With the rapid development of the information industry

the demand for converters featuring a wide input voltage range and high efficiency has increased. To further extend the input voltage range of the conventional LLC resonant converter

an LLC resonant converter with a novel wide input voltage range was proposed. The proposed converter was capable of operating in half-bridge(HB)LLC mode

full-bridge(FB)LLC mode

and a combined FB+HB LLC mode

in which the gains of the half-bridge and full-bridge LLC converters were superimposed. As a result

the switching-frequency range was compressed to a region close to the resonant frequency

and efficiency performance was improved. Pulse-frequency modulation(PFM)was employed to enable wide-input-voltage operation

achieve relatively smooth mode switching during power-off retention

and simplify the transformer design. Finally

a prototype with an input voltage range of 60-260 V and an output of 12 V/12.5 A(150 W)was developed. The experimental results show that the proposed converter achieves zero-voltage switching(ZVS)and zero-current switching(ZCS)under various operating modes

maintains good efficiency

and provides a gain range consistent with the theoretical analysis.