电流断续模式Boost功率因数校正变换器的变占空比控制

摘要

DCM Boost PFC变换器具有开关管零电流开通、二极管无反向恢复和开关频率恒定等优点,但是当在半个输入周期内占空比恒定时,其输入功率因数较低。本文推导了DCM Boost PFC变换器的输入电流和PF值的表达式,并提出一种变占空比控制的方法,可以在全输入电压范围内将PF值提高到接近于1。为了简化电路实现,本文进一步给出一种拟合占空比的方法。与定占空比控制相比,所提出的变占空比控制方法还具有输出电压纹波小和效率高等优点。实验结果验证了理论分析的正确性。%DCM Boost PFC converter features zero-current turn-on for the switch,no reverse recovery in diode and constant frequency operation,however,the input power factor（PF）is relatively low when the duty cycle is constant within one half the line cycle.This paper derives the expressions of the input current and PF of DCM Boost PFC converter,and based on which,a variable duty cycle control is proposed so as to improve the PF to nearly 1 in the whole input voltage range.A method of fitting the duty cycle is further proposed for simplifying the circuit implementation.Besides a higher PF,the proposed variable duty cycle control achieves a lower output voltage ripple and a higher efficiency over the constant duty cycle control.The experimental results from a 120W universal input prototype are given to verify the effectiveness of the proposed method.