Hybrid Control Scheme for a Half-Bridge LLC Resonant Converter with a Wide Input Range

In this paper, the LLC resonant converter with hybrid PFM and PWM control scheme is proposed for the wide input range operation. In low input voltage range, the PFM control scheme is applied to LLC resonant converter for normal operation. In PFM mode, zero-voltage switching is achieved form no load to full load condition. In high voltage range, the PWM control scheme is applied to the converter to reduce the gain of resonant tank. In PWM mode, zero-voltage switching is not achieved because the current is not enough to discharge parasitic capacitor of power MOSFET for turning on the body diode. The proposed method is experimentally verified with 400W laboratory prototype.