Study and Design of DC-DC LLC Full Bridge Converter for Electric Vehicle Charging Application

This article mainly focuses on the study, design and operating frequency range aspects of high frequency based resonant LLC full bridge DC-DC converter for onboard battery charging application of EVs (electric vehicles). This suggested DC-DC LLC converter has low switching loss due to soft switching and hence high-efficiency because ZVS (Zero Voltage Switching) is used to turnon the MOSFET Switches, and ZCS (Zero Current Switching) is used to turnoff the rectifier diode. In this converter, a single high-frequency transformer is used to step down the voltage level suitable for battery charging, whose primary is connected to the resonant tank circuit and secondary is connected to the bridge rectifier. Fast charging method utilizes the CC (constant current)-CV (constant voltage) charging modes. Battery charging operation first uses the CC mode of charging, and ends with the CV mode of charging. This paper describes the principle of operation, design analysis of the converter, battery charging, and simulation results analysis of the suggested 1kW LLC resonant full bridge converter. The proposed model offers the advantages like, better voltage regulation at light load conditions, simple close-loop control, and soft switching benefit to minimize the losses and thereby maximize efficiency. The model was tested using the MATLAB/Simulink platform.