Abstract:
A driving method and data driving circuit of display is provided. A frame is divided into a first field and a second field, and respectively driving a first and a second part of those data lines within the first and second field. Sequentially driving a first part of the data lines corresponding to the first field and driving a second part of the data lines corresponding to the second field. While said data lines are driving, every two adjacent pixels are respectively applied with a first common voltage with a first polarity and applied with a second common voltage with a second polarity within a time period of the frame, where the first polarity is opposite to the second polarity, and the first part and the second part of the data lines are interlaced arrangement.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the priority benefit of Taiwan application serial no. 94137767, filed Oct. 28, 2005. All disclosure of the Taiwan application is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of Invention  
         [0003]     The present invention relates to a driving method and a data driving circuit of a display. More particularly, the present invention relates to a driving method and a data driving circuit of a display using alternating current common electrode voltage (AC Vcom) and a dot inversion manner for driving.  
         [0004]     2. Description of Related Art  
         [0005]     As generally known in the art, a function of a display is displaying images to audiences, and quality of images shown in the display will influence feeling of the audiences. Audiences usually consider the display, such as a liquid crystal display, to a bad display if they have bad feeling about the displayed images which have problems like flicker and crosstalk. Flicker and crosstalk problems make color edge of the images not sharp enough to make the images clear, which burden the audiences if they try to look at the images displayed. Factors that influence the level of flicker and crosstalk are driving method and data driving circuit of the display.  
         [0006]     A common electrode voltage (“Vcom”, as shown in  FIG. 1 ) of a driving circuit in a display is generally of two types, a first one using a direct current (DC) source and another one using an alternating current (AC) source. In the case of using AC Vcom, a source driver can reduce its output voltage, therefore a lower operation voltage is used, the low-voltage process is adopted and power consumption is reduced thereby. However, in consideration of applications, a manner of polarity changing in the liquid crystal display can generally be only adopted with a frame inversion manner or a row inversion manner. The method of polarity changing for the frame inversion is shown in  FIG. 2 , and waveform of the Vcom is shown in  FIG. 4  and  FIG. 5 . With reference to a frame  1  of  FIG. 4 , a waveform of Vcom forms polarity, which is all positive in the whole frame, as shown in frame  1  of  FIG. 2 . With reference to frame  2  of  FIG. 5 , a waveform of Vcom forms polarity, which is all negative in the whole frame, as shown in frame  2  of  FIG. 2 . Although it achieves the purpose of reducing power consumption, it also causes problems, such as flicker and crosstalk, which have bad influence to image quality.  
         [0007]     Method of the polarity change of the row inversion is shown in  FIG. 3 , and the corresponding waveform of Vcom is shown in  FIG. 4  and in  FIG. 5 . With reference to frame  1  of  FIG. 4 , a waveform of Vcom forms polarity, which is all positive in odd lines and all negative in even lines, as shown in frame  1  of  FIG. 3 . With reference to frame  2  of  FIG. 5 , a waveform of Vcom forms polarity, which is all negative in odd lines and all positive in even lines, as shown in frame  2  of  FIG. 3 . Although the row inversion partially overcomes shortcomings of the frame inversion, the improvement is occasionally insufficient for images requiring higher quality. The adoption of method of dot inversion polarity change solves problems mentioned above. However, a conventional source driving circuit and its control method cannot complete the function of dot inversion with using the AC Vcom.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention provides a driving method and a data driving circuit of display thereof capable of obtaining a display image by using a dot inversion under a AC Vcom.  
         [0009]     The driving method of the present invention divides a first frame into a first field and a second field, and driving data lines of a first part in the first field and driving data lines of a second part in the second field.  
         [0010]     The data driving circuit of the present invention includes a data processing circuit. The data processing circuit includes a plurality of output terminals, a plurality of multiplexers (MUXs) and a control unit. The data process circuit receives display data and outputs the display data to the output terminals, input terminals of each of the MUXs one-on-one coupled to the output terminals. Each MUX includes a first output terminal and a second output terminal, in which the first output terminal and the second output terminal are coupled to two adjoining data-lines. The control unit provides a control signal to the MUXs to choose from the first output terminal and the second output terminal as the terminal through which the MUXs outputs display data.  
