Patent Publication Number: US-8988469-B2

Title: Image display device and driving method thereof

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of the Korean Patent Application No. 10-2009-0135082 filed on Dec. 31, 2009, which is hereby incorporated by reference as if fully set forth herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image display device, and more particularly, to an image display device which facilitates to improve partial luminance in an image-display area by a local dimming method to partially control a backlight unit according to a display image, and simultaneously to reduce power consumption, and a driving method thereof. 
     2. Discussion of the Related Art 
     Generally, a liquid crystal display (LCD) device includes a liquid crystal display panel and a backlight unit, wherein the liquid crystal display panel is provided with plural liquid crystal cells arranged in a matrix-type configuration, and plural control switches for conversion of image data to be supplied to the plural liquid crystal cells. In this case, a transmittance of light emitted from the backlight unit is controlled in the liquid crystal display panel, whereby a desired image is displayed on a screen. 
     A related art backlight unit may be largely classified into a direct type and an edge type. In the direct type backlight unit, a light source is positioned at a rear side of a liquid crystal display panel, whereby the liquid crystal display panel is directly illuminated with light emitted from the light source. In the edge type backlight unit, a light source is positioned at one lateral side or both lateral sides of a liquid crystal display panel, whereby the liquid crystal display panel is illuminated with light emitted from the light source through the use of light-guiding plate. Especially, the direct type backlight unit can realize high luminance since the liquid crystal display panel is directly illuminated with light emitted from plural lamps, whereby the direct type backlight unit is chiefly used for a large-sized liquid crystal display device. 
     The related art backlight unit applies light with constant luminance to the liquid crystal display panel without regard to an image displayed on the liquid crystal display panel. Accordingly, since the constant luminance is maintained in the backlight unit without regard to the image displayed on the liquid crystal display panel, it is difficult to animatedly express an image with parts requiring high luminance, for example, explosion scene or flashlight scene. In addition, the continuous provision of the constant luminance causes the increase of power consumption. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to an image display device and a driving method thereof that substantially obviates one or more problems due to limitations and disadvantages of the related art. 
     An advantage of the present invention is to provide an image display device and a driving method thereof, which facilitate to improve partial luminance in an image-display area by a local dimming method to partially control a backlight unit according to a display image, and simultaneously to reduce power consumption. 
     Another advantage of the present invention is to provide an image display device and a driving method thereof, which facilitates to allow various analysis algorithms by analyzing a display image in a system main body through the use of local dimming method, and simultaneously to reduce cost. 
     Additional advantages and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, there is provided an image display device comprising a liquid crystal display panel with plural display blocks; a system main body for generating image data to be displayed on the liquid crystal display panel, and generating plural block dimming data, which is applied block-by-block, by analyzing block image data to be supplied to the plural display blocks; a backlight unit for emitting light to the plural display blocks; a backlight driver for driving the backlight unit; and a panel driving part for controlling the backlight driver based on the plural block dimming data supplied from the system main body, and displaying an image based on the image data supplied from the system main body on the liquid crystal display panel. 
     At this time, the system main body modulates the image data to include the plural block dimming data therein, and supplies the modulated image data to the panel driving part. 
     In another aspect of the present invention, there is provided an image display device comprising a liquid crystal display panel with plural display blocks; a backlight unit for emitting light to the plural display blocks; a backlight driver for driving the backlight unit; and a panel driving part for controlling the backlight driver by extracting plural block dimming data, or plural scanning data together with the plural block dimming data from externally-provided image data, and simultaneously displaying an image based on the image data on the liquid crystal display panel. 
     In another aspect of the present invention, there is provided an image display device comprising a system main body for providing image data to the liquid crystal display device by controlling a transmittance of light applied to plural display blocks from a backlight unit, wherein the system main body generates the image data to be displayed on the liquid crystal display device, analyzes block image data to be supplied to the plural display blocks, generates plural block dimming data for controlling the backlight unit, and supplies the generated plural block dimming data to the liquid crystal display device. 
