KR20070075009A - Display device and method of driving the same - Google Patents

Abstract

A display device and a method of driving the same are provided to enhance image quality by driving the display device through an HDR(High Dynamic Range) scheme. A display device includes a timing controller(110), a light source driver(170), a light source(180), a data driver(140), and a display panel(160). The timing controller converts a primary gradation signal to a high gradation signal using the primary gradation signal and generates first and second gradation signals based on the high gradation signal. The light source driver outputs a driving signal in response to the first gradation signal. The light source generates a light based on the driving signal. The data driver converts the second gradation signal to an analog gradation voltage and outputs the converted analog gradation voltage. The display panel displays images in response to the analog gradation voltage.

Description

DISPLAY DEVICE AND METHOD OF DRIVING THE SAME}

1 is a block diagram of a display device according to an exemplary embodiment of the present invention.

FIG. 2 is a schematic perspective view illustrating driving of the liquid crystal display panel and the light source unit illustrated in FIG. 1.

3 is a detailed block diagram of the timing controller shown in FIG. 1.

FIG. 4 is conversion curves for describing an operation of the high gray scale conversion unit illustrated in FIG. 3.

5A and 5B are flowcharts illustrating a method of driving a display device according to another exemplary embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

110: timing controller 140: data driver

160: liquid crystal display panel 170: light source driver

180: light source unit 112: data input unit

113: first storage unit 114: high gradation conversion unit

115: second storage unit 116: average gray calculator

117: first grayscale conversion unit 118: second grayscale conversion unit

The present invention relates to a display device and a driving method thereof, and more particularly, to a display device for improving image quality and a driving method thereof.

In general, a liquid crystal display device includes a liquid crystal display panel for displaying an image and a light source unit for providing light to the liquid crystal display panel. The liquid crystal display panel includes two opposing substrates in which a plurality of pixel portions are defined, and a liquid crystal layer interposed between the two substrates. The light source unit is disposed on a front surface of the liquid crystal display panel to provide front light, and a rear light source unit disposed on a rear surface of the liquid crystal display panel to provide white light (hereinafter, referred to as a backlight unit). Divided by.

Generally, a fluorescent lamp (eg, CCFL, EEFL) and a light emitting diode (LED) are used as a light source of the backlight unit. When the light emitting diode is used, a plurality of light emitting diodes are arranged on the rear surface of the liquid crystal display panel to provide back light to the liquid crystal display panel.

The backlight unit always generates light while being driven by the liquid crystal display panel. That is, even when a complete black image is displayed on the liquid crystal display panel, the backlight unit provides light to the liquid crystal display panel. As described above, according to the dual driving method of the liquid crystal display panel and the backlight unit, there is a problem of deterioration in image quality that an unwanted image is seen in the human eye. Preferably, the sharpness of the image seen by the human eye is displayed brighter for bright images and darker for dark images.

Accordingly, the technical problem of the present invention was conceived in this respect, and an object of the present invention is to provide a display device for improving image quality.

Another object of the present invention is to provide a method of driving the display device.

A display device according to an exemplary embodiment for realizing the object of the present invention includes a timing controller, a light source driver, a light source, a data driver, and a display panel. The timing controller converts the raw gradation signal into a 2 k-bit high gradation signal using k-bit raw gradation signals in frame units, and calculates a k-bit first gradation signal and a second gradation signal based on the high gradation signal. do. The light source driver outputs a driving signal in response to the first gray level signal. The light source unit generates light having a predetermined luminance by the driving signal. The data driver converts the second gray level signal into an analog gray level voltage and outputs the analog gray level voltage. The display panel displays an image in response to the gray voltage.

According to another aspect of the present invention, there is provided a data driver for outputting a gray voltage to a display panel for displaying an image, and a light source driver for outputting a driving signal to a light source for generating light on the display panel. In the driving method of the display device, the raw gradation signal is converted into a high gradation signal of 2 k bits using the k-bit raw gradation signals in a frame unit, and the average gradation signal for the high gradation signals in a predetermined unit is calculated. The average gradation signal is converted into the k-bit first gradation signal, and output to the light source driver. The second gradation signal of the k-bit is calculated using the high gradation signal and output to the data driver.

