Comparative analysis and control design of two non-isolated DC-DC converters with high reduction ratio

In this paper, two step-down converters with a high reduction ratio based on the concept of switched inductors and switched capacitors are analyzed, modeled, and controlled. These topologies can achieve a high-voltage step-down ratio compared to a conventional buck converter. The proposed topologies have the same conversion ratio in terms of the duty cycle, however, they have different operating principles, and thus, different design, modeling, and control strategies must be followed. Therefore, the guidelines for the design of these types of converters are proposed here. Furthermore, to show the benefits of selected topologies, a comparison between them and other topologies with similar voltage ratios is presented. The comparison is made regarding the number of semiconductors, number of passive elements, and switch electrical stress. Besides, model-based control strategies are proposed for both converters. The modeling process yields a second-order system for the switched inductor-based converter structure and a fourth-order system for the switched capacitor-based converter. Based on these models, control laws are designed resulting in multi-loop controllers, formed by inner and outer control loops. These control schemes are aimed to guarantee output voltage regulation and, therefore, zero steady-state error of the states in each system. Finally, the performance of the proposed control strategies and converters is evaluated on an experimental setup.