Abstract:
A detecting method for a touch panel is disclosed. The sensing electrode of the detecting method is indirectly and repeatedly charged several times via the charge holding capacitor circuit to reach a certain higher voltage. The driving electrode is switched to the first voltage or the second voltage under the cooperation of the driving circuit when several measuring cycle is conducted. After the voltage is switched every time, several measured values of different situations are obtained rapidly so as to eliminate the noise to get the best signal via several measured values. There is only to wait the balancing time in the measuring cycle, which effectively shortens the reaction time of the touch detecting.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority to Taiwan patent application Ser. No. 104137519 entitled “DETECTING METHOD OF TOUCH PANEL AND DETECTION CIRCUIT THEREOF”, filed Nov. 13, 2015, which is also incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present invention pertains to a detecting method for an identification device, and particularly relates to a detecting method and detection circuit thereof that can quickly get touch signal of a touch panel. 
       BACKGROUND OF THE INVENTION 
       [0003]    A touch panel or touch screen is one of the major interfaces between human and machine, and as a recognition device, can ingeniously combine input and display interfaces, and therefore has the advantages of saving device space and user-friendly operation. Nowadays it has been generally applied to a wide variety of consuming or industrial electronic products. For example, PDAs (Personal Digital Assistant), palm-sized PCs (Personal Computers), tablet computers, mobile phones, handwriting input devices for a smart phone, IAs (Information Appliances), ATMs (Automated Teller Machines) and POS (Points-of-Sale), etc., which can generally be seen in various occasions of business and industry applications. 
         [0004]    The detection method in the prior art subtracts the signal to eliminate the noise, by the way of repeating a measuring cycle to obtain more than two different detection voltage signal and then subtracting it to eliminate the noise for a contact signal. 
         [0005]    Besides, U.S. patent Ser. No. 12/466,230 of the prior art discloses a different detection method, comparing the several signals from the measured cycling and the accepted value range between the maximum and the minimum, abandoning the signal beyond the scope, determining the touch location by the change of one or several signals within the accepted range. In addition, TW Patent No. 100112718 discloses another way, scanning the capacitive matrix for the touch screen in rows and in lines respectively, and in two rows or in two lines at the same time to get the capacitance difference, or in one row or in one line to get the capacitance difference, proceeding to the date process then. 
         [0006]    Summarily, the detection methods above have many shortcomings, it needs to measure the sensing electrode when the driving electrode is uncharged, the reaction time is slowed down. Besides, every measuring cycle needs ground discharging, driving, waiting for the potential balance, discharging, waiting for the discharging to finish, so much unnecessary time is wasted, the reaction speed of the touch detection is slowed down also. Therefore, there is a need for a new method with time saving and better signal performance. 
       SUMMARY OF THE PRESENT INVENTION 
       [0007]    The present invention provides an improved detecting method for a touch panel and a detecting circuit thereof, which effectively excludes the noise interference during the detecting so as to shorten the processing time. 
         [0008]    In order to achieve one, some or all of the above stated objectives or others, a detecting method for a touch panel according to the embodiments of the present invention is provided. The detecting method for a touch panel, the touch panel includes at least one driving electrode and at least one sensing electrode, the detecting method comprising: initializing the driving electrode and the sensing electrode so that both of the driving electrode and the sensing electrode are in a grounding state; coupling the sensing electrode to a charge holding capacitor circuit; switching the sensing electrode to a floating state; after the charging process of the charge holding capacitor circuit is done, charging the sensing electrode by the charge holding capacitor circuit; switching the driving electrode to an initial voltage; disconnecting the charge holding capacitor circuit and the sensing electrode after the balance of potential is completed, and measuring the charge holding capacitor circuit by an analog to digital converter to obtain an initial value; conducting a measuring cycle, the measuring cycle comprising: switching the driving electrode to a first voltage or a second voltage according to a switching mode, the switching mode depends on the back-end filter; coupling the sensing electrode to the charge holding capacitor circuit; and disconnecting the charge holding capacitor circuit and the sensing electrode after the balance of potential is completed, and measuring the charge holding capacitor circuit by the analog to digital converter to obtain a measured value; repeating the measuring cycle to obtain a plurality of the measured values; switching the sensing electrode to the grounding state; and switching the driving electrode back to the grounding state. 
         [0009]    In better embodiment of the present invention, the detecting method further comprises a process of calculating the initial value and the measured values by a controlling unit to obtain a signal value. 
