| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a light emitting circuit which can provide controllable luminance over a wide range and can control luminance with high precision even in a case of low level luminance. SOLUTION: An analog voltage AV of 0 to 2 V is output from a D/A converter 20 and is given to a voltage current conversion part 30 in accordance with a digital value DV of 0 to 31 given from a light emitting control part 10. A drive current DI output from the voltage current conversion part 30 is controlled in 1 mA unit in a scope of 0 to 31 mA in accordance with the digital value DV. On the other hand, a drive current DI1 of a voltage current conversion part 40 is controlled in 4 mA unit in a scope of 0 to 124 mA, and a drive current DI1 of a voltage current conversion part 50 is controlled in 20 mA unit in a scope of 0 to 620 mA. Consequently, it is possible to control luminance of an LED 1 precisely over a wide scope even at a low level by turning on and off and controlling the voltage current conversion parts 40, 50 by scope specifying signals C1, C2.</p> |
