KR20090073454A - Liquid crystal display device - Google Patents

Abstract

A liquid crystal display device is provided to reflect a gain value due to a color component of light for detecting brightness detected through light from a light emitting diode to each block brightness data, thereby uniformly maintaining a color coordinate of each block. A backlight unit(50) applies light generated in an LED(Light Emitting Diode) array(54) corresponding to each block to each block of a liquid crystal display panel. A light emitting diode for brightness detection installed at a backlight unit generates light for brightness detection. A backlight driver(60) drives the backlight unit through light for brightness detection and block brightness data detected through data signals supplied to each block.

Description

Liquid crystal display {LIQUID CRYSTAL DISPLAY DEVICE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device. In particular, a color coordinate of each block of a light emitting diode array divided into a plurality of blocks using a light emitting diode for luminance detection is constantly controlled, and a display image according to the brightness of each block is provided. The present invention relates to a liquid crystal display device capable of controlling partial luminance.

Typically, a liquid crystal display is backlit by a liquid crystal panel composed of a plurality of liquid crystal cells arranged in a matrix and a plurality of control switches for switching a video signal to be supplied to each of the liquid crystal cells. A transmission amount of light supplied from the unit (Back Light Unit) is adjusted to display a desired image on the screen.

The backlight unit is in the trend of miniaturization, thinning and weight reduction. In accordance with this trend, a backlight unit using a light emitting diode (Light Emitting Diode), which is advantageous in terms of power consumption, weight, and brightness, has been proposed instead of the fluorescent lamp used in the backlight unit.

A conventional backlight unit using a light emitting diode array emits light generated from a plurality of light emitting diodes installed on an inner bottom surface of a case to a liquid crystal panel. In addition, the LED array maintains a constant brightness at all times by feeding back a change in brightness of the LED array using a color sensor to control the brightness of the LED array.

However, the conventional backlight unit has a problem in that the partial luminance of the display image cannot be controlled because the luminance of the entire screen is adjusted by the color sensor according to the feedback signal.

In order to solve the above problems, the present invention is to control the color coordinates of each block of the light emitting diode array divided into a plurality of blocks by using the light emitting diode for brightness detection and to display the image according to the brightness of each block There is provided a liquid crystal display device capable of controlling a partial luminance of.

According to an aspect of the present invention, there is provided a liquid crystal display device including: a liquid crystal display panel having a liquid crystal cell formed for each region defined by a plurality of gate lines and a plurality of data lines; A data driving circuit converting an input data signal to a data voltage and supplying the data signal to the data lines; A gate driving circuit supplying scan pulses to the gate lines; A timing controller which controls the data driving circuit and the gate driving circuit and supplies the data signal to the data driving circuit; A backlight unit for dividing the liquid crystal display panel into a plurality of blocks and irradiating light generated from a light emitting diode array provided to correspond to each block to each block of the liquid crystal display panel; A luminance detecting light emitting diode provided in the backlight unit to generate luminance detecting light; And a backlight driver configured to drive the backlight unit by using the luminance data for each block detected through the data signals supplied to each block of the liquid crystal display panel and the luminance detection light. .

The liquid crystal display may further include a light guide for guiding the brightness detecting light to the backlight driver.

The backlight unit may include a case having a bottom surface and a side wall; A plurality of light emitting diode arrays disposed on a bottom surface of the case so as to correspond to the blocks; A diffusion member disposed on the front surface of the case so as to face the light emitting diode array; And at least one light collecting member disposed on the diffusion member, each of the plurality of light emitting diode arrays; Printed circuit board; And a plurality of light emitting diode packages arranged at regular intervals on the front surface of the printed circuit board.

The luminance detecting light emitting diode is provided on a rear surface of the printed circuit board to irradiate the light guide with the luminance detecting light.

The liquid crystal display according to the present invention maintains the color coordinates of each block by reflecting a gain value corresponding to the color component of the brightness detection light detected through the light from the brightness detection LED in the brightness data for each block. In addition, the partial brightness of the display image may be controlled through individual control of the LED array arranged to correspond to each block.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings and embodiments.

1 is a view schematically showing a liquid crystal display according to an exemplary embodiment of the present invention, and FIG. 2 is a cross-sectional view schematically showing a liquid crystal display according to an exemplary embodiment of the present invention.

