Power source device

A power source device for a vehicle, the device comprising:

• at least one first battery;
• at least one second battery, the voltage of which is lower than that of the first battery, wherein a device that is activated at least during charging is connected to the second battery;
• a control circuit connected to the first battery via a line, the control circuit controlling a load;
• a system main relay provided on the line;
• and
• a charger connected to a part of the line between the system main relay and the first battery, the charger being capable of charging the first battery using an external alternating-current power source,
• wherein the charger includes:
• a transformer having a primary coil, to which an alternating-current power source is connected, at least one first secondary coil, to which the first battery is connected, and at least one second secondary coil, to which the second battery is connected;
• a first power conversion circuit located between the primary coil of the transformer and the alternating-current power source;
• a second power conversion circuit located between the primary coil of the transformer and the first power conversion circuit;
• a third power conversion circuit located between the first secondary coil and the first battery;
• a rectification circuit located between the second secondary coil and the second battery;
• a voltage adjustment circuit located between the rectification circuit and the second battery;
• and
• a control section that charges, in a state where the system main relay is open, the first battery using the alternating-current power source, and, simultaneously supplies electrical power to the second battery.