实用开关电源分析与设计.ppt

传统服务器一次电源设计 * 45w 235w 285w Soft start 移相全桥变换器(PSFB) 小功率辅助电源和电源适配器设计 台式机电源及无外壳内置式电源设计 台式机电源 Desktop PSU High Efficiency Barrier MOS Hard Switch Secondary rectifier loss Multiple Output Way to Efficiency Up Low Coss MOSfet Synchronous Rectifier Merits: Low Voltage Stress on MOSFET No need reset circuit High Reliability Two Transistor Forward (TTF) High Efficiency Barrier MOS Hard Switch Secondary rectifier loss Multiple Output Way to Efficiency Up Low Coss MOSfet Synchronous Rectifier Merits: Bi-Magnetization of Transformer Much higher Duty Cycle than TTF High Efficiency than TTF Active Clamped Forward (ACF) High Efficiency Barrier Multiple Power Stage in Series Way to Efficiency Up Enhance BUCK Efficiency Merits: High Efficiency at every Power Stage Variable Frequency HB LLC + BUCKs 无外壳内置式电源设计(Open frame Imac PSU) Vdsmax Double magnetizing duty loss loss Synchronous rectifier driving comparison of waveform-ACF ACF Input voltage load Switching transistor P-P voltage(V) duty Clamping transistor P-P voltage(V) 230V 5% 710 38.12% 725 50% 745 41.66% 730 100% 795 45.55% 765 5% load 50% load 100% load comparison of waveform-TTF TTF Input voltage load duty 230V 5% 30.01% 50% 31.74% 100% 33.36% 10% load 50% load 100% load 优点： 变压器直接传递功率，功率等级比反激高； 正激变压器体积小； 单端电路，所用器件较少，可靠性高； 输出电流脉动小，电压纹波小； 缺点： 变压器单向磁化，变压器利用率低（双管正激或普通正激）； 开关电压应力高（普通正激或ACF）； 占空比有限制（保证去磁时间），不适合宽输入范围； 需要有去磁回路或额外的去磁电路; Forward Forward 适合于中小功率开关电源，一般功率在200W~1kW LLC半桥谐振变换器(LLC HB) LLC半桥谐振(LLC HB)电路拓扑 LLC半桥谐振(LLC HB)基本关系式 ZCS ZVS Vinmax Vinmin Full load No load At resonant frequency High line operation Higher than resonant frequency Large switching loss poor line regulation — not desirable Lower than resonant frequency Low line operation Holdup time operation LLC半桥谐振(LLC HB)工作原理 Half bridge switching Alternating high side ON and low side ON HB voltage: 50% duty cycle (T=T) blockwave steep HB slopes “happen automatically” GateLowSide GateHighSide HB VBoost 0 Voltage waveshapes in time GateHighS