Ripple Compensation Based On COT Control Mode

In the traditional Constant-On-Time (COT) control mode, the output bypass capacitor mostly uses ceramic capacitors, and its equivalent series resistance (ESR) is small, the phase of output voltage ripple lags behind the inductor current, causing system instability. For this reason, this paper adopts the ripple compensation technology. By injecting the external ramp and the internal inductor current ramp, a virtual resistance is introduced for the ESR, and the resistance value of the ESR is increased to meet the stability conditions. The chip is designed based on 18V 0.1Sum BCD process. The simulation results show that when the input voltage is 12V and the temperature is 27°C, the system conversion efficiency can reach 97%, and the system output voltage ripple is about 3.4mV.