Digital autotuning controller for point-of-load converter based on non-intrusive start-up transient observer

A new method for online estimation of power-stage parameters and autotuning of feedback controller for point-of-load (POL) converter is presented in this paper. The autotuning controller presented has been specifically developed to handle wide variations of the resonant frequency of LoCooutput filter and the equivalent series resistance (ESR) zero of output capacitor. The resonant frequency of LoCooutput filter and the time constant of output capacitor's ESR zero are estimated by examining the start-up transient response of converter and online measurement of steady-state output voltage ripple, respectively, hence the proposed method is non-intrusive and does not affect converter's normal operation. Based on these results, digital compensator is automatically tuned based on some user defined phase margin and crossover frequency to provide the desired transient response and output voltage regulation over wide variations of power-stage parameters. Simulation and experimental results from a 12 V-to-1.5 V, 22.5 W, 500 kHz digitally controlled POL buck converter are provided to verify the effectiveness of the proposed method.