Autotuning Techniques for Digitally Controlled Point-of-Load Converters with Wide Range of Capacitive Loads

摘要

This paper addresses auto-tuning of digitalcontrollers for point-of-load (POL) switching converters withwide range of capacitive loads. Two auto-tuning methods areconsidered with particular attention given to robustness andfeasibility. The first method is derived from the well knownrelay-feedback autotuning technique, where specific frequenciesare excited to gain information on the power stage. In the second,system-identification based method, compensator parameters arecomputed based on on-line identification of the power stagefrequency response. The tuning techniques proposed in thispaper have been specifically developed to handle widecapacitance and ESR range, and important extensions of thebasic algorithms are implemented in order to face practicalissues such as limit cycling conditions, output voltage tolerancespecification, closed-loop bandwidth maximization and phasemargin constraints. Simulation and experimental results on a 12-to-1.5 V, 9 A, 200 kHz POL converter are provided to show theeffectiveness and to compare the considered techniques.