Patent Publication Number: US-7719505-B2

Title: Display device and driving method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims the priority benefit of Taiwan application serial no. 95144210, filed Nov. 29, 2006. All disclosure of the Taiwan application is incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a driving method. More particularly, the present invention relates to a driving method for a display device. 
   2. Description of Related Art 
   Generally speaking, a liquid crystal display (LCD) device includes a display array structure, and each display unit in the display array has a thin film transistor (TFT). Images displayed by LCDs have high contrast and wide linear grayscale. Moreover, the LCDs have the advantages of square display, low power consumption, and low radiation, so users can enjoy an optimal visual environment. The development of the technology of LCD devices meets the users&#39; requirement. According to the requirements of the users, the size of the LCDs is increased, so it has been an important topic to develop a large-size LCDs. 
   It is known that the LCD device is a hold type display, which is different from the impulse type display of a cathode ray tube display device. Referring to  FIG. 1 , the hold type display refers that a display unit remains in a same tone when a frame is displayed. Considering the operation of the circuit, when a frame F 11  is displayed, a voltage of a storage capacitor in the display unit remains constant until the LCD device displays next frame F 12 . However, according to the characteristics of the hold type display, when dynamic images are displayed, a user obviously views blur edges even in an ideal condition (R/T=0) due to visual integration of human eyes. 
   Therefore, in the conventional LCD device, the hold type display realizes the impulse type display of dynamic images through impulse-driving.  FIG. 2  is an architectural view of the system of a conventional impulse type display. As shown in  FIG. 2 , gate output enable (OE) signals are divided into two groups, and scan driving units  11 - 14  match with independent vertical start signals STV 1 -STV 4  respectively, so as to insert a black level image data between any two image data.  FIG. 3  is a timing diagram of the system of  FIG. 2 . As shown in  FIG. 3 , the writing of the image data and the writing of the black level data share the time of a same scan line (time division processing). Therefore, in case of high resolution and high frame rate, the charging will be insufficient, so the images cannot be displayed correctly. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to a display device, which includes a plurality of data lines, a plurality of scan lines, a display array, a data driver, and a scan driver. The plurality of scan lines and the plurality of data lines are interlaced. The display array has a plurality of display units, and each of the display units corresponds to a set of data line and scan line interlaced with the data line. The data driver controls the plurality of data lines and output an image signal. The image signal has a plurality of image sections, and the plurality of image sections correspond to the plurality of scan lines respectively. The scan driver drives the plurality of scan lines. In the display device according to the present invention, each predetermined number of image sections is defined as a group, each group of the image sections has a first and a second reset data, and each group of scan lines is divided into a first and a second portions. The scan driver sequentially drives the scan lines of the first group according to a first start waveform, and the data driver writes the first group of image sections into the display units of the scan lines of the first group respectively through the data lines. After a predetermined period, the scan driver drives the first group of scan lines according to a second start waveform, and the data driver writes the first reset data into the display units on the scan lines of the first portion, and writes the second reset data into the display units on the scan lines of the second portion through the data lines. 
   The present invention is further directed to a driving method for a display device. The display device includes a plurality of data lines, a plurality of scan lines, and a plurality of display units corresponding to the data lines and the scan lines interlaced with the data lines. The driving method includes the following steps. An image input signal is received. The image input signal is divided into a plurality of image sections corresponding to the plurality of scan lines respectively. Each predetermined number of image sections is defined as a group. Each group of the scan lines is divided into a first second portion and a second portion. A first reset data and a second reset data are inserted into each group of image sections to generate an image data. The first group of scan lines is sequentially driven according to a first start waveform. The first group of image sections is written into the display units on the scan lines of the first group respectively through the data lines. The first group of scan lines is driven according to a second start waveform. The first reset data is written into the display units on the scan lines of a first portion through the data lines. And, the second reset data is written into the display units on the scan lines of a second portion through the data lines. 
   In order to make the aforementioned objectives, features and advantages of the present invention comprehensible, a preferred embodiment accompanied with figures is described in detail below. 
