Patent Publication Number: US-2013234989-A1

Title: Touch panel with discharging function

Description:
REFERENCE TO RELATED APPLICATION 
     This Patent Application is being filed as a Divisional application of Ser. No. 12/817,521, filed on 17 Jun. 2010, currently pending. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to a touch panel, and particularly to a touch panel with a discharging function. 
     BACKGROUND OF THE INVENTION 
     Recently, various electronic products are developed in the trend of easier operations, small volume, and large displays. In particular, portable electronic products are demanding severely in volume and display size. Thereby, many electronic products integrate touch panels and liquid-crystal displays for saving the space required by keyboards or operational keys, and hence expanding the area available for displays. 
     Currently, touch panels can be categorized into resistive, capacitive, infrared, and ultrasonic touch panels, and the resistive and capacitive panels are most popular. For capacitive touch panels, the feature of multi-point control provides more friendly operation modes, and thus is gradually favorable in the market. However, capacitive touch panels can only be operated by touching the panel with conductive materials. Thereby, users cannot operate them in gloves or using nonconductive materials. 
     On the other hand, resistive touch panels are operable no matter what material is used by a user to touch the touch panels, and hence enhancing their convenience. Besides, their costs are relatively lower, and their technologies are developed more maturely. Thereby, their market share is higher. 
       FIG. 1  shows a structural schematic diagram of a touch panel according to the prior art. As shown in the figure, the touch panel comprises a scanning bus  10 ′, a sensing bus  20 ′, and a control unit  30 ′. The scanning bus  10 ′ is used for scanning a touch frame. The sensing bus  20 ′ interleaves with the scanning bus  10 ′, and senses at least a touched location on the touch frame. The control unit  30 ′ is coupled to the scanning bus  10 ′ and the sensing bus  20 ′ for controlling them and knowing that at least a location on the touch frame is touched. No matter for capacitive or resistive touch panels, particularly for multi-point applications, the grid structure is generally used for achieving the multi-point effect. The sensing parts at the grids are formed by transparent conductive films. Hence, there exist parasitic capacitance effects at the locations where two layers of transparent conductive films overlap. Thereby, at the scanning transient, the signal on the scanning bus  10 ′ will interfere the signal on the sensing bus  20 ′ owing to the coupling effect between the parasitic capacitors in the touch panel. Consequently, when the system measures, erroneous judgment for the signals occurs, reducing drastically the accuracy. 
     Accordingly, the present invention provides a novel touch panel with a discharging function, which can avoid the parasitic capacitance effect, which results in erroneous judgment for signals. Hence, the accuracy is increased significantly, and the problem described is solved. 
     SUMMARY 
     An objective of the present invention is to provide a touch with a discharging function, which uses a discharging circuit for releasing charges on the parasitic capacitor and avoiding parasitic capacitance effect. Hence, the sensing accuracy of the touch panel is increased. 
     The touch panel with a discharging function according to the present invention comprises a scanning bus, a sensing bus, a control unit, and a discharging circuit. The scanning bus is used for scanning a touch frame. The sensing bus interleaves with the scanning bus, and senses at least a touched location on the touch frame. The control unit is coupled to the scanning bus and the sensing bus  20 ′ for controlling them. The discharging circuit is coupled to the sensing bus or/and the scanning bus, and is controlled by the control unit for releasing the charges at the touched location or/and on the relevant path between the touched location and the buses. Thereby, by using a discharging circuit for releasing charges on the parasitic capacitor, the parasitic capacitance effect is avoided. Hence, the sensing accuracy of the touch panel is increased. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a structural schematic diagram of a touch panel according to the prior art; 
         FIG. 2  shows a structural schematic diagram according to a preferred embodiment of the present invention; 
         FIG. 3  shows a structural schematic diagram according to another preferred embodiment of the present invention; 
         FIG. 4  shows a structural schematic diagram according to another preferred embodiment of the present invention; 
         FIG. 5  shows a structural schematic diagram according to another preferred embodiment of the present invention; 
         FIG. 6  shows a structural schematic diagram according to another preferred embodiment of the present invention; 
         FIG. 7  shows a discharge timing diagram according to a preferred embodiment of the present invention; 
         FIG. 8A  shows a schematic diagram of discharging according to a preferred embodiment of the present invention; 
         FIG. 8B  shows a schematic diagram of discharging according to a preferred embodiment of the present invention; 
         FIG. 8C  shows a schematic diagram of discharging according to a preferred embodiment of the present invention; and 
         FIG. 9  shows a structural schematic diagram according to another preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In order to make the structure and characteristics as well as the effectiveness of the present invention to be further understood and recognized, the detailed description of the present invention is provided as follows along with embodiments and accompanying figures. 
