ActiveClampandResetTechnique有源钳位电路完整开关周期工作过程分析PPT课件.ppt

Active Clamp and Reset Technique 有源钳位电路 完整开关周期工作过程分析 摘自TI资料 庄主 2006.02.18—2.20传统的复位电路及RCD复位电路有源钳位电路及include the MOSFET parasitic output capacitance (Coss) and the internal body diode的电路三种复位方式的性能比较有源钳位的优点及与其它电路的相比较的不同点:SIGNIFICANT BENEFITS:&& "recycles" transformer magnetizing energy instead of dissipating it in a resistor&& facilitates Zero Voltage Transition of the main switch for higher efficiency&& uses lower voltage MOSFET and diodescompared to the RCD && reduced EMI/RFI via soft switching && eliminates lossy snubber network on primary&& operates at fixed frequency&& allows much higher frequency operation && similar power transfer to conventional square wave switching&& duty cycles beyond 50% max are obtainable && actively resets main transformer to third quadrant of BH curveDIFFERENCES AND SIMILARITIES:This new approach requires a few more parts than the other forward choices to achieve the benefits listed previously. Differences include:&& an additional high voltage MOSFETclamp/reset switch && an isolated, variable duty cycle gate drive for the clamp/reset switch&& a modified PWM control technique to properly program the associated delays between gate drives to achieve the zero voltage transitions&& a new gate drive technique to extract theproper clamp/reset drive pulseINITIAL CONDITIONS: time t0:>0: t t3<3Cr*(Vin+Vcr) 2/2.Cr是整个的谐振电容.。