JP2013183435A - Control circuit and offset adjustment circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control circuit that correctly controls an offset included in an output of a touch sensor.SOLUTION: The control circuit for controlling an adjustment circuit on the basis of an output voltage from a voltage output circuit having a CV conversion circuit for outputting the output voltage, which depends on a capacitance value of a capacitor with a variable capacitance value and of a touch sensor, and the adjustment circuit, which adjusts the capacitance value of the capacitor includes: a first acquisition circuit for acquiring the output voltage as a first output voltage when the CV conversion circuit is activated; a second acquisition section for acquiring the output voltage as a second output voltage every time an instruction to acquire the output voltage is input; a first determination section for determining whether or not a difference of the second output voltage from a reference value depending on the first output voltage is larger than a predetermined value; and an adjustment section for instructing the adjustment circuit to adjust the capacitance value of the capacitor so as to remove an offset in the output voltage if the difference is smaller than the predetermined value.

Description

  The present invention relates to a control circuit and an offset adjustment circuit.

  Some interface devices such as a touch pad and a touch switch are provided with a capacitive touch sensor. In such a device, touch detection is performed based on a change in the capacitance value of the touch sensor (see, for example, Patent Document 1).

JP 2005-190950 A

  The output of the touch sensor varies depending on the use environment such as a touch switch (for example, temperature and humidity). Therefore, generally, a calibration process (hereinafter referred to as calibration) for removing an offset included in the output of the touch sensor is performed. By the way, if the touch switch is touched during calibration, the offset of the touch sensor output is not correctly reflected.

  The present invention has been made in view of the above problems, and an object thereof is to provide a control circuit capable of correctly controlling an offset included in the output of a touch sensor.

  To achieve the above object, according to one aspect of the present invention, a capacitor capable of changing a capacitance value, a CV conversion circuit that outputs an output voltage corresponding to the capacitance value of the touch sensor, and a capacitance value of the capacitor are adjusted. A control circuit for controlling the adjustment circuit based on the output voltage from the voltage output circuit comprising the adjustment circuit, and obtaining the output voltage when the CV conversion circuit is activated as the first output voltage A first acquisition unit, a second acquisition unit that acquires the output voltage as the second output voltage each time an instruction to acquire the output voltage is input, and a reference value corresponding to the first output voltage; A first determination unit that determines whether or not a difference from the second output voltage is greater than a predetermined value; and if the difference is smaller than the predetermined value, the adjustment circuit is configured to remove an offset of the output voltage. The computer Comprising an adjustment unit for adjusting the capacitance value of the capacitors, the.

  A control circuit that can correctly control the offset included in the output of the touch sensor can be provided.

It is a figure which shows the outline | summary of the touch switch apparatus 10 to which this invention is applied. 2 is a diagram illustrating an example of a signal processing circuit 21. FIG. It is a figure for demonstrating the state in which sense line XL0 is selected. 3 is a diagram illustrating an example of a variable capacitor 31. FIG. It is a figure which shows an example of the structure of the microcomputer 23, and a functional block implement | achieved by CPU61a. 6 is a diagram illustrating an example of functional blocks implemented in a calibration processing unit 73. FIG. It is a flowchart which shows an example of the process which CPU61a performs. It is a flowchart which shows an example of an offset adjustment process. 4 is a diagram for explaining a state in which a finger approaches the surface of the touch switch 20. FIG. It is a figure for demonstrating an example of the correction process of the data Dp. It is a figure which shows the relationship between normal measurement in case the number of channels at the time of acquiring data AD0-AD2 is 12, and calibration. It is a figure which shows the relationship between normal measurement and calibration in case the number of channels at the time of acquiring data AD0-AD2 is two. 2 is a diagram illustrating an example of a signal processing circuit 200. FIG. 4 is a diagram for explaining a signal output from a signal generation circuit 210. FIG. 2 is a diagram illustrating an example of a signal generation circuit 210. FIG. The figure which shows an example of the offset adjustment process by the signal processing circuit. It is a figure which shows an example of the structure of the microcomputer 23, and a functional block implement | achieved by CPU61b. It is a flowchart which shows an example of the process which CPU61b performs.

At least the following matters will become apparent from the description of this specification and the accompanying drawings.
FIG. 1 is a diagram showing an outline of a touch switch device 10 to which the present invention is applied. The touch switch device 10 includes a touch switch 20, signal processing circuits 21 and 22, and a microcomputer 23.

  The touch switch 20 is provided on a glass substrate (not shown). Further, between the touch switch 20 and the glass substrate, a voltage is applied to the sense lines XL0 to XL11 and YL0 to YL11 for detecting the touch position and a capacitance (touch sensor) formed on each sense line. Drive lines XDR and YDR are provided.

