Analyses and Design of a High Power Bidirectional 48V-12V DCDC Converter System for Electric Vehicle Application

This paper proposes the theoretical analyses, design method, design process and design results of a high power bidirectional 48V-12V DCDC converter system in electric vehicle (EV) application. The design is divided into 3 levels that are topology level, control method level, and block level based on IC with 3 steps respectively. In topology level, full-bridge CLLC is chosen for its high efficiency and good stability. 8 stages are designed for full-bridge CLLC in one switching period. Topology design mainly focuses on determining resonant components by inherent frequency and quality factor. In control method level, FPD (Frequency, Phase shift, and Duty) influence the performance of the whole system in their own way and FPD control method is chosen for this system. In block level, a main control loop that consists of 3 interlaced loops is illustrated by functional blocks and achieved actually by IC design. The whole design is verified by analog IC simulation whose results confirm the basic function and expected performance of the system. The output voltage accuracy enters 0.1% range and efficiency is up to 99.15% in buck mode with full load. The performances of the converter system in other conditions are also competitive.