Abstract:
A sensing device placed in a touch sensing system of a display device includes a selector, a sensing module, and a detection module for determining touch signals generated by the touch sensing system. The selector selects two of the touch signals according to at least one selection control signal. The sensing module comprises a first differential amplifier for comparing the selected touch signals and producing a first differential signal according to first control signals. According to second control signals, the detection module receives the first differential signal, generates an averaged sensing value and a reference value, and compares the averaged sensing value with the reference value to produce a second differential signal. Thereby, the touch sensing system uses the second differential signal to generate the first control signals and the second control signals to control the operation of the touch sensing system.

Description:
BACKGROUND 
     1. Technical Field 
     The disclosure relates to a display device, and more particularly to a sensing device for determining touch signals generated by a touch sensing system of the display device. 
     2. Related Art 
     With the development of technology, touch display devices have been widely used in various electronic devices. A touch display device usually includes a touch input interface, a sensing device, and an analog to digital converter (ADC). The touch input interface provides signal generation units to a user, and thereby the user can use an external object (e.g. a finger) to touch or slide on the surface of the touch display, and then the signal generation units generate touch signals and transmit the touch signals to the sensing device. The sensing device determines whether there is any touch happened to one of sensing lines thereof by comparing one of sensing lines and an adjacent sensing line thereof. Every sensing line corresponds to one of the signal generation unit. 
     The sensing device compares the two signals from the two sensing lines to generate a compared signal which can be converted into continuous signal values by an analog to digital converter (ADC). Moreover, by comparing signal values before and after the touch or approaching of the external object, the position touched or approached by the external object can be determined. 
     SUMMARY 
     The disclosure is a sensing device for determining N touch signals generated by a touch input interface of a touch sensing system, and N is a positive integer. The sensing device includes a selector, a sensing module, and a detection module. The selector selects an ith touch signal and a (i+1)th touch signal from N touch signals according to at least one selection control signal, i is a positive integer from 1 to (N−1). The sensing module connects to the selector in series and comprises a first differential amplifier for comparing the selected touch signals and producing a first differential signal according to first control signals. The detection module connects to the sensing module in series for according to second control signals, generating an averaged sensing value and a reference value from the first differential signal, and comparing the averaged sensing value with the reference value to produce a second differential signal. 
     The disclosure provides a touch sensing system which includes a touch input interface and the sensing device described as above. The touch input interface connects to the selector in series and comprises N sense capacitance circuits for providing the N touch signals to the selector. 
     Moreover, the disclosure provides a display device which includes the touch sensing system described as above. 
     For purposes of summarizing, some aspects, advantages and features of some embodiments of the disclosure have been described in this summary. Not necessarily all of (or any of) these summarized aspects, advantages or features will be embodied in any particular embodiment of the disclosure. Some of these summarized aspects, advantages and features and other aspects, advantages and features may become more fully apparent from the following detailed description and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will become more fully understood from the detailed description given herein below for illustration only, and thus are not limitative of the disclosure, and wherein: 
         FIG. 1  is a block diagram of a device including a touch sensing system according to an embodiment of the disclosure; 
         FIG. 2  is a circuit structure diagram of an embodiment of a sensing module of the implementation of  FIG. 1 ; 
         FIG. 3A  is a circuit structure diagram of an embodiment of a control module of the implementation of  FIG. 1 ; 
         FIG. 3B  is a circuit structure diagram of another embodiment of a control module of the implementation of  FIG. 1 ; 
         FIG. 4  is a timing chart diagram of the touch sensing system of the implementation of  FIG. 1 ; 
         FIG. 5  is a circuit structure diagram of another embodiment of a detection module of the implementation of  FIG. 1 ; and 
         FIG. 6  is a timing chart diagram of the touch sensing system of the implementation of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     The detailed features and advantages of the disclosure are described below in great detail through the following embodiments, the content of which is sufficient for those of ordinary skill in the art to understand the technical content of the disclosure and to implement the disclosure accordingly. Based upon the content of the specification, the claims, and the drawings, those of ordinary skill in the art can easily understand the relevant objectives and advantages of the disclosure. 
     The disclosure provides a touch sensing system which can be implemented in a device or any system having a touch input interface so that the touch sensing system may generate touch signals through the touch input interface when a user touches the touch input interface. 
