Patent Publication Number: US-9891761-B2

Title: Touch sensing device and touchscreen device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2013-0167353 filed on Dec. 30, 2013, with the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     The present disclosure relates to a touch sensing device and a touchscreen device. 
     A touchscreen device, such as a touchscreen or a touch pad, is a data input device attached to a display device so as to provide an intuitive user interface, and has recently been widely applied to various electronic devices such as cellular phones, personal digital assistants (PDA), and navigation devices. Particularly, as demand for smartphones has been recently increased, touchscreens have been increasingly employed therein, since they are able to provide users with various data input methods in a limited form factor. 
     Touchscreens used in portable devices may be mainly divided into resistive type touchscreens and capacitive type touchscreens, depending on the manner in which touches are sensed therein. Among these, capacitive type touchscreens have advantages of a relatively long lifespan and ease in the implementation of various types of data input and gestures therefor, and thus it has been increasingly employed. It is especially easy to implement a multi-touch interfaces with capacitive type touchscreens, as compared to resistive type touchscreens, and thus, capacitive type touchscreens are widely used in smartphones and the like. 
     Capacitive type touchscreens include a plurality of electrodes having a predetermined pattern and the electrodes form a plurality of nodes in which changes in capacitance are generated due to touches. The nodes provided on a two-dimensional plane generate changes in self-capacitance or changes in mutual-capacitance due to touches. Coordinates of touches may be calculated by applying a weighted average calculation method or the like to changes in the capacitance occurring in the nodes. 
     Recently, applications allowing touchscreen devices to detect various types of gesture are being developed for increased user convenience. To this end, techniques of forming capacitance in wide areas around electrodes and of detecting minute changes in capacitance are required. 
     RELATED ART DOCUMENT 
     (Patent Document 1) Korean Patent Laid-Open Publication No. 2011-0103790 
     SUMMARY 
     An aspect of the present disclosure may provide a touch sensing device and a touchscreen device capable of precisely detecting a proximity touch that is not made directly to a touch panel. 
     According to an aspect of the present disclosure, a touch sensing device may include: a driving circuit applying a driving signal having a predetermined first period to a node capacitor; a buffer circuit converting capacitance of the node capacitor into a voltage signal; a buffer capacitor being charged and discharged depending on an output voltage from the buffer circuit; and an integration circuit integrating voltages charged in the buffer capacitor, wherein, in a normal touch mode, the buffer circuit integrates capacitance of the node capacitor to generate the voltage signal, and, in a proximity touch mode, the buffer circuit generates the voltage signal by following the voltages charged in the node capacitor. 
     The driving circuit unit may include: a first switch connected between a first node of the node capacitor and a supply voltage terminal; and a second switch connected between the first node of the node capacitor and a common-mode voltage terminal, wherein the first and second switches are switched on and off by first and second clock signals, each of the first and second clock signals having a first period and the first and second clock signals having a phase difference of 180 degrees with respect to each other. 
     The buffer circuit may include: a first operational amplifier; a third switch connected between a second node of the node capacitor and an inverting input terminal of the first operational amplifier; a fourth switch connected between the second node of the node capacitor and the common-mode voltage terminal; a fifth switch connected between the inverting input terminal and an output terminal of the first operational amplifier; a sixth switch connected between the second node of the node capacitor and the non-inverting input terminal of the first operational amplifier; a seventh switch connected between the non-inverting input terminal of the first operational amplifier and the terminal of the common-mode voltage; and a first feedback capacitor connected to the fifth switch in parallel. 
     In the normal touch mode, the third switch may be switched on and off by a third clock signal having a predetermined second period, the fourth switch and the fifth switch may be switched on and off by a fourth clock signal having the second period, the sixth switch may be turned off, the seventh switch may be turned on, and the third clock signal and the fourth clock signal may have a phase difference of 180 degrees with respect to each other. 
     The second period may be equal to half of the first period. 
     In the proximity touch mode, the third switch, the fourth switch and the seventh switch may be turned off, and the fifth switch and the sixth switch may be turned on. 
     The integration circuit may include: a second operational amplifier; an eighth switch connected between the inverting input terminal of the second operational amplifier and the buffer capacitor; a ninth switch connected between the buffer capacitor and the common-mode voltage terminal; a tenth switch connected between the inverting input terminal and an output terminal of the second operational amplifier; and a second feedback capacitor connected to the tenth switch in parallel. 
