Quantitative Feedback Design Based Robust 2-DOF PID Control of Voltage Mode Controlled DC–DC Buck Converter With Unstructured Uncertainty and Sensor Noise Suppression

Abstract

This article presents a robust control strategy for a Buck-type dc–dc (BTdcdc) converter under voltage-mode control using only output-voltage feedback. Robust control design is challenging due to parametric and unstructured uncertainties, set-point tracking, source-voltage and load disturbances, and high-frequency (HF) sensor noise. To address these issues, a Quantitative Feedback Theory (QFT) based two-degree-of-freedom (2-DOF) control architecture is developed. The advantages of the proposed QFT approach are: 1) 2-DOF control structure comprises PID controller and a prefilter, which provides additional flexibility to improve the output voltage set-point tracking despite model variations. 2) Low transient inductor current leads to subsequent reduced losses. 3) Inclusion of disturbance dynamics and an unstructured uncertainty in the controller loop-shaping design itself. 4) Reduced output voltage deviation for source and load disturbances. 5) Improved suppression of HF sensor noise with less peak-to-peak inductor current and duty ratio variation. Experimental validation on a BTdcdc prototype confirms superior tracking and regulation performance. For source-voltage disturbances, the proposed method reduces peak voltage deviation by 30% –50% and achieves settling times 4–8 times faster. HF noise attenuation is also significantly improved.