KR101730849B1 - liquid crystal display device and method of driving the same - Google Patents

Abstract

The present invention relates to a liquid crystal display device, comprising: a liquid crystal panel; An LED array which supplies light to the liquid crystal panel and is divided into a plurality of strings composed of a plurality of LEDs; And a lamp driver for applying different currents to the plurality of strings.

Description

[0001] The present invention relates to a liquid crystal display device and a method of driving the same,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device and a driving method thereof.

2. Description of the Related Art [0002] With the development of an information society, demands for a display device for displaying images have been increasing in various forms. Recently, a liquid crystal display (LCD), a plasma display panel (PDP) Various flat display devices such as an organic light emitting diode (OLED) have been utilized.

Of these flat panel display devices, liquid crystal display devices are widely used today because they have advantages of miniaturization, weight reduction, thinness, and low power driving. On the other hand, an active matrix type liquid crystal display device in which a plurality of pixels are arranged in a matrix and thin film transistors are formed in each of these pixels is widely used today.

In recent years, a liquid crystal display device realizes ultra-high picture quality of a large screen of a large screen. Further, in order to provide a clearer image quality of the liquid crystal display device, the backlight is driven by a plurality of lamps.

However, when the same current is applied to a plurality of light source elements constituting the backlight, darkness is generated in the corner portions of the liquid crystal panel.

That is, as shown in FIG. 1, when the same current is applied to the LED array formed in a single row or a plurality of columns, for example, part darkness is generated at corner portions of the liquid crystal panel unlike the other portions.

The present invention has a problem to reproduce a liquid crystal display device and a driving method thereof for improving a partial darkness occurring at corner portions of a liquid crystal panel.

Accordingly, there is a problem in improving brightness and providing a clearer image quality.

According to an aspect of the present invention, there is provided a liquid crystal display comprising: a liquid crystal panel; An LED array which supplies light to the liquid crystal panel and is divided into a plurality of strings composed of a plurality of LEDs; And a lamp driver for applying different currents to the plurality of strings.

The lamp driving unit applies a current higher than the current applied to the other strings to the strings corresponding to the corner portions of the liquid crystal panel.

The current applied to the string corresponding to the corner portion of the liquid crystal panel is 10% to 15% higher than the current applied to the other strings.

The LED array is located at one side, both sides or four sides of the liquid crystal panel.

A method of driving a liquid crystal display device including a liquid crystal panel and an LED array which supplies light to the liquid crystal panel and is divided into a plurality of strings composed of a plurality of LEDs, And a method of driving the liquid crystal display device.

A current higher than the current applied to the other strings is applied to the strings corresponding to the corner portions of the liquid crystal panel.

The current applied to the string corresponding to the corner portion of the liquid crystal panel is 10% to 15% higher than the current applied to the other strings.

The LED array is located at one side, both sides or four sides of the liquid crystal panel.

The liquid crystal display device according to the present invention provides an effect of improving the darkness of corner portions of the liquid crystal panel by applying a higher current to the LED array corresponding to the corner portion of the liquid crystal panel.

Further, since the darkness of the corner portion of the liquid crystal panel is improved, a clearer liquid crystal panel can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view schematically showing the darkness of a corner portion of a liquid crystal panel generated in a conventional liquid crystal display device. Fig.
2 is a cross-sectional view schematically showing a liquid crystal display device according to an embodiment of the present invention.
3 is an equivalent circuit diagram of a pixel according to an embodiment of the present invention.
4 is an exploded perspective view of a backlight according to an embodiment of the present invention.
5 is a cross-sectional view schematically showing an RGB type LED as an example.
6 is a cross-sectional view schematically showing an LED array as an example.
7 is a cross-sectional view schematically illustrating a liquid crystal panel and an LED array according to an embodiment of the present invention.
FIG. 8 is a schematic view illustrating a liquid crystal display device improved in darkness at a corner portion of a liquid crystal panel according to an embodiment of the present invention. FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is a schematic diagram of a liquid crystal display device according to an embodiment of the present invention, and FIG. 3 is an equivalent circuit diagram of a pixel of a liquid crystal display device according to an embodiment of the present invention.

A liquid crystal display device 100 according to an embodiment of the present invention includes a liquid crystal panel 200, a backlight unit 900, and a driving circuit unit D.

The liquid crystal panel 200 is provided with a plurality of gate lines GL extending along a row line direction and a plurality of data lines DL extending along a column line direction. The gate wiring GL and the data wiring DL intersect with each other to define a pixel P in the form of a matrix.

