| 摘要 |
PURPOSE:To automatically or manually adjust the brightness of a back light in accordance with peripheral brightness and to obtain an always easily observable screen by adjusting the brightness of the back light through a brightness adjusting means. CONSTITUTION:Voltage supplied from a power supply 32 is switched to the side of an outside light brightness detecting circuit 37 for automatically adjusting brightness through the movable iron chip (a) and fixed contacts (b), (c) of a switch 38 for automatically or manually switching the voltage or the side of a variable resistor 35 for manually adjusting brightness. The brightness of the back light 23 disposed on the back of a liquid crystal panel on a liquid crystal display device is detected by the brightness adjuster 27 such as a cds and adjusted based upon the detection output of the adjuster 27. Since the outer light brightness detector 27 such as the cds is included in the circuit 37 and its resistance value is changed in accordance with outside light, the change value is extracted as the voltage change of a brightness adjusting variable resistor 42 to drive a back light driving circuit 39. |