     In the normal touch mode, the eighth switch may be switched on and off by a fifth clock signal having the first period, the ninth switch may be switched on and off by a sixth clock signal having the first period, and the fifth clock signal and the sixth clock signal may have a phase difference of 180 degrees with respect to each other. 
     The fifth clock signal may have a phase difference of 90 degrees with respect to the driving signal. 
     In the proximity touch mode, the eighth switch may be switched on and off by a fifth clock signal having the first period, the ninth switch may be switched on and off by a sixth clock signal having the first period, and the fifth clock signal and the sixth clock signal may have a phase difference of 180 degrees with respect to each other. 
     The fifth clock signal and the driving signal may be in-phase. 
     According to another aspect of the present disclosure, a touch sensing device may include: a driving circuit applying a driving signal having a predetermined first period to a node capacitor; a first operational amplifier having a non-inverting input terminal and an inverting input terminal connected to the node capacitor, and an output terminal connected to the inverting input terminal; a buffer capacitor being charged and discharged depending on an output voltage from the first operational amplifier; and an integration circuit integrating voltages charged in the buffer capacitor. 
     The driving circuit unit may include: a first switch connected between a first node of the node capacitor and a supply voltage terminal; and a second switch connected between the first node of the node capacitor and a common-mode voltage terminal, wherein the first and second switches are switched on and off by first and second clock signals, each of the first and second clock signals having a first period and the first and second clock signals having a phase difference of 180 degrees with respect to each other. 
     The integration circuit may include: a second operational amplifier; an eighth switch connected between the inverting input terminal of the second operational amplifier and the buffer capacitor; a ninth switch connected between the buffer capacitor and the common-mode voltage terminal; a tenth switch connected between the inverting input terminal and an output terminal of the second operational amplifier; and a second feedback capacitor connected to the tenth switch in parallel. 
     The eighth switch may be switched on and off by a fifth clock signal having the first period, the ninth switch may be switched on and off by a sixth clock signal having the first period, and the fifth clock signal and the sixth clock signal may have a phase difference of 180 degrees with respect to each other. 
     The fifth clock signal and the driving signal may be in-phase. 
     According to another aspect of the present disclosure, a touchscreen device may include: a panel unit including a plurality of first electrodes extending in a first direction, and a plurality of second electrodes extending in a second direction intersecting the first direction; a driving circuit unit applying driving signals to a portion of the plurality of first electrodes; and a sensing circuit unit detecting capacitance from a portion of the plurality of the second electrodes near one ends thereof and from a portion near the other ends thereof, wherein the sensing circuit unit includes at least one operational amplifier behaving as a voltage follower. 
     The sensing circuit unit may include: a first operational amplifier having a non-inverting input terminal and an inverting input terminal connected to the portion of the plurality of the second electrodes near one ends thereof and to the portion near the other ends thereof, and an output terminal connected to the inverting input terminal; a buffer capacitor being charged and discharged depending on an output voltage from the first operational amplifier; and an integration circuit integrating voltages charged in the buffer capacitor. 
     The others of the plurality of first and second electrodes, than the portion to which the driving signals are applied and the portion from which the sensing signals are detected, may be kept in a floating state. 
     The touchscreen device may further include: a signal conversion unit converting the capacitance detected in the sensing circuit unit into a digital signal; and an operation unit determining whether a touch is made based on the digital signal. 
     The operation unit may acquire first direction information of the touch based on the digital signal. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The above and other aspects, features and other advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a perspective view showing an appearance of an electronic device including a touchscreen device according to an exemplary embodiment of the present disclosure; 
         FIG. 2  is a view of a panel unit included in a touchscreen device according to an exemplary embodiment of the present disclosure; 
         FIG. 3  is a cross-sectional view of the panel unit illustrated in  FIG. 2 . 
         FIG. 4  is a diagram illustrating a touchscreen device according to an exemplary embodiment of the present disclosure; 
         FIGS. 5 through 9  are diagrams for illustrating the operation of a touchscreen device according to an exemplary embodiment of the present disclosure; 
         FIG. 10  is a circuit diagram of a touch sensing device included in the touchscreen device of  FIG. 4 ; 
         FIG. 11  is a diagram for illustrating the operation of a touch sensing device in a normal touch mode according to an exemplary embodiment of the present disclosure; 
         FIG. 12  is a diagram for illustrating the operation of a touch sensing device in a proximity touch mode according to an exemplary embodiment of the present disclosure; and 
