Patent ID: 6438009
Filing Date: 2002-08-20
Classification: H02M,Y02B

Abstract:
Apparatus for use in a fly-back DC/DC converter, comprising:a MOSFET used as a synchronous rectifier and which is coupled to a secondary winding of a transformer for generating an output DC voltage, where the MOSFET is repetitively turned on and off in response to turning off and on of a primary switch coupled to a primary winding of the transformer and to an input DC voltage source; a first transistor coupled to a gate of the MOSFET for controlling when the MOSFET is turned on and off; a first capacitor coupled between a drain of the MOSFET and the first transistor for turning the first transistor on and off; and a second capacitor coupled to the MOSFET drain and arranged to be charged to a peak voltage of a transient caused by a reverse current generated when the MOSFET is turned off, wherein the charged second capacitor causes a voltage across the first capacitor to change so that the first transistor turns on to decrease a next on-period for the MOSFET.