A Quasi-Two-Stage Isolated Bidirectional Buck-DAB Converter for Wide Input Voltage Range

In this article, a quasi-two-stage buck-DAB (QBDAB) converter is proposed for improving the performance of the conventional dual active bridge (DAB) solution under a wide voltage range. For the proposed QBDAB converter, the DAB can always work under voltage matching conditions for wide voltage range applications, and the gain is adjusted through the added front-end circuit. The front-end circuit is similar to a buck converter, while only part of the transmission power flows through the circuit, which could also reduce the burden of achieving ZVS of the front-end circuit. Therefore, compared with the traditional two-stage buck-DAB converter solution, the related loss for the buck circuit can be reduced. The working principle, power transfer characteristics, and full load range ZVS design are analyzed deeply in this article. A detailed comparison of the QBDAB and other related combined buck+DAB topologies is also presented. Finally, the effectiveness of the proposed QBDAB is verified through experimental results from a 1kW prototype.