Abstract:
In a touch panel having at least one pixel and/or in accordance with a method of controlling the touch panel, a first bias signal is sent to a touch-sensitive sensing capacitor of the pixel during a first time period to charge the sensing capacitor with a sensing charge. The charged sensing capacitor discharges the sensing charge, as an outputted second bias signal, during a second time period. Based on the second bias signal, a determination is made as to whether the capacitance of the sensing capacitor has changed between the first and second periods, thereby indicating whether the pixel of the touch panel has been touched.

Description:
[0001]    This application claims the benefit of Taiwan application Serial No. 96137575, filed Oct. 5, 2007, the entirety of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The disclosure relates to a panel and a control method, and, in particular, to a touch panel and a control method thereof. 
         [0004]    2. Related Art 
         [0005]    With the recent advancement of technology, various information apparatuses have been continuously upgraded. Taking a data input apparatus as an example, inputting the data through a keyboard or a mouse and outputting the data through a display appear to be too slow because the current data processing amount gradually grows with each passing day. 
         [0006]    In addition to the visual sense and the acoustic sense, the human still possesses the tactile sense, so a touch sensor has become another choice for the communication between the human and the information apparatus with the continuous update of the sensor technology. 
         [0007]    On the other hand, the conventional computer input interface, such as the keyboard or the mouse, cannot be easily operated by a user who is not familiar with the computer so that the popularization of the computer is limited. In order to operate the information apparatus more instinctively, the manufacturers have recently developed touch panels. The touch panel has the property of human-oriented input interface so that the user with any age can directly select the functional options on the touch panel with his/her finger or a touch pen (stylus). 
         [0008]    In a conventional touch panel, a touch film (an outer film) is added onto the conventional display panel to sense the touched position. However, this configuration increases material costs and decreases the brightness of the panel. 
         [0009]    Recently, the manufacturers have developed an in-cell touch panel having a photonic transistor, which is manufactured in the panel by the thin film transistor manufacturing process, for sensing the touched position. The principle of such in-cell touch panel is that different signals are generated when the photonic transistor is illuminated or is not illuminated by light. Thus, a rear end control unit can obtain the position touched by the user. 
         [0010]    However, when the touch panel is placed in an environment with a flickering external light source or a weak external light source, the touch panel may be malfunctioned. In addition, the lifespan of the photonic transistor is also restricted due to the action of light. 
         [0011]    Therefore, it is important to provide a touch panel and a control method thereof, which can be free from interferences caused by external light rays and have a lengthened service life. 
       SUMMARY 
       [0012]    In an embodiment, the invention discloses a touch panel, comprising: a controller; at least one pixel and a sense reading unit. The pixel comprises a touch choosing switch coupled to and controlled by the controller to turn on during a first time period and turn off during a second time period; a read switch coupled to and controlled by the controller to turn off during the first time period and turn on during the second time period; and a sensing capacitor having a touch-sensitive capacitance and being electrically connected with the touch choosing switch and the read switch to be charged, via the touch choosing switch, with a sensing charge during the first time period and to discharge the sensing charge, via the read switch during the second time period. The sense reading unit is electrically connected with the sensing capacitor via the read switch for outputting a sensed output value during the second time period. The sensed output value is indicative of the whether the capacitance of the sensing capacitor has changed between the first and second periods, thereby indicating whether said pixel of the touch panel has been touched. 
         [0013]    In another embodiment, the invention also discloses a touch panel comprising at least one pixel having a first scan line, a second scan line, and a bias line. The pixel further comprises a touch choosing switch, a read switch, and a sensing capacitor having a touch-sensitive capacitance. The touch choosing switch is electrically connected with the first scan line and the bias line. The read switch is electrically connected with the second scan line. The sensing capacitor is electrically connected with both the touch choosing switch and the read switch, for receiving a first bias signal from the bias line through the touch choosing switch during a first period and for outputting a second bias signal through the read switch during a second period different from the first period. The second bias signal is indicative of the whether the capacitance of the sensing capacitor has changed between the first and second periods, thereby indicating whether said pixel of the touch panel has been touched. 
         [0014]    In a further embodiment, the invention further discloses a control method of a touch panel having at least one pixel that comprises a sensing capacitor having a touch-sensitive capacitance. The control method comprises transmitting a first bias signal to the sensing capacitor during a first time period to charge the sensing capacitor with a sensing charge; causing the sensing capacitor to discharge the sensing charge as an outputted second bias signal during a second time period different from the first time period; and based on the second bias signal, determining whether the capacitance of the sensing capacitor has changed between the first and second periods, thereby indicating whether said pixel of the touch panel has been touched. 