Each pixel P includes a thin film transistor T, a pixel electrode, a common electrode, a liquid crystal capacitor Clc, and a storage capacitor Cst.

The thin film transistor T is formed at the intersection of the gate line GL and the data line DL. The thin film transistor T is connected to the pixel electrode. On the other hand, a common electrode is formed corresponding to the pixel electrode. When a data voltage is applied to the pixel electrode and a common voltage is applied to the common electrode, an electric field is formed therebetween to drive the liquid crystal. The pixel electrode, the common electrode, and the liquid crystal located between these electrodes constitute a liquid crystal capacitor Clc.

Each pixel P further includes a storage capacitor Cst, which serves to store the data voltage applied to the pixel electrode until the next frame.

Each pixel P may be composed of R, G, and B subpixels displaying red, green, and blue, for example. That is, the neighboring R, G, and B sub-pixels constitute a pixel that is a unit of image display.

The backlight 900 serves to supply light to the liquid crystal panel 200.

This will be described in detail with reference to Fig. 4 is an exploded perspective view of a backlight 900 according to an embodiment of the present invention.

A backlight 900 is provided on the back surface of the liquid crystal panel 200 to supply light from the backside of the liquid crystal panel 200 so that the difference in transmittance represented by the liquid crystal panel 200 is externally expressed.

Here, the backlight 900 is divided into an edge type and a direct type according to the arrangement structure of the light sources. In the edge type, one or a pair of light sources are disposed on one side of the light guide plate 901 And two edges 2Edge having a structure in which two or two pairs of light sources are disposed on both side portions of the light guide plate 901. As shown in Fig.

Further, there are four edges (4Edge) having a structure in which four or four pairs of light sources are disposed on each of four sides of the light guide plate (901).

 The direct type has a structure in which several light sources are disposed under the optical sheet 902.

In recent years, the edge type is more suitable for the lightweight thin type liquid crystal display device than the direct type in the state where the research of the lightweight thin type liquid crystal display device is progressing actively according to the demand of the consumer in recent years.

The backlight 900 includes a cold cathode fluorescent lamp (CCFL), an external electrode fluorescent lamp, and a light emitting diode (LED) use.

In particular, the LED 903a has characteristics such as small size, low power consumption, and high reliability, and is widely used as a display light source.

The backlight 900 of the present invention includes an LED assembly 903, a white or silver reflective plate 904, a light guide plate 901 seated on the reflective plate 904, and a plurality of optical sheets (902).

The LED assembly 903 includes a plurality of LEDs 903a, a plurality of LEDs 903a, a plurality of LEDs 903a, and a plurality of LEDs 903a. The LEDs 903a are disposed on one side of the light guide plate 901 so as to face the light- And the PCB 903b is mounted at a predetermined interval.

At this time, the plurality of LEDs 903a emit light having colors of red (R), green (G), and blue (B) toward the front of the light guide plate 901, ) Can be turned on at once to realize white light by color mixing.

On the other hand, using the LED 903a constituted by an LED chip (not shown) that emits all the colors of RGB, the white light can be realized in each LED 903a, or a white The LED 903a emitting light may be used.

A plurality of LEDs 903a emitting RGB light may be bundled into one cluster and a plurality of LEDs 903a mounted on the PCB 903b may be arranged in a line on the PCB 903b. It is also possible to arrange them in parallel or in a plurality of rows.

Here, a plurality of LEDs 903a arranged on a PCB 903b in a row or in a plurality of rows is referred to as an LED array.

The light guide plate 901 uniformly spreads the light incident from the LED 903a to a wide area of the light guide plate 901 while traveling through the light guide plate 901 by total reflection to provide a surface light source to the liquid crystal panel 200 .

The light guide plate 901 is made of a plastic material such as polymethylmethacrylate (PMMA) or polycarbonate (PC), which is an acrylic transparent resin, which is one of transparent materials capable of transmitting light, It is made in flat type.

Here, PMMA is an acrylic resin, and is excellent in transparency, weather resistance, and colorability.

The driving circuit unit D includes a timing control unit 300, a gate driving unit 400, a data driving unit 500, a gamma voltage supplying unit 600, a power generating unit 700, and a lamp driving unit 800 .

Here, the timing controller 300 receives a video data signal RGB, a vertical synchronization signal Vsync0, a horizontal synchronization signal Hsync, a clock signal CLK, and a data enable signal from an external system such as a TV system or a video card And receives a control signal TCS such as a signal DE. Although not shown, these signals may be input through the interface configured in the timing controller 300. [

The timing control unit 300 uses the input control signal TCS to control the gate control signal GCS for controlling the gate driving unit 400 and the data control signal DCS for controlling the data driving unit 500 . Further, it generates a lamp control signal (LCS) for controlling the lamp driver 800.