   It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
       FIG. 1  shows an LCD display device that drives the display unit by means of hold type driving. 
       FIG. 2  is an architectural view of the system simulating conventional impulse driving. 
       FIG. 3  is a timing diagram of the system of  FIG. 2 . 
       FIG. 4  is a schematic view of the display device according to a first embodiment of the present invention. 
       FIG. 5  is a schematic view of the display panel of the first embodiment. 
       FIG. 6  shows a data processing cycle of the first embodiment of the present invention. 
       FIGS. 7   a  and  7   b  are driving timing diagrams of the scan lines according to the first embodiment of the present invention. 
       FIG. 8  is a schematic view illustrating polarities of the data according to the first embodiment of the present invention. 
       FIG. 9  is a schematic view of the control of the driving unit according to the present invention. 
       FIG. 10  shows the data processing cycle of a second embodiment of the present invention. 
       FIGS. 11   a  and  11   b  are timing diagrams of the display device according to the second embodiment of the present invention. 
       FIG. 12  is a schematic view illustrating polarities of the data according to the second embodiment of the present invention. 
   

   DESCRIPTION OF EMBODIMENTS 
     FIG. 4  shows a display device according to a first embodiment of the present invention. Referring to  FIG. 4 , the display device  4  includes a receiving unit  40 , an operating unit  41 , a data rearrangement unit  42 , a timing generation unit  43 , and a display panel  44 . Referring to  FIG. 5 , the display panel  44  further includes a data driver  50 , a scan driver  51 , and a display array  52 . The data driver  50  controls data lines D 1 -D m . The scan driver  51  controls a plurality of scan lines, and has a plurality of driving units. The data lines D 1 -D m  are interlaced with all of the scan lines. The display array  52  has a plurality of display units, and each display unit correspond to the data line and the scan line interlaced with the data line, e.g., the data line D 1  and the scan line G 53   1  correspond to the display unit  52   a.    
   Referring to  FIG. 4 , the receiving unit  40  receives a data enable signal DE, an input image signal DATA, and a clock signal CLK from an external device. The operating unit  41  is coupled to the receiving unit  40 , and generates a plurality of reset data RD according to the data enable signal DE, the input image signal DATA, and the clock signal CLK. The data rearrangement unit  42  is coupled to the receiving unit  40  and the operating unit  41 , and receives the data enable signal DE, the input image signal DATA, the clock signal CLK, and the plurality of reset data RD. The reset data RD can be an all-black frame or an all-white image, or an image of any single grayscale. The data rearrangement unit  42  rearranges the input image signal DATA and the plurality of reset data RD, and the details will be described below. 
   The data rearrangement unit  42  divides the input image signal DATA into a plurality of image sections DS, and each image section DS correspond to a display unit on a scan line. In other words, the data of each image section DS is input into a display unit on one scan line. The data rearrangement unit  42  defines each predetermined number of image sections DS as one group, and a plurality of reset data RD is inserted into one group. After the input image signal DATA and the plurality of reset data RD are rearranged, the data rearrangement unit  42  generates an image signal In_DATA. In the first embodiment of the present invention, the operating unit  41  generates two reset data RD. The data rearrangement unit  42  defines four image sections DS as one group, and two reset data RD are inserted into one group. Herein, the reset data RD displaying all-black frames is taken as an example. 
     FIG. 6  shows a data processing cycle of the display device according to the first embodiment of the present invention. For example, referring to the input image signal DATA of  FIG. 6 , the image sections DS 1 -DS 4  are defined as one group P 1 . Referring to the image signal In_DATA, two reset data RD 1  and RD 2  are inserted into the group P 1 , in which the reset data RD 1  is arranged between the image sections DS 3  and DS 4 , and the reset data RD 2  is arranged subsequent to the image section DS 4 . Moreover, as the data rearrangement unit  42  rearranges the input image signal DATA and the plurality of reset data RD, as compared with the input image data DATA, the image data In_DATA is delayed for a time Tdelay. Similarly, the data rearrangement unit  42  generates a delayed data enable signal In_DE. 
