초록 ▼

A back light circuit for a liquid crystal display (LCD) includes: an alternating current (AC) adapter, a battery for supplying a direct current (DC) when the alternating current (AC) adapter is not used, an adapter detecting unit for determining whether or not the alternating current (AC) adapter is

A back light circuit for a liquid crystal display (LCD) includes: an alternating current (AC) adapter, a battery for supplying a direct current (DC) when the alternating current (AC) adapter is not used, an adapter detecting unit for determining whether or not the alternating current (AC) adapter is being used, a direct current/direct current (DC/DC) converter for providing output of a switched signal, a direct current/alternating current (DC/AC) converter for driving a cold cathode fluorescent lamp (CCFL) by increasing an electric potential, a cold cathode fluorescent lamp (CCFL) operated by the direct current/alternating current (DC/AC) converter, an on/off controller for controlling the direct current/direct current (DC/DC) converter, a brightness controller for controlling the brightness of the cold cathode fluorescent lamp (CCFL), a feedback unit for providing feed back signals to the direct current/direct current (DC/DC) converter, a brightness condition detector for determining the brightness condition of the back-light of the liquid crystal display (LCD), a low battery/very low battery (LB/LLB) signal transmitter for generating a signal indicating the residual amount of battery power when the battery is being used, and a brightness condition controller for determining a brightness condition of the back light of the liquid crystal display (LCD). The back light of the liquid crystal display (LCD) is adjusted based on the condition of the battery, and further based on whether the alternating current (AC) adapter is being used.

대표청구항 ▼

[ What is claimed is:] [1.] A back light circuit for a liquid crystal display, said circuit comprising:an alternating current adapter for receiving alternating current and converting said alternating current to generate a direct current;a battery for providing said direct current when said alternati

[ What is claimed is:] [1.] A back light circuit for a liquid crystal display, said circuit comprising:an alternating current adapter for receiving alternating current and converting said alternating current to generate a direct current;a battery for providing said direct current when said alternating current adapter is not being used to generate said direct current;an adapter detecting unit for determining whether said alternating current adapter is being used to generate said direct current;a direct current/direct current converter for receiving said direct current and providing output of a switched signal via a switching regulator;a direct current/alternating current converter for driving a cold cathode fluorescent lamp by generating an increased electric potential after converting said switched signal output from said direct current/direct current converter;said cold cathode fluorescent lamp operated by said direct current/alternating current converter for providing back light for said liquid crystal display;an on/off controller for controlling driving of said direct current/direct current converter to interrupt operation of said cold cathode fluorescent lamp;a brightness controller having a first current channel for controlling a degree of brightness of said back light provided by said cold cathode fluorescent lamp;a feedback unit for receiving an output signal from said brightness controller and providing said output signal from said brightness controller to said direct current/direct current converter;a brightness condition detector for determining said degree of brightness of said back light based on said output signal from said brightness controller;a battery signal transmitter for generating signals indicating a residual amount of battery power when said battery is being used to provide said direct current; anda brightness condition controller having second, third and fourth current channels for determining and controlling said degree of brightness of said back light in response to signals output from said adapter detector, said battery signal transmitter and said brightness condition detector.