DEVICE FOR CONTROLLING BACKLIGHT, PARTICULARLY REGARDING TO CONTROLLING ON/OFF OF BACKLIGHT ACCORDING TO EXISTENCE OF PERIPHERAL LIGHT

摘要

PURPOSE: A device for controlling a backlight is provided to control on/off of the backlight according to existence of peripheral light without operating a key button or folder, thereby easily controlling the backlight in the dark. CONSTITUTION: A photo transistor(310) is mounted between a power source voltage and a ground, and is formed of photosensitive collector-base PN(Positive-Negative) junction so that the photo transistor executes switching action by generating a current at a base terminal if light enters a photosensitive surface. An SCR(Silicon Controlled Rectifier)(320) is formed of four-layer P-N-P-N junction and is turned on and off by the switching action of the photo transistor. A switch part(330) provides a path of a driving current according to control of the SCR. An LED(Light Emitting Diode)(340) emits light as a backlight of a key pad and an LCD(Liquid Crystal Display) if receiving the driving current.