Patent ID: 6459595
Filing Date: 2002-10-01
Classification: H02M

Abstract:
A method of generating, in addition to a main output DC voltage, at least one additional output DC voltage in a flyback DC/DC converter having a transformer with a primary winding connected in series with a primary switch to an input DC voltage source, a first secondary winding connected in series with a first rectifier to a first output capacitor for generating said main output DC voltage across said first output capacitor, and a secondary winding connected in series with a second rectifier to a second output capacitor, for generating said additional output DC voltage across said second output capacitor, wherein said second rectifier is a synchronous rectifier, the method comprising:turning on said synchronous rectifier in response to current generated in a flyback operation of the second secondary winding traversing said synchronous rectifier; comparing the actual value of said additional output DC voltage with a desired value; and adjusting the turn-off time of the synchronous rectifier in response to the ratio between the actual value and the desired value to adjust the actual value to the desired value.