Liquid crystal display device and driving method thereof

Abstract

A liquid crystal display device includes a display panel including one or more pixel region partitioned into first, second and third sub-pixels; a backlight including first and second sources for projecting onto the one or more pixel region one of a first light having a first wavelength and a second light having a second wavelength; and a controller for partitioning a four-color pixel data corresponding to a period into first and second data to be applied to the first and second sub-pixels, respectively, during a first part of the period while the backlight projects the first light onto the one or more pixel region, and third and fourth data to be applied to the first and second sub-pixels, respectively, during a second part of the period while the backlight projects the second light onto the one or more pixel region, the controller applying a white data to the third sub-pixel during the first and second parts of the period.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of embodiments of the present invention and are incorporated in and constitute a part of this application, illustrate embodiments of the present invention and together with the description serve to explain the principle of embodiments of the present invention. In the drawings:

FIG. 1 is an equivalent circuit diagram showing a pixel provided at a related art LCD;

FIG. 2 is a block diagram showing a configuration of the related art LCD;

FIG. 3 is a block diagram showing a configuration of an LCD according to an embodiment of the present invention;

FIG. 4A shows a circuit diagram of exemplary sub-pixel regions in the LCD device of FIG. 3;

FIG. 4B shows a cross-sectional view of exemplary sub-pixel regions with colors and transparent filters according to an embodiment of the invention;

FIG. 4C shows a cross-sectional view of exemplary sub-pixel regions with colors and transparent filters according to another embodiment of the invention;

FIG. 4D shows a diagram of the interrelationship between R, G and B primary colors and C, Y and M colors;

FIG. 4E is a waveform diagram showing a driving waveform of the LCD according to the embodiment of the present invention;

FIG. 5 is a block diagram showing a configuration of a data processor in FIG. 3;

FIG. 6A to FIG. 6D are exemplary views explaining an operation of the data processor in FIG. 3 according to an embodiment of the invention; and

FIG. 7A to FIG. 7B are exemplary views explaining an operation of the data processor in FIG. 3 according to another embodiment of the invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

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

FIG. 3 is a block diagram showing a configuration of an LCD device according to an embodiment of the present invention. Referring to FIG. 3, an LCD device 200 includes a gate driver 130, a gamma reference voltage generator 140, an inverter 160, a common voltage generator 170, and a gate driving voltage generator 180 similar to the LCD device 100 shown in FIG. 1. The LCD device 200 further includes an LCD panel 210, a data processor 220, a timing controller 230, a data driver 240, and a backlight assembly 250. The LCD panel 110 has an upper glass substrate (not shown) and a lower glass substrate (not shown) facing each other, and a liquid crystal material is formed between the upper glass substrate and the lower glass substrate.

FIG. 4A shows a circuit diagram of exemplary sub-pixel regions in the LCD device of FIG. 3. Referring to FIG. 4A, data lines DL1 to DLm and gate lines GL1 to GLn cross each other on the lower glass substrate. Crossings of the data lines DL1 to DLm and the gate lines GL1 to GLn define pixel regions. Each pixel region is partitioned into a G sub-pixel, a W sub-pixel, and an M sub-pixel by forming G, W, and M color filters formed on the LCD panel 210. A TFT is formed at each of the G sub-pixel, the W sub-pixel, and the M sub-pixel, and the TFT supplies a data on the data lines DL1 to DLm to the liquid crystal cell Clc in response to a scanning pulse from the gate driver 130.

FIG. 4B shows a cross-sectional view of exemplary sub-pixel regions with colors and transparent filters according to an embodiment of the invention. FIG. 4C shows a cross-sectional view of exemplary sub-pixel regions with colors and transparent filters according to another embodiment of the invention. Referring to FIGS. 4B and 4C, the W sub-pixel is a transparent sub-pixel. As shown in FIG. 4B, color filters G and M are formed at corresponding sub-pixels of the color filter substrate with a black matrix BM separating the subpixels from each other. The W sub-pixel region does not include a filter. Similarly, as shown in FIG. 4C, color filters G and M are formed at corresponding sub-pixels of the color filter substrate with a black matrix BM separating the subpixels from each other. In contrast, in FIG. 4C, the W sub-pixel includes a transparent filter without any pigment in it with the common electrode (not shown) on the pigment-less transparent filter.

