| 摘要 |
PURPOSE:To prevent brightness from being lower than necessary and also to prevent the operation time of a battery from being shortened by varying a control method for display brightness in accordance with the conditions of a power supply circuit such as the using situation of the battery, a change in the residual capacity of the battery, etc. CONSTITUTION:A brightness control circuit is disposed in a power supply device 11, and power consumption is detected and the display brightness is controlled by a microcomputer 111 in the device 11, and also the using situation of the battery 13 and the residual capacity of the battery 13 are detected so as to vary the brightness controlling method. When the battery 13 is in use, the brightness is controlled so as to be made lower, and the power consumption is saved, and in the case that an AC adapter 2 is connected, the battery 13 is not used, and the brightness is controlled so as to become the maximum brightness in a state where the heat does not increase more than a fixed degree. Thus, the brightness can be prevented from being lower than necessary and also the operation time of the battery 13 can be prevented from being shortened.
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