Half-Bridge LLC Resonant Converter Design for High Voltage Battery to Low Voltage Battery Conversion in Electric Vehicles

The LLC resonant converter has high-efficiency and low switching losses by achieving Zero Voltage Switching (ZVS). Therefore, it has been widely used in the industry. In conventional vehicles, the low voltage systems are fed by the 12V battery. However, several appliances such as the heater, air-conditioning compressor operate at a few kilowatt regions. Thus, the amount of the current drawn by these appliances is relatively higher with the conventional 12V system. To compensate this high current, a 48V level is obtained from the high-voltage batteries via a dc-to-dc converter. In this study, 3kW Half-Bridge LLC resonant converter is designed for high voltage battery to low voltage battery used in electric vehicles by using PSIM. 48V output voltage is regulated with 0.17% by the proposed converter in several cases, which are varied input voltage and loads by changing switching frequency owing to control algorithm. In terms of unit step response, rising and settling times are 5.55 ms and 1.06 ms, respectively.