IMAGE FORMING APPARATUS

An image forming apparatus: acquires, before start of current supply to electric elements including heater, information indicating rated power of the heater and total consumption power of the electric elements excluding the heater; subtracts the total consumption power from upper power limit of the apparatus, and calculates maximum power not exceeding the rated power and remaining power thus subtracted; obtains duty ratio based on assumption of current supply corresponding to the maximum power according to pulse modulation, and determines whether the duty ratio falls within predetermined range; and controls, when the duty ratio falls within the range, drive circuit to supply alternating current by pulse modulation method, and when the duty ratio falls outside the range, to supply the alternating current by phase control method that temporarily interrupts the supply of the alternating current to the heater in half cycles of the alternating current.