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

This paper presents a robust control strategy for a Buck-type DC–DC (BTDCDC) converter under voltage-mode control (VMC) 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: (i) 2-DOF control structure comprises PID controller and a pre-filter, which provides additional flexibility to improve the output voltage set-point tracking despite model variations (ii) Low transient inductor current, leads to subsequent reduced losses (iii) Inclusion of disturbance dynamics and an unstructured uncertainty in the controller loop-shaping design itself (iv) Reduced output voltage deviation for source and load disturbances (v) 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 faster. HF noise attenuation is also significantly improved.