An adaptive ramp compensation scheme to improve stability for DC-DC converters with ripple-based constant on-time control

This paper proposes an adaptive compensation scheme for buck converters with ripple-based constant on-time control in order to eliminate the sub-harmonic oscillation. In comparison with traditional ramp compensation approaches, the new scheme reduces the required compensation to avoid sub-harmonic oscillation by alternating cycles to provide ramp compensation. Also, more importantly, amplitude of the compensation ramp is adaptively adjusted according to feedback of off-time difference. This minimizes the ramp amplitude at steady state, and thus, reduces the impact on transient response. In addition to theoretical analysis, experimental results verify the effect of the proposed approach.