  The signal processing circuit 21 detects a change in the capacitance value formed in each of the 12 sense lines XL0 to XL11 in the X-axis direction by applying a predetermined voltage to the drive line XDR.

  The signal processing circuit 22 detects a change in capacitance value formed in each of the 12 sense lines YL0 to YL11 in the Y-axis direction by applying a predetermined voltage to the drive line YDR.

  The microcomputer 23 comprehensively controls the touch switch 20 and the signal processing circuits 21 and 22 included in the touch switch 20. For example, the microcomputer 23 performs determination of the touch position, processing according to the operation of the touch switch 20, and the like based on the outputs of the signal processing circuits 21 and 22.

== An example of the signal processing circuit 21 ==
FIG. 2 is a diagram illustrating an example of the signal processing circuit 21 (voltage output circuit). The signal processing circuit 21 includes a multiplexer (MUX) 30, a variable capacitor 31, a register 32, a drive circuit 33, a CV conversion circuit 34, an AD converter (ADC) 35, an interface (IF) circuit 36, and a control circuit 37. Is done. Note that the register 32 and the control circuit 37 correspond to an adjustment circuit.

  The multiplexer 30 is a selection circuit of 12 channels (Ch0 to Ch11), and selects one of the sense lines XL0 to XL11 and connects to the node N based on the control of the control circuit 37. For example, when the channel Ch0, that is, the sense line XL0 is selected, the capacitor 40 formed between the sense line XL0 and the drive line XDR is connected to the node N as shown in FIG. Also, when any of the sense lines XL1 to XL11 is selected, a capacitor (not shown) formed between each of the sense lines XL1 to XL11 and the drive line XDR is connected to the node N as in FIG. Connected. The node N is a node to which the output of the multiplexer 30, one end of the variable capacitor 31, and the input of the CV conversion circuit 34 are connected.

  The variable capacitor 31 is a capacitor whose capacitance value changes according to the data stored in the register 32, and has one end connected to the node N and the other end connected to the drive circuit 33. As illustrated in FIG. 4, the variable capacitor 31 includes capacitors 41 to 44 and switches SW1 to SW4. The switches SW1 to SW4 are turned on or off depending on the data stored in the register 32. As a result, the combined capacitance of the capacitors 41 to 44, that is, the capacitance value Ca of the variable capacitor 31 changes. The data stored in the register 32 is updated by the control circuit 37.

  The drive circuit 33 outputs a predetermined drive signal to the drive line XDR and the other end of the variable capacitor 31 based on the control of the control circuit 37. Therefore, for example, when the sense line XL0 is selected as shown in FIG. 3, the capacitor 40 and the variable capacitor 31 formed between the sense line XL0 and the drive line XDR are driven by the drive circuit 33.

  The CV conversion circuit 34 outputs an output voltage Vout corresponding to the capacitance value of the capacitor connected to the node N when the drive circuit 33 outputs a drive signal to the variable capacitor 31 and the like. For example, in the case of FIG. 3 in which the channel Ch0 is selected, the value of the output voltage Vout is a value corresponding to the capacitance values of the variable capacitor 31 and the capacitor 40. The CV conversion circuit 34 outputs the output voltage Vout corresponding to the capacitance formed on each of the sense lines XL0 to XL11 by switching the channels Ch0 to Ch11. In the present embodiment, when the touch switch 20 is not touched and the offset is canceled, the output voltage Vout of “0 V (zero volt)” is output.

  The AD converter 35 digitizes the output voltage Vout and outputs it to the interface circuit 36.

  The interface circuit 36 exchanges data with the microcomputer 23 based on an instruction from the microcomputer 23. For example, the interface circuit 36 transmits the digitized output voltage Vout to the microcomputer 23 based on an instruction to acquire the output voltage Vout from the microcomputer 23. Further, the interface circuit 36 transmits various instructions from the microcomputer 23 to the control circuit 37.

  The control circuit 37 controls each block of the signal processing circuit 21 based on an instruction from the microcomputer 23.

  Although the signal processing circuit 21 has been described here, the signal processing circuit 22 is the same as the signal processing circuit 21, and thus detailed description thereof is omitted.

== Details of the microcomputer 23 ==
As shown in FIG. 5, the microcomputer 23 (control circuit) includes a memory 60 and a CPU (Central Processing Unit) 61a.

  The memory 60 stores, for example, program data to be executed by the CPU 61a and various data.

  The CPU 61a realizes various functions by executing the program data stored in the memory 60. Specifically, the CPU 61 a realizes the functions of the acquisition unit 70, the measurement unit 71, the touchdown processing unit 72, the calibration processing unit 73, and the correction unit 74.

