JP7654883B1 - Integrated Circuit and Sensor Controller - Google Patents

Abstract

An integrated circuit capable of switching a connection method between a receiving coil of an EMR sensor and a sensor controller is provided.
[Solution] The integrated circuit according to the present invention includes a switch circuit 30 connected to a plurality of loop coils LCx which are receiving coils of an EMR sensor, the plurality of loop coils LCx having a plurality of ends including ends _T12 and _T21 along a first side of a touch surface, a differential amplifier _40-1 having a non-inverting input terminal and an inverting input terminal, and a group of switches which switch the connection destination of the end _T12 between the inverting input terminal of the differential amplifier _40-1 and either the end _T21 , the ground terminal, or the non-inverting input terminal of the differential amplifier _40-1 .
[Selected figure] Figure 2

Description

The present invention relates to an integrated circuit and a sensor controller, and more particularly to an integrated circuit and a sensor controller for use with an EMR sensor.

The electromagnetic induction method (EMR method) is known as one method for detecting the position of an electromagnetic induction pen on the panel surface of a tablet terminal or the like. A position detection device using the EMR method has a pen detection sensor (hereinafter referred to as the "EMR sensor") arranged on the panel surface and a sensor controller connected to the EMR sensor. The EMR sensor is composed of a transmitting coil consisting of multiple Tx coils arranged in a row in the y direction and a receiving coil consisting of multiple Rx coils arranged in a row in the x direction. The sensor controller detects the position of the electromagnetic induction pen (hereinafter referred to as the "pen position") by sequentially sending out alternating magnetic fields from the multiple Tx coils and receiving the reflected signal (hereinafter referred to as the "pen signal") sent by the electromagnetic induction pen at each Rx coil, and also receives the data sent by the electromagnetic induction pen (hereinafter referred to as the "pen data"). Patent documents 1 to 3 disclose examples of EMR sensors.

Patent Document 2 discloses an example of an EMR sensor that uses a loop coil as the Rx coil. Both ends of the Rx coil in Patent Document 2 are connected to two input terminals of a differential amplifier that outputs a pen signal. Patent Document 3 discloses an example of an EMR sensor that uses a linear electrode (hereinafter referred to as a "linear electrode") instead of the Rx coil.

Patent No. 6698386 JP 2018-185559 A JP 2022-117491 A

By the way, there are several methods for connecting each Rx coil that constitutes the receiving coil of an EMR sensor to the sensor controller. Specifically, there is the differential method, in which both ends of the Rx coil are connected to the sensor controller, the single-ended method, in which one end of the Rx coil is connected to the sensor controller and the other end is grounded, and the bundled input method, in which multiple Rx coils are connected in series to the sensor controller. Each method has its own advantages, but conventional position detection devices are limited to one of them. Therefore, there was a demand for the ability to switch the connection method between each Rx coil and the sensor controller.

Therefore, one object of the present invention is to provide an integrated circuit that can switch the connection method between the receiving coil of an EMR sensor and a sensor controller.

The inventor of the present application is also considering using a coil (hereinafter referred to as a "comb coil") configured by connecting a number of wires (hereinafter referred to as "comb teeth") extending in the y direction to one wire (hereinafter referred to as "base") extending in the x direction as the receiving coil of the EMR sensor, instead of the above-mentioned multiple Rx coils. One end of each comb tooth is connected to the base, and the other end is connected to the sensor controller. According to the research of the inventor of the present application, the sensor controller receives the pen signal by regarding the other ends of two adjacent comb teeth as both ends of the Rx coil, and thus can receive the pen signal as if the Rx coil were formed by the two comb teeth and the part of the base that connects them, even though each of the two comb teeth is actually connected to the other comb teeth via the base. Therefore, it is possible to detect the pen position by using a comb coil as well as by using multiple Rx coils.

However, comb coils have the problem that the accuracy of detecting the pen position is low. This is because the configuration of a comb coil is equivalent to a virtual loop coil made up of two adjacent comb teeth that are spaced apart in the x direction.

Therefore, another object of the present invention is to provide an integrated circuit that can improve the detection accuracy of the pen position when a comb coil is used as the receiving coil of an EMR sensor.

In addition, while an alternating magnetic field is being emitted from the Tx coil, this alternating magnetic field appears in the Rx coil, so the sensor controller receives the pen signal at the Rx coil after stopping the emission of the alternating magnetic field from the Tx coil. However, due to the influence of the time constant of the Rx coil, the influence remains in the Rx coil even after the emission of the alternating magnetic field from the Tx coil has stopped, deteriorating the SNR (Signal to Noise Ratio) of the pen signal.

Therefore, another object of the present invention is to provide an integrated circuit and a sensor controller that can improve the SNR of the pen signal.

The inventor of the present application is also considering using a coil (hereinafter referred to as a "comb coil") configured by connecting a number of wires (hereinafter referred to as "comb teeth") extending in the y direction to one wire (hereinafter referred to as "base") extending in the x direction as the receiving coil of the EMR sensor, instead of the above-mentioned multiple Rx coils. One end of each comb tooth is connected to the base, and the other end is connected to the sensor controller. According to the research of the inventor of the present application, the sensor controller receives the pen signal by regarding the other ends of two adjacent comb teeth as both ends of the Rx coil, and thus can receive the pen signal as if the Rx coil were formed by the two comb teeth and the part of the base that connects them, even though each of the two comb teeth is actually connected to the other comb teeth via the base. Therefore, it is possible to detect the pen position by using a comb coil as well as by using multiple Rx coils.

However, comb coils have the problem that the accuracy of detecting the pen position is low. This is because the configuration of a comb coil is equivalent to a virtual loop coil made up of two adjacent comb teeth that are spaced apart in the x direction.

Therefore, another object of the present invention is to provide an integrated circuit and a sensor controller that can improve the detection accuracy of the pen position when a comb coil is used as the receiving coil of an EMR sensor.

In addition, when using a linear electrode instead of an Rx coil as in Patent Document 2, the sign of the pen signal is opposite between the linear electrode on one side of the pen position in the x direction and the linear electrode on the other side of the x direction, and a sign transition occurs near the pen position, resulting in a problem that the received strength of the pen signal is weak near the pen position.

Therefore, another object of the present invention is to provide an integrated circuit and a sensor controller that can increase the reception strength of a pen signal when a linear electrode is used instead of an Rx coil.

Furthermore, in conventional position detection devices, if the electromagnetic induction pen is tilted relative to the panel surface, the peak position of the pen signal received by the Rx coil may shift from the actual position of the pen tip depending on the azimuth angle of the electromagnetic induction pen. This causes a deterioration in the detection accuracy of the pen position, so improvements were needed.

Therefore, another object of the present invention is to provide a sensor controller that can detect the position of an electromagnetic induction pen with high accuracy even if the pen is tilted relative to the panel surface.

Furthermore, in recent years, displays that can be folded (foldable displays) have appeared, and there is a demand for these foldable displays to be able to detect the position of an electromagnetic induction pen. However, foldable displays use conductive hinge parts to achieve folding, and because these hinge parts disrupt the magnetic field, there is a problem in that the reception strength of the pen signal is weakened near the hinge parts, i.e., near the folding line.

Therefore, another object of the present invention is to provide an integrated circuit and a sensor controller that can increase the reception strength of a pen signal near the folding line of a foldable display.

The integrated circuit according to the first aspect of the present invention is an integrated circuit connected to a receiving coil of an EMR sensor, the receiving coil having a plurality of ends along a first side of a touch surface, the plurality of ends including a first end and a second end, a differential amplifier having a first input terminal and a second input terminal, and a group of switches for switching the connection destination of the first end between the second input terminal and any one of the second end, a ground terminal, and the first input terminal.

