Patent ID: 6151233
Filing Date: 2000-11-21
Classification: H02M,Y02B

Abstract:
A synchronous rectifier circuit, comprising:an output terminal for providing an output;a first switch, having a ratio of conduction period to cut-off period controlled in accordance with the output at the output terminal;an inducing element, connected to said first switch, for storing an energy of a first current flowing therethrough;a rectifier element, connected to said inducing element;a second switch, connected in parallel with said rectifier element, said second switch being conductive so as not to overlap with the conduction period of said first switch; andcontrol means for cutting off said second switch just before an energy stored in said inducing element is completely released regardless of whether said first switch is conductive or cut-off, the energy being stored in said inducing element while said first switch is conductive,said inducing element is provided between an input terminal and the output terminal, said first switch is provided between said inducing element and the input terminal, and said rectifier element has a terminal which is connected between said first switch and said inducing element and has a polarity for maintaining the first current,said control means controlling said second switch so as to satisfyT2off<=Ton.multidot.(Vin-Vout)/Vout,where Vin is a voltage of the input terminal, Vout is a voltage of the output terminal, Ton is a conduction time of said first switch, and T2off is a period between cut-off of said first switch and cut-off of said second switch.