江苏宏微科技股份有限公司 Power for the Better同步整流技术及主要拓扑电路宏微科技市场部2015-9-16Contents• 同步整流电路概述 • 典型电路及其特点 • 损耗分析 • 同步整流电路中常见问题 • MOSFET选型设计参考Power for the Better1 CONFIDENTIAL力求更好Contents• 同步整流技术概述 • 典型电路及其特点 • 损耗分析 • 同步整流电路中常见问题 • MOSFET选型设计参考Power for the Better2 CONFIDENTIAL力求更好同步整流技术概述由于中低压MOSFET具有很小的导通电阻,在有电流通过时产生的电压降很 小,可以替代二极管作为整流器件,可以提高变换器的效率。
diodeMOSFETMOSFET作整流器时,栅源极间电压必须与被整流电压的相位保持同步关系才 能完成整流功能,故称同步整流技术。
MOSFET是电压控制型开关器件,且没有反向阻断能力,必须在其栅-源之 间加上驱动电压来控制器漏-源极之间的导通和关断。
这是同步整流设计的难 点和重点。
根据其控制方式,同步整流的驱动电路分为 •自驱动方式; • 独立控制电路他驱方式; • 部分自驱+部分他驱方式结合;Power for the Better3 CONFIDENTIAL力求更好Contents• 同步整流技术概述 • 典型电路及其特点 • 损耗分析 • 同步整流电路中常见问题 • MOSFET选型设计参考Power for the Better4 CONFIDENTIAL力求更好典型电路及其特点1u 2u L1 TX1 1m C1 P1 S1 2 R1 P1 S1 D1N4148 D2 TX1 1m C1 L1 2 R1DC-AC ConverterDC-AC ConverterD1N4148 D1 S2 1u 2uL2L2主变压器副边绕组自驱动 自驱同步整流电路辅助绕组自驱动优点: 电路相对简单,可靠性较高; 成本低; 当采用辅助绕组时,不受主绕组输出电压限制; 在有源钳位正激,双管正激,谐振复位正激,不对称半桥拓扑应用广 泛。
Power for the Better5 CONFIDENTIAL力求更好典型电路及其特点4u4uL4L4 TX2TX2 1m C2 2 R2P1S1 1m C2 2 R2P1S1DC-AC ConverterDC-AC ConverterS2S3主变压器副边绕组自驱动 辅助绕组自驱动 自驱同步整流电路缺点: 驱动幅值随占空比变化较大;需要有额外的限幅电路; 主变压器提前复位时,没有驱动信号,需要增加栅压保持电路; 主变漏感增加驱动电压尖峰,降低可靠性; 驱动波形受原边主管开关波形影响。
Power for the Better6 CONFIDENTIAL力求更好典型电路及其特点他驱方式优点: 易实现符合同步整流需要的驱动时序逻辑; 易获取高效率; 外围电路较简单; 在反激,对称半桥,全桥,LLC拓扑应用广泛。
Power for the Better缺点: 需要驱动IC; 成本较高。
7 CONFIDENTIAL力求更好Contents• 同步整流技术概述 • 典型电路及其特点 • 损耗分析 • 同步整流电路中常见问题 • MOSFET选型设计参考Power for the Better8 CONFIDENTIAL力求更好同步整流管损耗考虑A SR MOSFET does not use active switching – switching speed has no primary relevance and has no influence on efficiency! Losses in a SR MOSFET come from• • • • Conduction losses (like in a diode) Body diode conduction losses(dead time) Gate drive losses (not present with diodes) Reverse recovery losses (like in a diode, but typically larger)Power for the Better9 CONFIDENTIAL力求更好同步整流管损耗考虑ConductionConducting lossesPv _ cond = IBody diode conduction loss2 RMS⋅ RDS ( on )PV _ BD _ cond = VD ⋅ I D ⋅ t BD _ on ⋅ f swGate lossesSwitchingPv _ gate = Qg ⋅ Vg ⋅ f swTurn-off – reverse recovery lossesPsw = VT ⋅ (1 2 ⋅ Qoss + Q *rr ) ⋅ f swPower for the Better 9/17/2015 力10 CONFIDENTIAL求更好AOS Confidential10同步整流管损耗考虑Upeak I comm Utrafo Qoss di/dt=const Irev_ peak tIpeak trev tUpeak Qrr* UDSIDtimeMOS body diode 反向恢复电压,电流简化波形和实测波形Coss8 7 6 Coss [nF] 5 4 3 2 1 0 0 10 20 30 40 50 Uds [V] 60 70 80 90 100 Coss Coss_meanQoss = ∫ coss (t ) ⋅ v(t ) ⋅ dt = VT ⋅ Cconst ⇒ Cconst0UT1 T = ⋅ ∫ coss (t ) ⋅ v(t ) ⋅ dt VT 0UPower for the Better11 CONFIDENTIAL力求更好同步整流管损耗考虑80V MOSFET technology; transformer output 40V; Vout = 12VPower Losses per SR MOSFET Switching Frequency - 125kHz4.0 3.5power dissipation [W]Qrr/Mosfet Qoss/Mosfet Diode/Mosfet Qg/Mosfet Conduction/Mosfet3.0 2.5 2.0 1.5 1.0 0.5 0.01030output current [A]50Power for the Better12 CONFIDENTIAL力求更好同步整流管损耗考虑Synchronous rectification yields a major efficiency gain MOSFETs have lower conduction losses but higher switching losses than diodes Turn-off