Patent Publication Number: US-2022214794-A1

Title: Touch sensing system and display system including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a Continuation application of U.S. application Ser. No. 16/822,685 filed Mar. 18, 2020, which claims priority from Korean Patent Application No. 10-2019-0086899 filed on Jul. 18, 2019 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Methods and apparatuses consistent with example embodiments relate to a touch sensing system, and a display system including the same. 
     Touch and display driver integration (TDDI) refers to a technology that integrates a touch integrated circuit (IC) and a display driver IC (DDI) in a single chip. 
     A capacitive touch sensing device may recognize a touch input using a change in capacitance. The capacitive method may be a self-capacitive method or a mutual capacitive method. The self-capacitive method may sense a change in capacitance occurring in an electrode for touch recognition, and the mutual capacitive method may sense a change in capacitance generated between a driving electrode receiving separate driving signals and a sensing electrode. 
     SUMMARY 
     One or more example embodiments provide a touch sensing system capable of performing proximity sensing for sensing proximity of an object without using a separate proximity sensor. 
     According to an aspect of an embodiment, a touch sensing system includes a touch panel including touch sensors arranged in a grid along a row direction and a column direction that crosses the row direction; a touch controller including at least one transmission circuit configured to transmit an output voltage signal to the touch sensors, and at least one reception circuit configured to detect an input voltage signal from the touch sensors; a switching circuit configured to selectively connect each of the touch sensors to the at least one transmission circuit and the at least one reception circuit in accordance with an operation mode; and a plurality of routing wires configured to electrically connect each of the touch sensors to the switching circuit. The switching circuit is further configured to: connect each of the touch sensors to the at least one reception circuit in a touch mode, the touch mode sensing a touch of an object, and connect a first portion of the touch sensors to the at least one reception circuit and a second portion of the touch sensors to the at least one transmission circuit in a proximity mode, the proximity mode sensing proximity of the object. 
     According to an aspect of an embodiment, a touch sensing system includes a touch panel including touch sensors arranged in a grid along a row direction and a column direction that crosses the row direction; and a touch controller configured to electrically connect at least two touch sensors adjacent to each other, among the touch sensors, and connect the at least two touch sensors to a proximity sensing receiver. The proximity sensing receiver is configured to sense proximity of an object using the at least two touch sensors. 
     According to an aspect of an embodiment, a display system includes a display panel including touch sensors arranged in a grid along a row direction and a column direction that crosses the row direction; and a controller configured to control the display panel to sense a touch of an object using the touch sensors in a touch mode and sense proximity of the object using a portion of the touch sensors in a proximity mode. The controller is further configured to control the display panel to selectively activate the touch mode and the proximity mode based on a first event occurring. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The above and other aspects, features, and 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 block diagram illustrating a display system according to an embodiment. 
         FIG. 2  is a view illustrating an operation of a display system according to an embodiment. 
         FIG. 3  is a cross-sectional view of a touch display panel according to an embodiment. 
         FIG. 4  is a block diagram illustrating a touch sensing system according to an embodiment. 
         FIG. 5  is a block diagram illustrating an embodiment of an in-cell type touch display panel according to an embodiment. 
         FIGS. 6 and 7  are views illustrating an operation of sensing a touch input according to an embodiment. 
         FIG. 8  is a view illustrating a proximity sensing operation according to an embodiment. 
         FIG. 9  is a view illustrating a touch sensing system according to an embodiment. 
         FIGS. 10 and 11  are views illustrating a touch sensing system according to an embodiment. 
         FIGS. 12 and 13A, 13B and 13C  are views illustrating a proximity sensing operation of a touch sensing system according to an embodiment. 
         FIGS. 14A, 14B, 14C, 14D, 14E, 14F and 14G  are views illustrating a proximity sensing operation of a touch sensing device according to an embodiment. 
         FIG. 15  is a flowchart illustrating a method of operating a display system according to an embodiment. 
         FIGS. 16A, 16B, 16C and 16D  are views illustrating a method of operating a display system according to an embodiment. 
         FIG. 17  is a view illustrating a display system equipped with a touch sensing device according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments will be described with reference to the accompanying drawings. The present disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Like reference numerals refer to like elements throughout this application. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. For example, the expression, “at least one of a, b, and c,” should be understood as including only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c. 
       FIG. 1  is a block diagram illustrating a display system according to an embodiment. Referring to  FIG. 1 , a display system  10  may include a touch display panel  100 , a touch display driving integrated circuit (touch DDI) chip  200 , and a host  300 . The display system  10  may be a touch display system having a touch function. 
     The touch display panel  100  may include a touch panel TP therein. The touch panel TP may include a plurality of touch sensors TS. As an example, the touch sensors TS may be provided by a common electrode that is included in the touch display panel  100  and receives a common voltage VCOM for driving the display, a separate electrode different from the common electrode, or the like. For example, the plurality of touch sensors TS may be arranged in a grid along a row direction ROW and a column direction COL crossing the row direction ROW. 
     The display system  10  may be an in-cell type touch display system or an on-cell type touch display system. 
     In an on-cell type touch display panel  100 , a plurality of touch sensors TS may be arranged on a display panel. For example, in the on-cell type touch display system, touch sensors TS may be provided by separate electrodes disposed on an upper substrate of the display panel. 
     In an in-cell type touch display panel  100 , a plurality of pixels and a plurality of touch sensors TS may be arranged within the same panel. For example, in the in-cell type touch display system, touch sensors TS may be mounted in the touch display panel  100 , together with the plurality of pixels. For example, a touch sensor TS may be provided by a common electrode for driving the plurality of pixels. 