   In the first embodiment of  FIG. 5 , the scan driver  51  having four driving units  53 - 56  is taken as an example. As the data rearrangement unit  42  defines every four image sections DS as one group, in the first embodiment, each driving unit controlling four scan lines is taken as an example. As shown in  FIG. 5 , the driving unit  53  controls the scan lines G 53   1 -G 53   4 , the driving unit  54  controls the scan lines G 54   1 -G 54   4 , the driving unit  55  controls the scan lines G 55   1 -G 55   4 , and the driving unit  56  controls the scan lines G 56   1 -G 56   4 . 
   The timing generation unit  43  receives the image signal In_DATA, and generates a plurality of control signals CS according to the image signal In_DATA. The control signals CS at least include a gate timing signal CPV, a vertical start signal STV, and a plurality of output enable signals OE. The timing generation unit  43  transmits the image signal In_DATA and the data enable signal In_DE to the data driver  50 , and transmits the gate timing signal CPV, the vertical start signal STV, and the plurality of output enable signals OE to the scan driver  51 . It should be noted that in this embodiment, a group of scan lines is controlled by one driving unit of the scan driver  51 , and the output enable signals OE of the driving units are independent from one another. In other words, as four driving units are taken as an example in the first embodiment, the timing generation unit  43  generates four independent output enable signals OE 1 -OE 4 , and transmits them to the driving units  53 - 56  respectively. Referring to  FIG. 6 , each output enable signal has two waveforms OE_D and OE_B. For example, when the output enable signal OE 1  has the image section enable waveform OE_D, the driving unit  53  allows the display units on the scan line G 53   1 -G 53   4  of the group P 1  to receive corresponding image sections DS 1 -DS 4  respectively. When the output enable signal OE 1  has the reset data enable waveform OE_B, the driving unit  53  allows the display units on the scan line G 53   1 -G 53   4  in the group P 1  to receive corresponding reset data RD 1  and RD 2  respectively. In addition, referring to  FIG. 5 , the vertical start signal STV is sequentially provided to the driving units  53 - 56 . 
     FIGS. 7   a  and  7   b  are driving timing diagrams of the scan lines according to the first embodiment of the present invention. The vertical start signal STV also has two waveforms STV_D and STV_B respectively indicating the start of writing the data section and the reset data. Referring to  FIGS. 5 and 6 , for example, the data sections DS 1 -DS 4  belong to the group P 1 , and respectively correspond to the display units on the scan lines G 53   1 -G 53   4 . The all-black reset data RD 1  is inserted between the data sections D 3  and D 4 , and the all-black reset data RD 2  is inserted subsequent to the data section DS 4 . According to the first embodiment of the present invention, two reset data RD 1  and RD 2  are inserted in the group P 1 , so the group P 1  of the scan lines G 53   1 -G 53   4  is divided into a first portion and a second portion, so as to receive the reset data RD 1  and RD 2  respectively. In  FIGS. 7   a  and  7   b,  the group P 1  of scan lines G 53   1 -G 53   4  and the control signals thereof are taken as an example. Referring to  FIG. 7   a,  when the vertical start signal STV exhibits the image section start waveform STV_D, the driving unit  53  sequentially drives the scan lines G 53   1 -G 53   4  according to the image section start waveform STV_D. After the driving unit  53  sequentially drives the scan lines G 53   1 -G 53   4 , the driving unit  54  sequentially drives the scan lines G 54   1 -G 54   4  according to the data section start waveform STV_D, and the driving units  55  and  56  perform the same driving (not shown in  FIG. 7   a ). When the scan lines G 53   1 -G 53   4  are driven, the driving unit  53  allows the display units on the scan lines G 53   1 -G 53   4  of the group P 1  to receive corresponding image sections DS 1 -DS 4  respectively according to the low level of the gate timing signal CPV and the image section enable waveform OE_D. It should be noted that as one black reset data is inserted into every four image sections in the image signal In_DATA, the image section enable waveform OE_D of each output enable signal OE remain at a high level for a relatively long time in portions corresponding to the black reset data RD 1  and RD 2 , so as to shield the black reset data RD 1  and RD 2  from being loaded into the display units. 