The integrated circuit according to the second aspect of the present invention is an integrated circuit according to the first aspect, in which the receiving coil is a comb coil having the multiple ends, and the group of switches switches in a time-division manner between a first state in which the first end is connected to the second input terminal, and a second state in which the first end is connected to the first input terminal.

The integrated circuit according to the third aspect of the present invention is an integrated circuit connected to an EMR sensor, the receiving coil of the EMR sensor being composed of a plurality of first loop coils, the integrated circuit including a plurality of differential amplifiers each having a first input terminal and a second input terminal, a first wiring that connects one end of each of the plurality of first loop coils to the first input terminal of the corresponding differential amplifier, a second wiring that connects the other end of each of the plurality of first loop coils to the second input terminal of the corresponding differential amplifier, and a first switch element provided between a power supply wiring to which a predetermined power supply potential is supplied and the first wiring.

A sensor controller according to a third aspect of the present invention is a sensor controller connected to the EMR sensor via an integrated circuit according to the first aspect of the present invention, in which the plurality of first loop coils each extend in a first direction and are arranged side by side in a second direction intersecting the first direction, and a transmitting coil of the EMR sensor is composed of a plurality of second loop coils each extending in a second direction and arranged side by side in the first direction, and the integrated circuit has a first state in which one end and the other end of the 2n-1th (n is a natural number) first loop coil from one end side in the second direction of the plurality of first loop coils are connected to the first input terminal and the second input terminal of the corresponding differential amplifier, while one end and the other end of the 2nth first loop coil are disconnected from the first input terminal and the second input terminal of the corresponding differential amplifier, and a second state in which the 2nth first loop coil from one end side in the second direction of the plurality of first loop coils is disconnected from the first input terminal and the second input terminal of the corresponding differential amplifier. A switch circuit is configured to be able to switch between a first state in which one end and the other end of the first loop coil are connected to the first input terminal and the second input terminal of the corresponding differential amplifier, and a second state in which one end and the other end of the 2n-1th first loop coil are disconnected from the first input terminal and the second input terminal of the corresponding differential amplifier, and an alternating magnetic field is sent from the EMR sensor by sequentially passing a current through each of the plurality of second loop coils, and the switch circuit is set to the first state when the current is passed through the second loop coil that is 2m-1th (m is a natural number) from one end side in the first direction among the plurality of second loop coils, and the switch circuit is set to the second state when the current is passed through the loop coil that is 2mth from one end side in the first direction among the plurality of loop coils, thereby receiving a pen signal output from each of the plurality of differential amplifiers.

The integrated circuit according to the fourth aspect of the present invention is an integrated circuit connected to an EMR sensor, and the receiving coil of the EMR sensor is a comb coil having a configuration in which a plurality of comb teeth each extending in a first direction are connected at one end to a base extending in a second direction intersecting the first direction, and includes a plurality of differential amplifiers each having a first input terminal and a second input terminal, and a switch circuit configured to be able to switch between a first state in which the other end of the 2n-1th (n is a natural number) comb tooth portion from one end side in the second direction and the other end of the 2nth comb tooth portion from one end side in the second direction are connected to the first input terminal and the second input terminal of the same differential amplifier, and a second state in which the other end of the 2nth comb tooth portion from one end side in the second direction and the other end of the 2n+1th comb tooth portion from one end side in the second direction are connected to the first input terminal and the second input terminal of the same differential amplifier.

The sensor controller according to the fourth aspect of the present invention is a sensor controller connected to the EMR sensor via the integrated circuit according to the second aspect of the present invention, and the transmitter coil of the EMR sensor is composed of a plurality of loop coils each extending in the second direction and arranged in the first direction, and an alternating magnetic field is sent from the EMR sensor by sequentially passing a current through each of the plurality of loop coils, and when passing the current through the loop coil that is 2m-1th (m is a natural number) from one end side in the first direction among the plurality of loop coils, the switch circuit is set to the first state, and when passing the current through the loop coil that is 2mth from one end side in the first direction among the plurality of loop coils, the switch circuit is set to the second state, thereby receiving a pen signal output from each of the plurality of differential amplifiers.

The integrated circuit according to the fifth aspect of the present invention is an integrated circuit connected to an EMR sensor, the receiving coil of the EMR sensor being composed of a plurality of linear electrodes each extending in a first direction and arranged in a second direction intersecting the first direction, the integrated circuit including a plurality of differential amplifiers each having a first input terminal and a second input terminal, and wiring connecting an end of the 2n-kth (k is an odd natural number, n is a natural number greater than k/2) linear electrode from one end side in the second direction among the plurality of linear electrodes to the first input terminal and the second input terminal of the same differential amplifier, respectively.

The sensor controller according to the fifth aspect of the present invention is a sensor controller connected to the EMR sensor via the integrated circuit according to the third aspect of the present invention, and the transmitter coil of the EMR sensor is composed of a plurality of loop coils each extending in the second direction and arranged in the first direction, and an alternating magnetic field is sent from the EMR sensor by sequentially passing a current through each of the plurality of loop coils, and when passing the current through the loop coil that is 2m-1th (m is a natural number) from one end side in the first direction among the plurality of loop coils, the switch circuit is set to the first state, and when passing the current through the loop coil that is 2mth from one end side in the first direction among the plurality of loop coils, the switch circuit is set to the second state, thereby receiving the pen signal output from each of the plurality of differential amplifiers.

A sensor controller according to a sixth aspect of the present invention is a sensor controller connected to an EMR sensor having a plurality of loop coils, which adds, with different weighting, a pen signal received at a first loop coil among the plurality of loop coils and a pen signal received at one or more other loop coils that are located near the first loop coil among the plurality of loop coils, and derives the position of the electromagnetic induction pen using an added pen signal obtained by the addition.

An integrated circuit according to a seventh aspect of the present invention is an integrated circuit connected to an EMR sensor, the receiving coil of the EMR sensor being a comb coil having a configuration in which a plurality of comb tooth portions each extending in a first direction are connected at one end to a base portion extending in a second direction intersecting the first direction, the receiving coil including a receiving circuit for a pen signal transmitted by an electromagnetic induction pen, and a selection circuit for selecting two of the plurality of comb tooth portions and connecting the selected two comb tooth portions to the receiving circuit, the plurality of comb tooth portions being connected to a base portion extending in the second direction. The integrated circuit has first to fourth comb tooth portions in order from one side, and the selection circuit performs the selection so that a first state in which the first and third comb tooth portions are selected from the plurality of comb tooth portions and a second state in which the second and fourth comb tooth portions are selected from the plurality of comb tooth portions appear in order, and the distance between the first comb tooth portion and the third comb tooth portion and the distance between the second comb tooth portion and the fourth comb tooth portion are both a first distance, and the distance between the first comb tooth portion and the second comb tooth portion is a second distance shorter than the first distance.

The sensor controller according to the seventh aspect of the present invention is an integrated circuit according to the seventh aspect of the present invention, further comprising: the plurality of comb tooth portions having a fifth comb tooth portion on the other side of the fourth comb tooth portion in the second direction; the selection circuit is a sensor controller connected to the EMR sensor via an integrated circuit that performs the selection so that the first state, the second state, and a third state that selects the third comb tooth portion and the fifth comb tooth portion appear in sequence; and the sensor controller controls the selection circuit so that the first state, the second state, and the third state appear in sequence.

According to the first aspect of the present invention, it is possible to switch the connection method between the receiving coil of the EMR sensor and the sensor controller by controlling a group of switches.

