Patent Publication Number: US-2015084939-A1

Title: Method for reducing power consumption of liquid crystal display system

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to method for reducing power consumption of a liquid crystal display (LCD), and more particularly to a method that can change a sequence of a gate driving circuit driving a plurality of scan lines and accordingly change a sequence of a source driving circuit outputting data voltages corresponding to an image signal of a frame to reduce the power consumption of the LCD system. 
     2. Description of the Prior Art 
     Please refer to  FIG. 1 , which is a diagram illustrating a liquid crystal panel  100  with a dot inversion. As shown in  FIG. 1 , sub pixels coupled to the same data line are arranged in a Zig-Zag shape as denoted by dotted lines as shown in  FIG. 1 , wherein polarities of each two adjacent sub pixels of the liquid crystal panel  100  are reverse. Taking a data line DL for example, green sub pixels  101 ,  105 , . . . and red sub pixels  103 ,  107 , . . . are coupled to the data line DL, wherein a scan line S 1  controls a switch coupled to the green sub pixel  101 , a scan line S 2  controls a switch coupled to the red sub pixel  103 , a scan line S 3  controls a switch coupled to the green sub pixel  105 , a scan line S 4  controls a switch coupled to the red sub pixel  107 , and so on. Hence, the sub pixels of the liquid crystal panel  100  are driven in the Zig-Zag shape. 
     As shown in  FIG. 1 , an advantage of using the Zig-Zag shaped driving method is that the liquid crystal panel  100  can display one dot driving effect. However, a disadvantage of the liquid crystal panel  100  is that when the liquid crystal panel  100  displays a mono-color frame or a mixed color frame, since the polarities of the adjacent sub pixels are reverse, a source driving circuit of the liquid crystal panel  100  needs to frequently output positive polarity voltages and negative polarity voltages in turn, resulting in power consumption of the liquid crystal panel  100  being very great. Hence, how to reduce the power consumption of the liquid crystal panel  100  caused by the dot inversion is an important issue for a liquid crystal panel designer. 
     SUMMARY OF THE INVENTION 
     According to an embodiment of the present invention, a method for reducing power consumption of a liquid crystal display system is provided. The LCD system includes a liquid crystal panel, a timing controller, a gate driving circuit, a source driving circuit, a plurality of scan lines, and a plurality of data lines, and the liquid crystal panel includes a plurality of sub pixels. The method includes the following steps: the timing controller receiving an image signal of a frame; the timing controller generating a gate control signal and a source control signal corresponding to the gate control signal according to the image signal of the frame; the gate driving circuit driving odd scan lines of a plurality of scan lines in turn and then driving even scan lines of the plurality of scan lines in turn according to the gate control signal; and a source driving circuit charging the plurality of sub pixels through the plurality of data lines according to the source control signal, driving sequence of the plurality of scan lines, and data voltages corresponding to the image signal, wherein voltages of the plurality of data lines are switched one time at most, and a common voltage of the liquid crystal panel is a direct current (DC) voltage. 
     In view of above, the present invention provides a method for reducing the power consumption of the LCD system. The method changes a sequence of the gate driving circuit driving the plurality of scan lines, and accordingly changes a sequence of the source driving circuit outputting data voltages corresponding to an image signal of a frame. Since the present invention can significantly reduce switching times of the data voltages corresponding to the image signal, so the present invention can significantly reduce the power consumption of the LCD system. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a liquid crystal panel with a dot inversion. 
         FIG. 2  is a diagram illustrating an LCD system. 
         FIG. 3  is a flowchart illustrating a method for reducing the power consumption of the LCD system according to an embodiment of the present invention. 
         FIG. 4  is a diagram illustrating the liquid crystal panel of the LCD system displaying a red color frame. 
         FIG. 5  is a diagram illustrating the liquid crystal panel of the LCD system displaying a frame having green and blue colors. 
         FIG. 6  is a diagram illustrating the liquid crystal panel of the LCD system displaying a frame having red, blue, and green colors. 
     
    
    
     DETAILED DESCRIPTION 
     Please refer to  FIGS. 2-6 .  FIG. 2  is a diagram illustrating an LCD system  10 .  FIG. 3  is a flowchart illustrating a method for reducing power consumption of the LCD system according to an embodiment of the present invention.  FIG. 4  is a diagram illustrating a liquid crystal panel of the LCD system  10  displaying a red color frame.  FIG. 5  is a diagram illustrating the liquid crystal panel of the LCD system  10  displaying a frame having green and blue colors.  FIG. 6  is a diagram illustrating the liquid crystal panel of the LCD system  10  displaying a red, blue and green color frame. 
