Analysis and compensation of input current dead-zone in three-phase single-stage full-bridge PFC converter

A three-phase single-stage PFC (Power Factor Correction) converter based on full-bridge struc-tureis researched, which operates in DCM (Discontinuous Conduction Mode), and can realize functions such as PFC, electrical isolation between input and output sides and output voltage regulation. Analysis of the equivalent circuits in both ideal and nonideal conditions shows that, due to the on-state voltage drop of each switch and diode in the main circuit, there will be input current dead zone when its voltage is lower than the voltage drop of main circuit, which will be more serious as the input voltage decreases. According to the working principle of the circuit, a compensation circuit is proposed to suppress the dead zone, which is composed of six low power switches and resistors. With corresponding control strategy, when the smallest input voltage is lower than the voltage drop, the current of that phase flows through the compensation circuit, and the dead zone of input current is thus eliminated. Simulation and experimental results show the validity of theoretical analysis.