Patent ID: 7706708

Claim:
An image forming apparatus comprising: an image forming apparatus main body; and at least one option apparatus that is mounted on the image forming apparatus main body when functions are extended, wherein the image forming apparatus main body comprises: a main power supply unit configured to convert a commercial power supply into a predetermined voltage; a first load that is driven on the basis of electric power supplied from the main power supply unit; a first auxiliary power supply that is charged by the commercial power supply; and a fixing device including a main heater that is heated on the basis of electric power supplied from the commercial power supply and an auxiliary heater that is heated on the basis of electric power supplied from the first auxiliary power supply, and the at least one option apparatus comprises: a second load that is driven on the basis of electric power supplied from the main power supply unit when the at least one option apparatus is mounted on the image forming apparatus main body; and a second auxiliary power supply that is charged by the commercial power supply when the at least one option apparatus is mounted on the image forming apparatus main body and, on the other hand, heats the auxiliary heater in conjunction with the first auxiliary power supply.