According to such a display device and a driving method thereof, an image can be expressed in more detail by converting a k-bit raw gradation signal into a 2k-bit high gradation signal adaptively to the brightness of the frame screen.

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

1 is a block diagram of a display device according to an exemplary embodiment of the present invention.

Referring to FIG. 1, the display device includes a timing controller 110, a driving voltage generator 120, a reference gamma voltage generator 130, a data driver 140, a gate driver 150, and a liquid crystal display panel 160. , A light source driving unit 170 and a light source unit 180.

The timing controller 110 receives a source control signal 101a and a source grayscale signal 101b of k (k is a natural number) bits from an external device. The timing controller 110 converts the k-bit raw gradation signal 101b into a 2k-bit high gradation signal using a conversion curve adaptive to the brightness of the frame screen. The timing controller 110 converts the 2k-bit gradation signal into k-bit first gradation signal 110d and second gradation signal 110e, respectively. The k-bit first gray level signal 110d is provided to the light source driver 170, and the k-bit second gray level signal 110e is provided to the data driver 140. That is, the first gray level signal 110d is a luminance signal that controls the brightness of the light source unit 180, and the second gray level signal 110e is a data signal for driving the liquid crystal display panel 160.

The timing controller 110 generates and outputs control signals for driving the display device based on the original control signal 101a. In detail, the control signals control the first control signal 110a for controlling the driving voltage generator 120, the second control signal 110b for controlling the data driver 140, and the gate driver 150. The third control signal 110c and the fourth control signal 110d for controlling the light source driver 170 are included. The fourth control signal 110d includes the first gray level signal.

The driving voltage generator 120 generates driving voltages for driving the display device. In detail, the driving voltage generator 120 outputs an analog driving voltage 120b to the reference gamma voltage generator 130, and outputs gate voltages 120c to the gate driver 150. The common voltage 120d is output to the liquid crystal display panel 160.

The reference gamma voltage generator 130 generates 10 to 20 reference gamma voltages 130a by using the analog driving voltage 120b and outputs the same to the data driver 140.

The data driver 140 converts the k-bit second gray level signal 110e provided from the timing controller 110 into a gray level voltage and outputs the gray level voltage. In detail, the data driver 140 converts the second gray level signal 110e into a gray level voltage by using the second control signal 110b and the reference gamma voltages 130a to the liquid crystal display panel 160. Output

The gate driver 150 generates gate signals using the third control signal 110c provided from the timing controller 110 and the gate voltages 120c provided from the driving voltage generator 120. The gate signals are output to the liquid crystal display panel 160.

The liquid crystal display panel 160 includes a plurality of pixel portions P defined by a plurality of gate lines GL and a plurality of source lines DL, and each pixel portion P includes a switching element ( And a liquid crystal capacitor CLC and a storage capacitor CST connected to the TFT and the switching element TFT. A common voltage 120d provided from the driving voltage generator 120 is applied to one end of each of the liquid crystal capacitor CLC and the storage capacitor CST.

The light source driver 170 drives the light source unit 180 based on the k-bit first gray level signal 110d provided from the timing controller 110. The light source driver 170 pulse width modulates the first gray level signal 110d and applies the pulse width modulated drive signal 170a to the light source unit 180.

The light source unit 180 includes a plurality of light emitting diodes (LEDs), and the light emitting diodes are driven by being divided into the plurality of light source blocks. The timing controller 110 provides the first gray level signal 110d corresponding to each light source block to the light source driver 170, and the light source driver 170 pulses the first gray level signal 110d. The width modulation is applied to a corresponding light source block among the plurality of light source blocks.

FIG. 2 is a schematic perspective view illustrating driving of the liquid crystal display panel and the light source unit illustrated in FIG. 1.

1 and 2, the liquid crystal display panel 160 is formed of M × N pixel parts by M data lines and N gate lines, and displays a screen 260 of one frame. . Here, M and N are natural numbers.

