Abstract:
An exemplary driving circuit ( 20 ) includes: gate lines ( 23 ); data lines ( 24 ); pixel units ( 240 ); a gate driving circuit ( 21 ); a data driving circuit ( 22 ); a signal output circuit configured for providing a set of signals in each frame, each signal in the set of signals selectively being a black signal or a white signal; and a select output circuit ( 26 ) configured for receiving the data signals from the data driving circuit and the set of signals from the signal output circuit. When a signal of the set of signals provided by the signal output circuit is a black signal, the select output circuit provides the black signal to a corresponding data line. When a signal of the set of signals provided by the signal output circuit is a white signal, the select output circuit provides a corresponding one of the data signals to the corresponding data line.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to driving circuits of liquid crystal displays (LCDs), and particularly to a driving circuit which includes a signal output circuit for alternately outputting black or white signals and inverse black or white signals in every frame. 
       GENERAL BACKGROUND 
       [0002]    A typical LCD has the advantages of portability, low power consumption, and low radiation. The LCD has been widely used in various portable information products such as notebooks, personal digital assistants (PDAs), video cameras, and the like. Furthermore, the LCD is considered by many to have the potential to completely replace CRT (cathode ray tube) monitors and televisions. An LCD generally includes a liquid crystal panel, a driving circuit for driving the liquid crystal panel, and a backlight module for illuminating the liquid crystal panel. 
         [0003]      FIG. 8  is essentially an abbreviated circuit diagram of a typical driving circuit  10  of an LCD. The driving circuit  10  includes a number n (where n is a natural number) of gate lines  13  that are parallel to each other and that each extend along a first direction, a number m (where m is also a natural number) of data lines  14  that are parallel to each other and that each extend along a second direction orthogonal to the first direction, a plurality of thin film transistors (TFTs)  15  that function as switching elements, a plurality of pixel electrodes  16 , a gate driving circuit  11 , and a data driving circuit  12 . The plurality of gate lines  13  and the plurality of data lines  14  cross each other, thereby defining an array of pixel units of the LCD. The gate driving circuit  11  is configured to provide scanning signals to the gate lines  13 . The data driving circuit  12  is configured to provide data signals to the data lines  14 . 
         [0004]    Each TFT  15  is provided in the vicinity of a respective point of intersection of the gate lines  13  and the data lines  14 . A gate electrode, a source electrode, and a drain electrode of the TFT  15  are connected to a corresponding gate line  13 , a corresponding data line  14 , and a corresponding pixel electrode  16  respectively. 
         [0005]    Referring also to  FIG. 9 , this is a waveform diagram of driving signals of the driving circuit  10 . G 1 -G n  show waveforms of scanning signals generated by the gate driving circuit  11 . V d  shows a waveform of data signals generated by the data driving circuit  12 . A driving method of the driving circuit  10  is as follows: 
         [0006]    During a first frame, the gate driving circuit  11  generates a plurality of scanning signals  19 , and applies the scanning signals  19  to the gate lines  13 . The scanning signals  19  are high voltage signals. When one of the gate lines  13  has a scanning signal  19  applied thereto, the corresponding row of TFTs  15  are switched on by the high voltage. At the same time, the data driving circuit  12  applies a plurality of data signals Vd (which represent pixel data PD of the first frame) to the pixel electrodes  16  via the data lines  14  and the row of activated TFTs  15 . Before a scanning signal  19 ′ of a second frame next to the first frame is applied to the gate line  13 , the pixel data PD displayed on the row of pixel units remains the same. When the scanning signal  19 ′ of the second frame is applied to the gate line  13 , the row of TFTs  15  are switched on again by the high voltage. At the same time, the data driving circuit  12  applies a plurality of data signals Vd′ (which represent pixel data PD′ of the second frame) to the pixel electrodes  16  via the data lines  14  and the row of activated TFTs  15 . Thereby, the row of pixel units display the pixel data PD′ of the second frame. 
         [0007]    However, because a response speed of liquid crystal molecules at the pixel electrodes  16  of the LCD is low, a residual image phenomenon may occur. In particular, when the data signals are changed from Vd to Vd′, the liquid crystal molecules may be unable to track the variation within a single frame period, and instead produce a cumulative response during several frame periods. 
         [0008]    What is needed, therefore, is a driving circuit and a driving method of an LCD that can overcome the above-described deficiencies. What is also needed is an LCD using such a driving circuit. 
