| 摘要 |
PROBLEM TO BE SOLVED: To vary the light emitting quantity of a light-emitting element so as to keep visibility according to the variation of brightness in the surrounding when the brightness varies, by increasing the light-emitting quantity of the light-emitting element when the luminance of the light emitting element being a load is lowered in a simple constitution obtained by adding light-receiving elements to a stabilized power supply circuit. SOLUTION: A light-receiving element 17 is provided in parallel to a pressure dividing resistor 26 which divides the output voltage of the stabilized power supply circuit 20, and a light-receiving element 18 is provided in parallel to a pressure dividing resistor 27. The light-receiving element 17 receives light of the load 15, and the light-receiving element 18 receives the ambient light. The output voltage of the stabilized power supply circuit 20 is boosted when a light quantity received by the light-receiving element 17 decreases, and drops when the light quantity received by the light-receiving element 18 decreases. COPYRIGHT: (C)2008,JPO&INPIT
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