The one frame screen 260 is composed of, for example, six screen blocks B1, B2, B3, B4, B5, and B6. That is, one screen block B1 is composed of m × n pixel parts, thereby being driven by m × n gray level signals. Where m < M and n < N.

The light source unit 180 includes a plurality of light emitting diodes 181. The light source unit 180 includes six light source blocks LB1, LB2, LB3, LB4, LB5, and LB6 corresponding to the six screen blocks B1, B2, B3, B4, B5, and B6. Accordingly, the light source driver 170 modulates the pulse width to drive the light source blocks LB1, LB2, LB3, LB4, LB5, and LB6 according to the first gray level signal 110d provided from the timing controller 110. The driving signals 170a-1, 170a-2, 170a-3, 170a-4, 170a-5, and 170a-6, which are the power signals, are output.

3 is a detailed block diagram of the timing controller shown in FIG. 1. FIG. 4 is conversion curves for describing an operation of the high gray scale conversion unit illustrated in FIG. 3.

2 to 4, the timing controller 110 includes a control signal generator 111, a data input unit 112, a first storage unit 113, a high gray scale conversion unit 114, and a second storage unit. 115, an average gray calculator 116, a first gray converter 117, and a second gray converter 118.

The control signal generator 111 generates and outputs first, second and third control signals 110a, 110b, and 110c for driving the display device based on the raw control signal 101a input from the outside. . The original control signal 101a includes a main clock signal MCLK, a horizontal synchronization signal HSYNC, a vertical synchronization signal VSYNC, and a data enable signal DE.

The data input unit 112 receives a raw gradation signal 101b provided from an external device, that is, a k-bit original gradation signal Di.

The input raw gradation signal is stored in a frame unit in the first storage unit 113.

The high gradation converter 114 converts the k-bit raw gradation signal Di into a 2k-bit high gradation signal HDi using a conversion curve adaptive to the brightness of the frame screen.

Specifically, an average brightness signal AL of the raw gradation signals in the frame unit is calculated. The calculated average brightness signal AL classifies the brightness level of the frame screen based on a predetermined threshold range. For example, when the raw gradation signal is 8 bits, when the calculated average brightness signal exists in the first threshold range (0 to 85), it is a dark screen, and when it is in the second threshold range (86 to 176), a normal screen And, if present in the third threshold range (171 to 255) it is divided into a bright screen.

After dividing the brightness level of the frame screen based on the average brightness signal AL as described above, a k-bit raw gradation signal Di is converted into a 2 k-bit high gradation signal (by applying a conversion curve corresponding to the threshold range). HDi).

For example, as shown in FIG. 4, the high gradation converter 114 includes a first conversion curve C1, a second conversion curve C2, and a third corresponding to the first to third threshold ranges, respectively. The transformation curve C3 is stored in the form of a transformation lookup table or a transformation function.

The first conversion curve C1 is a conversion curve applied when the brightness of the frame screen is dark. When the 8-bit gradation signal in the low gradation range (0 to 171) is converted into a 16-bit gradation signal, It is a curve for displaying a dark screen in detail by distributing it to an area. The second conversion curve C2 is a conversion curve applied when the brightness of the frame screen is a normal screen, and is a curve for linearly converting an 8-bit raw gray level signal into a 16-bit high level signal. On the other hand, the third conversion curve C3 is a conversion curve applied when the brightness of the frame screen is bright, and when the 8-bit gradation signal in the high gradation range 172 to 255 is converted into a 16-bit gradation signal. It is a curve for displaying a bright screen in more detail by distributing it in a wide area.

In the above, an example of dividing the brightness of the frame screen into three levels is taken as an example.

The second storage unit 115 stores the high gray level signal HDi output from the high gray level converter 114 in a predetermined unit. Preferably, the high gradation signals corresponding to n horizontal lines among the high gradation signals of one frame displayed on the liquid crystal display panel 160 are stored. For example, high gradation signals corresponding to the first screen block and the second screen blocks B1 and B2 are stored.

