Design and Analysis of Combined Input-Voltage Feedforward and PI Controllers for the Buck Converter

This paper presents the design and analysis of combining input-voltage feedforward and proportional-integral (PI) controllers to regulate the output voltage of DC-DC Buck converter subject to input line disturbances. Non-idealities of the Buck converter such as passive and active components parasitics are included in the mathematical model obtained by the state-space averaging (SSA) technique for accurate control. The stability boundary locus approach is used to graphically analyze the system stability. It guides the design of the PI controller gains and the feedforward scaling factor to achieve desired phase and gain margins. Analysis shows that the feedforward scaling factor affects the stability regions of the closed-loop system and can limit the possible PI controller gains for certain phase and gain margins; 75 degrees and 9.54 dB in our case. The results are verified by a Simulink model developed for the Buck converter system.