POWER SUPPLY DEVICE FOR ELECTRIC VEHICLE AND CONTROL METHOD FOR SAME

An electrically powered vehicle (5) has a main battery (10) and an auxiliary battery (70) mounted therein. In external charging, a charging device (200) performs AC/DC power conversion converting power received from an external power supply (400) into power charged to main battery (10). A sub charging relay (SCR1, SCR2) is connected between a predetermined node (N1, N2) on an electric conduction path of the charging device (200) in the AC/DC power conversion and the auxiliary battery (70). The sub charging relay (SCR1, SCR2) is turned off in the external charging. The charging device (200) is configured such that when the external charging is not performed and the sub charging relay (SCR1, SCR2) is turned on the charging device performs DC/DC power conversion to convert power of the main battery (10) via at least a portion of the electric conduction path in the AC/DC power conversion into power to be charged to the auxiliary battery (70) and outputs the converted power on the predetermined node (N1, N2).