The average gradation calculator 116 calculates an average gradation signal AD for the high gradation signals corresponding to the m × n pixel units among the high gradation signals stored in the second storage 115. Specifically, the average gray level signal AD is calculated and output corresponding to each of the screen blocks B1, B2, B3, B4, B5, and B6. Each average gray level signal AD is a 2k bit gray level signal.

The first grayscale converter 117 converts the 2k bit average gray signal AD into a k bit average gray signal, that is, the first gray signal 110d. The k-bit first gray level signal 110d is provided to the light source driver 170. The light source driver 170 may pulse-modulate the first gray level signal 110d to output a corresponding light source block among the plurality of light source blocks LB1, LB2, LB3, LB4, LB5, and LB6.

The second gray level converter 118 converts the high gray level signal HDi of 2k bits read from the second storage unit 115 into a second gray level signal 110e of k bits. Preferably, the second gray level converter 118 calculates the second gray level signal 110e by dividing the high gray level signal HDi of 2k bits by the first gray level signal 110d of k bits. The second gray level signal 110e is provided to the data driver 140.

For example, a second gray level signal corresponding to the first screen block B1 may be divided by dividing the high gray level signals of the first screen block B1 into first gray level signals corresponding to the first light source block LB1. Calculate them. The calculated second gray level signals are provided to the data driver 140, and the data driver 140 converts the second gray level signals into analog gray voltages and outputs the analog gray voltages to the liquid crystal display panel 160. 1 The image is displayed on the screen block B1. In this case, the first light source block LB1 emits light having brightness corresponding to the first gray level signal.

Accordingly, the first screen block B1 displays a relatively high resolution image, and the first light source block LB1 displays a relatively low resolution image. That is, after converting the k-bit gradation signal into a 2k-bit high gradation signal, the 2k-bit high gradation signal is converted into a k-bit first gradation signal and a k-bit second gradation signal, respectively, to drive the display device. Let's do it.

Accordingly, the display device may display a dark screen and a bright screen in more detail as the display device is driven by a high dynamic range (HDR).

5A and 5B are flowcharts illustrating a method of driving a display device according to another exemplary embodiment of the present invention.

2 to 5B, the data input unit 112 receives a raw gradation signal 101b provided from an external device, for example, an 8-bit original gradation signal Di (S110). The received raw gray level signal Di is stored in the first storage unit 113 in units of frames. The high gradation converter 114 first calculates an average brightness signal AL of the raw gradation signal in units of frames stored in the first storage unit 113 (S120).

The high gray scale conversion unit 114 determines the degree of brightness of the frame screen based on the average brightness signal AL. In detail, it is determined whether the average brightness signal AL exists within the first threshold range 0 to 85 which is the low gradation range (S130). When the average brightness signal AL is within the first threshold range, the high gray scale conversion unit 114 applies the pre-stored first conversion curve C1 to convert the raw gray level signal into a 16-bit high gray level signal HDi. (S132).

On the other hand, if the average brightness signal AL does not exist within the first threshold range, it is determined whether the average brightness signal AL exists within the second threshold range 86 to 170 which is the halftone range (S140). When the average brightness signal AL is within the second threshold range, the high gray scale conversion unit 114 applies the pre-stored second conversion curve C2 to convert the raw gray level signal into a 16-bit high gray level signal HDi. (S142).

Meanwhile, when the average brightness signal AL does not exist within the second threshold range, it is determined whether the average brightness signal AL exists within the third threshold range 171 to 255 which is the high gradation range (S150). When the average brightness signal AL is within the third threshold range, the high gray scale conversion unit 114 applies the pre-stored third conversion curve C3 to convert the raw gray level signal into a 16-bit high gray level signal HDi. (S152). As described above, the high gray level signal HDi output from the high gray level conversion unit 114 is stored in the second storage unit 115.

The average gradation calculator 115 calculates an average gradation signal AD for a predetermined unit stored in the storage 114, that is, high gradation signals for each screen block (S160). Specifically, an average gray level signal is calculated for each of the screen blocks B1, B2, B3, B4, B5, and B6.