   Referring to  FIG. 7   b,  when the vertical start signal STV has the reset data start waveform STV_B, the driving unit  53  drives the scan lines G 53   1  and G 53   3  (the scan lines of the first portion of the group P 1 ) at the same time according to the reset data start waveform STV_B, and then drives the scan line G 53   2  and G 53   4  (the scan lines of the second portion of the group P 1 ) at the same time. When the driving unit  53  drives the scan lines G 53   1 -G 53   4 , the driving unit  54  drives the scan lines G 54   1  and G 54   3  at the same time according to the data section start waveform STV_B, and then drives the scan lines G 54   2  and G 54   4  at the same time. The driving units  55  and  56  perform the same driving (not shown in  FIG. 7   b ). When the scan lines G 53   1  and G 53   3  are driven at the same time, the driving unit  53  allows the display units on the scan lines G 53   1  and G 53   3  of the group P 1  to receive the reset data RD 1  at the same time according to a first low level of the reset data enable waveform OE_B. Then, when the scan lines G 53   2  and G 53   4  are driven at the same time, the driving unit  53  allows the display units on the scan lines G 53   2  and G 53   4  of the group P 1  to receive the reset data RD 2  at the same time according to a second low level of the reset data enable waveform OE_B. 
   As the vertical start signal STV is sequentially provided to the driving units  53 - 56 , subsequent to the driving unit  53 , starting from the driving unit  54 , the driving units  54 - 56  also indicate the start of writing the data section and the reset data respectively according to the waveforms STV_D and STV_B of the vertical start signal STV. 
   According to the first embodiment of the present invention, for a driving unit, the writing of the data section and the writing of the reset data are performed with a predetermined time interval. Referring to  FIG. 8 , the reset signal section start waveform STV_B appear after a predetermined period Tbk since the image section start waveform STV_D of the vertical start signal STV appears. 
   Referring to  FIG. 8  again, the polarity change of the image sections and the reset data is also shown. Each frame has two time points of the polarity change. Referring to  FIG. 8 , in a (N−1) th  frame, the polarities POL of the image sections are “−+−+− . . . ” sequentially. When the image section start waveform STV_D of the vertical start signal STV appears, it indicates a start point of the image section of one frame, and the polarities of the image sections must be changed. Therefore, in an N th  frame, when the image section start waveform STV_D appears, the polarities POL of the image sections are changed to “+−+− . . . ” sequentially. Similarly, referring to  FIG. 8 , in the (N−1) th  frame, the polarities POL of the reset data image sections are “+−+− . . . ” sequentially. When the reset data start waveform STV_B of the vertical start signal STV appears, it indicates a start point of the reset data of one frame, and the polarities of the reset data must be changed. Therefore, in the N th  frame, when the reset data start waveform STV_B appears, the polarities POL of the reset data are changed to “−+−+ . . . ” sequentially. It is known that the polarities in each frame is changed twice at time points when the image section start waveform STV_D of the vertical start signal STV appears and when the reset data start waveform STV_B of the vertical start signal STV appears. 
   According to the first embodiment of  FIG. 5 , four driving units  53 - 56  are taken as an example. Output enable signals OE 1 -OE 4  that are input to the driving units  53 - 56  are respectively independent from one another, and each output enable signal has an image section enable waveform OE_D and a reset data enable waveform OE_B. In some embodiments, the image section enable waveform OE_D can be designed to be partially overlapped between any two driving units, so as to facilitate the conversion between different waveforms, as shown in  FIG. 9 . For example, in a frame, the image section enable waveform OE_D of the output enable signal OE 1  and the image section enable waveform OE_D of the output enable signal OE 2  have an overlapped area Tovp between the driving units  53  and  54 . Similarly, the image section enable waveform OE_D of the output enable signal OE 2  and the image section enable waveform OE_D of the output enable signal OE 3  have an overlapped area Tovp between the driving units  54  and  55 , and the image section enable waveform OE_D of the output enable signal OE 3  and the image section enable waveform OE_D of the output enable signal OE 4  have an overlapped area Tovp between the driving units  55  and  56 . 
