A synchronous rectifying type DC-DC converter including an auxiliary winding, provided on a secondary side of a transformer, for supplying voltages assuming polarities opposite to each other to control terminals of a rectifying switch and of a fly wheel switch, and the rectifying switch...http://www.google.com/patents/US6169675?utm_source=gb-gplus-sharePatent US6169675 - DC/DC converter with improved operation of plural parallel synchronous rectifiers 
