JP6172525B2 - Electrostatic touch switch device and noise detection method - Google Patents

Description

  The present invention relates to an electrostatic touch switch device and a noise detection method.

  As a conventional technique, an electrode that detects an operation performed on the operation surface by a change in capacitance value, and a determination unit that determines whether or not the finger is tilted based on a contact area where the finger contacts the operation surface And a coordinate input device that can change the amount of movement of the pointer relative to the amount of movement of the finger by changing the inclination of the contact surface of the finger is disclosed (for example, see Patent Document 1).

JP 2010-186880 A

  However, since the conventional coordinate input device detects an operation on the operation surface by a change in the capacitance of the electrode when a finger touches the operation surface, when noise is mixed from the electrode or the like, There has been a problem that an operation on the operation surface is erroneously detected due to a change in electric capacity.

  Accordingly, an object of the present invention is to provide an electrostatic touch switch device and a noise detection method in which erroneous detection of an operation on an operation surface due to the influence of noise is reduced.

  According to one aspect of the present invention, a generation unit that generates two electrode drive signals having different frequencies, and alternately outputs the generated two electrode drive signals, and the 2 that the generation unit outputs alternately The touch electrode charged by one electrode drive signal and the two electrode output signals output from the touch electrode are input in synchronization with the switching, and the two electrode output signals, which are analog signals, are converted into digital signals. An electrostatic touch switch device is provided that includes a conversion unit that performs digital conversion and a detection unit that detects the presence or absence of noise by calculating a difference between the two electrode output signals based on the digital signal.

  According to another aspect of the present invention, two electrode drive signals having different frequencies are generated, the generated two electrode drive signals are alternately switched and output, and the two electrodes output alternately The step of charging the touch electrode with a drive signal and the two electrode output signals output from the touch electrode are input in synchronization with the switching, and the two electrode output signals, which are analog signals, are converted into digital signals. There is provided a noise detection method including a step of converting and a step of detecting the presence or absence of noise by calculating a difference between the two electrode output signals based on the digital signal.

  ADVANTAGE OF THE INVENTION According to this invention, the misdetection of operation with respect to the operation surface by the influence of noise can be reduced.

FIG. 1 is a block diagram of an electrostatic touch switch device according to an embodiment of the present invention. FIG. 2 is a timing chart showing the timing for switching between the first electrode drive signal (330 kHz) and the second electrode drive signal (337 kHz). FIG. 3 is a graph showing the AD conversion value of the first electrode output signal (330 kHz) and the AD conversion value of the second electrode output signal (337 kHz) when the detection target approaches or contacts the operation surface. . FIG. 4 is a graph showing a difference value between the AD conversion value of the first electrode output signal and the AD conversion value of the second electrode output signal in FIG. FIG. 5 is a graph showing an AD conversion value of the first electrode output signal (330 kHz) when noise of 1 MHz is applied to the touch electrode. FIG. 6 is a graph showing an AD conversion value of the second electrode output signal (337 kHz) when 1 MHz noise is applied to the touch electrode. FIG. 7 is a graph showing a difference value between the AD conversion value of the first electrode output signal in FIG. 5 and the AD conversion value of the second electrode output signal in FIG.

[Embodiment]
FIG. 1 is a block diagram of an electrostatic touch switch device according to an embodiment of the present invention. The electrostatic touch switch device 1 includes an operation surface 10 that receives an operation by a detection object such as a finger, and first and second electrode drive signals S ₁ and S that are provided on the operation surface 10 and are analog signals to be described later. ₂ , the voltage follower 20 for impedance conversion of the first and second electrode output signals S ₁₁ and S ₂₁ output from the touch electrode 11, and the impedance conversion by the voltage follower 20. A conversion unit 30 that performs analog / digital conversion on the first and second electrode output signals S ₁₁ and S ₂₁ and outputs digital signals S ₃₁ and S ₃₂ , and a microcomputer 40 that controls each unit of the electrostatic touch switch device 1 Is provided.

  The electrostatic touch switch device 1 can perform an electrostatic touch switch operation by changing an electrostatic capacity when an operator touches the touch electrode 11 with a finger or the like. The touch electrode 11 can be applied to one or a plurality of touch electrodes 11 arranged in a row, two-dimensionally arranged in a crossing direction, or the like.

  The touch electrode 11 has, for example, a configuration in which two metal plates are arranged to face each other with a dielectric layer interposed therebetween. The operation surface 10 is formed with a dielectric protective layer such as a resin that is operated by a detection object such as a finger, and is configured such that the capacitance value of the touch electrode 11 increases when the finger or the like comes into contact. Note that the touch electrode 11 may have an operation surface on one of the electrodes, and the capacitance value of the touch electrode 11 may be increased or decreased when a detection target object comes into contact with the operation surface.

