Extension of zero-voltage-switching range in dual active bridge converter by switched auxiliary inductance

This paper proposes a novel Dual Active Bridge (DAB) converter, which has an auxiliary inductor and a bi-directional switch connected in parallel to a transformer in order to achieve zero voltage switching (ZVS) over a wide load range and a wide battery voltage variation. In the proposed converter, the equivalent magnetizing inductance is changed by switching the auxiliary inductance depending on the output power. In order to achieve ZVS at light load, the equivalent magnetizing current is increased by connecting the auxiliary inductance in parallel. At heavy load, the equivalent magnetizing current is reduced without connecting the auxiliary inductance because ZVS is achieved without any increment of the equivalent magnetizing current. In addition, the auxiliary inductance is switched without the occurrence of DC-offset of the auxiliary-inductor current. In the experimental results, the ZVS range is extended by 50% at most. In addition, the high efficiency in the wide load is achieved by the switched auxiliary inductance.