According to the second aspect of the present invention, the reception of the pen signal in the first state and the reception of the pen signal in the second state can be executed in a time-division manner, and therefore the spacing between the virtual loop coils can be effectively set to zero, thereby improving the detection accuracy of the pen position when a comb coil is used as the receiving coil of the EMR sensor.

According to the third aspect of the present invention, each first loop coil can be precharged by turning on the first switch element, so that the influence of the alternating magnetic field emitted from the transmitting coil can be eliminated from the receiving coil, thereby improving the SNR of the pen signal.

According to the fourth aspect of the present invention, the reception of the pen signal in the first state and the reception of the pen signal in the second state can be executed in a time-division manner, and therefore the spacing between the virtual loop coils can be effectively set to zero, thereby improving the detection accuracy of the pen position when a comb coil is used as the receiving coil of the EMR sensor.

According to the fifth aspect of the present invention, pen signals having opposite signs are reinforced by a differential amplifier, making it possible to increase the received strength of the pen signal in the vicinity of the pen position when a linear electrode is used as an Rx coil.

According to the sixth aspect of the present invention, the position of the electromagnetic induction pen is derived using an added pen signal obtained by adding pen signals received by multiple loop coils with different weighting, so that even if the electromagnetic induction pen is tilted relative to the panel surface, its position can be detected with high accuracy.

According to the seventh aspect of the present invention, the virtual loop coil is shifted by a distance shorter than the distance between the two comb teeth that make up the virtual loop coil, making it possible to increase the reception strength of the pen signal near the folding line of the foldable display.

1 is a diagram showing a configuration of a position detection system 1 according to a first embodiment of the present invention. 2 is a diagram showing an internal configuration of a switch circuit 30 shown in FIG. 1 and a state of the switch circuit 30 in a differential system. 2 is a diagram showing an internal configuration of a switch circuit 30 shown in FIG. 1 and a state of the switch circuit 30 in a single-ended system. 2 is a diagram showing an internal configuration of a switch circuit 30 shown in FIG. 1 and a first state of the switch circuit 30 in a bundled input method. 2 is a diagram showing an internal configuration of the switch circuit 30 shown in FIG. 1 and a second state of the switch circuit 30 in the bundled input method. FIG. 11 is a diagram showing a configuration of a position detection system 1 according to a second embodiment of the present invention. 7 is a diagram showing an internal configuration and a first state of the switch circuit 30 shown in FIG. 6. 7 is a diagram showing an internal configuration and a second state of the switch circuit 30 shown in FIG. 6. FIG. 13 is a diagram illustrating a first state of a switch circuit 30 according to a first modified example of the second embodiment of the present invention. FIG. 13 is a diagram illustrating a second state of the switch circuit 30 according to the first modified example of the second embodiment of the present invention. FIG. 13 is a diagram illustrating a first state of a switch circuit 30 according to a second modified example of the second embodiment of the present invention. FIG. 13 is a diagram illustrating a second state of the switch circuit 30 according to the second modified example of the second embodiment of the present invention. FIG. 11 is a diagram showing an internal configuration of a switch circuit 30 according to a third embodiment of the present invention. 14 is a diagram showing waveforms of signals related to the control of switch elements S1, S2, T1, and T2 shown in FIG. 13. 13A to 13C are diagrams illustrating a method of driving an EMR sensor according to a modified example of the third embodiment of the present invention. FIG. 13 is a diagram showing a configuration of a position detection system 1 according to a fourth embodiment of the present invention. 17 is a diagram showing an internal configuration and a first state of the switch circuit 30 shown in FIG. 16. 17 is a diagram showing an internal configuration and a second state of the switch circuit 30 shown in FIG. 16. 13A to 13C are diagrams illustrating a method of driving an EMR sensor according to a modified example of the fourth embodiment of the present invention. FIG. 13 is a diagram showing a configuration of a position detection system 1 according to a fifth embodiment of the present invention. 21 is a diagram showing an internal configuration and a first state of the switch circuit 30 shown in FIG. 20. 21 is a diagram showing an internal configuration and a second state of the switch circuit 30 shown in FIG. 20. FIG. 13 is a diagram showing a simulation result of the reception strength of a pen signal. FIG. 23 is a diagram showing an internal configuration and a first state of a switch circuit 30 included in a position detection system 1 according to a first modified example of the fifth embodiment of the present invention. FIG. 23 is a diagram showing an internal configuration and a second state of a switch circuit 30 included in a position detection system 1 according to a first modified example of the fifth embodiment of the present invention. 13A to 13C are diagrams illustrating a method of driving an EMR sensor according to a second modified example of the fifth embodiment of the present invention. 13A to 13C are diagrams illustrating problems that arise when receiving a pen signal using the position detection system 1 according to the third embodiment of the present invention. 28 is a diagram for explaining the azimuth angle θ and tilt angle φ used in FIG. 27. 13A is a diagram for explaining the processing performed by a sensor controller 31 according to a sixth embodiment of the present invention, and FIG. 13B is a diagram showing a virtual loop coil VLCx obtained by the addition shown in FIG. 11 is a diagram showing the reception level of the sum pen signal PS _SUM when the tip of the electromagnetic induction pen 2 is at the position of x coordinate=0 mm. FIG. 13A is a plan view of an EMR sensor 33 included in a position detection device 3 according to a seventh embodiment of the present invention, and FIG. 13B is a cross-sectional view of the EMR sensor 33 corresponding to the line AA shown in FIG. 13A. 13A is a diagram illustrating the distribution of reception levels of the pen signal PS received when the tip of the electromagnetic induction pen 2 is at each position in the x direction, assuming that the ODD/EVEN method is adopted in the position detection device 3 according to the seventh embodiment of the present invention, and FIG. 13B is a diagram illustrating the distribution of reception levels of the pen signal PS received when the tip of the electromagnetic induction pen 2 is at each position in the x direction, assuming that the ODD/EVEN method is adopted in the position detection device 3 according to the seventh embodiment of the present invention (i.e., a position detection device 3 adopting the A/B/C method). FIG. 13 is a diagram showing an internal configuration and a first state of a switch circuit 30 according to a seventh embodiment of the present invention. FIG. 13 is a diagram showing an internal configuration and a second state of a switch circuit 30 according to a seventh embodiment of the present invention. FIG. 13 is a diagram showing an internal configuration and a third state of a switch circuit 30 according to a seventh embodiment of the present invention. This figure plots the maximum reception level of the pen signal PS observed when the ODD/EVEN method is adopted and the maximum reception level of the pen signal PS observed when the A/B/C method is adopted, for each distance (pen height) from the touch surface 3a to the tip of the electromagnetic induction pen 2. FIG. 23 is a diagram illustrating a process performed by a sensor controller 31 according to a modified example of the seventh embodiment of the present invention.

The following describes in detail an embodiment of the present invention with reference to the attached drawings.

Figure 1 is a diagram showing the configuration of a position detection system 1 according to a first embodiment of the present invention. As shown in the figure, the position detection system 1 is configured to have an electromagnetic induction pen 2 and a position detection device 3. Of these, the electromagnetic induction pen 2 is a pen that supports position detection using the EMR method, and is configured to have a resonant circuit including a coil and a capacitor inside.

The position detection device 3 is a device configured to be able to detect the position of the electromagnetic induction pen 2 within the touch surface 3a (panel surface) using the EMR method. Within the touch surface 3a, multiple loop coils LCx (Rx coils) which are the receiving coils of the EMR sensor, and multiple loop coils LCy (Tx coils) which are the transmitting coils of the EMR sensor are arranged. In addition to these, the position detection device 3 is configured to include a switch circuit 30, a sensor controller 31, and a host processor 32. A typical example of the position detection device 3 is a tablet terminal or notebook computer whose display surface doubles as the touch surface 3a, but the position detection device 3 may also be configured using a digitizer that does not have a display surface.

