Patent ID: 7984309

Claim:
A power supply system comprising: a first device that commands an external device to perform processing, and is configured to supply electric power to the external device; a second device that is connected to the first device through a communications line, and that performs the processing in accordance with the command received from the first device; and a request unit that requests the first device to supply to the second device an amount of electric power needed for the second device performing the processing commanded by the first device, the first device determining whether or not to supply electric power to the second device, in accordance with at least one of; content of the command sent to the second device, and the amount of electric power requested by the request unit and an amount of electric power which the first device is capable of supplying, wherein the second device comprises an internal power unit configured to supply electric power, which is different from the electric power to be supplied from the first device, to the second device, and the first device commands the second device to use the internal power unit in a case where the amount of electric power required by the request unit exceeds the amount of electric power which the first device is capable of supplying.