This paper proposes the novel generation method of gate signals to control output voltage in a wide range and to achieve synchronous rectification operating in half-bridge LLC resonant converters. The switching frequency modulation is used in half-bridge LLC resonant converters for control strategy of output voltage. The switching timing of secondary MOSFETs is compensated using the gate signal of primary side by the reference value of switching frequency without any detection circuits. The Current Doubler Synchronous Rectifier (CDSR) and the Center Tapped Synchronous Rectifier (CTSR) are implemented for secondary circuit in the experiment. According to experimental results, not only stable operation in a wide switching frequency range but also the improved conversion efficiency is achieved by the proposed method.