Voltage control of capacitor in single-stage PFC circuit based on critical mode switching method

A novel critical mode switching (CMS) method is proposed to reduce the high voltage stress of the storage capacitor of single-stage power factor corrector. The principle of CMS is taking use of the switching of the working modes of the converter automatically according to the load condition, which could control the voltage of the storage capacitor based on the analysis of the critical points of the PFC converter and the DC-DC converter. Then the analytic formulation of the working principle is obtained. The expression of the power factor (PF) is also derived based on the analysis of the distortion of the input current. The circuit uses a simple IC to realize the high PF and decrease the voltage stress of the capacitor. Finally, the circuit performance was verified experimentally.