Design of a Step-Down Non-Isolated DC-DC n-Cell Converter With a High Reduction Ratio

Abstract

In this paper, a multistage DC-DC buck converter with a high reduction ratio, based on the concept of switched inductance, is presented. The proposed converter offers a significantly higher reduction ratio than conventional step-down converters. The analysis and design of the proposed multistage converter are considered for three operating regions, i.e., continuous conduction mode, boundary conduction mode, and discontinuous conduction mode. Besides, an averaged model is obtained, based on the analysis of the conduction modes. Also, a model-based control strategy is proposed to meet the proposed control objectives. Thus, a control law is designed that results in a two-control loop controller, i.e., a current control loop and a voltage control loop are proposed. A comparison is carried out in terms of efficiency, number of components, and type of control to highlight the advantages and disadvantages of the proposed converter. Finally, an experimental prototype is built to assess the proposal performance, reducing from an input voltage of 200 V to an output voltage of 12 V. The closed-loop converter is evaluated in an experimental setup under steady-state and transient conditions.

Keywords

• DC-DC high gain step-down converter
• switched inductors
• model-based control
• multi-stage converter