Patent Publication Number: US-8982027-B2

Title: LCD drive circuit and driving method for scanning at least two adjacent scan lines simultaneously

Description:
FIELD OF THE INVENTION 
     The present disclosure generally relates to the technical field of liquid crystal displays (LCDs), and more particularly, to an LCD drive circuit and a driving method thereof. 
     BACKGROUND OF THE INVENTION 
     As liquid crystal display (LCD) devices develop towards a low cost, a light weight, a low power consumption and high reliability, LCDs using a plurality of gate drive chips and a plurality of source drive chips have been developed. In such an LCD, scan signals are provided by the plurality of gate drive chips, data signals are provided by a plurality of source drive chips, and signal line patterns are formed on a glass substrate. 
     The LCD comprises a liquid crystal panel, which is formed by an upper substrate, an intermediate liquid crystal layer and a lower substrate in combination. The liquid crystal panel comprises a plurality of data lines arranged in a column direction and a plurality of scan lines arranged in a row direction. A plurality of thin-film transistors (TFT switches) are disposed in the form of an array at intersections between the plurality of data lines and the plurality of scan lines, and liquid crystal capacitors are formed between the TFTs and a common electrode. 
     Due to the delay of the data signals and the scan signals caused by resistances of the data lines and the scan lines in the liquid crystal panel, the pulse width of the gate driving signals is reduced and the charging time of the TFT switches is shortened. As the LCD devices are developing towards a high resolution and a high frame rate, the aforesaid problem leads to a shortened average charging time of the TFT switches within a period, thus resulting in degradation of the image frame quality. 
     SUMMARY OF THE INVENTION 
     A primary objective of the present disclosure is to provide a liquid crystal display (LCD) drive circuit and a driving method thereof which can increase an average charging time of TFT switches within a period. 
     To achieve this objective, the present disclosure provides a liquid crystal display (LCD) drive circuit, which comprises: 
     a data driver, a scan driver, a divider, a controller, a plurality of data lines and a plurality of scan lines; 
     the scan driver is connected to the plurality of scan lines; 
     the data driver is connected to the plurality of data lines; 
     the divider is configured to divide the scan lines into a plurality of groups each comprising a plurality of scan lines; and 
     the controller is configured to control the scan driver to, during scanning of each group of scan lines, scan at least two adjacent scan lines in the group simultaneously, and also control the scan driver in such a way that the at least two adjacent scan lines scanned simultaneously within a predetermined time interval are different for different image frames and positions of the at least two adjacent scan lines scanned simultaneously in each image frame are shifted downwards by at least two scan lines from those scanned simultaneously in a previous image frame, wherein the predetermined time interval is in units of image frame durations, and a magnitude of the predetermined time interval is equal to the number of scan lines in each group divided by the number of scan lines scanned simultaneously. 
     Preferably, the divider is configured to divide the scan lines into a plurality of groups each comprising eight scan lines, and the controller is configured to control the scan driver to, during scanning of each group of scan lines, scan two adjacent scan lines in the group simultaneously and also control the scan driver in such a way that every two adjacent scan lines scanned simultaneously in four consecutive image frames is different from each other. 
     Preferably, the controller is configured to control the scan driver in such a way that, within the four consecutive frames, positions of the two adjacent scan lines scanned simultaneously in each of the image frames are shifted downwards by two scan lines from those of a previous image frame. 
     To achieve the aforesaid objective, the present disclosure further provides an LCD drive circuit, which comprises a data driver, a scan driver, a divider, a controller, a plurality of data lines and a plurality of scan lines. The scan driver is connected to the plurality of scan lines; the data driver is connected to the plurality of data lines; the divider is configured to divide the scan lines into a plurality of groups each comprising a plurality of scan lines; and the controller is configured to control the scan driver to, during scanning of each group of scan lines, scan at least two adjacent scan lines in the group simultaneously, and also control the scan driver in such a way that the at least two adjacent scan lines scanned simultaneously within a predetermined time interval are different for different image frames. 
     Preferably, the predetermined time interval is in units of image frame durations, and a magnitude of the predetermined time interval is equal to the number of scan lines in each group divided by the number of scan lines scanned simultaneously. 
