Transfer function‐matched capacitor‐current sensing and its circuit implementation for high‐frequency power converters

Abstract

It would effectively achieve a fast load transient response in switching-mode power converters when introducing capacitor current into the feedback control loop. In these schemes, an accurate and rapid sensing of capacitor current is crucial in the control circuit design. On this issue, a paralleled nonintrusive sensing scheme for capacitor current is proposed in this paper, which is implemented by matching the transfer functions of the sensing circuit and the sensed capacitor branch. With the proposed transfer function matching approach, 4 possible circuit topologies are derived in theory, and on this basis, a parameter design flow chart is given for 2 of candidate topologies. With the application of the proposed capacitor-current sensing circuit to a constant-frequency hysteresis controlled Buck converter, a fast and accurate sensing of capacitor current is achieved in experiment, as well as a fast load transient response.