     A display system  10 , including the in-cell type touch display panel  100 , may output an image frame according to a predetermined frame period. In an embodiment, one frame period may include a display period for displaying image information, and a touch period for sensing a touch input of an object. 
     During the display period, the touch sensors TS may be used as a common electrode for driving a plurality of pixels. Therefore, a common voltage may be applied to the touch sensors TS during the display period. 
     During the touch period, the touch sensors TS may be used as an electrode for sensing a touch input. Therefore, a touch sensing signal, corresponding to the change in capacitance may be output from the touch sensor TS during the touch period. 
     The touch display panel  100  may include a display panel such as a liquid crystal display panel, an organic light emitting display panel, or the like, but is not limited thereto. 
     The touch display panel  100  may be driven by the touch DDI chip  200 . The touch DDI chip  200  may be connected to the touch display panel  100  through gate lines GL, data lines DL, and touch sensing lines TSL. The touch DDI chip  200  may include a display driving circuit  210  and a touch controller  220 . 
     The display driving circuit  210  may generate signals for driving a plurality of pixels. The display driving circuit  210  may be connected to the plurality of pixels through the gate lines GL and the plurality of data lines DL, respectively. The display driving circuit  210  may provide a gate signal for driving the gate lines GL of the touch display panel  100 . The display driving circuit  210  may provide an image signal to each of the plurality of pixels through the data lines DL. 
     The touch controller  220  may generate signals for sensing a touch input. The touch controller  220  may be connected to the touch sensors TS through the touch sensing lines TSL, respectively. The touch controller  220  may acquire a touch sensing signal corresponding to a change in capacitance occurred in the touch sensors TS through the touch sensing lines TSL. The touch controller  220  may sense the touch input using the touch sensing signal. 
     According to an embodiment, the touch controller  220  and the display driving circuit  210  may be implemented as a single semiconductor chip. However, embodiments are not limited thereto, and the touch controller  220  and the display driving circuit  210  may be implemented as separate semiconductor chips. 
     The touch DDI chip  200  may communicate with the host  300 . For example, the host  300  may be a main processor that controls the entire operation of an electronic device on which the touch display panel  100  and the touch DDI chip  200  are mounted, and may implemented as an application processor (AP), a central processing unit (CPU), or the like. The touch DDI chip  200  may control display of an image on the touch display panel  100  according to data received from the host  300 . Also, the touch DDI chip  200  may provide the host  300  with information on the touch input sensed by the touch display panel  100 . 
     According to an embodiment, the display system  10  may provide a proximity sensing function for sensing proximity of an object not in direct contact with the touch display panel  100 . For example, in an embodiment, the proximity sensing function may be implemented by electrically connecting and grouping at least a portion of the touch sensors included in the touch display panel  100 . Because the proximity sensing function is implemented without a proximity sensor, a full screen display capable of displaying an image the entire screen of an electronic device may be implemented. 
       FIG. 2  is a view illustrating an operation of a display system according to an embodiment. Referring to  FIG. 2 , a touch sensor TS may be disposed on a touch display panel  100 , and a plurality of pixels may be disposed below one touch sensor TS. For example, one touch sensor TS may have a larger area than one pixel (e.g., PIX 1 ). The touch sensor TS may be one among a plurality of touch sensors. 
     A first pixel PIX 1  may include a first pixel electrode PE 1  and a transistor TR. In a display period, one touch sensor TS may be used as a common electrode for driving the plurality of pixels. The image information may be displayed according to a difference in voltage between the one touch sensor TS used as the common electrode and pixel electrodes PE 1 , PE 2 , and PE 3 . 
     The transistor TR may be a thin film transistor (TFT). The transistor TR of the first pixel PIX 1  may be connected to a gate line GL and a data line DL. A source of the transistor TR may be connected to a touch DDI chip  200  through the data line DL, a drain of the transistor TR may be connected to the first pixel electrode PE 1 , and a gate of the transistor TR may be connected to the touch DDI chip  200  through the gate line GL. 
     A storage capacitor Cs and a liquid crystal layer may be disposed between the first pixel electrode PE 1  and the touch sensor TS. A liquid crystal capacitor Clc may be formed between the first pixel electrode PE 1  and the touch sensor TS by the liquid crystal layer. The liquid crystal capacitor Clc may be connected to the storage capacitor Cs in parallel. The storage capacitor Cs may serve to maintain a voltage charged in the liquid crystal capacitor Clc in a state in which the gate of the transistor TR is turned off. 
     During the display period, the touch DDI chip  200  may provide a common voltage to a touch sensing line TSL connected to the touch sensor TS, may provide a gate signal to a gate line GL, and may provide an image signal to a data line DL. For example, the gate signal may be a signal for controlling a turn-on or a turn-off of the transistor TR included in the pixel PIX 1 . 
     For example, in the first pixel PIX 1 , an electric field may be formed by the image signal received through the data line DL and the common voltage of the touch sensor TS. An arrangement of liquid crystal directors of the liquid crystal layer may be changed by the electric field. According to the arrangement of the liquid crystal directors, light incident on the liquid crystal layer may be penetrated or blocked. Therefore, the display system  10  may display image information through the touch display panel  100 . 
     During the touch period, the touch DDI chip  200  may receive a touch sensing signal output from the touch sensor TS through the touch sensing line TSL. In this case, when an inputting object such as a portion of a user&#39;s body touches the touch display panel  100  or approaches the touch display panel  100 , capacitance (Ct) may be generated between the touch sensor TS and the inputting object. As the capacitance (Ct) is generated, the touch sensing signal output from the touch sensor TS may be changed. The touch DDI chip  200  may sense a change in the touch sensing signal output from the touch sensor TS through the touch sensing line TSL. The display system  10  may recognize that the inputting object touches the touch display panel  100  or approaches the touch display panel  100  based on a change in the touch sensing signal. 
