An unbalanced PWM control strategy for the full-bridge series resonant converter

An unbalanced pulse-width modulation (UPWM) control strategy is proposed to extend zero-voltage switching (ZVS) range and improve the overall efficiency for a full-bridge series resonant converter. Steady-state analysis is performed using fundamental harmonics approximation and the ZVS conditions are given. Compared with other fixed-frequency control strategies, all switches of the converter are able to maintain ZVS operation with UPWM control at large variation of converter gain. Experimental results have demonstrated that the proposed UPWM control can improve the converter efficiency with the variations of input/output voltage, especially under light load condition.