Interleaved PFC balance charger with passive lossless snubber for series-connected batteries

Abstract

An interleaved balance charger for four series-connected batteries is proposed in this study. Each battery can be charged individually in the proposed charger for balance charging process. The charger is operated in the discontinuous conduction mode (DCM) for power factor correction (PFC). Two flyback and two buckboost converters are input parallel-connected and controlled with multi-phase interleaving technique. The input current ripple is then greatly reduced. Each flyback converter is used to convert the charging power from the grid to one corresponding battery. The two buckboost converters are output parallel-connected and followed by a dual output converter. Two batteries in the series-connected battery tank are charged by the dual output converter. Moreover, a passive lossless snubber is proposed to recover the leakage inductance energy in the flyback converters. A 500 W prototype is constructed and corresponding experiments are carried out. From the experimental results, it can be seen that the efficiency is improved by about 3% compared with the topology with common RCD snubbers. The measured power factor of the proposed charger is higher than 0.976.