The illustrated x and y directions are directions within the touch surface 3a and are mutually perpendicular. The multiple loop coils LCx are each formed to extend in the y direction and are arranged side by side in the x direction. On the other hand, the multiple loop coils LCy are each formed to extend in the x direction and are arranged side by side in the y direction. Note that both loop coils LCx and LCy may be arranged to overlap with other adjacent loop coils LCx and LCy, in which case they are formed three-dimensionally using via conductors or the like. Both ends of each loop coil LCx and each loop coil LCy are connected to the switch circuit 30. The end of each loop coil LCx is arranged along side E1, which is one side of the rectangular touch surface 3a.

The switch circuit 30 is a group of switches (switch group) that is configured with a plurality of switches for switching the connections between the plurality of loop coils LCx and between the plurality of loop coils LCx and the sensor controller 31. The switch circuit 30 may be configured as an integrated circuit by itself, or may be provided in the same integrated circuit as the sensor controller 31. The switching state of the switch circuit 30 is controlled by the sensor controller 31.

The sensor controller 31 is an integrated circuit that has the function of detecting the position (pen position) of the electromagnetic induction pen 2 on the touch surface 3a by the EMR method. The sensor controller 31 controls the connection state of the loop coils LCx, LCy by controlling the switch circuit 30, thereby supplying AC current to each of the multiple loop coils LCy in sequence, and each time, performs processing to receive a pen signal generated in each loop coil LCx. The sensor controller 31 is then configured to derive the pen position based on the pen signal thus received, and to receive pen data transmitted by the electromagnetic induction pen 2.

To explain in more detail, when the sensor controller 31 starts supplying AC current to one of the loop coils LCy, that loop coil LCy starts emitting an AC magnetic field. When the coil of the electromagnetic induction pen 2 enters this AC magnetic field, an electromotive force is generated at both ends, charging the capacitor of the electromagnetic induction pen 2. When the sensor controller 31 then stops supplying AC current to the loop coil LCy, the power stored in the capacitor of the electromagnetic induction pen 2 causes the coil of the electromagnetic induction pen 2 to emit an AC magnetic field (pen signal).

The electromagnetic induction pen 2 is configured to be able to transmit pen data, such as a pen pressure value indicating the pressure applied to the pen tip and on/off information indicating the on/off state of a switch provided on the surface, using a pen signal. That is, the capacitor that constitutes the resonant circuit of the electromagnetic induction pen 2 is configured so that its capacitance changes according to the value of the pen data. When the capacitance of the capacitor changes, the resonant frequency of the resonant circuit changes according to the amount of change, and therefore the frequency of the alternating magnetic field emitted from the coil changes according to the value of the pen data. The electromagnetic induction pen 2 is configured to utilize the properties of this resonant circuit to frequency-modulate the alternating magnetic field emitted from the coil using the pen data.

The pen signal sent from the coil of the electromagnetic induction pen 2 is received by each loop coil LCx. The sensor controller 31 changes the loop coil LCy that supplies AC current under the control of the switch circuit 30, and receives the pen signal at each loop coil LCx each time, thereby acquiring the strength of the pen signal for each combination of loop coil LCy and loop coil LCx. Then, based on each acquired strength, the intensity distribution of the pen signal within the touch surface 3a is derived, and the apex of the distribution is detected as the pen position. The sensor controller 31 also acquires pen data by detecting changes in the frequency of the pen signal received with the strongest strength. The sensor controller 31 is configured to supply the position detected as described above and the acquired data to the host processor 32 each time.

Here, the detection of the pen position by the sensor controller 31 is performed in one of two modes: global scan and local scan. Global scan is a process that is performed when the pen position has not yet been detected, and the sensor controller 31 executes the above-mentioned series of processes using all loop coils LCx, LCy. This enables the sensor controller 31 to detect the electromagnetic induction pen 2 over the entire touch surface 3a.

On the other hand, local scan is a process that is executed when a pen position has already been detected. In this case, the sensor controller 31 executes the above-mentioned series of processes using only the loop coils LCx and LCy that are located near the previously detected pen position. This reduces the time required for one position detection, allowing the sensor controller 31 to detect the pen position more frequently than with global scan.

The sensor controller 31 is configured to select one of the above-mentioned differential, single-end, and bundled input methods for receiving the pen signal in each loop coil LCx. This selection may be performed during the manufacturing stage of the sensor controller 31 or the position detection device 3, or may be performed when the user uses the device. In one example, the sensor controller 31 may select the bundled input method when the pen pressure value included in the latest received pen data indicates that the electromagnetic induction pen 2 is hovering (the pen tip is not in contact with the touch surface 3a), and may select the differential or single-end method when the pen is touching (the pen tip is in contact with the touch surface 3a). The sensor controller 31 controls the switch circuit 30 according to the result of the selection, and as a result, the reception of the pen signal in the selected method is realized. The specific contents of the control of the switch circuit 30 by the sensor controller 31 will be described in detail later with reference to Figures 2 to 5.

The host processor 32 is a central processing unit of the position detection device 3 that executes the operating system and various applications of the position detection device 3 by executing programs read from a memory (not shown). The processes executed by the host processor 32 according to the programs include various processes using the pen position and pen data supplied from the sensor controller 31. These various processes include, for example, the movement of the cursor displayed on the display surface and the generation of stroke data indicating the trajectory of the electromagnetic induction pen 2 on the touch surface. With regard to the stroke data, the host processor 32 also performs processes such as rendering and displaying the generated stroke data, generating and recording digital ink including the generated stroke data, and transmitting the generated digital ink to an external device in response to a user instruction.

Figures 2 to 5 are diagrams showing the internal configuration of the switch circuit 30. These figures show only the parts of the internal configuration of the switch circuit 30 that are related to receiving the pen signal in each loop coil LCx. Below, with reference to these figures, we will explain in detail the internal configuration of the switch circuit 30 and the specific content of the control of the switch circuit 30 performed by the sensor controller 31 to realize each of the differential method, single-ended method, and bundled input method.

2 to 5 show only two loop coils _LCx1 and _LCx2 , but the actual position detection device 3 naturally has many more loop coils LCx. Hereinafter, both ends of the loop coil _LCx1 will be referred to as ends _T11 and _T12 , and both ends of the loop coil _LCx2 will be referred to as ends _T21 and _T22 .

2, the switch circuit 30 includes a plurality of differential amplifiers 40 and a switch group including a plurality of switches 50 to 55. The differential amplifier 40 is provided for each loop coil LCx. The switches 50, 51, and 52 are single-pole double-throw switches, and the switches 53 and 54 are single-pole triple-throw switches, each of which is provided for each loop coil LCx. The switch 55 is a single-pole double-throw switch, and is provided for each pair of adjacent loop coils LCx. In the following description, as necessary, the configuration corresponding to the loop coil LCx ₁ may be distinguished from the other configurations by adding a subscript "1" to the right of the reference numeral, the configuration corresponding to the loop coil LCx ₂ may be distinguished from the other configurations by adding a subscript "2" to the right of the reference numeral, and the configuration corresponding to both the loop coils LCx ₁ and LCx ₂ may be distinguished from the other configurations by adding a subscript "1" to the right of the reference numeral.

