A Verification of Applying Superjunction MOSFETs in Dual-Active-Bridge Converters Operated with Minimal RMS Current

This paper presents a comprehensive analysis of zero-voltage-switching (ZVS) in the operation of a proposed peak current optimization scheme in dual-active-bridge converters with the voltage ratio between the primary and secondary sides is not matched with the turn ratio of its transformer. A minimal switching current and dead-time range are introduced to discuss the required conditions for ZVS realization in all possible operations with considering the parasitic capacitance of the power semiconductor device and dead-time. For a specific power range that can not achieve ZVS, a model-based lowest switching current control is proposed to achieve ZVS with ample switching current. Moreover, the allowable range of the dead-time for ZVS as function of the lowest switching current is also analyzed to determine the appropriate dead-time. Experiments using a 1-kW small-scale prototype were conducted to verify the theoretical analyses. We propose the use of silicon superjunction (SJ) MOSFETs for DAB converters by ensuring ZVS. To verify the concept, demonstrations using a fabricated DAB converter prototype with SJ-MOSFETs were conducted. It was verified that the proposed strategy can realize ZVS in a wide operating range, and achieve safe operation with SJ-MOSFETs.