Soft-switching converter with low circulating current and wide range of ZVS turn-on

In this paper, a new hybrid dc–dc converter with low circulating current within the freewheeling interval, wide range of zero-voltage switching and reduced output current ripple is presented. The proposed hybrid circuit includes two three-level pulse-width modulation converters and a series resonant converter with the shard lagging-leg switches. Series resonant converter is operated at fixed switching frequency (close to series resonant frequency) to extend the zero-voltage switching range of lagging-leg switches. The output of series resonant converter is connected to the secondary sides of three-level converters to produce a positive rectified voltage instead of zero voltage. Hence, the output inductances can be reduced. The reflected positive voltage is used to decrease the circulating current to zero during the freewheeling interval. Therefore, the circulating current losses in three-level converters are improved. Finally, experiments are presented for a 1.44 kW prototype circuit converting 800 V input to an output voltage 24 V/60A. Copyright © 2015 John Wiley & Sons, Ltd.