A Dual Active Bridge DC-DC Based Single Stage AC-DC Converter with Seamless Mode Transition and High Power Factor

In this paper, a dual active bridge (DAB) based single-stage isolated AC-DC converter is studied. By analyzing the root mean square (RMS) value of the leakage inductor current, the high frequency transformer turns ratio is optimized for higher conversion efficiency. Three operating modes of the DAB converter are utilized in the control strategy and the current and voltage waveforms of these operating modes are analyzed. The control variables, including the phase shift ratio φ, the primary side duty cycle d1 and the secondary side duty cycle d2 are combined based on instantaneous calculation according to achieve boundary zero voltage switching (ZVS). The mode transition is seamless and the switching frequency is fixed. Furthermore, the magnetizing inductor of the transformer is designed to help the secondary side switches to achieve ZVS. ZVS conditions and parameter designment are given in the paper. Besides, a 1kW prototype was fabricated to verify the effectiveness of the designment and control strategy.