     As shown in  FIG. 2 , the LCD system  10  includes a liquid crystal panel  102 , a timing controller  104 , a gate driving circuit  106 , a source driving circuit  108 , a plurality of scan lines S 1 -SN, and a plurality of data lines D 1 -DM. The liquid crystal panel  102  includes a plurality of sub pixels, and N and M are positive integers. The liquid crystal panel  102  is a dot inversion liquid crystal panel and sub pixels of the plurality of sub pixels of the liquid crystal panel  102  coupled to a data line of the data lines D 1 -DM are arranged in a Zig-Zag shape. As shown in  FIG. 2 , the gate driving circuit  106  and the source driving circuit  108  are coupled to the timing controller  104 , and each sub pixel of the liquid crystal panel  102  corresponds to one scan line of the scan lines S 1 -SN and one data line of the data lines D 1 -DM. The method in  FIG. 3  is illustrated using the LCD system  10  in  FIG. 2 . Detailed steps are as follows: 
     Step  300 : Start. 
     Step  302 : The timing controller  104  receives an image signal IS of a frame. 
     Step  304 : The timing controller  104  generates a gate control signal GCS and a source control signal SCS corresponding to the gate control signal GCS according to the image signal IS. 
     Step  306 : The gate driving circuit  106  drives odd scan lines of the plurality of scan lines S 1 -SN in turn and then driving even scan lines of the plurality of scan lines S 1 -SN in turn according to the gate control signal GCS. 
     Step  308 : The source driving circuit  108  charges the plurality of sub pixels through the plurality of data lines D 1 -DM according to the source control signal SCS, a driving sequence of the plurality of scan lines S 1 -SN, and data voltages corresponding to the image signal IS, wherein voltages of the plurality of data lines D 1 -DM are switched one time at most, and a common voltage of the liquid crystal panel  102  is a direct current (DC) voltage. 
     Step  310 : End. 
     In step  304 , the timing controller  104  can generate the gate control signal GCS and the source control signal SCS corresponding to the gate control signal GCS according to a timing and a position displayed on the liquid crystal panel  102  of the image signal IS of the frame. In step  306 , the gate driving circuit  106  drives the odd scan lines S 1 , S 3 , . . . of the plurality of scan lines S 1 -SN in turn and then driving the even scan lines S 2 , S 4 , . . . of the plurality of scan lines S 1 -SN in turn according to the gate control signal GCS. 
     However, in another embodiment of the present invention, the gate driving circuit  106  drives the even scan lines S 2 , S 4 , . . . of the plurality of scan lines S 1 -SN in turn and then driving the odd scan lines S 1 , S 3 , . . . of the plurality of scan lines S 1 -SN in turn according to the gate control signal GCS. Hence, in step  308 , the source driving circuit  108  charges corresponding sub pixels of the plurality of sub pixels of the liquid crystal panel  102  through data lines of the data lines D 1 -DM corresponding to the odd scan lines S 1 , S 3 , . . . according to the source control signal SCS, the driving sequence of the odd scan lines S 1 , S 3 , . . . , and the data voltages corresponding to the image signal IS, wherein when the liquid crystal panel  102  displays the image corresponding to the image signal IS, the common voltage of the liquid crystal panel  102  is a direct current voltage. 
     As shown in  FIG. 4 , when the image signal IS corresponds to a red color, the gate driving circuit  106  will first drive the odd scan lines S 1 , S 3 , . . . of the scan lines S 1 -SN in turn according to the gate control signal GCS. That is, in the liquid crystal panel  102 , switches of sub pixels coupled to the odd scan lines S 1 , S 3 , . . . are turned on in turn. Hence, taking the data line D 1  for example, since switches corresponding to red sub pixels  1021 ,  1023 ,  1025  . . . are turned on in turn, the source driving circuit  108  may charge the red sub pixels  1021 ,  1023 ,  1025  . . . of the liquid crystal panel  102  according to a driving sequence of the odd scan lines S 1 , S 3 , . . . and the data voltages corresponding to the image signal IS. 
     As shown in  FIG. 4 , since polarities of the red sub pixels  1021 ,  1023 ,  1025 , . . . are positive, the data voltages for charging the red sub pixels  1021 ,  1023 ,  1025 , . . . of the liquid crystal panel  102  are a positive voltage (such as 5V). However, the present invention does not limit the data voltages for charging the red sub pixels  1021 ,  1023 ,  1025  . . . of the liquid crystal panel  102  being 5V. 