         FIG. 13  is an equivalent circuit of a buffer circuit in a proximity touch mode according to an exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a perspective view showing an appearance of an electronic device including a touchscreen device according to an exemplary embodiment of the present disclosure. 
     Referring to  FIG. 1 , the electronic device  100  according to the exemplary embodiment may include a display device  110  for displaying a screen, an input unit  120 , an audio unit  130  for outputting a voice, and a touchscreen device integrated with the display device  110 . 
     As shown in  FIG. 1 , it is common in mobile devices that a touchscreen device is integrated with a display device, and such a touchscreen device needs to have so high light transmittance that a screen displayed on the display device can be seen. Accordingly, such a touchscreen device may be implemented by forming an electrode with an electrically conductive material on a transparent substrate formed of a film such as polyethylene terephthalate (PET), polycarbonate (PC), polyethersulfone (PES), polyimide (PI), polymethylmethacrylate (PMMA), and cyclo-olefin polymer (COP), soda glass, or tempered glass. The conductive electrode may be formed of indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), carbon nano tube (CNT), or graphene, for example. Further, the conductive electrode may be implemented by forming any one of Ag, Al, Cr, Ni, Mo and Cu or an alloy thereof as a non-visible fine conductor lines. In a bezel area of the display device, wiring patterns connected to electrodes formed of a transparent, conductive material are arranged, and the wire patterns are shielded by the bezel area so that they are not visible. 
     Since the touchscreen device according to the exemplary embodiment is of a capacitive type, the touchscreen device may include a plurality of electrodes having a predetermined pattern. Further, the touchscreen device may include a capacitance sensing circuit to sense changes in the capacitance formed in the plurality of electrodes, an analog-digital conversion circuit to convert an output signal from the capacitance sensing circuit into a digital value, and an operation circuit to determine whether a touch is made using the data converted into digital value. 
       FIG. 2  is a view of a panel unit included in a touchscreen device according to an exemplary embodiment of the present disclosure. 
     Referring to  FIG. 2 , the panel unit  200  according to the exemplary embodiment includes a substrate  210  and a plurality of electrodes  220  and  230  provided on the substrate  210 . Although not shown in  FIG. 2 , each of the plurality of electrodes  220  and  230  may be electrically connected to a wiring pattern on a circuit board attached to one end of the substrate  210  through a wiring and a bonding pad. The circuit board may have a controller integrated circuit mounted thereon so as to detect sensing signals generated in the plurality of electrodes  220  and  230  and may determine whether a touch is made based on the detected sensing signals. 
     In a touchscreen device, the substrate  210  may be a transparent substrate on which the plurality of electrodes  220  and  230  are formed. On the region in which wirings for connecting to the plurality of electrodes  220  and  230  are provided, other than the region in which the plurality of electrodes  220  and  230  are provided, a printed region may be formed on the substrate  210  so as to shield the wirings typically formed of an opaque metal material so that they are not visible. 
     The plurality of electrodes  220  and  230  may be formed on one surface or both surfaces of the substrate  210 . Although the plurality of electrodes  220  and  230  are shown to have a lozenge- or diamond-shaped pattern in  FIG. 2 , it is apparent that the plurality of electrodes  220  and  230  may have a variety of polygonal shapes such as rectangle and triangle. 
     The plurality of electrodes  220  and  230  may include first electrodes  220  extending in the x-axis direction, and second electrodes  230  extending in the y-axis direction. The first electrodes  220  and the second electrodes  230  may be provided on both surfaces of the substrate  210  or may be provided on different substrates  210  such that they may intersect with each other. If all of the first electrodes  220  and the second electrodes  230  are provided on one surface of the substrate  210 , an insulating layer may be partially formed at intersection points between the first electrodes  220  and the second electrodes  230 . 
     A device, which is electrically connected to the plurality of electrodes  220  and  230  to sense a touch, detects changes in capacitance generated in the plurality of electrodes  220  and  230  by a touch to sense the touch based on the detected change in capacitance. The first electrodes  220  may be connected to channels defined as D 1  to D 8  in the controller integrated circuit to thereby receive driving signals, and the second electrodes  230  may be connected to channels defined as S 1  to S 8  to thereby be used for the controller integrated circuit to detect sensing signals. 
     The controller integrated circuit may acquire changes in capacitance generated among the first electrodes  220  and the second electrodes  230 , to use them as sensing signals. 
       FIG. 3  is a cross-sectional view of the panel unit illustrated in  FIG. 2 .  FIG. 3  is a cross-sectional view of the panel unit  200  illustrated in  FIG. 2  taken in the y-z plane, in which the panel unit  200  may further include a cover lens  240  that is touched, in addition to the substrate  210  and the plurality of electrodes  220  and  230  described with reference to  FIG. 2 . The cover lens  240  may be provided on the second electrodes  230  to receive a touch from a touching object  250  such as a finger. 
