Auto-tuning and self-calibration techniques for V2 control with capacitor current ramp compensation using lossless capacitor current sensing

Recently, capacitor current ramp compensation, which features fastest transient response, has been proposed to stabilize V² control with low equivalent-series-resistance (ESR) capacitor. However, it is found that the design of capacitor current sensing gain and the time-constant mismatch of sensing network may lead to oscillatory or slow transient response, so both issues are investigated in this paper to improve the control scheme. Firstly, the small signal model based on describing function is derived to identify the effect of capacitor current sensing gain on the system stability and transient performance. Secondly, based on the knowledge from this accurate model, a simple auto-tuning technique is developed to optimize the current sensing gain over possible parameter variations by detecting the transient response of output voltage. Thirdly, two easy self-calibration techniques are proposed to correct the time constant mismatch during output voltage scaling. Finally, the effectiveness of proposed methods is verified by SIMPLIS simulation and experimental results.