A SMALL DIRECT SC AC-AC CONVERTER WITH CASCADE TOPOLOGY

To realize a small inductor-less AC-AC converter, this paper presents a cascade direct AC-AC converter using switched-capacitor (SC) techniques. The proposed AC-AC converter has cascade topology, where converter blocks with the conversion ratio of 1/2 or 2 are connected in series. Owing to the cascade topology, multiple conversion is performed to realize high conversion ratio. Furthermore, each converter block consists of only two capacitors and four switches, because no flying capacitor is necessary to realize AC-AC conversion. By reducing the number of capacitors, the proposed converter can achieve smaller circuit components and higher input power factor than conventional converters. To clarify the effectiveness of the proposed AC-AC converter, characteristic evaluation was performed by using simulation program with integrated circuit emphasis (SPICE) simulations and theoretical analysis. In the conversion ratio of 1/4, the SPICE simulation result demonstrated that the proposed AC-AC converter can improve 8% power efficiency and 0.4 input power factor from the conventional direct AC-AC converter using flying capacitors.