Soft-switched bidirectional buck-boost converters

A bidirectional buck-boost converter with a new soft-switching active-snubber cell that reduces switching losses is introduced. Soft-switching cell consists of an active snubber switch, a snubber inductor, and a two-winding transformer with associated magnetizing current reset circuit. The soft-switching cells enable the buck and boost rectifier to turn off with a controlled turn-off rate of their current to minimize corresponding reverse-recovery losses. In addition, in the introduced soft-switching cell, the power-controlling buck and boost switches turn on with zero-voltage switching (ZVS) and the snubber switches turn off with zero-current switching (ZCS). The performance of the proposed bidirectional converter was evaluated on a 5-kW prototype exchanging energy between a 400-V bus and a battery with voltage range between 200 V and 300 V. The 100-kHz prototype circuit exhibits the maximum full-load efficiency of 99.1% in the boost-mode and 98.2% in the buck-mode operation.