1. Field of the Invention
The present invention relates to a lamp controller for controlling what is called a lighting state of a lamp provided on a vehicle such as an automobile, the lighting state specifically meaning whether the lamp is lit on or lit off and how the light is distributed, and in particular relates to a lamp controller that is preferably applicable to lamps of an automobile that runs on electric power from a battery (electric cell).
2. Description of Related Art
In a vehicle such as an electric automobile or hybrid automobile, in which at least part of the electric power supplied from an on-vehicle battery is used to drive the vehicle, this battery is also utilized as power supply to light various lamps including headlamps and tail lamps. It is desirable for such a vehicle to suppress the power consumed by these lamps in order to ensure traveling of the vehicle or to improve the mileage even when the remaining charge of the battery becomes low. Some techniques have been proposed to control the lighting state of lamps in a vehicle that runs on electric power supplied from a battery in order to suppress the power consumed by the lamps when the remaining charge of the battery becomes low. Japanese Patent Application Publication No. 2006-188122 (JP 2006-188122 A) proposes a technique wherein the supply of power to lamps is automatically controlled or automatically stopped by detecting a remaining charge of the battery and the ambient light of the outside of the vehicle so that safety is ensured for the vehicle by illumination with the lamps while saving the power consumption of the lamps.
While the technique of JP 2006-188122 A is described in terms of application to headlamps of an automobile, this technique is actually a technique to automatically control or automatically turn off a plurality of lamps collectively. Therefore, when the technique of JP 2006-188122 A is applied to headlamps each including a low-beam lamp and a high-beam lamp, for example, light amounts of the high-beam lamps and low-beam lamps are reduced simultaneously once the remaining charge of the battery becomes low. On the other hand, when the technique of JP 2006-188122 A is applied to both headlamps and tail lamps, light amounts of both of the headlamps and tail lamps are reduced at the same time, or all of the headlamps and tail lamps are turned off. If the light amounts of all the lamps are simultaneously reduced, or all the lamps are turned off, it may become difficult to secure safety of the automobile by illumination of the lamps.