KR20070066044A - Liquid crystal display and driving method thereof - Google Patents

Abstract

An LCD device and a driving method thereof are provided to compensate for response speed of the liquid crystal by using white light to realize higher luminance. An LCD(Liquid Crystal Display) device includes a light source array(112) and a light source driver(108). The light source array includes plural light sources, which irradiate lights to a liquid crystal panel(110). The light source driver drives the light source array to turn on at least one of the light sources with different luminance from a pixel data signal during one of plural sub-frames. The light source driver drives the light source array to realize white light with higher luminance than the luminance corresponding to the pixel data signal.

Description

Liquid crystal display and its driving method {LIQUID CRYSTAL DISPLAY AND DRIVING METHOD THEREOF}

1 is a view for explaining a field sequential driving method of a conventional liquid crystal display.

2 is a block diagram illustrating a liquid crystal display according to the present invention.

3A to 3C are diagrams illustrating driving signals applied to light sources driven in a field sequential driving method of a liquid crystal display according to the related art and the present invention.

4 is a view showing sequential driving of light sources during one frame period of the liquid crystal display according to the present invention.

5A and 5B are diagrams illustrating a driving signal applied to a white light source among light sources of the liquid crystal display according to the present invention and a light source driven in a subframe before the white light.

<Description of Symbols for Main Parts of Drawings>

102: data driver 104: gate driver

106: timing controller 108: light source driver

110: liquid crystal display panel 112: light source array

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

In general, a liquid crystal display (LCD) displays an image by adjusting light transmittance of liquid crystal cells according to a video signal. An active matrix liquid crystal display device in which switching elements are formed for each liquid crystal cell is suitable for displaying moving images. As a switching element used in an active matrix liquid crystal display device, a thin film transistor (hereinafter, referred to as TFT) is mainly used.

However, the liquid crystal display device has not only a slow response characteristic of the liquid crystal but also a motion blurring phenomenon in which the screen is blurred or a tailing phenomenon in which the contour appears to be drawn when the moving image is realized by the liquid crystal holding characteristic.

In order to reduce the image quality deterioration due to the retention characteristics of the liquid crystal display device, a field filter is used to sequentially remove three color light sources of a red light source, a green light source, and a blue light source located at the bottom of the bottom plate, by removing the color filter. The liquid crystal display of Fiel Sequential Driving System has been developed.

In the field sequential driving type liquid crystal display, as shown in FIG. 1, the red data is filled in the liquid crystal cell during the scanning time of the TFT, and then, after the response time of the liquid crystal, the red light source is turned on. The red color is displayed for a time less than the period After red is displayed, green and blue are displayed by writing green data and turning on the green light source, followed by writing blue data and turning on the blue light source.

That is, in a predetermined subframe (5.56 ms based on 16.7 ms) among the first to third subframes constituting the first frame, any one of red, green, and blue data is applied to the liquid crystal cell by using the gate pulse during the data write period. A voltage is supplied, and the data voltage of a specific color supplied to the liquid crystal cell is kept constant during the liquid crystal response period, and a specific color of light is transmitted through the liquid crystal cell to which the specific color data is supplied during the lamp lighting period. do.

However, the liquid crystal response time of the TN mode in the conventional field sequential liquid crystal display device is longer than one frame period. Therefore, when driving a liquid crystal display by dividing one frame into first to third subframe periods, the voltage charged in the liquid crystal cell proceeds to the next frame before the desired voltage is reached due to the slow response time of the liquid crystal in the TN mode. Therefore, there is a problem in that there is little effect of increasing the brightness. In addition, in order to obtain a brightness increase effect, there is a limit that is applied only to liquid crystals of OCB and FLC modes, in which the response time of the liquid crystal is relatively fast. In addition, the conventional field sequential driving type liquid crystal display has a problem that it is difficult to be applied to a resolution of VGA or higher because of the low mobility when the thin film transistor is made of amorphous silicon.

Accordingly, an object of the present invention is to provide a liquid crystal display device with increased luminance and a driving method thereof.

In order to achieve the above technical problem, the liquid crystal display device according to the present invention which displays an image by sequentially driving a light source by dividing a frame section into a plurality of sub frame sections, respectively emits a plurality of lights irradiated to the liquid crystal display panel. A light source array having a plurality of light sources; And a light source driver configured to drive the light source array so that at least one light source of the plurality of light sources is turned on at a brightness different from that corresponding to the pixel data signal in any one of the plurality of sub frame sections. It features.

The light source driving unit may drive the light source array to implement white light having a luminance higher than that corresponding to the pixel data signal.

To this end, the first embodiment of the light source array includes a red light source for generating red light, a green light source for generating green light, and a blue light source for generating blue light, wherein the red light, the green light source and the blue light source are simultaneously used. It is characterized in that the white to realize the light.

A second embodiment of the light source array may include a red light source for generating red light, a green light source for generating green light, a blue light source for generating blue light, and a white light source for generating white light.

And, the white light is characterized in that the common luminance portion of the red light source, the green light source and the blue light source.

