A Fully ZVS Critical Conduction Mode Boost PFC

Abstract

Boost converter operating in critical conduction mode is widely used in low-power power factor corrector because of its simplicity and low switching losses. The switching loss due to parasitic capacitor discharge at the on-time instant can also be reduced by a valley switching technique. In this paper, we introduce a new driver topology for the high-side switch in a synchronous boost converter operating in the critical conduction mode to obtain full zero-voltage switching. Using the proposed high-side driver topology, the conventional control circuit is sufficient to control the low-side switch, and no additional control circuit is required to adjust the timing of the switches. Finally, the line current distortion is reduced through the use of on-time extension technique to less than 10% in the defined load range. Based on approximate mathematical calculations, two separate distortion reduction circuits are designed to implement the on-time extension technique for both voltage-mode and current-mode control methods.