A Method for Balancing Capacitor Voltages in Single-Phase Half-Bridge PFC Converter

Abstract

A single-phase half-bridge Power Factor Correction converter has no common-mode noise theoretically. The output dc capacitor voltages, however, happen to be unbalanced sometimes. In this paper, it is made clear that the unbalanced voltages are principally caused by the asymmetry on the reference signal or the detected current wave. We investigate an improved converter, which has double half-bridge PFC converters in common with two output dc capacitors and should be connected to the single-phase three-wired distribution system. It can output their balanced capacitor voltages even if the reference signal wave has the asymmetry due to the offset in the control circuit. As a result, it can be operated with the lower distortion in source currents, the higher power factor, and the lower ripple in output dc voltage as compared with the conventional converter. Moreover, their output capacitors can be downsized for saving the costs and the maintenances.