JP2014164607A - Electrostatic capacity type touch sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic capacity type touch sensor with a simple configuration which utilizes capacitive coupling between a touch electrode and a finger of a person.SOLUTION: A touch sensor element 1 includes: a touch electrode 2 that generates capacity between the ground and the same; and a touch detector 10 the input end of which is connected to the touch electrode 2. The touch detector 10 has an amplifier 11 which includes an input terminal connected to the input end of the touch detector 10 and the output terminal connected to the output end of the touch detector 10. An equalization switch SW1 performs ON/OFF operation to switch electrical connect/non-connect between the input terminal and the output terminal of the amplifier 11.

Description

  The present disclosure relates to a capacitive touch sensor that electrically detects contact.

  In recent years, with the development of portable devices, the technological development of capacitive touch sensors as the input method is rapidly progressing.

  In Non-Patent Documents 1 and 2, the detection electrode arranged on the panel is used by utilizing the fact that the voltage of the detection electrode changes due to the change in the capacitance value due to capacitive coupling when a human finger or the like approaches the detection electrode. A capacitive touch sensor that detects the presence or absence of a touch by sensing a voltage change is disclosed.

T. Nakamura, "In-cell capacitive-type touch sensor using LTPS TFT-LCD technology", Journal of the SID (Society for Information Display) 19/9, 2011, pp.639-644 S. Tomita et al. "An in-cell capacitive touch sensor integrated inan LTPS WSVGA TFT-LCD", Journal of the SID (Society for Information Display) 20/8, 2012, pp.441-449

  In the circuit configurations disclosed in Non-Patent Documents 1 and 2, in addition to the detection electrode and the amplifier that amplifies the voltage, a precharge transistor and a precharge line for precharging the detection electrode, a read transistor, and a coupling pulse Provided with a combined pulse line. On the other hand, with the miniaturization and thinning of portable information devices, there is a demand for a capacitive touch sensor with a simpler configuration.

  The present disclosure provides a simpler configuration for a capacitive touch sensor using capacitive coupling between a touch electrode and a human finger or the like.

  In one aspect of the present disclosure, in a capacitive touch sensor including a touch sensor element, the touch sensor element includes a touch electrode that forms a capacitance with a ground, and touch detection in which an input end is connected to the touch electrode. A touch detector, an amplifier having an input terminal connected to an input end of the touch detector, an output terminal connected to an output end of the touch detector, an input terminal of the amplifier, and an output An equalizing switch is provided between the input terminal and the terminal, and can be switched between electrical connection / disconnection between the input terminal and the output terminal by an on / off operation.

  According to this aspect, in the touch detector, the input / output terminal of the amplifier is short-circuited when the equalizing switch is turned on, and the voltage of the input / output terminal at this time is applied to the touch electrode. In other words, the touch electrode is precharged by the equalizing operation of the amplifier. After that, when the equalize switch is turned off, the voltage of the touch electrode is amplified by the amplifier. When the voltage of the touch electrode changes due to the approach of a person's finger or the like, the voltage change is amplified by the amplifier and touched. Obtained as detector output. That is, a circuit for precharging the touch electrode and a circuit for detecting the potential fluctuation of the electrode due to the touch can be shared. Therefore, the touch sensor element can be realized with a simple configuration.

  According to the present disclosure, a capacitive touch sensor using capacitive coupling between a detection electrode and a human finger or the like can be realized with a simpler configuration.

Configuration Example of Capacitive Touch Sensor According to First Embodiment It is a structural example of a touch detector, (a) is an example using an inverting amplifier, (b) is an example using a differential amplifier. (A) and (b) are concrete circuit structural examples of the structure of FIG. (A)-(c) is another example of composition of a touch detector Other configuration examples related to a touch detector using a differential amplifier Other configuration examples related to the touch detector (A) is a configuration example for performing an interleave operation, (b) is a timing chart of the interleave operation. (A) is a problem in touch detection with two axes, (b) is an example of touch detection with three axes. (A) and (b) are configuration examples provided with a shift register. (A) is a configuration example using a current direction detector, (b) is a configuration example of a current direction detector using a latch. (A) is the example of a structure of the current direction detector using a capacitive element, (b) is a timing chart which shows operation | movement of the example of a structure of (a). Configuration example of current direction detector using current controlled oscillator Configuration Example of Capacitive Touch Sensor According to Second Embodiment

  A first embodiment according to the present disclosure is a capacitive touch sensor including a touch sensor element. The touch sensor element includes a touch electrode that forms a capacitance between the touch sensor element and a ground. An amplifier having an input terminal connected to an input terminal of the touch detector, an output terminal connected to an output terminal of the touch detector, and an amplifier. And an equalizing switch capable of switching electrical connection / disconnection between the input terminal and the output terminal by an on / off operation.

