KR20080015598A - A display deivce and a method for driving the same - Google Patents

Abstract

A display device and a driving method thereof are provided to prevent a flickering phenomenon at a still image by sequentially turning on plural light sources or maintaining turn-on states of light sources according to a kind of images. A display device includes a display screen(201), plural light sources(LED), an image reader(231), and a light source driver(LD). The display screen displays an image. The light sources supply light to the display screen. The image reader compares previous image frame data with current image frame data and determines whether the image on a corresponding display screen is a moving picture or a still image. The light source driver maintains turn-on states of the light sources or sequentially turns on the light sources according to a comparison result from the image reader.

Description

A display deivce and a method for driving the same}

1 is a view showing a conventional liquid crystal display device having a direct type backlight.

2 illustrates a display device according to a first exemplary embodiment of the present invention.

3 illustrates a display device according to a second exemplary embodiment of the present invention.

4A is a diagram illustrating an image displayed on a display screen;

4B is a view illustrating a method of driving light sources according to the image of FIG. 4A;

* Explanation of symbols on the main parts of the drawings

200: liquid crystal panel 201: display screen

231: image reading unit LD: light source driving unit

LED: Light source LED_R: Red LED

LED_G: Green LED LED_B: Blue LED

The present invention relates to a display device, and more particularly, to a display device and a driving method thereof capable of improving image quality by controlling driving of light sources differently according to an image state.

In general, the liquid crystal display device (Liquid Crystal Display Device) is a trend that the application range is gradually widened due to the features such as light weight, thin, low power consumption. In accordance with this trend, liquid crystal displays have been used for office automation equipment, audio / video equipment, and the like.

Meanwhile, the liquid crystal display device displays a desired image on a screen by adjusting the amount of light transmitted according to image signals applied to a plurality of control switches arranged in a matrix form.

Since the liquid crystal display device is not a self-luminous display device, a light source such as a back light is required. Such a backlight for a liquid crystal display device includes a direct type method and a light guide plate method. The direct type places several lamps in the plane. A diffuser plate is installed between the lamp and the liquid crystal panel to maintain a constant space between the liquid crystal panel and the lamp. In the light guide plate method, a lamp is installed outside the flat plate, and light is incident from the lamp onto the entire surface of the liquid crystal panel using a transparent light guide plate.

Hereinafter, a liquid crystal display device having a conventional direct backlight is described with reference to the accompanying drawings.

1 is a view showing a conventional liquid crystal display device having a direct type backlight.

As shown in FIG. 1, a conventional LCD having a direct backlight includes a plurality of lamps 111 arranged in one direction and a liquid crystal panel 101 in which light emitted from the lamps 111 is provided. ).

Such a conventional liquid crystal display generates a uniform light by using a plurality of lamps 111 and irradiates the liquid crystal panel 101 to display a desired image. Accordingly, the conventional liquid crystal display device has a disadvantage in that power consumption is large because the lamp 111 needs to be continuously turned on.

Further, since the lamp 111 is continuously turned on regardless of whether the image displayed on the display screen of the liquid crystal panel 101 is a moving image or a still image, a motion blur phenomenon occurs in the moving image.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a display device and a driving method thereof which can improve image quality by controlling driving of light sources differently according to the state of an image.

A display device according to the present invention for achieving the above object, the display screen for displaying an image; A plurality of light sources for providing light to the display screen; An image reading unit which compares the image frame data of the previous period with the image frame data of the current period and determines whether the image on the display screen of the current period is a still image or a moving image; And a light source driver for keeping the light sources in a lighted state or lighting the light sources in sequence according to the determination result from the image reading unit.

In addition, a display device according to the present invention for achieving the above object, the display screen divided into a plurality of display areas; A plurality of light sources for providing light to the display screen; An image reading unit which compares the image frame data of the previous period and the image frame data of the current period, and determines a display area where a still image is displayed and a display area where a video is displayed on a screen of the current period; And a light source that maintains light sources positioned corresponding to the display area where the still image is displayed, and lights up light sources positioned corresponding to the display area where the video is displayed according to the determination result from the image reading unit. It is characterized by including a drive unit.

In the driving method of the display device according to the present invention for achieving the above object, in the driving method of the display device comprising a display screen for displaying an image, and a plurality of light sources for providing light to the display screen, Comparing the image frame data of the previous period with the image frame data of the current period to determine whether the image on the display screen of the current period is a still image or a moving image; And maintaining the light sources in a lighted state or lighting the light sources in sequence according to the determination result from the image reading unit.