     When driving signals are sequentially applied to the first electrodes  220  through the channels D 1  to D 8 , mutual-capacitance is generated between the first electrodes  220 , to which the driving signals are applied, and the second electrodes  230 . When the driving signals are sequentially applied to the first electrodes  220 , changes in the mutual-capacitance is made between the first electrode  220  and the second electrode  230  close to the area with which the touching object  270  comes in contact. The change in the mutual-capacitance may be proportional to the overlapped area between the region that the touching object  270  comes into contact, and the region that the first electrodes  220 , to which the driving signals are applied, and the second electrodes  230 . In  FIG. 3 , the mutual-capacitance generated between the first electrodes  220  connected to channel D 2  and D 3 , respectively, and the second electrodes  230  is influenced by the touching object  270   
       FIG. 4  is a diagram illustrating a touchscreen device according to an exemplary embodiment of the present disclosure. 
     Referring to  FIG. 4 , the touchscreen device according to the exemplary embodiment may include a panel unit  310 , a driving circuit unit  320 , a sensing circuit unit  330 , a signal converting unit  340 , and an operating unit  350 . The driving circuit unit  320 , the sensing circuit unit  330 , the signal converting unit  340 , and the operating unit  350  may be implemented as a single controller integrated circuit (IC), i.e., a control circuit. 
     The panel unit  310  may include a plurality of first electrodes X 1  to Xm extending in a first axis direction (that is, the horizontal direction of  FIG. 4 ), and a plurality of second electrodes Y 1  to Yn extending in a second axis direction (that is, the vertical direction of  FIG. 4 ) crossing the first axis direction. 
     As described above, when a voltage is applied to a plurality of first electrodes X 1  to Xm and a plurality of second electrodes Y 1  to Yn, capacitance may be generated, and, in  FIG. 5 , capacitance generated at intersections of the plurality of first electrodes X 1  to Xm and the plurality of second electrodes Y 1  to Yn are denoted by node capacitors C 11  to Cmn. Further, although not shown in  FIG. 5 , it is to be understood that capacitance may also be formed between the first electrodes X 1  to Xm and between the second electrodes Y 1  to Yn. 
     The driving circuit unit  320  may apply predetermined driving signals to the first electrodes X 1  to Xm and to the second electrodes Y 1  to Yn of the panel unit  510 . The driving signals may be square wave signals, sine wave signals, triangle wave signals, or the like, having specific frequency and amplitude. Although circuits for generating and applying the driving signals are individually connected to the plurality of first and second electrodes X 1  to Xm and Y 1  to Yn in  FIG. 4 , it is apparent that a single driving signal generating circuit may be used to apply the driving signals to the first electrodes X 1  to Xm and to the second electrodes Y 1  to Yn by employing a switching circuit. 
     The sensing circuit unit  330  may be connected to the first and second electrodes X 1  to Xm and Y 1  to Yn to receive sensing signals and may detect changes in capacitance based on the received sensing signals. The sensing circuit unit  330  may include C-V converters to detect changes in capacitance as voltage. For example, each of the C-V converters may include at least one operational amplifier and a capacitor C 1  having a specific capacitance and may integrate changes in capacitance to output an analog signal in the form of voltage. 
     The signal conversion unit  340  may generate a digital signal S D  from the analog signals transmitted from the sensing circuit unit  330 . For example, the signal conversion unit  340  may include a time-to-digital converter (TDC) circuit measuring a time in which the analog signals in the form of voltage output from the sensing circuit unit  330  reach a predetermined reference voltage level to convert the measured time into the digital signal S D , or an analog-to digital-converter (ADC) circuit measuring an amount by which a level of the analog signals output from the sensing circuit unit  330  is changed for a predetermined time to convert the changed amount into the digital signal S D . 
     The operation unit  350  may determine whether a touch is made on the panel unit  310  based on the digital signal S D . The operation unit  350  may determine the number of touches, coordinates of the touches, and the type of gesture of the touches or the like made on the panel unit  310 , based on the digital signal S D . 
     The digital signal S D , which is used by the operation unit  350  to determine whether a touch is made, may be data that is a numerical value representing a change in capacitance of the capacitors C 11  to Cmn, especially representing a difference between the capacitance with and without a touch. Typically in a capacitive type touchscreen device, a region touched by a conductive object has less capacitance than other regions not touched. 
       FIGS. 5 through 9  are diagrams for illustrating the operation of a touchscreen device according to an exemplary embodiment of the present disclosure. In  FIGS. 5, 8 and 9 , Tx refers to driving signals generated in the driving circuit unit  320  of  FIG. 4 , and Rx refers to sensing signals acquired by the sensing circuit unit  330 . Although only a portion of the first and second electrodes X 1  to Xm and Y 1  to Yn of  FIG. 4  are shown for simplicity, it is apparent that more electrodes may be formed as shown in  FIG. 4 . 
     Hereinafter, a method of driving a touchscreen device according to the exemplary embodiment will be described with reference to  FIGS. 4 through 7 . 
