A Novel SiC-Based Multifunctional Onboard Battery Charger for Plug-In Electric Vehicles

This article proposes a simple and effective method to reduce the bulky capacitor in onboard battery charger (OBC) where low-voltage (LV) battery charging circuit is utilized as an active power decoupling (APD) circuit to filter out the second-order ripple power. When the OBC is connected to the grid to charge the high-voltage (HV) battery, the switches on the primary side of the LV charging circuit are operated as those of an ac-dc converter with APD function. Consequently, small dc-link capacitors can be used instead of large capacitor banks. In the proposed OBC, the switching devices are shared for the ac-dc converter, APD circuit, and primary-side of the LV charger. For a simultaneous charging of the LV and HV batteries, a dc-dc converter is added, which shares the same transformer core and secondary side with the LV charging circuit. So the functions of the OBC are maintained in the proposed topology whereas the volume and cost are decreased by 52.3% and 46.9% compared with the conventional nonisolated OBC, respectively. A 2-kW SiC-based prototype has been designed and tested to verify the validity of the proposed system. The peak efficiencies of the OBC and LV charger are 96.1% and 95.3%, respectively.