       FIG. 3  is a cross-sectional view of a touch display panel according to an embodiment. Referring to  FIG. 3 , a touch display panel  100  may include a transistor TR, a channel region CH, a pixel electrode PE, a liquid crystal layer LC, a touch sensor TS, a color filter CF, a black matrix BM, and a storage capacitor Cs. A liquid crystal capacitor Clc may be formed between the pixel electrode PE and the touch sensor TS by the liquid crystal layer LC. 
     The transistor TR may include a gate electrode GE, a source electrode SE, and a drain electrode DE. The gate electrode GE may be connected to a gate line, and may receive a gate signal from the gate line. The gate signal may control a turn-on or a turn-off of the transistor TR. The source electrode SE may be connected to a data line, may receive an image signal from the data line, and may transmit the received image signal to the drain electrode DE. The drain electrode DE may be connected to the pixel electrode PE. 
     The touch sensor TS may be connected to a touch sensing line, may receive a common voltage from the touch sensing line, and may supply the common voltage to each pixel. In the pixel, an electric field may be formed by the image signal received through the data line and the common voltage applied to the touch sensor TS. An arrangement of liquid crystal directors of the liquid crystal layer LC may be changed by the electric field. According to the arrangement of the liquid crystal directors, light incident on the liquid crystal layer LC may be penetrated or blocked. 
     The color filter CF may be provided to display a color for each pixel. The black matrix BM may serve to distinguish and block light between the color filters CF. 
     In an embodiment, a display system may output a touch sensing signal, corresponding to a change in capacitance occurred in the touch sensor TS, to a touch sensing line. The display system may recognize that an inputting object approaches the touch display panel  100  based on a change in the touch sensing signal. 
       FIG. 4  is a block diagram illustrating a touch sensing system according to an embodiment. Referring to  FIG. 4 , a touch sensing system  10 A may include a touch sensing device  100 A and a touch controller  200 A. The touch sensing device  100 A may include a touch panel  110 A, a switching unit  120 A, and routing wires  130 A. 
     A plurality of touch sensors TS may be arranged on the touch panel  110 A. For example, the touch sensors TS may be arranged in a row direction ROW and a column direction COL crossing the row direction ROW. 
     The touch controller  200 A may include at least one transmission circuit and at least one reception circuit. The at least one transmission circuit may output a voltage signal to the touch sensors TS. The at least one reception circuit may detect the voltage signal from the touch sensors TS. 
     One end of the routing wires  130 A may be connected to each of the touch sensors TS, and the other end of the routing wires  130 A may be connected to the switching unit  120 A. The routing wires  130 A may transfer voltage signals from the plurality of touch sensors TS to the switching unit  120 A or may transfer voltage signals to the plurality of touch sensors TS. 
     The switching unit  120 A may selectively connect each of the touch sensors TS to the at least one of the transmission circuit and the at least one reception circuit in accordance with an operation mode. For example, the switching unit  120 A may connect the touch sensors TS to the at least one reception circuit in a touch mode for sensing direct contact of an object. Depending on an embodiment, in a proximity mode for sensing proximity of an object, the switching unit  120 A may connect a portion of the touch sensors TS to the at least one reception circuit, and a remainder of the touch sensors TS to the at least one transmission circuit. 
     According to an embodiment, the touch sensing device  100 A may be implemented as an in-cell type, and the touch sensing system  10 A may sense a touch input based on a self-capacitive method. Further, in an embodiment, the switching unit  120 A may implement a proximity sensing operation for sensing the proximity of the object by individually controlling routings of the touch sensors TS. 
       FIG. 5  is a block diagram illustrating an embodiment of an in-cell type touch display panel according to an embodiment. Referring to  FIG. 5 , a touch display panel  100  may include polarizers PL 1  and PL 2 , glasses GL 1  and GL 2 , and a display panel DP. 
     In the in-cell type touch display panel  100 , a display panel DP and a touch panel TP for sensing a touch input may be arranged on the same panel. For example, the touch panel TP may be included in a layer CL including the display DP. The in-cell type touch display panel  100  may perform a touch sensing function by using at least a portion of various electrodes provided in the touch display panel  100  as a touch sensor. 
     For example, the touch sensor may receive a common voltage during a display period, and the touch sensor may output a touch sensing signal during a touch period. 
     The layer CL including the display panel DP and the touch panel TP may be disposed between the glasses GL 1  and GL 2 . The polarizers PL 1  and PL 2  may be arranged on the glasses GL 1  and GL 2 , respectively. 
       FIGS. 6 and 7  are views illustrating an operation of sensing a touch input according to an embodiment. Referring to  FIG. 6 , parasitic capacitance (Cp) may be formed between a touch sensor TS and a ground source GND in a touch display panel. 
     In accordance with a touch input by an object OJ, touch capacitance (Ct) may be formed between the touch sensor TS and the object OJ. In a self-capacitive method, the touch input may be sensed by measuring a magnitude of the touch capacitance (Ct) between the touch sensor TS and the object OJ. 
     In  FIG. 7 , a configuration of a reception circuit connected to a touch sensor TS is illustrated. Referring to  FIG. 7 , the reception circuit connected to the touch sensor TS may include a receiver RX and a feedback capacitor Cc. Parasitic capacitance (Cp) may be formed between the touch sensor TS and a ground source GND in a touch display panel. 