In addition, the driving method of the display device according to the present invention for achieving the above object, the display device is divided into a plurality of display areas, and driving the display device including a plurality of light sources for providing light to the display screen A method comprising: comparing image frame data of a previous period with image frame data of a current period to determine a display area on which a still image is displayed and a display area on which a video is displayed on a screen of the current period; And keeping the light sources positioned in correspondence with the display area where the still image is displayed, and turning on the light sources located in correspondence with the display area where the video is displayed, in accordance with the determination result from the image reading unit. It characterized by including the.

Hereinafter, a liquid crystal display according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 is a diagram illustrating a display device according to a first embodiment of the present invention.

As shown in FIG. 2, the display device according to the first embodiment of the present invention provides a liquid crystal panel 200 having a display screen 201 for displaying an image, and provides light to the display screen 201. An image reading unit that compares a plurality of light sources (LEDs), image frame data of a previous period and image frame data of a current period, and determines whether the image on the display screen 201 of the current period is a still image or a moving image. 231 and a light source driver LD for maintaining the light sources LEDs in a lit state or turning on the light sources LEDs in sequence according to the determination result from the image reading unit 231.

The light source LED is a light emitting diode (LED), and the light sources LED emit red light (LED_R), green light emitting green LED (LED_G), and blue light emitting light. It includes a blue LED (LED_B).

These light sources LEDs are arranged in a matrix direction in a bottom cover (not shown). In this case, a plurality of light sources (LEDs) arranged along a horizontal line are commonly connected to one printed circuit board (PCB) substrate.

The inner bottom surface of the bottom cover is further formed with a reflector for increasing light efficiency.

The display screen 201 is formed on the display of the liquid crystal panel 200. The liquid crystal panel 200 includes an upper plate and a lower plate facing each other, and a liquid crystal layer disposed between the upper plate and the lower plate. The liquid crystal panel 200 includes a plurality of pixel areas defined by a plurality of gate lines and a plurality of data lines that cross each other. Each pixel region has a thin film transistor which is turned on according to a gate signal from the gate line and switches data (unit image data) from the data line, a pixel electrode supplied with data from the thin film transistor, The common electrode is disposed to face the pixel electrode. The light transmittance of the liquid crystal layer is changed according to an electric field generated between the pixel electrode and the common electrode, and a unit image according to the data is displayed in each pixel area.

The liquid crystal panel 200 is provided on the bottom cover where the light sources LEDs are formed.

Optical means is provided between the liquid crystal panel 200 and the bottom cover provided with the light sources LEDs. The optical means includes a diffusion plate provided on the bottom cover, and a prism sheet provided on the diffusion plate.

The diffusion plate allows the light emitted from the light sources (LEDs) to travel toward the display screen 201 of the liquid crystal panel 200, and controls the light to be incident at a wide range of angles.

The prism sheet can improve the front luminance of the display device by narrowing the viewing angle of the light emitted from the diffusion plate.

The image reading unit 231 compares the degree of change between the image displayed on the display screen 201 in the previous period and the image to be displayed on the display screen 201 in the current period. That is, the image reading unit 231 may be configured to provide the first image frame data which is the basis for the image displayed on the display screen 201 during the previous period, and the image to be displayed on the display screen 201 during the current period. The degree of change between the underlying second video frame data is compared.

To this end, the image reading unit 231 includes a line memory for receiving and storing image frame data of a previous period from a timing controller.

The entire image displayed on one screen of the liquid crystal panel 200 is an aggregate of each unit image displayed in each unit pixel region called a pixel included in the liquid crystal panel 200. Unit image data for representing a unit image in the pixel area is included.

Here, comparing the degree of change between the image frame data of the previous period and the image frame data of the current period is comparing the degree of change between the unit image data corresponding to each other.

The degree of change between each unit image data can be known by comparing the gradation value between each unit image data.

That is, the image reading unit 231 may include a gray value of each unit image data included in the image frame data of the previous period, and a gray value of each unit image data corresponding to each of the unit image data included in the image frame data of the current period. Compare The number of unit image data having different gradation values in the previous period and the current period and the number of unit image data having the same gradation values in the previous period and the current period are calculated.

By doing so, the number of pixel regions having different gradation values for each period and the number of pixel regions having the same gradation values for each period can be known on the display screen 201.