     In a further aspect of the present invention, there is provided a method of driving an image display device including a liquid crystal display panel with plural display blocks, and a backlight unit for emitting light to the plural display blocks, comprising generating image data in a system main body, the image data to be displayed on the liquid crystal display panel, and generating plural block dimming data by analyzing the image data to be supplied to the plural display blocks, and irradiating the plural display blocks with light emitted from the backlight unit which is driven based on the plural block dimming data supplied from the system main body, and displaying an image based on the image data supplied from the system main body on the liquid crystal display panel. 
     In addition, the driving method further includes modulating the image data in the system main body so that the modulated image data includes the plural block dimming data. 
     It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings: 
         FIG. 1  illustrates an image display device according to the embodiment of the present invention; 
         FIG. 2  illustrates a system main body in the image display device of  FIG. 1 ; 
         FIG. 3A  illustrates a display image generated based on image data of  FIG. 2 ; 
         FIG. 3B  illustrates a method of generating block dimming data for the display image of  FIG. 3A  in an image data analyzer of  FIG. 2 ; 
         FIG. 4  illustrates a method of modulating image data according to one embodiment of the present invention in an image data modulator of  FIG. 2 ; 
         FIG. 5  illustrates a method of modulating image data according to another embodiment of the present invention in an image data modulator of  FIG. 2 ; 
         FIG. 6  illustrates a timing controller of  FIG. 1 ; 
         FIG. 7  illustrates a data processing unit of  FIG. 6 ; and 
         FIG. 8  illustrates a backlight driver of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     Hereinafter, an image display device according to the present invention and a driving method thereof will be described with reference to the accompanying drawings. 
       FIG. 1  illustrates an image display device according to the embodiment of the present invention. 
     Referring to  FIG. 1 , the image display device according to the embodiment of the present invention includes a liquid crystal display panel  100 , a backlight unit  200 , a system main body  300 , a panel driving part  400 , and a backlight driver  500 . Herein, the liquid crystal display panel  100 , the backlight unit  200 , the panel driving part  400 , and the backlight driver  500  constitute a liquid crystal display device which displays an image by controlling a light transmittance according to image data provided from the system main body  300 . 
     In the liquid crystal display panel  100 , a plurality of gates lines GL and data lines DL are formed in such a way that the gate and data lines cross at right angles to each other, that is, are perpendicular to each other. Thus, pixel regions are defined by the gate lines GL and data lines DL crossing at right angles to each other, and pixels P are formed in the respective pixel regions. 
     Each of the plural pixels P includes a thin film transistor (not shown) connected to the gate line GL and data line DL; and a liquid crystal cell connected to the thin film transistor. 
     The thin film transistor supplies a data voltage supplied from the data line DL to the liquid crystal cell in response to a scan pulse supplied from the gate line GL. 
     The liquid crystal cell can be equivalently expressed as a liquid crystal capacitor (not shown) because it is provided with a common electrode facing via liquid crystal, and a pixel electrode connected to the thin film transistor. In addition, the liquid crystal cell comprises a storage capacitor (not shown) which maintains the data voltage charged on the liquid crystal capacitor (not shown) until the next data voltage is charged thereon. 
     As an electric field is formed in each pixel P of the liquid crystal display panel  100  through the use of scan pulse and data voltage supplied from the panel driving part  400 , the liquid crystal display panel  100  can control the transmittance of light emitted from the backlight unit  200  through the electric field, to thereby display the image on the liquid crystal display panel  100 . 
     The backlight unit  200  includes ‘n’ light-emitting diode arrays (hereinafter, referred to as ‘LED arrays’)  210  which are provided to confront ‘n’ display blocks on a rear surface of the liquid crystal display panel  100 . 
     Each of the ‘n’ LED arrays  210  drives ‘m’ LEDs by each block dimming voltage Vbd 1  to Vbdn supplied from the backlight driver  500 , wherein the block dimming voltage Vbd 1  to Vbdn is applied block-by-block, whereby the rear surface of the liquid crystal display panel  10  is irradiated with light. In this case, since the ‘n’ LED arrays  210  are respectively arranged in the ‘n’ display blocks divided on the rear surface of the liquid crystal display panel  100 , the liquid crystal display panel  100  is divided into ‘n’ display blocks, and the light is applied to each display block. Accordingly, the liquid crystal display panel  100  is divided into the ‘n’ display blocks to respectively confront the ‘n’ LED arrays  210 . For example, the liquid crystal display panel  100  may be divided into 80 display blocks (10×8), but it is not limited to this. The number of display blocks may vary based on the size of the liquid crystal display panel  100  and/or the number of LED arrays  210 . 