     Although the present invention merely illustrate operations of the odd scan lines S 1 , S 3  and S 5  in  FIG. 4 , operations of other odd scan lines are similar to those of the odd scan lines S 1 , S 3  and S 5 , and are omitted for brevity. Further, as shown in  FIG. 4 , when the image signal IS corresponds to a red color, the gate driving circuit  106  will drive the even scan lines S 2 , S 4 , . . . of the scan lines S 1 -SN in turn after driving first drive the odd scan lines S 1 , S 3 , . . . of the scan lines S 1 -SN in turn according to the gate control signal GCS. That is, in the liquid crystal panel  102 , switches of sub pixels coupled to the even scan lines S 2 , S 4 , . . . are turned on in turn. Hence, taking the data line D 2  for example, since switches corresponding to red sub pixels  1022 ,  1024 ,  1026  . . . are turned on in turn, the source driving circuit  108  may charge the red sub pixels  1022 ,  1024 ,  1026  . . . of the liquid crystal panel  102  according to a driving sequence of the even scan lines S 2 , S 4 , . . . and the data voltages corresponding to the image signal IS. 
     As shown in  FIG. 4 , since polarities of the red sub pixels  1022 ,  1024 ,  1026  . . . are negative, the data voltages for charging the red sub pixels  1022 ,  1024 ,  1026  . . . of the liquid crystal panel  102  are a negative voltage (such as −5V). However, the present invention does not limit the data voltages for charging the red sub pixels  1022 ,  1024 ,  1026  . . . of the liquid crystal panel  102  being −5V. 
     Moreover, as shown in  FIG. 4 , taking the data line D 2  for example, when the image signal IS corresponds to a red color, green sub pixels  1027 ,  1029 ,  1031 , . . . corresponding to the odd scan lines S 1 , S 3 , S 5 , . . . are turned off. Thus, data voltages of the data line D 2  corresponding to the odd scan lines S 1 , S 3 , S 5 , . . . are 0. 
     Further, although the present invention merely illustrate operations of the even scan lines S 2 , S 4  and S 6  in  FIG. 4 , operations of other even scan lines are similar to those of the even scan lines S 2 , S 4  and S 6 , and are omitted for brevity. Further, as shown in  FIG. 4 , switching times of the data voltages (a positive voltage and a negative volatge) of the plurality of data lines D 1 -DM corresponding to the image signal IS are significantly reduced. For example, the data voltages of the data lines D 1  and D 2  are switched one time at most. 
     Moreover, since the gate driving circuit  106  first drives the odd scan lines of the scan lines S 1 -SN in turn according to the gate control signal GCS, and then drives the even scan lines of the scan lines S 1 -SN in turn, data voltages corresponding to the image signal IS outputted by the source driving circuit  108  need to correspond to a driving sequence of the scan lines S 1 -SN. Further, when the image signal IS corresponds to a red color, green sub pixels and blue sub pixels of the liquid crystal panel  102  are turned off. At this moment, the green sub pixels and the blue sub pixels of the liquid crystal panel  102  present black. That is, the liquid crystal panel  102  utilizes the red sub pixels to display a red frame. 
     Similarly, as shown in  FIG. 5 , taking the data line D 2  for example, when the image signal IS corresponds to a green color and a blue color (the red sub pixels of the liquid crystal panel  102  are turned off), since switches corresponding to the green sub pixels  1027 ,  1029 ,  1031 , . . . are turned on in turn, the source driving circuit  108  may charge the green sub pixels  1027 ,  1029 ,  1031  . . . of the liquid crystal panel  102  according to a driving sequence of the odd scan lines S 1 , S 3 , . . . and data voltages corresponding to the image signal IS. 
     As shown in  FIG. 5 , since polarities of the green sub pixels  1027 ,  1029 ,  1031 , . . . are negative, the data voltages for charging the green sub pixels  1027 ,  1029 ,  1031 , . . . of the liquid crystal panel  102  are a negative voltage (such as −5V). Further, as shown in  FIG. 5 , taking the data line D 2  for example, when the image signal IS corresponds to a green color and a blue color, the red sub pixels  1022 ,  1024 ,  1026 , . . . are turned off. Thus, data voltages of the data line D 2  corresponding to the even scan lines S 2 , S 4 , S 6 , . . . are 0. 
