JP5549145B2 - Capacitance detection device - Google Patents

Description

  The present invention relates to detection of a capacitive element whose capacitance changes according to the approach or contact of an object such as a finger.

  In an electronic device such as a personal computer or a mobile phone, an input device using a change in capacitance is used. For example, in a flat pointing device, when capacitance elements having capacitance are arranged on the operation surface in a two-dimensional array and a finger is brought close to or in contact with the operation surface, the capacitance of the capacitance element at that position changes. . By detecting the change in capacitance, the input position and movement of the finger can be obtained. Patent Document 1 discloses a capacitance type sensor that detects such a change in capacitance.

JP 2004-132886 A

FIG. 1 is a block diagram illustrating a configuration example of a conventional capacitance detection device. Capacitance elements Cs having capacitance are arranged in a matrix of 4 rows × 4 columns. One electrode of the capacitive element Cs in each row direction is commonly connected to the signal lines X _{1 to} X _4, and the other electrode of the capacitive element Cs in each column direction is commonly connected to the signal lines Y _{1 to} Y _4. It is connected. These capacitive elements Cs are arranged below members such as the operation surface and operation panel of the electronic device, and when an object such as a finger approaches or comes into contact with the operation surface, the capacitance of the capacitive element Cs at that position. Changes.

The signal lines X _{1 to} X ₄ and the signal lines Y _{1 to} Y ₄ are connected to the capacitance detection unit 10 (10-1, 10-2,... 10-8). Figure, the capacitance detection unit 10-1 connected to an output of the signal lines Y ₁ are shown. The capacitance detection unit 10-1 controls the switching of the switching circuit 12 and the switching circuit 12, supplies a constant current to the capacitive element Cs, and outputs a triangular wave signal having a frequency corresponding to the capacitance of the capacitive element Cs. A programmable driver 14 to be generated, a Schmitt circuit 16 that binarizes the triangular wave signal, and a counter 18 that counts the number of pulses of the pulse signal output from the Schmitt circuit 16 and measures the frequency.

Switching circuit 12 has an input terminal connected to the signal line Y _1, and an output terminal connected to a Schmitt circuit 16, a power supply terminal connected to the constant current source, and a ground terminal connected to ground potential . The switching circuit 12 switches the connection among the input terminal, the output terminal, the power supply terminal, and the ground terminal. For example, when measuring the capacitance of the capacitive element Cs ₁ where the signal line Y ₁ and the signal line X ₁ intersect, the signal line X ₁ is connected to the ground terminal by the switching circuit 12, and the signal line Y ₁ is switched to the switching circuit 12. Is connected to the power supply terminal, and the capacitor Cs ₁ is charged with a charge from a constant current. Next, the switching circuit 12 reads the electric charge charged in the capacitive element Cs ₁ by connecting the input terminal connected to the signal line Y ₁ to the output terminal, and the frequency according to the capacitance of the capacitive element Cs _1. A triangular wave signal is generated. The frequency of the triangular wave signal is measured by the counter 18, and a change in capacitance is detected from the change in frequency.

  Capacitance elements whose capacitance has changed by scanning each of the 4 rows × 4 columns of capacitance elements at a constant period (capacitance measurement), that is, the position of the finger moving in time on the operation surface, Movement can be detected.

  Here, noise included in the triangular wave signal can be removed by a Schmitt circuit (hysteresis circuit) or a digital filter (not shown). However, with such noise countermeasures, if the frequency of the triangular wave signal and the noise frequency are the same, the noise cannot be sufficiently separated and removed, and a capacitive element whose capacitance has changed due to the influence of noise can be removed. There is a problem in that it is erroneously detected, and as a result, an accurate input position or movement on the operation surface cannot be obtained.

  Further, if the film thickness of the dielectric film of each capacitive element becomes non-constant due to manufacturing variation, the detection sensitivity of the capacitance is different, and the detection accuracy becomes uneven, leading to deterioration in operability and operation unevenness. In particular, if the difference in capacitance between capacitive elements is too large, it may be difficult to detect a change in capacitance.

  An object of the present invention is to solve such a conventional problem and to provide a capacitance detection device capable of accurately detecting a change in capacitance.