(Microcomputer)
The microcomputer 40 is a microcomputer composed of, for example, a CPU (Central Processing Unit) that performs operations, processing, and the like on acquired data. The microcomputer 40 functions as a pulse generator unit 41 and a detection unit 42 by operating in accordance with programs stored in a RAM (Random Access Memory) and a ROM (Read Only Memory) which are semiconductor memories.

The pulse generator unit 41 alternately switches the first and second electrode drive signals S ₁ and S ₂ and outputs them to the touch electrode 11 at predetermined intervals based on a clock signal or the like inside the microcomputer 40. The first and second electrode drive signals S ₁ and S ₂ are, for example, a rectangular wave and a trapezoidal wave with a duty ratio of 50. Also, the frequency of the first electrode driving signals _{S 1} is, for example, 330kHz, the frequency of the second electrode driving signal _{S 2} is, for example, 337KHz. The frequencies of the first and second electrode drive signals S ₁ and S ₂ are not limited to 330 kHz and 337 kHz, and can be applied if the respective frequencies are different. The pulse generator unit 41 is an example of a generation unit.

The detection unit 42 includes a counter that counts the number of pulses of the digital signals S _{31 and} S _{32 obtained} by analog / digital conversion of the first and second electrode output signals S ₁₁ and S ₂₁ output from the touch electrode 11. Can do. For example, the detection unit 42 is configured to input the first electrode output signal S ₁₁ from the first channel 421 and input the second electrode output signal S ₂₁ from the second channel 422.

  The detection unit 42 detects the capacitance value of the touch electrode 11, that is, the touch capacitance, by counting the pulses output according to the change in the capacitance due to the touch on the operation surface 10. The detection unit 42 detects contact or non-contact with the touch electrode 11 based on the detected touch capacitance.

The detection unit 42 is configured to detect noise mixed in the first and second electrode output signals S ₁₁ and S ₂₁ from the touch electrode 11 or the like. That is, the detection unit 42 detects noise mixed in from the touch electrode 11 and the like by calculating the difference in the number of pulses of the digital signals S ₃₁ and S ₃₂ input from the first and second channels 421 and 422, respectively. Thus, erroneous detection of operation on the operation surface 10 is suppressed.

(Conversion unit)
Converter 30, a second to the first electrode output signal S ₁₁ and the first conversion circuit 31 to an analog / digital converter, an analog / digital converting the second electrode output signal S ₂₁ outputted from the touch electrode 11 Conversion circuit 32, and a switch 33 for switching the connection between the voltage follower 20 and the first or second conversion circuit 31, 32.

The first and second conversion circuits 31 and 32 have one end connected to the switch 33 and the other end connected to the microcomputer 40. The first and second conversion circuits 31 and 32 convert the input voltage values of the first and second electrode output signals S ₁₁ and S ₂₁ into a digital signal S ₃ having an AD (analog / digital) conversion value. The first conversion circuit 31 outputs a digital signal S ₃₁ obtained by analog / digital conversion of the first electrode output signal S ₁₁ to the first channel 421 of the detection unit 42. Similar to the first conversion circuit 31, the second conversion circuit 32 outputs a digital signal S ₃₂ obtained by converting the second electrode output signal S ₂₁ to the second channel 422 of the detection unit 42.

The switch 33 has a terminal 33 a connected to the voltage follower 20, a terminal 33 b connected to the first conversion circuit 31, and a terminal 33 c connected to the second conversion circuit 32. Switch 33 is, for example, under the control of the microcomputer 40, the terminal 33a pulse Genet regulator unit 41 is synchronized to switch alternately the first and the electrode drive signals S ₁ and the second electrode driving signal S ₂ The connection with the terminal 33b or the connection between the terminal 33a and the terminal 33c is switched.

(Operation of electrostatic touch switch device)
Next, the operation of the electrostatic touch switch device 1 will be described. FIG. 2 is a timing chart showing the timing for switching between the first electrode drive signal (330 kHz) and the second electrode drive signal (337 kHz).

When power from a power source (not shown) to the electrostatic touch switch apparatus 1 is turned on, the pulse Genest regulator unit 41 generates a second electrode driving signal _{S 2} of the first electrode driving signal _{S 1} and 337kHz of 330kHz. When the pulse generator unit 41 outputs the first electrode drive signal S ₁ to the touch electrode 11, the first electrode drive signal S ₁ charges the touch electrode 11.

