AC VOLTAGE DETECTION CIRCUIT, HEATER CONTROL DEVICE AND IMAGE FORMING DEVICE

摘要

When a partial pressure exceeding a Zener voltage of a Zener diode is applied to a first limiting circuit by a positive voltage applied to input terminals by an AC power supply, the first limiting circuit allows a current such that a photo transistor of the first detection circuit is turned on. When a partial pressure exceeding a total value of Zener voltages of Zener diodes is applied to a second limiting circuit by a negative voltage applied to the input terminals, the second limiting circuit allows a current such that a photo transistor of a second detection circuit is turned on. Therefore, it is possible to detect a voltage input from the AC power supply by turning on and off the photo transistors and to detect a voltage input from the AC power supply using a simpler circuit configuration.