     The system main body  300  generates image data to be displayed on the liquid crystal display panel  100  including the ‘n’ display blocks; generates block dimming data, which is applied block-by-block, by analyzing the image data; and supplies the generated block dimming data to the panel driving part  400 . For this, as shown in  FIG. 2 , the system main body  300  includes an image data generator  310 , an image data analyzer  320 , an image data modulator  330 , and an image data transmitter  340 . 
     The image data generator  310  generates the image data R, G, and B to be displayed on the liquid crystal display panel  100 . Also, the image data generator  310  generates a timing synchronization signal TSS to display the image data R, G, and B on the liquid crystal display panel  100 . At this time, the timing synchronization signal TSS may include a vertical synchronous signal Vsync, a horizontal synchronous signal Hsync, a data enable signal Data Enable, and a dot (or data) clock DCLK. 
     The image data analyzer  320  generates block dimming data BD, which is applied block-by-block, by analyzing the block image data to be supplied to the respective ‘n’ display blocks. At this time, the image data analyzer  320  generates the block dimming data BD by detecting luminance or grayscale of the image data to be supplied to each display block per frame. At this time, the block dimming data BD may be the largest grayscale value, the average grayscale value, the highest luminance value, or the average luminance value among the image data to be supplied to each display block, but it is not limited to these. For example, the block dimming data BD may be a mode value, which occurs most frequently in a histogram of the image data to be supplied to each display block. 
     The image data analyzer  320  is formed in the system main body  300  whose processing speed is relatively more rapid. Thus, the image data analyzer  320  can generate the aforementioned block dimming data BD by using various image analysis algorithms to be treated in the system main body  300 . 
     For example, when the image such as sunrise is displayed on the liquid crystal display panel  100 , as shown in  FIG. 3A , the image data analyzer  320  divides the display image into the ‘n’ display blocks DB; and generates the block dimming data BD by analyzing the image data of the display image corresponding to the respective display blocks through the aforementioned method, as shown in  FIG. 3B . 
     The image data modulator  330  modulates the image data R, G, and B supplied from the image data generator  310 , so that the modulated data includes the block dimming data BD supplied from the image data analyzer  320  therein. At this time, the image data modulator  330  can modulate some pieces of the image data R, G, and B to be supplied to the first horizontal line in each display block DB into the block dimming data BD. In order to minimize deterioration of picture quality by the modulation of image data R, G, and B, the image data modulator  330  can modulate the lowermost bit of each piece of the image data corresponding to a bit number of the block dimming data BD among the image data R, G, and B into the block dimming data BD. 
     For example, as shown in  FIG. 4 , if the first block dimming data among the block dimming data BD is 8 bits and its dimming data value ‘127’, the image data modulator  330  modulates the lowermost bit value of each piece of the image data R 1 , G 1 , B 1 , R 2 , G 2 , B 2 , R 3 , G 3 , and B 3  supplied to the first horizontal line of a first display block into “01111111”, that is, the first block dimming data BD, to thereby generate the image data MR, MG, and MB including the first block dimming data BD. 
     Furthermore, the system main body  300  may generate scanning data to sequentially drive the ‘n’ LED arrays  210  according to the sequential driving of the horizontal rows of the plural display blocks; and may modulate the image data R, G, and B to include the generated scanning data and block dimming data BD therein. For minimizing the deterioration of picture quality according to the modulation of the image data R, G, and B, the image data modulator  330  can modulate both the lowermost bit of the image data corresponding to the bit number of the scanning data and the lowermost bit of the image data corresponding to the bit number of the block dimming data BD among the image data R, G, and B into the scanning data and the block dimming data BD, respectively. Preferably, the scanning data is positioned ahead of the block dimming data BD. 
     For example, as shown in  FIG. 5 , if the scanning data is 8 bits and its data value ‘1’, and the first block dimming data among the block dimming data BD is 8 bits and its dimming data value ‘127’; the image data modulator  330  modulates the lowermost bit value of each piece of the first to fourth image data R 1 , G 1 , B 1 , and R 2  supplied to the first horizontal line into the scanning data “0001”, and also modulates the lowermost bit value of each piece of the fifth to twelfth image data G 2 , B 2 , R 3 , G 3 , B 3 , R 4 , G 4 , and B 4  into “01111111”, that is, the first block dimming data BD, to thereby generate the image data MR, MG, and MB including the scanning data SD and block dimming data BD. 