       FIG. 2  shows a structural schematic diagram according to a preferred embodiment of the present invention. As shown in the Figure, the touch panel with a discharging function according to the present invention comprises a scanning bus  10 , a sensing bus  20 , a control unit  30 , and a discharging circuit  32 . The scanning bus  10  is used for scanning a touch frame  40 . The sensing bus  20  interleaves with the scanning bus  10 , and senses at least a touched location on the touch frame  40 . Namely, the scanning bus  10  is coupled to a plurality of scanning lines  12 ; the sensing bus  20  is coupled to a plurality of sensing lines  22 . The plurality of scanning lines  12  of the scanning bus  10  interleave with the plurality of sensing lines  22  of the sensing bus  20 . The plurality of scanning lines  12  and the plurality of sensing lines  22  are located in different layers. Between the plurality of scanning lines  12  and the plurality of sensing lines  22 , nonconductive objects such as spacers, glass, or films are used for isolating the layers of the lines (not shown in the Figure) and forming the touch frame  40 . The above-mentioned technique is common for persons having ordinary skill in the art, and hence will not be described further in detail. The plurality of scanning lines  12  and the plurality of sensing lines  22  are formed on conductive films. A preferred embodiment of the conductive film is a transparent conductive oxide (TCO) film. According to the present invention, the grid structure of touch panel is adopted for achieving the multi-point touch effect. However, this is only a preferred embodiment of the present invention. The present invention is not limited to the structure of touch panel. Those touch panels formed by conductive films are within the scope of the present invention. 
     The control unit  30  is coupled to the scanning bus  10  and the sensing bus  20  for controlling them. A plurality of switches  14  are disposed between the scanning bus  10  and the plurality of scanning lines  12 , respectively. The control unit  30  controls the plurality of switches  14 , and hence controlling the scanning bus  10  to scan the touch frame  40  via the plurality scanning lines  12 . Likewise, a plurality of switches  24  are disposed between the sensing bus  20  and the plurality of sensing lines  22 , respectively. The control unit  30  controls the plurality of switches  24 , and hence controlling the sensing bus  20  to sense if the touch frame  40  is touches. When the touch frame  40  is touched, the scanning bus  10  and the sensing bus  20  will produce at least a scanning signal and at least a sensing signal, respectively, according to the touched location on the touch frame  40 , and transmit the scanning signal and the sensing signal to the control unit  30 , respectively. The control unit  30  then calculates to give the coordinate of the touched location according to the scanning signal and the sensing signal. 
     Because some portions of the plurality of scanning lines  12  coupled to the scanning bus  10  cross with some portions of the plurality of sensing lines  22  coupled to the sensing bus  20 , the parasitic capacitance effect occur at the locations where the conductive films cross each other. Alternatively, some residual charges remains on the scanning lines  12  and the sensing lines  22 . During the using process of the touch frame  40  of the touch panel, after many touches, it is easy to increase the charges on the touch panel and thereby affecting the overall performance. In some circumstances, the signal will be produced even the touch panel is not touched, leading to false judgment. In other words, at the scanning transient, the signal on the scanning bus  10  may interfere the signal on the sensing bus  20  owing to the coupling effect between parasitic capacitors in the touch panel. Consequently, when the system measures, erroneous judgment for the signals occurs, reducing drastically the accuracy. 
     Accordingly, the touch panel according to the present invention uses the discharging circuit  32  coupled to the sensing bus  20  and controlled by the control unit  30  for releasing the charges at the touched location on the touch frame  40 . Thereby, after many touches during the using process of the touch panel, the charges accumulated on the touch panel can be avoided, and hence increasing the overall performance and preventing erroneous judgment for the untouched condition. 
       FIG. 3  shows a structural schematic diagram according to another preferred embodiment of the present invention. As shown in the figure, the difference between the present embodiment and the one in  FIG. 2  is that the discharging circuit  32  according to the present embodiment is disposed between the scanning bus  10  and the scanning lines  12 , and is controlled by the control unit  30  for releasing the charges at the touched location of the touch frame  40 . Thereby, the charges accumulated on the touch panel are reduced, and hence increasing the overall performance and preventing erroneous judgment for the untouched condition. 
