Abstract: An overvoltage protection circuit prevents a voltage higher than an allowable voltage value from being supplied to a predetermined to-be-protected circuit. A voltage is applied from outside to an input end 11. A cathode terminal of a zener diode 13 is connected to the input end 11. A first resistance element 14 is connected between an anode terminal of the zener diode 13 and a ground terminal. A voltage detection integrated circuit 15 detects a voltage between both ends of the zener diode 13, and outputs a detection signal that indicates whether or not the detected voltage is higher than the allowable voltage value. When the detection signal indicates that the detected voltage is no higher than the allowable voltage value, a MOSFET 16 supplies the to-be-protected circuit with the voltage applied to the input end 11.

Abstract: An overvoltage protection circuit prevents a voltage higher than an allowable voltage value from being supplied to a predetermined to-be-protected circuit. A voltage is applied from outside to an input end 11. A cathode terminal of a zener diode 13 is connected to the input end 11. A first resistance element 14 is connected between an anode terminal of the zener diode 13 and a ground terminal. A voltage detection integrated circuit 15 detects a voltage between both ends of the zener diode 13, and outputs a detection signal that indicates whether or not the detected voltage is higher than the allowable voltage value. When the detection signal indicates that the detected voltage is no higher than the allowable voltage value, a MOSFET 16 supplies the to-be-protected circuit with the voltage applied to the input end 11.