Small signal analysis and design of active droop control using current mode equivalent circuit model

This paper proposes a small signal model for active droop control in equivalent circuit form. Active droop control is an average current mode control with proportional output voltage feedback. The proposed model takes the switching ripple of the voltage and current feedback into account, and the model is valid up to half of switching frequency. The features of the active droop controlled converters with ESR dominant capacitor and ceramic capacitor are identified. Design guidelines of the compensator and external ramp are proposed to simplify the compensator, maximize the control bandwidth and reduce the output capacitor numbers. The over designed external ramp complicates the loop design and degrades the performance. The model is applicable to different modulations.