Patent ID: 9575456
Date: 2017-02-21
CPC Classifications: G03G

Claim:
1. An image forming apparatus comprising: a power source portion configured to convert an AC voltage of a commercial power source into a DC voltage; a fixing portion configured to heat and fix an image, formed on a recording material, on the recording material, wherein said fixing portion includes a first heat generating element which generates heat by electric power supplied from the commercial power source and a second heat generating element which is controlled independently of the first heat generating element and which generates the heat by the electric power supplied from the commercial power source; and a controller configured to control the electric power supplied to the first and second heat generating elements, wherein when a plurality of periods of an AC waveform of the commercial power source constitute one control period, said controller sets a waveform of a current to be passed through each of the first and second heat generating elements in the one control period so that the total electric power supplied to the first and second heat generating elements in the one control period is dependent on the temperature of said fixing portion, wherein said controller sets the waveform of the current to be passed through each of the first and second heat generating elements so that, in a synchronous half wave in the one control period, when the current passes through one of the first and second heat generating elements from a halfway point of the half wave, the current either passes or does not pass through the other heat generating element throughout a period of the half wave, depending on a duty ratio of the total electric power supplied to said first and second heat generating elements, and wherein said controller sets a current supply starting timing of the current passing through the one of the first and second heat generating elements from the halfway point of the half wave, at a timing when a current passing toward said power source portion stops.