  According to this embodiment, the touch electrode is precharged by the equalizing operation of the amplifier. For this reason, a circuit for precharging the touch electrode and a circuit for detecting the potential fluctuation of the electrode due to the touch can be shared. Therefore, a separate transistor and wiring are not necessary, and the touch sensor element can be realized with a simple configuration.

  According to a second form of the present disclosure, in the first form, the touch sensor element has an equalization operation in which a capacitance between the touch electrode and the ground is charged with a predetermined voltage, and a voltage change between the touch electrode and the ground. The touch detector turns on the equalizing switch in the equalizing operation and turns off the equalizing switch in the sensing operation.

  According to this embodiment, the equalizing operation and the sensing operation of the touch element can be executed by the on / off operation of the equalizing switch.

  A third form according to the present disclosure includes a plurality of touch sensor elements arranged so that touch electrodes formed so as to extend in the first direction are arranged in parallel in the second form, and the plurality of touch sensor elements include: When the first element group is divided into the first element group and the second element group, and the first element group is performing the equalizing operation, the second element group performs the sensing operation, and the second element group performs the equalizing operation. At this time, the first element group is controlled to perform a sensing operation.

  According to this form, it becomes possible to detect any time a touch operation is performed by the interleave operation.

  According to a fourth embodiment of the present disclosure, in the first embodiment, a plurality of touch sensor elements are provided, and a plurality of touch electrodes formed so as to extend in the first direction are arranged in parallel. A first element group composed of touch sensor elements, and a second element group composed of a plurality of touch sensor elements arranged so that touch electrodes formed to extend in a second direction different from the first direction are arranged in parallel. I have.

  According to this embodiment, it is possible to reliably detect the touch position in two directions.

  According to a fifth embodiment of the present disclosure, in the fourth embodiment, touch electrodes formed so as to extend in a third direction different from the first and second directions are arranged from a plurality of touch sensor elements arranged in parallel. The third element group is provided.

  According to this aspect, the touch position in the three directions can be reliably detected, and the ghost position detection at the time of multi-touch can be avoided.

  A sixth mode according to the present disclosure is a shift in which the output of each touch sensor element configuring the first element group is input in parallel and the output of each input touch sensor element is serially output bit by bit in the fourth mode. It has a register.

  According to this embodiment, it is possible to send the touch sensor output with a small bit width.

  According to a seventh aspect of the present disclosure, in the first aspect, the touch detector is connected to the output end of the touch detector, and the potential of the output end of the touch detector when there is no touch in the sensing operation. Is provided with an offset setting means for setting to a predetermined logic level.

  According to this aspect, it is possible to reliably detect the presence or absence of a touch from the output of the touch sensor element.

  An eighth form according to the present disclosure includes, in the first form, a reference electrode that forms a capacitance with the ground, and the touch detector is connected as an amplifier with a negative-phase input terminal connected to an input terminal of the touch detector. The differential amplifier includes a positive phase input terminal connected to the reference electrode, and the equalizing switch is provided between the negative phase input terminal and the output terminal of the differential amplifier.

  According to this embodiment, the touch detector can be configured with a differential amplifier, and the influence of fluctuations in the ground potential can be suppressed.

  According to a ninth embodiment of the present disclosure, in the eighth embodiment, the ninth embodiment further includes a shield electrode that is connected to a power source that generates a predetermined potential and electrostatically shields the reference electrode.

  According to this embodiment, since the electromagnetic wave or the like can be prevented from affecting the reference electrode, the output of the touch sensor element can be further stabilized.

  According to a tenth aspect of the present disclosure, in the first aspect, the touch sensor element includes a differential comparator in which one input is connected to the output terminal of the touch detector and a predetermined reference voltage is given to the other input. ing.

  According to this aspect, it is possible to reliably detect the presence or absence of a touch from the output of the touch sensor element.

  According to an eleventh aspect of the present disclosure, in the tenth aspect, the touch sensor element includes a plurality of differential comparators, and the plurality of differential amplifiers have different predetermined reference voltages.

