Analysis of a new resonant converter with auxiliary windings to extend input voltage range

The resonant converters have been developed for medium-power applications due to the high circuit efficiency and high power density. However, the switching frequency is related to the voltage gain of resonant converter. Therefore, the resonant converter is usually limited at narrow input voltage applications. To overcome this limitation, the auxiliary winding and switch are adopted at the secondary side to provide a high voltage gain under low input voltage case or to extend the hold-up time when AC power is turned off. Thus, the switching frequency variation can be reduced for the wide input voltage case. The operation principle, circuit characteristics and design procedure of the proposed converter are presented in detail. Experiments are provided to verify the effectiveness and demonstrate the circuit performance.