Each differential amplifier 40 is an amplifier circuit (differential amplifier) that has a non-inverting input terminal, an inverting input terminal, and an output terminal, amplifies the potential difference between the non-inverting input terminal and the inverting input terminal, and outputs the amplified potential difference from the output terminal as an output voltage relative to the ground potential. The output terminal of each differential amplifier 40 is supplied to the sensor controller 31 as a pen signal.

The common terminal of the switch _50-1 is connected to the end T- ₁₁ , one selection terminal is connected to the ground terminal, and the other selection terminal constitutes the node n- ₁₁ shown in the figure. The common terminal of the switch _51-1 is connected to the end T- ₁₂ , one selection terminal is connected to the ground terminal, and the other selection terminal constitutes the node n- ₁₂ shown in the figure. The common terminal of the switch _52-1 is connected to the node n _-12 , one selection terminal is connected to the node n _-11 , and the other selection terminal is connected to the second selection terminal of the switch _53-1 . The common terminal of the switch _53-1 is connected to the non-inverting input terminal of the differential amplifier _40-1 , the first selection terminal is connected to the node n- ₁₁ , and the third selection terminal is connected to the ground terminal. The common terminal of the switch _54-1 is connected to the inverting input terminal of the differential amplifier _40-1 , the first selection terminal is connected to the node n- ₁₂ , the second selection terminal is connected to a node n _-21 described later, and the third selection terminal is connected to the ground terminal.

The common terminal of the switch ₅₀₂ is connected to the end _T21 , one selection terminal is connected to the ground terminal, and the other selection terminal constitutes the node _n21 shown in the figure. The common terminal of the switch ₅₁₂ is connected to the end _T22 , one selection terminal is connected to the ground terminal, and the other selection terminal constitutes the node _n22 shown in the figure. The common terminal of the switch ₅₂₂ is connected to the node _n22 , one selection terminal is connected to the node _n21 , and the other selection terminal is connected to the second selection terminal of the switch _532. The common terminal of the switch ₅₃₂ is connected to the non-inverting input terminal of the differential amplifier ₄₀₂ , the first selection terminal is connected to the node _n21 , and the third selection terminal is connected to the ground terminal. The common terminal of the switch ₅₄₂ is connected to the inverting input terminal of the differential amplifier ₄₀₂ , the first selection terminal is connected to the node _n22 , and the third selection terminal is connected to the ground terminal. Although not shown, a second selection terminal of the switch ₅₄₂ is connected to the other selection terminal of the switch 50 corresponding to another loop coil LCx adjacent to the loop coil _LCx2 on the opposite side to the loop coil _LCx1 .

The common terminal of switch 55 is connected to terminal _T12 and one select terminal is connected to terminal _T21 . The other select terminal of switch 55 is not connected anywhere, and therefore switch 55 may be a single-pole, single-throw switch.

With the above configuration, the switch circuit 30 plays a role of switching the connection destination of the end _T12 (first end) between the inverting input terminal (second input terminal) of the differential amplifier ₄₀₁ and either the end _T21 (second end), the ground terminal, or the non-inverting input terminal (first input terminal) of the differential amplifier _401. The sensor controller 31 controls this switching to realize reception of pen signals by each of the differential method, the single-ended method, and the bundled input method. This will be described in detail below.

2 shows the state of the switch circuit 30 after being controlled by the sensor controller 31 that has selected the differential method. In this case, the sensor controller 31 connects the other selection terminal of each of the switches 50 and 51 to the common terminal, and connects the first selection terminal of each of the switches 53 and 54 to the common terminal. The switches 52 and 55 are in a disconnected state (or in a state in which the other selection terminal of each is selected). As a result, as shown by the dashed lines in FIG. 2, both ends of the corresponding loop coil LCx are connected to each differential amplifier 40. For example, the non-inverting input terminal of the differential amplifier _40-1 is connected to the end _T11 of the loop coil LCx _-1 , and the inverting input terminal is connected to the end _T12 of the loop coil LCx- ₁ . According to the differential method, it is possible to remove common mode noise from the pen signal received by each loop coil LCx, and it is also possible to obtain the effect that the signal strength of the pen signal received by each loop coil LCx is greater than that of the single-ended method described later.

3 shows the state of the switch circuit 30 after being controlled by the sensor controller 31 that has selected the single-ended method. In this case, the sensor controller 31 connects the other selection terminal of the switch 50 to the common terminal, connects the first selection terminal of the switch 53 to the common terminal, connects one selection terminal of the switch 51 to the common terminal, and connects the third selection terminal of the switch 54 to the common terminal. The switches 52 and 55 are in a disconnected state (or in a state in which the other selection terminal is selected) as in the case of FIG. 2. As a result, as shown by the dashed lines in FIG. 3, in each differential amplifier 40, only the non-inverting input terminal is connected to one end of the corresponding loop coil LCx, and the inverting input terminal is connected to the ground terminal. In addition, the other end of each loop coil LCx is connected to the ground terminal. For example, the non-inverting input terminal of the differential amplifier _40-1 is connected to the end _{T11 of} the loop coil LCx _-1 , the inverting input terminal is connected to the ground terminal, and the end _T12 of the loop coil LCx-1 is connected to the ground terminal. The single-ended method has the effect of enabling the sensor controller 31 to receive the pen signal even if the differential amplifier 40 is not connected to both ends of the loop coil LCx.

Figures 4 and 5 show the state of the switch circuit 30 after being controlled by the sensor controller 31 that has selected the bundled input method. In this case, the sensor controller 31 controls the switch circuit 30 so that the first state shown in Figure 4 and the second state shown in Figure 5 are realized in a time-division manner for each loop coil LCy.

First, referring to Fig. 4, the first state is a state in which two adjacent loop coils LCx are connected in series between the non-inverting input terminal and the inverting input terminal of each differential amplifier 40. To be more specific with reference to Fig. 4, in order to realize the first state, the sensor controller 31 connects the other selection terminal of the switches ₅₀₁ and ₅₁₂ to the common terminal, connects one selection terminal of the switches ₅₂₂ and ₅₅₁₂ to the common terminal, connects the first selection terminal of the switch ₅₃₁ to the common terminal, connects the second selection terminal of the switch ₅₄₁ to the common terminal, and disconnects the switches ₅₀₂ , ₅₁₁ , ₅₂₁ , ₅₃₂ , and _542. As a result, as shown by the dashed lines in Fig. 4, the two loop coils _LCx1 and _LCx2 are connected in series between the non-inverting input terminal and the inverting input terminal of the differential amplifier _401. The same applies to the other loop coils LCx not shown.

Referring next to FIG. 5, in the second state, the combination of two loop coils LCx connected in series to each differential amplifier 40 is shifted by one in the x direction compared to the first state. In addition to this shift, the contents of the control of the switch circuit 30 performed by the sensor controller 31 to realize the second state are the same as those in the first state.

According to the bundled input method, since two loop coils LCx are connected in series, the inductance is doubled, and the reception strength of the pen signal is increased accordingly. However, since the first state shown in FIG. 4 and the second state shown in FIG. 5 must be performed in a time-division manner, it takes twice as long to receive the pen signal as in the differential or single-end methods. As described above, the sensor controller 31 selects the bundled input method when the pen pressure value included in the most recently received pen data indicates that the electromagnetic induction pen 2 is hovering, and selects the differential or single-end method when the pen is touching. In this way, during hovering, when the distance between the coil in the electromagnetic induction pen 2 and the touch surface 3a is large and the reception strength of the pen signal tends to be small, the bundled input method is used to increase the reception strength of the pen signal, and during pen touch, when a sufficiently large reception strength is obtained, the differential or single-end method is used to shorten the time required to receive the pen signal. In this way, adaptive switching of the connection method can be realized.