  The acquisition unit 70 (first to fourth acquisition units) acquires the output voltage Vout and stores it in the memory 60 when the touch switch device 10 is activated or based on a predetermined instruction. The acquisition unit 70 stores the value of the output voltage Vout acquired at the time of startup in the memory 60 as data Dp (reference value).

  The measurement unit 71 (third determination unit) measures the output voltage Vout when the channels Ch0 to Ch11 are sequentially switched, and determines whether or not the touch switch 20 is touched. Note that the measurement unit 71 appropriately transmits an instruction for sequentially switching the channels Ch0 to Ch11, an instruction for acquiring the output voltage Vout, and the like to the signal processing circuits 21 and 22. Here, the measurement of the output voltage Vout by sequentially switching the channels Ch0 to Ch11 is referred to as normal measurement.

  When it is determined that the touch switch 20 is being touched, the touch-down processing unit 73 performs processing according to the operation result of the touch switch 20.

  The calibration processing unit 73 performs calibration, that is, offset adjustment processing of the output voltage Vout based on an instruction to start calibration. Although details will be described later, the calibration processing unit 73 first causes the acquisition unit 70 to acquire the output voltage Vout when an instruction to start calibration is input. When the difference between the acquired value of the output voltage Vout and the value of the data Dp is smaller than the predetermined value B1 (for example, when the output voltage Vout at the time of acquisition is substantially equal to the output voltage Vout) ) Executes the offset adjustment process.

  When the difference between the acquired value of the output voltage Vout and the value of the data Dp is larger than the predetermined value B1 (for example, when the output voltage Vout at the time of acquisition and the output voltage Vout greatly deviate). Then, the value of the data Dp is corrected.

<< Details of Calibration Processing Unit 73 >>
FIG. 6 is a diagram illustrating an example of functional blocks included in the calibration processing unit 73. The calibration processing unit 73 includes a touch determination unit 80, a tapping determination unit 81, and an adjustment unit 82.

  The touch determination unit 80 determines whether or not the touch switch 20 is touched after the calibration is started.

  The tapping determination unit 81 (first determination unit) determines whether an operation such as tapping (double touch) that cannot be detected by the touch determination unit 80 is performed after the calibration is started.

  The adjustment unit 82 performs offset adjustment of the output voltage Vout when touch, double touch, or the like is not performed. Note that the control unit 90 (first to third control units) included in the adjustment unit 82 outputs an instruction or the like for changing the capacitance value Ca of the variable capacitor 31. Then, the determination unit 91 (second determination unit) determines whether or not there is an influence of a finger or the like (for example, an influence when the touch switch 20 is operated very slowly) during the calibration.

== Example of processing executed by CPU 61a ==
FIG. 7 is a flowchart illustrating an example of processing executed by the CPU 61a. First, when the touch switch device 10 (each block included in the touch switch device 10) is activated, the acquisition unit 70 acquires the output voltage Vout and stores it in the memory 60 as data Dp (S100). Here, the acquisition unit 70 will be described as acquiring the output voltage Vout corresponding to each of the channels Ch0 to Ch11, for example.

  And the measurement part 71 determines whether the touch switch 20 is touched based on the acquired output voltage Vout (S101). When the touch switch 20 is touched (S101: with touch), the touchdown processing unit 73 executes a process according to the operation result of the touch switch 20 (S102). On the other hand, when the touch switch 20 is not touched (S101: no touch), calibration is started.

  When calibration is started, the acquiring unit 70 first acquires the output voltage Vout and stores it in the memory 60 as data AD0 (S103). Then, the touch determination unit 80 determines whether or not the touch switch 20 has been touched after the calibration is started (S104). Specifically, the touch determination unit 80 compares the data AD0 with a threshold value Vth for determining whether or not the touch switch 20 has been touched. When the value of the data AD0 is greater than the threshold value Vth, the touch determination unit 80 determines that there is a touch (S104: YES). As a result, the calibration is stopped and the touchdown process (S102) is executed. On the other hand, when the value of the data AD0 is smaller than the threshold value Vth, the touch determination unit 80 determines that it is not touched (S104: NO). Therefore, in this case, calibration is continued.

  Incidentally, even when the value of the data AD0 is smaller than the threshold value Vth, an operation such as tapping may be performed. Therefore, the tapping determination unit 81 determines whether or not an operation such as tapping is performed (S105). Specifically, the tapping determination unit 81 determines whether or not the difference Diff between the size (absolute value) of the data Dp and the size of the data AD0 is greater than a predetermined value B1. When the difference Diff is greater than the predetermined value B1 (S105: YES), that is, when it is determined that there is tapping during calibration, the tapping determination unit 81 sets the tapping flag stored in the memory 60 to a low level ( The level is changed from “L” level to high level (“H” level) (S106). Then, the correction unit 74 executes correction of the data Dp (S107). The correction process executed by the correction unit 74 will be described later.