The gate control signal GCS includes a gate start pulse GSP, a gate shift clock GSC and a gate output enable signal GOE. The data control signal DCS includes a source start pulse (SSP), a source sampling clock (SSC), a source output enable (SOE) signal, a polarity signal (POL) . ≪ / RTI >

The gate shift clock GSP serves to inform the start line of the screen in one vertical direction and the gate shift clock GSC serves to inform the start line of the screen, (T) is turned on. In addition, the gate output enable signal GOE serves to control the output of the gate driver 400.

The source start pulse SSP serves to notify the start point of data in the horizontal direction, that is, the first pixel P, and the source sampling clock SSC latches the data based on the rising and falling edges. (not shown). In addition, the embedded signal SOE serving as a source output controls the output of the data driver 500 and the polarity signal POL is a polarity signal to drive the liquid crystal in the positive polarity or the negative polarity. .

In addition, the timing controller 300 receives the image data signals RGB from the external system, aligns them, and transmits the image data signals RGB to the data driver 500.

The gamma voltage supplier 600 divides the high voltage and the low voltage to generate a plurality of gamma voltages Vgamma and supplies the same to the data driver 500.

The data driver 500 supplies the data voltages to the plurality of data lines DL in response to the data control signal DCS and the video data signals RGB supplied from the timing controller 300. [ That is, the data voltage corresponding to the video data signal RGB is generated using the gamma voltage Vgamma, and the generated data voltage is output to the data line DL.

The gate driver 400 sequentially scans a plurality of gate lines GL in response to a gate control signal GCS supplied from the timing controller 300. [

For example, a plurality of gate lines GL are sequentially selected for each frame, and a gate voltage is output to the selected gate line GL. By the gate voltage, the thin film transistor T located on the corresponding row line is turned on. On the other hand, a turn-off voltage is supplied to the gate line GL until the scan of the next frame, and the thin film transistor T maintains the turn-off state.

The power generating unit 700 generates various driving voltages necessary for driving the liquid crystal display device 100. For example, the power supply voltage supplied to the timing controller 300, the data driver 500, the gate driver 400 and the ramp driver 800, the gate high voltage and the gate low voltage supplied to the gate driver 400 .

The lamp driving unit 800 drives the backlight 900, for example, by applying different currents to the LED array in units of strings, in response to the lamp control signal LCS supplied from the timing control unit 300. This will be described later in detail.

Hereinafter, a method of applying different currents in a string unit according to an embodiment of the present invention will be described in more detail with reference to FIGS. 5 to 7. FIG.

FIG. 5 is a view illustrating an RGB type package among the LEDs 903a, and FIG. 6 is an illustration showing an RGB array type LED array.

7 is a schematic view of an LED array and a liquid crystal panel 200 according to an embodiment of the present invention. 6 is a diagram showing a two-edge type backlight 900 in which the LED array LA is formed on both sides of the liquid crystal panel 200, for example.

Referring to FIG. 5, the LED 903a mixes light having respective intrinsic colors emitted from RGB chips to realize white light.

Green chip (GC) and blue chip (BC) having the same size or different sizes are arranged in a predetermined order in one LED 903a. In order to realize white light, LEDs 903a The white light is realized by adjusting the amount of light having each inherent color coming from the RGB chips (RC, GC, BC) in the driving circuit to a certain ratio through the driving circuit.

Here, the relative ratio of the amount of RGB light required for mixing white light with each light amount emitted from the RGB chips (RC, GC, BC) is R: G: B = 3: It requires a relatively large amount of light.

Therefore, a green chip (GC) having a high light quantity of green (G) is used to realize white light with the light quantity from the red chip (RC), green chip (GC) and blue chip (BC) .

Referring to FIG. 6, a plurality of LEDs 903a are arranged in a line to form an LED array LA.

Specifically, for example, an RGB type LED 903a is mounted on the PCB 903b for current application and heat emission and is used as a light source.

At this time, the LED array LA can be logically divided into a plurality of LEDs 903a to apply current. Specifically, for example, three LEDs 903a may be logically divided to apply current. At this time, a partial unit of the LED array LA divided by three LEDs 903a is referred to as a string (ST), for example.

By applying a current to the LED array LA in units of strings (ST), luminance is improved and sharp picture quality can be provided.