   To sum up, the present invention defines a predetermined number of image sections as a group, and inserts an all-black or an all-white reset data, or a reset data of any single grayscale. Through the corresponding control signals such as the gate timing signal CPV, the vertical start signal STV, and the output enable signal OE, each display unit can display a black or all-white image or an image of any single grayscale after displaying normal images for a predetermined period, so as to simulate the impulse driving, thus preventing the overlapping of images of two adjacent frames and alleviating the phenomenon of blurred images. 
   As described above, one data section DS is corresponding to display units on one scan line. Therefore, according to the polarities POL of  FIG. 8 , it is known that the scan driver  51  drives the scan lines through line inversion. In some embodiments, the scan driver  51  can drive the scan lines through other types of inversion, e.g., two-line inversion.  FIG. 10  shows a data processing cycle of the display device according to a second embodiment of the present invention, in which the scan driver drives the scan lines through the two-line inversion. It is known from  FIG. 10  that as the scan lines are driven through the two-line inversion, the reset data RD 1  is arranged between the image section DS 2  and the image section DS 3 , and the reset data RD 2  is arranged subsequent to image section DS 4 . As the arrangement of the reset data RD of the second embodiment is different from that of the first embodiment, the waveform of the output enable signal OE of the second embodiment is also different from that of the first embodiment. 
     FIGS. 11   a  and  11   b  are timing diagrams of the display device according to the second embodiment of the present invention. The scan lines are driven through the two-line inversion in the second embodiment, so the waveform of the vertical start signal STV of the second embodiment is different from that of the first embodiment. 
   Referring to  FIG. 11   a,  when the vertical start signal STV exhibits the image section start waveform STV_D, the driving unit  53  sequentially drives the scan lines G 53   1 -G 53   4  according to the image section start waveform STV_D. Then, the driving units  54  and  56  perform the same driving of the scan lines. When the scan lines G 53   1 -G 53   4  are driven, the driving unit  53  allows the display units on the scan lines G 53   1 -G 53   4  of the group P 1  to receive the corresponding image sections DS 1 -DS 4  respectively according to the low level of the gate timing signal CPV and the image section enable waveform OE_D. 
   Referring to  FIG. 11   b,  when the vertical start signal STV has the reset data start waveform STV_B, the driving unit  53  drives the scan lines G 53   1  and G 53   2  (the scan lines of the first portion of the group P 1 ) at the same time according to the reset data start waveform STV_B, and then drives the scan lines G 53   3  and G 53   4  (the scan lines of the second portion of the group P 1 ) at the same time. After the driving unit  53  drives the scan lines G 53   1 -G 53   4 , the driving units  54  and  56  perform the same driving of the scan lines. When the scan line G 53   1  and G 53   2  are driven, the driving unit  53  allows the display units on the scan lines G 53   1  and G 53   2  of the group P 1  to receive the reset data RD 1  at the same time according to a first low level of the reset data enable waveform OE_B. Then, when the scan line G 53   3  and G 53   4  are driven, the driving unit  53  allows the display units on the scan lines G 53   3  and G 53   4  of the group P 1  to receive the reset data RD 2  at the same time according to a second low level of the reset data enable waveform OE_B. 
     FIG. 12  is a schematic view of the polarities of the data of the second embodiment of the present invention. In the (N−1) th  frame, the polarities POL of the image sections are “−−++ . . . ” in a sequence. In the N th  frame, when the image section start waveform STV_D of the vertical start signal STV appears, the polarities POL of the image sections are sequentially changed to “++−− . . . ”. Similarly, referring to FIG.  12 , in the N th  frame, the polarities POL of the reset data image sections are “+−+− . . . ” sequentially. In the N th  frame, when the reset data start waveform STV_B of the vertical start signal STV appears, the polarities POL of the reset data are changed to “−+−+ . . . ” sequentially. 
   It will be apparent to persons of ordinary art in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.