Single-Stage Integrated Buck-Flyback PFC Converter With Low Total Harmonic Distortion Control

Conventional buck power factor correction (PFC) converter has the disadvantage of high harmonic currents due to the dead zone of input current. An improved method, critical-continuous mode control buck-flyback converter has not completely eliminated the impact of dead zone of buck unit on the input current. In this article, a single-stage integrated buck-flyback PFC converter with low total harmonic distortion (THD) control is proposed and analyzed. With the average current mode control, the input current of each unit can be automatically distributed; therefore, the PFC function with extremely low THD can be achieved. Furthermore, the power ratio of flyback converter unit can be designed to be smaller, thereby improving the system efficiency. The design considerations are analyzed in detail, and the key parameters are designed based on the principle of loss minimization. Finally, a 96-W prototype with a peak efficiency of 95.2% and low THD current is built to validate the proposed converter.