         [0011]     The present invention uses a new driving method and new data driving circuit, in which a frame is divided into two fields, and data lines corresponding to both of the fields are respectively driven to reduce flicker and crosstalk and solves quality problem. The present invention also overcomes the problem that the conventional source driver circuit and control method cannot achieve a driving method of a dot inversion with using AC Vcom. The data driving circuit of the present invention drives the data lines in a half of a display panel in one field time, therefore only half of the conventional driving circuits is required, which reduce necessary circuit and the cost.  
         [0012]     In order to the make the aforementioned and other objects, features and advantages of the present invention comprehensible, a preferred embodiment accompanied with figures is described in detail below.  
         [0013]     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  
       [0014]     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.  
         [0015]      FIG. 1  is a block diagram of a conventional liquid crystal display.  
         [0016]      FIG. 2  shows general polarity change in frame inversion.  
         [0017]      FIG. 3  shows general polarity change in raw inversion.  
         [0018]      FIG. 4  and  FIG. 5  show voltage waveform of Vcom in frame inversion and in raw inversion.  
         [0019]      FIG. 6  shows polarity change in the dot inversion according to the embodiment of the present invention.  
         [0020]      FIG. 7  shows the voltage waveform of Vcom according to the embodiment of the present invention.  
         [0021]      FIG. 8  shows the block diagram of source driver according to the embodiment of the present invention.  
         [0022]      FIG. 9  is a block diagram of a conventional source driver.  
         [0023]      FIG. 10  shows the mux inner block diagram of source driver according to the embodiment of the present invention. 
     
    
     DESCRIPTION OF EMBODIMENTS  
       [0024]     In order to solve problems that conventional source driver circuit and its control method cannot achieve function of dot inversion with using AC Vcom, and to overcome image quality problems such as flicker and crosstalk, the present invention provides a driving method and a data driving circuit different from the conventional ones. In the following, detailed description along with the accompanied drawings is given to better explain preferred embodiments of the present invention.  
         [0025]     As shown in  FIG. 6  and  FIG. 7 , the present invention uses dot inversion polarity change as a control method to accomplish dot inversion under AC Vcom. For explanation, a portion of a data lines and gate lines are shown, but is not limited to. With reference to a voltage waveform of Vcom as shown in  FIG. 7 , a frame  1  is divided into a first field and a second field. With reference to  FIG. 6 , a source driver drives odd data lines such as S 1 , S 3 , S 5 , and S 7  of display as shown in the first field, and a Vcom voltage waveform which changes polarity during every horizontal line as shown in  FIG. 7 . The polarity characteristic  602  between Vcom and image data stored in pixels in the first filed of the first frame is shown in  FIG. 6 . The symbol “+” represents the image data voltage higher than Vcom and the symbol “−” represents image data voltage lower than Vcom.  
         [0026]     The source driver drives even data lines S 2 , S 4 , S 6 , and S 8  of the display in the second field of the first frame, and a Vcom voltage waveform which changes polarity during every horizontal line is shown in  FIG. 7 , which is opposite to Vcom polarity in the first field. The polarity characteristic  604  between Vcom and image data stored in pixels in the second field of the first frame is shown in  FIG. 6 . The first frame has polarity characteristic  606  between Vcom and image data stored in pixels, as shown in  FIG. 6 , after combining the polarity characteristic  602  in the first field and the polarity characteristic  604  in the second field, and the number of thin film transistors (as the thin film transistors  102  as shown  FIG. 1 ) is only half of total thin film transistors in one frame. Then a next frame (the second frame) is also divided into a first field and a second field. A source driver also drives odd data lines S 1 , S 3 , S 5 , and S 7  of display in the first field, and a voltage phase of Vcom of which is opposite to the voltage phase of the Vcom in the first field of the first frame, but is the same as the second field as shown in  FIG. 7 . That means Vcom has polarity opposite to polarity in the first field of the previous frame though it changes polarity during every horizontal line in the same way. The polarity characteristic between Vcom and image data stored in pixels in the first field of the second frame is shown as a reference number  608  in  FIG. 6 . In the second field, the source driver drives even data lines S 2 , S 4 , S 6 , and S 8  of display and changes polarity during every horizontal line, same as the first field as shown in  FIG. 7 , but has opposite voltage phase of Vcom to the Vcom in the second field of the first frame. The polarity characteristic between Vcom and image data stored in pixels in the second frame is shown as a reference number  610  in  FIG. 6 . Then the second frame has polarity characteristic  612  between Vcom and image data stored in pixels, as shown in  FIG. 6 . The number of thin film transistor driven is also half of total thin film transistors in a frame.  
