LIGHT SENSING CIRCUIT, BACKLIGHT CONTROL APPARATUS HAVING THE SAME, AND LIQUID CRYSTAL DISPLAY DEVICE HAVING THE SAME

• US 20100327286A1
• Filed: 08/27/2010
• Published: 12/30/2010
• Est. Priority Date: 06/23/2006
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: Moon, Su-Hwan, Yoon, Jeong-Won
• Granted Patent: US 7,961,181 B2
• Time in Patent Office: Days
• US Class Current: 257/59
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2360/144 the light being ambient light
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336

Abstract

A light sensing circuit capable of enhancing a reliability by lowering a dependency on a temperature change without using a resistor, a backlight control apparatus having the same, and an LCD device having the same. The light sensing circuit includes a first MOS-transistor; and a second MOS-transistor serially connected to the first MOS-transistor between a first power terminal and a ground terminal, in which a second power terminal is connected to each gate terminal of the first MOS-transistor and the second MOS-transistor, and an optical amount detecting terminal is connected to a common connection point between a drain terminal of the first MOS-transistor and a source terminal of the second MOS-transistor.

Claims

1. A light sensing circuit, comprising:

a first metal oxide semiconductor (MOS)-transistor; and

a second MOS-transistor serially connected to the first MOS-transistor between a first power terminal and a ground terminal,

wherein a second power terminal is connected to each gate terminal of the first MOS-transistor and the second MOS-transistor, and an optical amount detecting terminal is connected to a common connection point between a drain terminal of the first MOS-transistor and a source terminal of the second MOS-transistor.

2. The light sensing circuit of claim 1, wherein the first MOS-transistor and the second MOS-transistor respectively comprise an amorphous-silicon type MOS-transistor.

3. The light sensing circuit of claim 1, wherein the first MOS-transistor and the second MOS-transistor are disposed at an edge of an LC panel.

4. The light sensing circuit of claim 1, wherein the first MOS-transistor is disposed so as to be exposed to external light, and the second MOS-transistor is disposed so as not to be exposed to external light.

5. The light sensing circuit of claim 1, further comprising a black matrix for shielding external light positioned at an upper portion of the second MOS-transistor.

6. The light sensing circuit of claim 1, further comprising an optical amount detecting terminal (V_d) connected to the a common connection point.