     A touch sensing signal from the touch sensor TS may be input to a first input terminal (−) of the receiver RX. Various types of reference voltages (Vref) such as a pulse signal may be input to a second input terminal (+) of the receiver RX. The feedback capacitor Cc may be connected between the first input terminal (−) and an output terminal of the receiver RX. 
     In accordance with a touch input by an object OJ, an electric field may be formed from the touch sensor TS, and touch capacitance (Ct) may be formed between the touch sensor TS and the object OJ. Capacitance of the feedback capacitor Cc may be the sum of the parasitic capacitance (Cp) and the touch capacitance (Ct). 
     When a reference voltage (Vref) having a first magnitude (Va) is input to the second input terminal (+) of the receiver RX, an output voltage (Vout) having a second magnitude (Vb) may be output to the output terminal of the receiver RX according to the touch capacitance Ct. The second magnitude (Vb) may be greater than the first magnitude (Va). The touch controller may sense the touch input in accordance with a difference (ΔV) between the first magnitude (Va) and the second magnitude (Vb). 
     In order for the display system to detect proximity of the object, intensity of an electric field should be strong. Because an area of one touch sensor TS is constant, intensity of an electric field generated by one touch sensor TS may be constant even when an area of the object OJ increases. Therefore, even when the object OJ having a relatively large area approaches the touch sensor TS, an amount of the touch capacitance (Ct) formed between the touch sensor TS and the object OJ may be constant. For example, one touch sensor TS may not sense proximity of the object OJ. 
       FIG. 8  is a view illustrating a proximity sensing operation according to an embodiment. Referring to  FIG. 8 , in a proximity sensing operation, a display system according to an embodiment may group and electrically connect a plurality of touch sensors TS to form a touch sensor group TSG. Touch sensors TS of the touch sensor group TSG may be commonly connected to a proximity sensing receiver for sensing proximity of an object. As a result, an area of the touch sensor group TSG may be greater than the individual touch sensors TS. 
     As an area of the touch sensor group TSG is increased, intensity of an electric field generated by one touch sensor group TSG may increase. This may increase a distance at which the touch sensor TS may sense an object OJ. Therefore, the display system may provide a proximity sensing function for sensing proximity of an object, not in direct contact, by grouping the touch sensors TS into a touch sensor group TSG. 
       FIG. 9  is a view illustrating a touch sensing system according to an embodiment. Referring to  FIG. 9 , a touch sensing system  30  may include touch panel  110 A, switching unit  120 A, and routing wires  130 A. The touch panel  110 A may be one among a plurality of touch panels  110 A. 
     In the touch panel  110 A, touch sensors TS may be arranged in m (m is a natural number of 1 or more) rows and n (where n is a natural number of 1 or more) columns. A plurality of pixels may be arranged under the touch sensor TS. 
     The switching unit  120 A may include n multiplexers MUX 1  to MUXn, n corresponds to the number of columns of the touch sensors TS arranged on the touch panel  110 A. Each of the multiplexers MUX 1  to MUXn may be connected to the touch sensors TS arranged at the same position in a row direction ROW. 
     Specifically, m touch sensors TS arranged in a first column C 1  of the touch panel  110 A may be connected to a first multiplexer MUX 1 . In addition, m touch sensors TS arranged in a second column C 2  of the touch panel  110 A may be connected to a second multiplexer MUX 2 . Further, m touch sensors TS arranged in an n th  column Cn of the touch panel  110 A may be connected to an n th  multiplexer MUXn. 
     Each of the multiplexers MUX 1  to MUXn may be respectively connected to n touch sensing receivers RX 1  to RXm, a proximity sensing receiver PRX, a ground source GND for supplying a ground voltage to the touch sensors TS, a voltage source SG for supplying a predetermined voltage, different from the ground voltage, to the touch sensors TS, and a buffer BF. According to an embodiment, each of the multiplexers MUX 1  to MUXn may be connected to a common voltage source for supplying a common voltage to the touch sensors TS. 
     Each of the touch sensing receivers RX 1  to RXm may be receivers for sensing a touch input by the object, and may receive a touch sensing signal from the touch sensors TS. The proximity sensing receiver PRX may be receivers for sensing proximity of the object, and may receive a touch sensing signal from the touch sensors TS. The proximity sensing receiver PRX may be substantially the same receiver as each of the touch sensing receivers RX 1  to RXm, but may be implemented as different receivers from the touch sensing receivers RX 1  to RXm according to an embodiment. 
     For example, each of the multiplexers MUX 1  to MUXn may transmit the touch sensing signals of the touch sensors TS to the corresponding touch sensing receivers RX 1  to RXm. For example, a touch sensing signal of the touch sensor TS disposed in a region in which the first column C 1  and the first row R 1  cross each other may be transferred to the first touch sensing receiver RX 1 , and a touch sensing signal of the touch sensor TS disposed in a region in which the first column C 1  and an m th  row Rm cross each other may be transferred to an m th  touch sensing receiver RXm. 
     Each of the touch sensing receivers RX 1  to RXm and the proximity sensing receiver PRX may include a first input terminal to receive the touch sensing signal from the touch sensor TS, and a second input terminal to receive a reference voltage. 
     According to an embodiment, each of the multiplexers MUX 1  to MUXn may connect the touch sensors TS to the buffer BF. The buffer BF may supply the reference voltage to the touch sensors TS. 