         [0015]    Additional aspects and advantages of the disclosed embodiments are set forth in part in the description which follows, and in part are apparent from the description, or may be learned by practice of the disclosed embodiments. The aspects and advantages of the disclosed embodiments may also be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    Embodiments of the invention will become more fully understood from the detailed description and accompanying drawings, which are given for illustration only, and thus are not limitative of the present invention, and wherein: 
           [0017]      FIG. 1  is a schematic illustration showing a touch panel according to a first embodiment of the invention; 
           [0018]      FIG. 2  is a schematic illustration showing a pixel according to the first embodiment of the invention; 
           [0019]      FIG. 3  is a schematic illustration showing a control method of the touch panel according to the first embodiment of the invention; 
           [0020]      FIG. 4  is a schematic illustration showing a timing control of the touch panel according to the first embodiment of the invention; 
           [0021]      FIGS. 5A and 5B  are schematic illustrations showing alternative structures of a sensing capacitor of the touch panel according to the first embodiment of the invention; 
           [0022]      FIG. 6  is a schematic illustration showing a touch panel according to a second embodiment of the invention; 
           [0023]      FIG. 7  is a schematic illustration showing a pixel according to the second embodiment of the invention; 
           [0024]      FIG. 8  is a schematic illustration showing a control method of the touch panel according to the second embodiment of the invention; 
           [0025]      FIG. 9  is a schematic illustration showing a timing control of the touch panel according to the second embodiment of the invention; and 
           [0026]      FIGS. 10 and 11  show connections between a liquid crystal capacitor and a storage capacitor of the touch panel. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0027]    Embodiments of the present invention will be apparent from the following detailed description, with reference to the accompanying drawings, wherein the same references relate to the same elements. 
       First Embodiment 
       [0028]    Referring to  FIG. 1 , a touch panel  1  according to a first embodiment of the invention includes a plurality of pixels  2 , a data control circuit  11 , a scan control circuit  12  and a touch control circuit  13 . The data control circuit  11  is electrically connected with the corresponding pixels  2  through a plurality of data lines D 11  to D m1 , and the scan control circuit  12  is electrically connected with the corresponding pixels  2  through a plurality of scan lines S 11  to S n2 , wherein m and n are positive integers. 
         [0029]    The touch control circuit  13  includes a plurality of sense reading units  131  and a position judging unit  132 . The position judging unit  132  is electrically connected with the sense reading units  131 , and the sense reading units  131  are electrically connected with the corresponding pixels  2  through a plurality of read lines R 1  to R m . 
         [0030]    The pixels  2  are arranged on the touch panel in an array. Referring to  FIG. 2 , the pixel  2  according to the first embodiment of the invention includes a pixel unit  21  and a touch unit  22 . 
         [0031]    The pixel unit  21  has a pixel switch T 11  and a pixel sensing capacitor C 11 . The pixel switch T 11  is electrically connected with the first scan line S 11 , the data line D 11  and the pixel sensing capacitor C 11 . In practice, the pixel sensing capacitor C 11  includes a liquid crystal capacitor C LC1  and a storage capacitor C ST1  electrically connected with each other. The storage capacitor C ST1  is electrically connected with and between the pixel switch T 11  and a bias line B 11 , and the liquid crystal capacitor C LC1  is electrically connected with and between the pixel switch T 11  and a common electrode V com . 
         [0032]    The touch unit  22  has a touch choosing switch T 12 , a read switch T 13  and a sensing capacitor C 12 . The touch choosing switch T 12  is electrically connected with the second scan line S 12  and the bias line B 11 . To be noted, the voltage applied to a bias line may be a DC or AC voltage. The sensing capacitor C 12  is electrically connected with the touch choosing switch T 12  and the read switch T 13 . The sensing capacitor C 12  includes a liquid crystal capacitor C LC2  and a varactor C T . 
         [0033]    As shown in  FIG. 2 , the sense reading unit  131  is electrically connected with the read switch T 13 . In practice, the sense reading unit  131  may be an integrator. In addition, the sense reading unit  131  may be disposed in the pixel  2  or the touch control circuit  13 . In this illustrated embodiment, the sense reading unit  131  is integrated with the touch control circuit  13 , for example. 
         [0034]    In this embodiment, the sense reading unit  131  includes an operational amplifier OP, an operational capacitor C fb  and a switch L. The operational amplifier OP has a positive input terminal, a negative input terminal and an output terminal. The operational capacitor C fb  is electrically connected with and between the negative input terminal and the output terminal of the operational amplifier, and the switch L is connected with the operational capacitor C fb  in parallel. 
         [0035]    Referring again to  FIG. 3 , a control method of the touch panel according to the first embodiment of the invention includes steps W 01  to W 03 . 
