| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide an illuminance sensor which is prevented from malfunctioning due to disturbance light. SOLUTION: This sensor is equipped with a photodiode D, a converting- amplifying part 10, for converting a photoelectric current into a voltage and amplifying it by a fitly selectable amplification factor; a comparison part 20 for comparing an amplified voltage Vin, outputted from the amplifying part 10 with a reference voltage Vref to output a binary output voltage signal Vout, in response to the result of the comparison, and thereby controlling the opening/ closing of an external triac Q for switching between a power supplying state to a lighting load Lp and a power supply stopped state; and a selection part 11 for selecting a value of the voltage Vin, corresponding to the brightness of outside light, according to the voltage signal Vout fed back from the comparison part 20. Even when the amplification factor of the amplifying part 10 is set appropriately so as to cause the comparison part to control the opening/ closing of the external triac Q in dim outside lighting conditions, a disturbance light tolerance L is kept at or higher than a prescribed quantity by the selection part 10, and malfunctions due to fluctuations in external light and due to disturbance light can be prevented.</p> |