       FIG. 5  is a diagram for illustrating the operation of a touchscreen device in a normal touch mode according to an exemplary embodiment of the present disclosure. 
     In the normal touch mode, the driving circuit unit  320  may sequentially apply driving signals Tx to the plurality of first electrodes X 1  to X 7 , and the sensing circuit unit  330  may be connected to the second electrodes Y 1  to Y 7  to acquire sensing signals Rx according to capacitance formed at intersections of the first electrodes X 1  to X 7  and the second electrodes Y 1  to Y 7 . 
     For example, when a driving signal Tx is applied to the first one X 1  of the first electrodes, capacitance is formed at each of intersections of the first one X 1  of the first electrodes and the second electrodes Y 1  to Y 8 , such that the sensing circuit unit  330  may acquire sensing signals Rx according to capacitance from the second electrodes. 
     It is to be noted that exemplary embodiments of the present disclosure are not limited thereto, but the driving signals Tx may be sequentially applied to the second electrodes Y 1  to Y 7 , such that sensing signals Rx may be acquired from the first electrodes X 1  to X 7 . 
       FIGS. 6 and 7  are diagrams for illustrating capacitance generated on a panel unit according to an exemplary embodiment of the present disclosure. 
     Referring to  FIGS. 6 and 7 , on the panel unit  310  according to an exemplary embodiment of the present disclosure, there may be mutual capacitance Cxy generated at each of intersections of the first electrodes and the second electrodes, parasitic capacitance Cxg generated between the first electrodes and ground potential GND, parasitic capacitance Cyg generated between the second electrodes and ground GND potential. The ground potential (GND) corresponds to the voltage level of a display device such as an LCD that is integrated with the touchscreen device. 
     In general, the mutual capacitance Cxy generated at each of intersections of the first electrodes and the second electrodes takes a large portion of the total capacitance on the panel unit. From a portion of the first electrodes disposed near ends thereof and from a portion of the second electrodes disposed near ends thereof, however, parasitic capacitances Cxg and Cyg may be detected relatively largely because they are less affected by the other electrodes. The parasitic capacitances Cxg and Cyg tend to be more widely generated than the mutual capacitance because the distance from the electrodes to a LCD is longer than that between the electrodes. According to the exemplary embodiment, by detecting the parasitic capacitances Cxg and Cyg, it may be determined whether a proximity touch is made. 
       FIGS. 8 and 9  are diagrams for illustrating the operation of a touchscreen device in a proximity touch mode according to an exemplary embodiment of the present disclosure. In the proximity touch mode according to the exemplary embodiment, a touchscreen device may alternately perform operations of acquiring first direction information and second direction information at a predetermined interval. In the following, the operation of the touchscreen device according to the embodiment of the present disclosure will be described in detail with reference to  FIGS. 8 and 9 . 
     Referring to  FIG. 8 , the driving circuit unit  320  may apply a driving signal Tx to the first one X 1  of the first electrodes X 1  to X 7 , and the sensing circuit unit  330  may acquire a sensing signal Rx from the first one Y 1  and the seventh one Y 7  of the second electrodes Y 1  to Y 7 . At this time, the second one X 2  to the seventh one X 7  of the first electrodes to which no driving signal Tx is applied and the second one Y 2  to the sixth one Y 6  of the second electrodes from which no sensing signal is detected may be in a floating state. Accordingly, magnetic field may widely propagate so that capacitance may be generated on other areas, as well as limited areas such as the intersection of the first one X 1  of the first electrodes and the first one Y 1  of the second electrodes or the intersection of the first one X 1  of the first electrodes and the seventh one Y 7  of the second electrodes. Therefore, capacitance are generated over large areas, even when a touching object such as a finger or a stylus pen is not directly touched on but proximate to the panel unit, it may be determined whether the touching object is at the first one Y 1  or at the seventh one Y 7  of the second electrodes. In other words, according to the exemplary embodiment, first direction information, i.e., information on the direction in which first electrodes extend of a touch may be acquired. 
     Although the driving signal Tx is applied to the first one X 1  of the first electrodes in the above exemplary embodiment, exemplary embodiments of the present disclosure is not limited thereto. The driving signal Tx may be applied to any one of the first electrodes, and, in addition to applying the driving signal Tx to one of the first electrodes, driving signals Tx may be applied to a portion or all of the first electrodes simultaneously. 
     Moreover, although the sensing circuit unit  330  acquires sensing signals Rx from the first one Y 1  and seventh one Y 7  of the second electrodes at the ends thereof in the above description, it is apparent that sensing circuit unit  330  may acquire sensing signals Rx from a portion of electrodes near the ends of the second electrodes, e.g., first, second, sixth and seventh ones Y 1 , Y 2 , Y 6  and Y 7  of the second electrodes. 
     Referring to  FIG. 9 , the driving circuit unit  320  may apply a driving signal Tx to the first one Y 1  of the second electrodes Y 1  to Y 7 , and the sensing circuit unit  330  may acquire a sensing signal Rx from the first one X 1  and the seventh one X 7  of the first electrodes X 1  to X 7 . 
