JP2005301974A - Coordinate position detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coordinate position detector of a capacity coupling system touch panel improved so as to shorten detection time and to reduce power consumption. <P>SOLUTION: The coordinate position detector of the capacity coupling system touch panel comprises means 22, 24 for charging coupling capacity, means 27, 28 for converting charged amount of charges into voltage, means 29, 30 for sampling the converted voltage, means 22, 24 for returning the charged coupling capacity to a state before charging and means 27, 28 for returning the converted voltage to a state before charging. An intermittent operation is made possible by each means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a coordinate position detecting device for a capacitively coupled touch panel, and more specifically, an improved coordinate position detecting device for a capacitively coupled touch panel that can reduce detection time and power consumption. About. The present invention also relates to a coordinate position detection apparatus improved so as to compensate for the influence of external noise applied to the touch panel. A touch panel is an input device used for direct input to a display, and is a display device such as an LCD. Unlike a mouse, it is a pointing device that can input absolute coordinates.

  First, the basic principle of the position detection method using the capacitive coupling method employed in the present invention will be described with reference to FIG.

    In FIG. 5, a one-dimensional resistor sandwiched between the electrode A and the electrode B is shown for the sake of simplicity. In an actual display device, a touch panel having a two-dimensional spread exhibits the same function as this one-dimensional resistor.

  Each of the electrode A and the electrode B is connected to a resistance r for current-voltage conversion. The electrodes A and B are connected to the position detection circuit via a switching circuit.

  In the position detection mode, a voltage having the same homologous potential (AC e) is applied between the electrode A and the ground and between the electrode B and the ground. At this time, since the electrode A and the electrode B are always at the same potential, no current flows between the electrode A and the electrode B.

  It is assumed that the position C is touched with a finger or the like. Here, the resistance from the contact position C to the electrode A by the finger is R1, the resistance from the contact position C to the electrode B is R2, and R = R1 + R2. At this time, when the impedance of the human finger is Z, the current flowing through the electrode A is i1, and the current flowing through the electrode B is i2, the following equation is established.

  e = r * i1 + R1 * i1 + (i1 + i2) Z (Formula 1)

  e = r * i2 + R2 * i2 + (i1 + i2) Z (Formula 2)

  Although induction is omitted, Equation (3) is obtained from Equation 1 and Equation 2 above.

  R1 / R = (2r / R + 1) i2 / (i1 + i2) -r / R (Formula 3)

  Since r and R are known, if the current i1 flowing through the electrode A and the current i2 flowing through the electrode B are obtained by measurement, R1 / R can be determined from Equation 3, and the coordinate position can be determined accordingly. it can. Note that R1 / R does not depend on the impedance Z including a person touching with a finger. Therefore, as long as the impedance Z is not zero and infinite, Equation 3 is established, and changes and states due to people and materials can be ignored.

  Next, the case where the relational expression in the one-dimensional case is expanded to the two-dimensional case will be described with reference to FIGS. 6 and 7. Here, as shown in FIG. 6, four electrodes A, B, C, and D are formed at four corners of the touch panel 11. These electrodes A to D are connected to a position detection circuit.

  Referring to FIG. 7, an alternating voltage having the same homologous potential is applied to electrodes A, B, C, and D at the four corners of touch panel 11. The currents that flow through the four corners of the touch panel 7 when touched by a finger or the like are denoted by i1, i2, i3, and i4, respectively. In this case, the following expression is obtained by the same calculation as the above-described calculation.

  X = k1 + k2 · (i2 + i3) / (i1 + i2 + i3 + i4) (Formula 4)

  Y = k1 + k2 · (i1 + i2) / (i1 + i2 + i3 + i4) (Formula 5)

  Here, X is the X coordinate of the contact position on the counter conductive film, and Y is the Y coordinate of the contact position on the counter conductive film. K1 is an offset, and k2 is a magnification. k1 and k2 are constants that do not depend on human impedance.

  Based on the above formulas 4 and 5, the contact position can be determined from the measured values of i1 to i4 flowing through the four electrodes.

  FIG. 8 is a configuration diagram of a conventional coordinate position detection circuit using the principle of such capacitive coupling system (see, for example, Patent Document 1).

