POWER SUPPLY DEVICE AND METHOD THEREOF FOR FUEL CELL

The power supply device is configured on an aircraft and includes a secondary battery, a transformer, a fuel cell and a bypass switch. The transformer is electrically connected between the secondary battery and the aircraft. The fuel cell is suitable for providing a first output current to the aircraft. The bypass switch is connected in parallel with the transformer. The transformer has a first output voltage set value. When a first output terminal voltage of the fuel cell is lower than the first output voltage set value and the bypass switch is in a non-conducting state, a second output current of the secondary battery is provided to the aircraft via the transformer. When the first output terminal voltage is lower than the first output voltage set value and the bypass switch is in a conducting state, the second output current is provided to the aircraft via the bypass switch.