  On the other hand, if the difference Diff is smaller than the predetermined value B1 (S105: NO), that is, if it is determined that there is no tapping, an offset adjustment process is executed (S108).

<< About offset adjustment processing >>
Here, an example of the offset adjustment process (S108) will be described with reference to the flowchart shown in FIG.

  First, the control unit 90 outputs a change instruction for changing the capacitance value Ca of the variable capacitor 31 from the current capacitance value C1 to the capacitance value C2 so that the offset of the output voltage Vout is canceled (S200). . The capacitance value C2 is a capacitance value that decreases the offset if the current offset is “positive”. On the other hand, when the current offset is “negative”, the capacitance value increases the offset. In addition, the change instruction output from the control unit 90 is transmitted to the control circuit 37 via the interface circuit 36. Since the control circuit 37 updates the data in the register 32 based on the change instruction, the capacitance value Ca of the variable capacitor 31 is changed to the capacitance value C2. Hereinafter, when the capacitance value Ca is changed, the same processing is executed, but is omitted as appropriate.

  When the capacitance value Ca becomes the capacitance value C2, the acquisition unit 70 acquires the output voltage Vout and stores it as data AD1 in the memory 60 (S201). The controller 90 outputs a change instruction for changing the capacitance value Ca from the capacitance value C2 to the capacitance value C1 (S202). Then, when the capacitance value Ca becomes the capacitance value C1 and the predetermined time TA has elapsed since the data AD0 was acquired in step S103, the acquisition unit 70 acquires the output voltage Vout and stores it in the memory 60 as the data AD2 (S203). ).

  Further, the determination unit 91 determines whether or not the difference between the size of the data AD0 and the size of the data AD2 is smaller than a predetermined threshold B2 (S204). Here, the predetermined threshold value B2 is a value for determining whether a finger or the like has approached the surface of the touch switch 20 slowly, for example, during calibration. Specifically, as shown in FIG. 9, a predetermined time is determined based on the difference (AD2−AD0) from the data AD2 and AD0 when the finger approaches the surface of the touch switch 20 in a predetermined time TA (for example, 100 ms). The threshold value B2 is small. Therefore, when the difference between the data AD0 and AD2 is larger than the predetermined threshold B2 (S204: NO), that is, when the finger is approaching the surface of the touch switch 20 during the calibration, the offset adjustment process is completed. Then, the process S101 of FIG. 7 is executed again.

  On the other hand, if the difference between the data AD0 and AD2 is smaller than the predetermined threshold B2 (S204: YES), that is, if the finger is not approaching the surface of the touch switch 20 during calibration, the offset adjustment process is continued. The Then, the control unit 90 outputs an instruction to select a capacitance value when a smaller value of data AD0 and AD2 is acquired (S205). As a result, the offset in the output voltage Vout is reduced. And if process S205 is performed, process S101 of FIG. 7 will be performed again.

  Therefore, by executing the above-described processing, it is possible to cancel the offset while suppressing influences such as tapping and finger approach.

<< About correction processing >>
Here, details of the correction processing executed by the correction unit 74 will be described. For example, if the touch switch 20 is not touched at the time of activation, the data Dp has a value in the “not touched” state, so that the tapping determination (S105) is made with high accuracy.

  However, when the touch switch 20 is touched with a finger at the time of activation, the value of the data Dp is a very large value compared to when the touch switch 20 is not touched. When tapping determination (S105) is executed based on such data Dp, it is determined that tapping has been performed even if the value of data AD0 is a desired value. Therefore, the correction unit 74 corrects the data Dp so that the tapping determination is accurately performed even when the data Dp is data when the touch switch 20 is touched with a finger. Specifically, the correction unit 74 corrects the data Dp so that the data Dp approaches (asymptotically approaches) the value of the data AD0. At this time, the correction unit 74 corrects the data Dp so that the rate at which the data Dp approaches the value of the output voltage Vout increases as the difference Diff between the value of the data Dp and the value of the data AD0 increases.