  Referring to FIG. 8, the coordinate position detection circuit includes four current change detection circuits 1. The current change detection circuit 1 measures a current flowing between each of the electrodes 7, 8, 9, and 10 of the resistance film r of the touch panel and the ground. The current change detection circuit 1 detects a change in impedance between each electrode 7, 8, 9, 10 and the ground due to contact with a finger or the like as a change in current, and the coordinate position is detected based on this change. Since the impedance of a finger or the like is composed of a capacitive component, an AC voltage is applied to each electrode 7, 8, 9, 10 by the AC oscillation circuit 5, and an AC voltage is applied to each electrode 7, 8, 9, 10. Current flows. The output of the detection circuit 1 is subjected to amplification and band-pass filtering processing by the analog signal processing circuit 2. The output of the analog signal processing circuit (hereinafter referred to as a band-pass filter) 2 is detected by the detection filtering circuit 3 and then input to the noise canceling DC circuit 4. The noise elimination DC circuit 4 converts the output of the detection filtering circuit 3 to DC, and a value proportional to the current flowing through each electrode 7, 8, 9, 10 is input to the control device 6. The control device 6 detects the coordinate position based on this value.

In addition, as shown in FIG. 9, there has been proposed an apparatus that detects a coordinate position by detecting a response of a pulse applied to a touch panel using a transformer (see, for example, Patent Document 2).
JP 2003-66417 A Japanese Patent Laid-Open No. 7-219708

  The conventional coordinate position detection apparatus is configured as described above. However, in the disclosed technique of Patent Document 1, since it is a two-dimensional case, coordinates are obtained by detecting currents in four directions. However, since the signal applied here is alternating current, only one detection is performed. Then, it is extremely unstable as data (signal waveform). Therefore, in order to obtain decent data, it is not practical unless the AC signal is taken a plurality of times and averaged. Therefore, in order to obtain the average, an operation for a certain period is necessary, and the operation time of the circuit is required correspondingly, and there is a problem that the power consumption as the system increases.

  In addition, the technique disclosed in Patent Document 2 has a problem that it is difficult to integrate into an IC by using a transformer.

  Further, the conventional coordinate position detection apparatus has the following problems.

  Referring to FIG. 10, bandpass filter 2 uses the oscillation frequency of AC oscillation circuit 5 as a passband, and components other than the oscillation frequency are removed. Therefore, bandpass filter 2 functions as noise compensation means. Therefore, the external noise received by the touch panel 11 is output as Vnoise 1 by the detection circuit 1, but the component of Vnoise 1 is deleted by the bandpass filter 2. However, the noise component in the vicinity of the pass band of the bandpass filter 2 is not deleted by the bandpass filter 2, but passes through the bandpass filter 2 and is converted into an output signal as a change in DC level by the noise elimination DC circuit 4. There was a problem of appearing.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a coordinate position detection device that can reduce current consumption by shortening detection time and can be integrated into an IC. And

  Another object of the present invention is to provide a coordinate position detection apparatus capable of compensating for noise including noise near the center frequency of a bandpass filter.

  The coordinate position detection apparatus of the present invention includes a unit for charging a coupling capacitor, a unit for converting a charged amount of charge into a voltage, a unit for sampling the converted voltage, and a state before the charged coupling capacitor is charged. And means for returning the converted voltage to the state before charging, and each means is capable of intermittent operation. By repeating the operation of each means, the coordinate position can be continuously detected. Each of the above means is realized by using a resistor, a capacitor, and a transistor that can be integrated into an IC.

  A coordinate position detection apparatus according to another aspect of the present invention is obtained by replacing the means for charging the coupling capacitance with a means for discharging. That is, the coordinate position detecting device includes a unit for discharging the coupling capacitance, a unit for converting the discharged charge amount into a voltage, a unit for sampling the converted voltage, and the discharged coupling capacitance in a state before discharging. And a means for returning the converted voltage to the state before discharge, and each means is capable of intermittent operation.

  According to a preferred embodiment of the present invention, there is further provided means for compensating for the current flowing to the parasitic capacitance of the touch panel among the current flowing during charging.

  According to still another aspect of the present invention, there is provided a coordinate position detection apparatus including a noise receiving unit that receives external noise and an output signal of the touch panel in a coordinate position detection apparatus of a capacitively coupled touch panel that determines a contact position from an output signal of the touch panel. And subtracting the noise signal received by the noise receiving means. With this configuration, the influence of noise can be compensated.