The data processor 220 converts three-color RGB data from a system into four-color RGCB data, and then calculates a gain from the four-color RGCB data. The data processor 220 amplifies a gray level of the four-color RGCB data in proportion to the calculated gain, and then calculates a minimum gray level of the amplified four-color RGCB data. The data processor 220 calculates an RGCB data using the calculated gain and the minimum gray level, and at the same time generates a W data having the calculated minimum gray level in each of the color components to output a digital RGCBW data to the timing controller 230.

FIG. 4D shows a diagram of the interrelationship between R, G and B primary colors and C, Y and M colors. Referring to FIG. 4D, the wavelengths of light corresponding to C fall between G and B. The wavelengths of light corresponding to M falls between R and B. The wavelength of light corresponding to Y falls between R and G. Thus, a C light passing through a G filter will emerge as a C light. In contrast, the C light passing through an M filter emerges as a B light. A Y light passing through a G filter emerges as a G light. In contrast, a Y light passing through an M filter emerges as a R light.

The timing controller 230 supplies the digital RGCBW data to the data driver 240, and at the same time generates a data driving control signal DDC and a gate driving control signal GDC using horizontal/vertical synchronizing signals H and V from a system in accordance with a clock signal CLK inputted from a system to supply them to the data driver 240 and the gate driver 130, respectively. Herein, the data driving control signal DDC includes a source shift clock SSC, a source start pulse SSP, a polarity control signal POL, and a source output enable signal SOE, etc., and the gate driving control signal GDC includes a gate start pulse GSP, a gate shift clock GSC, and a gate output enable signal GOE, etc.

The data driver 240 converts a digital RGCBW data inputted via the timing controller 230 into an analog RGCBW data in accordance with the timing controller 230 to supply it to the LCD panel 210 as follows. Each input frame is divided into first and second subframes to be sequentially displayed on the LCD panel. Accordingly, if the input frames are driven at a frequency of about 60 Hz, for example, the corresponding first and second subframes are driven at a frequency of about 120 Hz.

FIG. 4E is a waveform diagram showing a driving waveform of the LCD device according to an embodiment of the present invention. As shown in FIG. 4E, during the first subframe period, each pixel is irradiated with a C light from the backlight (not shown). If data from the first subframe is inputted from the timing controller 230, the data driver 240 supplies an analog C data and an analog B data to the G sub-pixel and the M sub-pixel, respectively, and supplies an analog W data to the W sub-pixel. Thus, during the first subframe period, the G sub-pixel transmits a light of C wavelength and the M sub-pixel transmits a light of B wavelength. Furthermore, the W sub-pixel transmits the C light from the backlight source substantially unchanged to increase a light transmittance.

During the second subframe period, each pixel is irradiated with a Y light from the backlight (not shown). If data from the second subframe is inputted from the timing controller 230, the data driver 240 supplies an analog G data and an analog R data to a G sub-pixel and an M sub-pixel, respectively, and supplies an analog W data to a W sub-pixel. During the second subframe period, the G sub-pixel transmits a light of G wavelength and the M sub-pixel transmits a light of R wavelength. Furthermore, the W sub-pixel transmits the Y light from the backlight source substantially unchanged to increase a light transmittance.

