Design of Flyback Converter with Voltage Driven Synchronous Rectifier

In low output voltage dc-dc converters, power losses is significant, due to the conduction of rectifying device. Using synchronous rectifiers instead of the conventional fast recovery diodes is an effective solution to this problem in most topologies. However, for synchronous rectifier to perform effectively, it requires an external gate drive with proper sensing and timing control circuits. This can increase the complexity and cost in converter hardware implementation. Design of Flyback Converter with Voltage Driven Synchronous Rectifiers is proposed. The proposed SR is the voltage driven synchronous rectifier (VDSR), which operates depending on the voltage drop across the drain and source of the MOSFET. Experimental results for the 85W (12V/7.1A) proposed converter are shown.