  According to a further preferred embodiment of the present invention, there is further provided means for adjusting the gain of the noise signal. With this configuration, it is possible to perform noise compensation with high accuracy.

  According to the coordinate position detection apparatus according to the present invention, the panel is charged (discharged) by applying a voltage at a constant cycle from the periphery of the panel. Therefore, when the finger is not touching the panel or when charging is completed even when the finger is touching, the charging (discharging) current does not flow. That is, since the position can be specified by charging once even if the finger is touched, the coordinates can be accurately determined in a short time. Furthermore, by controlling the circuit to operate only during the coordinate position detection period, it contributes to a reduction in power consumption as a whole. For example, when coordinate position detection is performed for a period of 0.2 ms with a period of 16.7 ms, the power consumption is always compared with when the circuit is operating by controlling the circuit to operate only during the coordinate position detection period. Thus, it is reduced to 0.2 / 16.7 times, that is, about 1/80 times.

  According to the coordinate position detection apparatus according to another aspect of the present invention, the coordinate position detection apparatus includes means for subtracting the noise signal received by the noise reception means from the output signal of the touch panel, so that noise including noise near the center frequency of the bandpass filter is included. It is possible to compensate for the effects.

  Examples of the present invention will be described below.

  A coordinate position detection apparatus according to an embodiment of the present invention recognizes a touched position as a coordinate in a panel when a human finger (or pen or the like) touches the panel in a capacitively coupled touch panel. In this case, the finger (or pen) is regarded as a capacitor (capacitor), and the coordinates are obtained by the current value (and its integrated value) when the capacitor is charged (discharged) through the resistance component of the panel.

  In this case, in this embodiment, the panel is charged (discharged) by applying a voltage from the periphery of the panel at a constant cycle. This operation is called an intermittent operation. Therefore, when the finger is not touching the panel or when charging is completed even when the finger is touching, the charging (discharging) current does not flow. That is, since the position can be specified by charging once even if the finger is touched, the coordinates can be accurately determined in a short time. Furthermore, current consumption (charging and discharging) flows only when necessary, which contributes to a reduction in power consumption as a whole.

  However, in this case, the difference in the current flowing through the finger contributes little to reducing the power consumption of the entire system. Here, what contributes to lower power consumption of the system is that pulses can be intermittently applied. That is, a feature of the present invention is that the current detection operation may be performed only when necessary (only when touching with a finger). In particular, in the conventional technique as shown in FIG. 7, since the circuit operation must be performed constantly (continuously), the current consumption increases in the entire system.

  In this embodiment, the means for converting the current into the voltage integrates the current when charging the capacitive load as a finger. The charging means switches the current flow.

  In this embodiment, a one-dimensional case will be described and described, but this can be easily extended to a two-dimensional case (actual case). In the case of one dimension, there are two sets of current integration means on the left and right, but in the case of two dimensions, this is four sets in four directions.

  FIG. 1 is a block diagram illustrating the configuration of the coordinate position detection apparatus according to the first embodiment of the present invention.

  The coordinate position detection apparatus according to the embodiment includes blocks 22 and 24 each including two means, that is, a means for charging the coupling capacity of the touch panel and a means for returning the charged coupling capacity to a state before charging. The blocks 27 and 28 comprise two means: means for converting the charged current into voltage and means for returning the converted voltage to the state before charging. The coordinate position detection apparatus further includes means 29 and 30 for sampling the converted voltage. The sampling means 29 and 30 are connected to the control device 31. 36 is a touch panel, 37 is a resistive film of the touch panel, and 38 is the impedance of a fingertip touched on the touch panel.

  In order to simplify the description, a one-dimensional resistance film 37 is shown here. In an actual display device, a resistive film having a two-dimensional extent exhibits the same function as this one-dimensional resistive film.

  With reference to FIG. 1, a voltage is periodically applied to touch panel 36 from around touch panel 36. That is, although a pulse is applied to the touch panel 36, when a finger (such as a pen) touches the touch panel 36, charging of the current starts to the finger. For example, the capacitance value of the finger is about 100 Pf, and the applied pulse voltage is about 1 μSec.

