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.

主权项

1. A constant on-time controller used in a switching converter, wherein the switching converter includes a first switch, a second switch, an inductor and an output capacitor, and is configured to convert an input voltage into an output voltage, the controller comprises:
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 coupled to the ramp compensation generator, wherein the comparing circuit compares the sum of the compensation signal and a feedback signal indicative of the output voltage with a reference signal to generate a comparison signal; a logic circuit coupled to the on-time control circuit and the comparing circuit, wherein based on the on-time control signal and the comparison signal, the logic circuit generates a control signal with a duty cycle; a driving circuit coupled to the logic circuit, wherein based on the control signal, the driving circuit generates a first driving signal and a second driving signal to respectively drive the first switch and the second switch; and a feed forward circuit configured to generate a compensation control signal based on the input voltage; wherein the ramp compensation generator is coupled to the feed forward circuit and configured to adjust the compensation signal based on the compensation control signal.