The touch electrode 11, and outputs a first electrode output signal S ₁₁ based on the first electrode driving signal S _1. The first electrode output signal S ₁₁ is impedance-converted by the voltage follower 20 and input to the conversion unit 30.

The conversion unit 30 connects the terminal 33 a and the terminal 33 b of the switch 33 based on the control of the microcomputer 40, and inputs the first electrode output signal S ₁₁ to the first conversion circuit 31. The first conversion circuit 31 converts the first electrode output signal S ₁₁ into a digital signal S ₃₁ and outputs the converted digital signal S ₃₁ to the first channel 421 of the detection unit 42.

Detector 42 based on the digital signal S ₃₁ inputted from the first channel 421, and calculates an average value of the values of the first electrode output signal S ₁₁ is held as AD conversion value. That is, as shown in FIG. 3, and calculates an average value of 16 times of sampling by the first electrode output signal S ₁₁ of 48μ seconds.

Pulse Genet regulator unit 41, when the first electrode driving signals S ₁ passes 48μ seconds after outputting the touch electrode 11 is switched from the first electrode drive signals S ₁ to the second electrode driving signal S ₂ Touch Output to the electrode 11. Converter 30, first the second electrode output signal S ₂₁ is input to the second conversion circuit 32, AD conversion value by calculating an average value of the voltage value of the second electrode output signal S ₂₁ switches the switch 33 Hold as. That is, as shown in FIG. 3, and calculates an average value of 16 times of sampling by the second electrode output signal S ₂₁ of 47μ seconds.

The detection unit 42 calculates the touch capacitance of the touch electrode 11 based on the held AD conversion values of the first and second electrode output signals S ₁₁ and S ₂₁ and detects the touch of the finger on the operation surface 10. The capacity determination process is performed. Further, the detection unit 42 calculates the AD conversion value of the first electrode output signal S ₁₁ which holds the difference value between the AD converted value of the second electrode output signal S _21, mixed from the touch electrode 11 and the like noise The difference process, which is a process for detecting the.

  If noise is not detected and the amount of change in the AD conversion value is equal to or greater than a certain value, the detection unit 42 determines that the touch capacitance of the touch electrode 11 has changed and detects contact of the finger with the operation surface 10. . If the detection part 42 detects the contact of the finger | toe to the operation surface 10, the microcomputer 40 will perform the operation | movement according to the instruction | indication from an operator based on a program etc.

Next, the operation of the electrostatic touch switch device 1 will be described in detail with reference to FIGS. FIG. 3 shows an AD conversion value of the first electrode output signal S ₁₁ (330 kHz) and an AD conversion value of the second electrode output signal S ₂₁ (337 kHz) when the detection target object contacts the operation surface 10. a graph, Figure 4 is a graph showing the AD conversion value of the first electrode output signal S ₁₁ in FIG. 3, the difference value between the AD converted value of the second electrode output signal S _21.

  FIG. 5 is a graph showing the AD conversion value of the first electrode output signal (330 kHz) when 1 MHz noise is applied to the touch electrode. FIG. 6 is a graph showing the first AD signal when the 1 MHz noise is applied to the touch electrode. 7 is a graph showing an AD conversion value of the second electrode output signal (337 kHz), and FIG. 7 shows an AD conversion value of the first electrode output signal in FIG. 5 and an AD conversion value of the second electrode output signal in FIG. It is a graph which shows the difference value with.

When the operator touches the operation surface 10 with the finger, the touch capacitance of the touch electrode 11 increases, and the voltage values of the first and second electrode output signals S ₁₁ and S ₂₁ decrease. Accordingly, as shown in FIG. 3, the AD conversion values of the first and second electrode output signals S ₁₁ and S ₂₂ also decrease. The difference value between the first and second electrode output signals S ₁₁ and S ₂₁ is calculated when the noise is not mixed from the touch electrode 11 or the like when the finger is brought into contact with the operation surface 10 as shown in FIG. It falls within the range of about 200 pulses.

Detector 42, a difference between the AD converted value of the AD conversion value and the second electrode output signal _{S 21} of the first electrode output signal _{S 11} is for example, a 300 pulses or less, and the first and second If the amount of change in the electrode output signals S ₁₁ and S ₂₁ is, for example, 1000 pulses or more, it is determined that the touch capacitance value has increased above the threshold value, and the touch of the finger on the operation surface 10 is detected.

For example, when radiation noise or conduction noise from the outside is mixed in the touch electrode 11, the capacitance value of the touch electrode 11 changes due to the noise, and therefore the first and second electrode output signals S ₁₁ and S _21. As shown in FIG. 5, the AD conversion value may deviate from the AD conversion value of the second electrode output signal S ₂₁ shown in FIG. 6 due to the influence of noise.