  The capacitance detection device according to the present invention includes a plurality of capacitive elements having one electrode and the other electrode facing the one electrode, and forming a capacitance between the one electrode and the other electrode, A change in capacitance of a capacitive element is detected in response to the approach or contact of an object, and a plurality of two-dimensionally arranged capacitive elements and a current from a constant current source are supplied to each capacitive element. Generating means for generating an output signal having a frequency corresponding to the capacitance of each capacitive element; detecting means for detecting a change in capacitance of the capacitive element based on the frequency of the output signal; and Determination means for determining whether or not the change in electric capacity is due to noise; and variable means for varying a current value supplied from the constant current source when the determination means determines that the change is due to noise.

  Preferably, the determination unit determines that the change in capacitance is due to noise when the amount of movement of the position of the capacitive element in which the change in capacitance has been detected within a certain period exceeds a threshold value. Preferably, the determination unit determines that the change in capacitance is due to noise when the change in the direction of the position of the capacitive element in which the change in capacitance is detected within a predetermined time exceeds a threshold value. . Preferably, the variable means refers to a table defining a relationship between a plurality of current values and a plurality of frequencies corresponding thereto, and supplies a current value corresponding to a frequency different from the frequency of the output signal from the constant current source. Let Preferably, the variable means supplies a current value having a frequency approximate to a harmonic of the frequency of the output signal from the constant current source.

  Preferably, the generation unit includes a switching element between the constant current source and a reference potential, and one electrode of the capacitive element is connected to a connection node between the constant current source and the switching element, and the switching element When is turned off, current is supplied from the constant current source to the capacitive element, and when the switching element is turned on, supply of current from the constant current source to the capacitive element is stopped. The generating unit may further include a switching circuit that switches each connection between the connection node and the plurality of capacitive elements. The generating means generates a triangular wave signal as the output signal, and the generating means further includes a binarizing circuit for binarizing the triangular wave signal and a filter for removing noise of the binarized signal. Can do. Preferably, the constant current source includes a current mirror circuit capable of supplying a plurality of current sources, and the variable means selects a plurality of current sources of the current mirror circuit.

  Furthermore, the capacitance detection device according to the present invention includes a plurality of capacitive elements that have one electrode and the other electrode facing the one electrode, and that form a capacitance between the one electrode and the other electrode. , Which detects a change in capacitance of a capacitive element in accordance with the approach or contact of an object, and supplies a plurality of capacitive elements arranged in a two-dimensional manner and current from a constant current source to each capacitive element Generating means for generating an output signal having a frequency corresponding to the capacitance of each capacitive element; and a capacitive element generated by the generating means in a state where an object is not approaching or in contact with the plurality of capacitive elements Obtained by the generating means using the scanning means for comparing the frequency difference between the output signal and the reference frequency of the reference capacitive element in the memory and the frequency difference stored in the storage means. Output signal Having a correction means for correcting the frequency, and detection means for detecting a change in capacitance based on the frequency of the corrected output signal.

  Preferably, the reference capacitive element is one capacitive element selected from the plurality of capacitive elements. Preferably, the reference capacitive element is a capacitive element having a known capacitive element connected to the outside. Preferably, the scanning means is executed when the electrostatic capacity detection device is turned on. Preferably, the capacitance detection device further includes calculation means for calculating a position or coordinates of the capacitive element in which a change in capacitance is detected by the detection means. Said electrostatic capacitance detection apparatus can be utilized for a position input device.

  According to the present invention, when it is determined that the detected change in capacitance is due to noise, by changing the current value of the constant current source, the frequency of the output signal can be made different from the noise frequency, Thereby, noise can be separated and removed from the output signal, and a change in capacitance can be accurately detected. Further, by correcting the variation in the capacitance of each capacitive element, it is possible to detect the change in capacitance more accurately.

It is a block diagram which shows the structure of the conventional electrostatic capacitance detection apparatus. It is a block diagram which shows the structure of the electrostatic capacitance detection apparatus which concerns on 1st Example of this invention. It is a figure which shows the example of a triangular wave generation circuit and a waveform diagram. It is a figure which shows the example of a variable current pattern table. It is a figure which shows the example of the current mirror circuit of a constant current source. It is a figure which shows the example of the operation | movement flow for the electrostatic capacitance detection by a microcontroller. It is a figure which shows the example of the determination flow of whether it is noise. It is a block diagram which shows the structure of the electrostatic capacitance detection apparatus which concerns on 2nd Example of this invention. It is an operation | movement flow of the electrostatic capacitance detection apparatus which concerns on 2nd Example of this invention. It is an example of a correction table.

