFF,D2 is ONnLp is dynamically shorted.nCr resonates with Ls,fr1 appearsnOutput energy comes from Cr and LsnPhase ends when I(Ls)=0,Phase 1 startsCoutVgVcI(lp)I(ls)ImosId Waveforms above resonance(fsw fr1)Gate-drivesignalsTransformercurrentsDead-timeDiodevoltagesDiodecurrentsM

20、agnetizing current is triangularOutput currentTank circuit currentCCM operationHB mid-pointVoltageResonant capvoltageSinusoid f=fr1 Linear portionVgOperating Sequence below resonance(Phase 1/8)Q1 ONQ2 OFFQ1 OFFQ2 ONQ1 OFFQ2 ON1/8VinVoutQ1Q2LsLpCrn:1:1D1D2Coss1Coss2nQ1 is OFF,Q2 is ONnD1 is OFF,D2 is

21、 ON;nLp is dynamically shortednCr resonates with Ls,fr1 appearsnOutput energy comes from Cr and LsnPhase ends when I(D2)=0CoutVgVcI(lp)I(ls)ImosIdOperating Sequence below resonance(Phase 2/8)Q1 ONQ2 OFFQ1 OFFQ2 ONQ1 OFFQ2 ON2/8VinVoutQ1Q2LsLpCrn:1:1D1D2Coss1Coss2nQ2 is ON,Q1 is OFFnD1 and D2 are OFF

22、ntransformers secondary is opennCr resonates with Ls+Lp,fr2 appearsnOutput energy comes from CoutnPhase ends when Q2 is switched offCoutVgVcI(lp)I(ls)ImosIdOperating Sequence below resonance(Phase 3/8)Q1 ONQ2 OFFQ1 OFFQ2 ONQ1 OFFQ2 ON3/8VinVoutQ1Q2LsLpCrn:1:1D1D2Coss1Coss2nQ1 and Q2 are OFF nD1 and

23、D2 are OFFntransformers secondary is opennPhase ends when Q1 is switched onCoutVgVcI(lp)I(ls)ImosIdOperating Sequence below resonance(Phase 4/8)Q1 ONQ2 OFFQ1 OFFQ2 ONQ1 OFFQ2 ON4/8VinVoutQ1Q2LsLpCrn:1:1D1D2Coss1Coss2nQ1 is ON,Q2 is OFFnD1 is ON,D2 is OFFnLp is dynamically shortednCr resonates with L

24、s,fr1 appearsnEnergy is recirculating into VinnPhase ends when I(Ls)=0CoutVgVcI(lp)I(ls)ImosIdOperating Sequence below resonance(Phase 5/8)Q1 ONQ2 OFFQ1 OFFQ2 ONQ1 OFFQ2 ON5/8VinVoutQ1Q2LsLpCrn:1:1D1D2Coss1Coss2nQ1 is ON,Q2 is OFFnD1 is ON,D2 is OFFnLp is dynamically shortednCr resonates with Ls,fr1

25、 appearsnEnergy is taken from Vin and goes to VoutnPhase ends when I(D1)=0CoutVgVcI(lp)I(ls)ImosIdOperating Sequence below resonance(Phase 6/8)Q1 ONQ2 OFFQ1 OFFQ2 ONQ1 OFFQ2 ON6/8VinVoutQ1Q2LsLpCrn:1:1D1D2Coss1Coss2nQ1 is ON,Q2 is OFFnD1 and D2 are OFFntransformers secondary is opennCr resonates wit

26、h Ls+Lp,fr2 appearsnOutput energy comes from CoutnPhase ends when Q1 is switched offCoutVgVcI(lp)I(ls)ImosIdOperating Sequence below resonance(Phase 7/8)Q1 ONQ2 OFFQ1 OFFQ2 ONQ1 OFFQ2 ON7/8VinVoutQ1Q2LsLpCrn:1:1D1D2Coss1Coss2nQ1 and Q2 are OFF nD1 and D2 are OFFntransformers secondary is opennPhase

27、ends when Q2 is switched onCoutVgVcI(lp)I(ls)ImosIdOperating Sequence below resonance(Phase 8/8)Q1 ONQ2 OFFQ1 OFFQ2 ONQ1 OFFQ2 ON8/8VinVoutQ1Q2LsLpCrn:1:1D1D2Coss1Coss2nQ1 is OFF,Q2 is ONnD1 is OFF,D2 is ONnLp is dynamically shortednCr resonates with Ls,fr1 appearsnOutput energy comes from Cr and Ls

28、nPhase ends when I(Ls)=0,Phase 1 startsCoutVgVcI(lp)I(ls)ImosIdGate-drivesignalsHB mid-pointVoltageResonant capvoltageTransformercurrentsDead-timeDiodevoltagesDiodecurrentsMagnetizing currentOutput currentTank circuit currentWaveforms below resonance(fsw fr1)Sinusoid f=fr2DCM operationSinusoid f=fr2