     According to an embodiment, each of the multiplexers MUX 1  to MUXn may turn off switches connected to each of the touch sensors TS, to float the touch sensors TS. According to an embodiment, each of the multiplexers MUX 1  to MUXn may apply a ground voltage or a predetermined voltage, different from the ground voltage, to each of the touch sensors TS. 
     According to an embodiment, each of the multiplexers MUX 1  to MUXn included in the switching unit  120 A may independently control routing of each of the touch sensors TS disposed on the touch panel  110 A. Therefore, the touch sensing system  30  may electrically connect and group the plurality of touch sensors TS to form a touch sensor group TSG, and may connect the touch sensors TS of the touch sensor group TSG to the proximity sensing receiver PRX in common. 
     The touch sensors TS of the touch sensor group TSG may be connected to the proximity sensing receiver PRX in common, an area of the touch sensor group TSG may be greater than an area of an individual touch sensor TS. As the area of the touch sensor group TSG is increased, an electric field generated by the touch sensor group TSG is greater than an electric field generated by an individual touch sensor TS. When the electric field generated increases, a distance at which the object OJ may be sensed may increase. 
     Therefore, the touch sensors TS of the touch sensor group TSG may serve as a proximity sensor for sensing proximity of the object. 
       FIGS. 10 and 11  are views illustrating a touch sensing system according to an embodiment. In an embodiments described with reference to  FIGS. 10 and 11 , it is assumed that touch sensors TS may be arranged in 32 rows and 18 columns. The number of rows and columns may be variously modified. 
     Referring to  FIG. 10 , a first multiplexer MUX 1  connected to 32 touch sensors TS arranged in a first column C 1  may include 32 sub-multiplexers SUB 1  to SUB 32  corresponding to each of the 32 touch sensors TS. Each of the sub-multiplexers SUB 1  to SUB 32  may be connected to each of the touch sensors TS arranged in the first column C 1 . 
     The first multiplexer MUX 1  may be connected to first to 32 nd  touch sensing receivers RX 1  to RX 32 , a proximity sensing receiver PRX, a ground source GND, a voltage source SG for supplying a predetermined voltage, different from a ground voltage, and a buffer BF. Each of the sub-multiplexers SUB 1  to SUB 32  included in the first multiplexer MUX 1  may be connected to corresponding touch sensors TS, and may be connected to touch sensing receivers corresponding to touch sensors TS, among the touch sensing receivers RX 1  to RX 32 . 
     Each of the sub-multiplexers SUB 1  to SUB 32  may be connected to a corresponding touch sensing receiver among the touch sensing receivers RX 1  to RX 32 , the proximity sensing receiver PRX, the ground source GND, the voltage source SG for supplying a predetermined voltage, different from a ground voltage, and the buffer BF. 
     For example, a first sub-multiplexer SUB 1  may be connected to a first touch sensor TS 1 , the first sub-multiplexer SUB 1  may be connected to a first touch sensing receiver RX 1 , the proximity sensing receiver PRX, the ground source GND, the voltage source SG for supplying a predetermined voltage, different from a ground voltage, and the buffer BF. A second sub-multiplexer SUB 2  may be connected to a second touch sensor TS 2 , and the second sub-multiplexer SUB 2  may be connected to a second touch sensing receiver RX 2 , the proximity sensing receiver PRX, the ground source GND, the voltage source SG for supplying a predetermined voltage, different from a ground voltage, and the buffer BF. A 32 nd  sub-multiplexer SUB 32  may be connected to a 32 nd  touch sensor TS 32 , and the 32 nd  sub-multiplexer SUB 32  may be connected to a 32 nd  touch sensing receiver RX 32 , the proximity sensing receiver PRX, the ground source GND, the voltage source SG for supplying a predetermined voltage, different from a ground voltage, and the buffer BF. 
     Referring to  FIG. 11 , a first sub-multiplexer SUB 1  may include a plurality of switches SW 1  to SW 5 . The first sub-multiplexer SUB 1  may control a turn-on or a turn-off of each of the plurality of switches SW 1  to SW 5  based on a first control signal CTRL 1  output from a touch controller. 
     For example, the first sub-multiplexer SUB 1  may turn on the first switch SW 1  and turn off the remaining switches SW 2  to SW 5  based on the first control signal CTRL 1 . Therefore, a first touch sensor TS 1  may be connected to a first touch sensing receiver RX 1 . 
     According to an embodiment, the first sub-multiplexer SUB 1  may turn on the second switch SW 2  and may turn off the remaining switches SW 1 , SW 3 , SW 4 , and SW 5  based on the first control signal CTRL 1 . Therefore, the first touch sensor TS 1  may be connected to a proximity sensing receiver PRX by the first sub-multiplexer SUB 1 . 
     According to an embodiment, the first sub-multiplexer SUB 1  may turn on the third switch SW 3  and may turn off the remaining switches SW 1 , SW 2 , SW 4 , and SW 5  based on the first control signal CTRL 1 . Therefore, the first touch sensor TS 1  may be connected to a ground source GND by the first sub-multiplexer SUB 1 . 
     According to an embodiment, the first sub-multiplexer SUB 1  may turn on the fourth switch SW 4  and may turn off the remaining switches SW 1 , SW 2 , SW 3 , and SW 5  based on the first control signal CTRL 1 . Therefore, the first touch sensor TS 1  may be connected, by the first sub-multiplexer SUB 1 , to a voltage source SG for supplying a predetermined voltage, different from a ground voltage. 
     According to an embodiment, the first sub-multiplexer SUB 1  may turn on the fifth switch SW 5  and may turn off the remaining switches SW 1 , SW 2 , SW 3 , and SW 4  based on the first control signal CTRL 1 . Therefore, the first touch sensor TS 1  may be connected to a buffer BF by the first sub-multiplexer SUB 1 . 
