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Design of a nesting-type switched-capacitor AC/DC converter using voltage equalizers
Author(s)
Date Issued
January 1, 2017
Type
Article
Abstract
For electric appliances, an electric circuit that changes an alternating current (ac) into a direct current (dc) is necessary. Among others, a small and light ac/dc converter is indispensable to develop novel mobile devices. As one of the most promising design approaches, the ac/dc converter designed by switched-capacitor (SC) techniques attracts many researchers’ attention, because the SC ac/dc converter can be implemented without a high turn ratio transformer. Owing to the heavy transformer-less design, the SC ac/dc converter can realize smaller size and lighter weight than traditional ac/dc con-verters. However, the SC ac/dc converter suffers from complexity of the circuit control and the inflexibility of conversion ratio. To overcome these problems, this paper proposes a nesting-type SC ac/dc converter using voltage equalizers. Unlike conventional SC ac/dc converters, the proposed converter consists of a full waveform rectifier with a big capaci-tor and nested voltage equalizers. In the nested voltage equalizers, a part of the capacitor voltage of a voltage equalizer is converted by other voltage equalizers, where each voltage equalizer is controlled by non-overlapped two-phase clock pulses. By the nesting conver-sion, the conversion ratio of the proposed converter is expressed as a reverse value of the total sum of main capacitors’ voltage ratios. Therefore, the proposed converter can achieve not only simple circuit control but also flexible conversion ratios. Concerning the 1/9× step-down SC ac/dc converter, the advantages of the proposed converter were investigated by theoretical analysis, simulated program with integrated circuit emphasis (SPICE) simulations, and experiments. First, mathematical formulas for estimating the characteristics of the proposed converter were derived theoretically by utilizing a simple four equivalent circuit. Then, by comparing the proposed converter with conventional SC ac/dc converters, the effectiveness of the proposed converter was clarified by SPICE simulations. Finally, the feasibility of the proposed converter was confirmed by using the experimental circuit implemented on a breadboard.
Citation
International Journal of Innovative Computing Information and Control, 13(4), 1369-1384, 2017