Patent ID: 8803368

Claim:
An image forming apparatus, comprising: a universal interface to connect to at least one type of option unit; a power supply unit; a plurality of switches along a power supply path between the option unit and the power supply unit; and a control unit to identify a type of option unit using identification (ID) information pre-stored in a memory of the option unit, the ID information including the type of option unit and an allowed power level of the type of option unit, the control unit to control on/off states of the plurality of switches to supply power to the option unit corresponding to the identified type of option unit, wherein the control unit activates the option unit by controlling the plurality of switches to supply to the option unit maximum power when the option unit is connected to the universal interface and identifies the type of the option unit after receiving the ID information from the activated option unit and adjusts on/off states of the plurality of switches to supply to the option unit power corresponding to the identified type of option unit.