Power supply apparatus and these-use electric vehicle

In a power supply apparatus for a vehicle is an inverting circuit (30a), a voltage of a first battery unit (10) through switches (24a, 24b) a. A smoothing capacitor (31) is provided in parallel between the first battery unit and the inverter. A DC-DC converter (50) is provided between the smoothing capacitor and a second battery unit (60) to spannungszuwandeln electrical energy which is stored in the first battery unit or the smoothing capacitor, for supply to the second battery unit and to electrical energy, which in the second battery unit is stored, spannungszuwandeln to supply the smoothing capacitor. An electronic control unit (80) controls / regulates the DC-DC converter before starting the power supply to the inverter circuit, so that the switches are closed after the smoothing capacitor is charged to a voltage within a predetermined allowable voltage range of the voltage of the first battery unit.