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Integration of high-voltage (HV) on-board battery charger (OBC) and low-voltage (LV) auxiliary power module (APM) can provide significant improvement in the overall weight, size, and efficiency of electric vehicle powertrains. This paper proposes an optimized isolated triple-active bridge (TAB) converter to integrate the functions of OBC and APM in a single converter. The proposed converter has a simple structure and is capable of charging both HV (400V) and LV (12V) batteries simultaneously. Furthermore, a conduction loss-minimization strategy is proposed by utilizing the converter's five degrees of freedom (DOF), aiming to improve the efficiency of the converter by reducing the RMS current in the LV bridge. Wide variations of HV and LV battery voltages are considered. Although soft-switching operation is lost under certain conditions with the conduction-loss minimization scheme, the total power loss of the converter can be reduced by 50%. Simulation results of a converter capable of delivering 3.3kW and 1.6kW simultaneously to the HV and LV battery, respectively, proved the theoretical analysis. 3D Finite Element simulations demonstrated the increased power density of the proposed integrated converter.
Kougioulis et al. (Sun,) studied this question.