Improved Burst Mode Operation for DAB Converters to Achieve ZVS in Full-Load-Range by Considering Device Voltage Oscillation

This paper proposes an improved burst mode for dual active bridge (DAB) converters to obtain zero-voltage switching (ZVS) operation over the entire load range. Despite the burst mode can reduce the number of switching and improve the efficiency by introducing non-switching intervals, the conventional burst mode operations fail in the realization of ZVS over the entire load range. The proposed method introduces an oscillation of device voltages which can be resonant to zero during the non-switching interval of the burst mode. The oscillation period is discretely adjusted so that the switching devices can always be turned on at zero voltage even at light-load conditions. As a result, further efficiency improvement can be obtained in the entire load condition with an extended ZVS range. The effectiveness of the proposed method was verified by experiments with a fabricated DAB converter, which consisted of SiC-MOSFETs and was operated at 100-kHz.