In order to achieve the above technical problem, the driving method of the liquid crystal display according to the present invention comprises the steps of: dividing one frame period into a plurality of subframe periods, and a plurality of subframe periods in any one of the plurality of subframe periods; And driving the light source array such that at least one light source of the light source is turned on at a brightness different from that corresponding to the pixel data signal.

The driving of the light source array may include driving the light source array to implement white light having a luminance higher than that corresponding to the pixel data signal.

Other technical problems and features of the present invention in addition to the above technical problem will become apparent through the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 2 to 5B.

2 is a block diagram illustrating a liquid crystal display according to the present invention.

Referring to FIG. 2, a liquid crystal display according to the present invention includes a liquid crystal display panel 110 for implementing an image, a data driver 102 for driving a data line DL of the liquid crystal display panel 110, and a liquid crystal display. A gate driver 104 for driving the gate line GL of the display panel 110, a light source driver 108 for driving the light source array 112, a light source driver 108, a gate driver 104, A timing controller 106 for controlling the data driver 102 is provided.

The liquid crystal display panel 80 includes an insulated data line DL and a gate line GL, a thin film transistor TFT positioned at an intersection thereof, and a data line DL and a gate line GL. The liquid crystal cell Clc is formed to be connected to the thin film transistor TFT in the pixel region provided by the pixel region.

The timing controller 106 supplies the pixel data signals R, G, and B data input from the outside to the data driver 102. In addition, the timing controller 106 may include a gate control signal GDC and a data control signal for controlling each of the gate driver 104, the data driver 102, and the light source driver 108 in response to a control signal input from the outside. DDC) and a light source control signal (LDC).

The gate control signals GDC include a gate start pulse GSP, a gate shift clock signal GSC, a gate output enable signal GOE, and the like. The data control signals DDC include a source start pulse SSP, a source shift clock signal SSC, a source output enable signal SOE, a polarity control signal POL, and the like. The light source control signal LDC includes a signal for determining whether the red, green, and blue light sources of the light source array 70 are turned on and off.

The gate driver 104 sequentially supplies the gate high voltage VGH to the gate lines GL1 to GLn in response to the gate control signals GDC from the timing controller 106. Accordingly, the gate driver 104 causes the thin film transistor TFT connected to the gate lines GL1 to GLn to be driven in units of the gate line GL.

The data driver 102 generates pixel data signals of one horizontal line for each horizontal period H1, H2, ... in response to the data control signals DDC from the timing controller 106. DLm). In particular, the data driver 102 converts the digital pixel data R, G, and B from the timing controller 106 into an analog pixel data signal using a gamma voltage from a gamma voltage generator (not shown). do.

The data driver 102 time-divides the frame period in which one screen is displayed into the first to fourth subframes to supply data to the data line DL. That is, the data driver 102 supplies the red pixel data signal to the data line DL during the first subframe period. Thereafter, the green pixel data signal is supplied to the data line DL during the second sub frame period. Thereafter, the blue pixel data signal is supplied to the data line DL during the third sub frame period. Thereafter, the white pixel data signal is supplied to the data line DL during the fourth sub frame period. At this time, the supply period of the red, green, blue, and white pixel data signals supplied during each sub frame period may be variously changed according to the lighting sequence of the light source.

The light source driver 108 blinks the red, green, blue, and white light sources 112R, 112G, 112B, and 112W included in the light source array 112 in subframe units under the control of the timing controller 106. Here, the light source includes a cold cathode fluorescent lamp, a light emitting diode, and the like. The light source driver 108 maintains the light source while the remaining light sources are turned off for the first to fourth subframe periods in response to the light source control signal LDC.

3A to 3C are views for sequentially driving the light source array during one frame period in the liquid crystal display according to the related art and the present invention.

In the conventional liquid crystal display shown in FIG. 3A, the red (R), green (G), and blue (B) light sources are sequentially turned on during the first to third subframe periods 1SF to 3SF forming one frame period. In this case, the conventional liquid crystal display represents luminance corresponding to the current value I or voltage value applied to each of the red (R), green (G), and blue (B) light sources.

In the conventional liquid crystal display shown in FIG. 3B, the red (R), green (G), blue (B), and white (W) light sources are applied during the first to fourth subframe periods 1SF to 4SF forming one frame period. Lights up sequentially. To the white (W) light source, a red (R), green (G), and blue (B) light source shown in FIG. 3A is applied to a current value (I1) or a voltage value corresponding to the white luminance, which is commonly turned on. Implement the brightness of. In addition, a current value or a voltage value corresponding to the luminance of the remaining colors except for the white luminance is applied to the red, green, and blue light sources to implement the luminance of the corresponding color.

In this case, because the characteristics of the light source and the slow response speed of the liquid crystal, the amount of light emitted through the light source proceeds to the next frame before reaching the desired amount of light, and thus the conventional liquid crystal display cannot obtain the desired luminance.

