Patent ID: 7750512

Claim:
An image forming apparatus comprising: a board comprising a plurality of functional units; a first power source circuit configured to output a first voltage; a second power source circuit configured to output a second voltage which is lower than the first voltage; a power switching unit configured to selectively activate the first power source circuit and the second power source circuit, individually; a third power source circuit mounted on the board and configured to convert the first voltage input from the first power source circuit into operation voltages to operate respective functional units; a mode switching unit configured to select one of power modes, the power modes including a first mode in which a first unit group comprising at least one of the plurality of functional units is activated and a second mode in which a second unit group comprising at least one of the plurality of functional units is activated; and a control unit, wherein, in the first mode, the control unit is operable to: control the power switching unit to activate the first power source circuit; input the first voltage to the third power source circuit; and supply the operation voltage converted by the third power source circuit to the first unit group, and wherein, in the second mode, the control unit is operable to: control the power switching unit to activate the second power source circuit and to deactivate the first power source circuit; and supply the second voltage output from the second power source circuit to the second unit group without intervention of the third power source circuit.