Fixed‐frequency adaptive on‐time buck converter with ramp compensation

Abstract

This study presents a fixed-frequency adaptive on-time buck converter with adaptive ramp compensation internally, which uses valley current-mode control. The on-time is obtained by feed forwarding input voltage and output voltage, which is easy to implement. The control method provides fast transient response, wide duty ratio and high efficiency for both heavy and light load. In a traditional adaptive on-time buck converter, the output voltage ripple determines the moment when the main power metal oxide semiconductor field effect transistor is being turned on. Different from that way, this study proposes a new way by which the valley current flowing through the inductor determines the moment. This avoids the problem induced by insufficient output ripple when a low equivalent series resistance capacitor like ceramic output capacitor is used. An adequate and simple ramp compensation circuit is proposed to optimise its jitter performance for wide duty ratio applications.