  Hereinafter, a capacitance detection device according to the best mode of the present invention will be described with reference to the drawings.

  FIG. 2 is a block diagram showing the configuration of the capacitance detection apparatus according to the first embodiment of the present invention. In the figure, a representative capacitive element Cs of a plurality of capacitive elements is illustrated. The capacitance detection apparatus 100 according to the present embodiment receives a switching circuit 110 connected to the capacitive element Cs, a programmable drive circuit 120 connected to the switching circuit 110, and a triangular wave signal generated from the programmable drive circuit 120. Schmitt built-in binarization circuit 130, digital filter 140 connected to the output of binarization circuit 130, frequency measurement unit 150 for measuring the frequency of the rectangular wave signal output from digital filter 140, and programmable drive circuit 120, a variable current control unit 160 that varies a constant current, a variable current pattern table 170 that defines a relationship between a plurality of current values that can be supplied from a constant current source and frequencies corresponding thereto, and a change in capacitance And a microcontroller 180 that performs detection and other controls.

  For example, as shown in FIG. 1, the plurality of capacitive elements Cs are arranged in a matrix of 4 rows × 4 columns below a member that provides an operation surface of the electronic device. The switching circuit 110 scans the plurality of capacitive elements Cs at a constant cycle. That is, the switching circuit 110 switches the connection between each capacitive element Cs and the drive circuit 120 so that the capacitance of each capacitive element is measured in order at a constant period. The operation of the switching circuit 120 may be controlled by the microcontroller 180 or may be performed by the programmable drive circuit 120, for example.

  The programmable drive circuit 120 includes a constant current source 122 and a switching element 124 that can vary a supplied current value, and controls the on / off of the switching element 124 to control the supply of current to the capacitor element Cs. Then, a triangular wave signal having a frequency corresponding to the capacitance of the capacitive element Cs selected by the switching circuit 110 is generated.

3A is a circuit example for generating a triangular wave signal, and FIG. 3B is a waveform diagram of the node N and the switch SW. As shown in the figure, a switch SW124 is connected in series to the constant current source 122, and a capacitive element Cs is selectively connected to these connection nodes N. The node N is connected to the inverting input terminal of the comparator COMP1, and the other non-inverting input terminal is connected to the potential V _d1 that determines the upper limit of the triangular wave signal. Further, the node N is connected to the non-inverting input terminal of the comparator COMP2, and the other inverting input terminal is connected to the potential _Vd2 that determines the lower limit of the triangular wave signal. The switch SW is turned on in response to the comparator COMP1 being inverted to L level, and is switched to the off state in response to the comparator COMP2 being inverted to L level.

  The Schmitt built-in binarization circuit 130 preferably includes a triangular wave signal and a comparator for comparing with a reference voltage, and converts the triangular wave signal into a rectangular wave signal. The digital filter 140 includes, for example, an IIR filter or an FIR filter, and removes a noise component included in the binarized signal. The frequency measurement unit 150 includes a counter, for example, and measures the frequency by counting the pulses of the rectangular wave signal output from the digital filter 140.

The variable current pattern table 170 stores, for example, a table as shown in FIG. 4 in the memory. The table, the current value _{I 1,} I 2, which is capable of supplying a constant current source 122, · · · _{I n} and the frequency _{f 1,} f 2 corresponding thereto, defines the relationship between the · · · _{f n} . The variable current control unit 160 refers to the variable current pattern table 170 and selects a current value that has a frequency different from the frequency of the triangular wave signal when it is determined that the detection of the change in capacitance is due to noise. Then, this is supplied from the constant current source 122.

