Design of LLC Converter Parameters Based on ZVS Characteristic Analysis

LLC resonant converter is attractive for its high power density, high efficiency. When converter is operating below the resonant frequency, traditional FHA method is not accurate to obtain an adequate inductor to let system operate in zero-voltage-switching (ZVS) mode. This paper proposes a novel method to analyze the value of magnetic current from the perspective of energy conversion. During load switching, if the operating point moves to the capacitive region, the switch will lose ZVS. This paper propose a method to determine if the converter is likely to lose ZVS during load switching based on circuit parameters. Finally, a 300W 500kHz 400V/24V half-bridge LLC resonant converter is built to verify the validity of method.