A CCM/DCM Dual-Mode Synchronous Rectification Controller for a High-Efficiency Flyback Converter

A dual-mode synchronous rectification (SR) controller supporting both the continuous-conduction mode and discontinuous-conduction mode is developed to improve the power efficiency of a flyback converter. The dual-mode SR controller ensures nonoverlapped turning-on of the primary and secondary switches by monitoring the voltage level of the secondary switch. The dual-mode SR controller requiring four pins and only one external resistor has been implemented in a 0.35-μm BCDMOS process and applied to a 50-W flyback converter. The efficiency of the flyback converter is improved by upto 6.8% when the dual-mode SR controller is employed compared to the one employing the conventional SR controller.