Patent ID: 6912143

Claim:
A synchronous rectifier, comprising: a transformer having a primary winding electrically connected to a power source, a secondary winding, a first auxiliary winding, and a second auxiliary winding; a first switch and a second switch electrically connected to said secondary winding and control terminals of said first switch and said second switch individually connected to said first and second auxiliary windings for being either self-driven directly from voltages of said auxiliary windings; a third switch electrically connected between said first switch and said first auxiliary winding in series; a fourth switch electrically connected between said second switch and said second auxiliary winding in series; a detecting circuit electrically connected to an output terminal of said synchronous rectifier for detecting a load status; and a control circuit electrically connected to said detecting circuit for enabling said third switch and said fourth switch when said load status is at a heavy load and disabling said third switch and said fourth switch when said load status is at a light load.