29、LLC工作模式总结工作模式总结三个工作区都能实现三个工作区都能实现MOSFET ZVS，Diode ZCSBOOST区区v需要限制最低频率需要限制最低频率v部分时间没有向副边传递能量，利用率低，因而效率稍差部分时间没有向副边传递能量，利用率低，因而效率稍差谐振区谐振区v效率最高，工作特性最好效率最高，工作特性最好Buck区区vMOSFET关断损耗增加关断损耗增加vDiode反向恢复稍大反向恢复稍大v空载需要跳周空载需要跳周Features Of LLCZVS for primary switches in full load range，ZCS for secondary rectifiers

30、No need of output choke inductorMagnetic integration helps reduction of the volumeLow voltage stress of secondary diodeLess reverse recoveryHigh efficiencyLow EMILLC的主要应用的主要应用最佳应用：输入高压最佳应用：输入高压400V左右，输出左右，输出50V左右左右v前级接前级接PFC时，电压较为稳定，多数时间在谐振区时，电压较为稳定，多数时间在谐振区附近工作附近工作vMOSFET的的Rds适当，驱动难度不大适当，驱动难度不大v电感、

31、变压器便于设计电感、变压器便于设计vDiode可用可用Schottkyv谐振电容适当谐振电容适当磁集成：磁集成：600W以内以内v磁芯和磁芯和Bobbin难选，但绕制工艺简单难选，但绕制工艺简单v漏感和励磁电感比例不能精确控制，但影响不大漏感和励磁电感比例不能精确控制，但影响不大LLC的主要应用的主要应用高端应用高端应用v工频纹波大是一个很突出的问题工频纹波大是一个很突出的问题由于电压环控制的原因，工频纹波很难抑制，工频补偿可由于电压环控制的原因，工频纹波很难抑制，工频补偿可以较为有效的解决这一问题以较为有效的解决这一问题v副边同步整流也是一个难点副边同步整流也是一个难点准确确定同步MOSFE

32、T的开通、关断时间非常困难；目前较为传统的方法是采样SR MOSFETs DS电压控制开关(1168)；另可以采样副边电流控制(Hindenburg2)；原副边同驱(Houston)。v工作频率高时增益反转现象工作频率高时增益反转现象由寄生参数引起,加强工艺,高频限制；LLC在低压大电流时的应用在低压大电流时的应用在低压大电流输入、高压输出时：在低压大电流输入、高压输出时：v不能磁集成不能磁集成v最好采用原边全桥最好采用原边全桥v注意死区时间对注意死区时间对ZVS的影响的影响v输出输出Diode的反向恢复是一个问题的反向恢复是一个问题v效率有优势效率有优势vEMI性能好性能好LLC应用问题应用

33、问题磁集成磁集成v磁集成的方法磁集成的方法LLC 需要一个相对大的Lr，一般采用一种可组合线轴线圈数和绕线结构是决定Lr大小的主要因素变压器芯的气隙长度不会影响Lr太多通过调整气隙长度却可以轻松控制Lm分立磁性元件分立磁性元件v磁性元件体积大磁性元件体积大v仍旧可以采用仍旧可以采用TX励磁电感作为励磁电感作为Lmv容易控制感量与工艺容易控制感量与工艺v适合大功率应用适合大功率应用3K LLC Demo BoardCircuit diagram3K LLC Demo BoardPhoto of the demo board（Second Edition）vThe latest edition i

34、s planned carefully方案简介方案简介采用采用L6599模拟控制模拟控制原边全桥原边全桥LLC，副边中心抽头全桥整流，副边中心抽头全桥整流隔离驱动隔离驱动MOSFET：IPP075N15N3Diode：APT15DQ100KCr采用高压薄膜电容采用高压薄膜电容分离分离Lr与与TX（Lm）性能描述性能描述按照输入电压按照输入电压80-110V设计，输出功率设计，输出功率2700W；Peak Efficiency：97.4DC load；Full Load Efficiency：97.0DC load；全桥全桥LLC与半桥与半桥LLC的区别的区别变压器匝比比半桥增大一倍；变压器匝比

35、比半桥增大一倍；Lr、Lm是半桥的是半桥的4倍，倍，Cr是半桥的是半桥的1/4保证保证Q值不变；值不变；需要隔离驱动；需要隔离驱动；变压器匝数增多，线径变小；变压器匝数增多，线径变小；MOSFET数量由数量由2个变为个变为4个个在低压大电流时，在低压大电流时，半桥半桥LLC也需要用也需要用4个；都用个；都用4个个MOSFET时，时，二者损耗相当；二者损耗相当；全桥全桥LLC整体电流应力小；整体电流应力小；设计步骤设计步骤-1注意：原边为全桥注意：原边为全桥LLC，副边两路折算成一路，副边两路折算成一路1.列出设计参数与规格要求列出设计参数与规格要求vVin（最小、最大、常压）、（最小、最大、常

