Bi-directional Operation Mode of LLC/CLLC DC/DC Converter for On Board Charger of 800V Battery Systems

Abstract

Global Vehicle OEM’s are raising the battery voltage to increase the mileage of electric vehicles and reduce the battery charging time. A bidirectional on-board charger (OBC) is also required for Vehicle to Grid (V2G) and Vehicle to Load (V2L) operation. Recently, ICCU (Integrated Charging Control Unit), a product that integrates OBC and LDC (Low-Voltage DC/DC Converter) circuit and housing, has been developed. In this paper, we propose LLC/CLLC bidirectional DC/DC converter for OBC circuit in 800V battery system. In forward mode, it operates as LLC full-bridge resonant converter to achieve a wide output voltage range. In reverse mode, the DC link voltage can be designed to be lower than in forward mode by operating as a CLLC half-bridge resonant converter. The proposed converter uses SiC-MOSFET, so it satisfies high voltage and is implemented in a small package. The 11 kW prototype of the proposed bidirectional resonant converter was built and tested to verify the proposed operation.