To prevent the functional deterioration of a photosensitive element in the case where it has reached unallowable operation state, and remove the necessity of an external restart control pin, and raise the robust property of start management, by detecting the temperature of the element and controlling the enabling of the element.

The reverse input 24.2 of a comparator 24 is coupled with voltage reference dependent upon temperature, and a voltage reference 30 dependent upon temperature is coupled with a temperature sensor 32 which detects the temperature of an element 12. The current generated in a current source 14 flows through a line 15, and charges a capacitor 16. Hereby, it follows that the potential Vcc goes up continuously. Once the potential Vcc gets over the voltage at the voltage standard 28, a comparator 26 is switched hereby, and it sends out corresponding output signals to output 26.3. This output signal is transmitted to the element 12 through a control line 11. As a result, the operation of the element 12 is enabled.