Patent ID: 6841977
Filing Date: 2005-01-11
Classification: H02M,Y02B,Y10S

Abstract:
1. In a system having a buck converter comprising a switch, an inductor, a capacitor and a synchronous rectifier, said buck converter having two input terminals to which an input DC voltage is coupled and two output terminals where the output DC voltage is provided, said synchronous rectifier having a control input and being controlled such that when said switch is open, current through said inductor is maintained by a path provided by said synchronous rectifier, and having a pulse width modulator (PWM) having an output designed to provide control of the state of said synchronous rectifier; a control circuit coupled between said PWM output and said control input of said synchronous rectifier for controlling said synchronous rectifier during a predetermined condition, comprising: a comparator circuit for comparing a feedback signal indicative of said predetermined condition to a predetermined reference voltage, such that said comparator circuit outputs a control signal when said predetermined condition is active; and a driver circuit responsive to said control signal to prevent said PWM from controlling the state of said synchronous rectifier when said predetermined condition is active; said driver circuit responsive to said control signal to change the state of said synchronous rectifier to off if said synchronous rectifier is on when said predetermined condition is active and to maintain the off state of said synchronous rectifier if said synchronous rectifier is off when said predetermined condition is active.