Voltage-driven synchronous rectification in forward topology

The self-driven synchronous rectification (SDSR) forward topology is widely used in offline low voltage DC-DC power conversion. The major disadvantage of the SDSR forward topology is the conduction of the SR body diode when transformer reset process is over. SR body diode conduction brings excessive loss due to its high forward drop and poor reverse recovery characteristic. In this paper, a new SR drive mechanism is proposed. This drive method effectively prevents the body diode of SR from conduction with a coupled winding and several low power switches. Theoretical analysis and experimental results are shown. A 250 kHz, 48 V input, 5 V/10 A output low profile DC-DC module is designed to verify the proposed idea. 92.3% efficiency is achieved at full load typical line.