Constant on-time controller

摘要

A constant on-time controller, comprising a ripple generator, a comparing circuit and a logic control circuit, is provided. The ripple generator generates a ripple signal, which is injected into one of a voltage reference signal and a voltage detection signal to form a ripple modulated signal with ripple information. The comparing circuit compares the ripple modulated signal with the other of the voltage reference signal and the voltage detection signal and accordingly generates a comparison result signal. The logic control circuit generates a control signal with a fixed pulse width according to the comparison result signal. The ripple generator has a level modulation circuit for modulating an amplitude of the ripple modulated signal to make the amplitude within an preset range under different applications.

主权项

1. A constant on-time controller, adapted to control a converting circuit to switch for generating an output voltage, comprising:
a ripple generator, generating a ripple signal according to a first signal having a component in response to a current flowing through an inductance of the converting circuit and a second signal having a component in response to the output voltage or the current of the inductance, wherein an amplitude of the second signal is smaller than an amplitude of the first signal when the second signal has the component in response to the current of the inductance, and the ripple generator comprises a level modulation circuit to and modulates the levels of the first signal and the second signal according to an amplitude of the ripple signal; a comparing circuit, receiving the ripple signal, a voltage reference signal and a voltage detection signal indicative of the output voltage, and modulating one of the voltage reference signal and the voltage detection signal according to the ripple signal for generating a ripple modulated signal with a ripple information of the ripple signal, and the comparing circuit comparing the ripple modulated signal with the other of the voltage reference signal and the voltage detection signal for generating a comparison result signal; and a logic control circuit, generating a control signal with fixed pulse width according to the comparison result signal for controlling the switching of the converting circuit.