     According to an embodiment, the first sub-multiplexer SUB 1  may turn off all of the switches SW 1  to SW 5  based on the first control signal CTRL 1 . Therefore, the first touch sensor TS 1  connected to the first sub-multiplexer SUB 1  may be floated. 
     Each of the second to 32 nd  sub-multiplexers SUB 2  to SUB 32  of  FIG. 10  may include the plurality of switches SW 1  to SW 5 , in a similar manner to the first sub-multiplexer SUB 1 . Each of the second to 32 nd  sub-multiplexers SUB 2  to SUB 32  of  FIG. 10  may control routing of the touch sensor TS connected to each of the sub-multiplexers SUB 2  to SUB 32  based on a control signal outputted from the touch controller, in a manner similar to the first sub-multiplexer SUB 1  of  FIG. 11 . 
     In addition, each of the remaining multiplexers MUX 2  to MUX 18  may also include 32 sub-multiplexers, in a manner similar to the first multiplexer MUX 1  of  FIG. 10 . Each of the sub-multiplexers may control the routing of the touch sensor connected to each of the sub-multiplexers based on a control signal output from the touch controller in a manner similar to the sub-multiplexer of  FIG. 11 . 
     Each of the multiplexers MUX 1  to MUXn included in the switching unit  120 A according to an embodiment may independently control the routing of each of the touch sensors TS disposed on the touch panel  110 A. Therefore, the switching unit  120 A may electrically connect and group at least two touch sensors TS, adjacent to each other, among the plurality of touch sensors TS. The switching unit  120 A may implement a proximity sensing function, without a separate proximity sensor, by connecting the grouped touch sensors TS to the proximity sensing receiver PRX in common. 
       FIGS. 12 and 13A to 13C  are views illustrating a proximity sensing operation of a touch sensing system according to an embodiment. 
     Referring to  FIG. 12 , in a touch mode, a switching unit may electrically connect and group at least two touch sensors TS, adjacent to each other, among a plurality of touch sensors TS. The grouped touch sensors TS may be arranged in a first region R 1 - 1  of a touch panel  110 B. 
     In a first embodiment, the touch sensors TS of the first region R 1 - 1  in the touch panel  110 B may perform a proximity sensing function, and each of the touch sensors TS of remaining regions, except for the first region R 1 - 1 , may be floated, may be connected to a touch sensing receiver to sense a touch input, may be connected to a ground source, may be connected to a voltage source for supplying a predetermined voltage, different from a ground voltage, or may be connected to a buffer. 
     In a second embodiment, the touch sensors TS of the first region R 1 - 1  in the touch panel  110 B may perform a proximity sensing function, each of the touch sensors TS of a second region R 1 - 2 , surrounding the first region R 1 - 1 , may be connected to a buffer, and each of the touch sensors TS of remaining regions, except for the first region R 1 - 1  and the second region R 1 - 2 , may be floated, may be connected to a touch sensing receiver to sense a touch input, may be connected to a ground source, may be connected to a voltage source for supplying a predetermined voltage, different from the ground voltage, or may be connected to the buffer. 
     The switching unit may freely form shapes, areas, positions, and states of the grouped touch sensors TS. For example, the switching unit may form shapes of the grouped touch sensors TS in a circle, an ellipse, a polygon, a loop, or the like. 
     As illustrated in  FIG. 12 , the grouped touch sensors TS may be arranged in the first region R 1 - 1  of the touch panel  110 B. According to an embodiment, in the touch panel  110 B, a second region R 1 - 2 , surrounding the first region R 1 - 1 , and remaining regions, except for the first region R 1 - 1  and the second region R 1 - 2 , may be determined, in accordance with control of the switching unit. 
     Each of the touch sensors TS included in the second region R 1 - 2  may be connected to the buffer BF outputting a reference voltage. An electric field radiated from the touch sensors TS of the second region R 1 - 2  may enhance straightness of an electric field radiated from the touch sensors TS of the first region R 1 - 1 . 
     For example, an electric field radiated from the touch sensors TS of the second region R 1 - 2  serves to guard an electric field radiated from the touch sensors TS of the first region R 1 - 1 . Therefore, the second region R 1 - 2  may be a shielding region for the touch sensors TS of the first region R 1 - 1 . 
     Referring to  FIGS. 12 and 13A  together, when a touch controller  200 A scans a fourth column C 4 , all touch sensors TS 1  to TS 32  arranged in the fourth column C 4  may be in a floating state. In this case, all the switches included in each sub-multiplexers SUB 1  to SUB 32  included in a fourth multiplexer MUX 4  may be turned off. 
     Referring to  FIGS. 12 and 13B  together, when the touch controller  200 A scans a fifth column C 5 , the first touch sensor TS 1  disposed in a region in which the fifth column C 5  and a first row R 1  cross each other may be in a floating state. In this case, all the switches included in the first sub-multiplexer SUB 1 , connected to the first touch sensor TS 1 , among the sub-multiplexers SUB 1  to SUB 32  included in a fifth multiplexer MUX 5 , may be turned off. 
     The touch sensors TS 2  to TS 7  arranged in a region in which the fifth column C 5  and second to seventh rows R 2  to R 7  cross each other may guard an electric field radiated from the touch sensors TS of the first region R 1 - 1 . In this case, among the switches included in each of the second to seventh sub-multiplexers SUB 2  to SUB 7 , the switch for controlling connection between each of the second to seventh touch sensors TS 2  to TS 7  and the buffer BF may be turned on. Therefore, the touch sensors TS 2  to TS 7  connected to the second to seventh sub-multiplexers SUB 2  to SUB 7  may be connected to the buffer BF. 