  According to this embodiment, it is possible to detect a plurality of states such as no touch, touch, and touch separation from the output of the touch sensor element.

  According to a twelfth aspect of the present disclosure, in the first aspect, the touch sensor element is connected to the output end of the touch detector, and includes a current direction detector that detects the direction of the output current at the output end.

  According to this aspect, the current direction detector that detects the direction of the output current at the output end of the touch detector enables highly accurate touch detection in a shorter time.

According to a thirteenth embodiment of the present disclosure, in the twelfth embodiment, the current direction detector includes a current control oscillator that uses the output current of the touch detector as a bias current, and a counter that counts the oscillation frequency of the current control oscillator. According to this embodiment, the current direction detector can be configured digitally, and highly accurate touch recognition that eliminates the influence of background noise is possible.

  A fourteenth aspect according to the present disclosure is a capacitive touch sensor, each having a touch electrode that forms a capacitance with a ground, and a plurality of sensor in-cell portions arranged in an array, In order to send a row selection signal for controlling the on / off operation of the bus switch of each row, arranged for each column and output from the sensor in-cell portion of that column, the column bus connected via the bus switch, and arranged for each row Row selection signal lines and an equalization signal line that is arranged for each row and transmits an equalization signal for controlling the equalization operation of the sensor in-cell portion of the row. The sensor in-cell portion has an input terminal connected to the touch electrode. And an amplifier having an output terminal connected to the bus switch, and provided between the input terminal and the output terminal of the amplifier, and electrically connected / disconnected between the input terminal and the output terminal. And a equalizing switch for switching in response to the rise signal.

  According to this embodiment, the touch electrode is precharged by the equalizing operation of the amplifier. This eliminates the need for a transistor or wiring for precharging the touch electrode, and an in-cell touch sensor can be realized with a simple configuration.

(First embodiment)
FIG. 1 is a diagram illustrating a configuration example of a capacitive touch sensor according to the present embodiment. In FIG. 1, a plurality of touch sensor elements 1 each having a touch electrode 2 and a touch detector 10 are arranged on a display unit 4. The touch electrode 2 forms a capacitance with the ground 5. In the configuration of FIG. 1, the ground 5 is formed on the back surface of the display unit 4. The touch detector 10 has an input end connected to the touch electrode 2. In the configuration of FIG. 1, the touch electrode 2 and the touch detector 10 are connected via the pad 3 of the display unit 4. In addition, it is preferable to arrange | position components other than the touch electrode 2 of the touch sensor element 1 in the outer peripheral area of the screen area | region which detects a touch.

  In the configuration of FIG. 1, a plurality of touch sensor elements 1 are arranged in two element groups G1 and G2. In the element group G1, the touch electrodes 2 extend in the X-axis direction (the horizontal direction in the drawing), and the touch electrodes 2 are arranged in parallel in the Y-axis direction (the vertical direction in the drawing). In the element group G2, the touch electrodes 2 extend in the Y-axis direction, and the touch electrodes 2 are arranged in parallel in the X-axis direction. In the element group G1, the touch electrodes 2 are arranged by being blocked by an insulator so as not to contact each other. Similarly, also in the element group G2, the touch electrodes 2 are arranged by being cut off by an insulator so as not to contact each other. Further, the touch electrode 2 of the element group G1 and the touch electrode 2 of the element G2 are also blocked by an insulator so as not to contact each other.

  The touch sensor element 1 performs an equalizing operation for charging a capacitance between the touch electrode 2 and the ground 5 with a predetermined voltage, and a sensing operation for detecting whether or not the voltage between the touch electrode 2 and the ground 5 is changed. Do. In the sensing operation, when the touch electrode 2 is touched by a human finger or the like, the capacitance value changes, and the voltage between the touch electrode 2 and the ground 5 changes. By specifying the touch sensor element 1 whose voltage has changed, it is possible to detect the touched position on the display unit 4.

  The touch detector 10 includes an amplifier 11, an equalize switch SW1, a current source 13, and a switch SW2. The input terminal of the amplifier 11 is connected to the input terminal of the touch detector 10, that is, the touch electrode 2 is electrically connected. The equalize switch SW1 is provided between the input terminal and the output terminal of the amplifier 11, and the electrical connection / disconnection between the input terminal and the output terminal can be switched by the on / off operation. By turning on the equalizing switch SW1, the input and output of the amplifier 11 are short-circuited, and the equalizing operation of the touch sensor element 1 is realized. The output terminal of the amplifier 11 is connected to the output terminal of the touch detector 10, and the output of the amplifier 11 becomes the output of the touch detector 10.

