| 摘要 |
PROBLEM TO BE SOLVED: To provide an image forming apparatus configured to slow temperature increase during abnormal condition when a temperature of a short heating element is excessively increased, without reducing temperature controllability of the heating element in normal operation.SOLUTION: When power is supplied to a short heating element 35b of heating elements 35a, 35b having different lengths and generating heat with power supplied from an AC power source 41, every time a voltage level of a zero-cross signal is changed, a mask signal of a predetermined pulse width is output. The mask signal forcibly turns off a triac drive circuit td of a triac 44 which supplies power to the heating element 35b. Phase control is performed, while preventing the heating element 35b from being supplied with power at a predetermined Duty or higher. Temperature of the heating element 35b, which has been excessively heated in abnormal operation, is slowly increased without reducing temperature controllability (temperature ripple) in normal operation. |