         [0010]    In order to achieve one, some or all of the above stated objectives or others, a detecting circuit for a touch panel according to the embodiments of the present invention is provided. The detection circuit for a touch panel, the touch panel includes at least one driving electrode and at least one sensing electrode, comprising: a charge holding capacitor circuit, selectively coupling with the sensing electrode; a charging circuit, selectively coupling with the charge holding capacitor circuit; and a driving circuit, for driving electrode being switchable between a grounding state or any voltage; an analog to digital converter, electrically coupling with the sensing electrode; and a controlling unit, electrically coupling with the charge holding capacitor circuit, the driving circuit, the analog to digital converter, the driving electrode and the sensing electrode, the controlling unit performs the above detecting method. 
         [0011]    The sensing electrode of the present invention is indirectly and repeatedly charged several times via the charge holding capacitor circuit to reach a certain higher voltage. The driving electrode is switched to the first voltage or the second voltage under the cooperation of the driving circuit when several measuring cycle is conducted. After the voltage is switched every time, several measured values of different situations are obtained rapidly, there is only to wait the balancing time, so as to eliminate the noise to get the best signal via several measured values. Compared with the prior art, the measuring cycle of the present invention is conducted only the balancing time is needed, every measuring cycle in the prior art needs ground discharging, driving, waiting for the potential balance, discharging, waiting for the discharging to finish. The present invention effectively shortens the reaction time of the touch detecting. In addition, the electromagnetic interference from the environment and the power, the noise caused by induced electric field from the driven LCD screen is deduced, especially the low frequency noise. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  depicts a diagram of a touch panel and the detection circuit thereof according to an embodiment of the present invention. 
           [0013]      FIG. 2  depicts a schematic diagram of the detection circuit for a touch panel according to an embodiment of the present invention. 
           [0014]      FIG. 3  depicts a flow chart of the detection method for a touch panel according to an embodiment of the present invention. 
           [0015]      FIG. 3A  depicts a block diagram of the measuring cycle process according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    The present invention can be more fully understood by reading the following detailed description of the preferred embodiments, with reference made to the accompanying drawings. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. It should be noted that, as used in the specification and the appended claims, the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a display” may include multiple displays, and the like. References cited herein are hereby incorporated by reference in their entirety, except to the extent that they conflict with teachings explicitly set forth in this specification. 
         [0017]    Please refer to  FIG. 1 ,  FIG. 1  shows a capacitive touch panel  100  and the detection circuit  200  thereof according to an embodiment of the present invention. The touch panel  100  includes at least one driving electrode  110  and at least one sensing electrode  120 . The driving electrode  110  and the sensing electrode  120  are made of conductive materials in matrix and the sensing electrode  120  is above the driving electrode  110 . The driving electrode  110  is made of stripes in rows, the sensing electrode  120  is made of strips in lines. The capacitive touch panel  100  with matrix structure electrically couples with the detection circuit  200  to perform touch control function. 
         [0018]    The schematic diagram of the detection circuit  200  for the touch panel  100  according to the present invention is shown in  FIG. 2 . The detection circuit  200  includes a switching circuit  210 , a charge holding capacitor circuit  220 , a charging circuit  230 , a driving circuit  240 , an analog to digital converter  250  (ADC) and a controlling unit  260 . The controlling unit  260  is electrically coupling with the switching circuit  210 , the charge holding capacitor circuit  220 , the driving electrode  240 , the analog to digital converter  250 , the driving electrode  110  and the sensing electrode  120  so as to control the detecting method of the detection circuit  200  for the touch panel  100 . 
         [0019]    The switching circuit  210  is selectively coupled with the sensing electrode  120 , the sensing electrode  120  is in a grounding state when the switching circuit  210  coupled with the sensing electrode  120 , the sensing electrode  120  is in a floating state when the switching circuit  210  disconnect with the sensing electrode  120 . The charge holding capacitor circuit  220  is selectively coupled with the sensing electrode  120  via two switches P&amp;Q which is one kind of multiplexer. The charging circuit  230  is selectively coupled with the charge holding capacitor circuit  220  via the switches P&amp;Q to provide a charging voltage V c . The sensing electrode  120  is indirectly charged by the charging circuit  230  via the charge holding capacitor circuit  220  under the control of the switches P&amp;Q. The driving circuit  240  can switch the driving electrode  110  to the grounding state or provide any voltage V H  for the driving electrode  110 . The voltage V H  includes an initial voltage, a first voltage and a second voltage. The charge holding capacitor circuit  220  is measured by an analog to digital converter  250  by means of disconnecting the contact between the charge holding capacitor circuit  220  and any other circuit or electrode via the switch P/Q. 
