Closed-Loop Model Reference Tuning of PID Regulators for Digitally Controlled dc-dc Converters based on Duty-Cycle Perturbation

This paper investigates a model reference tuning for digitally controlled dc-dc converters based on duty-cycle perturbation. Tuning is performed by exciting the system with a perturbation at the desired crossover frequency while maintaining the system in closed-loop configuration. The difference between the output of the real system and the reference model is used to set regulator parameters to obtain the desired stability margin and crossover frequency. The main advantages of the proposed technique are closed-loop operation during tuning process, good precision in presence of sampling noise, no need of high resolution A/D converters, independence of the method on the converter topology and small signal processing requirements, as dictated by the cost/complexity constraints existing in integrated digital controller. Both simulation and experimental results on a synchronous buck converter confirm the effectiveness of the proposed solution.