| 摘要 |
PURPOSE:To prolong the usable time of a battery by switching the brightness of a back-light so as to reduce the power consumption of the back-light when the voltage of the battery drops below a prescribed level. CONSTITUTION:A system control circuit 10 switches the brightness of a back- light 12 for illuminating a liquid crystal display panel 6 based on the detected result of an outside light sensor 8. Namely, when the circumference is bright, the brightness of the back-light 12 is increased so as to increase the brightness of a picture displayed on the panel 6 and, when the circumference is dark, the brightness of the back-light 12 is decreased so as to decrease the brightness of the picture. In addition, the circuit 10 detects the voltage V of a battery 2 and, when the voltage V drops below a prescribed reference level, decreases the brightness of the back-light 12 so as to reduce the power consumption of the back-light 12. Therefore, the usable time of the battery can be prolonged. |
