Constant on-time buck converter with calibrated ripple injection having improved light load transient response and reduced output capacitor size

Abstract

According to an aspect of one or more exemplary embodiments, there is provided a constant on-time buck converter with calibrated ripple injection having improved light load transient response and reduced output capacitor size. The constant on-time buck converter may include a controller having a pulse width modulator (PWM) comparator that generates an on-time request, an error amplifier that regulates an average feedback voltage to an internal reference voltage, and passes a feedback node ripple signal to an input of the PWM comparator, an on-time generator that outputs an on-time signal that controls an on-time of the buck converter based on the on-time request, a MOSFET driver that drives the buck converter based on the output of the on-time generator, a zero crossing detection circuit configured to detect when a current through an inductor of the buck converter equals zero, and an injection signal generator coupled to the on-time generator, and that is configured to output an injection signal that limits a dip in an output voltage of the buck converter during a load transient based on an output of the zero crossing detection circuit indicating that the current through the inductor of the buck converter equals zero. The error amplifier may receive a feedback voltage based on the output of the injection signal generator and based on the output voltage of the buck converter.