Thereafter, the image reading unit 231 compares the number of pixel areas having different gradation values for each period with a preset threshold.

When the number of pixel areas having different gradation values for each of the periods exceeds the threshold, the image reading unit 231 determines the image displayed on the display screen 201 as a moving image in the current period. Based on this determination, the image reading unit 231 outputs the first control signal CS1.

On the other hand, if the number of pixel areas having different gradation values for each of the periods is less than or equal to the threshold, the image reading unit 231 determines the image displayed on the display screen 201 as a moving image in the current period. Based on this determination, the image reading unit 231 outputs the second control signal CS2.

The first or second control signals CS1 and CS2 from the image reading unit 231 are supplied to the light source driver LD.

The light source driver LD sequentially turns on the first light sources LEDs in response to the first control signal CS1 (first method), and generates the light sources LEDs in response to the second control signal CS2. All of them are turned on at the same time and the lighting state is maintained (second method).

That is, when an image based on image frame data of the current period is displayed on the display screen 201 of the liquid crystal panel 200, the light source driving unit LD supplies the light sources LEDs in a first or second manner. Drive it.

The light sources LEDs are sequentially driven in units of horizontal lines by the first method. That is, first, the light sources LED arranged along the first horizontal line H1 are turned on at the same time, and then the light sources LED arranged along the second horizontal line H2 are turned on at the same time, and then the third horizontal line H The light sources LED arranged along H3) are simultaneously turned on, and finally, the light sources LED arranged along the ninth horizontal line H9 are simultaneously turned on. At this time, after the light sources LED are sequentially turned on from the first horizontal line H1 to the ninth horizontal line H9, the light sources LEDs of about 60% to about 70% of the horizontal lines are turned on and remain on. The light sources LED of the horizontal lines are turned off. For example, all of the light sources LED located in about six horizontal lines of the first to the ninth horizontal lines H1 to H9 remain on, and the other light sources are turned off.

The light sources LEDs may be driven in units of n horizontal lines (n is a natural number of 2 or more). That is, the light sources on the first and second horizontal lines H1 and H2 may be turned on at the same time, and then the light sources on the third and fourth horizontal lines H3 and H4 may be turned on at the same time.

By the second method, all of the light sources LEDs are all lit at the same time, and continue to maintain this lighting state until the next period. In addition, even if the image is a still image in the next period, the light sources LED are continuously turned on.

The light source driver LD may further include a pulse width modulation (PWM) controller. The PWM controller outputs a pulse signal having a duty ratio different according to the type of the control signal from the image reading unit 231, and supplies the same to the light sources LEDs to control the brightness of the light sources LEDs.

As described above, the liquid crystal display according to the present invention determines whether the image is a still image or a moving image, and drives the light sources LED in a first or second manner according to a result of the determination, thereby causing a motion blur in the moving image. Flickering in motion blur and still images can be minimized.

Next, the display device according to the second embodiment of the present invention will be described in detail.

3 is a diagram illustrating a display device according to a second exemplary embodiment of the present invention.

As shown in FIG. 3, the display device according to the second embodiment of the present invention includes a liquid crystal panel 300 having a display screen 301 divided into a plurality of display areas D1 to D12, and the display screen. A plurality of light sources (LEDs) that provide light to the 301 and the image frame data of the previous period and the image frame data of the current period are compared, so that the display area and the video where the still image is displayed on the display screen of the current period. The image reading unit 331 determining the display area to be displayed and the light sources LEDs corresponding to the display area where the still image is displayed according to the determination result of the image reading unit 331 are kept in the lit state. And a plurality of light source drivers LD1 to LD12 that sequentially light up the light sources LED positioned corresponding to the display area where the video is displayed.

As illustrated in FIG. 3, the display screen 301 includes first to twelfth display areas D1 to D12, and a plurality of light sources may be provided on the bottom cover portion corresponding to each of the display areas D1 to D12. LEDs) are provided.

The light sources LED located in each of the display areas D1 to D12 are independently driven by the light source drivers LD1 to LD12.

That is, turning on and turning off the light sources LED in the first display area D1 is controlled by the first light source driving unit LD1, and turning on and turning off the light sources LED in the second display area D2. The second light source driver LD2 is controlled by the second light source driver LD2, and the lighting and turning off of the light sources LED positioned in the twelfth display area D12 is controlled by the twelfth light source driver LD12.