       FIG. 1  illustrates a block diagram of a touch sensing system to an embodiment of the disclosure. The touch sensing system  10  includes a touch input interface  11 , a sensing device  12 , and a control module  16 . The touch input interface  11  may be a touch panel including N sensing capacitors resulted from N sensing lines (not shown in  FIG. 1 ) which may generate N touch signals when a user touches the touch input interface  11 . The touch signals generated by the touch input interface  11  are transmitted to the sensing device  12 . N is a positive integer. 
     The sensing device  12  includes a selector  13 , a sensing module  14 , and a detection module  15 . As shown in  FIG. 1 , the selector  13  may be a multiplexer, a logic circuit, or the like for selection. The sensing device  12  may select two of the touch signals from the touch input interface  11  from the selection control signals SI(i) and SI(i+1) to determine whether there is any touch happened to one of sensing lines thereof by comparing one of sensing lines and an adjacent sensing line thereof, wherein i is a positive integer from 1 to (N−1). Every sensing line includes a corresponding one of the sensing capacitors. Two of the sensing capacitors generating the selected touch signals are arranged to be adjacent to each other. The sensing module  14  connects to the selector  13  for receiving the selected two touch signals and comparing the two selected touch signals to generate a first differential signal D 1 . The detection module  15  connects to the sensing module  14  for receiving the first differential signal D 1 , and then generates an averaged sensing value and a reference value from the differential amplifier D 1  and compares the averaged sensing value with the reference value to produce a differential signal D 2 . The control module  16  connects to the detection module  15  for receiving the differential signal D 2 , digitizing the differential signal D 2  and generating control signals according to the differential signal D 2 . The detailed structures of the sensing module  14 , the detection module  15 , and the control module  16  are described as below. 
       FIG. 2  illustrates a circuit structure diagram of an embodiment of a sensing module  14  of the implementation of  FIG. 1 . The sensing module  14  includes charge maintenance circuits  141  and  142  and a differential amplifier  143 . The charge maintenance circuit  141  connects to a sense capacitance circuit  111  through a switch SW 7  and connects to the differential amplifier  143 , and this forms a first sensing line. The charge maintenance circuit  142  connects to a sense capacitance circuit  112  through a switch SW 8  and connects to the differential amplifier  143 , and this forms a second sensing line. The sense capacitance circuit  111  includes a capacitor C A  and a switch SW 1  which connects to the capacitor C A  in parallel. The sense capacitance circuit  112  includes a capacitor C B  and a switch SW 2  which connects to the capacitor C B  in parallel. The capacitors C A  and C B  may be configured in the touch input interface  11  as shown in FIG.  1 . The charge maintenance circuit  141  includes a capacitor CK 1  and a switch SW 3  which connects to the capacitor CK 1  in parallel. The charge maintenance circuit  142  includes a capacitor CK 2  and a switch SW 4  which connects to the capacitor CK 2  in parallel. 
     When the switch SW 7  is closed and when the switch SW 3  is opened, the capacitor CK 1  of the charge maintenance circuit  141  receives one of the selected touch signals from the sense capacitance circuit  111  and is charged so as to maintain the touch signal. The charged voltage between the two ends of the capacitor CK 1  becomes the input of the negative end of the differential amplifier  143 . When the switch SW 7  is opened and when the switch SW 3  is closed, the capacitor CK 1  discharges. When the switch SW 8  is closed and when the switch SW 4  is opened, the capacitor CK 2  of the charge maintenance circuit  142  receives the other one of the selected touch signals from the sense capacitance circuit  112  and is charged. The charged voltage between the two ends of the capacitor CK 2  becomes the input of the positive end of the differential amplifier  143 . When the switch SW 8  is opened and when the switch SW 4  is closed, the capacitor CK 2  discharges. Moreover, the charge maintenance circuits  141  and  142  operate synchronously, that is, the switches SW 7  and SW 8  operate synchronously; the switches SW 3  and SW 4  operate synchronously. When receiving the two selected signals simultaneously, the differential amplifier  143  generates the first differential signal D 1 . 