         [0020]      FIGS. 3&amp;3A  depict flow charts of the detection method and the measuring cycle process for a touch panel according to an embodiment of the present invention. Refer to  FIG. 2  showing a schematic diagram of the detection circuit, the detection method is used for the touch panel above. The detection method of the present invention includes three phases, the first phase is a starting process which comprises steps of S 1 -S 9 , the second phase is a loop process which comprises steps of S 10 -S 11 , and the third phase is an ending process which comprises steps of S 10 -S 12 . The steps includes: 
         [0021]    Step S 1 : The controlling unit  260  initializes the driving electrode  110  and the sensing electrode  120  so that both of the driving electrode  110  and the sensing electrode  120  are in a grounding state. Residual charges on the driving electrode  110  and the sensing electrode  120  is cleared as the driving electrode  110  and the sensing electrode  120  are in a grounding state. 
         [0022]    Step S 2 : The controlling unit  260  controls the switches P&amp;Q so that the sensing electrode  120  is coupled with the charge holding capacitor circuit  220 . 
         [0023]    Step S 3 : Through a first delayed discharge, the sensing electrode  120  is switched to be in a floating state by the controlling unit  260  via the switching circuit  210  while the driving electrode  110  is still in a grounding state. 
         [0024]    Step S 4 : The controlling unit  260  controls the switches P&amp;Q so that the charging circuit  230  couples with the charge holding capacitor circuit  220  to charge the charge holding capacitor circuit  220  in a certain charging voltage V c . 
         [0025]    Step S 5 : Next, the controlling unit  260  controls the switches P&amp;Q to charge the sensing electrode  120  by the charge holding capacitor circuit  220 . 
         [0026]    Step S 6 : Repeating the steps S 4 -S 5  until the sensing electrode  120  reaches a certain voltage. The certain voltage includes the average value of the charging voltage V c  provided for the charging circuit  230  or the half V c /2. 
         [0027]    Step S 7 : The controlling unit  260  controls the driving circuit  240  to convert the driving electrode  110  from grounding state to the state of providing an initial voltage V H . 
         [0028]    Step S 8 : The electric charges on the driving electrode  110  and the sensing electrode  120  remains stable though a second delay while the balance of potential is completed. 
         [0029]    Step S 9 : The charge holding capacitor circuit  220  disconnects with the sensing electrode  120  when the controlling unit  260  controls the switches P or Q. Next, measuring the charge holding capacitor circuit  220  by an analog to digital converter  250  to obtain an initial value. Through a third delay after the measuring is finished, the controlling unit  260  determines whether to adjust the measuring frequency of an uncertain value for the switching mode based on the back-end filter (not shown); in other words, from the starting process to the loop process. 
         [0030]    Step S 10 : Conducting a measuring cycle by the controlling unit  260 , which means it is entering the loop process. As in  FIG. 3A , the flowchart of the measuring cycle S 10  includes the steps S 101  to S 105 . 
         [0031]    Step S 101 : The controlling unit  260  drives the driving circuit  240  to maintain the initial voltage during the S 7 , or to provide the first voltage for the driving electrode  110 , or to switch the second voltage to the driving electrode  110  according to the switching mode. In the embodiment of the present invention, the initial voltage is any voltage above 0, the first voltage includes 0V and any voltage below 5V, the second voltage includes 18V and any voltage above 5V. In step  101 , the controlling unit  260  decides the switching mode based on the back-end filter (not shown) according to S 9 . 
         [0032]    Step S 102 : The controlling unit  260  controls the switches P&amp;Q so that the sensing electrode  120  is coupled with the charge holding capacitor circuit  220 . 
         [0033]    Step S 103 : The electric charges on the driving electrode  110  and the sensing electrode  120  remains stable through a fourth delay after the balance of potential is completed. The fourth delay period is longer than the third delay period in the embodiment of the present embodiment. 
         [0034]    Step S 104 : The charge holding capacitor circuit  220  disconnects with the sensing electrode  120  when the controlling unit  260  controls the switches P&amp;Q. Next, a measured value is obtained by measuring the charge holding capacitor circuit  220  via an analog to digital converter  250 . 
         [0035]    Step S 105 : Through a third delay after the measuring is finished, the controlling unit  260  determines whether to adjust the switching mode based on the back-end filter proceeding to the next step. S 105  is the result of the controlling unit  260  based on S 104 . The back-end filter determines whether to change the switching mode, so that the driving electrode  110  continually remains on the first voltage when S 11  repeats S 101  of the measuring cycle in S 10 ; or the driving electrode  110  continually remains on the second voltage; or the driving electrode  110  continually remains on the first voltage of several times after remaining on the second voltage of several times; or the driving electrode  110  continually remains on the second voltage of several times after remaining on the first voltage of several times; or the driving electrode  110  remains on the first voltage and the second voltage in turn. The changing of the first voltage and the second voltage depends on the back-end filter. 
