Constant on-time switching converter with adaptive ramp compensation and control method thereof

摘要

A COT switching converter includes a first switch, a second switch, an inductor, an on-time control circuit configured to generate an on-time control signal, a ramp compensation generator configured to generate a compensation signal, a comparing circuit, a logic circuit, a driving circuit and a feed forward circuit configured to generate a compensation control signal based on the input voltage of the switching circuit. The comparing circuit compares the sum of the compensation signal and a feedback signal with a reference signal to generate a comparison signal. Based on the on-time control signal and the comparison signal, the logic circuit generates a control signal with a duty cycle to drive the first and second switches through the driving circuit. The ramp compensation generator adjusts the compensation signal based on the compensation control signal, so the amplitude of the ramp compensation signal can follow a critical value proportional to the difference between the duty cycle and the square of the duty cycle.