If the noise is mixed in the touch electrode 11, the difference value between the AD converted value and the AD conversion value of the second electrode output signal S ₂₁ of the first electrode output signal S _11, as shown in FIG. 7, For example, about 800 pulses. The difference value increases when noise is mixed in the touch electrode 11 or the like because the sensitivity for detecting noise differs depending on the frequency of the electrode drive signal.

When the difference value between the AD conversion value of the first electrode output signal S _{11 and} the AD conversion value of the second electrode output signal S ₂₁ is, for example, 500 pulses or more, the detection unit 42 does not operate the operation surface 10. It is determined that the capacitance value of the touch electrode 11 has changed due to noise.

That is, the detection unit 42, when the difference value between the AD converted value of the AD conversion value and the second electrode output signal S ₂₁ of the first electrode output signal S ₁₁ is large, the first and second electrode output Even if the change amount of the signals S ₁₁ and S ₂₂ is, for example, 1000 pulses or more, it is determined that the finger is not in contact with the operation surface 10.

(Effect of embodiment)
According to the present embodiment, the following effects can be obtained.
(1) By detecting an operation on the operation surface 10 using the first and second electrode drive signals S ₁ and S ₂ having different frequencies, noise mixed from the touch electrode 11 or the like is detected in the first and second electrodes. It can be detected based on the difference value between the output signals S ₁₁ and S ₂₂ . As a result, it is possible to detect an operation on the operation surface 10 with reduced erroneous detection due to noise.
(2) Since the noise is detected by the detection unit 42, it is not necessary to provide a filter for suppressing noise mixed from the touch electrode 11 on the operation surface 10, so that the electrostatic touch switch device 1 can be reduced in size and cost. Can be
(3) Since it is possible to accurately detect an operation on the operation surface 10 by reducing erroneous detection due to noise, the operability of the electrostatic touch switch device 1 is improved.
(4) In particular, when radiation noise including a specific frequency, spike noise, or the like is mixed from the touch electrode 11 or the like, the influence of noise can be effectively reduced.

[Modification]
The embodiments of the present invention are not limited to the above-described embodiments, and various modifications and implementations are possible without departing from the scope of the present invention. For example, the detection unit 42 receives the first and second electrode output signals S ₁₁ and S ₂₁ from the first and second channels 421 and 422, respectively. The first and second electrode output signals S ₁₁ and S ₂₁ may be input.

The conversion unit 30 may be configured to perform analog / digital conversion of the first and second electrode output signals S ₁₁ and S ₂₁ using a single conversion circuit.

DESCRIPTION OF SYMBOLS 1 ... Electrostatic touch switch apparatus, 10 ... Operation surface, 11 ... Touch electrode, 20 ... Voltage follower, 30 ... Conversion part, 31 ... 1st conversion circuit, 32 ... 2nd conversion circuit, 33 ... Switch, 33a- 33c ... terminal, 40 ... microcomputer, 41 ... pulse Genet regulator unit, 42 ... detection unit, 421 ... first channel, 422 ... second channel, S 1 _... first electrode driving signal, S 2 _... of the second Electrode drive signal, S ₁₁ ... First electrode output signal, S ₂₁ ... Second electrode output signal, S _31, S ₃₂ .. Digital signal

Claims (3)

A generating unit that generates two electrode drive signals having different frequencies, and alternately switches and outputs the generated two electrode drive signals;
A touch electrode that is charged by the two electrode drive signals output alternately by the generator;
A conversion unit that inputs two electrode output signals output from the touch electrode in synchronization with the switching, and performs analog / digital conversion of the two electrode output signals that are analog signals into digital signals;
A detection unit that detects the presence or absence of noise by calculating a difference between the two electrode output signals based on the digital signal;
Electrostatic touch switch device. The detection unit detects an operation on the operation surface of the touch electrode when the difference between the two electrode output signals is smaller than a predetermined value and the capacitance value of the touch electrode is changed.
The electrostatic touch switch device according to claim 1. Generating two electrode drive signals having different frequencies, switching the generated two electrode drive signals alternately, and outputting;
Charging the touch electrode with the two electrode drive signals output alternately;
Two electrode output signals output from the touch electrodes are input in synchronization with the switching, and the two electrode output signals, which are analog signals, are converted into digital signals from analog to digital, and
Detecting the presence or absence of noise by calculating a difference between the two electrode output signals based on the digital signal,
Noise detection method.

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