The backlight assembly 250 is radiated by a driving voltage and a current supplied from the inverter 160 to sequentially irradiate a C light and a Y light into the LCD panel 210 as follows. When driving the first subframe, a G sub-pixel and an M sub-pixel are supplied with an analog C data and an analog B data, respectively, and a W sub-pixel is supplied with an analog W data. Then, the backlight assembly 250 turns on a C light source to irradiates the C light onto the LCD panel 210. When driving the second subframe, a G sub-pixel and an M sub-pixel are supplied with an analog G data and an analog R data, respectively, and a W sub-pixel is supplied with an analog W data. Then, the backlight assembly 250 turns on a Y light source to irradiates the Y light into the LCD panel 210.

FIG. 5 is a block diagram showing a configuration of the data processor in FIG. 3. Referring to FIG. 5, the data processor 220 includes a data converter 221, a gain calculator 222, a data amplifier 223, a gray level calculator 224, and a data calculator 225.

FIG. 6A to FIG. 6D are exemplary views explaining an operation of the data processor in FIG. 3 according to an embodiment of the invention. Referring to FIG. 6A, the data converter 221 converts a three-color Ri, Gi, and Bi data from a system into a four-color RGCB data to output them to the gain calculator 222.

The gain calculator 222 calculates a maximum gray level GV1max and a minimum gray level GV1min of four-color RGCB data converted by the data converter 221, and then substitutes the maximum gray level GV1max and the minimum gray level GV1min in the following equation 1 to calculate a gain, thereby outputting it to the data amplifier 223.

Gain=(GV1max+GV1min)/GV1max  [Equation 1]

As described above, the gain calculator 222 divides a value that the calculated maximum gray level GV1max and the minimum gray level GV1min are added, by the maximum gray level GV1max to calculate the share as a gain.

The data amplifier 223 multiplies a gray level of RGCB data by the calculated gain to amplify a gray level of RGCB data. In other words, the data amplifier 223 amplifies a gray level of RGCB data in proportion to the calculated gain as shown in FIG. 6B.

Referring to FIG. 6C, the gray level calculator 224 calculates a minimum gray level GV2min of four-color RGCB data amplified by the data amplifier 223 to output it to the data calculator 225. As shown in FIG. 6C, the amplified RGCB data can be interpreted as a combination of a first RGCB data (top portion of FIG. 6C) having a zero gray level value in the color component corresponding to the minimum gray level value (for example, the G component), and a second RGCB data (the boxed component at the bottom of FIG. 6C) with all four components having a gray level equal to the minimum gray level value GV2min. Accordingly, the second RGCB data corresponds to a W data having a gray level value of GV2min, as shown in FIG. 6D.

The data calculator 225 subtracts a minimum gray level GV2min calculated by the gray level calculator 224 from a gray level of RGCB data amplified by the data amplifier 223 to calculate a Ro, Go, Co, and Bo data to be outputted to the data output terminal, and generates a Wo data having a minimum gray level GV2min to output it to the data output terminal. More specifically, the data calculator 225 carries out a predetermined equation 2 to equation 5 to calculate an output Ro, Go, Co, and Bo data as shown in FIG. 6D. Furthermore, the data calculator 225 generates a Wo data having a minimum gray level GV2min calculated as shown in FIG. 6D.

Ro=(gain*R)−GV2min  [Equation 2]

As described above, the data calculator 225 subtracts a minimum gray level GV2min calculated by the gray level calculator 224 from a gray level of a R data amplified by the data amplifier 223 to calculate a Ro data.

Go=(gain*G)−GV2min  [Equation 3]

As described above, the data calculator 225 subtracts a minimum gray level GV2min calculated by the gray level calculator 224 from a gray level of a G data amplified by the data amplifier 223 to calculate a Go data.

Co=(gain*C)−GV2min  [Equation 4]

As described above, the data calculator 225 subtracts a minimum gray level GV2min calculated by the gray level calculator 224 from a gray level of a C data amplified by the data amplifier 223 to calculate a Co data.

Bo=(gain*B)−GV2min  [Equation 5]

As described above, the data calculator 225 subtracts a minimum gray level GV2min calculated by the gray level calculator 224 from a gray level of a B data amplified by the data amplifier 223 to calculate a Bo data.