     The remaining touch sensors TS 8  to TS 32  arranged in the fifth column C 5  may be in a floating state. In this case, all of the switches included in each of the remaining sub-multiplexers SUB 8  to SUB 32  may be turned off. 
     Referring to  FIGS. 12 and 13C  together, when the touch controller  200 A scans a sixth column C 6 , the first touch sensor TS 1  disposed in a region in which the sixth column C 6  and the first row R 1  cross each other may be in a floating state. In this case, all the switches included in the first sub-multiplexer SUB 1 , connected to the first touch sensor TS 1 , among the sub-multiplexers SUB 1  to SUB 32  included in a sixth multiplexer MUX 6 , may be turned off. 
     The second and seventh touch sensors TS 2  and TS 7  arranged in a region in which the sixth column C 6  and the second row R 2  and the seventh row R 7  cross each other may guard an electric field radiated from the touch sensors TS of the first region R 1 - 1 . In this case, among the switches included in each of the second and seventh sub-multiplexers SUB 2  and SUB 7 , the switch for controlling connection between each of the second and seventh touch sensors TS 2  to TS 7  and the buffer BF may be turned on. Therefore, the touch sensors TS 2  and TS 7  connected to the second and seventh sub-multiplexers SUB 2  and SUB 7  may be connected to the buffer BF. 
     The third to sixth touch sensors TS 3  to TS 6  arranged in a region in which the sixth column C 6  and the third to sixth rows R 3  to R 6  cross each other may be grouped to perform the proximity sensing function. In this case, among the switches included in each of the third to sixth sub-multiplexers SUB 3  to SUB 6 , a switch for controlling connection between each of the third to sixth touch sensors TS 3  to TS 6  and the proximity sensing receiver PRX, may be turned on. Therefore, the touch sensors TS 3  to TS 6  connected to the third to sixth sub-multiplexers SUB 3  to SUB 6  may be electrically connected and grouped, and the grouped touch sensors TS 3  to TS 6  may be connected to the proximity sensing receiver PRX in common. 
     The remaining touch sensors TS 8  to TS 32  arranged in the sixth column C 6  may be in a floating state. In this case, all of the switches included in the remaining sub-multiplexers SUB 8  to SUB 32  may be turned off. 
       FIGS. 14A to 14G  are views illustrating a proximity sensing operation of a touch sensing device according to an embodiment. Referring to  FIG. 14A , a touch panel  110 C may include a first region R 2 - 1 , a second region R 2 - 2 , and remaining regions, excluding the first region R 2 - 1  and the second region R 2 - 2 . The first region R 2 - 1  may perform a proximity sensing function, and the second region R 2 - 2  may be a shielding region for touch sensors TS of the first region R 2 - 1 . Each touch sensor TS in the remaining regions may be floated, may be connected to a touch sensing receiver to sense a touch input, may be connected to a ground source, may be connected to a voltage source for supplying a predetermined voltage, different from a ground voltage, or may be connected to a buffer. 
     The touch panel  110 C may prevent electromagnetic interference (EMI) by excluding touch sensors TS of a corner portion of the second region R 2 - 2  from the second region R 2 - 2 . 
     Referring to  FIG. 14B , a touch panel  110 D may include a first region R 3 - 1 , a second region R 3 - 2 , a third region R 3 - 3 , and remaining regions, excluding the first region R 3 - 1 , the second region R 3 - 2 , and the third region R 3 - 3 . The second region R 3 - 2  may perform a proximity sensing function, and the first region R 3 - 1  and the third region R 3 - 3  may be shielding regions for touch sensors TS of the second region R 3 - 2 . Each touch sensors TS of the remaining regions may be floated, may be connected to a touch sensing receiver to sense a touch input, may be connected to a ground source, may be connected to a voltage source for supplying a predetermined voltage, different from a ground voltage, or may be connected to a buffer. 
     The touch panel  110 D may further improve sensitivity of proximity sensing by implementing the touch sensors TS performing the proximity sensing function in a loop shape. 
     Referring to  FIG. 14C , a first region R 4 - 1  for performing a proximity sensing function, and a second region R 4 - 2 , a shielding region for touch sensors TS included in the first region R 4 - 1 , may be positioned in a lower end portion of a touch panel  110 E. 
     Referring to  FIG. 14D , a touch panel  110 F may include a first region R 5 - 1  for performing a proximity sensing function, a second region R 5 - 2  that may be a shielding region for touch sensors TS included in the first region R 5 - 1 , a third region R 6 - 1  for performing a proximity sensing function, and a fourth region R 6 - 2  that may be a shielding region for touch sensors TS included in the third region R 6 - 1 . 
     A deviation between a sensing signal output from the first region R 5 - 1  and a sensing signal output from the third region R 6 - 1  may be used to remove a noise of the sensing signals by arranging the first region R 5 - 1  and the third region R 6 - 1 , performing the proximity sensing function in the touch panel  110 F, on left and right sides of the touch panel  110 F. 
     Referring to  FIG. 14E , a touch panel  110 G may include a first region R 7 - 1  for performing a proximity sensing function, a second region R 7 - 2  that may be a shielding region for touch sensors TS included in the first region R 7 - 1 , a third region R 8 - 1  for performing a proximity sensing function, and a fourth region R 8 - 2  that may be a shielding region for touch sensors TS included in the third region R 8 - 1 . 