  The current source 13 and the switch SW2 constitute an offset setting unit. The current source 13 is connected to the output terminal of the touch detector 10 via the switch SW2. When the switch SW2 is in the ON state, the potential at the output terminal of the touch detector 10 is maintained at a predetermined logic level (here, “L” level) when the touch electrode 1 is not touched by a person or the like.

  The operation of the capacitive touch sensor of FIG. 1 will be described.

  First, the touch detectors 10 of all or some of the touch sensor elements 1 perform an equalizing operation. That is, the equalize switch SW1 is set to an on state, and the input / output of the amplifier 11 is short-circuited. Then, a predetermined voltage is charged between the touch electrode 2 connected to the touch detector 10 and the ground 5. Next, the equalizing switch SW1 is released and set to an off state, and a sensing operation is performed. At this time, the switch SW2 is turned on. In this state, if there is an object contact with the touch electrode 2, the capacitance between the touch electrode 2 and the ground 5 increases, and the voltage between the touch electrode 2 and the ground 5 decreases. This voltage drop is inverted and amplified by the amplifier 11 to the logic output level.

  In the configuration of FIG. 1, when the touch sensor element 1 in which the voltage drop is detected is specified in the element group G1 and the element group G2, the arrangement position of the touch electrode 2 of the specified touch sensor element 1 is specified. It can be determined that there is contact at the intersection of That is, in the configuration of FIG. 1, the touch sensor element 1 is arranged separately in the X-axis direction and the Y-axis direction, so that the X of the place where contact has occurred on the display unit 4 by the output of each touch sensor element 1. A position in the axial direction and a position in the Y-axis direction can each be specified.

  FIG. 2 is a diagram illustrating a configuration example of the touch detector 10. FIG. 2A shows a configuration using a single-input inverting amplifier, which is the same as the configuration shown in FIG. FIG. 2B shows a configuration using a differential amplifier. The differential amplifier 15 has a negative-phase input terminal connected to the touch electrode 2 and a positive-phase input terminal connected to the reference electrode 6 that forms a capacitance with the ground. The equalize switch SW1 is provided between the negative phase input terminal and the output terminal of the differential amplifier 15. That is, the equalizing operation is realized by turning on the equalizing switch SW1 and short-circuiting the reverse phase input and the output of the differential amplifier 15.

  2A and 2B, by connecting the current source 13 to the output of the inverting amplifier 11 or the differential amplifier 15, the output is made constant even when there is no touch operation. It is possible. The current source 13 needs to be controlled to operate after the equalizing operation is completed. Therefore, the current source 13 is connected to the output of the inverting amplifier 11 or the differential amplifier 15 by turning on the switch SW2 after completion of the equalizing operation.

  FIG. 3 is a diagram showing a specific circuit configuration example of the configuration example of FIG. 2, and FIGS. 3A and 3B correspond to the configuration examples of FIGS. 2A and 2B, respectively. In FIG. 3A, PMOS1 and NMOS1 form an inverting amplifier 11, and NMOS2 forms an equalize switch SW1. The NMOS 3 forms the switch SW2, and the NMOS 4 forms the current source 13. In FIG. 3B, PMOS1, PMOS2, NMOS1, NMOS2 and NMOS3 form a differential amplifier 15, and NMOS4 forms an equalize switch SW1. The NMOS 5 forms the switch SW2, and the NMOS 6 forms the current source 13.

  Further, the touch detector 10 may be configured not to use the current source 13. FIG. 4 is a diagram illustrating another configuration example of the touch detector 10. In the configuration of FIG. 4A, a differential comparator 7 that compares the output of the detection unit 10a in the touch detector 10 with a reference voltage is provided. Here, the detection unit 10a has a configuration in which the current source 13 and the switch SW2 are omitted in FIGS. 2 (a) and 2 (b). By appropriately setting the reference voltage of the differential comparator 7, the output of the touch detector 10 when there is no touch operation can be made constant.