As the display screen 301 is divided into a larger number of display areas, the number of the light source drivers increases.

The image reading unit 331 compares the image frame data of the previous period with the image frame data of the current period, and any of the display areas D1 to D12 of the current display screen 301 represents a moving picture. It is determined whether a display area is a part representing a still image. The first control signal CS1 is supplied to the light source controller for controlling the light sources LEDs of the display area representing the moving image, and the second control signal is supplied to the light source controller for controlling the light sources LEDs of the display area representing the still image. (CS2) is supplied.

Then, the light source driver supplied with the first control signal CS1 drives the light sources LEDs positioned in the display area in charge thereof in the above-described first manner. In addition, the light source driving unit supplied with the second control signal CS2 drives the light sources LEDs positioned in the display area in charge thereof in the above-described second manner.

4A is a diagram illustrating an image displayed on a display screen, and FIG. 4B is a diagram illustrating a method of driving light sources according to the image of FIG. 4A.

As shown in FIG. 4A, a video is displayed on the sixth and seventh display areas D6 to D7 of the display screen 301, and the remaining display areas (first to fifth display areas D1 to D5) are displayed. In the eighth to twelfth display areas D8 to D12, still images are displayed.

Therefore, as shown in FIG. 4B, the light sources LEDs positioned in the sixth and seventh display areas D6 to D7 are driven in the first manner, and the remaining display areas D1 to D5 and D8 to D12 are driven. The light sources LED located at are driven in a second manner.

That is, among the light sources LEDs positioned in the sixth and seventh display areas D6 and D7, the light sources LED arranged along the fourth horizontal line H4 are driven first, and then the fifth horizontal line H5. The light sources LED arranged along the line are driven, and finally the light sources LED arranged along the sixth horizontal line H6 are driven.

Therefore, the liquid crystal display according to the second exemplary embodiment of the present invention can minimize motion blur and flicker when the moving image and the still image are simultaneously displayed on the display screen 301.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and it is common in the art that 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.

As described above, the liquid crystal display device and the driving method thereof according to the present invention have the following effects.

The liquid crystal display according to the present invention compares the image frame data of the previous period with the image frame data of the current period, and determines whether the image on the display screen of the current period is a still image or a moving image, and determines from the image reading unit. As a result, the light sources are kept in the lit state or the light sources are turned on in sequence.

Therefore, it is possible to prevent the motion blur in the video and the flicker in the still image.

Claims (20)