  FIG. 10 is a diagram illustrating an example of the correction process of the data Dp. For example, when the touch switch 20 is touched with a finger at the time of activation (time t0), the value of the data Dp is a very large value. When the tapping determination is made at time t1 (S105), the difference Diff is larger than the predetermined value B1, so that the tapping flag becomes “H” level. Thereafter, for example, a value corresponding to the difference Diff is subtracted from the data Dp so that the data Dp approaches the data AD0, and the data DP is corrected. The same process is continued from time t1 to time t4 when the difference Diff is greater than the predetermined value B1. However, the correction value (change ratio) of the data Dp at times t2 and t3 is smaller than the correction value at time t1. Furthermore, the correction value of the data Dp at time t4 is smaller than the correction values at time t2 and t3. At time t5, since the difference Diff is smaller than the predetermined value B1, the tapping flag is set to the “L” level, and the above-described offset adjustment process is executed.

  Since such correction processing is executed, in this embodiment, tapping can be detected with high accuracy.

<< About the number of channels when acquiring data >>
Here, the number of channels such as data AD0 acquired when the calibration is executed will be described. Here, as shown in FIG. 11, the output voltage Vout for 12 channels (Ch0 to Ch11) is acquired at the timing of acquiring each of the data AD0 to AD2. In such a case, if the interval of the predetermined time TA is obtained from the acquisition of the data AD0 to the acquisition of the data AD2, the calibration time becomes longer. That is, since the interval between normal measurements also becomes long, the response of operation of the touch switch 20 will become slow.

  Therefore, it is preferable to acquire the output voltage Vout of each channel as shown in FIG. 12 in order to improve the response while separating the acquisition timing of the data AD0 and AD2 by a predetermined time TA.

  In FIG. 12, when “calibration A” is executed, the acquisition unit 70 acquires data AD0 and AD1 of channels Ch0 and Ch1, and acquires data AD2 of channels Ch6 and Ch7. Then, the determination unit 91 executes determination processing using the data AD0 of the channels Ch6 and Ch7 acquired previously and the data AD2 of the channels Ch6 and Ch7 acquired this time (S204).

  Accordingly, the data AD0 of the channels Ch0 and Ch1 acquired by “Calibration A” is determined when the data AD2 of the channels Ch0 and Ch1 is acquired by “Calibration D”. It is designed to be longer than the predetermined time TA from when the data AD0 of the channels Ch0 and Ch1 is acquired by “Calibration A” until the data AD2 of the channels Ch0 and Ch1 is acquired by “Calibration D”. Suppose that

  In this way, by performing the acquisition timing of the data AD0 for a certain channel (for example, the channel Ch0) and the acquisition timing of the data AD2 by different calibration processes, while suppressing the influence of the approach of the finger, etc. The response of the touch switch 20 can be improved.

<< Other Embodiments of Signal Processing Circuit >>
FIG. 13 is a diagram illustrating an example of the second embodiment of the signal processing circuit. The signal processing circuit 200 further includes a signal generation circuit 210 in addition to each block of the signal processing circuit 21. In addition, since the block with the same code | symbol in the signal processing circuits 21 and 200 is the same, detailed description is abbreviate | omitted.

  Based on the digitized output voltage Vout, the signal generation circuit 210 generates a signal for instructing calibration or initiating touchdown processing. In the signal generation circuit 210, for example, as shown in FIG. 14, the output voltage Vout is higher than a predetermined voltage V1 for determining whether or not the touch switch 20 (touch sensor formed on the sense line) is touched. In this case, an instruction signal S1 for starting the touchdown process is output. In addition, the signal generation circuit 210 enters the range from the voltage V2 (> 0) to the voltage V1 only i times continuously or becomes lower than the voltage -V2 only j times continuously. An instruction signal S2 for starting calibration is output. The voltage V2 is a predetermined voltage (for example, a value twice the noise level) higher than the positive noise level (noise floor) of the output voltage Vout, and the voltage -V2 is also lower than the negative noise level. It is a predetermined voltage.

  The control circuit 211 controls the multiplexer 30, the register 32, and the drive circuit 33 based on various instructions from the microcomputer 23 and a calibration instruction from the signal generation circuit 210.

== Details of Signal Generation Circuit 210 ==
As shown in FIG. 15, the signal generation circuit 210 includes a latch circuit 220, comparison circuits 221 to 224, 240 and 241, counters 230 and 231, an AND circuit 250, NO circuits 251 to 253, and inverters 254 and 255. Composed.

  The latch circuit 220 (acquisition unit), for example, latches (stores) the digitized output voltage Vout every time the clock signal CLK becomes “H” level.

  The comparison circuits 221 and 222 and the AND circuit 250 determine whether or not the latched output voltage Vout is within the range of the voltage V2 (first value) to the voltage V1 (second value). The AND circuit 250 outputs an “H” level signal when the output voltage Vout is within the range from the voltage V2 to the voltage V1. Note that the comparison circuits 221 and 222 and the AND circuit 250 correspond to a first determination unit.