         [0036]    Illustrations will be made with reference to  FIGS. 3 and 4 . In the step W 01 , a first bias signal is transmitted to the sensing capacitor C 12  during a first time period T 01 . In this embodiment, a second scan signal (S 12  in  FIG. 4 ) is transmitted from the scan control circuit  12  through the second scan line S 12  so that the touch choosing switch T 12  turns on, and then the first bias signal is transmitted from the scan control circuit  12  to the sensing capacitor C 12  through the bias line B 11  and the touch choosing switch T 12 . The read switch T 13  remains turned off during the first time period T 01 . Thus, the sensing capacitor C 12  is charged by the first bias signal. 
         [0037]    In addition, it is to be noted that the operational capacitor C fb  stores the charges outputted from the previous scan during the first time period T 01 . Therefore, the switch L is controlled to be closed by a switching signal (S L  in  FIG. 4 ) transmitted (by a control circuit, for example, data control circuit  11  or scan control circuit  12 ) through a switch signal line S L  so that the operational capacitor C fb  discharges to reset the state of the operational capacitor C fb . 
         [0038]    In the steps W 02  and W 03 , the sensing capacitor C 12  outputs a second bias signal V b  to the sense reading unit  131  via read line R 1 , and an image data signal is transmitted to the pixel sensing capacitor C 11  during a second time period T 02  which is the displaying period. In this embodiment, during the second time period T 02 , the second scan signal is removed from the second scan line S 12  so that the touch choosing switch T 12  turns off. A first scan signal (S 11  in  FIG. 4 ) is transmitted from the scan control circuit  12  through the first scan line S 11  so that the pixel switch T 11  turns on. When the pixel switch T 11  turns on, image data is transmitted from the data control circuit  11  to the liquid crystal capacitor C LC1  through the data line D 11  and the pixel switch T 11 . The first scan signal on the first scan line S 11  also turns on the read switch T 13  so that the sensing capacitor C 12  discharges and outputs the second bias signal V b  to the sense reading unit  131  through the read switch T 13  and read line R 1 . 
         [0039]    The negative input terminal of the operational amplifier OP of the sense reading unit  131  receives the second bias signal V b , and the positive input terminal of the operational amplifier OP of the sense reading unit  131  receives a reference signal V ref . The operational amplifier OP outputs a sensed output value V o  according to the second bias signal V b  and the reference signal V ref , wherein the sensed output value V o  is represented by: 
         [0000]    
       
         
           
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         [0040]    The position judging unit  132  judges which pixel  2  is touched according to the sensed output value V o  outputted from the respective sense reading unit  131  and a timing signal of the scan line. 
         [0041]    In addition, the first bias signal is the same as the second bias signal V b  in this embodiment when the capacitance of the sensing capacitor C 12  is unchanged during the time periods T 01  and T 02 , i.e., when the respective pixel of the touch panel  1  is not applied with an external force. Correspondingly, if the touch panel  1  is applied with the external force, the first bias signal is different from the second bias signal V b . Herein, the so-called external force represents the external force capable of changing the capacitance of the sensing capacitor C 12 . For example, the force may be applied to change the gap of the sensing capacitor C 12 , or the touch of the human body may change the capacitance of a varactor C T . 
         [0042]    In practice, the sensing capacitor C 12  may have various structures as exemplarily shown in  FIGS. 5A and 5B . The touch panel  1  includes a transistor substrate  24 , a color filtering substrate  25 , a pixel electrode  26  and a common electrode V com . The sensing capacitor C 12  is formed at the position shown in the drawing. As shown in  FIG. 5A , when the user applies an external force F to the touch panel  1 , the capacitance of the sensing capacitor C 12  is changed by a value equal to the capacitance variation of the varactor C T  only, because liquid crystal capacitor C LC2  is not provided in the structure of  FIG. 5A . As shown in  FIG. 5B , when the user applies an external force F to the touch panel  1 , the capacitance of the sensing capacitor C 12  is changed by a value equal to a sum of the capacitance variations of both the liquid crystal capacitor C LC2  and the varactor C T . 
         [0043]    Although not shown in  FIGS. 5A and 5B , an alternative structure of the sensing capacitor C 12  can also be used in this embodiment when the common electrode V com  and the transistor substrate  24  have the same structure size, i.e., the varactor C T  cannot function for the judgment of the touched position. In this alternative structure, only the liquid crystal capacitor C LC2  can function for the judgment of the touched position. That is, the sensing capacitor C 12  cannot become effective until a force F is applied. When the common electrode V com  has a discontinuous structure, as shown in  FIG. 5A  or  5 B, both the liquid crystal capacitor C LC2  and the varactor C T  ( FIG. 5B ) or only the varactor C T  ( FIG. 5A ) may function for the judgment of the touched position. 