         [0036]    Step S 11 : Repeating the measuring cycle in S 10  to get several measured values. The repeating times are odd in the embodiment of the present invention. If there is a need to cease the measuring cycle S 10 , which also means preparing from the loop process to the ending process, S 105  in measuring cycle S 10  is omitted and the last measuring cycle S 10  is conducted before S 12 . 
         [0037]    Step S 12 : Proceed to the ending process. The detection process is ended as the driving electrode  110  and the sensing electrode  120  are converted to the grounding state. 
         [0038]    When the driving electrode  110  is switched to the first voltage (it is referred to any voltage of 0 V or below 5V) in the measuring cycle S 10 , a plurality of first measured values are read which includes only noise and a first base value. When the driving electrode  110  is switched to the second voltage (it is referred to a higher voltage of 18 V or above 5V) in the measuring cycle S 10 , a plurality of second measured values are read. If any object is proximate to the touch panel, the second measured value includes noise, a second base value and a first contact value. If no object is proximate to the touch panel, the second measured value includes only noise and the second base value. 
         [0039]    Finally, the initial value obtained in S 9  and several measured values obtained in S 10 -S 11  cannot be used alone as noise is included, thus, it&#39;s impossible to tell the touch signal of the object. A usable touch signal is obtained by handling the values above via the controlling unit  260 . After conducting the detection method of Starting-Loop-Ending, the initial value and measured values are obtained, which include the second measured values of m numbers when the driving electrode  110  remains on the second voltage and the first measured values of n numbers when the driving electrode  110  remains on the first voltage, the second measured values include noise, the second base value and/or the first contact value. It&#39;s worth mentioning the number of m and n is positive integer. 
         [0040]    The controlling unit  260  inputs the values of m+n numbers to the back-end filter, noise is cleared after data processing, the data processing includes amplifying the useable signal and a filtering operation. It&#39;s worth mentioning the number of m and n depends on the back-end filter, one of m or n can be zero in one embodiment of the present invention. If there is any object proximate to the touch panel, the controlling unit  260  outputs a third base value and a second contact value of a certain magnification. If no object is proximate to the touch panel, the third base value of a certain magnification is output by the controlling unit  260 . The third base value of the certain magnification is used as a basis of the data processing. Useable touch signal is gained after the controlling unit  260  processing the third base value and the second contact value of the certain magnification to eliminate the noise of lower frequency. Besides, frequency hopping is preferred after gaining the touch signal to achieve better touch signal. 
         [0041]    In a better embodiment, the driving electrode  110  is made of stripes in rows, the sensing electrode  120  is made of strips in lines. The strips of the sensing electrode  120  are measured by the analog to digital converter  250 , in order to produce several initial values or measured values. Next, further calculation is conducted by the controlling unit  260  based on the average of the initial values and the average of the measured values. 
         [0042]    In the above embodiment, the driving electrode  110  is defined in a grounding state when the starting process is initialized, then it is switched to any voltage V H  to detect the touch signal of the operating object by means of changing the voltage of the driving electrode via the driving circuit  240 . Thus, in S 12  of the ending process, the driving electrode  110  is back to the initial state (grounding state) by the driving circuit  240 . However, if the initialization conditions of the detection method differ during the three processes, the driving electrode  110  is defined on any voltage V H  when the starting process is initialized, then changed to the grounding state after that. The driving electrode  110  is back to the initialized state (any voltage V H ) by the driving circuit  240 , which can also detect the touch signal of the operating object. The state of the driving electrode  110  isn&#39;t limited whether on a grounding state or any voltage in the initializing process. 
         [0043]    The sensing electrode  120  is switched to the grounding state by the controlling unit  260  via the switching circuit  210  only in the last step of S 12  and the initializing of S 1  during the detection method process of the detection circuit. It is not necessary to make the sensing electrode  120  in a grounding state for conducting the starting process during the steps S 2 -S 9  and the loop process during the steps S 10 -S 11 .The driving electrode is switched to the first voltage or the second voltage for several times via the driving circuit during the step S 10 , the measuring cycle is conducted after every switch is finished through the potential is balanced. 
         [0044]    The invention provides a plurality of measured values in different modes as the measuring cycle is conducted rapidly and gets better touch signal via a plurality of values filtering the noise. Further, the sensing electrode of the invention reaches a certain higher voltage via the charge holding capacitor circuit, when the measuring cycle is conducted at the first voltage, the problem of incapable of measuring is avoided. Besides, the electromagnetic interference from the environment and the power, the noise caused by induced electric field from the driven LCD screen is deduced, especially the low frequency noise.