  When the touch panel 36 is touched with a finger (such as a pen), the coordinate position of the touch panel 36 is detected by causing a current to flow through the impedance 38. The voltages v01 and v02 at both ends of the resistance film 37 of the touch panel 36 are applied with in-phase voltages by the charging units 22 and 24, respectively, and are charged from v01 = v02 = v0 (v) to v01 = v02 = v0 + Vref (v). The At the time of charging, among the currents supplied from the charging means 22 and 24, one current i 1 flows from the touch position A to the impedance 38 through the resistor r 1 on the left side of the resistance film 37. The other current i <b> 2 flows from the touched position A to the impedance 38 via the resistor r <b> 2 on the right side of the resistive film 37. At this time, since the common-mode voltage is applied to the voltages v01 and v02 from the charging means 22 and 24, the common-mode voltage is also applied to the resistors r1 and r2, and the currents i1 and i2 are resistance values of the resistors r1 and r2, respectively. The value is inversely proportional to. Accordingly, the ratio of the currents i1 and i2 is expressed by the following equation.

  i1: i2 = r2: r1

  The currents i1 and i2 are inputted to the means 27 and 28 for converting into voltage via the means 22 and 24 for charging. When the voltages v01 and v02 are charged from v01 = v02 = V0 [V] to v01 = v02 = v0 + Vref [V], the charge amounts Q1 and Q2 of the currents i1 and i2 are converted into voltages 27 and 28, respectively. Are converted into voltages v11 and v12 and input to sampling means 29 and 30. At this time, since the ratio between the currents i1 and i2 is constant, the ratio between the charge amounts Q1 and Q2 is the same as the ratio between the currents i1 and i2, and the following equation is established.

  v11: v12 = Q1: Q2 = i1: i2 = r2: r1

  The sampling means 29 and 30 sample the voltages v11 and v12 and input the sampling output to the control device 31. Since the voltages v11 and v12 are values based on the ratio of the resistances r1 and r2 determined by the touched position of the panel, the control device 31 detects the coordinate position based on the input voltage ratio. Is possible.

  After sampling, the voltages v01 and v02 are discharged from v01 = v02 = v0 + Vref (v) to v01 = v02 = v0 (v) by means 22 and 24 for returning to the state before charging, and returned to the state before charging. . Further, after sampling, the voltages v11 and v12 are returned to the state before charging by means 27 and 28 for returning the converted voltage to the state before charging. This makes it possible to charge again and detect the coordinate position. By repeating the above operation, continuous coordinate position detection is possible.

  Note that “returning to the state before charging” is almost equivalent to “discharging”, but this expression was purposely used when charging from a state where the charge is completely zero, and at a certain level in the initial state. This is to include the case where charging is performed from above when there is a problem.

  Since this coordinate position detection device can detect the coordinate position by at least one charge, the detection time is shorter than that of the prior art shown in FIG. 7, and each circuit is turned off outside the detection period to operate intermittently. By doing so, power consumption can be reduced.

  Further, even if the charging means 22 and 24 shown in FIG. 1 are replaced with discharging means, only the polarity of the output of the means 27 and 28 for converting to voltage is inverted, so that the coordinate position can be detected.

  Next, FIG. 2 is a block diagram showing an embodiment of a coordinate position detecting apparatus provided with means for compensating for the current due to the parasitic capacitance of the touch panel among the currents flowing during charging when the touch panel has parasitic capacitance.

  FIG. 2 shows a configuration in which parasitic capacitances Ca and Cb of the touch panel and compensation means 21 and 23 are added to the coordinate position detection apparatus of FIG. When the charging means 22 and 24 charge the voltages v01 and v02 from v01 = v02 = v0 (v) to v01 = v02 = v0 + Vref (v), in addition to the currents i1 and i2, the parasitic capacitances Ca and Cb are supplied. Charging currents i3 and i4 flow. At this time, by outputting a current having the same magnitude as the currents i3 and i4 from the terminal C of the compensation means 21 and 23, the currents input to the means 27 and 28 for converting into voltages are only i1 and i2. It is possible to compensate for the influence due to the parasitic capacitances Ca and Cb of the touch panel.

  Next, an example of a circuit in the block of FIG. 2 is shown.

  FIG. 3 is an example of a circuit in each block of FIG. For the sake of simplicity, the circuits in one block (21, 22, 27, 29) are shown. Another block (23, 24, 28, 30) is a similar circuit.

