A Unified Control for PFC Converter With Seamless Transition Between PWM/PFM Modes

Discontinuous conduction mode is often used in boost power factor correction converter. This article proposes a unified control method to achieve both pulsewidth modulation control and pulse frequency modulation control, which is based on the virtual impedance principle. The control modes can easily be changed by only adjusting one control parameter. Consequently, by comprehensively considering current ripple, switching frequency, and efficiency, the converter can operate flexibly in the situation of variable loads. This article first introduces the operation principle of the proposed unified control method. Then, the operation condition for each control mode is discussed. Besides, the current ripple, the switching frequency, and the power loss are analyzed. Finally, the experimental results of steady-state test and load switching test are presented. And the efficiency of the converter is more than 95% in the range from half load to full load. These experimental results fully verify the effectiveness of the proposed control.