Light sensing circuit, backlight control apparatus having the same, and liquid crystal display device having the same

• US 7,804,481 B2
• Filed: 12/28/2006
• Issued: 09/28/2010
• 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
• Primary Examiner(s): Hjerpe; Richard
• Assistant Examiner(s): Steinberg; Jeffrey S
• Application Number:
  US11/646,715
• Publication Number:
  US 20070296687A1
• Time in Patent Office: 1,370 Days
• Field of Search: 345/102
• US Class Current: 345/102
• 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 liquid crystal display (LCD) device, comprising:

an LC panel including a first region having a plurality of pixel region to display image and a second region in the outside of the first region;

a backlight that irradiates light a rear side of the LC panel;

an inverter that supplies an output power to the backlight;

a light sensing circuit that detects an amount of external light introduced to the LC panel by a first metal oxide semiconductor (MOS)-transistor and a second MOS-transistor serially connected to each other;

an inverter driving controller that controls a driving of an inverter based on a voltage corresponding to the optical amount from the light sensing circuit;

a second power terminal connected to each gate terminal of the first MOS-transistor and the second MOS-transistor; and

an optical amount detecting terminal connected to a common connection point between a drain terminal of the first MOS-transistor and a source terminal of the second MOS-transistor,

wherein the light sensing circuit is constructed so that the first MOS-transistor and the second MOS-transistor are serially connected to each other between a first power terminal and a ground terminal,

wherein the first MOS-transistor and the second MOS-transistor are disposed in the second region so that the first MOS-transistor is exposed to external light and the second MOS-transistor is not exposed to external light.

2. The LCD device of claim 1, wherein the first MOS-transistor and the second MOS-transistor comprise an amorphous-silicon type MOS-transistor.

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

4. The LCD device of claim 1, wherein the LC panel comprises:

a lower substrate on which the first MOS-transistor and the second MOS-transistor are formed;

an upper substrate adjacent the lower substrate, and comprising a black matrix of a lattice shape thereon; and

an LC layer positioned between the upper substrate and the lower substrate,

wherein the black matrix is disposed on the upper substrate corresponding to the second MOS-transistor, and the black matrix is removed on the upper substrate corresponding to the first MOS-transistor.

5. The LCD device of claim 4, further comprising a polarizer respectively coupled onto an outer surface of the upper substrate and an outer surface the lower substrate, and wherein the polarizer attached onto the lower substrate is removed at a region corresponding to the first MOS-transistor.

6. A liquid crystal display (LCD) device, comprising:

an LC panel including a first region having a plurality of pixel region to display image and a second region in the outside of the first region;

means for irradiating a rear side of the LC panel;

means for supplying an output power to a backlight;

means for detecting an amount of external light introduced to the LC panel by a first metal oxide semiconductor (MOS)-transistor and a second MOS-transistor serially connected to each other;

means for controlling a driving of an inverter based on a voltage corresponding to the optical amount from the detecting means;

a second power terminal connected to each gate terminal of the first MOS-transistor and the second MOS-transistor; and

an optical amount detecting terminal connected to a common connection point between a drain terminal of the first MOS-transistor and a source terminal of the second MOS-transistor,

wherein the detecting means is constructed so that the first MOS-transistor and the second MOS-transistor are serially connected to each other between a first power terminal and a ground terminal,

wherein the first MOS-transistor and the second MOS-transistor are disposed in the second region so that the first MOS-transistor is exposed to external light and the second MOS-transistor is not exposed to external light.

7. The LCD device of claim 6, wherein the first MOS-transistor and the second MOS-transistor comprise an amorphous-silicon type MOS-transistor.

8. The LCD device of claim 6, wherein the first MOS-transistor and the second MOS-transistor are disposed at an edge of an LC panel.

9. The LCD device of claim 6, wherein the LC panel comprises:

a lower substrate on which the first MOS-transistor and the second MOS-transistor are formed;

an upper substrate adjacent the lower substrate, and comprising a black matrix of a lattice shape thereon; and

an LC layer positioned between the upper substrate and the lower substrate,

wherein the black matrix is disposed on the upper substrate corresponding to the second MOS-transistor, and the black matrix is removed on the upper substrate corresponding to the first MOS-transistor.

10. The LCD device of claim 9, further comprising a polarizer respectively coupled onto an outer surface of the upper substrate and an outer surface the lower substrate, and wherein the polarizer attached onto the lower substrate is removed at a region corresponding to the first MOS-transistor.