     The first region R 7 - 1  and the third region R 8 - 1  for performing the proximity sensing function in the touch panel  110 G may be arranged on both upper and lower sides of the touch panel  110 G. 
     Referring to  FIG. 14F , a touch panel  110 H may include a first region R 9 - 1  for performing a proximity sensing function, a second region R 9 - 2  that may be a shielding region for touch sensors TS included in the first region R 9 - 1 , a third region R 10 - 1  for performing a proximity sensing function, and a fourth region R 10 - 2  that may be a shielding region for touch sensors TS included in the third region R 10 - 1 . 
     The first region R 9 - 1  for performing the proximity sensing function in the touch panel  110 H may be disposed on an upper right side of the touch panel  110 H, and the third region R 10 - 1  may be disposed on a lower left side of the touch panel  110 H. 
     Referring to  FIG. 14G , a touch panel  110 I may include a first region R 11 - 1  for performing a proximity sensing function, a second region R 11 - 2  that may be a shielding region for touch sensors TS included in the first region R 11 - 1 , a third region R 12 - 1  for performing a proximity sensing function, and a fourth region R 12 - 2  that may be a shielding region for touch sensors TS included in the third region R 12 - 1 . 
     The first region R 11 - 1  for performing the proximity sensing function in the touch panel  110 I may be disposed on an upper left side of the touch panel  110 I, and the third region R 12 - 1  may be disposed on a lower right side of the touch panel  110 I. 
       FIG. 15  is a flowchart illustrating a method of operating a display system according to an embodiment, and  FIGS. 16A to 16D  are views illustrating a method of operating a display system according to an embodiment. Referring to  FIG. 15  and  FIGS. 16A to 16D  together, a touch mode for displaying an image and sensing a touch input of an object in a display system may be activated (S 110 ). 
     As illustrated in  FIG. 16A , a touch mode is activated in S 110  when an incoming call is received, an answer button  111  and an end button  113  may be displayed on a touch display panel  100 , but the present disclosure is not limited thereto. When a user clicks (or touches) the answer button  111  to answer the incoming call (S 120 ), the display system may activate the touch mode and a proximity mode (S 130 ). 
     The proximity mode may be a mode for sensing proximity to the object. As illustrated in  FIG. 16B , the end button  113  may be displayed on a touch display panel  100  in the proximity mode, but the present disclosure is not limited thereto. In the proximity mode, the display system may electrically connect and group at least two touch sensors adjacent to each other, among the touch sensors included in the display panel. The display system may connect the grouped touch sensors to a proximity sensing receiver. Therefore, the grouped touch sensors may sense proximity to the object. 
     While the touch mode and the proximity mode are activated in S 130 , the display system may determine whether the object exists within a predetermined distance (S 140 ). In S 140 , when the display system senses the object within the predetermined distance, the display system may inactivate the touch mode and may activate only the proximity mode (S 150 ). Because only the proximity mode is activated in the display system, the display system may not display image information, as illustrated in  FIG. 16C , while the user continues the call. Touch sensors  115  grouped in the touch display panel  100  may sense proximity to the object. 
     While the user continues the call, the display system may determine whether the object may be sensed within the predetermined distance (S 160 ). When the display system does not sense the object within the predetermined distance in S 160 , the display system may again activate the touch mode and the proximity mode (S 130 ). 
     When the display system does not sense the object within the predetermined distance in S 140  (“NO” in S 140 ), and the user clicks (or touches) the end button  113  of  FIG. 16B  to end the call (S 180 ), only the touch mode may be activated (S 110 ). A call button  112  and a message button  117  may be displayed on the display panel  100  as illustrated in  FIG. 16D , but the present disclosure is not limited thereto. 
     While the touch mode and the proximity mode are activated in S 130 , when the display system does not sense the object within the predetermined distance (S 140 ), and the user does not click (or touch) the end button to end the call (S 180 ), the display system may continuously activate the touch mode and the proximity mode. 
       FIG. 17  is a view illustrating a display system equipped with a touch sensing device according to an embodiment.  FIG. 17  is a view illustrating a structure of a display system in which a touch sensing device and a display panel are integrated according to an example embodiment. As illustrated in  FIG. 17 , a display system  10 B may include a window glass  400 , a display panel  110 B, and a polarizing plate  500 . 
     Particularly, according to an embodiment, a touch sensing device may be formed integrally with the display panel  110 B by patterning a transparent electrode on an upper plate of the display panel  110 B, instead of being formed on a separate glass substrate. In addition, a switching unit  120 B of the touch sensing device may be formed integrally on the display panel  110 B. 
     When the display panel  110 B is produced in this manner, a touch controller and a display driving circuit may be integrated in a semiconductor chip  200 B. When the touch controller and the display driving circuit are integrated in the single semiconductor chip  200 B, the semiconductor chip  200 B may include a first pad related to touch data, and a second pad related to an image and gradation data. The semiconductor chip  200 B may be connected to the touch sensing device on the display panel  110 B through a conductive line  600 , and the touch controller integrated in the semiconductor chip  200 B may be connected to the switching unit  120 B through the conductive line  600 . 
     The touch controller integrated in the semiconductor chip  200 B may be designed to be connected to the touch sensors through the switching unit  120 B, to reduce the number of pads of the semiconductor chip  200 B. 
     According to an embodiment, a plurality of touch sensors included in a touch panel may be grouped and electrically connected to each other, to perform proximity sensing for sensing proximity of an object. Therefore, according to an embodiment, a full screen display may be implemented. 
     While example embodiments have been illustrated and described above, it will be apparent to those skilled in the art that modifications and variations could be made without departing from the scope as defined by the appended claims.