| 摘要 |
<P>PROBLEM TO BE SOLVED: To enable manually finely adjust or manually adjust the light emission quantity when the light emission quantity of light emitting diode is automatically adjusted based on the brightness of surroundings in a backlight of a liquid crystal display, for example. <P>SOLUTION: When a transistor Q1 is turned on, the current in accordance with the detected light quantity of a photodiodo 7 is generated. In this case a control voltage generation circuit 3 outputs a potential difference between an output voltage of a voltage generation circuit 2 and a voltage to be generated based on the generated current of the photodiode 7 as a control voltage. An LED current control circuit 5 controls the current flowing through a light emitting diode 6 based on the control voltage. On the other hand, when the transistor Q1 is turned off, the operation of the photodiode 7 is stopped. In this case the control voltage generation circuit 3 outputs the output voltage of the voltage generation circuit 2 as the control voltage, and controls the current flowing through the light emitting diode 6 based on the control voltage. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
