Patent ID: 7889521
Filing Date: 2011-02-15
Classification: H02M,Y02B

Abstract:
1. A three-pin integrated synchronous rectifier, comprising: a first electric connection point; a second electric connection point; a third electric connection point; a power transistor having a first output/input terminal, a second output/input terminal and a control terminal, wherein the first output/input terminal is coupled with the first electric connection point, and the second output/input terminal is coupled with the second electric connection point; and a synchronous rectifying control circuit for controlling the electric status of the power transistor and having an input control terminal, two detection terminals, and an output terminal, wherein the input control terminal is coupled with the third electric connection point, the two detection terminals respectively are coupled with the first output/input terminal and the second output/input terminal of the power transistor, and the output terminal is coupled with the control terminal of the power transistor; wherein the synchronous rectifying control circuit comprises: (i) a detection circuit coupled with the first output/input terminal and the second output/input terminal to form the two detection terminals and used for detecting a current flowing through the power transistor, wherein the detection circuit outputs a turn-off signal when the current is smaller than the pre-determined current; (ii) a delay circuit coupled with the detection circuit and outputting a confirm signal when the turn-off signal lasts a first pre-determined period; and (iii) a driver coupled with the delay circuit and the input control terminal, wherein the driver turns the power transistor on when the driver receives a synchronous signal at the input control terminal, and the driver turns the power transistor off when the driver receives the confirm signal; wherein, the synchronous rectifying control circuit turns the power transistor on when the synchronous rectifying control circuit receives the synchronous signal at the input control terminal, and the synchronous rectifying control circuit turns the power transistor off when the synchronous rectifying control circuit detects that the current flowing through the power transistor is smaller than a pre-determined current by the two detection terminals.