     As shown in  FIG. 1 , the detection module  15  includes an integrator  110 , a voltage buffer  120 , a sensing integrated unit  130 , a differential amplifier  140 , and a charge maintenance circuit  150 . The integrator  110  connects to the sensing module  14  for receiving the differential signal D 1  and generating an averaged sensing value. The voltage buffer  120  connects to the sensing module  14  and connects to the integrator  110  in parallel for receiving the differential signal D 1  and generating a reference value. The use of the voltage buffer  120  is to balance with integrator  110  so that both the outputs of the integrator  110  and the voltage buffer  120  have similar order of charging load to release the input range of the differential amplifier  140 . The sensing integrated unit  130  respectively connects to the integrator  110  in parallel through a switch W 3  and to a negative end of the differential amplifier  140  in parallel through a switch W 5 . The switches W 3  and W 5  are connected in series. The charge maintenance circuit  150  connects to the voltage buffer  120  in parallel through a switch W 4  and to a positive end of the differential amplifier  140  in parallel through a switch W 6 . The switches W 4  and W 6  are connected in series. 
     The sensing integrated unit  130  includes a switch W 1  connecting to (N−1) charge maintenance circuits in parallel, and every charge maintenance circuit includes a capacitor (shown as CS 1 , CS 2  or CS(N−1)) and switch (shown as K 1 , K 2  or K(N−1)) and connects to each other in series. In every charge maintenance circuit, the switch connects to the capacitor in series, and the switch W 1  connects to the capacitors of all charge maintenance circuits in parallel. The charge maintenance circuit  150  includes a switch W 2  and a capacitor CD 1 , the switch W 2  connects to the capacitor CD 1  in parallel. In addition, the control or the selection of the charge maintenance circuits in sensing integrated unit  130  is based on the operation of the switch of every charge maintenance circuit, and the operation of the switches K 1  to K(N−1) is described as below. 
     As shown in  FIG. 1  and  FIG. 4 , the switches K 1  to K(N−1) are controlled by the selection control signal SI(i), that is, the switch K 1  operates according to the control of the selection control signal SI 1  if the value of i is 1. In one embodiment, the value of i is 1, and when the switch W 3  is closed and when the switch K 1  is closed, the capacitor CS 1  is charged by the averaged sensing value from the integrator  110 . When the switch W 5  is closed, the charged voltage formed between the two ends of the capacitor CS 1  becomes the input of the negative end of the differential amplifier  140 . When the switch W 4  is closed, the capacitor CD 1  can be charged by the reference value from the voltage buffer  120 . When the switch W 6  is closed, the charged voltage formed between the two ends of the capacitor CD 1  becomes the input of the positive end of the differential amplifier  140 . The differential amplifier  140  simultaneously receives the averaged sensing value and the reference value to generate a differential signal D 2 . When the switches W 1  and W 2  are closed and when the switches W 3 , W 4 , W 5 , and W 6  are opened, the charged capacitor CS 1  is discharged through the switch W 1  and the charged capacitor CD 1  discharges through the switch W 2 . The switches W 1  and W 2  respectively connect to the ground. 
       FIG. 3A  illustrates a circuit structure diagram of an embodiment of a control module of the implementation of  FIG. 1 . The control module  16  includes a differential amplifier  161 , an analog to digital converter (ADC)  162 , and a timing controller  163 . The differential amplifier  161  connects to the sensing device  12  of  FIG. 1  for receiving the differential signal D 2  and further generating a differential signal according to the differential signal D 2  and a reference voltage Vref for tuning compensation. The reference voltage Vref is used to adjust the ADC  162  tuning range and compensate the offset so the higher resolution can be achieved by the ADC  162  while the differential result of the differential signal D 2  will be concentrated on certain voltage range. It is usually happened when the sensing result is averaged by the integrator  110  of  FIG. 1 . The ADC  162  connects to the differential amplifier  161 , receives the differential signal from the differential amplifier  161 , and converts the differential signal to a digital signal. The timing controller  163  connects to the ADC  162 , enables the ADC  162  through an enable signal En, and generates two groups of control signals based on a clock signal CLK and the digital signal, and the operation timing of the two groups of control signals are described as below. 