1 and 2, a liquid crystal display according to an exemplary embodiment of the present invention may include a liquid crystal display panel 10; Timing controller 20; A data driving circuit 30; A gate driving circuit 40; Light Emitting Diode (hereinafter referred to as "LED") backlight unit 50; And an LED backlight driver 60.

The liquid crystal display panel 10 may include a thin film transistor (not shown) formed for each pixel area defined by the plurality of gate lines GL and the plurality of data lines DL, a liquid crystal capacitor (not shown) connected to the thin film transistor, And a storage capacitor (not shown).

The liquid crystal capacitor is composed of a pixel electrode connected to the thin film transistor and a common electrode facing the pixel electrode with the liquid crystal interposed therebetween. In this case, the pixel electrodes may be formed in a substantially cylindrical shape, or may be formed side by side at regular intervals to have at least one bent portion or bent portion, or a straight shape. The thin film transistor supplies a data voltage from each data line DL to the pixel electrode in response to a scan pulse from each gate line GL. The liquid crystal capacitor realizes a desired image by charging a difference voltage between the data voltage supplied to the pixel electrode and the common voltage supplied to the common electrode and adjusting the light transmittance of the liquid crystal according to the difference voltage.

The storage capacitor maintains the voltage charged in the liquid crystal capacitor until the next data voltage is supplied. The storage capacitor may be formed by overlapping the pixel electrode and the previous gate line, or may be formed by overlapping the pixel electrode and the storage line or overlapping the pixel electrode and the common electrode line.

The timing controller 20 aligns the input digital video data signal RGB to be suitable for driving the liquid crystal display panel 10 and arranges the aligned data signals R, G, and B in the data driving circuit 30 and the LED back. Supply to each of the light drive unit (60).

In addition, the timing controller 20 receives timing signals such as vertical / horizontal synchronization signals (Vsync, Hsync), data enable signals (Data Enable), clock signals (DCLK), and the like, and the data driving circuit 30 and the gate driving circuit. Generate timing control signals for controlling the operation timing of 40. These timing control signals include a gate control signal GCS such as a gate start pulse (GSP), a gate shift clock signal (GSC), a gate output enable signal (GOE), and the like. do. In addition, the timing control signals include a source start pulse (SSP), a source sampling clock (SSC), a source output enable signal (SOE), a polarity control signal (POL), and the like. Data control signal DCS.

The gate start pulse GSP is a timing signal indicating a first horizontal pulse at which a scan starts in one vertical period in which one screen is displayed, that is, a first scan pulse supplied to the first gate line. The gate shift clock signal GSC is input to a shift register in the gate driving circuit 40 and is a timing signal for sequentially shifting a gate start pulse GSP. The source start pulse SSP indicates a start pixel on one horizontal line in which data is to be displayed. The source sampling clock SSC instructs the latching operation of data in the data driving circuit 30 based on the rising or falling edge. The source output enable signal SOE indicates the output of the data driving circuit 30. The polarity control signal POL indicates the polarity of the data voltage to be supplied to the liquid crystal cells of the liquid crystal display panel 10.

The data driving circuit 30 latches the data signals R, G, and B input from the timing controller 20 under the control of the timing controller 20. The data driving circuit 30 converts the latched data R, G, and B into analog positive / negative gamma voltages according to the polarity control signal POL to generate positive / negative analog data voltages. The data voltage is supplied to the data lines DL.

The gate driving circuit 40 includes a plurality of gate drive integrated circuits including a shift register and a level shifter for converting an output signal of the shift register into a swing width suitable for driving the thin film transistor of the liquid crystal cell P. The gate driving circuit 40 sequentially supplies scan pulses to the gate lines GL in response to the gate control signal GCS. Here, the gate driving circuit 40 may further include an output buffer connected between the level shifter and the gate line GL. The gate driving circuit 40 may be formed on the substrate at the same time as the thin film transistor of the liquid crystal display panel 10 is formed.

LED backlight unit 50 includes a case 52; A plurality of LED arrays 54; Diffuser material 56; First and second light collecting members 58 and 59; Brightness detecting LED 70; And a light guide 76.