  In the configuration of FIG. 4B, a plurality of differential comparators 8a and 8b for comparing the output of the detection unit 10a in the touch detector 10 with different reference voltages are provided. In this configuration, it is possible to detect that the output of the detection unit 10a is in an intermediate state. In addition, it can be determined whether it is at the upper logical level or the lower logical level. If it is in an intermediate state, it is determined that there is no touch. In addition, since the output logic level of the touch detector 10 is reversed when there is a touch and when the touched object is separated, the presence of touch and the presence of touch separation are detected by determining the logic level. be able to. Therefore, it is possible to detect three states: no touch, touch, and touch separation.

  Further, as shown in FIG. 4C, an A / D converter 9 for A / D converting and outputting the output of the detection unit 10a in the touch detector 10 may be provided.

  FIG. 5 shows another configuration example of a touch detector using a differential amplifier. In the configuration of FIG. 5, the reference signal detection unit 20 including the reference electrode 6 is connected to the positive phase input terminal of the differential amplifier 15. In addition to the reference electrode 6 connected to the positive phase input terminal of the differential amplifier 15, the reference signal detection unit 20 includes a shield electrode 21 connected to a power supply 22 that generates a predetermined potential. The shield electrode 21 electrostatically shields the reference electrode 6 so as not to be affected by the lines of electric force from the external contact body. The reference electrode 6 is configured to form a capacitance with the ground electrode 23 that monitors the potential of the ground. Thereby, the reference signal detection unit 20 can detect the ground potential fluctuation of the entire touch sensor system. Accordingly, the influence of background noise can be eliminated from the potential of the touch electrode 2, and more accurate touch detection can be performed.

  FIG. 6 shows another configuration example of the touch detector using the inverting amplifier. In the configuration of FIG. 6, a reference bias generation unit 25 including a reference electrode 26 is provided, and an output voltage of the reference bias generation unit 25 is applied as a bias voltage of a current source of the inverting amplifier 11 of each touch detector 10. ing. The reference bias generator 25 detects the potential fluctuation of the reference electrode 26 caused by the fluctuation of the ground potential, and transmits the current fluctuation corresponding to the potential fluctuation to the inverting amplifier 11 of each touch detector 10. The potential fluctuation of the touch electrode 2 due to the fluctuation of the ground potential is almost equal to the potential fluctuation of the reference electrode 26. For this reason, the current fluctuation of the inverting amplifier 11 due to the potential fluctuation of the touch electrode 2 is canceled by the current fluctuation transmitted from the reference bias generation unit 25. Therefore, the reference bias generator 25 can suppress the influence of ground potential fluctuations in the plurality of touch detectors 10.

(Other configuration example 1)
Since the touch sensor element described above needs to perform an equalizing operation, the sensing operation cannot be performed during the period in which the equalizing operation is being performed. In order to avoid this problem, for example, the touch sensor element may be interleaved.

  FIG. 7A shows a configuration example in which an interleave operation is performed. Touch sensor elements in which touch electrodes 2 are arranged in the same direction are divided into an element group 1 and an element group 2. As shown in the operation timing chart of FIG. 7B, when the element group 1 is performing the equalizing operation, the element group 2 is performing the sensing operation, and when the element group 2 is performing the equalizing operation, the element group 1 is controlled to perform a sensing operation. By performing the interleaving operation in this way, at least one of the element groups 1 and 2 always performs the sensing operation. Therefore, it is possible to detect a touch operation whenever it is performed.

(Other configuration example 2)
In the configuration of the touch sensor in FIG. 1, the touch position is determined in the two-axis directions of the X axis and the Y axis. For this reason, when there is a contact at a plurality of positions, a touch position different from the true touch position may appear as a ghost.

  For example, as shown in FIG. 8A, it is assumed that there are touches at two touch positions (X1, Y1) and (X2, Y2). In this case, there is a possibility that it is detected that there is a touch at the ghost positions (X2, Y1) and (X1, Y2) different from the true touch position. In order to avoid this problem, for example, as shown in FIG. 8B, the Z axis may be further added to the touch detection axis, and the touch position may be detected by three axes. In FIG. 8B, the Z-axis is set in an oblique direction that lowers to the right. In such a Z-axis, if a touch is detected only at the coordinate Z1, the ghost positions (X2, Y1) and (X1, Y2) can be excluded because the Z-axis coordinate is not Z1. Therefore, it is possible to avoid detecting the ghost position even in the case of multi-touch.

