Patent ID: 7173831
Filing Date: 2007-02-06
Classification: H02M,Y02B

Abstract:
1. An apparatus, comprising: a transformer having a primary winding and a secondary winding; a switching circuit, including a primary active switch and a capacitor commonly coupled in parallel between a primary ground and the primary winding, to facilitate a periodic application of an input voltage to the primary winding; a synchronous rectification circuit coupled to the secondary winding to generate a rectified signal; an output filter coupled to the synchronous rectification circuit to provide an output voltage in response to the rectified signal; the synchronous rectification circuit includes a bi-directional switch coupled in series between the secondary winding and the output filter and a shunt active switch coupled in parallel with the output filter; a control circuit, coupled to the output filter, the synchronous rectification circuit, and the primary active switch, and responsive to the output voltage to provide a first control signal to the primary active switch to regulate the output voltage by varying a conductive state of the primary active switch; the control circuit further arranged to provide a second control signal to the bi-directional switch to control a conductive state of the bi-directional switch; and the conducting state for the bi-directional switch extending for a first time period after an end of the conducting state for the primary active switch.