       SUMMARY 
       [0009]    In one preferred embodiment, a driving circuit includes: a plurality of substantially parallel gate lines; a plurality of substantially parallel data lines crossing the gate lines thereby defining a plurality of pixel units; a gate driving circuit configured for providing scanning signals to the gate lines; a data driving circuit configured for providing data signals; a signal output circuit configured for providing a set of signals in each frame, each signal in the set of signals selectively being a black signal or a white signal; and a select output circuit configured for receiving the data signals from the data driving circuit and the set of signals from the signal output circuit. When a signal of the set of signals provided by the signal output circuit is a black signal, the select output circuit provides the black signal to a corresponding one of the data lines. When a signal of the set of signals provided by the signal output circuit is a white signal, the select output circuit provides a corresponding one of the data signals to the corresponding data line. Over the duration of two adjacent frames, each pixel unit displays both a black image corresponding to the black signal and a normal image corresponding to the white signal, in a sequence according to the corresponding selected signal of the set of signals for each of the two adjacent frames. 
         [0010]    Other novel features and advantages will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. In the drawings, all the views are schematic. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is side, cross-sectional view of an LCD according to a first embodiment of the present invention, the LCD including a driving circuit (not shown). 
           [0012]      FIG. 2  is essentially an abbreviated circuit diagram of the driving circuit of the LCD of the first embodiment, the driving circuit including a register. 
           [0013]      FIG. 3  is an abbreviated view of a black-and-white image, which is stored in the form of data in the register of the driving circuit of  FIG. 2 . 
           [0014]      FIG. 4  is an abbreviated waveform diagram of driving signals of the driving circuit of  FIG. 2 . 
           [0015]      FIG. 5  is an abbreviated view of a black-and-white image, which is stored in the form of data in a register of a driving circuit of an LCD according to a second embodiment of the present invention. 
           [0016]      FIG. 6  is an abbreviated view of a black-and-white image, which is stored in the form of data in a register of a driving circuit of an LCD according to a third embodiment of the present invention. 
           [0017]      FIG. 7  is an abbreviated view of a black-and-white image, which is stored in the form of data in a register of a driving circuit of an LCD according to a fourth embodiment of the present invention. 
           [0018]      FIG. 8  is essentially an abbreviated circuit diagram of a conventional driving circuit of an LCD. 
           [0019]      FIG. 9  is an abbreviated waveform diagram of driving signals of the driving circuit of  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0020]    Referring to  FIG. 1 , an LCD  2  according to a first embodiment of the present invention is shown. The LCD  2  includes a first substrate  201 , a second substrate  202 , a liquid crystal layer  203  sandwiched between the first substrate  201  and the second substrate  202 , and a driving circuit (not shown). 
         [0021]    Referring to  FIG. 2 , the driving circuit  20  includes a number n (where n is a natural number) of gate lines  23  that are parallel to each other and that each extend along a first direction, a number m (where m is an even natural number) of data lines  24  that are parallel to each other and that each extend along a second direction orthogonal to the first direction, a plurality of thin film transistors (TFTs)  230  that function as switching elements, a plurality of pixel electrodes  231 , a gate driving circuit  21 , a data driving circuit  22 , a signal output circuit (not labeled), and a select output circuit  26 . The plurality of gate lines  23  and the plurality of data lines  24  cross each other, thereby defining an array of pixel units  240  of the LCD  2 . The gate driving circuit  21  is configured to provide scanning signals to the gate lines  23 . The data driving circuit  22  includes the number m of signal output terminals  221 , which are configured to output data signals. 
         [0022]    Each TFT  230  is provided in the vicinity of a respective point of intersection of the gate lines  23  and the data lines  24 . A gate electrode, a source electrode, and a drain electrode of each TFT  231  are connected to a corresponding gate line  23 , a corresponding data line  24 , and a corresponding pixel electrode  231  respectively. 
         [0023]    The signal output circuit includes a register  25 , the number m of switches  27 , and the number m of inverters  28 . The register  25  is configured to store a black-and-white image in the form of data in advance, and read black or white signals corresponding to the pixel units  240  from the black-and-white image data. The inverters  28  are configured to convert the black signals into white signals or convert the white signals into black signals. 