       FIG. 4  shows a structural schematic diagram according to another preferred embodiment of the present invention. As shown in the figure, the difference between the present embodiment and those described above is that the discharging circuit  32  according to the present embodiment is disposed on the scanning bus  10  as well as the sensing bus  20  for enhancing charge releasing effect and hence increasing the sensing accuracy of the touch panel. Because the discharging circuit  32  according to the present embodiment is the same as those described above, its details will not be described further. 
       FIG. 5  shows a structural schematic diagram according to another preferred embodiment of the present invention. As shown in the figure, the difference between the present embodiment and the one in  FIG. 2  is that the discharging circuit  32  according to the present embodiment comprises a plurality of discharging switches  34  disposed between the sensing bus  20  and the sensing lines  22 , respectively. When the control unit  30  produces the discharging signal to the plurality of discharging switches  34 , the plurality of discharging switches  34  are closed for releasing the charges accumulated at the touched location on the touch frame  40 . The discharging switch  34  can be a field-effect transistor or a bipolar junction transistor (BJT). However, using a field-effect transistor or a BJT as the discharging switch  34  is only a preferred embodiment, not used for limiting the scope of the present invention. 
       FIG. 6  shows a structural schematic diagram according to another preferred embodiment of the present invention. As shown in the figure, the difference between the present embodiment and the one in  FIG. 5  is that the plurality of discharging switches of the discharging circuit  32  according to the present embodiment are disposed between the scanning bus  10  and scanning lines  12  for releasing the charges accumulated at the touched location on the touch frame  40 . 
       FIG. 7  shows a discharge timing diagram according to a preferred embodiment of the present invention. As shown in the figure, the control unit  30  according to the present invention controls the sensing lines  22  of the sensing bus  20  to discharge (as shown in  FIG. 2 ) while the scanning bus  10  is scanning and hence releasing the charges on the touch frame  40 . Alternatively, the control unit  30  controls the discharging circuit  32  to discharge the scanning lines  12  of the scanning bus  10 . The control unit  30  also can control the discharging circuit  32  to discharge the scanning lines of the scanning bus  10  and the sensing lines  22  of the scanning bus  20  simultaneously. The control unit  30  discharges the touch frame  40  according to a discharge timing and hence releasing the charges accumulated at the touched location or/and relevant circuits between the touched location and the buses. In other words, the control circuit  30  drives the scanning bus  10  to produce a scanning signal. Then, the control circuit  30  produces and transmits a discharging signal to the discharging circuit  32  for discharging the sensing bus  20  or discharging the rest un-scanned scanning lines. In addition, the control unit can adjust the discharge timing for controlling the time for releasing the residual charges on the touch frame  40 . Namely, the control circuit  30  can control a discharging time AT of the discharging circuit  32  and determine the discharging time for the touch frame  40 . Thereby, the parasitic capacitance effect can be avoided, and thus increasing the sensing accuracy of the touch panel. 
     Besides, the timing by which the control unit  30  controls the discharging circuit  32  described above is only a preferred embodiment, not used for limiting the present invention. In the following, various discharge timing by which the control unit  30  controls the discharging circuit  32  is described. First, also refer to  FIG. 8A , which shows a schematic diagram of discharging according to a preferred embodiment of the present invention. As shown in the figure, before the control unit  30  controls the scanning bus  10  to scan the touch frame  40 , the control unit  30  controls the discharging circuit  32  of the sensing bus  20  to release the charges at the touched location and on the relevant path between the touched location and the buses. In other words, when the control unit  30  is to sense if the touch frame  40  is touched, before the control unit  30  controls the scanning bus  10  to scan, the control unit  30  controls the discharging circuit  32  to release charges on the touch frame  40 , which is accomplished by closing the plurality of discharging switches  34  and hence releasing the charges on the touch frame  40 . Similarly, after the control unit  30  scans the touch frame  40 , the control unit  30  controls the discharging circuit  32  of the sensing bus  20  to release the charges at the touched location and on the relevant path between the touched location and the buses. 