     According to an interface method between the system main body  300  and the liquid crystal display device, the image data transmitter  340  transmits the image data MR, MG, and MB including the block dimming data BD supplied from the image data modulator  330  and the timing synchronization signal TSS supplied from the image data generator  310  to the panel driving part  400 . For example, the image data transmitter  330  can transmit the image data MR, MG, and MB including the block dimming data BD to the panel driving part  400  by a low-voltage differential signal LVDS interface method. 
     If the image data R, G, and B is not modulated to include the aforementioned block dimming data BD therein, the image data transmitter  340  transmits each piece of the image data R, G, and B and block dimming data BD to the panel driving part  400  through an additional signal transmission cable (not shown) according to the interface method. However, if each piece of the image data R, G, and B and block dimming data BD is transmitted to the panel driving part  400 , it is necessary to provide the additional signal transmission cable, whereby a manufacturing cost is increased due to the additional signal transmission cable. Preferably, the image data R, G, and B is modulated to include the block dimming data BD within a range of minimizing the deterioration of picture quality, and is then transmitted to the panel driving part  400 . Supposing that the system main body  300  modulates the image data R, G, and B to include the block dimming data BD therein, and transmits the modulated image data to the panel driving part  400 . 
     In  FIG. 1 , the panel driving part  400  controls the backlight driver  500  through the use of image data MR, MG, and MB including the block dimming data BD supplied from the system main body  300 ; and simultaneously displays the image based on the image data MR, MG, and MB on the liquid crystal display panel  100 . For this, the panel driving part  400  includes a timing controller  410 , a data driving circuit part  420 , and a gate driving circuit part  430 . 
     As shown in  FIG. 6 , the timing controller  410  includes a control signal generating unit  412 , a data receiving unit  414 , and a data processing unit  416 . 
     The control signal generating unit  412  generates a data control signal DCS for controlling a driving timing of the data driving circuit part  420 , and simultaneously generates a gate control signal GCS for controlling a driving timing of the gate driving circuit part  430  through the use of timing synchronization signal TSS supplied from the system main body  300 . 
     The data control signal DCS may be a source start pulse, a source sampling clock, a source output enable, a polarity control single POL, and etc. 
     The gate control signal GCS may be a gate start pulse, a gate shift clock, a gate output enable, and etc. 
     The data receiving unit  414  receives the image data MR, MG, and MB from the system main body  300  according to the interface method between the system main body  300  and the liquid crystal display device; and then supplies the received image data MR, MG, and MB to the data processing unit  416 . 
     As shown in  FIG. 7 , the data processing unit  416  includes a data aligning unit  417 , a data extracting unit  418 , and a dimming signal generating unit  419 . 
     The data aligning unit  417  aligns the image data AMR, AMG, and AMB supplied from the data receiving unit  414  so as to be proper for driving of the liquid crystal display panel  100 , and then supplies the aligned image data to the data driving circuit part  420 . 
     The data extracting unit  418  extracts only the block dimming data BD, or extracts the scanning data SD together with the block dimming data BD from the image data R, G, and B supplied from the data receiving unit  414 ; and then supplies the extracted data to the dimming signal generating unit  419 . 
     Based on indicator and identifier, which are supplied ahead of the image data MR, MG, and MB supplied from the data receiving unit  414 , the data extracting unit  418  checks whether or not the image data includes only the block dimming data BD, or the scanning data SD together with the block dimming data BD. 
     If it is determined that only the block dimming data BD is included in the image dada R, G, and B, the data extracting unit  418  extracts the lowermost bit of each piece of the image data MR, MG, and MB supplied after the indicator and identifier; and generates the block dimming data BD. For example, the data extracting unit  418  generates the block dimming data BD by extracting “01111111” from the lowermost bit value of each piece of the first to eight image data R 1 , G 1 , B 1 , R 2 , G 2 , B 2 , R 3 , and G 3  shown in  FIG. 4 ; and supplies the generated block dimming data BD to the dimming signal generating unit  419 . 