Furthermore, there is a functional relation between a Wo data generated by the data calculator 225, and a maximum gray level GV2max and a minimum gray level GV2min of gray levels of RGCB data amplified by the data amplifier 223 as shown in the following equation 6.

Wo=f(GV2max,GV2min)  [Equation 6]

Herein, “f” represents a function having a maximum gray level GV2max and a minimum gray level GV2min as a variable.

FIG. 7A to FIG. 7B are exemplary views explaining an operation of the data processor in FIG. 3 according to another embodiment of the invention.

Referring to FIG. 7A, the gray level calculator 224 calculates a minimum gray level GV2min of four-color RGCB data amplified by the data amplifier 223 to output it to the data calculator 225. As shown in FIG. 7A, the amplified RGCB data can be interpreted as a combination of a first RGCB data (top portion of FIG. 7A) having a non-zero gray level value in the color component corresponding to the minimum gray level value (for example, the G component), and a second RGCB data (the boxed component at the bottom of FIG. 7A) with all four components having a gray level value GV2white less than the minimum gray level value GV2min. Accordingly, the second RGCB data corresponds to a W data having a gray level value of GV2white, as shown in FIG. 7B.

The data calculator 225 subtracts a white gray level GV2white calculated by the gray level calculator 224 from a gray level of RGCB data amplified by the data amplifier 223 to calculate a Ro, Go, Co, and Bo data to be outputted to the data output terminal, and generates a Wo data having the white gray level GV2white to output it to the data output terminal. Furthermore, the data calculator 225 generates a Wo data having the gray level GV2white calculated as shown in FIG. 7B.

Ro=(gain*R)−GV2white  [Equation 7]

As described above, the data calculator 225 subtracts the white gray level GV2white calculated by the gray level calculator 224 from a gray level of a R data amplified by the data amplifier 223 to calculate a Ro data in accordance with Equation 7.

Go=(gain*G)−GV2white  [Equation 8]

As described above, the data calculator 225 subtracts the white gray level GV2white calculated by the gray level calculator 224 from a gray level of a G data amplified by the data amplifier 223 to calculate a Go data in accordance with Equation 8.

Co=(gain*C)−GV2white  [Equation 9]

As described above, the data calculator 225 subtracts the white gray level GV2white calculated by the gray level calculator 224 from a gray level of a C data amplified by the data amplifier 223 to calculate a Co data in accordance with Equation 9.

Bo=(gain*B)−GV2white  [Equation 10]

As described above, the data calculator 225 subtracts the white gray level GV2white calculated by the gray level calculator 224 from a gray level of a B data amplified by the data amplifier 223 to calculate a Bo data in accordance with Equation 10.

As described above, the present invention calculates a W data through the above-mentioned process to increase a light transmittance, and calculate a white data without distorting an R color, a G color, a C color, and a B color.

It will be apparent to those skilled in the art that various modifications and variations can be made in the liquid crystal display device and method of driving the same of embodiments of the present invention. Thus, it is intended that embodiments of the present invention cover the modifications and variations of the embodiments described herein provided they come within the scope of the appended claims and their equivalents.

Claims

1. A liquid crystal display device, comprising: a converter for converting a three-color pixel data into a converted data;an amplifier for amplifying the converted data; anda first calculator for generating a four-color pixel data having a zero gray level value in one of the four colors corresponding to a minimum gray level of the four colors, and a white data having a gray level value equal to the minimum gray level in each of the four colors.

2. The liquid crystal display device of claim 1, further comprising a processor for converting the three-color pixel data into the four-color pixel data and the white data.

3. The liquid crystal display device of claim 1, further comprising a second calculator for calculating a gain in accordance with a maximum gray level and the minimum gray level of the four colors.

4. The liquid crystal display device of claim 3, wherein the gain is a fraction of the summation of the maximum and minimum gray levels.