     Preferably, the controller is configured to control the scan driver in such a way that, within the predetermined time interval, positions of the at least two adjacent scan lines scanned simultaneously in each image frame are shifted downwards by at least two scan lines from those scanned simultaneously in a previous image frame. 
     Preferably, the divider is configured to divide the scan lines into a plurality of groups each comprising eight scan lines, and the controller is configured to control the scan driver to, during scanning of each group of scan lines, scan two adjacent scan lines in the group simultaneously and also control the scan driver in such a way that every two adjacent scan lines scanned simultaneously in four consecutive image frames is different from each other. 
     Preferably, the controller is configured to control the scan driver in such a way that, within the four consecutive frames, positions of the two adjacent scan lines scanned simultaneously in each of the image frames are shifted downwards by two scan lines from those of a previous image frame. 
     To achieve the aforesaid objective, the present disclosure provides an LCD driving method, comprising the following steps of: 
     a. dividing scan lines into a plurality of groups each comprising a plurality of scan lines; 
     b. during displaying of a current image frame, using a scan driver to scan each group of scan lines sequentially, wherein for each group of scan lines, the scan driver is controlled by a controller to scan at least two adjacent scan lines in the group simultaneously and scan other scan lines in the group sequentially; 
     c. during displaying of a next image frame, using the scan driver to scan each group of scan lines sequentially, wherein for each group of scan lines, the controller controls the scan driver in such a way that the at least two scan lines scanned simultaneously are different from those scanned simultaneously in the previous image frame; and 
     d. if each scan line in the group has been scanned once simultaneously with an adjacent scan line within a predetermined time interval, then the step b is executed; otherwise, the step c is executed. 
     In the step d, the predetermined time interval is in units of image frame durations, and a magnitude of the predetermined time interval is equal to the number of scan lines in each group divided by the number of scan lines scanned simultaneously. 
     Preferably, in the step c and the step d, the controller controls the scan driver in such a way that positions of the scan lines scanned simultaneously are shifted downwards by at least two scan lines from those scanned simultaneously in the previous image frame, and if the last scan line of the scan lines scanned simultaneously is the last one in the group, then the step d is executed; otherwise, if the last scan line of the scan lines scanned simultaneously is not the last one in the group, then the step c is executed. 
     Preferably, in the step b, the controller controls the scan driver to scan a first scan line and a second scan line in the group simultaneously and scan other scan lines in the group sequentially; and in the step c, the controller controls the scan driver in such a way that positions of the scan lines scanned simultaneously are shifted downwards by two scan lines from the previous image frame. 
     Preferably, in the step a, the scan lines are divided into a plurality of groups each comprising eight scan lines. 
     The present disclosure has the following benefits: as compared to the prior art where delay of data signals and scan signals is caused by resistances of data lines and scan lines to result in a too narrow pulse width of the gate driving signals and a too short charging time of the TFT switches, the present disclosure has at least two adjacent scan lines scanned simultaneously in each image frame. Thus, the number of scannings in each image frame is reduced and the average scanning time of the scan lines is increased, thereby resulting in an increased charging time of pixel units. Furthermore, every two scan lines scanned simultaneously within a predetermined time interval are scanned simultaneously in only a single image frame and are scanned separately in other image frames; because the time is very short, the frames perceived by the user&#39;s eyes can still be kept accurate without being perceived to have errors. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a preferred embodiment of an LCD drive circuit according to the present disclosure. 
         FIG. 2  is a flowchart of a preferred embodiment of an LCD driving method according to the present disclosure. 
         FIGS. 3 to 6  are schematic views illustrating scanning of four exemplary image frames in the LCD driving method according to the present disclosure respectively. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present disclosure is more particularly described in the following examples that are intended as illustrative only since numerous modifications and variations therein will be apparent to those skilled in the art. 
