POWER SUPPLY DEVICE, POWER SUPPLY METHOD, AND NON-TRANSITORY COMPUTER-READABLE MEDIUM

Provided is a power supply device including a capacitor, a pre-charge circuit and a control circuit. The capacitor is connected in series with a contactor that is connected between an inverter driving a motor and a battery and that switches on or off power supply from the battery to the inverter, and is connected in parallel with the inverter. The pre-charge circuit is connected in parallel with the contactor and pre-charges the capacitor. The control circuit controls the pre-charge circuit and the contactor. The control circuit includes a sensor that measures the voltage of the battery and the voltage of the capacitor, and determines whether the pre-charge is necessary according to whether a ratio of the voltage of the capacitor to the voltage of the battery is equal to or less than a target value.