     The first group of control signals is referred as the control signals P 1  to P 3  and is used to control the operation of the sensing module  14  and the operation of the touch input interface  11  in  FIG. 2 . The second group of control signals is referred as the control signals Q 1  to Q 4  and is used to control the operation of the detection module  15  in  FIG. 1 . 
     As shown in  FIG. 2 ,  FIG. 3A , and  FIG. 4 , the control signal P 1  of the first group of control signals controls the operation of the switches SW 1 , SW 2 , SW 3 , and SW 4 . When the status of the control signal P 1  becomes a high logic level (ON), the switches SW 1 , SW 2 , SW 3 , and SW 4  are closed. When the status of the control signal P 1  becomes a low logic level (OFF), the switches SW 1 , SW 2 , SW 3  and SW 4  are opened. The control signal P 2  of the first group of control signals controls the operation of the switches SW 5  and SW 6 . When the status of the control signal P 2  becomes ON, the switches SW 5  and SW 6  are closed. When the status of the control signal P 2  becomes OFF, the switches SW 5  and SW 6  are opened. The control signal P 3  of the first group of control signals control the operation of the switches SW 7  and SW 8 . When the status of the control signal P 3  becomes ON, the switches SW 7  and SW 8  are closed. When the status of the control signal P 3  becomes OFF, the switches SW 7  and SW 8  are opened. 
     As shown in  FIG. 1 ,  FIG. 3A , and  FIG. 4 , the control signal Q 1  of the second group of control signals controls the operation of the switch W 1 . When the status of the control signal Q 1  becomes ON, the switch W 1  is closed. When the status of the control signal Q 1  becomes OFF, the switch W 1  is opened. The control signal Q 2  of the second group of control signals controls the operation of the switch W 2 . When the status of the control signal Q 2  becomes ON, the switch W 2  is closed. When the status of the control signal Q 2  becomes OFF, the switch W 2  is opened. The control signal Q 3  of the second group of control signals controls the operation of the switches W 3  and W 4 . When the status of the control signal Q 3  becomes ON, the switches W 3  and W 4  are closed. When the status of the control signal Q 3  becomes OFF, the switches W 3  and W  4  are opened. When the status of the control signal Q 4  becomes ON, the switches W 5  and W 6  are closed. When the status of the control signal Q 4  becomes OFF, the switches W 5  and W 6  are opened. 
       FIG. 5  illustrates a circuit structure diagram of another embodiment of a detection module of the implementation of  FIG. 1 . The detection module  25  includes an integrator  210 , a voltage buffer  220 , a sensing integrated unit  230 , a differential amplifier  240 , and a charge maintenance circuit  250 . The integrator  210  connects to the sensing module  14  of  FIG. 1  for receiving the differential signal D 1  and generating an averaged sensing value. The voltage buffer  220  connects to the sensing module  14  of  FIG. 1  and connects to the integrator  210  in parallel for receiving the differential signal D 1  and generating a reference value. The use of the voltage buffer  220  is to balance with integrator  210  so that both the outputs of the integrator  210  and the voltage buffer  220  have similar order of charging load to release the input range of the differential amplifier  240 . 
     The sensing integrated unit  230  connects to the integrator  210  in parallel through a switch W 9  and connects to a negative end of the differential amplifier  240  in parallel through a switch W 11 . The switches W 9  and W 11  are connected in series. The charge maintenance circuit  250  connects to the voltage buffer  220  in parallel through a switch W 10  and connects to a positive end of the differential amplifier  240  in parallel through a switch W 12 . The switches W 10  and W 12  are connected in series. The sensing integrated unit  230  includes a switch W 7  and a capacitor CI (a charge maintenance circuit) and the switch W 7  connects to the capacitor CI in parallel. The charge maintenance circuit  250  includes a switch W 8  and a capacitor CD 2 , and the switch W 8  connects to the capacitor CD 2  in parallel. 