     Referring to  FIG. 1 , there is shown a schematic view of a preferred embodiment of an LCD drive circuit according to the present disclosure. The LCD drive circuit comprises a data driver  10 , a scan driver  11 , a divider (not shown), a controller  13 , a TFT switch array  14 , a plurality of data lines  15  and a plurality of scan lines  16 . The scan lines  16  and the data lines  15  are disposed to intersect with each other. The TFT switch (not labeled) is disposed near each intersection, and all the TFT switches together form the TFT switch array  14 . The scan driver  11  is connected to the plurality of scan lines  16  to sequentially scan the scan lines  16 . The data driver  10  is connected to the plurality of data lines  15  to supply a grayscale voltage for each of the data lines  15 . The divider is configured to divide the scan lines  16  into a plurality of groups, each group comprises a plurality of scan lines  16 . The controller  13  is configured to control the scan driver  11 , and during scanning of each group of scan lines  16 , the scan driver  11  scan two adjacent scan lines  16  of the group simultaneously. The controller  13  also control the scan driver  11  in such a way that, within a predetermined time interval, positions of every two adjacent scan lines  16  scanned simultaneously in an image frame is shifted downwards by two scan lines  16  from those scanned simultaneously in a previous image frame. The predetermined time interval is in units of image frame durations, and a magnitude thereof is equal to the number of the scan lines  16  in each group divided by the number of the scan lines that are simultaneously scanned. For example, if each group comprises six scan lines  16 , then the predetermined time interval is equal to a duration of three (i.e., six divided by two) image frames. 
     Referring to  FIG. 1  and  FIG. 2  together, a preferred embodiment of a driving method for the LCD drive circuit comprises the following steps: 
     Step  1 : the divider divides the scan lines  16  into a plurality of groups each comprising a plurality of scan lines  16 . 
     Step  2 : during the displaying of a current image frame, the scan driver  11  scans each group of scan lines  16  sequentially. However, for each group of scan lines  16 , the controller  13  controls the scan driver  11  to scan the first scan line  16  and the second scan line  16  in the group simultaneously and scan other scan lines  16  in the group sequentially. When a certain scan line  16  is scanned, TFT switches corresponding to the scan line  16  are turned on at the same time, and meanwhile, the data driver  10  transfers a plurality of grayscale voltages via the plurality of data lines  15  to sources of the turned-on TFT switches. The grayscale voltages are then transferred from the sources of the TFT switches to the pixel electrodes, and then applied to the liquid crystal layer so that predetermined grayscales are displayed. 
     Step  3 : during the displaying of a next image frame, the scan driver  11  scans each group of scan lines  16  sequentially. However, for each group of scan lines  16 , the controller  13  controls the scan driver  11  in such a way that positions of scan lines  16  scanned simultaneously are shifted downward by two scan lines  16  from those scanned simultaneously in the previous image frame. 
     Step  4 : if the last scan line  16  among the scan lines  16  scanned simultaneously in the step  3  is the last one in the group (i.e., each of the scan lines  16  in the group has been scanned once simultaneously with an adjacent scan line within the aforesaid predetermined time interval), then the step  2  is executed; otherwise, if the last scan line  16  among the scan lines  16  scanned simultaneously is not the last one in the group, then the step  3  is executed. 
     In other embodiments of the LCD drive circuit, the number of scan lines  16  scanned simultaneously in each group is not limited to two, and may be greater than two depending on practical needs. That is, the controller  13  may also control the scan driver  11  to, during scanning of each group, scan three or four adjacent scan lines  16  in the group simultaneously, and also control the scan driver  11  in such a way that positions of every three or four adjacent scan lines  16  scanned simultaneously in each image frame are shifted downward by three or four scan lines  16  successively within a predetermined time interval. Here, a magnitude of the predetermined time interval is equal to the number of scan lines  16  in each group divided by three or four. 
     In other embodiments of the LCD drive method, for each group of scan lines  16 , the number of scan lines  16  scanned simultaneously by the scan driver  11  is not limited to two, and may be greater than two, for example, three, four or more. If the number of scan lines  16  scanned simultaneously is three, then for each group of scan lines  16  in the step  2 , the first scan line  16 , the second scan line  16  and the third scan line  16  in the group are scanned simultaneously and then other scan lines  16  in the group are scanned sequentially; and for each group of scan lines  16  in the step  3 , positions of the scan lines  16  simultaneously scanned by the scan driver  11  are shifted downward by three scan lines  16  from those of the previous image frame. Likewise, the LCD driving method can be modified correspondingly when the number of scan lines  16  scanned simultaneously is four. 
