| 摘要 |
PURPOSE:To improve visibility with stabilized, unchanged luminous intensity of a backlight bulb regardless of battery voltage change by applying, when a lighting switch is off, the output from the battery and when the lighting switch is on, the output from a constant voltage circuit, to the bulb. CONSTITUTION:When an ignition switch 5 is on and a lighting switch 6 is off because of bright surroundings, the output of a battery 7 is directly applied to a bulb 2 by way of the ignition switch 5 and a continuously closing contact point of a relay 3. Then the bulb is lighted in the brightest condition. If the lighting switch 6 is turned on when the surroundings become dark, the relay 3 is energized and switched to the continuously opening contact side so that stabilized output from a constant voltage circuit 8 is applied to the bulb 2. This output is adjusted to a value for lighting the bulb 2 at a relatively dark, specified luminous intensity and does not change even if the output voltage of a battery 7 changes. Thus, a display of stabilized, good visibility and high commercial quality and value is obtained. |
