Analysis of GaN Based Full-bridge CLLC Resonant Converter Considering Output Capacitances under Light-load Conditions

Under light-load conditions, the voltage gain of CLLC resonant converter usually exhibits an abnormal increase with rising switching frequency. To investigate the practical voltage gain characteristic, this paper proposes a comprehensive analysis for GaN based full-bridge CLLC converter at light-load conditions. A detailed time-domain circuit model is established considering output capacitances and dead-time operation. Based on the model, the output voltage is derived, and its main influencing factors are discussed to explain the light-load gain characteristic. Finally, a 21.5V/400V, 200W GaN based CLLC resonant converter prototype is built to verify the correctness of the analysis.