     Moreover, as shown in  FIG. 5 , taking the data line D 3  for example, since switches corresponding to green sub pixels  1028 ,  1030 ,  1032  are turned on in turn, the source driving circuit  108  may charge the green sub pixels  1028 ,  1030 ,  1032  . . . of the liquid crystal panel  102  according to a driving sequence of the even scan lines S 2 , S 4 , . . . and data voltages corresponding to the image signal IS. As shown in  FIG. 5 , since polarities of the green sub pixels  1028 ,  1030 ,  1032  . . . are positive, the data voltages for charging the green sub pixels  1028 ,  1030 ,  1032  . . . of the liquid crystal panel  102  are a positive voltage (such as 5V). 
     Moreover, as shown in  FIG. 5 , taking the data line D 3  for example, since switches corresponding to blue sub pixels  1033 ,  1035 ,  1037  are turned on in turn, the source driving circuit  108  may charge the blue sub pixels  1033 ,  1035 ,  1037  . . . of the liquid crystal panel  102  according to a driving sequence of the odd scan lines S 1 , S 3 , . . . and the data voltage corresponding to the image signal IS. As shown in  FIG. 5 , since polarities of the blue sub pixels  1033 ,  1035 ,  1037  . . . are positive, the data voltages for charging the blue sub pixels  1033 ,  1035 ,  1037  . . . of the liquid crystal panel  102  are a positive voltage (such as 5V). 
     Further, although the present invention merely illustrate operations of the odd scan lines S 1 , S 3  and S 5 , and the even scan lines S 2 , S 4  and S 6  in  FIG. 5 , operations of other odd and even scan lines of the scan lines S 1 -SN are similar and are omitted for brevity. 
     Similarly, as shown in  FIG. 6 , when the image signal IS corresponds to a frame having red, blue, and green colors (even column sub pixels of the liquid crystal panel  102  are turned off, thus the even column sub pixels of the liquid crystal panel  102  present black), taking the data line D 3  for example, since switches corresponding to the blue sub pixels  1033 ,  1035 ,  1037  are turned on in turn, the source driving circuit  108  may charge the blue sub pixels  1033 ,  1035 ,  1037  . . . of the liquid crystal panel  102  according to a driving sequence of the odd scan lines S 1 , S 3 , . . . and data voltages corresponding to the image signal IS. As shown in  FIG. 6 , since polarities of the blue sub pixels  1033 ,  1035 ,  1037  . . . are positive, the data voltages for charging the blue sub pixels  1033 ,  1035 ,  1037  . . . of the liquid crystal panel  102  are a positive voltage (such as 5V). 
     Moreover, as shown in  FIG. 6 , taking the data line D 3  for example, the green sub pixels  1028 ,  1030 ,  1032 , . . . corresponding to the even scan lines S 2 , S 4 , S 6 , . . . are turned off. Thus, data voltages of the data D 3  corresponding to the even scan lines S 2 , S 4 , S 6 , . . . are 0. 
     Moreover, taking the data line D 4  for example, since switches corresponding to blue sub pixels  1034 ,  1036 ,  1038  are turned on in turn, the source driving circuit  108  may charge the blue sub pixels  1034 ,  1036 ,  1038  . . . of the liquid crystal panel  102  according to the driving sequence of the even scan lines S 2 , S 4 , . . . and data voltages corresponding to the image signal IS. As shown in  FIG. 6 , since polarities of the blue sub pixels  1034 ,  1036 ,  1038  . . . are negative, the data voltages for charging the blue sub pixels  1034 ,  1036 ,  1038  . . . of the liquid crystal panel  102  are a negative voltage (such as −5V). 
     Moreover, as shown in  FIG. 6 , taking the data line D 4  for example, the red sub pixels  1039 ,  1041 ,  1043 , . . . corresponding to the odd scan lines S 1 , S 3 , S 5 , . . . are turned off. Thus, data voltages of the data D 4  corresponding to the odd scan lines S 1 , S 3 , S 5 , . . . are 0. 
     Further, although the present invention merely illustrate operations of the odd scan lines S 1 , S 3  and S 5 , and the even scan lines S 2 , S 4  and S 6  in  FIG. 6 , operations of other odd and even scan lines of the scan lines S 1 -SN are similar and are omitted for brevity. 
     In view of above, the method for reducing the power consumption of the LCD system provided by the present invention changes a sequence of the gate driving circuit driving the plurality of scan lines, and accordingly changes a sequence of the source driving circuit outputting data voltages corresponding to an image signal of a frame, to reduce the power consumption of the LCD system. Therefore, the present invention can significantly reduce switching times of the data voltages corresponding to the image signal, so the present invention can significantly reduce the power consumption of the LCD system. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.