A High-Efficiency and Stable-Operating Single-Stage Half-Bridge AC/DC Resonant Converter

Single-stage AC/DC converters have the potential to optimize efficiency, cost, and power density. How ever, existing three-phase solutions generally require numerous high-frequency switches and complex modulation schemes. This paper proposes a three-phase single-stage half-bridge AC/DC resonant converter that integrates a low frequency Swiss rectifier with a three-level half-bridge LLC resonant circuit. The proposed converter employs only four high-frequency switches while achieving power-factor correction (PFC), wide-range output voltage regulation, and zero-voltage switching (ZVS). To accurately characterize the resonant tank under time-varying three-level excitation, a time-domain numerical method is developed for steady state analysis and resonant parameter optimization. By ex ploiting the zero-input natural response during the negative half-cycle, the numerical analysis is confined to the positive half-cycle, thereby reducing the computational burden. Furthermore, based on the monotonic relationships of the resonant current integral with the switching frequency and duty ratio, an integral hysteresis control strategy is pro posed to achieve cycle-by-cycle input current shaping and output voltage regulation. Experimental results obtained from a 6.6 kW prototype demonstrate an input current total harmonic distortion (THD) of 2.33%, a peak efficiency of 97.6%, and a full-load efficiency of 96.7%. Stable operation is also verified over a wide output voltage range and under grid disturbances.