  The charging means 22 includes a Pch MOS transistor PMOS1, an Nch MOS transistor NMOS1, and a voltage source v0 (v). PMOS 1 and NMOS 1 are ON / OFF controlled by signals from the control device. Before charging is started, PMOS1 is turned off, NMOS1 is turned on, and the voltage v01 becomes v0 (v). Thereafter, PMOS1 is turned on, NMOS1 is turned off, and the voltage v01 becomes the same potential as the terminal D of the means 27 for converting to voltage. At this time, since the terminal D of the means 27 for converting into voltage is set to v0 + Vref (v), the voltage v01 is charged to v0 + Vref (v). By charging the voltage v01, the current i1 is input to the means 27 for converting it into a voltage via the PMOS1. After the sampling by the sampling means 29 is completed, the PMOS 1 is turned off again and the NMOS 1 is turned on again, so that the charging can be started.

  The means 27 for converting voltage comprises PchMOS transistors PMOS2, PMOS3, NchMOS transistors NMOS2, NMOS3, a voltage source v0 + Vref (v), a capacitor C3, and an amplifier circuit OP1. PMOS 2, PMOS 3, NMOS 2, and NMOS 3 are ON / OFF controlled by signals from the control device.

  Before the charging by the charging means 22 is started, PMOS2, PMOS3, NMOS2, and NMOS3 are turned on, the terminal D of the means 27 for converting to voltage is v0 + Vref (v), and the voltage across the capacitor C1 is Set to 0 (v). Thereafter, PMOS2, PMOS3, NMOS2, and NMOS3 are turned off, and the terminal D of the means 27 for converting to voltage is held at v0 + Vref (v). When charging by the charging means 22 is started, the charge of the current i1 is charged in the capacitor C1, and the converted voltage v11 is output to the amplifier circuit OP1.

  After the voltage v11 is sampled by the sampling means 29, the PMOS2, PMOS3, NMOS2, and NMOS3 are turned on again, the voltages at both ends of C1 are set to 0 (v), and stand by in the state before charging. As the sampling means 29, a PchMOS transistor PMOS4, an NchMOS transistor NMOS4, and a capacitor C4 constitute a sample and hold circuit. The PMOS 4 and NMOS 4 are controlled to be turned on / off by a signal from the control device. At the time of sampling, PMOS4 and NMOS4 are ON, and at the time of holding, PMOS4 and NMOS4 are OFF.

  The means 21 for compensating for the parasitic capacitance component of the touch panel includes a Pch MOS transistor PMOS5, an NchMOS transistor NMOS5, a compensation capacitor C5, and a voltage source v0 + Vref × 2 (V). When PMOS1 of the charging means 22 is ON and NMOS1 is OFF, the voltage at one end of the parasitic capacitance Ca of the touch panel is v0 (v). At this time, the PMOS 5 of the compensation means 21 is ON and the NMOS 5 is OFF, and one end of the compensation capacitor C5 is charged to the voltage v0 + Vref × 2 (v).

  When PMOS 1 of the charging means 22 is OFF and NMOS 1 is ON, one end of the parasitic capacitance is charged to v0 + Vref (v). At this time, the PMOS 5 of the compensation means 21 is turned off, the NMOS 5 is turned on, and one end of the compensation capacitor C5 is discharged to v0 + Vref (v). At this time, the charging voltage of the parasitic capacitance Ca and the discharge voltage of the compensation capacitance are the same Vref (v). Therefore, by setting the parasitic capacitance Ca and the compensation capacitance C5 to the same capacitance value, The charge current and the discharge current of the compensation capacitor C5 from the source output of the NMOS 5 have the same amount of current, and the current due to the parasitic capacitance Ca is compensated.

  The circuit shown in FIG. 3 is realized by resistors, capacitors, and transistors, which are electronic components that can be integrated into an IC.

  The present embodiment corresponds to the invention according to claims 4 and 5.