  In the example of FIG. 8B, the Z-axis is set in a diagonal direction that lowers to the right. However, the present invention is not limited to this. For example, the Z-axis may be set in a diagonal direction that increases to the right. Further, the touch electrodes may be arranged in the axial direction with more than three axes.

(Other configuration example 3)
FIGS. 9A and 9B are configuration examples of a capacitive touch sensor provided with a shift register. FIG. 9A shows a two-axis configuration of XY axes, and FIG. 9B shows a three-axis configuration of XYZ axes. That is, 1-bit information output from sensor elements arranged in the same axis direction is input in parallel to the shift register. Then, it is serially output bit by bit from the shift register. In the configuration of FIG. 8A, a shift register SH1 is provided for the X-axis sensor element, and a shift register SH2 is provided for the Y-axis sensor element. In the configuration of FIG. 8B, two shift registers SH3 and SH4 are provided for the Z-axis sensor element. With such a configuration, the touch sensor output can be transferred with a small bit width using the shift register.

  Further, the shift register and the touch detector may be integrated together with a driver unit of a display display on which the touch sensor is mounted. Thereby, the mounting area can be further reduced.

(Other configuration example 4)
In the touch detector configured as described above, it cannot be determined whether or not there is a touch unless the output of the touch detector reaches a predetermined logic level. For this reason, it takes a certain amount of time to detect the touch position, which may cause a problem in the operation of the touch system.

  Therefore, in this configuration example, as shown in FIG. 10A, a current direction detector 30 connected to the output end of the touch detector 10 and detecting the direction of the output current at the output end is provided. Then, the inclination of the output of the touch detector 10 is detected by the current direction detector 30, thereby determining the touch operation. Thereby, highly accurate touch detection can be performed in a shorter time.

  FIG. 10B is an example of a circuit configuration of the current direction detector 30. In FIG. 10B, two inverting amplifiers 31 and 32 are latch-coupled to form a current detection type latch. Further, a switch SW3 for equalization and a switch SW4 for switching connection with the output terminal of the touch detector 10 are provided. First, in a state where the switch SW4 is turned off and disconnected from the input, the switch SW3 is turned on, and the current detection type latch composed of the inverting amplifiers 31 and 32 is equalized. Next, the switch SW3 is turned off and the switch SW4 is turned on, and the output current of the touch detector 10 is input. The current detection type latch composed of the inverting amplifiers 31 and 32 performs a latch operation and outputs a signal corresponding to the direction of the input current.

  FIG. 11A shows another example of the circuit configuration of the current direction detector 30. In FIG. 11A, capacitive elements C1 and C2 are connected to the positive phase input terminal and the inverting input terminal of the differential amplifier 34, respectively. Further, switches SW5 and SW6 for switching the connection with the output terminal of the touch detector 10 are provided on the input lines of the positive phase input terminal and the inverting input terminal of the differential amplifier 34, respectively.

  As shown in FIG. 11B, first, in a period in which the touch sensor element performs an equalizing operation, the switches SW5 and SW6 are both on, and the capacitive elements C1 and C2 are charged to a constant voltage. Next, in a period in which the touch sensor element performs a sensing operation, both the switches SW5 and SW6 are turned on for a while, and then only SW5 is turned off. Thereby, after the output current of the touch detector 10 is charged to both the capacitive elements C1 and C2 for a while, only the capacitive element C2 is continuously charged. As a result, the direction of the output current of the touch detector 10 can be detected from the magnitude relationship between the potentials of the capacitive elements C1 and C2. Therefore, when the differential amplifier 34 detects the potential difference between the capacitive elements C1 and C2, the direction of the output current of the touch detector 10 can be detected, thereby enabling touch detection.

  FIG. 12 shows another example of the circuit configuration of the current direction detector 30. In the configuration of FIG. 12, the output of the touch detector 10 is used as the bias current of the current control oscillator 35. Thereby, a change in the output current of the touch detector 10 appears as a change in the oscillation frequency of the current control oscillator 35. The counter 36 measures the oscillation frequency of the current control oscillator 35. Since the temporal change of the oscillation frequency corresponds to the slope of the output of the touch detector 10, the output of the counter 36 measured at different times is stored in the registers 37 and 38, respectively, and the touch determination logic circuit 39 determines the difference from the difference. Perform touch determination.

