Output conduction detection in a buck converter

Abstract

An integrated controller for a buck converter has an output conduction detector circuit that provides the input or high side of the controller with visibility of the discharge period and thereby prevents continuous current mode operation in case of a short-circuited output. The controller receives a feedback signal indicative of an output voltage of the buck converter and produces an input drive signal. A bias drive circuit receives the input drive signal and produces a bias drive signal. A bias supply circuit includes a bias transistor and a bias diode. The bias drive transistor receives the bias drive signal to enter a conducting state when the bias drive signal is asserted. The output conduction detector circuit detects an output conduction event as a voltage drop across the bias transistor, due to conduction of freewheeling current through either the bias transistor or bias diode, and produces an output conduction signal.