  The counter 230 increments the count value N by “1” when the clock signal DCLK becomes “H” level while the AND circuit 250 outputs the “H” level signal. The clock signal DCLK is a signal obtained by delaying the clock signal CLK by a delay circuit (not shown).

  The comparison circuit 240 outputs an “H” level signal when the count value N reaches “i” (first number of times).

  The OR circuit 251 resets the count value N of the counter 230 (N = “0”) when the signal from the AND circuit 250 becomes “L” level or the signal from the comparison circuit 240 becomes “L” level. .

  Accordingly, a signal of “H” level is output from the comparison circuit 240 only when the output voltage Vout latched by the latch circuit 220 is continuously “i” times within the range of the voltage V2 to the voltage V1.

  The comparison circuit 223 compares the latched output voltage Vout with the voltage V1. When the output voltage Vout is higher than the voltage V1, the comparison circuit 223 outputs an “H” level signal, that is, an instruction signal S1 for starting the touch processing. Output.

  The comparison circuit 224 (second determination unit) compares the output voltage Vout with the voltage −V2 (third value), and outputs an “H” level signal when the output voltage Vout is lower than the voltage −V2. .

  The counter 231 increments the count value M by “1” when the clock signal DCLK becomes “H” level while the comparison circuit 224 outputs the “H” level signal.

  When the count value M reaches “j” (second number of times), the comparison circuit 241 outputs an “H” level signal.

  In the AND circuits 254 and 255 and the OR circuit 252, the output of the comparison circuit 224 becomes “L” level, the output of the comparison circuit 241 becomes “L” level, or the output of the AND circuit 250 becomes “H” level. When the output of the comparison circuit 223 becomes “H” level, the count value M of the counter 231 is reset (M = “0”).

  Therefore, the “H” level signal is output from the comparison circuit 241 only when the output voltage Vout latched by the latch circuit 220 becomes lower than the voltage −V2 “j” times continuously.

  The OR circuit 253 outputs an “H” level signal, that is, an instruction signal S2 for starting calibration when either of the outputs of the comparison circuit 240 or the comparison circuit 241 becomes “H” level. Note that the comparison circuits 240 and 241 and the OR circuit 253 correspond to an adjustment unit.

== Example of Operation of Signal Processing Circuit 200 ==
FIG. 16 is a diagram illustrating an example of the operation (offset adjustment process) of the signal processing circuit 200. Here, the value of “i” described above is, for example, “5”, and the value of “j” is, for example, “4”. Here, it is assumed that the clock signal CLK becomes “H” level at each timing from time t10 to time t30.

  From time t10 to t14, the output voltage Vout is in the range of V2 <Vout <V1, and therefore the calibration instruction S2 or the like is not output from the signal generation circuit 210.

  Since the output voltage Vout falls within the range of V2 <Vout <V1 between times t15 and t19, the count value N is incremented. At time t19, since the count value N becomes “5”, the calibration instruction signal S2 is output. As a result, the offset is adjusted and the output voltage Vout becomes substantially the target value (0 V).

  At time t23, since the output voltage Vout becomes higher than the voltage V1, the instruction signal S1 instructing the touchdown process is output.

  Further, since the output voltage Vout remains lower than the voltage −V2 from time t27 to time t30, the count value M is incremented. At time t30, since the count value M is “4”, the calibration instruction signal S2 is output. As a result, the offset is adjusted, and the output voltage Vout becomes substantially the target value (0 V).

  Thus, since the signal processing circuit 200 can reduce the offset of the output voltage Vout, the output voltage Vout with high accuracy is output.

<< Other Embodiments of Functional Block of CPU 61 >>
FIG. 17 is a diagram illustrating an example of functional blocks of the CPU 61b when the CPU 61b realizes the same function as the signal generation circuit 211.

  The CPU 61b implements an acquisition unit 300, a determination unit 301, a count unit 302, and an adjustment unit 303 by executing a predetermined program.

  The acquisition unit 300 acquires the output voltage Vout every predetermined time. The determination unit 301 compares the acquired output voltage Vout with the voltages V1, V2, and −V2, and determines whether the output voltage Vout is within the range illustrated in FIG.

  The count unit 302 stores, as the count value N, the number of times that the output voltage Vout continuously enters the range from the voltage V2 to the voltage V1. Further, the count unit 302 stores the number of times that the output voltage Vout is continuously lower than the voltage −V2 as the count value M.

  The adjustment unit 303 outputs an instruction to start calibration when the count value N becomes “i” or the count value M becomes “j”. Further, when the output voltage Vout is higher than the predetermined voltage V1, the adjustment unit 300 outputs an instruction for starting the touchdown process.

