Light-Load Efficiency Enhancement of High-Frequency Dual-Active-Bridge Converter Under SPS Control

Dual-active-bridge (DAB) converter is an attractive topology to be used as a DC transformer (DCT) in the DC power distribution system. Because the voltage gain for DC transformer is relatively fixed, single-phase-shift (SPS) control is popularly adopted for DAB converter to achieve simple power control. Aiming at increasing the light load efficiency of high-frequency DAB converter under SPS control, this chapter proposes a concept to achieve full load range zero-voltage-switching (ZVS) with minimum RMS current in certain voltage variation range. In the proposed method, the added magnetizing inductance creates the possibility to achieve ZVS for all power switches. And, the voltage gain of the converter is specially controlled by turns ratio, which is no longer the conventional unity voltage gain condition. The key parameters optimization, including the turns ratio, magnetizing inductance and leakage inductance of the transformer, are introduced based on ZVS and current stress analysis. A 250 kHz, 400/48 V, 1000 W GaN-based DAB prototype is built, which shows performance improvements at light load.