36、压）、Vout、Pout、Fs（常压（常压时的工作频率）时的工作频率）v根据常压与输出电压，结合所选拓扑求变压器匝比根据常压与输出电压，结合所选拓扑求变压器匝比NN Vin/Vout(全桥)（副边单路为Center-Tap形式）v初选初选Lr与与Lm的比值的比值，在在0.2-0.35之间较好之间较好v求出求出Re：2.确定最低输入电压时需要的增益确定最低输入电压时需要的增益MmaxvMmaxN*Vout/Vin-min（与半桥（与半桥LLC不同）不同）3.确定确定Q值值v从增益曲线中找到与从增益曲线中找到与Mmax有交点的有交点的Q值即为值即为Qmaxv也可以根据下式计算也可以根据下式计算Qm

37、axv选取选取Q90*Qmaxv根据下式求出根据下式求出Lr、Cr、Lm设计步骤设计步骤-2设计步骤设计步骤-34.确认是否满足确认是否满足ZVS条件条件vMOSFET关断时的电流要能抽走其寄生电容关断时的电流要能抽走其寄生电容Coss上的能量上的能量v死区时间内电流不能过零死区时间内电流不能过零5.通过通过IC参数设定参数设定Fmin与跳周期时需要的频率与跳周期时需要的频率6.变压器、电感设计变压器、电感设计7.功率器件、谐振电容选取功率器件、谐振电容选取8.反馈设计、驱动设计反馈设计、驱动设计9.IC周边参数选取周边参数选取与与Push-pull对比：损耗计算及对比对比：损耗计算及对比PU

38、SH-PULLLLC备备 注注MOSFET导通损耗65W35WMOSFET切换损耗未计算未计算LLC MOSFET切换损耗很小Diode导通损耗 20W21WDiode切换损耗未计算未计算LLC Diode切换损耗很小变压器铁损9W11W变压器铜损46W10WLLC的电流谐波少，并进行了绕组优化电感铁损未计算5W电感铜损4W2WSnubber损耗未计算无LLC谐振电容损耗很小计算总损耗144W84W测试总损耗173W(2300W)83W(2700W)Push-pull未能带更多负载损耗百分比7%3%uLLC的近似正弦波形对开关管、磁性元件均有利；的近似正弦波形对开关管、磁性元件均有利；u实际测

39、试损耗从实际测试损耗从173W下降到下降到83W，降低了，降低了52，且，且LLC在输出功率更大条件下测试在输出功率更大条件下测试与与Push-pull对比：效率曲线对比对比：效率曲线对比DC Source输入，电阻负载时，单级效率：输入，电阻负载时，单级效率：Push-pull效效率率与与Push-pull对比：效率曲线对比对比：效率曲线对比电池输入时，带逆变，整机效率：电池输入时，带逆变，整机效率：Push-pull效率效率与与Push-pull对比：效率曲线对比对比：效率曲线对比DC Source输入，电阻负载时，单级效率：输入，电阻负载时，单级效率：LLC效率效率没有电压跟随没有电压跟

40、随与与Push-pull对比：效率曲线对比对比：效率曲线对比电池输入时，带逆变，整机效率：电池输入时，带逆变，整机效率：LLC效率效率测试波形测试波形Boost区区Buck区区MOS电压电压Diode电压电压Lr电流电流Lr电流电流MOS电压电压Diode电压电压带逆变器时工作模式分析带逆变器时工作模式分析在工频半波内相当于单边带载在工频半波内相当于单边带载对交叉调整率要求较高对交叉调整率要求较高效率优化效率优化在带逆变负载时效率下降在带逆变负载时效率下降1.6；输入为电池时，效率会提升输入为电池时，效率会提升0.4；反馈环路调慢有利于稳定工作频率，进而减小频反馈环路调慢有利于稳定工作频率，进而减小频率变化带来的效率损失；率变化带来的效率损失；输出电压跟随时，能保证效率最高点差异不大；输出电压跟随时，能保证效率最高点差异不大；v电压跟随可以使平均效率提高，延长电池时间电压跟随可以使平均效率提高，延长电池时间v输出最高电压应该以后级逆变能承受的电压为准输出最高电压应该以后级逆变能承受的电压为准v可以通过调整变压器匝比来调整跟随电压的最高值可以通过调整变压器匝比来调整跟随电压的最高值