A display screen for displaying an image; A plurality of light sources for providing light to the display screen; An image reading unit which compares the image frame data of the previous period with the image frame data of the current period and determines whether the image on the display screen of the current period is a still image or a moving image; And, And a light source driver for keeping the light sources in a lighted state or lighting the light sources in sequence according to the determination result from the image reading unit. The method of claim 1, The image reading unit, Compares the gradation value of each unit image data included in the image frame data of the previous period and the gradation value of each unit image data included in the image frame data of the current period, and determines whether the image on the display screen of the current period is still or A display device, characterized in that for determining the recognition. The method of claim 2, The display screen includes a plurality of pixel areas representing each unit image according to the unit image data. The image reading unit, The gray level value of each unit image data included in the image frame data of the previous period and the gray level value of each unit image data included in the image frame data of the current period are compared to determine whether the screen of the current period is still or moving image. Display device characterized in that. The method of claim 3, wherein The image reading unit, If the number of pixel areas having different gradation values in the previous period and the current period exceeds a predetermined threshold value, the image to be displayed on the display screen is determined as a moving picture; And, And determining that the image to be displayed on the display screen is a still image when the number of pixel regions having different gray scale values in the previous period and the current period is less than or equal to the threshold value. The method of claim 1, And a light source driving unit sequentially illuminating light sources positioned corresponding to an upper side of the display area to light sources positioned corresponding to a lower side when the image to be displayed on the display screen is a moving image. The method of claim 1, And the plurality of light sources are arranged in a matrix form. The method of claim 1, The light source is a display device, characterized in that the LED (Light Emitting Diode). A display screen divided into a plurality of display areas; A plurality of light sources for providing light to the display screen; An image reading unit which compares the image frame data of the previous period and the image frame data of the current period, and determines a display area where a still image is displayed and a display area where a video is displayed on a screen of the current period; And, According to a result of the determination from the image reading unit, a plurality of light sources that maintain light sources positioned corresponding to the display area where the still image is displayed, and light up the light sources located corresponding to the display area where the video is displayed And a driving unit. The method of claim 8, The image reading unit, A display area for displaying a still image on the screen of the current period by comparing the gray value of each unit image data included in the image frame data of the previous period and the gray value of each unit image data included in the image frame data of the current period; And a display area for displaying a moving image. The method of claim 9, Each display area includes a plurality of pixel areas representing each unit image according to the unit image data. The image reading unit has a difference between the number of pixel areas having different gray values in the previous period and the current period among the pixel areas in an arbitrary display area, and the number of pixel areas having the same gray value in the previous period and the current period. And determining whether the image represented in the arbitrary display area is a still image or a moving image. The method of claim 10, The image reading unit, If the number of pixel areas having different gradation values in the previous period and the current period exceeds a predetermined threshold value, the image to be displayed on the arbitrary display area is determined as a moving picture; And, And determining that the image to be displayed on the arbitrary display area is a still image when the number of pixel areas having different gradation values in the previous period and the current period is less than or equal to the threshold value. The method of claim 8, When the image to be displayed on the display area that is in charge of the video is a video, each light source driver sequentially turns on the light sources positioned in the display area from the light sources positioned corresponding to the upper side to the light sources positioned corresponding to the lower side. Display device characterized in that. A driving method of a display apparatus comprising a display screen for displaying an image and a plurality of light sources for providing light to the display screen, Comparing the image frame data of the previous period with the image frame data of the current period to determine whether the image on the display screen of the current period is a still image or a moving image; And And keeping the light sources in a lighted state or lighting the light sources in sequence according to the determination result from the image reading unit. The method of claim 13, In the determining of whether the image on the display screen of the current period is a still image or a video, Compares the gradation value of each unit image data included in the image frame data of the previous period and the gradation value of each unit image data included in the image frame data of the current period, and determines whether the image on the display screen of the current period is still or And a method of driving the display device. The method of claim 14, The display screen includes a plurality of pixel areas representing each unit image according to the unit image data. In the determining of whether the image on the display screen of the current period is a still image or a video, The gray level value of each unit image data included in the image frame data of the previous period and the gray level value of each unit image data included in the image frame data of the current period are compared to determine whether the screen of the current period is still or moving image. A driving method of a display device, characterized in that. The method of claim 15, In the determining of whether the image on the display screen of the current period is a still image or a video, If the number of pixel areas having different gradation values in the previous period and the current period exceeds a predetermined threshold value, the image to be displayed on the display screen is determined as a moving picture; And, And determining that the image to be displayed on the display screen is a still image when the number of pixel regions having different gradation values in the previous period and the current period is smaller than or equal to the threshold value. In the driving method of a display device comprising a display screen divided into a plurality of display areas, and a plurality of light sources for providing light to the display screen, Comparing the image frame data of the previous period with the image frame data of the current period, and determining a display area on which a still image is displayed and a display area on which a video is displayed on a screen of the current period; And, In response to the determination result from the image reading unit, maintaining the light sources positioned corresponding to the display area where the still image is displayed, and lighting the light sources positioned corresponding to the display area where the video is displayed. Method of driving a display device, characterized in that. The method of claim 17, In determining the display area where the still image is displayed on the screen of the current period and the display area where the video is displayed, the gray level value of each unit image data included in the image frame data of the previous period and the image frame data of the current period are included. And a display area on which a still image is displayed and a display area on which a video is displayed on the screen of the current period by comparing the gray level values of the respective unit image data. The method of claim 18, Each display area includes a plurality of pixel areas representing each unit image according to the unit image data. In the determining of the display area where the still image is displayed and the display area where the video is displayed on the screen of the current period, the number of pixel areas having different gradation values in the previous period and the current period among the pixel areas in the arbitrary display area. And comparing the difference between the number of pixel regions having the same gray level value in the previous period and the current period to determine whether the image represented in the arbitrary display region is a still image or a moving image. Driving method. The method of claim 19, In the determining of the display area where the still image is displayed and the display area where the video is displayed on the screen of the current period, when the number of pixel areas having different gray scale values in the previous period and the current period exceeds a predetermined threshold value. Determining an image to be displayed on the arbitrary display area as a moving picture; And, And when the number of pixel areas having different gradation values in the previous period and the current period is less than or equal to the threshold value, determining an image to be displayed on the arbitrary display area as a still image. .

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