Proportional-Integral (PI) Compensator Design of Duty-Cycle-Controlled Buck LED Driver

A discrete time-domain modeling and design for the duty-cycle-controlled buck light-emitting diode (LED) driver is presented in this paper. The discrete time-domain equation representing the buck LED driver is derived and linearized about the equilibrium state. Also the switching control law, the proportional-integral (PI) compensator is used here as an example of the error amplifier, is linearized about the equilibrium state. The linearized buck LED driver and the control law are then combined to arrive at a linearized duty-cycle-controlled buck LED driver. The root-locus method is employed to analyze the dynamic performance of the closed-loop system. Based on the modeling result, a practical design equation for the PI compensator is derived. Experimental results are presented to verify the validity of the proposed PI compensator design.