The case 52 includes a bottom surface on which the plurality of LED arrays 54 are installed and sidewalls bent from the bottom surface.

Reflecting members (not shown) may be formed on the bottom and sidewalls of the case 52. At this time, the reflection member reflects light from the plurality of LED arrays 54 toward the diffusion member 56, thereby preventing light loss and improving light efficiency. To this end, the reflective member may be formed of a plate or sheet made of polyethylene terephthalate (PET) or polycarbonate (PC), and may be coated with silver (Ag) or aluminum (Ag). .

Each of the plurality of LED arrays 54 is installed at regular intervals on the bottom surface of the case 10 to emit light by a driving current supplied from the LED backlight driver 60.

Each of the plurality of LED arrays 54 includes a printed circuit board 51 disposed on the bottom surface of the case 10 and a plurality of LED packages 53 disposed at regular intervals on the printed circuit board 51. It is configured by.

The printed circuit board 51 is a metal printed circuit board for dissipating heat generated in each LED package. Here, the metal printed circuit board is a base substrate of a metal material of aluminum or copper alloy; An insulating layer formed on the base substrate; A wiring layer formed on the insulating layer; And a wiring protective layer covering the wiring layer.

The plurality of LED packages 53 is configured in a form of a multi chip consisting of a red (R) LED, a green (G) LED, and a blue (B) LED. At this time, the red LED emits red light by emitting the red driving current supplied from the LED backlight driver 60 and the green LED emits green by the green driving current supplied from the LED backlight driver 60. Light is generated, and the blue LED emits light by the blue driving current supplied from the LED backlight driver 60 to generate blue light. Accordingly, each LED package 53 is a mixture of the red light, green light and blue light generated from the red (R) LED, green (G) LED and blue (B) LED by white balancing Emits white light.

The diffusion member 56 is disposed on the front surface of the case 52 to face the plurality of LED arrays 54. The diffusion member 56 diffuses the light from each of the LED arrays 54 to the entire region to improve light characteristics such as brightness and uniformity, and irradiate the first light collecting member 58.

The first light collecting member 58 may include a base film (not shown); And a first condensing pattern (not shown) formed on an upper surface of the base film. In this case, the first condensing pattern includes a first concave-convex pattern for increasing condensing or front luminance of light emitted from the diffusion member 56. For example, the request pattern may include a prism of a triangular cross section, a pyramid prism, a square pyramid, a triangular prism, a curved lens; And elliptical lenticular lenses formed regularly or irregularly.

The second light collecting member 59 may include a base film (not shown); And a second condensing pattern (not shown) formed on the upper surface of the base film. In this case, the second condensing pattern includes a second concave-convex pattern for increasing the front condensation or re-condensing of the light emitted from the first condensing member 58. Here, the second uneven pattern may be formed in a direction crossing the direction of the first uneven pattern according to the shape.

The luminance detecting LED 70 is disposed on the rear surface of any one of the plurality of LED arrays 54 and emits light by a constant driving current supplied from the LED backlight driver 60 to generate a luminance detecting light 74. Will occur).

The light guide 76 is inserted into the hole 55 formed in the bottom surface of the case 52 to surround the detection LED 70. The light guide 76 guides the brightness detecting light 74 generated by the brightness detecting LED 70 to the LED backlight driver 60.

As such, the LED backlight unit 50 is the LED package 53 of each LED array 54 by the red, green and blue driving current supplied from the LED backlight driver 60 to each LED array 54. The light is emitted to generate white light, and the optical properties such as brightness and uniformity of the white light are improved through the diffusion members 56 and the first and second light collecting members 58 and 59 to irradiate the liquid crystal display panel 10.

As shown in FIG. 1, the LED backlight driver 60 includes a block-by-block luminance controller 62; LED control unit 64; And first and second LED drivers 66 and 68.

The first LED driver 66 has a duty on period corresponding to each of the first to j (where j is i / 2) block dimming signals BDim_1 to BDim_j supplied from the LED controller 64. The first to j th driving currents are generated and supplied to the first to j th LED arrays 54. In this case, each of the first to j block dimming signals BDim_1 to BDim_j includes red, green, and blue dimming signals, which will be described later. In addition, each of the first to jth driving currents includes driving currents for red, green, and blue LEDs described later.