As described above, according to the position detection system 1 of this embodiment, by controlling the group of switches in the switch circuit 30 from the sensor controller 31, it is possible to switch the connection method between the receiving coil of the EMR sensor and the sensor controller 31 between the differential method, the single-ended method, and the bundled input method. Therefore, the sensor controller 31 can detect the pen position and acquire pen data while making the most of the advantages of each method.

Figure 6 is a diagram showing the configuration of a position detection system 1 according to a second embodiment of the present invention. The position detection system 1 according to this embodiment differs from the position detection system 1 according to the first embodiment in that it uses a comb coil CCx consisting of a base portion PB and multiple comb teeth portions PT as the receiving coil of the EMR sensor, rather than multiple loop coils LCx. In addition, the internal configuration of the switch circuit 30 and the content of the control of the switch circuit 30 by the sensor controller 31 are also different from those of the position detection system 1 according to the first embodiment. In other respects, it is similar to the position detection system 1 according to the first embodiment, so the following description will focus on the differences from the position detection system 1 according to the first embodiment.

As shown in FIG. 6, the comb coil CCx is configured by connecting a base PB, which is a single wire extending in the x direction, to a number of comb tooth portions PT, which are wires extending in the y direction. One end of each comb tooth portion PT is connected to the base PB, and the other end is connected to the switch circuit 30. The other end of each comb tooth portion PT is arranged along side E1, which is one side of the rectangular touch surface 3a.

Figures 7 and 8 are diagrams showing the internal configuration of the switch circuit 30 according to this embodiment. These figures show only the parts of the internal configuration of the switch circuit 30 that are related to receiving a pen signal in the comb coil CCx. Below, with reference to these figures, a detailed explanation will be given of how the sensor controller 31 receives a pen signal using the comb coil CCx.

7 and 8 show only four comb tooth portions PT ₁ to PT ₄ for ease of explanation, but the actual comb coil CCx naturally has many more comb tooth portions PT. In the following, the other ends of the respective comb tooth portions PT ₁ to PT ₄ (the ends opposite to the ends connected to the base portion PB) will be referred to as ends T ₁ to T ₄ .

7, the switch circuit 30 according to the present embodiment includes a plurality of differential amplifiers 40 and a switch group including a plurality of switches 60 to 62. One differential amplifier 40 is provided for every two comb tooth portions PT. The switch 60 is a single-pole double-throw switch, and the switch 62 is a single-pole triple-throw switch, each of which is provided for each comb tooth portion PT. The switch 61 is a single-pole double-throw switch, and is provided for every two comb tooth portions PT. In the following description, as necessary, each configuration may be distinguished from the other configurations by adding the subscript "1" to the right of the reference numeral to the configuration corresponding to comb tooth portion _PT1 , the subscript " ₂ " to the right of the reference numeral to the configuration corresponding to comb tooth portion _PT2 , the subscript "3" to the right of the reference numeral to the configuration corresponding to comb tooth portion _PT3 , the subscript "4" to the right of the reference numeral to the configuration corresponding to comb tooth portion _PT4 , the subscript " ₁₂ " to the right of the reference numeral to the configuration corresponding to both comb tooth portions PT1 and _PT2 , and the subscript "34" to the right of the reference numeral to the configuration corresponding to both comb tooth portions PT3 and _PT4 .

The common terminal of switch _60-1 is connected to end T _-1 , one selection terminal is connected to the ground terminal, and the other selection terminal constitutes the illustrated node n- ₁ . The same is true for switches _60-2 to _60-4 , where the common terminal of switch _60-2 is connected to end T- ₂ , one selection terminal is connected to the ground terminal, and the other selection terminal constitutes the illustrated node n- ₂ , the common terminal of switch _60-3 is connected to end T- ₃ , one selection terminal is connected to the ground terminal, and the other selection terminal constitutes the illustrated node n- ₃ , and the common terminal of switch _60-4 is connected to end T- ₄ , one selection terminal is connected to the ground terminal, and the other selection terminal constitutes the illustrated node n- ₄ .

The common terminal of the switch _61-12 is connected to the node n- ₂ , one selection terminal is connected to the node n- ₁ , and the other selection terminal is connected to the second selection terminal of the switch _62-1 . The common terminal of the switch _62-1 is connected to the non-inverting input terminal of the differential amplifier _40-12 , the first selection terminal is connected to the node n _-1 , and the third selection terminal is connected to the ground terminal. The common terminal of the switch _62-2 is connected to the inverting input terminal of the differential amplifier _40-12 , the first selection terminal is connected to the node n- ₂ , the second selection terminal is connected to the node n- ₃ , and the third selection terminal is connected to the ground terminal.

The common terminal of the switch ₆₁₃₄ is connected to the node _n4 , one selection terminal is connected to the node _n3 , and the other selection terminal is connected to the second selection terminal of the switch _623. The common terminal of the switch ₆₂₃ is connected to the non-inverting input terminal of the differential amplifier ₄₀₃₄ , the first selection terminal is connected to the node _n3 , and the third selection terminal is connected to the ground terminal. The common terminal of the switch ₆₂₄ is connected to the inverting input terminal of the differential amplifier ₄₀₃₄ , the first selection terminal is connected to the node _n4 , and the third selection terminal is connected to the ground terminal. Although not shown, the second selection terminal of the switch ₆₂₄ is connected to the other selection terminal of the switch 60 corresponding to another comb tooth portion PT adjacent to the comb tooth portion _PT4 on the opposite side to the comb tooth portion _PT3 .

With the above configuration, the switch circuit 30 plays a role of switching the connection destination of the end _T2 (first end) between the inverting input terminal (second input terminal) of the differential amplifier ₄₀₁₂ and the non-inverting input terminal (first input terminal) of the differential amplifier _401. The sensor controller 31 controls this switching to receive the pen signal while switching in a time-division manner between a first state in which the end _T2 is connected to the inverting input terminal of the differential amplifier ₄₀₁₂ and a second state in which the end _T2 is connected to the non-inverting input terminal of the differential amplifier _4012. This will be described in detail below.

7 shows the first state of the switch circuit 30. As shown in the figure, in the first state, the end _T1 of the comb tooth portion _PT1 is connected to the non-inverting input terminal of the differential amplifier ₄₀₁₂ , and the end _T2 of the comb tooth portion _PT2 is connected to the inverting input terminal of the differential amplifier _4012. The end _T3 of the comb tooth portion _PT3 is connected to the non-inverting input terminal of the differential amplifier ₄₀₃₄ , and the end _T4 of the comb tooth portion _PT4 is connected to the inverting input terminal of the differential amplifier _4034. The same is true for the other comb tooth portions PT not shown. As a result, as shown by the dashed line in FIG. 7, one virtual loop coil is formed by the parts connecting the two adjacent comb tooth portions PT and the base portion PB. Hereinafter, the virtual loop coil formed in this way is referred to as a "virtual loop coil". Although each virtual loop coil is connected through the base portion PB, it has been found by the research of the present inventor that this does not substantially affect the reception characteristics of the pen signal.