  Further, in the configuration of FIG. 12, the overall frequency change of the current control oscillator 35 connected to each touch sensor element is considered to represent background noise applied to the entire touch sensor. For this reason, the average frequency change of each current control oscillator 35 may be subtracted from the frequency change of each current control oscillator 35 as a frequency change due to noise. Thereby, for example, even if the configuration using the reference electrode as shown in FIG. 5 or FIG. 6 is not adopted, highly accurate touch recognition that eliminates the influence of background noise is possible.

  The circuit configuration shown in this configuration example is merely an example of the circuit configuration of the current direction detector, and the same effect can be obtained by using other circuit configurations that can detect the current direction.

(Second Embodiment)
In the capacitive touch sensor according to the first embodiment, touch electrodes extending in one direction are arranged in parallel. However, the configuration of the touch sensor element shown in the first embodiment can also be applied to an in-cell type touch sensor.

  FIG. 13 shows a configuration example of the capacitive touch sensor according to the present embodiment, which realizes an in-cell touch sensor. In the configuration of FIG. 13, the sensor in-cell unit 40 including the touch electrode 41 is arranged in an array on the display unit 50. The touch electrode 41 forms a capacitance with the ground. In addition to the touch electrode 41, the sensor in-cell unit 40 includes a transistor 42 as an amplifier for detecting a potential change of the touch electrode 41, and a transistor 43 as an equalizing switch for equalizing operation. The touch electrode 41 is connected to the gate of the transistor 42, and the transistor 43 is provided between the gate and drain of the transistor 42. That is, the gate and drain of the transistor 42 correspond to the input terminal and output terminal of the amplifier.

  A column bus 44 is arranged for each column of the sensor in-cell portions 40 arranged in an array. The column bus 44 is connected to the output of the sensor in-cell unit 40 in the column via a bus switch 47. Further, a row selection signal line 45 and an equalize signal line 46 are provided for each row of the sensor in-cell portions 40 arranged in an array. The row selection signal line 45 is for sending a row selection signal for controlling the on / off operation of the bus switch 47 of the row. The equalize signal line 46 is used to send an equalize signal for controlling the equalization operation of the sensor in-cell unit 40 in the row. The sensor driver 48 sends a row selection signal via the row selection signal line 45 and sends an equalization signal via the equalization signal line 46.

  The operation of the capacitive touch sensor of FIG. 13 will be described. In the configuration of FIG. 13, the touch detection of the entire display unit 50 is realized by scanning for each row.

  That is, the sensor driver 48 outputs a row selection signal for a certain row, and connects the sensor in-cell unit 40 of that row to the column bus of each column via the bus switch 47. Further, an equalize signal is output for the row, the transistor 43 is turned on in the sensor-in-cell portion 40 of the row, and the input / output of the detection transistor 42 is short-circuited. Thereby, an equalizing operation is performed. Thereafter, the transistor 43 is turned off, and a sensing operation for touch detection is performed. When the potential change of the touch electrode 41 occurs, the output current of the sensor in-cell unit 40 changes. Therefore, this current change is sent to the comparator 49 provided outside the display unit 50, converted into a logic level and output. The

  The above operation is performed for each row. Thereby, touch detection is realized over the entire display unit 50. In the description here, the sensor in-cell unit 40 includes the transistor 42 as an amplifier and the transistor 43 as an equalizing switch. However, the present invention is not limited to this.

  According to the present disclosure, a capacitive touch sensor using capacitive coupling between a touch electrode and a human finger or the like can be realized with a simpler configuration. For example, a portable information device equipped with a touch panel This is useful for downsizing and cost reduction.

DESCRIPTION OF SYMBOLS 1 Touch sensor element 2 Touch electrode 6 Reference electrode 7 Differential comparator 8a, 8b Differential comparator 10 Touch detector 11 Amplifier 13 Current source 15 Differential amplifier 20 Reference signal detection part 21 Shield electrode 22 Power supply 30 Current direction detector 35 Current Control Oscillator 36 Counter 40 Sensor In-Cell Unit 41 Touch Electrode 42 Transistor (Amplifier)
43 Transistor (equalize switch)
44 column bus 45 row selection signal line 46 equalize signal line 47 bus switch SW1 equalize switch SW2 switch G1 first element group G2 second element group SH1 to 4 shift register

Claims (14)