     The operation of the touchscreen device according to the exemplary embodiment of  FIG. 9  is similar to that of the touchscreen device according to the exemplary embodiment of  FIG. 8  and, therefore, the description on the exemplary embodiment of  FIG. 8  may be applied, mutatis mutandis, to the exemplary embodiment of  FIG. 9 . 
     Unlike the exemplary embodiment of  FIG. 8  in which the touchscreen device acquires the first direction information in which first electrodes extend of a touch, the touchscreen device according to the exemplary embodiment of  FIG. 9  may acquire second direction information in which the second electrodes extend of a touch. 
       FIG. 10  is a circuit diagram of a touch sensing device included in the touchscreen device of  FIG. 4 . The touch sensing device of  FIG. 10  may include a drive circuit  325 , a buffer circuit  333 , a buffer capacitor Cn, and an integration circuit  337 . The drive circuit  325  may be included in the driving circuit unit  320 , and the buffer circuit  333 , the buffer capacitor Cn and the integration circuit  337  may be included in the sensing circuit unit  330  of  FIG. 11 . The capacitor Cm of  FIG. 10  may correspond to node capacitors C 11  to Cmn of  FIG. 4 . 
     The driving circuit  325  may include switches SW 1  and SW 2 , and the switch SW 1  may be connected between a first node of the node capacitor Cm and the supply voltage terminal VDD. The switch SW 2  may be connected between the first node of the node capacitor Cm and the common-mode voltage terminal VCM. The switches SW 1  and SW 2  may deliver driving signals to the node capacitor Cm such that one is closed while the other is open. 
     The buffer circuit  333  may include an operational amplifier OPA 1 , a feedback capacitor CF 1 , and switches SW 3  to SW 7 . The switch SW 3  may be connected between the second node of the node capacitor Cm and the inverting input terminal of the operation amplifier OPA 1 , and the switch SW 4  may be connected between the second node of the node capacitor Cm and the terminal of the common-mode voltage VCM. The switch SW 5  may be connected between the inverting input terminal of the operational amplifier OPA 1  and the output thereof, the switch SW 6  may be connected between the second node of the node capacitor Cm and the non-inverting input terminal of the operational amplifier OPA 1 , and the switch SW 7  may be connected between the non-inverting input terminal of the operational amplifier OPA 1  and the terminal of the common-mode voltage VCM. The feedback capacitor CF 1  may be connected in parallel to the fifth switch SW 5 , and the non-inverting input terminal of the operational amplifier OPA 1  may be connected to the terminal of the common-mode voltage VCM. 
     By the switching operations of the switches SW 1  and SW 7 , a predetermined voltage is delivered to the node capacitor Cm, and by the switching operation of the switches SW 2  to SW 7 , the charged stored in the node capacitor Cm may be output at the output terminal of the operational amplifier OPA 1  as the output voltage V bout . 
     The first node of the buffer capacitor Cn may be connected to the output terminal of the operational amplifier OPA 1 , and the buffer capacitor Cn may be charge or discharged depending on the amplitude and polarity of the output voltage V bout . 
     The integration circuit  337  may include an operational amplifier OPA 2 , a feedback capacitor CF 2 , and switches SW 8  to SW 10 . The switch SW 8  may be connected between the second node of the buffer capacitor Cn and the inverting input terminal of the operation amplifier OPA 2 , and the switch SW 9  may be connected between the second node of the buffer capacitor Cn and the common-mode voltage terminal VCM. The switch SW 10  may be connected between the inverting input terminal of the operational amplifier OPA 2  and the non-inverting input terminal thereof, and the feedback capacitor CF 2  may be connected in parallel to the switch SW 10 . The non-inverting input terminal of the operational amplifier OPA 2  may be connected to the common-mode voltage terminal VCM. 
     By the switching operations of the switches SW 8  and SW 9 , the charged stored in the buffer capacitor Cn may be output at the output terminal of the operational amplifier OPA 2  as non-inverted output voltage V intout . 
       FIG. 11  is a diagram for illustrating the operation of a touch sensing device in a normal touch mode according to an exemplary embodiment of the present disclosure. Specifically,  FIG. 11  illustrates clock signals applied to the switches SW 1  to SW 9  and output voltages, in which the switches are turned on when a clock signal of high level is applied thereto and are turned off when a clock signal of low level is applied thereto. In  FIG. 11 , V bout  represents the output voltage from the operational amplifier OPA 1  in the buffer circuit  333 , and V intout  represents the output voltage from the operational amplifier OPA 2  in the integration circuit  337 . In the normal touch mode, the switch SW 6  is turned off while the switch SW 7  is turned on, and thus the switch SW 6  and the switch SW 7  will not be described in detail. 
     In the following, the operation of the touch sensing device according to an embodiment of the present disclosure will be described in detail with reference to  FIGS. 10 and 11 . 
     In section 1, the switches SW 1 , SW 3  and SW 8  are turned on while the switches SW 2 , SW 4  and SW 9  are turned off, such that charges which are stored in the capacitor Cm in the buffer circuit unit with the voltage equal to VDD−VCM are non-inverted and integrated to be output. The output voltage V bout1  output from the operational amplifier OPA 1  in the buffer circuit  333  during section 1 may expressed as Mathematical Expression 1. Where the value of the common voltage VCM is equal to VDD/2, and V noise1  denotes the magnitude of noise introduced in section 1. 
     
