Digital two-loop controller design for fourth order split-inductor converter

In this paper a digital two-loop controller design methodology is proposed for the fourth order split inductor converter load voltage regulation. The salient features of the split-inductor converter are compared with the conventional SEPIC converter and then discrete-time mathematical models are established. Digital two-loop controller, inner current-loop and outer voltage-loop, is designed using direct digital design approach. A two-pole two-zero compensator is adopted in the outer voltage-loop, while one-pole and one zero is used in the inner current-loop design. Compensator design is validated through simulations and then experimental measurements. Load voltage regulation characteristics are obtained against line and load perturbations. A 25 watt 15 to 36 V prototype converter is built and experimental investigations are carried out. The measured results obtained from the prototype converter are in close agreement with those obtained in the analysis.