       Second Embodiment 
       [0044]    The touch panel and the control method thereof according to a second embodiment of the invention will be described in the following section. Referring to  FIG. 6 , a touch panel  3  according to the second embodiment of the invention includes a plurality of pixels  4 , a data control circuit  11 , a scan control circuit  12  and a touch control circuit  13 . 
         [0045]    Referring to  FIG. 7 , the pixel  4  according to the second embodiment of the invention includes a pixel switch T 21 , a touch choosing switch T 22  and a pixel/sensing capacitor C 21 . The pixel switch T 21  is electrically connected with a first scan line S 21  and a data and bias line DB 11 . The pixel/sensing capacitor C 21  is electrically connected with the pixel switch T 21 , and the touch choosing switch T 22 . In practice, the pixel/sensing capacitor C 21  includes a liquid crystal capacitor C LC2  and a storage capacitor C ST2  electrically connected with each other. 
         [0046]    In this embodiment, the touch panel  3  further includes a sense reading unit  131 , which is the same as that of the first embodiment, and a negative input terminal of an operational amplifier OP is electrically connected with the touch choosing switch T 22 . 
         [0047]    Referring further to  FIG. 8 , the control method of the touch panel according to the second embodiment of the invention includes steps W 11  to W 13 . 
         [0048]    Illustrations will be made with reference to  FIGS. 8 and 9 . In the step W 11 , a first scan signal (S 21  in  FIG. 9 ) is transmitted from the scan control circuit  12  through the first scan line S 21  during a first time period T 11  so that the pixel switch T 21  turns on. At this time, a first bias signal is transmitted from the data control circuit  11  to the pixel/sensing capacitor C 21  through the pixel switch T 21 , and the data and bias line DB 11 . The touch choosing switch T 22  remains turned off during the first time period T 01 . Thus, the pixel/sensing capacitor C 12  is charged by the first bias signal. 
         [0049]    In the step W 12 , a second scan signal (S 22  in  FIG. 9 ) is transmitted from the scan control circuit  12  through the second scan line S 22  during a second time period T 12  so that the touch choosing switch T 22  turns on. During the second time period T 12 , the first scan signal is removed from the first scan line S 21  so that the pixel switch T 21  turns off. As the touch choosing switch T 22  turns on, the pixel/sensing capacitor C 21  discharges and outputs a second bias signal V b , which is transmitted to the negative input terminal of the operational amplifier OP of the sense reading unit  131  through the touch choosing switch T 22 . If the pixel sensing capacitor C 21  is not applied with an external force, the first bias signal is the same as the second bias signal V b . One of ordinary skill in the art may easily understand the operation condition of the sense reading unit  131  according to the illustration made in the first embodiment, so detailed descriptions thereof will be omitted. 
         [0050]    In the step W 13 , an image data signal is transmitted from the data control circuit  11  during a third time period T 13  which is the displaying period. Herein, the first scan signal (S 21  in  FIG. 9 ) is again transmitted through the first scan line S 21  so that the pixel switch T 21  turns on, and the image data signal is transmitted to the pixel/sensing capacitor C 21  through the data and bias line DB 11  and the pixel switch T 21 . As shown in  FIG. 9 , during the time periods T 11  and T 13 , the switching signal (S L  in  FIG. 9 ) is transmitted (by a control circuit, for example, data control circuit  11  or scan control circuit  12 ) so as to reset the state of the operational capacitor C fb  similarly to the first embodiment. 
         [0051]    In addition, this embodiment does not intend to restrict the connection between the liquid crystal capacitor C LC2  and the storage capacitor C ST2  to be within the pixel/sensing capacitor C 21 . In addition to the parallel connection of  FIG. 7 , the liquid crystal capacitor C LC2  and the storage capacitor C ST2  may also be connected in series, as shown in  FIG. 10 , or may be connected in a manner as shown in  FIG. 11 . 
         [0052]    In summary, in the touch panel and the control method thereof according to embodiments of the invention, when an external force is applied to or a human body contacts (conductor contact) with the sensing capacitor or the pixel/sensing capacitor of a pixel, the capacitance thereof is changed so that a determination as to whether the touch panel is touched and/or the touched position can be made. Compared with the prior art, a photonic transistor is not used in the touch panel of embodiments of the invention to sense the touched position. Therefore, embodiments of the invention are free from the interferences of external light sources. Further, the service life of the touch panel in accordance with the disclosed embodiments is improved as the lifespan of the disclosed transistor is also longer than that of the conventional photonic transistor. 
         [0053]    Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments, will be apparent to persons skilled in the art. It is, therefore, contemplated that the appended claims will cover all modifications that fall within the true scope of the invention.