  FIG. 18 is a flowchart illustrating an example of processing executed by the CPU 61b. The CPU 61b controls the signal processing circuits 21 and 22.

  First, the acquisition unit 300 acquires the output voltage Vout (S300). The determination unit 301 determines whether or not the output voltage Vout falls within the range of V2 <Vout <V1 (S301). When the output voltage Vout falls within the range of V2 <Vout <V1 (S301: YES), the count unit 302 increments the count value “N” (S302) and resets the count value “M” (S303). The adjustment unit 303 determines whether or not the count value N is “i” (S304). When the count value N becomes “i” (S304: YES), the adjustment unit 303 outputs an instruction to start calibration (S305), and the count unit 302 resets the count value N (S306). On the other hand, if the count value N is not “i” (S304: NO), the process S300 is executed.

  When the output voltage Vout does not fall within the range of V2 <Vout <V1 (S301: NO), the count unit 302 resets the count value N (S310), and the determination unit 301 determines that the output voltage Vout is the voltage V1. It is determined whether it is larger (S311). When the output voltage Vout is greater than the voltage V1 (S311: YES), the count unit 302 resets the count value M (S312), and the adjustment unit 303 outputs a touch-down process start instruction (S313). .

  When the output voltage Vout is smaller than the voltage V1 (S311: NO), the determination unit 301 determines whether or not the output voltage Vout is smaller than the voltage −V2 (S320). When the output voltage Vout is smaller than the voltage −V2 (S320: YES), the count unit 302 increments the count value M (S322), and the adjustment unit 303 determines whether the count value M has become “j”. Is determined (S323). When the count value M becomes “j” (S323: YES), the adjustment unit 303 outputs an instruction to start calibration (S324), and the count unit 302 resets the count value M (S325). On the other hand, if the count value M is not “j” (S323: NO), the process S300 is executed. Further, when the output voltage Vout is higher than the voltage −V2 (S320: NO), the process S300 is executed.

  When an instruction to start calibration is output, the control circuit 37 executes an offset adjustment process. For this reason, the offset of the output voltage Vout is suppressed.

  The touch switch device 10 to which the present invention is applied has been described above. In the present embodiment, the offset adjustment process is executed when there is no tapping. For this reason, it is possible to correctly control the offset included in the output voltage Vout.

  In addition, when the touch switch 20 is touched at the time of activation, the correction unit 74 corrects the data Dp. Therefore, the tapping determination unit 81 can accurately determine the presence or absence of tapping.

  Further, the correction unit 74 corrects the data Dp so that the rate of change of the data Dp increases as the difference Diff increases. Therefore, the correction unit 74 can bring the data Dp close to a desired value (data AD1) with high accuracy in a short time.

  Further, when the difference between the size of the data AD0 and the size of the data AD2 is larger than the predetermined threshold B2, the determination unit 91 does not instruct the change of the capacitance value Cp. Therefore, in the present embodiment, it is possible to cancel the offset while suppressing the influence of finger approach and the like.

  Also, as shown in FIG. 12, normal measurement is performed before the predetermined time TA has elapsed. Therefore, the response of the touch switch 20 can be improved.

  Also, the offset included in the output voltage Vout can be correctly controlled using the signal generation circuit 210 configured by hardware.

  Further, the signal generation circuit 210 can correctly control the offset included in the output voltage Vout even when the touch switch 20 is touched at the time of activation.

  In addition, the said Example is for making an understanding of this invention easy, and is not for limiting and interpreting this invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes equivalents thereof.

  For example, a touch panel may be used instead of the touch switch 20.

DESCRIPTION OF SYMBOLS 10 Touch switch apparatus 20 Touch switch 21, 22, 200 Signal processing circuit 23 Microcomputer 30 Multiplexer 31 Variable capacity 32 Register 33 Drive circuit 34 CV conversion circuit 35 AD converter (ADC)
36 Interface (IF) circuit 37, 211 Control circuit 40-44 Capacitor 60 Memory 61 CPU
70,300 Acquisition unit 71 Measurement unit 72 Touch town processing unit 73 Calibration processing unit 74 Correction unit 80 Touch determination unit 81 Tapping determination unit 81
82,303 Adjustment unit 90 Control unit 91,301 Determination unit 210 Signal generation circuit 220 Latch circuit 221-224, 240, 241 Comparison circuit 230, 231 Counter 250 AND circuit 251-253 OR circuit 254, 255 Inverter 302 Count unit SW1- SW4 switch

Claims (8)

