Synchronous Rectification Controller for Boosting up the Efficiency of a Flyback Converter

In low output voltage power converters, the efficiency is mainly affected due to the voltage drop of a diode. One of the best solution is to replace this diode with a synchronous rectifier. Synchronous rectification (SR) is the technique for boosting up the efficiency of rectification by replacing the diode with actively controlled power MOSFET switch. In this paper, an effective approach for controlling the SR MOSFET of the flyback converter using SR controller is presented. The negative voltage across the output due to overlapping of the primary and secondary switches can be removed by using SR controller. Also SR controller assures reliable turn-on and turn-off of the SR MOSFET and reduces the cross conduction loss between the primary side MOSFET and secondary synchronous rectification MOSFET, thus higher efficiency can be achieved. The response of the SR controller is evaluated by simulating a 50-W flyback converter using MATLAB/ SIMULINK.