Heating device and image forming apparatus with fixing device switched on/off in response to a zero-cross point of an AC voltage output from an AC power source

摘要

A controller outputs a heater control signal in synchronization with a rise in a zero-cross signal. In response to the heater control signal, a switching device of a heater driving circuit switches ON/OFF. However, a noise occurs in an output voltage of an AC power source at the time of switching, and this noise causes a false zero-cross signal. For the purpose of preventing operation of a heater in accordance with the false zero-cross signal, the controller disregards the rise in the zero-cross signal during a set time period after the rise in the heater control signal.