         [0024]    The select output circuit  26  includes the number m of select output units  260 . Each select output unit  260  includes a first input terminal  261 , a second input terminal  262 , and a select output terminal  263 . The first input terminal  261  is configured to receive data signals from a corresponding signal output terminal  221  of the data driving circuit  22 . The second input terminal  262  is configured to receive black and white signals from a corresponding signal output terminal (not labeled) of the register  25 , or black and white signals inverted by a corresponding inverter  28 . The select output terminal  263  is configured to output a data signal or a black signal to a corresponding data line  24 . By controlling a corresponding switch  27 , the corresponding signal output terminal of the register  25  can directly provide a black or white signal to the second input terminal  262 , or provide a black or white signal inverted by the corresponding inverter  28  to the second input terminal  262 . 
         [0025]    Referring to  FIG. 3 , this shows the visual form of the black-and-white image that is stored in the register  25  in the form of data. The black-and-white image includes a plurality of rectangular regions corresponding to the pixel units  240  of the LCD  20 . Odd-column rectangular regions are black, and even-column rectangular regions are white. That is, the odd-column rectangular regions correspond to black signals, and the even-column rectangular regions correspond to white signals. 
         [0026]    Referring to  FIG. 4 , this is a waveform diagram of driving signals of the driving circuit  20 . G 1 -G n  show waveforms of scanning signals generated by the gate driving circuit  21 . V d1 -V dm  show waveforms of data signals generated by the data driving circuit  22 . V b1 -V bm  show waveforms of the black and white signals as applied to the select output circuit  26 . An exemplary driving method of the driving circuit  20  is as follows: 
         [0027]    During a first frame, the gate driving circuit  21  generates a plurality of scanning signals  29 , and applies the scanning signals  29  to the gate lines  23 . The scanning signals  29  are high voltage signals. When one of the gate lines  23  has a scanning signal  29  applied thereto, the corresponding row of TFTs  230  are switched on by the high voltage. 
         [0028]    At the same time, the signal output terminals  221  of the data driving circuit  22  output a plurality of data signals V d1 -V dm  of the first frame to the first input terminals  261  of the select output units  260  respectively, and the register  25  outputs a plurality of black and white signals V b1 -V bm  directly to the second input terminals  262  of the select output units  260  respectively. Odd-column second output terminals  262  receive black signals, and accordingly odd-column select output terminals  263  output the black signals to odd-column data lines  24  respectively. The black signals are applied to odd-column pixel units  240  via the odd-column data lines  24  and odd-column activated TFTs  230 . Even-column second input terminals  262  receive white signals, and accordingly even-column select output terminals  263  output the data signals to even-column data lines  24  respectively. The data signals are applied to even-column pixel units  240  via the even-column data lines  24  and even-column activated TFTs  230 . Thus, in the first frame, the odd-column pixel units  240  of the LCD  2  display black images, and the even-column pixel units  240  of the LCD  2  display normal images. 
         [0029]    During a second frame, the gate driving circuit  21  generates a plurality of scanning signals  29 ′, and applies the scanning signals  29 ′ to the gate lines  23  respectively. The scanning signals  29 ′ are high voltage signals. When one of the gate lines  23  has a scanning signal  29 ′ applied thereto, the corresponding row of TFTs  230  are switched on by the high voltage. 
         [0030]    At the same time, the signal output terminals  221  of the data driving circuit  22  output the plurality of data signals V d1 -V dm  of the first frame to the first input terminals  261  of the select output units  260 , and the register  25  outputs the plurality of black and white signals V b1 -V bm  of the first frame. However, the switches  27  are switched such that the black and white signals V b1 -V bm  are inverted by the inverters  28 , whereupon the inverted black and white signals V b1 -V bm  are input to the second input terminals  262  of the select output units  260 . The odd-column second output terminals  262  receive white signals, and accordingly the odd-column select output terminals  263  output the data signals to the odd-column data lines  24  respectively. The data signals are applied to the odd-column pixel units  240  via the odd-column data lines  24  and the odd-column activated TFTs  230 . The even-column second input terminals  262  receive black signals, and accordingly the even-column select output terminals  263  output the black signals to the even-column data lines  24  respectively. The black signals are applied to the even-column pixel units  240  via the even-column data lines  24  and the even-column activated TFTs  230 . Thus, in the second frame, the odd-column pixel units  240  of the LCD  2  display normal images, and the even-column pixel units  240  of the LCD  2  display black images. The normal images displayed by the even-column pixel units  240  in the first frame and the normal images displayed by the odd-column pixel units  240  in the second frame are mixed as perceived by a viewer of the LCD  2 , whereby a desired whole image is viewed from the standpoint of the viewer. 
