Accurate Design of High-Efficiency LLC Resonant Converter With Wide Output Voltage

$LLC$
resonant converter is utilized for a 3.3-kW on-board charger (OBC), where high efficiency and wide output voltage are required. In this paper, the resonant frequency and the magnetizing inductor of the converter are first optimized based on the required efficiency. Then, the resonant inductor and the resonant capacitor are designed considering the required maximum output voltage. The energy equations and the KCL and KVL equations about the converter are established by the time domain method to find out the information about peak resonant current, peak magnetizing current, and minimum switching frequency. The above-mentioned information is used to accurately design the converter’s magnetic components. A 3.3-kW prototype applied for OBC is developed. Its output voltage ranges from 230 to 430 V. Its peak efficiency is higher than 97.6%. The experimental results verify that the proposed method can accurately design the efficiency, the voltage gain, and the magnetic components of
$LLC$
resonant converter in a wide output voltage range.