this paper proposes an AC/AC power converter that expands the output voltage range. The proposed circuit has two operation modes. One is a step-down mode that supplies the output voltage which is lower than the input voltage. The other is a boost mode that supplies the output voltage which is higher than the input voltage. In the boost mode, the proposed circuit has characteristics of the current type inverter, so that it is possible to obtain an output voltage with less harmonics. This paper also clarifies the control method to realize a smooth mode transition from the buck mode to the boost mode. The validity of the proposed system is confirmed with a 1.5 kW prototype. The proposed circuit shows that the input / output voltage ratio of AC / AC direct conversion obtained is 0 to 1.2 or more. Moreover, the conversion efficiency of the proposed circuit is 95.7%, which is a 0.35% improvement over the conventional Back-to-Back system.