Patent ID: 8046613

Claim:
A power control system comprising: a main system that controls the power control system; a sub system that is connected to the main system in a communicatable manner and that implements various functions; and a power control unit, wherein the main system includes a power mode designating unit that outputs an operation mode designating signal that designates either one of a normal operation mode and a power-saving mode to the sub system, and the sub system includes a control unit that controls the sub system, and a sub power control unit that supplies, in the normal operation mode, a first voltage with which driving of the control unit is possible to the control unit, and while in the power-saving mode, supplies a second voltage that is lower than the first voltage, with which driving of the control unit is impossible but retention of a condition is possible, to the control unit, the power control unit supplying a voltage to the sub power control unit, when shifting to the power-saving mode is possible, the control unit outputs a power-saving mode shift enable signal indicating that shifting to the power-saving mode is possible to the sub power control unit, and when the operation mode designating signal designates the power-saving mode and the power-saving mode shift enable signal indicates that shifting to the power-saving mode is possible, the sub power control unit supplies the second voltage to the control unit.