Self-driven synchronous rectification scheme

A self-driven synchronous rectifier circuit for a power converter, said circuit comprising:

• a transformer having a primary and secondary winding, said secondary winding having a first terminal and a second terminal;
• a first synchronous rectifier having a source, drain and gate, said drain of said first synchronous rectifier connected to said second terminal of said secondary winding;
• a second synchronous rectifier having a source, drain and gate, said source of said second synchronous rectifier coupled to said source of said first synchronous rectifier, said drain of said second synchronous rectifier coupled to said first terminal of said secondary winding;
• a first switch having a source, drain and gate, said drain of said first switch coupled to said gate of said first synchronous rectifier, said source of said first switch coupled to said first terminal of said secondary winding, said gate of said first switch coupled to said second terminal of said secondary winding;
• and
• a second switch having a source, drain and gate, said source of said second switch coupled to said second terminal of said secondary winding, said gate of said second switch coupled to said first terminal of said secondary winding, and said drain of said second switch coupled to said gate of said second synchronous rectifier;
• wherein switching transitions of said first and second synchronous rectifiers are initiated by a polarity reversal of the voltage of said secondary transformer winding.

A method of rectifying a varying voltage from a power converter using a self-driven synchronous rectifier circuit with a transformer having a primary winding and a secondary winding, said secondary winding having a first and second terminal, said method comprising the steps of:

• providing the varying signal to said primary winding of said transformer;
• a first synchronous rectifier conducting current via a second terminal of said second winding;
• a first switch controlling said first synchronous rectifier;
• a second synchronous rectifier conducting current via said first terminal of said second winding;
• a second switch controlling said second synchronous rectifier;
• wherein said first and second switches are connected to said first synchronous rectifier and said second synchronous rectifier, respectively, such that switching transitions of said first and second synchronous rectifiers are initiated by a polarity reversal of the voltage of said secondary transformer winding.