         [0027]      FIG. 8  is a schematic diagram showing a source driver according to one embodiment of the present invention. As shown in  FIG. 8 , the source driver includes a shift register  802 , a latch  804 , a level shifter  806 , a digital to analog converter  808 , an output buffer  810  and n/2 one-to-two type multiplexers (MUXs)  812 , where n represents the number of output terminals S 1 -S(n) of a conventional source driver as shown in  FIG. 1 . It means that the source driver of the embodiment requires only half of the output buffers than the conventional one.  
         [0028]     In the source driver, output terminals of the shift register  802  are coupled to input terminals of the latch  804 , output terminals of the latch  804  are coupled to input terminals of the level shifter  806 , output terminals of the level shifter  806  are coupled to input terminals of the digital to analog converter  808 , output terminals of the digital to analog converter  808  are coupled to input terminals of the output buffer  810 , and output terminals of the output buffer  810  are coupled to input terminals of the one-to-two MUXs  812 .  
         [0029]     While the output buffer  810  outputs buffered signals OP 1 , OP 2  . . . OP(N/2) to the MUXs  812 , the MUXs  812  decide to output the odd output signals to odd-numbered output terminals S 1 ,S 3  . . . S(n-1) or the even-numbered output terminals S 2 ,S 4  . . . S(n) according to a control signal synchronous to a field switching rate to accomplish dot inversion.  
         [0030]      FIG. 9  is a schematic diagram showing the circuit block of a conventional source driver. As shown in  FIG. 9 , the source drivers includes a shift register  902 , a latch  904 , a level shifter  906 , a digital to analog converter  908 , and output buffers  910 . The output buffer  910  has output terminals S 1 , S 2 , . . . , S(n), where n represents a number of total output terminals of the output buffers  910  which are also the same as the output terminals S 1 -S(n) of the conventional source driver shown in  FIG. 1 .  
         [0031]     Output terminals of the shift register  902  are coupled to input terminals of the latch  904 , output terminals of the latch  904  are coupled to input terminals of the level shifter  906 , output terminals of the level shifter  906  are coupled to input terminals of the digital to analog converter  908 , and output terminals of the digital to analog converter  908  are coupled to input terminals of the output buffer  910 . The conventional source driver circuit does not have the control signal synchronous to field switching rate and MUXs which can decide to output the odd output signals S 1 ,S 3  . . . S(n-1) or the even output signals S 2 ,S 4  . . . S(n) according to the control signal, as described in the embodiment of the present invention, therefore the conventional source driver cannot accomplish dot inversion when the output buffer output signals directly.  
         [0032]     An embodiment of a multiplexer in a source driver according to the preferred embodiment of the present invention is shown in  FIG. 10 . As shown in  FIG. 10 , circuits of the source driver includes a control unit  1002 , an inverter  1006 , and n/2 multiplexers  1012 , where n represents the number of outputs required for the source driver. Each of the multiplexer  1012  includes a first switches  1008  and a second switches.  
         [0033]     As shown in  FIG. 10 , each dash line frame represents one switching unit  1012 , and input terminals of the multiplexer  1012 , from OP 1  to OP(n/2) respectively corresponds to output terminals of the output buffer, for example, OP 1  to OP(n/2) as shown in  FIG. 8 . The output terminals of multiplexer  1012 , from S 1  to S(n) also respectively correspond to the output terminals (from S 1  to S(n)) of multiplexers  812  in  FIG. 8 . The multiplexer  1012  includes switches respectively coupled between each input terminal and each output terminal. The control unit  1002  controls a half of the switches in all multiplexer  1012 , for example, odd-numbered output terminals S 1 , S 3  . . . S(n-1). The control unit  1002  also alternately controls the other half of the switches in all multiplexer  1012  through the outputs of the inverter  1006 , for example, the even-numbered output terminals S 2 , S 4  . . . S(n).  
         [0034]     When the control unit  1002  outputs a control signal  1004  synchronous with the field switching rate to the inverter  1006 , each multiplexer  1012  switches odd-numbered output terminal and even-numbered output terminal synchronously with the field switching rate according to the input signal  1004  and output signal  1006  of the inverter  1006 .  
         [0035]     As description above, a new driving method and driving circuit of source driver according to the present invention can reduce flicker and crosstalk of image quality problem. The source driver circuit of the present invention only drives a half data lines in the display panel within one field time, therefore only a half of the driving circuit is required, which reduces necessary circuits.  
         [0036]     It will be apparent to those skilled 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.