Patent ID: 7705541

Claim:
A light control circuit comprising: an illuminance sensor that detects the illuminance of surrounding light; a light-emitting device; and a driving control circuit that controls the amount of emitted light of the light-emitting device corresponding to the illuminance detected by the illuminance sensor so as to cause the light-emitting device to emit light, wherein the illuminance sensor is a current output type sensor that outputs a current which increases or decreases in an analog manner corresponding to an increasing or decreasing change of the illuminance, the light-emitting device is connected with a detection resistor that detects a current flowing through the light-emitting device, the driving control circuit has a light-emitting device driver that outputs to the light-emitting device a voltage for holding a voltage, which is obtained when a current flowing through the light-emitting device and a current detected by the illuminance sensor flows through the detection resistor, in a predetermined value all the time, and the light-emitting device emits a large amount of light in a dark place and emits a small amount of light in a bright place.