Buck converter with quasi-fixed-frequency constant on-time architecture and on-timing circuit

Abstract

An on-timing circuit includes a current generation module, an inversion delay counteracting module, a capacitor, and a comparator, wherein the current generation module is configured to generate a charging current in direct proportion to a voltage of a switch node after an upper power transistor is turned on; the inversion delay counteracting module is configured to generate a first delay for counteracting an inversion delay of the comparator according to a variable resistance unit and the capacitor, and a resistance value of the variable resistance unit is controlled by an input voltage; the capacitor is configured to be charged by the charging current after the upper power transistor is turned on; and the comparator is configured to compare a ramp voltage corresponding to a ramp voltage node with a first voltage and generate a turn-off signal, and the first voltage is a reference voltage in proportion to an output voltage.