The second LED driver 68 includes the j + 1 to i th driving currents having a duty-on period corresponding to each of the j + 1 to i block dimming signals BDim_j + 1 to BDim_i supplied from the LED controller 64. Is generated and supplied to j-th to i-th LED array 54. In this case, each of the j + 1 to i block dimming signals BDim_j + 1 to BDim_i includes red, green, and blue dimming signals, which will be described later. In addition, each of the j + 1 to i-th driving currents includes driving currents for red, green, and blue LEDs described later.

Meanwhile, as shown in FIG. 2, the color sensor 72 is disposed in one of the first and second LED drivers 66 and 68, for example, the first driver 66.

The color sensor 72 is disposed in the first driver 66 to be inserted into the light guide 76 of the LED backlight unit 50. The color sensor 72 detects the red, green, and blue components Sr, Sg, and Sb of the luminance detecting light 74 irradiated from the luminance detecting LED 70 through the light guide 76 and the LEDs. It supplies to the control part 64.

The block-by-block luminance controller 62 divides the liquid crystal display panel 10 into i blocks (where i is a natural number), and divides the data signals R, G, and B supplied from the timing controller 20 to each block. Block data luminance data BLD_1 to BLD_i are detected. For example, the block brightness controller 62 may detect the maximum gray level value among the data signals to be supplied to each block as the block data brightness data BLD_1 to BLD_i. As another example, the block-by-block brightness controller 62 may detect the average gray value of the data signals to be supplied to each block as the block-by-block brightness data BLD_1 to BLD_i.

Meanwhile, the block-by-block luminance controller 62 may detect block-specific luminance data BLD_1 to BLD_i using luminance values of data signals to be supplied to each block.

To this end, the block-by-block luminance control unit 62, as shown in Figure 3, the gamma correction unit 110; A luminance extractor 120; And a block-by-block luminance data generator 130.

The gamma correction unit 110 gamma corrects the data signals R, G, and B from the timing controller 20 to generate linearized correction data Rc, Gc, and Bc as shown in Equation 1 below.

R1 = R ^λ

G1 = G ^λ

B1 = B ^λ

The luminance extractor 120 extracts the luminance component Y of the correction data Rc, Gc, and Bc supplied from the gamma correction unit 110. Herein, the luminance component Y may be extracted by Equation 2 below.

Y = 0.299 × R1 + 0.587 × G1 + 0.114 × B1

The block-by-block luminance data generation unit 130 generates the luminance component Y having the largest value among the luminance components Y of each block as the block-specific luminance data BLD_1 to BLD_i. As another example, the luminance data generator 130 for each block may generate the average luminance component Y of the luminance components Y of each block as luminance data BLD_1 to BLD_i for each block.

In FIG. 1, the LED control unit 64 includes red, green, and red blocks of the luminance data BLD_1 to BLD_i supplied from the block luminance controller 62 and the luminance detection light 74 supplied from the color sensor 70. The first to i block dimming signals BDim_1 to BDim_i are generated using the blue components Sr, Sg, and Sb. The LED controller 64 supplies the generated first to j block dimming signals BDim_1 to BDim_j to the first LED driver 66, and the j + 1 to i block dimming signals BDim_j + 1 to BDim_i. Is supplied to the second LED driver 68.

To this end, the LED control unit 64, as shown in Figure 4, the gain setting unit 210; And first to i-th block controllers 2201 to 220i.

The gain setting unit 210 has red, green, and blue gain values Gr, corresponding to each of the red, green, and blue components Sr, Sg, and Sb of the luminance detecting light 74 supplied from the color sensor 70. Gg and Gb) are generated and supplied to each of the first to i-th block controllers 2201 to 220i. Here, the gain values Gr, Gg, and Gb are set in the range of 0 to 1 in order to keep the color coordinates of the light generated by the LED backlight unit 50 constant.

Each of the first to i-th block controllers 2201 to 220i may include a comparator 310 as shown in FIG. 5; Switching unit 320; A red dimming signal generator 330; A green dimming signal generator 340; And a blue dimming signal generator 350.