     When the switch W 9  is closed, the capacitor CI is charged by the averaged sensing value from the integrator  210 . When the switch W 11  is closed, the charged voltage formed between the two ends of the capacitor CI becomes the input of the negative end of the differential amplifier  240 . When the switch W 10  is closed, the capacitor CD 2  is charged by the reference value from the voltage buffer  220 . When the switch W 12  is closed, the charged voltage formed between the two ends of the capacitor CD 2  becomes the input of the positive end of the differential amplifier  240 . The differential amplifier  240  simultaneously receives the averaged sensing value and the reference value to generate a differential signal D 2 . When the switches W 7  and W 8  are closed and when the switches W 9 , W 10 , W 11 , and W 12  are opened, the charged capacitor CI discharges through the switch W 7 , and the charged capacitor CD 2  discharges through the switch W 8  which connects to the ground. In addition, the operation of the switches W 7  and W 8  is based on the reset signal Re which is provided by the control module  16  of  FIG. 1  and will be described as below. 
       FIG. 3B  illustrates a circuit structure diagram of another embodiment of a control module of the implementation of  FIG. 1 . The control module  26  includes a differential amplifier  261 , an ADC  262 , and a timing controller  263 . The differential amplifier  261  connects to the sensing device  12  of  FIG. 1  for receiving the differential signal D 2  and further generating a differential signal according to the differential signal D 2  and a reference voltage Vref for tuning compensation. The reference voltage Vref is used to adjust the ADC  162  tuning range and compensate the offset so the higher resolution can be achieved by the ADC  162  while the differential result of the differential signal D 2  will be concentrated on certain voltage range. It is usually happened when the sensing result is averaged by the integrator  210  of  FIG. 5 . The ADC  262  connects to the differential amplifier  261 , receives the differential signal from the differential amplifier  261 , and coverts the differential signal to a digital signal. The timing controller  263  connects to the ADC  262 , enables the ADC  262  through an enable signal En, and generates two groups of control signals based on a clock signal CLK. The operation timing of the two groups of control signals are described as below. 
     The first group of control signals is referred as the control signals P 4  to P 6  and is used to control the operation of the sensing module  14  and of the touch input interface  11  in  FIG. 2 . The second group of control signals is referred as the control signals Q 5  to Q 7  and is used to control the operation of the detection module  25  in  FIG. 5 . 
     As shown in  FIG. 2 ,  FIG. 3B ,  FIG. 5 , and  FIG. 6 , the control signal P 4  of the first group of control signals controls the operation of the switches SW 1 , SW 2 , SW 3 , and SW 4 . When the status of the control signal P 4  becomes ON, the switches SW 1 , SW 2 , SW 3 , and SW 4  are closed. When the status of the control signal P 4  becomes OFF, the switches SW 1 , SW 2 , SW 3 , and SW 4  are opened. The control signal P 5  of the first group of control signals controls the operation of the switches SW 5  and SW 6 . When the status of the control signal P 5  becomes ON, the switches SW 5  and SW 6  are closed. When the status of the control signal P 2  becomes OFF, the switches SW 5  and SW 6  are opened. The control signal P 6  of the first group of control signals control the operation of the switches SW 7  and SW 8 . When the status of the control signal P 6  becomes ON, the switches SW 7  and SW 8  are closed. When the status of the control signal P 6  becomes OFF, the switches SW 7  and SW 8  are opened. 
     As shown in  FIG. 3B ,  FIG. 5 , and  FIG. 6 , the control signal Q 5  of the second group of control signals controls the operation of the switch W 8 . When the status of the control signal Q 5  becomes ON, the switch W 8  is closed. When the status of the control signal Q 5  becomes OFF, the switch W 8  is opened. The control signal Q 6  of the second group of control signals controls the operation of the switches W 9  and W 10 . When the status of the control signal Q 6  becomes ON, the switches W 9  and W 10  are closed. When the status of the control signal Q 6  becomes OFF, the switch W 9  and W 10  are opened. The control signal Q 7  of the second group of control signals controls the operation of the switches W 11  and W 12 . When the status of the control signal Q 7  becomes ON, the switches W 11  and W 12  are closed. When the status of the control signal Q 7  becomes OFF, the switches W 11  and W 12  are opened. Moreover, the reset signal Re controls the operation of the switch W 7 . When the status of the reset signal Re becomes ON in the beginning of an operation cycle of the touch sensing system  10 , the switch W 7  is closed. When the status of the reset signal Re becomes OFF, the switch W 7  is opened. 
     Accordingly, through the operation process described as above, the touch sensing system can achieve the purpose of sensing the touch from a user and of determining the position concerning to the touch. 
     The disclosure may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.