         [0031]    In the two next frames, the above steps are repeated. 
         [0032]    In summary, the register  25 , the switches  27 , and the inverters  28  cooperatively form a signal output circuit. The signal output circuit outputs black and white signals alternately arranged by column to the select output circuit  26  in the first frame, and outputs black and white signals with an inverse arrangement in the second frame. Thus, each pixel unit  240  alternately displays normal images and black images every frame. The normal images displayed by the pixel units  240  in every two adjacent frames are mixed as perceived by the human eye, whereby a desired complete image is perceived by the viewer of the LCD  2 . Because two different consecutive normal images displayed by each pixel unit  240  are always spaced by a black image, a residual image phenomenon can be avoided. 
         [0033]    In an alternative embodiment, the register  25  stores an all-black image in the form of data. In such an embodiment, an exemplary driving method of the LCD  2  is as follows: 
         [0034]    During a first frame, the gate driving circuit  21  generates a plurality of scanning signals  29 , and applies the scanning signals  29  to the gate lines  23 . The scanning signals  29  are high voltage signals. When one of the gate lines  23  has a scanning signal  29  applied thereto, the corresponding row of TFTs  230  are switched on by the high voltage. 
         [0035]    At the same time, the signal output terminals  221  of the data driving circuit  22  output a plurality of data signals V d1 -V dm  to the first input terminals  261  of the select output units  260 , and the register  25  outputs a plurality of black signals directly to the second input terminals  262  of the select output units  260 . The select output terminals  263  output the black signals to the pixel units  240  via the data lines  24  and the activated TFTs  230 . Thus, in the first frame, the LCD  2  displays an all-black image. 
         [0036]    During a second frame, the gate driving circuit  21  generates a plurality of scanning signals  29 ′, and applies the scanning signals  29 ′ to the gate lines  23 . The scanning signals  29 ′ are high voltage signals. When one of the gate lines  23  has a scanning signal  29 ′ applied thereto, the corresponding row of TFTs  230  are switched on by the high voltage. 
         [0037]    At the same time, the signal output terminals  221  of the data driving circuit  22  output the plurality of data signals V d1 -V dm  of the first frame to the first input terminals  261  of the select output units  260 , and the register  25  outputs the plurality of black signals. However, the switches  27  are switched such that the black signals are inverted to white signals by the inverters  28 , whereupon the white signals are input to the second input terminals  262  of the select output units  260 . Accordingly, the select output terminals  263  output the data signals to the pixel units  240  via the data lines  24  and the activated TFTs  230 . Thus, in the second frame, the LCD  2  displays a normal image. 
         [0038]    In two next frames, the above steps are repeated. Because two different consecutive normal images displayed by the pixel units  240  are always spaced by an all-black image, a residual image phenomenon can be avoided. 
         [0039]    Referring to  FIG. 5 , this shows the visual form of a black-and-white image that is stored in the form of data in a register of a driving circuit of an LCD according to a second embodiment of the present invention. The black-and-white image includes a plurality of rectangular regions. Odd-column rectangular regions are white, and even-column rectangular regions are black. That is, the odd-column rectangular regions correspond to white signals, and the even-column rectangular regions correspond to black signals. 
         [0040]    Referring to  FIG. 6 , this shows the visual form of a black-and-white image that is stored in the form of data in a register of a driving circuit of an LCD according to a third embodiment of the present invention. The black-and-white image includes a plurality of rectangular regions. Odd-row rectangular regions are black, and even-row rectangular regions are white. That is, the odd-row rectangular regions correspond to black signals, and the even-row rectangular regions correspond to white signals. 
         [0041]    Referring to  FIG. 7 , this shows the visual form of a black-and-white image that is stored in the form of data in a register of a driving circuit of an LCD according to a fourth embodiment of the present invention. The black-and-white image includes a plurality of rectangular regions. Odd-row rectangular regions are white, and even-row rectangular regions are black. That is, the odd-row rectangular regions correspond to white signals, and the even-row rectangular regions correspond to black signals. 
         [0042]    It is to be further understood that even though numerous characteristics and advantages of the present embodiments have been set out in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.