       
         
           
             
               
                 
                   
                     Vbout 
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                     VCM 
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                         Cm 
                         
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                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                         
                       
                       * 
                       
                         ( 
                         
                           VDD 
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                           VCM 
                           - 
                           
                             Vnoise 
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                     Mathematical 
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     At this time, charges are stored in the buffer capacitor Cn with the voltage equal to V bout1 −VCM, and the charges stored in the buffer capacitor Cn may be integrated through the integration circuit  337  to then be output. The increment ΔVintout1 in the non-inverted output voltage V intout  from the integration circuit  337  during section 1 may be expressed as Mathematical Expression 2: 
     
       
         
           
             
               
                 
                   
                     Δ 
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                     Mathematical 
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                     ⁢ 
                     Expression 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     2 
                   
                   ] 
                 
               
             
           
         
       
     
     In section 2, the switches SW 1 , SW 4 , SW 5 , and SW 9  are turned on while the switches SW 2 , SW 3 , and SW 8  are turned off. The switches SW 1  and SW 4  are turned on so that charges are stored in the node capacitor Cm with voltage equal to VDD−VCM, and the switch SW 5  is turned on so that the operational amplifier OPA 1  is reset and the operation amplifier OPA 1  outputs common-mode voltage VCM. The switch SW 8  may be turned off so that the output voltage V intout  from the integration circuit  337  may be hold. 
     In section 3, the switches SW 2 , SW 3  and SW 9  are turned on while the switches SW 1 , SW 4 , SW 5  and SW 8  are turned off. The switches SW 2  and SW 3  are turned on so that the charges stored in the capacitor Cm with the voltage equal to VDD−VCM are released, and the output voltage V bout2  output from the operational amplifier OPA 1  may be expressed as Mathematical Expression 3: 
     
       
         
           
             
               
                 
                   
                     Vbout 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     2 
                   
                   = 
                   
                     VCM 
                     + 
                     
                       
                         Cm 
                         
                           CF 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                         
                       
                       * 
                       
                         ( 
                         
                           VCM 
                           + 
                           
                             Vnoise 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             2 
                           
                         
                         ) 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Mathematical 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     Expression 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     3 
                   
                   ] 
                 
               
             
           
         
       
     
     Where V noise2  denotes noise introduced in section 3. 
     In addition, in section 3, the switch SW 8  is turned off, the switch SW 9  is turned on, such that the output voltage V intout  from the integration circuit unit is hold, and charges are stored in the buffer capacitor Cn with voltage equal to V bout2 −VCM. 
     In section 4, the switches SW 2 , SW 4 , SW 5 , and SW 8  are turned on while the switches SW 1 , SW 3 , and SW 9  are turned off. The switch SW 5  is turned on, and the operational amplifier OPA 1  is reset, such that the operational amplifier OPA 1  output common-mode voltage VCM. At this time, the switch SW 8  is turned on and the switch SW 9  is turned off, such that the charges are stored in the buffer capacitor Cn with voltage equal to V bout2 −VCM are released. At this time, the increment ΔVintout2 in the output voltage V intout  from the integration circuit  337  may be expressed as Mathematical Expression 4. 
     
       
         
           
             
               
                 
                   
                     Δ 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     Vintout 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     2 
                   
                   = 
                   
                     
                       Cm 
                       
                         CF 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         1 
                       
                     
                     ⁢ 
                     
                       Cn 
                       
                         CF 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         2 
                       
                     
                     * 
                     
                       ( 
                       
                         VCM 
                         + 
                         
                           Vnoise 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Mathematical 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     Expression 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     4 
                   
                   ] 
                 
               
             
           
         
       
     
     In summary, during one period in which the switches SW 1  and SW 2  are once switched on/off and off/on, the increment ΔVintout in the output voltage integrated in the integration circuit  337  may be expressed as Mathematical Expression 5: 
     
       
         
           
             
               
                 
                   
                     Δ 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     Vintout 
                   
                   = 
                   
                     
                       
                         Δ 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         Vintout 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         1 
                       
                       + 
                       
                         Δ 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         Vintout 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         2 
                       
                     
                     = 
                     
                       
                         
                           
                             Cm 
                             
                               CF 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               1 
                             
                           
                           ⁢ 
                           
                             Cn 
                             
                               CF 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               2 
                             
                           
                           ⁢ 
                           
                             ( 
                             
                               VDD 
                               - 
                               VCM 
                               - 
                               
                                 Vnoise 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                               
                             
                             ) 
                           
                         
                         + 
                         
                           
                             Cm 
                             
                               CF 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               1 
                             
                           
                           ⁢ 
                           
                             Cn 
                             
                               CF 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               2 
                             
                           
                           ⁢ 
                           
                             ( 
                             
                               VCM 
                               + 
                               
                                 Vnoise 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 2 
                               
                             
                             ) 
                           
                         
                       
