Minimum Output Ripple and Fixed Operating Frequency Based on Modulation Injection for COT Ripple Control Converter

This paper proposes a minimum output ripple and fixed operating frequency technique based on the modulation injection for a constant on-time (COT) ripple control converter. Basically, the modulation injection approach aims to add a modulation signal to the output inductor to fix the operating frequency on the discontinuous conduction mode (DCM) and does not affect the inductor current ripple injection. Moreover, the spread spectrum of pulse width modulation (PWM) method is also applied to reduce the electromagnetic interference (EMI) noise. The illustrative simulation results indicate that the proposed converter operates stably at a fixed switching frequency (1.6MHz), and the output ripple is kept very small (5mVpp). EMI noise levels are also kept below 50mV, which is compared to 5V desired voltage.