losses should be minimized by• • • • Lowering the transformer voltage Using MOSFETs with a low voltage-class Using packages with a low contribution to Rds(on) Correctly selecting the Rds(on)Power for the Better13 CONFIDENTIAL力求更好Contents• 同步整流技术概述 • 典型电路及其特点 • 损耗分析 • 同步整流电路中常见问题 • MOSFET选型设计参考Power for the Better14 CONFIDENTIAL力求更好同步整流电路面临的几个问题驱动时序一旦不同步易引起效率降低(驱动开通延迟,MOS 体二极管导通 时间增加)和电流倒灌现象(驱动关断延迟)对于主变压器绕组电压非互补的拓扑中,例如半桥,全桥,存在较长 的死区时间,导致采用自驱电路的MOS驱动电压不足或没有,效率降低;需 要采取栅荷保持技术;驱动绕组电压受变压器漏感影响,驱动波形不可避免有一定尖峰电压, 降低可靠性; 自驱电路所用的绕组电压幅值随占空变化较大,容易超过Vgs 限值而损 坏MOS管,需要增加由一个MOS管组成的正-负限幅电路;Power for the Better15 CONFIDENTIAL力求更好同步整流电路面临的几个问题上述增加的正-负限幅电路会增加驱动损耗,还会增加主功率MOS管的 导通和关断时间,从而降低效率; 辅助绕组如果带中心抽头,则有驱动负压,增加驱动损耗; 整流管和续流管的驱动电压在切换时,存在一定的重合,从而产生直 通现象; 自驱驱动波形和原边主管Vds波形高度耦合,易受其影响; 电源输出并联导致可能的起机时预偏置电压跌落; MOSFET自身的可靠性问题(抗重复雪崩击穿能力和耐dv/dt 耐受力)Power for the Better16 CONFIDENTIAL力求更好Contents• 同步整流技术概述 • 典型电路及其特点 • 损耗分析 • 同步整流电路中常见问题 • MOSFET选型设计参考Power for the Better17 CONFIDENTIAL力求更好同步整流电路MOS选型考虑36~75V 18~75V4u L1VOUT=5V&12V100u C3 TX1 S1 P12 R1100u C21n C1ACF power stageinput36~75voutput5v AON6230 AON6240 AON6590* AON6292 AON6290 AON6280 AON6278partdescription1.44m / 40V 1.6m / 40V 0.95m / 40V 6m /100V 4.6m / 100V 4.1m/80V 3.3m/80V 120V 16.5m /150V 3.6m/60V 2.4m/60Vremark原副边匝比:436~75V12v原副边匝比:1.5~218~75V12vTBD(续流管) AON6250(续流管) AON6242(整流管) AON6260(整流管)原副边匝比:0.75~1Power for the Better18 CONFIDENTIAL力求更好同步整流电路MOS选型考虑FB/HB 200W-800W for Data communicationQ65 C48 Q62 T7 L23 C47 Q64 Q66 Q61input36~7 5V 40~6 0Voutput12v 10vpartAON6292 AON6290 AON6242 AON6260description6m /100V 4.6m / 100V 3.6m/60V 2.4m/60Vremark原副边匝比:5:2(稳压) 6: 2(半稳压) 原副边匝比: 4: 1(稳压)Q6736~75V 40~60V4u L112V 10VinputTX1 100u C1 S1 P1 100u C2output12v 10vpartAON6260 AON6242 AON6752description2.4m /60V 3.6m / 60V 1.7m/30Vremark原副边匝比:5:2(稳压) 原副边匝比: 4: 1(稳压)36~75 V 40~60 VPower for the Better19 CONFIDENTIAL力求更好同步整流MOS选型考虑outpu Full bridge regulator 200W~1000W for 佛如for wireless base stationD136~75V100u C24u L1P1S1TX1100u C130VD2inputpartdescriptionremarkT X4Q72L22IRF530Q9P1S1S2TX11m C2I RF530Q4I RF530Q3I RF530Q2I RF530Q12uL11m C1I RF530Q5I RF530Q6I RF530Q7I RF530Q81m C3Buck regulator(33V)+ full bridge/push-pull(open loop) 200W~1000W for wireless base station4u L236~75V1m C2P1S1TX 1100u C130V100u C3P1S1Half bridge /full bridge LLC for54Vout rectifierCONFIDENTIAL22 Power for the Betterinput output part Description remarkAC inputDC input54v AOT2500LAOB2500L6.5m @150V TO-2206.2m @150V TO-263Q6C4C3L1C8D3C2D2Q1Q3T1C1L3Q5D1C5Half bridge /full bridge LLC for 12Vout server powerEfficiency in half load reach the standards is difficulty pointCONFIDENTIAL23Power for the BetterQ4Q2inputoutputpartDescriptionremarkAC input DC input12vAON6230AON6232AOT240L AON6152AOT260L AOB 260L1.44m @40V DFN5*61.6m @ 40V DFN5*62.9m @ 40V TO-220@ 45V DFN5*62.5m @ 60V TO-2202.3m @ 60V TO-26345v for more strictly derating60v for TO-220 package谢谢!CONFIDENTIAL24 Power for the BetterThanks!。