                       = 
                       
                         
                           Cm 
                           
                             CF 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             1 
                           
                         
                         ⁢ 
                         
                           Cn 
                           
                             CF 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             2 
                           
                         
                         * 
                         
                           ( 
                           
                             VDD 
                             + 
                             
                               ( 
                               
                                 
                                   Vnoise 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   2 
                                 
                                 - 
                                 
                                   Vnoise 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   1 
                                 
                               
                               ) 
                             
                           
                           ) 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Mathematical 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     Expression 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     5 
                   
                   ] 
                 
               
             
           
         
       
     
     If the V noise1  is equal to the V noise2 , it can be seen that common noise is removed in the resulting output from the integration circuit  337 . That is, while one period of a driving signal is applied to the capacitor Cm by the switches SW 1  and SW 2 , integration is performed twice in the positive and negative regions, such that the common noise may be efficiently removed. 
       FIG. 12  is a diagram for illustrating the operation of a touch sensing device in a proximity touch mode according to an exemplary embodiment of the present disclosure. 
     Specifically,  FIG. 12  illustrates clock signals applied to the switches SW 1  to SW 9  and output voltages, in which the switches are turned on when a clock signal of high level is applied thereto and are turned off when a clock signal of low level is applied thereto. In  FIG. 12 , V bout  represents the output voltage from the operational amplifier OPA 1  in the buffer circuit  333 , and V intout  represents the output voltage from the operational amplifier OPA 2  in the integration circuit  337 . 
     This exemplary embodiment relates to the proximity touch mode, in which clock signals of  FIG. 12  may be applied to the driving circuit  325 , the buffer circuit  333 , and the integration circuit  337  which are described with respect to  FIGS. 8 and 9 , among the plurality of driving circuits  325 , the buffer circuit  333 , and the integration circuit  337  included in the driving circuit unit  320  and the sensing circuit unit  330  of  FIG. 4 . 
     In the proximity touch mode, since switches SW 3 , SW 4  and SW 7  are turned off and the switches SW 5  and SW 6  are turned on, the buffer circuit  333  may equivalently represented by the voltage follower shown in  FIG. 13 . Since the buffer circuit  333  may be equivalently represented by the voltage follower, the voltage signal applied to the non-inverting input terminal of the first operational amplifier OPA 1  may be output at the output terminal losslessly, and accordingly the components of the parasitic capacitances Cxg and Cyg may be integrated by the integration circuit  337  losslessly. 
     In the above-description, each of the second electrodes Y 1  to Ym has the sensing circuit unit  330  including the buffer circuit  333 , the buffer capacitor Cn, and the integration circuit  337  connected thereto. In addition to this, the voltage follower, the buffer capacitor and the integration circuit for acquiring sensing signals for proximity touch may be connected to a portion of electrodes disposed near the ends of the first and second electrodes. 
     In the following, the operation of the touch sensing device according to an embodiment of the present disclosure will be described in detail with reference to  FIGS. 10 and 12 . 
     In section 1, the switches SW 2  and SW 9  are turned on, the switches SW 1  and SW 8  are turned off, such that the voltage V bout  output from the buffer circuit  333  is 0 V, and charges are stored in the buffer capacitor Cn with the voltage equal to Cn*VCM. 
     In section 2, the switches SW 1  and SW 8  are turned on, the switches SW 2  and SW 9  are turned off, such that voltage V bout  that is applied to the non-inverting input terminal of the buffer circuit  333  to be output to the operational amplifier OPA 2  is equal to (Cm/(Cm+Cg))*VDD. The parasitic capacitance Cg may correspond to the parasitic capacitance Cxg illustrated in  FIGS. 6 and 7  when a change in capacitance is detected from the first electrodes and may correspond to the parasitic capacitance Cyg illustrated in  FIGS. 6 and 7  when a change in capacitance is detected from the second electrodes. 
     At this time, charges are stored in the buffer capacitor Cn with a voltage equal to Cn*(VCM+V bout ), the voltage V intout  output from the operational amplifier OPA 2  is equal to (Cn*V bout )/CF 2 . 
     That is, the resulting output voltage V intout  during one period may be expressed as Mathematical Expression 6 below: Sine there are components for the parasitic capacitance Cg in V intout  a proximity touch can be precisely determined. 
     
       
         
           
             
               
                 
                   Vintout 
                   = 
                   
                     
                       Cn 
                       
                         CF 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         2 
                       
                     
                     * 
                     
                       Cm 
                       
                         Cm 
                         + 
                         Cg 
                       
                     
                     * 
                     VDD 
                   
                 
               
               
                 
                   [ 
                   
                     Mathematical 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     Expression 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     6 
                   
                   ] 
                 
               
             
           
         
       
     
     As set forth above, according to exemplary embodiments of the present disclosure, a proximity touch that is not made directly to a touch panel can be precisely detected. 
     While exemplary embodiments have been shown and described above, it will be apparent to those skilled in the art that modifications and variations could be made without departing from the spirit and scope of the present disclosure as defined by the appended claims.