Hereinafter, referring to FIG. 7, a method of applying a current in a unit of a string ST according to an embodiment of the present invention will be described in detail.

As shown in Fig. 7, LED arrays LA are located on both sides of the liquid crystal panel 200. As shown in Fig.

As described above, in the LED array LA, a plurality of LEDs 903a are mounted on the PCB 903b, and current is applied by logically dividing the LEDs 903a in units of strings (ST).

Specifically, the lamp driving unit 800 drives the LED array LA by applying different currents in units of strings in response to the lamp control signal LCS supplied from the timing control unit 300.

The lamp driving unit 800 applies a higher current to the string ST corresponding to the corner of the liquid crystal panel 200 than the string ST among the strings ST for discriminating the LED array LA .

Concretely, for example, the first to fourth strings ST1 to ST4 corresponding to the four corner portions forming the liquid crystal panel 200 are supplied with a higher current than the other strings ST.

Specifically, the first to fourth strings ST1 to ST4 can be supplied with a current, for example, 10% to 15% higher than the current applied to the other string ST.

Accordingly, as the currents applied to the first through fourth strings ST1 through ST4 become higher, the LED 903a located in the first through fourth strings ST1 through ST4 can obtain a higher light amount .

Here, the portion of the string ST to which a higher current is applied may be variously set according to the characteristics of the liquid crystal panel 200. [

1, when the same current is applied to the string ST constituting the LED array LA, the corner portion of the liquid crystal panel 200 becomes darker than the other portions. A higher current is applied to the string ST portion.

Thus, as shown in Fig. 8, there is an effect that the darkness of the corner portion of the liquid crystal panel 200 is improved.

Further, since the darkness of the corner portion of the liquid crystal panel 200 is improved, a clearer liquid crystal panel 200 can be provided.

It is apparent to those skilled in the art that the LED array LA is formed on both sides of the liquid crystal panel 200 as an example of the present invention, and the LED array LA can be formed on one side and four sides of the liquid crystal panel 200.

In this case, when the same current is applied to the string ST constituting the LED array LA, a higher current is applied to the string ST corresponding to the portion of the liquid crystal panel 200 where darkness occurs. The higher current also applies a current 10% to 15% higher than the current applied to the other string ST.

The embodiment of the present invention described above is an example of the present invention, and variations are possible within the spirit of the present invention. Accordingly, the invention includes modifications of the invention within the scope of the appended claims and equivalents thereof.

100: liquid crystal display device 200: liquid crystal panel
900: Backlight 903: LED assembly
903a: LED 903b: PCB
LA: LED array ST: string

Claims (8)

A liquid crystal panel;
A plurality of optical sheets disposed under the liquid crystal panel;
A light guide plate disposed under the plurality of optical sheets;
A reflection plate disposed under the light guide plate;
An LED array which is disposed on at least one side of the light guide plate so as to face the light guide plate and supplies light to the liquid crystal panel, the LED array being divided into a plurality of strings arranged in a line;
And a lamp driver for applying a current to the string corresponding to a corner portion of the liquid crystal panel by 10% to 15% higher than a current applied to the other strings
Liquid crystal display device.
The method according to claim 1,
Wherein the plurality of LEDs constituting each of the plurality of strings includes red chips, green chips, and blue chips,
Wherein a relative ratio of the amounts of red chips, green chips, and blue chips is 3: 6: 1
Liquid crystal display device.
delete The method according to claim 1,
And the LED array is disposed on one side, both sides or four sides of the liquid crystal panel
Liquid crystal display device.
A light guide plate disposed under the plurality of optical sheets; a reflection plate disposed under the light guide plate; and a light guide plate disposed on at least one side of the light guide plate so as to face the light entrance surface of the light guide plate A method of driving a liquid crystal display device including a plurality of LEDs, each of which is divided into a plurality of strings arranged in a line, the plurality of LEDs supplying light to the liquid crystal panel,
And applying a current to the string corresponding to a corner portion of the liquid crystal panel by 10% to 15% higher than a current applied to the other strings
A method of driving a liquid crystal display device.
6. The method of claim 5,
Wherein the plurality of LEDs constituting each of the plurality of strings includes red chips, green chips, and blue chips,
Wherein a relative ratio of the amounts of red chips, green chips, and blue chips is 3: 6: 1
A method of driving a liquid crystal display device.
delete 6. The method of claim 5,
And the LED array is disposed on one side, both sides or four sides of the liquid crystal panel
A method of driving a liquid crystal display device.

Images