5. The liquid crystal display device of claim 1, wherein each of the first, second, third and fourth data is generated from the amplified converted data by subtracting the minimum gray level from each of the four colors of the amplified converted data.

6. The liquid crystal device of claim 1, further comprising a controller for partitioning the four-color pixel data into first and second data to be applied to the first and second sub-pixels of a display panel, respectively, during a first part of a display period, and third and fourth data to be applied to the first and second sub-pixels, respectively, during a second part of the display period, the controller applying the white data to a third sub-pixel of the display panel during the first and second parts of the display period.

7. The liquid crystal device of claim 6, further comprising a backlight including first and second sources for projecting a first light having a first wavelength onto the first and second sub-pixels during the first part of the display period and a second light having a second wavelength onto the first and second sub-pixels during the second part of the display period.

8. The liquid crystal display device of claim 7, wherein the first light includes cyan light and the second light includes yellow light.

9. The liquid crystal display device of claim 6, wherein the first, second, third and fourth data include cyan, blue, green and red data, respectively.

10. The liquid crystal display device of claim 1, further comprising a display panel including one or more pixel partitioned into first, second and third sub-pixels.

11. The liquid crystal display device of claim 10, wherein the first, second and third sub-pixels include green, magenta and transparent filters, respectively.

12. The liquid crystal device of claim 10, further comprising a controller for partitioning the four-color pixel data into first and second data to be applied to the first and second sub-pixels, respectively, during a first part of a display period, and third and fourth data to be applied to the first and second sub-pixels, respectively, during a second part of the display period, the controller applying the white data to the third sub-pixel during the first and second parts of the display period.

13. A method of driving a liquid crystal display device including a display panel with one or more pixel region partitioned into first, second and third sub-pixels, the method comprising: converting an input three-color pixel data into a converted data;amplifying the converted data;generating a four-color pixel data by subtracting from the amplified data a minimum gray level of the four colors;generating a white data having a gray level value less than or equal to the minimum gray level in each of the four colors; anddisplaying the four-color pixel data and the white data on the display panel.

14. The method of claim 13, wherein the displaying of the four-color pixel data includes: partitioning the four-color pixel data into first, second, third and fourth data;applying the first and second data to the first and second sub-pixels, respectively, and the white data to the third sub-pixel during a first part of a display period; andapplying the third and fourth data to the first and second sub-pixels, respectively, and the white data to the third sub-pixel during a second part of the display period.

15. The method of claim 14, further comprising projecting a first light having a first wavelength onto the first, second and third sub-pixels during the first part of the display period and a second light having a second wavelength onto the first, second and third sub-pixels during the second part of the display period.

16. The method of claim 13, wherein the four-color pixel data has a zero gray level value in one of the four colors corresponding to the minimum gray level of the four colors.

17. A liquid crystal display device, comprising: a converter for converting a three-color pixel data into a converted data;an amplifier for amplifying the converted data; anda calculator for generating a four-color pixel data, and a white data having a gray level value less than or equal to a minimum gray level of the four colors in each of the four colors.

18. The liquid crystal display device of claim 17, further comprising a controller for partitioning the four-color pixel data into first and second data to be applied to the first and second sub-pixels of a display panel, respectively, during a first part of a display period, and third and fourth data to be applied to the first and second sub-pixels, respectively, during a second part of the display period, the controller applying the white data to a third sub-pixel of the display panel during the first and second parts of the display period.

19. The liquid crystal display device of claim 18, further comprising a backlight including first and second sources for projecting a first light having a first wavelength onto the first, second and third sub-pixels during the first part of the display period and a second light having a second wavelength onto the first, second and third sub-pixels during the second part of the display period.

20. The liquid crystal display device of claim 17, wherein the each of the first, second, third and fourth data is generated from the amplified converted data by subtracting the minimum gray level from each of the four colors of the amplified converted data.