ENERGY REPORTS, vol.6, pp.173-178, 2020 (Journal Indexed in SCI)
In this paper, we present an inductor-less direct ac-ac converter with improved nesting-type topology. Unlike existing direct ac-ac converters, the proposed ac-ac converter combines a voltage equalizer and a switched-capacitor (SC) simple converter. Owing to the nesting conversion using two techniques, the proposed converter can provide a stepped-down voltage with small number of circuit components and high input power factor. To evaluate the performance of the proposed ac-ac converter, we compared the proposed ac-ac converter with existing inductor-less ac-ac converters, namely, flying capacitor type converter, symmetrical type converter, and traditional nesting-type converter, by theoretical analysis and simulation program with integrated circuit emphasis (SPICE) simulations. The SPICE simulations demonstrate that the proposed ac-ac converter outperforms existing inductor-less ac-ac converters in the point of circuit size and input power factor, although the power efficiency of the proposed ac-ac converter is inferior to that of the symmetrical type converter. In the case of 1/4x voltage gain, the proposed ac-ac converter achieves about 82% power efficiency and 0.58 input power factor when the output power is 200 W. (C) 2019 Published by Elsevier Ltd.