The comparator 310 compares the reference data with the block-specific luminance data BLD and supplies a comparison signal CS corresponding to the comparison result to the switching unit 310. Here, since the error of the luminance control increases when the size of the block-specific luminance data BLD is small or when the red, green, and blue components Sr, Sg, and Sb are small, the reference data may be minimized. It is set to be. Accordingly, the reference data is preferably set to low gradation, for example 50 gradation.

Accordingly, the comparator 310 generates a comparison signal CS of the first logic state when the luminance data BLD of each block is 50 gradations or more, and generates a comparison signal CS of the second logic state if the block data is not less than 50 gray levels. do.

The switching unit 320 may include a red dimming signal generator 330 corresponding to each of the red, green, and blue gain values Gr, Gg, and Gb according to the comparison signal CS supplied from the comparator 310; A green dimming signal generator 340; And a blue dimming signal generator 350. In this case, when the comparison signal CS is in the first logic state, the switching unit 320 supplies gain values Gr, Gg, and Gb to the dimming signal generators 330, 340, and 350, and compares the signal CS. In the second logic state, the gain values Gr, Gg, and Gb are not supplied to the dimming signal generators 330, 340, and 350.

When the red gain value Gr supplied from the switching unit 320 is supplied, the red dimming signal generator 330 multiplies the red gain value Gr and the luminance data BLD for each block to perform a red dimming signal BDim_R. If the red gain value Gr is not supplied from the switching unit 320, the block-specific luminance data BLD is generated as a red dimming signal BDim_R.

When the green gain value Gg supplied from the switching unit 320 is supplied, the green dimming signal generator 340 multiplies the green gain value Gg and the luminance data BLD for each block to calculate the green dimming signal BDim_G. In the case where the green gain value Gg is not supplied from the switching unit 320, the block-specific luminance data BLD is generated as the green dimming signal BDim_G.

When the blue gain value Gb supplied from the switching unit 320 is supplied, the red dimming signal generator 330 multiplies the blue gain value Gb and the luminance data BLD for each block to perform a blue dimming signal BDim_B. ), And when the blue gain value Gb is not supplied from the switching unit 320, the block-specific luminance data BLD is generated as a blue dimming signal BDim_B.

Each of the first to i-th block controllers 2201 to 220i stores the red, green, and blue gain values Gr, Gg, and Gb only when the luminance data BLD of each block is greater than or equal to the reference data. A red dimming signal BDim_R by multiplying by BLD; Green dimming signal BDim_G; And a block dimming signal BDim_k including the blue dimming signal BDim_B, wherein k is a natural number of 1 to i, and corresponding to the generated block dimming signal BDim_k. , 68).

As described above, the liquid crystal display according to the exemplary embodiment of the present invention has green and blue gain values Gr and Gg corresponding to the red, green, and blue components Sr, Sg, and Sb detected through the luminance detecting LED 70. , Gb), multiply the luminance data BLD of each block by the green and blue gain values Gr, Gg, and Gb to generate a block dimming signal BDim for each block, and generate the block dimming signal. A driving current having a duty on period corresponding to BDim is generated to emit light of each LED package 53 disposed in each LED array 54.

Accordingly, the liquid crystal display according to the exemplary embodiment of the present invention reflects a gain value corresponding to the color component of the luminance detecting light detected through the light from the luminance detecting light emitting diode 70 in the luminance data for each block, so that In addition to keeping the color coordinates constant, partial luminance of the display image may be controlled through individual control of the LED array 54 disposed to correspond to each block.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes can be made without departing from the technical spirit of the present invention. It will be evident to those who have knowledge of.

1 is a schematic view of a liquid crystal display according to an exemplary embodiment of the present invention;

2 is a cross-sectional view schematically showing the light emitting diode backlight unit shown in FIG. 1;

3 is a block diagram showing a block-by-block luminance control unit shown in FIG. 1;

4 is a block diagram showing a light emitting diode controller shown in FIG. 1; And

FIG. 5 is a block diagram illustrating each block controller shown in FIG. 4.