A capacitive touch sensor having a touch sensor element,
The touch sensor element is
A touch electrode that forms a capacitance with the ground;
A touch detector having an input end connected to the touch electrode;
The touch detector is
An amplifier having an input terminal connected to the input end of the touch detector and an output terminal connected to the output end of the touch detector;
An equalizer switch provided between the input terminal and the output terminal of the amplifier and capable of switching electrical connection / disconnection between the input terminal and the output terminal by an on / off operation; A capacitive touch sensor characterized by comprising: The capacitive touch sensor according to claim 1,
The touch sensor element performs an equalizing operation for charging a predetermined voltage to a capacitance between the touch electrode and the ground, and a sensing operation for detecting whether or not a voltage changes between the touch electrode and the ground. And
The touch detector is
In the equalizing operation, the equalizing switch is turned on, and in the sensing operation, the equalizing switch is turned off. The capacitive touch sensor according to claim 2,
A plurality of touch sensor elements arranged such that the touch electrodes formed to extend in the first direction are arranged in parallel;
The plurality of touch sensor elements are divided into a first element group and a second element group, and
When the first element group is performing the equalizing operation, the second element group is performing the sensing operation, and when the second element group is performing the equalizing operation, the first element group is performing the sensing operation. A capacitive touch sensor that is controlled to perform. The capacitive touch sensor according to claim 1,
A plurality of the touch sensor elements are provided,
A first element group consisting of a plurality of touch sensor elements arranged so that the touch electrodes formed to extend in the first direction are arranged in parallel;
The touch electrode formed so as to extend in a second direction different from the first direction includes a second element group including a plurality of the touch sensor elements arranged in parallel. Capacitive touch sensor. The capacitive touch sensor according to claim 4,
The touch electrode formed to extend in a third direction different from the first and second directions includes a third element group including a plurality of the touch sensor elements arranged in parallel. Capacitance type touch sensor. The capacitive touch sensor according to claim 4,
An electrostatic capacity comprising: a shift register that inputs the outputs of the touch sensor elements constituting the first element group in parallel and serially outputs the input outputs of the touch sensor elements bit by bit. Type touch sensor. The capacitive touch sensor according to claim 1,
The touch detector is
Connected to the output terminal of the touch detector, and provided with an offset setting means for setting the potential at the output terminal of the touch detector when there is no touch in the sensing operation to a predetermined logic level. Capacitive touch sensor characterized by The capacitive touch sensor according to claim 1,
It has a reference electrode that forms a capacitance with the ground,
The touch detector includes, as the amplifier, a differential amplifier in which a negative phase input terminal is connected to the input terminal of the touch detector and a positive phase input terminal is connected to the reference electrode.
The capacitive touch sensor, wherein the equalizing switch is provided between the negative-phase input terminal and the output terminal of the differential amplifier. The capacitive touch sensor according to claim 8,
A capacitive touch sensor, further comprising a shield electrode connected to a power source that generates a predetermined potential and electrostatically shields the reference electrode. The capacitive touch sensor according to claim 1,
The touch sensor element is
A capacitive touch sensor comprising a differential comparator in which one input is connected to the output terminal of the touch detector and a predetermined reference voltage is applied to the other input. The capacitive touch sensor according to claim 10,
The touch sensor element includes a plurality of the differential comparators,
The capacitive touch sensor, wherein the plurality of differential amplifiers have different predetermined reference voltages. The capacitive touch sensor according to claim 1,
The touch sensor element is
An electrostatic capacity type touch sensor comprising a current direction detector connected to the output end of the touch detector and detecting a direction of an output current at the output end. The capacitive touch sensor according to claim 12,
The current direction detector is
A current-controlled oscillator that uses the output current of the touch detector as a bias current;
A capacitance type touch sensor comprising: a counter that counts an oscillation frequency of the current control oscillator. Each having a touch electrode that forms a capacitance with the ground, and a plurality of sensor in-cell portions arranged in an array; and
Arranged for each column, the output of the sensor in-cell portion of the column, and a column bus connected via a bus switch;
A row selection signal line for sending a row selection signal arranged for each row and controlling the on / off operation of the bus switch of the row;
An equalize signal line for sending an equalize signal that is arranged for each row and controls an equalize operation of the sensor in-cell portion of the row;
The sensor in-cell part is
An amplifier having an input terminal connected to the touch electrode and an output terminal connected to the bus switch;
An equalizer switch provided between the input terminal and the output terminal of the amplifier, and configured to switch electrical connection / disconnection between the input terminal and the output terminal according to the equalize signal; A capacitive touch sensor characterized by having