  The constant current source 122 is preferably composed of a current mirror circuit. FIG. 5 shows a configuration example of the constant current source and variable current control unit 160. The current mirror circuit includes a MOS transistor Q1 and a plurality of MOS transistors Q2 to Qn having the same characteristics. The gate of the transistor Q1 is connected to the source, and the drain is connected to the node N. The gate of the transistor Q2 is connected in common to the gate of the transistor Q1, and the drain thereof is connected to the node N so as to be in parallel with the transistor Q1. The gates of the transistors Q3 to Qn are also connected to the gate of the transistor Q1 so as to be in parallel with the transistor Q1, and their drains are connected via switches SW1, SW2,... SWn-1. Connected to node N. The variable current control unit 160 varies the current value from the constant current source by controlling opening and closing of the switches SW1 to SWn-1. For example, when all the switches SW1 to SWn-1 are turned off, the node N is supplied with two drain currents Id × 2 of the transistors Q1 and Q2, and when the switches SW1 to SWn-1 are turned on, the node N In N, n drain currents Id × n are supplied to the node N.

  The microcontroller 180 includes a ROM or a RAM, and stores a program for detecting a change in capacitance element, that is, capacitance. FIG. 6 shows a detection flow when the microcontroller 180 executes the program. First, the microcontroller 180 refers to the variable current pattern table and sets a current value corresponding to a predetermined frequency in the constant current source 122 (step S101). In response to this, the variable current control unit 160 controls the switches SW1 to SWn-1 of the constant current source 122.

  Next, the microcontroller 180 controls the switching operation of the switching circuit 110, and scans each capacitive element so that the capacitance of each capacitive element is measured at a constant period (step S102). That is, the capacitance element is selected by the switching circuit 110, and further, the current from the constant current source is supplied to the selected capacitance element during the period when the switching element is turned off. A triangular wave signal having a frequency is generated. The triangular wave signal is binarized by the binarization circuit 130, the noise of the rectangular wave signal is removed by the digital filter 140, the frequency of the rectangular wave signal is measured by the frequency measuring unit 150, and the measurement result is sent to the microcontroller 180. Provided.

The microcontroller 180 detects whether or not the capacitance of the capacitive element has changed based on the measured frequency (step S103). Next, the microcontroller 180 determines whether or not the change in capacitance is due to the influence of noise (step S104). When determining that the change in capacitance is due to the influence of noise, the microcontroller 180 refers to the variable current pattern table 170 and selects a frequency that is different from the set frequency or the frequency measured by the frequency measurement unit 150. Select a current value that For example, the current value that is currently set When a (frequency f ₁₎ in I _1, the frequency f ₂ different transformed frequency or the frequency f ₁ is set to the current value to be selected. Preferably, the newly selected frequency is a harmonic of the measured frequency.

  The variable current control unit 160 varies the current value supplied from the constant current source 122 based on the selected frequency (step S105). The variable current control unit 160 selects a switch to be turned on from the switches SW1 to SWn-1 in the current mirror circuit shown in FIG. 5, for example. Since the current value of the constant current source 122 is varied, the frequency of the triangular wave signal is changed, and the noise included in the triangular wave signal is effectively removed by the Schmitt binarization circuit 130 and the digital filter 140.

  Next, FIG. 7 shows a flow for determining whether or not the change in capacitance is noise. Here, an object moving on the operation surface is a finger. When a change in capacitance is detected, the microcontroller 180 monitors the capacitive element in which the change in capacitance is detected within a certain period from the detection, and calculates the movement amount and movement direction of the finger during that period. (Step S201). Next, when the movement amount of the finger is larger than a predetermined threshold value S1, it is determined that the change in capacitance is due to the influence of noise (step S205). Even if the movement amount of the finger is equal to or less than the threshold value S1, it is determined that the influence of noise is caused when the movement direction changes or when the movement direction change amount exceeds the threshold value S2 (step S205). .

  Preferably, the threshold values S1, S2 are determined from experimental data. In a preferred example, the capacitance of the capacitive element is about 30 pF, and the amount of change in capacitance when a finger touches or approaches is about 0.2 pF. The amount of change in signal due to noise input to the element corresponds to a change in capacitance of about 10 pF, which is significantly larger than the change in capacitance when a normal operation is performed. The amount of finger movement when erroneously detected due to the influence of noise tends to be significantly greater than the amount of movement when a normal operation is performed. In addition, the movement direction when a normal operation is performed is almost linear, whereas the finger movement direction detected due to the influence of noise is non-linear and the amount of change is large. ing.