<Explanation of Signs of Major Parts of Drawings>

10 liquid crystal display panel 20 timing control unit

30: data driving circuit 40: gate driving circuit

50: LED backlight unit 54: LED array

60: LED backlight drive unit 62: block luminance control unit

64: LED controller 66: first LED driver

68: second LED driver 70: luminance detection LED

72: color sensor 74: brightness detection light

Claims (14)

A liquid crystal display panel having a liquid crystal cell formed for each region defined by a plurality of gate lines and a plurality of data lines; A data driving circuit converting an input data signal to a data voltage and supplying the data signal to the data lines; A gate driving circuit supplying scan pulses to the gate lines; A timing controller which controls the data driving circuit and the gate driving circuit and supplies the data signal to the data driving circuit; A backlight unit for dividing the liquid crystal display panel into a plurality of blocks and irradiating light generated from a light emitting diode array provided to correspond to each block to each block of the liquid crystal display panel; A luminance detecting light emitting diode provided in the backlight unit to generate luminance detecting light; And And a backlight driver configured to drive the backlight unit by using the luminance data for each block detected through the data signals supplied to each block of the liquid crystal display panel and the luminance detection light. Display. The method of claim 1, And a light guide for guiding the brightness detecting light to the backlight driver. The method of claim 2, The backlight unit is; A case having a bottom surface and sidewalls; A plurality of light emitting diode arrays disposed on a bottom surface of the case so as to correspond to the blocks; A diffusion member disposed on the front surface of the case so as to face the light emitting diode array; And At least one light collecting member disposed on the diffusion member, Each of the plurality of light emitting diode arrays; Printed circuit board; And And a plurality of light emitting diode packages arranged at regular intervals on the front surface of the printed circuit board. The method of claim 3, wherein And the luminance detecting light emitting diode is provided on a rear surface of the printed circuit board to irradiate the light guide with the luminance detecting light. The method of claim 4, wherein And the light guide is inserted into a hole formed in the bottom surface of the case to surround the light emitting diode for luminance detection. The method of claim 3, wherein The backlight drive unit; A block-by-block luminance controller detecting the luminance data of each block by using the data signals supplied to each block of the liquid crystal display panel; A sensor for detecting a color component of the brightness detecting light emitted through the light guide; A light emitting diode controller configured to generate a dimming signal for each block by using the color component of the light and the luminance data for each block; And And a light emitting diode driver installed with the sensor and generating a driving current for each block according to the dimming signal for each block, and supplying the driving current to each of the light emitting diode arrays. The method of claim 6, And the brightness control unit for each block generates the brightness data for each block by using gray level values or brightness values of data signals supplied to the blocks. The method of claim 7, wherein The luminance data for each block is a maximum gray value or an average gray value among data signals supplied to each block. The method of claim 7, wherein The block-by-block luminance control unit; A gamma correction unit to gamma correct the data signal to generate correction data; A luminance extracting unit which extracts a luminance value from the correction data; And And a block-by-block luminance data generator configured to generate the block-by-block luminance data by using the extracted luminance values of the respective blocks. The method of claim 9, And the luminance data for each block is the largest luminance value or an average luminance value among luminance values of data signals supplied to each block. The method of claim 9, The light emitting diode control unit; A gain setting unit for setting a gain value according to a color component of light supplied from the sensor; And And a plurality of block controllers which generate the dimming signal for each block by using the gain value and the luminance data for each block. The method of claim 11, Each of the plurality of block controllers includes; A comparator for comparing a reference data with the luminance data for each block to generate a comparison signal; A switching unit for switching the gain value according to the comparison signal; And And a dimming signal generator for generating the dimming signal for each block by multiplying the gain value supplied according to the switching of the switching unit and the luminance data for each block, or for generating the dimming signal for each block using only the luminance data for each block. Liquid crystal display characterized in that the configuration. The method of claim 12, Wherein each of the light emitting packages comprises red, green, and blue light emitting diodes. The method of claim 13, The block-specific dimming signals include block-specific red, green, and blue dimming signals for controlling the red, green, and blue light emitting diodes, respectively; The dimming signal generator; A red dimming signal generating unit generating the dimming signal for each block by multiplying the gain value and the luminance data for each block, or generating the red dimming signal for each block using only the luminance data for each block; A green dimming signal generating unit generating the dimming signal for each block by multiplying the gain value and the luminance data for each block or the green dimming signal for each block using only the luminance data for each block; And And a blue dimming signal generator for generating the dimming signal for each block by multiplying the gain value and the luminance data for each block, or for generating the blue dimming signal for each block using only the luminance data for each block. Liquid crystal display.

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