  FIG. 4 is a block diagram of the configuration of the coordinate position detection apparatus according to the second embodiment. An antenna 12 that receives noise, a resistor r2 that converts a current change received from the antenna 12 into a voltage, a circuit 13 that detects a voltage across the resistor r2, and a subtraction circuit 14 are added to the conventional circuit shown in FIG. Has been. The antenna 12 is connected to one end of the resistor r2, and the opposite electrode of the resistor r2 is connected to GND. The electrodes at both ends of the resistor r2 are connected to the detection circuit 13. Four subtraction circuits 14 are connected between the current detection circuit 1 and the band pass filter 2. The + input and − input of the subtraction circuit 14 are connected to the output of the current detection circuit 1 and the output of the detection circuit 13, respectively. The output of the subtraction circuit 14 is connected to the input of the bandpass filter 2. The antenna 12 is disposed near the touch panel 11 so as to receive noise having the same phase as the external noise received by the touch panel 11.

  Next, the operation will be described. When external noise occurs, the external noise received by the touch panel 11 is output as Vnoise1 to the output of the current detection circuit 1 as in the conventional circuit. At this time, the antenna 12 also receives external noise, and the noise flows as a current change to the resistor r2, and a voltage is generated across the resistor r2. The resistor r2 is the same resistor as the resistor r1. The voltage across the resistor r2 is detected by the detection circuit 13 and output as Vnoise2. The detection circuit 13 is a circuit that enables the gain of the detection circuit 1 to be adjusted by an external input.

  The gain of the detected output signal Vnoise2 is adjusted by an external input so that the amplitude is the same as that of Vnoise1. Vnoise1 is input to the + input of the subtraction circuit 14, and Vnoise2 is input to the-input. Since gain adjustment is performed so that the amplitudes of Vnoise1 and Vnoise2 are the same, Vnoise1 and Vnoise2 are canceled at the output of the subtraction circuit 14, and no noise component is output from the output of the subtraction circuit 14. That is, there is no signal component due to external noise in the subsequent circuit after the bandpass filter 2.

  As described above, in the prior art, the noise component in the vicinity of the passband of the bandpass filter 2 passes without being removed. However, according to the present embodiment, the noise is deleted before the bandpass filter 12. Therefore, noise near the passband is no longer passed.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  As described above, according to the present invention, the detection time is shortened compared to the prior art, so that power consumption can be reduced and integration in an IC is possible, which is industrially useful.

1 is a block diagram illustrating a configuration example of a coordinate position detection apparatus according to Embodiment 1; 1 is a block diagram illustrating a configuration example of a coordinate position detection apparatus including a compensation circuit according to a first embodiment. The circuit diagram which shows one Example of this invention. FIG. 4 is a block diagram illustrating a configuration example of a coordinate position detection apparatus according to a second embodiment. The figure which shows the basic principle of the position detection method by a capacitive coupling system. The top view of a touch panel. The conceptual diagram of the coordinate position detection apparatus in the case of two dimensions. The block diagram of the conventional coordinate position detection apparatus. The block diagram of the coordinate position detection apparatus concerning another prior art example. The figure which shows the further problem of the conventional coordinate position detection apparatus.

Explanation of symbols

22, 24 Means for Charging the Capacitance of Touch Panel 27, 28 Means for Converting Voltage 29, 30 Means for Sampling Converted Voltage 31 Control Device 36 Touch Panel 37 Resistive Film of Touch Panel 38 Impedance of Fingertip Touched on Touch Panel

Claims (5)

In capacitive coupling type touch panel,
Means for charging the coupling capacity;
Means for converting the amount of charged charge into voltage;
Means for sampling the converted voltage;
Means for returning the charged coupling capacity to the state before charging;
Means for returning the converted voltage to the state before charging,
Each of the means is a coordinate position detecting device in which an intermittent operation is enabled. In capacitive coupling type touch panel,
Means for discharging the coupling capacity;
Means for converting the amount of discharged electric charge into voltage;
Means for sampling the converted voltage;
Means for returning the discharged coupling capacitance to the state before discharge;
Means for returning the converted voltage to the state before discharge,
Each of the means is a coordinate position detecting device in which an intermittent operation is enabled.   The coordinate position detection apparatus according to claim 1, further comprising means for compensating a current flowing to the parasitic capacitance of the touch panel among currents flowing during charging. In the coordinate position detection device of the capacitive coupling type touch panel that determines the contact position from the output signal of the touch panel,
Noise receiving means for receiving external noise;
A coordinate position detection apparatus comprising: means for subtracting a noise signal received by the noise receiving means from an output signal of the touch panel. The coordinate position detection apparatus according to claim 4, further comprising means for adjusting a gain of the noise signal.

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