The first gray level converter 116 converts the 2k bit average gray signal AD into a first gray level signal 110d, which is a k bit average gray signal, and the second gray level converter 117 The 2k bit high gray level signal read from the storage unit 114 is converted into a k bit second gray level signal 110e (S170). Preferably, the second gray level converter 117 calculates the second gray level signal 110e by dividing the high gray level signal HDi of 2k bits by the first gray level signal 110d of k bits.

Thereafter, the k-bit first gray level signal 110d is provided to the light source driver 170 to drive the light source unit 180, and the k-bit second gray level signal 110e is transmitted to the data driver 140. It is provided to drive the liquid crystal display panel 160 (S180).

Accordingly, by converting the raw gradation signal into a high gradation signal adaptively to the brightness of the frame screen, a clearer and more detailed image can be displayed on both a dark screen and a bright screen.

As described above, according to the present invention, the k-bit raw gradation signal is converted into a 2k-bit high gradation signal by adaptively adapting the brightness level of the frame screen to drive the display device in the HDR method, so that both a dark screen and a bright screen can be operated. Detailed image representation can be enabled. Therefore, the image quality of the image displayed on the display device can be further improved.

Although described above with reference to the embodiments, those skilled in the art can be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below. I can understand.

Claims (11)

A timing controller converting the raw gradation signal into a 2 k-bit high gradation signal using k-bit raw gradation signals in frame units and calculating a k-bit first gradation signal and a second gradation signal based on the high gradation signal; A light source driver configured to output a driving signal in response to the first gray level signal; A light source unit generating light having a predetermined luminance by the driving signal; A data driver converting the second gray level signal into an analog gray level voltage and outputting the analog gray level voltage; And And a display panel displaying an image in response to the gray voltage. The method of claim 1, wherein the timing controller A high gradation converter configured to obtain an average brightness signal by adding the raw gradation signals in the frame unit and convert the raw gradation signal into a high gradation signal based on the average brightness signal; An average gradation calculator for calculating an average gradation signal for the high gradation signals in a predetermined unit; A first gradation converter converting the average gradation signal into a k-bit first gradation signal and outputting it to the light source driver; And And a second gray level converter which calculates the k-bit second gray level signal using the high gray level signal and outputs the second gray level signal to the data driver. The display device of claim 2, wherein the high gray scale conversion unit converts the raw gray level signal into a high gray level signal using a conversion curve corresponding to the average brightness signal among a plurality of preset conversion curves. The method of claim 3, wherein the plurality of conversion curves include a first conversion curve corresponding to a low gradation range, a second conversion curve corresponding to a mid gradation range, and a third conversion curve corresponding to a high gradation range. Display device. The display device of claim 2, wherein the predetermined unit is smaller than the frame unit. The display device as claimed in claim 5, wherein the second gray level converter divides the high gray level signals of the predetermined unit into the first gray level signals to calculate the second gray level signals. In a driving method of a display device comprising a data driver for outputting a gray voltage to a display panel for displaying an image and a light source driver for outputting a drive signal to a light source for generating light on the display panel, Converting the raw gradation signal into a high gradation signal of 2 k bits using k-bit raw gradation signals in frame units; Calculating an average gradation signal for the high gradation signals in a predetermined unit; Converting the average gradation signal into the k-bit first gradation signal and outputting it to the light source driver; And And calculating the k-bit second gray level signal using the high gray level signal and outputting the k-bit second gray level signal to the data driver. The method of claim 7, wherein converting the high gray signal of 2k bits Calculating an average brightness signal by adding the raw gradation signals in the frame unit; And And converting the raw gradation signal into a high gradation signal using a conversion curve corresponding to the average brightness signal among a plurality of preset conversion curves. The method of claim 8, wherein the plurality of conversion curves include a first conversion curve corresponding to a low gradation range, a second conversion curve corresponding to a mid gradation range, and a third conversion curve corresponding to a high gradation range. A driving method of the display device. The method of claim 7, wherein the predetermined unit is smaller than the frame unit. The driving method of claim 10, wherein the second gray level signal is calculated by dividing a high gray level signal of a predetermined unit by the first gray level signal, respectively.

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