Patent ID: 8494383

Claim:
An image forming apparatus, comprising: a fixing part configured to heat-fix an unfixed toner image formed on a recording material to the recording material, the fixing part comprising a heater that generates heat by power supplied from a commercial AC power supply; a temperature sensing element configured to sense a temperature of the fixing part; a power control part configured to control the power supplied from the commercial AC power supply to the heater according to the temperature sensed by the temperature sensing element, wherein the power control part selects a power level of a control pattern from a plurality of power levels of control patterns according to the sensed temperature per a segment of a control period, the duration of a segment of the control period being determined by a predetermined number of consecutive half-cycles in an AC wave form, and the plurality of power levels depends on a combination of a phase control pattern and a wave number control pattern; and a current detection part provided in a power supply path from the commercial AC power supply to the heater, configured to detect a current flowing in the power supply path, the current detection part comprising a transformer and a current detection circuit configured to detect the current via the transformer, wherein the current detection part is further configured to detect current corresponding to the combination of phase control pattern and the wave number control pattern and at least a part of the plurality of power levels includes: both a first group of wave forms in which power is supplied in both at least a part of a negative half-cycle and at least a part of a positive half-cycle in order just after the absence of supply of power during an entirety of a positive half-cycle, and a second group of wave forms in which power is supplied in at least a part of a positive half-cycle just after the absence of supply of power during an entirety of a negative half-cycle, or both a first group of wave forms in which power is supplied in both at least a part of a positive half-cycle and at least a part of a negative half-cycle in order just after the absence of supply of power during an entirety of a negative half cycle, and a second group of wave forms in which power is supplied in at least a part of a negative half-cycle just after the absence of supply of power during an entirety of one half of a positive half-cycle.