Although a synchronous rectifier can help to improve a Flyback converter’s efficiency at full load,it normally will sacrifice some efficiency at light load or no load. The reason is: whenconventional self-driven synchronous rectification is implemented in a Flyback converter, there isusually no DCM operation any more. When the secondary SR current drops to zero, becausethe SR is still on, the secondary current will go negative continuously until the SR is turned off bythe primary side switch turning on. At light load or no load, there is a significant amount ofenergy circulating between the primary side and secondary side. This circulating energyincreases the conduction losses and decreases the efficiency at light load or no load conditions.