  In the above determination flow, the amount of movement and the direction of movement are individually used as criteria for determination. However, when both the amount of movement and the direction of movement satisfy the conditions, it may be determined that the influence of noise. That is, when the movement amount is larger than the threshold value S1 and the change amount in the movement direction is larger than the threshold value S2, it is determined that the influence of noise. Further, in the determination operation of whether or not the noise, the determination flow shown in FIG. 7 is repeated a plurality of times, and when it is determined that the influence of noise is found in all the determination results, the determination is made as the influence of noise and the determination accuracy is improved. It may be.

  Next, a second embodiment of the present invention will be described. FIG. 8 shows the configuration of the capacitance detection apparatus according to the second embodiment, and the same components as those in FIG. 2 are given the same reference numerals.

  The amount of change in capacitance when an object such as a finger approaches or comes into contact with the capacitance of the capacitive element is small. For example, when the capacitance of the capacitive element is about 30 pF, the amount of change in the capacitance can be about 0.2 pF. For this reason, if there is a large variation in capacitance between capacitive elements, it will be difficult to determine whether the capacitance is due to variation or due to contact with an object. May not be detected. On the other hand, the thickness of the dielectric film of the capacitive element is affected by the film forming process during manufacturing, and it is difficult to make all the capacitances uniform. The second embodiment has a function of correcting (calibrating) variations in capacitance between capacitive elements that occur in the manufacturing stage or the like.

The capacitance detection apparatus 100A according to the second embodiment includes a selector 200 that scans a plurality of capacitance elements C _{1 to} C _n arranged in a two-dimensional matrix, and the capacitance of the capacitance elements scanned by the selector 200. And a correction table 210 for correcting the variation in capacity.

  As will be described later, the microcontroller 180 measures the capacitance of all the capacitive elements, and stores correction data for correcting variations in capacitance generated during manufacturing or the like in the correction table 210. The measured capacitance is corrected using the corrected data.

  FIG. 9 is a flowchart for explaining the capacitance correcting operation in the second embodiment. When the power is turned on, the microcontroller 180 controls the selector 200 to scan all the capacitive elements (steps S301 and S302). When this scanning is performed, it is assumed that an object such as a finger is not approaching or touching the capacitive element. Next, the microcontroller 180 measures the capacitance of the operated capacitive element (step S303). The capacitance is measured in the same way as in the first embodiment. That is, a triangular wave signal having a frequency corresponding to the capacitance of each capacitive element is generated, the frequency of the triangular wave signal is measured by the frequency measuring unit 150, and the capacitance of each capacitive element is measured.

Next, the microcontroller 180 calculates the variation in capacitance between the capacitive elements (step S304). If the capacitances of all the capacitive elements are equal, all the frequencies measured for each capacitive element are equal. The microcontroller 180 is a single capacitive element from among a plurality of capacitive elements selected as a reference capacitor element C _ref, is the variation of the relative capacitance between the reference capacitance element C _ref and another capacitive element The frequency difference Δf is obtained.

Next, the microcontroller 180 stores the obtained frequency difference Δf in the correction table 210 (step S305). FIG. 10 shows an example of the correction table. In this example, frequency differences Δf _{2 to} f _n between the reference capacitive element C _ref and the other capacitive elements C _{2 to} C _n when the capacitive element C ₁ is the reference capacitive element C _ref are shown. The storage of the frequency difference Δf in the correction table 210 may be performed when the power is turned on, and may be periodically updated during operation.

When actually measuring the capacitance of the capacitive element, the microcontroller 180 corrects the frequency measured by the frequency difference Δf in the correction table and detects the capacitive element whose capacitance has changed (step S306). For example, when the frequency _{f 2} of the capacitor _{C 2} is measured, corrected frequency _{f 2H is} a _{f 2H = f 2 + Δf 2} . The frequencies of the other capacitive elements C _{2 to} C _n are similarly corrected. As a result, the variation in the capacitance of each capacitive element is corrected, and the capacitive element in which the static electricity can be accurately detected can be detected.