8 shows the second state of the switch circuit 30. As shown in the figure, in the second state, the end _T2 of the comb tooth portion _PT2 is connected to the non-inverting input terminal of the differential amplifier ₄₀₁₂ , and the end _T3 of the comb tooth portion _PT3 is connected to the inverting input terminal of the differential amplifier _4012. The end _T1 of the comb tooth portion _PT1 is connected to the other differential amplifier ₄₀ adjacent to the differential amplifier ₄₀₁₂ on the opposite side of the differential amplifier 4034, together with the end of the other comb tooth portion PT adjacent to the comb tooth portion _PT1 on the opposite side of the comb tooth portion _PT2 . Similarly, the end _T4 of the comb tooth portion _PT4 is connected to the differential amplifier ₄₀₃₄ , together with the end of the other comb tooth portion PT adjacent to the comb tooth portion _PT4 on the opposite side of the comb tooth portion _PT3 . The same applies to the other comb tooth portions PT not shown. As a result, as shown by the dashed lines in Fig. 8, one virtual loop coil is formed by the portion connecting two adjacent comb tooth portions PT and the base portion PB, as in the case of Fig. 7, but the combination of two comb tooth portions PT constituting each virtual loop coil is shifted by one comb tooth portion PT in the x direction compared to the case of Fig. 7. In the second state, each virtual loop coil is also connected through the base portion PB, but as in the first state, there is no substantial effect on the reception characteristics of the pen signal.

When receiving a pen signal only in either the first state shown in FIG. 7 or the second state shown in FIG. 8, the spacing between the virtual loop coils in the x direction is wide, resulting in poor detection accuracy of the pen position in the x direction. According to the switch circuit 30 of this embodiment, the sensor controller 31 can time-share the reception of pen signals in the first state and the second state for each loop coil LCy, so that the spacing between the virtual loop coils can be reduced to zero overall. Therefore, it can be said that it is possible to improve the detection accuracy of the pen position when the comb coil CCx is used as the receiving coil of the EMR sensor.

As described above, according to the position detection system 1 of this embodiment, the reception of the pen signal in the first state and the reception of the pen signal in the second state can be executed in a time-division manner, and therefore the spacing between the virtual loop coils can be effectively set to zero, thereby improving the detection accuracy of the pen position when the comb coil CCx is used as the receiving coil of the EMR sensor.

In this embodiment, an example has been described in which one comb tooth portion PT is connected to one input terminal of the differential amplifier 40, but multiple comb tooth portions PT may be connected. Two modified examples that employ such a connection are described below.

Figures 9 and 10 are diagrams showing a first state and a second state of the switch circuit 30 according to a first modified example of this embodiment. This modified example is an example in which two comb tooth portions PT are connected to one input terminal of the differential amplifier 40. Note that in these figures, the detailed configuration within the switch circuit 30 is omitted, and only the connection state between each comb tooth portion PT and the differential amplifier 40 is shown. The switch circuit 30 according to this modified example has one differential amplifier 40 for every four comb tooth portions PT.

The sensor controller 31 according to this modification first selects four comb tooth portions PT from each of the comb coils CCx, starting from one end in the x direction. In the example of FIG. 9, the comb tooth portions PT ₁ to PT ₄ and the comb tooth portions PT ₅ to PT ₈ each constitute one set. The sensor controller 31 then connects two of the four comb tooth portions PT constituting each set from one end in the x direction to the non-inverting input terminal of the corresponding differential amplifier 40 in common, and the other two to the inverting input terminal of the corresponding differential amplifier 40 in common. As a result, a state (first state) in which four adjacent comb tooth portions PT are connected to one differential amplifier 40 is formed, as shown in FIG. 9. In this state, a predetermined number of ends (two in this case) including end _T4 (first end) of comb tooth portion _PT4 are connected to the inverting input terminal of the first differential amplifier 40, and the predetermined number of ends including end _T5 (second end) of comb tooth portion _PT5 are connected to the non-inverting input terminal of the second differential amplifier 40.

Next, the sensor controller 31 shifts the four comb tooth portions PT constituting each set one by one. FIG. 10 shows a state where this shift has been performed from the state of FIG. 9. As shown in the figure, in this case, the comb tooth portions PT ₂ to PT ₅ and the comb tooth portions PT ₆ to PT ₇ each constitute one set. Then, the sensor controller 31, as in the case of FIG. 9, commonly connects two of the four comb tooth portions PT constituting each set from one end side in the x direction to the non-inverting input terminal of the corresponding differential amplifier 40, and commonly connects the other two to the inverting input terminal of the corresponding differential amplifier 40. As a result, as shown in FIG. 10, a state (second state) in which four adjacent comb tooth portions PT are connected to one differential amplifier 40 is formed. In this state, the predetermined number of ends including end _T4 (first end) of comb tooth portion _PT4 and end _T5 (second end) of comb tooth portion _PT5 are connected to the inverting input terminal of the first differential amplifier 40, and the other ends of the predetermined number of comb tooth portions PT are connected to the non-inverting input terminal of the second differential amplifier 40.

The sensor controller 31 according to this modification performs a similar shift three times to form a set of four comb tooth portions PT in four combinations, and each time, performs a process of commonly connecting two of the four comb tooth portions PT constituting each set from one end side in the x direction to the non-inverting input terminal of the corresponding differential amplifier 40, and commonly connecting the other two to the inverting input terminal of the corresponding differential amplifier 40. As a result, four adjacent comb tooth portions PT are connected to one differential amplifier 40 in four states including the first state and the second state described above. The sensor controller 31 according to this modification receives the pen signal output from each differential amplifier 40 in each of the four states thus formed. Then, the received pen signal is used to detect the pen position and acquire pen data.

Figures 11 and 12 are diagrams showing a first state and a second state of the switch circuit 30 according to a second modified example of this embodiment, respectively. This modified example is an example in which four comb tooth portions PT are connected to one input terminal of the differential amplifier 40. In these figures, the detailed configuration within the switch circuit 30 is also omitted, and only the connection state between each comb tooth portion PT and the differential amplifier 40 is shown. The switch circuit 30 according to this modified example has one differential amplifier 40 for every eight comb tooth portions PT.

The sensor controller 31 according to this modification first selects eight comb tooth portions PT from each of the comb coils CCx, starting from one end in the x direction, as one set. In the example of FIG. 11, the comb tooth portions PT ₁ to PT ₈ form one set. The sensor controller 31 then connects four of the eight comb tooth portions PT from one end in the x direction of each set to the non-inverting input terminal of the corresponding differential amplifier 40 in common, and the remaining four to the inverting input terminal of the corresponding differential amplifier 40 in common. As a result, a state (first state) in which eight adjacent comb tooth portions PT are connected to one differential amplifier 40 is formed, as shown in FIG. 11. In this state, a predetermined number of ends (four in this case) including end _T8 (first end) of comb tooth portion _PT8 are connected to the inverting input terminal of the first differential amplifier 40, and the predetermined number of ends including end _T9 (second end) of comb tooth portion _PT9 are connected to the non-inverting input terminal of the second differential amplifier 40.

Next, the sensor controller 31 shifts the eight comb tooth portions PT constituting each set one by one. FIG. 12 shows a state where this shift has been performed from the state of FIG. 11. As shown in the figure, in this case, the comb tooth portions PT ₂ to PT ₁₀ constitute one set. Then, the sensor controller 31, as in the case of FIG. 11, commonly connects four of the eight comb tooth portions PT constituting each set from one end side in the x direction to the non-inverting input terminal of the corresponding differential amplifier 40, and commonly connects the other four to the inverting input terminal of the corresponding differential amplifier 40. As a result, as shown in FIG. 12, a state (second state) in which eight adjacent comb tooth portions PT are connected to one differential amplifier 40 is formed. In this state, the predetermined number of ends, including end _T8 (first end) of comb tooth portion _PT8 and end _T9 (second end) of comb tooth portion _PT9 , are connected to the inverting input terminal of the first differential amplifier 40, and the other ends of the predetermined number of comb tooth portions PT are connected to the non-inverting input terminal of the second differential amplifier 40.

