Control device for rectifiers of switching converters

Abstract

A control device detects zero crossings of a current through a rectifier transistor during plural cycles; generates a turn-on signal of the transistor and inserts a turn-on delay equal to a fixed first quantity from the start time of for each cycle. The control device starts counting consecutive cycles after inserting the turn-on delay; detects whether a zero crossing of the current through the transistor after turning on said transistor has occurred; if no zero crossing is detected before counting a number N of consecutive cycles, decreases the turn-on delay by a fixed second quantity for the next cycle; if a zero crossing is detected, maintains turned on the transistor; if the turn-on delay is smaller than first quantity, increases the turn-on delay o for the next switching cycle; and if the turn-on delay is equal to the first quantity, maintains the turn-on delay for the next switching cycle.