The capacitance detection device of the present embodiment is applied to an input device such as a pointing device. Since the capacitance measurement of the pointing device is operated with a human finger, noise is generated due to capacitive coupling with the capacitance of the measurement target. According to the capacitance detection device of the first embodiment,
(1) Since it operates so as to avoid noise frequency, stable operation is possible even with variable noise.
(2) Since the current value of the conventional constant current source has been changed so that it can be varied, it does not add significant functions or increase costs.
(3) Since the noise removal filter need not have a large order, the circuit scale can be reduced and the cost can be reduced.
(4) Since the filter is simple, there is an effect that the operating current can be reduced.
Therefore, it is possible to measure the capacitance stably even in different noise environments, and it is possible to construct a pointing device with a good operational feeling, and to increase the cost and operating current by partially changing existing circuits and simple filters. Operation with low current consumption is possible.

In addition, the capacitance panel and the switch have a large variation in manufacturing, and there are variations in voltage, temperature, and aging, which affects the operational feeling and detection accuracy. The capacitance detection device of the second embodiment According to
(1) The operational feeling and detection accuracy are improved by correcting the variation in capacitance.
(2) The overhead head for correcting the variation in capacitance is small and can be configured at low cost.
(3) Since variation in capacitance can be corrected electrically, an electronic device or system can be configured with an inexpensive electrostatic switch panel.
(4) By correcting the variation in capacitance, there is an effect that the resolution is substantially improved.

In the above example, a reference capacitive element is selected from a plurality of capacitive elements, and the relative capacitance variation between the capacitive elements is obtained and corrected. However, the reference capacitive element is externally provided. A connected capacitive element may be used. For example, a calibration reference capacitance element C _ref whose absolute value of capacitance is known is connected to the selector 210, and the frequency according to the capacitance of the measurement capacitance element and the reference capacitance element C _ref is measured. The frequency difference Δf may be obtained and the obtained frequency difference Δf may be stored in the correction table.

  In the above example, the variation in capacitance is measured when the power is turned on, and this is stored in the correction table. Then, the frequency difference in the correction table may be updated. For example, the capacitance varies when the temperature of the capacitive element changes during the operation of the capacitance detection device or when the power supply voltage of the device changes. Therefore, the capacitance varies at an appropriate timing during the operation. Is measured, and the content of the correction table is updated, so that the variation in capacitance during operation can be compensated. In addition, the correction table only needs to be able to store the frequency difference every time the variation is measured, and thus can be configured using a volatile memory such as SRAM.

In the above embodiment, an example using a circuit that generates a triangular wave signal as shown in FIG. 3 is shown. However, a circuit that converts capacitance into a frequency is configured using other integrating circuits and differentiating circuits. May be.
Further, in the above-described embodiment, an example in which a plurality of capacitive elements are arranged in a matrix of 4 rows × 4 columns is illustrated, but the arrangement of the plurality of capacitive elements is, for example, 12 rows × 16 columns, etc. Other combinations of matrices may be used.
The capacitance of the capacitive element and the amount of change of the capacitance when the finger touches or approaches are illustrated as about 30 pF and about 0.2 pF, respectively. It may vary depending on the operating conditions.

  Although the preferred embodiments of the present invention have been described in detail, the present invention is not limited to the specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

100, 100A: Capacitance detection device 110: Switching circuit 120: Programmable drive circuit 122: Constant current source 124: Switching element 130: Schmitt built-in binarization circuit 140: Digital filter 150: Frequency measurement unit 160: Variable current control unit 170: Variable current pattern table 180: Microcontroller

Claims (14)

