Starting and Voltage Suppression Scheme Based on a Passive Forward Auxiliary Circuit for Three-Phase Isolated Full-Bridge Boost PFC Converter

A starting and voltage spike suppression scheme based on a passive forward auxiliary circuit is proposed for the three-phase isolated full-bridge boost power factor correction (PFC) converter. Compared to the existing passive flyback auxiliary circuit, the structure in the secondary side of the integrated transformer is slightly more complicated in the passive forward auxiliary circuit. However, for the PFC converter with the forward auxiliary circuit, current stresses of the diodes in the auxiliary circuit and the switches can be lower than those of the PFC converter with the flyback auxiliary circuit, and power losses of the PFC converter will also be lower. Operational processes of the forward auxiliary circuit are analyzed in both steady and starting states of the PFC converter, based on which comparison of the two auxiliary circuits and design guidelines of the forward auxiliary circuit are discussed. Finally, experimental study has been done on a laboratory-made PFC prototype, and the feasibility of the proposed scheme and the validity of the theoretical analysis are verified by the experimental results.