Power supply device and control method for power supply device

A power supply device comprising:

• a battery circuit module group in which a plurality of battery circuit modules are connected in series via their output terminals, each battery circuit module including:
• a battery;
• its output terminal through which a voltage of the battery is to be output;
• a first switching element connected to the output terminal and connected in parallel to the battery;
• and
• a second switching element connected in series to the battery between the battery and the first switching element, the second switching element being configured to be turned off when the first switching element is turned on;
• and
• a control circuit configured to:
• output, at intervals of a certain time, a gate signal for turning on and off the first switching element and the second switching element of each battery circuit module to the battery circuit modules in the battery circuit module group;
• and
• select one of the battery circuit modules that receives an input of the gate signal to output a predetermined voltage from the power supply device.