In contrast, the liquid crystal display according to the present invention supplies the current value I2 higher than the original current value I1 to the white (W) light source as shown in FIG. 3C so that the luminance of the white W is higher than the original luminance. Implement Here, the white (W) light source of the liquid crystal display according to the present invention has a luminance equal to the white luminance that is realized by the red (R), green (G), and blue (B) light sources being commonly lit as shown in FIG. 3B. The red (R), green (G) and blue (B) light sources will be described with an example of implementing the luminance of the remaining colors except for the white (W) luminance.

Specifically, as shown in FIG. 4, the red light source 112R is turned on and the remaining light sources 112G, 112B, and 112W are turned off during the first sub frame period 1SF of one frame, so that red light is emitted from the liquid crystal display panel 110. Is incident on. Thereafter, the green light source 112G is turned on and the remaining light sources 112R, 112B, and 112W are turned off for the second sub frame period 2SF, and the green light is incident on the liquid crystal display panel 110. Thereafter, all the light sources are turned off during the third sub frame period 3SF. Thereafter, during the fourth frame period 4SF, the white light source 112W is turned on and the remaining light sources 112R, 112G, and 112B are turned off, and white light is incident on the liquid crystal display panel 110. At this time, the white light source 112W is supplied with a current value higher than the original current value to inject the white light having a light amount T2 higher than the original light amount T1 into the liquid crystal display panel 110. That is, the white light source 112W is supplied with a current value I2 capable of realizing a luminance higher than that corresponding to the white pixel data signal applied to the liquid crystal cell. For example, the white light source 112W has a current value that is greater than the current value I1 capable of realizing a luminance corresponding to the white pixel data signal applied to the liquid crystal cell Clc, and less than twice the current value I1. (I2) is supplied.

In addition, the current value applied to the white light source according to the present invention varies depending on the current value applied to the light source lit in the previous subframe of the subframe in which the white light source is turned on. This will be described with reference to FIGS. 5A and 5B.

 As shown in FIG. 5A, when the first blue current value IB1 is supplied to the blue light source that is lit in the previous subframe 3SF of the fourth subframe 4SF in which the white light source is turned on, the luminance of the white light source is increased. To this end, a second white current value IW2 higher than the first white current value IW1 is supplied.

On the other hand, as shown in FIG. 5B, the second blue current value lower than the first blue current value IB1 is applied to the blue light source lit in the previous subframe 3SF of the fourth subframe 4SF in which the white light source is turned on. When IB2) is supplied, the third white current value IW3 higher than the second white current value IW2 is supplied to the white light source.

This is because as the difference between the current value of the blue light source and the first white current value IW1 is smaller, the response speed of the light source can be reduced according to the current value, so that the desired luminance can be obtained even when a relatively small current value is supplied to the white light source. to be. The smaller the voltage difference between the blue pixel data signal supplied to the liquid crystal cell when the blue light source is turned on and the white pixel data signal supplied to the liquid crystal cell when the white light source is turned on, the smaller the response speed of the liquid crystal can be. This is because the desired luminance can be obtained even if the value is supplied.

On the other hand, the liquid crystal display according to the present invention has been described using a white light source to emit white light as an example, but may also generate white light using a red, green and blue light source without a white light source.

As described above, the liquid crystal display device and the driving method thereof according to the present invention use the white light to implement a luminance higher than the luminance corresponding to the white pixel data signal applied to the liquid crystal cell to improve the characteristics of the light source and the slow response speed of the liquid crystal. Compensation can be achieved to obtain desired luminance.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (10)

A liquid crystal display device which displays an image by sequentially driving a light source by dividing one frame section into a plurality of sub frame sections. A light source array having a plurality of light sources each emitting a plurality of lights irradiated onto the liquid crystal display panel; And a light source driver configured to drive the light source array so that at least one light source of the plurality of light sources is turned on at a brightness different from that corresponding to the pixel data signal in any one of the plurality of sub frame sections. A liquid crystal display device characterized by the above-mentioned. The method of claim 1, The light source driver And driving the light source array to implement white light having a luminance higher than that corresponding to the pixel data signal. The method of claim 2, The light source array includes a red light source generating red light, a green light source generating green light, and a blue light source generating blue light, The white light is a liquid crystal display, characterized in that the red light source, the green light source and the blue light source are simultaneously lit to implement the white. The method of claim 2, The light source array includes a red light source for generating red light, a green light source for generating green light, a blue light source for generating blue light, and a white light source for generating white light. The method of claim 2, And the white light implements a common luminance portion of the red light source, the green light source, and the blue light source. Dividing a frame section into a plurality of sub frame sections; Driving the light source array such that at least one light source of the plurality of light sources is turned on at a brightness different from a brightness corresponding to a corresponding pixel data signal in any one of the plurality of sub frame sections. A method of driving a liquid crystal display device. The method of claim 6, Driving the light source array And driving the light source array to implement white light having a luminance higher than that corresponding to the pixel data signal. The method of claim 7, wherein The white light is a driving method of the liquid crystal display, characterized in that the red light source, the green light source and the blue light source are simultaneously lit. The method of claim 7, wherein The white light is a driving method of the liquid crystal display device, characterized in that the white light source is turned on. The method of claim 7, wherein And the white light implements a common luminance portion of the red light source, the green light source, and the blue light source.

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