Based on the output voltage from the voltage output circuit comprising: a capacitor capable of changing the capacitance value; a CV conversion circuit that outputs an output voltage corresponding to the capacitance value of the touch sensor; and an adjustment circuit that adjusts the capacitance value of the capacitor. A control circuit for controlling the adjustment circuit,
A first acquisition unit that acquires the output voltage when the CV conversion circuit is activated as a first output voltage;
A second acquisition unit that acquires the output voltage as the second output voltage each time an instruction to acquire the output voltage is input;
A first determination unit that determines whether a difference between a reference value corresponding to the first output voltage and the second output voltage is greater than a predetermined value;
When the difference is smaller than the predetermined value, an adjustment unit that causes the adjustment circuit to adjust the capacitance value of the capacitor so that the offset of the output voltage is removed;
A control circuit comprising: The control circuit according to claim 1,
A correction unit that corrects the reference value so that the reference value approaches the second output voltage when the difference between the reference value and the second output voltage is greater than the predetermined value;
A control circuit characterized by. The control circuit according to claim 2,
The correction unit is
When the difference between the reference value and the second output voltage is greater than the predetermined value, the rate at which the reference value approaches the second output voltage increases as the error between the reference value and the second output voltage increases. Correcting the reference value,
A control circuit characterized by. The control circuit according to any one of claims 1 to 3,
The adjustment unit is
When the difference between the reference value and the second output voltage is smaller than the predetermined value, the capacitance value of the capacitor is changed from the first capacitance value to the second capacitance value in the adjustment circuit so that the offset of the output voltage is removed. A first control unit to be changed;
A third acquisition unit that acquires, as a third output voltage, the output voltage when the capacitance value of the capacitor is changed from the first capacitance value to the second capacitance value;
A second control unit that causes the adjustment circuit to change the capacitance value of the capacitor from a second capacitance value to a first capacitance value;
The capacitance value of the capacitor is changed from the second capacitance value to the first capacitance value, and after a predetermined period has elapsed since the second acquisition unit acquired the second output voltage, the output voltage is changed to a fourth value. A fourth acquisition unit that acquires the output voltage;
A second determination unit for determining whether a difference between the second and fourth output voltages is greater than a predetermined threshold;
When the difference between the second and fourth output voltages is smaller than the threshold value, the capacitance value of the capacitor is a capacitance value in which the offset of the output voltage is reduced among the first and second capacitance values A third control unit for controlling the adjustment circuit;
Including,
A control circuit characterized by. The control circuit according to claim 4,
A third determination unit that determines whether or not the touch sensor has been touched based on the output voltage from when the second acquisition unit acquires the second output voltage to when the predetermined period elapses. about,
A control circuit characterized by. A capacitor capable of changing a capacitance value and a CV conversion circuit for outputting an output voltage corresponding to the capacitance value of the touch sensor;
A first acquisition unit that acquires the output voltage when the CV conversion circuit is activated as a first output voltage;
A second acquisition unit that acquires the output voltage as the second output voltage each time an instruction to acquire the output voltage is input;
A first determination unit that determines whether a difference between a reference value corresponding to the first output voltage and the second output voltage is greater than a predetermined value;
When the difference is smaller than the predetermined value, an adjustment unit that adjusts the capacitance value of the capacitor so that the offset of the output voltage is removed;
An offset adjustment circuit comprising: Based on the output voltage from the voltage output circuit comprising: a capacitor capable of changing the capacitance value; a CV conversion circuit that outputs an output voltage corresponding to the capacitance value of the touch sensor; and an adjustment circuit that adjusts the capacitance value of the capacitor. A control circuit for controlling the adjustment circuit,
An acquisition unit that acquires the output voltage each time an instruction to acquire the output voltage is input;
The output voltage acquired by the acquisition unit is within a predetermined range from a first value higher than a target value of the output voltage to a second value for determining whether or not the touch sensor is touched. A first determination unit for determining whether or not there is;
The adjustment circuit is configured to remove the offset of the output voltage when the first determination unit continuously determines that the output voltage acquired by the acquisition unit is within the predetermined range by the first number of times. An adjustment unit for adjusting the capacitance value of the capacitor;
A control circuit comprising: The control circuit according to claim 7,
A second determination unit for determining whether the output voltage acquired by the acquisition unit is lower than a third value lower than a target value of the output voltage;
The adjustment unit is
The first determination unit continuously determines that the output voltage acquired by the acquisition unit is within the predetermined range by the first number of times or is lower than the third value. 2 when the determination unit continuously determines the second number of times, the adjustment circuit adjusts the capacitance value of the capacitor so that the offset of the output voltage is removed,
A control circuit characterized by.

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