     In addition, when the discharging circuit  32  is disposed on the scanning bus  10  (not shown in the figure), before and after the control unit  30  scans the touch frame  40 , the control unit  30  controls the discharging circuit  32  of the scanning bus  10  to release the charges at the touched location and on the relevant path between the touched location and the buses. This discharging method is the same as the one described above, and hence will not be described any further. 
     Moreover, before or after sensing bus  20  senses the touched location, the control unit  30  can control the discharging circuit  32  of the scanning bus  10  to release the charges at the touched location and on the relevant path between the touched location and the buses on the touch frame  40  for avoiding accumulation of residual charges. Besides, after the scanning bus  10  or the sensing bus  20  completes a scanning cycle, the control unit  30  can control the discharging circuit  32  of the scanning bus  10  to release the charges at the touched location and on the relevant path between the touched location and the buses on the touch frame  40  for avoiding accumulation of residual charges at the touched location and on the plurality of scanning lines  12  or on the plurality of sensing lines  22 . 
       FIG. 8B  shows a schematic diagram of discharging according to a preferred embodiment of the present invention. As shown in the figure, the difference between the present preferred embodiment and the one in  FIG. 8A  is that according to the present preferred embodiment, each sensing line  22  of the sensing bus  20  releases the charges at the touched location on the touch frame  40  and on the path of the sensing line  22 . The discharge timing according to the present preferred embodiment is the same the one in  FIG. 8A , and hence will not be described again. 
       FIG. 8C  shows a schematic diagram of discharging according to a preferred embodiment of the present invention. As shown in the figure, the difference between the present preferred embodiment and previous one is that, according to the present preferred embodiment, when the scanning bus  10  scans the touch frame  40  the control unit  30  controls the discharging circuit  32  to release charges on the un-scanned scanning lines  12  of the scanning bus  10 . Namely, when the scanning bus  10  scans the second scanning line  34  of the touch frame  40 , the control unit  30  can close the discharging switches  36 ,  38  on adjacent scanning lines and release charges. Thereby, the parasitic capacitance effect can be avoided, and the sensing accuracy of the touch panel can be enhanced. Besides, the control unit  30  also can control the discharging circuit  32  to release the charges on the plurality of scanning lines  12  being scanned by the scanning bus  10 . In other words, when the scanning bus  10  scans the second scanning line  34  of the touch frame  40 , the control unit  30  can release the charges on the second scanning line  34  at the same time. Likewise, when the scanning bus  10  scans the touch frame  40 , the control unit  30  can control the discharging circuit  32  to release the charges on the un-sensed sensing lines  22  of the sensing bus  20  (not shown in the figure). Moreover, when the scanning bus  10  scans the touch frame  40 , the control unit  30  can control the discharging circuit  32  to release the charges on the plurality of sensing lines  22  being sensed by the sensing bus  20 . Because the drawing of this embodiment is easily figured out by persons having ordinary skill in the art, it will not be drawn again. 
       FIG. 9  shows a structural schematic diagram according to another preferred embodiment of the present invention. As shown in the figure, the difference between the present preferred embodiment and the previous one is hat the discharging circuit  32  according to the present preferred embodiment is disposed on both the scanning bus  10  and the sensing bus  20  for increasing charge-releasing effect, and hence enhancing sensing accuracy of the touch panel. Because the discharging circuit  32  according to the present preferred embodiment is the same as the one in the previous preferred embodiment, it is not described in more detail. 
     To sum up, the touch panel with a discharging function according to the present invention comprises a scanning bus, a sensing bus, a control unit, and a discharging circuit. The scanning bus is used for scanning a touch frame. The sensing bus interleaves with the scanning bus, and senses at least a touched location on the touch frame. The control unit is coupled to the scanning bus and the sensing bus  20 ′ for controlling them. The discharging circuit is coupled to the sensing bus or/and the scanning bus, and is controlled by the control unit for releasing the charges at the touched location or/and on the relevant path between the touched location and the buses. Thereby, by using a discharging circuit for releasing charges on the parasitic capacitor, the parasitic capacitance effect is avoided. Hence, the sensing accuracy of the touch panel is increased. 
     Accordingly, the present invention conforms to the legal requirements owing to its novelty, nonobviousness, and utility. However, the foregoing description is only embodiments of the present invention, not used to limit the scope and range of the present invention. Those equivalent changes or modifications made according to the shape, structure, feature, or spirit described in the claims of the present invention are included in the appended claims of the present invention.