     In other embodiments of the LCD driving method, the scan lines scanned simultaneously in the step  2  are also not limited to the first scan line  16  and the second scan line  16  in each group, but may also be other adjacent scan lines  16  in each group. Correspondingly, shifting of the positions of the scan lines  16  scanned simultaneously in the step  3  is not limited to shifting downward from those of the previous image frame, but may also be changed arbitrarily as long as the adjacent scan lines  16  scanned simultaneously are different from those scanned simultaneously in the previous image frames within the predetermined time interval; furthermore, if each scan line  16  in the group has been scanned once simultaneously with an adjacent scan line within the aforesaid predetermined time interval, then the step  2  is executed; otherwise, the step  3  is executed. 
     Correspondingly, in other embodiments of the LCD drive circuit, the controller  13  is not limited to control the scan driver  11  in such a way that positions of two adjacent scan lines  16  scanned simultaneously in each image frame are shifted downward successively as long as every two adjacent scan lines  16  scanned simultaneously within the predetermined time interval is different for different image frames. 
     As compared to the prior art, the LCD driving method of the present disclosure has at least two adjacent scan lines  16  scanned simultaneously in each image frame, so the number of scanning in each image frame is reduced, and the average scanning time of the scan lines  16  is increased to result in an increased charging time of pixel units. Furthermore, every two scan lines  16  scanned simultaneously within the predetermined time interval is scanned simultaneously in only a single image frame and are scanned separately in other image frames; because the time is very short, the frame perceived by the user&#39;s eyes can still be kept accurate without being perceived to have errors. 
     Referring to  FIGS. 3 to 6  together, the LCD driving method will be described hereinbelow by taking a case where each group comprises eight scan lines  16  and two scan lines  16  are scanned simultaneously each time as an example. 
     Step  101 : the divider divides the scan lines  16  into a plurality of groups each comprising eight scan lines  16 . 
     Step  102 : during the displaying of the first image frame, the scan driver  11  scans each group of scan lines  16  sequentially; but as shown in  FIG. 3 , for each group of scan lines  16 , the controller  13  controls the scan driver  11  to scan the first scan line  16  and the second scan line  16  in the group simultaneously, and then scan other scan lines  16  in the group sequentially. 
     When a certain scan line  16  is scanned, TFT switches corresponding to the scan line  16  are turned on at the same time, and meanwhile, the data driver  10  transfers a plurality of grayscale voltages via the plurality of data lines  15  to sources of the turned-on TFT switches. The grayscale voltages are then transferred from the sources of the TFT switches to the pixel electrodes and then applied to the liquid crystal layer so that predetermined grayscales are displayed. 
     Step  103 : during the displaying of the second image frame, the scan driver  11  scans each group of scan lines  16  sequentially; but as shown in  FIG. 4 , for each group of scan lines  16 , the controller  13  controls the scan driver  11  to sequentially scan the first scan line  16  and the second scan line  16 , scan the third scan line  16  and the fourth scan line  16  simultaneously, and then sequentially scan other scan lines  16 . 
     Step  104 : during the displaying of the third image frame, the scan driver  11  scans each group of scan lines  16  sequentially; but as shown in  FIG. 5 , for each group of scan lines  16 , the controller  13  controls the scan driver  11  to sequentially scan the first to the fourth scan lines  16 , scan the fifth scan line  16  and the sixth scan line  16  simultaneously, and then sequentially scan other scan lines  16 . 
     Step  105 : during the displaying of the fourth image frame, the scan driver  11  scans each group of scan lines  16  sequentially; but as shown in  FIG. 6 , for each group of scan lines  16 , the controller  13  controls the scan driver  11  to sequentially scan the first to the sixth scan lines  16 , and then scan the seventh scan line  16  and the eighth scan line  16  simultaneously. At this point, each of the scan lines  16  in this group has been scanned once simultaneously with an adjacent scan line  16 , so the process returns back to the step  102  for a next cycle. 
     As can be known from the above descriptions, during the displaying of the four consecutive image frames, there are scan lines  16  scanned simultaneously in each image frame, so the number of scanning in each image frame is reduced, and the average scanning time of the scan lines  16  is increased to result in an increased charging time of pixel units. Furthermore, the two scan lines  16  scanned simultaneously in each image frame are different from those in any of the other three image frames. Overall, every two scan lines  16  scanned simultaneously within a predetermined time interval is scanned simultaneously in only a single image frame, and are scanned separately in other three image frames; because the time is very short, the frame perceived by the user&#39;s eyes can still be kept accurate without being perceived to have errors. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present disclosure without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the present disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims and their equivalents.