     If it is determined that the scanning data SD together with the block dimming data BD is included in the image data MR, MG, and MB; the data extracting unit  418  extracts the lowermost bit of each piece of the image data MR, MG, and MB supplied after the indicator and identifier, and generates the scanning data SD and block dimming data BD. For example, the data extracting unit  418  generates the scanning data SD by extracting “0001” from the lowermost bit value of each piece of the first to fourth image data R 1 , G 1 , B 1 , and R 2  shown in  FIG. 5 , and simultaneously generates the block dimming data BD by extracting “01111111” from the lowermost bit value of each piece of the fifth to twelfth image data G 2 , B 2 , R 3 , G 3 , B 3 , R 4 , G 4 , and B 4 ; and supplies the generated scanning data SD and block dimming data BD to the dimming signal generating unit  419 . 
     The dimming signal generating unit  419  generates a block dimming signal BDIM for driving the LED arrays  210  (See  FIG. 1 ) corresponding to the respective display blocks based on the block dimming data, or the scanning data SD together with the block dimming data BD supplied from the data extracting unit  418 ; and supplies the generated block dimming signal BDIM to the backlight driver  500  (See  FIG. 1 ). 
     In  FIG. 1 , the data driving circuit part  420  latches the image data MR, MG, and MB supplied from the timing controller  410  according to the data control signal DCS supplied from the timing controller  410 ; converts the latched image data into positive-polarity/negative-polarity analog data voltage through the use of analog positive-polarity/negative-polarity gamma voltage; generates a data voltage having a polarity corresponding to the polarity control signal POL; and supplies the generated data voltage to the data lines DL. 
     The gate driving circuit part  430  generates a scan pulse according to a gate control signal GCS supplied from the timing controller  410 ; and sequentially supplies the scan pulse to the gate lines GL. According as the gate driving circuit part  430  is formed on a substrate simultaneously with the thin film transistor, the gate driving circuit part  430  is formed in the liquid crystal display panel  100 . 
     The backlight driver  500  generates the block dimming voltages Vbd 1  to Vbdn corresponding to the block dimming signal BDIM supplied from the timing controller  410 ; and supplies the generated block dimming voltages to the backlight unit  200 . For this, as shown in  FIG. 8 , the backlight driver  500  includes a backlight controller  510 , and first to n-th LED drivers  5201  to  520   n.    
     The backlight controller  510  generates ‘n’ block dimming control signals BDCS 1  to BDCSn based on the block dimming signal BDIM supplied from the timing controller  410 , wherein the number of block dimming control signals corresponds to the number of LED arrays  210 . 
     The respective LED drivers of the first to n-th LED drivers  5201  to  520   n  generate the ‘n’ dimming voltages Vbd, that is, block dimming voltages Vbd 1  to Vbdn for driving the respective LED arrays  210  according to the block dimming control signals BDCS 1  to BDCSn supplied from the backlight controller  510 ; and supplies the generated block dimming voltages to the respective LED arrays  210 . Accordingly, the respective LED arrays  210  are driven by the block dimming voltages Vbd 1  to Vbdn respectively supplied from the first to n-th LED drivers  5201  to  520   n,  whereby the light emitted from the respective LED arrays  210  are supplied to the respective display blocks of the liquid crystal display panel  100 . 
     In the liquid crystal display device according to the embodiment of the present invention and the driving method thereof, the block dimming data is generated in the system main body  300  through the analysis of block image data to be displayed on the liquid crystal display panel  100  with the plural display blocks; and the panel driving part  400  performs the local dimming based on the block dimming data, to thereby improve partial luminance of the display image, and simultaneously to reduce power consumption. 
     In the liquid crystal display device according to the embodiment of the present invention and the driving method thereof, the system main body  300  performs the analysis of display image for the local dimming; and also modulates the image data to include the block dimming data therein, and supplies the modulated image data to the panel driving part  400 , whereby it allow various analysis algorithms simultaneously with reduction of cost. 
     In addition, the image data is modulated to include the block dimming data generated through the analysis of block image data, and then the modulated data is supplied to the panel driving part  400 , whereby it is unnecessary to provide the additional signal transmission cable, to thereby result in the reduced cost. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.