It has one electrode and the other electrode opposite to the one electrode, and includes a plurality of capacitor elements that form a capacitance between the one electrode and the other electrode. A capacitance detection device for detecting a change in capacitance,
A plurality of capacitive elements arranged in a two-dimensional array ;
Signal generating means for supplying a current from a constant current source to each capacitive element, and generating an output signal having a frequency corresponding to the capacitance of each capacitive element;
Detecting means for detecting a change in capacitance of the capacitive element based on the frequency of the output signal;
Determination means for determining whether the detected change in capacitance is due to noise;
When it is determined to be due to noise by the determination unit, a current value varying means for Ru changing the value of the current supplied from the constant current source,
Including
The determination means determines that the change in the capacitance is a noise when the amount of movement of the position of the capacitive element in which the change in the capacitance is detected within a predetermined period exceeds a predetermined threshold value. Capacitance detection device that determines that the
Capacitance detection device. It has one electrode and the other electrode opposite to the one electrode, and includes a plurality of capacitor elements that form a capacitance between the one electrode and the other electrode. A capacitance detection device for detecting a change in capacitance,
A plurality of capacitive elements arranged in a two-dimensional array;
Signal generating means for supplying a current from a constant current source to each capacitive element, and generating an output signal having a frequency corresponding to the capacitance of each capacitive element;
Detecting means for detecting a change in capacitance of the capacitive element based on the frequency of the output signal;
Determination means for determining whether the detected change in capacitance is due to noise;
A current value variable means for changing a current value supplied from the constant current source when it is determined by the determination means to be noise;
Including
The determination unit is configured to change the capacitance when the amount of change in the direction of the position of the capacitance element in the two-dimensional array in which the capacitance change is detected within a predetermined time exceeds a predetermined threshold value. Capacitance detection device that determines that noise is caused by noise. The capacitance detection device according to claim 1 or 2,
The current value varying means refers to a table that defines a relationship between a plurality of current values and a plurality of frequencies corresponding thereto, and supplies a current value corresponding to a frequency different from the frequency of the output signal from the constant current source. Capacitance detection device. The capacitance detection device according to claim 3,
The current value variable unit is a capacitance detection device that supplies a current value having a frequency approximate to a harmonic of the frequency of the output signal from the constant current source. The capacitance detection device according to claim 1 or 2,
Said signal generating means, said includes a switching element connected between the constant current source and the reference potential, the one electrode of the capacitor, is connected the connection node between the constant current source and the switching element, wherein A capacitance detection device that supplies current from the constant current source to the capacitive element when the switching element is turned off, and stops supply of current from the constant current source to the capacitive element when the switching element is turned on. . The capacitance detection device according to claim 5,
It said signal generation means further comprises a switching circuit for switching each of the connection between the connection node and a plurality of capacitive elements, the electrostatic capacitance detection device. The capacitance detection device according to claim 5 or 6,
Filter the signal generating unit generates a triangular wave signal as the output signal, which is further to the signal generating means, for removing noise in the binary circuit and binarized signal for binarizing the triangular wave signal A capacitance detection device. The capacitance detection device according to claim 1, 2, 3, or 4,
Said constant current source, a plurality of current source comprises a current mirror circuit which can supply, said varying means selects a plurality of current sources of the current mirror circuit, the electrostatic capacitance detection device. It has one electrode and the other electrode opposite to the one electrode, and includes a plurality of capacitor elements that form a capacitance between the one electrode and the other electrode. A capacitance detection device for detecting a change in capacitance,
A plurality of capacitive elements arranged in a two-dimensional array ;
Signal generating means for supplying a current from a constant current source to each capacitive element, and generating an output signal having a frequency corresponding to the capacitance of each capacitive element;
The object is approaching young properly into a plurality of capacitive elements in a state not in contact, as compared to the reference frequency of the frequency and the reference capacitance element of the output signal of the capacitor which is generated by said signal generating means, the frequency of the reference frequency Storage means for storing the difference in memory,
The difference between the frequencies stored in the storage means is used so that the frequencies of the plurality of output signals corresponding to the plurality of capacitance elements when an object is not in proximity to or in contact with the plurality of capacitance elements are equal. Correction means for correcting the frequency of the output signal obtained by the signal generation means;
Detecting means for detecting a change in capacitance of the capacitive element based on the frequency of the corrected output signal;
Including, electrostatic capacitance detection device. The capacitance detection device according to claim 9,
The capacitance detection device, wherein the reference capacitive element is one capacitive element selected from the plurality of capacitive elements. The capacitance detection device according to claim 9,
The electrostatic capacity detection device, wherein the reference capacitive element is a capacitive element having a known capacitive element connected to the outside. The capacitance detection device according to claim 9 ,
The capacitance detection device, wherein the difference is stored in a memory when the capacitance detection device is powered on. The capacitance detection device according to any one of claims 1 to 12,
It said location within said two-dimensional array of capacitive elements which change in capacitance is detected by the detecting means or further includes a calculating means for calculating the coordinates, the electrostatic capacitance detection device. One claims 1 to 13 What Re comprises or electrostatic capacitance detection device according, position input device.

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