To enable one of a low power mode power source and a high power mode power source to be selected to supply a power source to a load unit, and thereby to achieve a good power-saving effect.

The load unit 5 is configured to perform a switching operation between a normal mode and a power-saving mode based on an instruction to switch between the normal mode and the power-saving mode. A first power source unit 1 is configured to generate a first power source V1 for a power-saving mode to be supplied to the load unit 5, by means of an external power source 13. A second power source unit 3 is configured to generate a second power source V2 whose voltage is higher than that of the first power source V1, for a normal mode to be supplied to the load unit 5, by means of the external power source 13. The power source control unit 9 is configured to control the start-up of the second power source unit 3 based on the switching instruction, and output the second power source V2 to the load unit 5. A block unit 11 is configured to supply the first power source V1 to the load unit 5, and in response to the output of the second power source V2, to block the input of the second power source V2 into the first power source unit 1.