PI and Sliding Mode Control of a Cuk Converter

Proportional-integral (PI) and sliding mode controls are combined to regulate a fourth-order Cuk converter in a continuous conduction mode. A closed-loop system is obtained with the aid of the equivalent control method. Based on the Routh-Hurwitz stability criterion and root locus, the appropriate PI gains are obtained and a stable and robust system suitable for large signal variations is achieved. The minimum or nonminimum phase behavior of the closed-loop system and the transients of the closed- loop system under step variations of various circuit parameters are analyzed. Under a wide range of operating points, the Cuk converter under the proposed controller has a load voltage tracking accuracy within ±0.05 V with a moderate maximum switching frequency of not greater than 100 KHz. The merits and demerits of the proposed controller are compared with some other controllers.