The sensor controller 31 according to this modification performs the same shift seven times to form a set of eight comb tooth portions PT in eight combinations, and each time, performs a process of commonly connecting four of the eight comb tooth portions PT constituting each set from one end side in the x direction to the non-inverting input terminal of the corresponding differential amplifier 40, and commonly connecting the other four to the inverting input terminal of the corresponding differential amplifier 40. As a result, eight adjacent comb tooth portions PT are connected to one differential amplifier 40 in eight states including the first state and the second state described above. The sensor controller 31 according to this modification receives the pen signal output from each differential amplifier 40 in each of the eight states thus formed. Then, the received pen signal is used to detect the pen position and acquire pen data.

As shown in the two modified examples described above, according to the position detection system 1 of this embodiment, even when multiple comb tooth portions PT are connected to one input terminal of the differential amplifier 40, reception of the pen signal in multiple connection states can be executed in a time-division manner. Therefore, it is possible to improve the detection accuracy of the pen position when the comb coil CCx is used as the receiving coil of the EMR sensor. Furthermore, according to these modified examples, since multiple comb tooth portions PT are connected to one input terminal of the differential amplifier 40, it is possible to increase the reception strength of the pen signal compared to this embodiment.

Next, a position detection system 1 according to a third embodiment of the present invention will be described. The position detection system 1 according to this embodiment differs from the first embodiment in the internal configuration of the switch circuit 30. In other respects, it is similar to the position detection system 1 according to the first embodiment, so the following description will focus on the differences from the position detection system 1 according to the first embodiment.

Figure 13 is a diagram showing the internal configuration of the switch circuit 30 according to this embodiment. This figure shows only the configuration related to the illustrated loop coil LCx. This figure also shows one each of the loop coils LCx and LCy, and the sensor controller 31.

As shown in FIG. 13, the switch circuit 30 according to this embodiment includes, for each loop coil LCx, a differential amplifier 40, wiring lines L1 and L2, and a switch group including switch elements S1, S2, T1, and T2.

The differential amplifier 40 is an amplifier circuit (differential amplifier) that has a non-inverting input terminal, an inverting input terminal, and an output terminal, amplifies the potential difference between the non-inverting input terminal and the inverting input terminal, and outputs the amplified potential difference from the output terminal as an output voltage relative to the ground potential. The output signal of the differential amplifier 40 is supplied to the sensor controller 31 as the pen signal PS.

The wiring L1 connects one end of the loop coil LCx to the corresponding non-inverting input terminal of the differential amplifier 40. The switch element T1 is a single-pole, single-throw switch provided in the middle of this wiring L1. When the switch element T1 is on, one end of the loop coil LCx is connected to the non-inverting input terminal of the differential amplifier 40, whereas when the switch element T1 is off, one end of the loop coil LCx is disconnected from the non-inverting input terminal of the differential amplifier 40.

Wiring L2 connects the other end of the loop coil LCx to the inverting input terminal of the corresponding differential amplifier 40. Switch element T2 is a single-pole, single-throw switch provided in the middle of this wiring L2. When switch element T2 is on, the other end of the loop coil LCx is connected to the inverting input terminal of the differential amplifier 40, whereas when switch element T2 is off, the other end of the loop coil LCx is disconnected from the inverting input terminal of the differential amplifier 40.

The switch element S1 is a single-pole, single-throw switch provided between a power supply wiring to which a predetermined power supply potential Vref (e.g., ground potential or intermediate potential of the pen signal) is supplied and a portion of the wiring L1 between the switch element T1 and the loop coil LCx, and serves to supply the power supply potential Vref to one end of the loop coil LCx. Similarly, the switch element S2 is a single-pole, single-throw switch provided between a power supply wiring to which a predetermined power supply potential Vref is supplied and a portion of the wiring L2 between the switch element T2 and the loop coil LCx, and serves to supply the power supply potential Vref to the other end of the loop coil LCx.

The control of the switch elements S1 and S2 is performed by a precharge signal pre generated by the sensor controller 31. The control of the switch elements T1 and T2 is performed by a selection signal sel generated by the sensor controller 31. The control of the switch elements S1, S2, T1, and T2 performed by the sensor controller 31 using these signals will be described in detail below.

Figure 14 shows the waveforms of signals related to the control of switch elements S1, S2, T1, and T2. The voltage PE shown in the figure is the voltage across the coil that constitutes the resonant circuit of the electromagnetic induction pen 2. When the sensor controller 31 starts to emit an alternating magnetic field from the loop coil LCy at time t1, the voltage PE rises in the electromagnetic induction pen 2 located nearby, as shown in the figure. The sensor controller 31 continues to emit this alternating magnetic field from time t1 until time t3, a predetermined time Ta later.

The sensor controller 31 activates the precharge signal pre at time t2 (a predetermined time Tb (<Ta) after time t1) while continuing to send out the alternating magnetic field. This turns on the switch elements S1 and S2 shown in FIG. 13, and starts supplying the power supply potential Vref to the loop coil LCx. The sensor controller 31 maintains the precharge signal pre in an active state until time t3 or the time immediately before that, and then returns the precharge signal pre to an inactive state. By performing this series of processes, each loop coil LCx can be precharged, so that the influence of the alternating magnetic field sent out from the loop coil LCy can be eliminated from the loop coil LCx, and the SNR of the pen signal PS can be improved.

As shown in FIG. 13, the switch circuit 30 is configured so that the power supply potential Vref is supplied to both one end and the other end of the loop coil LCx in order to complete the precharging in a shorter time. That is, since the loop coil LCx has a time constant as described above, even if the power supply potential Vref is supplied to the loop coil LCx, the entire coil does not immediately become the power supply potential Vref, but rather the part close to the power supply wiring gradually transitions to the power supply potential Vref over a certain period of time. Therefore, if the power supply potential Vref is supplied to both one end and the other end of the loop coil LCx, this time can be shortened. However, it is not essential to supply the power supply potential Vref to both one end and the other end of the loop coil LCx, and it is also possible to supply the power supply potential Vref to only one of them.

Returning to FIG. 14, the sensor controller 31 stops transmitting the alternating magnetic field at time t3, and at the same time activates the selection signal sel to turn on the switch elements T1 and T2. The alternating magnetic field transmitted from the electromagnetic induction pen 2 then generates an alternating current in the loop coil LCx, which is supplied to the sensor controller 31 as the pen signal PS as shown in the figure. This enables the sensor controller 31 to obtain the pen position and pen data based on the pen signal PS. The sensor controller 31 maintains the selection signal sel in an active state until time t4 when it next starts transmitting the alternating magnetic field, and then returns the selection signal sel to an inactive state. Subsequent processing is a repetition of the processing described up to this point.

As described above, according to the switch circuit 30 and the sensor controller 31 of this embodiment, each loop coil LCx can be precharged by turning on the switch elements S1 and S2, so that the influence of the alternating magnetic field sent from the transmitting loop coil LCy can be eliminated from each receiving loop coil LCx, thereby improving the SNR of the pen signal PS.

Figure 15 is a diagram showing a method of driving an EMR sensor according to a modified example of this embodiment. The sensor controller 31 according to this modified example differs from the sensor controller 31 according to this embodiment in that when performing the global scan described above, the pen signal is received from only half of the multiple loop coils LCx, rather than all of them, each time an AC current is passed through each loop coil LCy. The following will focus on the differences and explain them in detail. Note that, for simplicity of explanation, only six loop coils LCx and LCy are shown in Figure 15, but the same applies when the EMR sensor includes more loop coils LCx and LCy.

Figure 15(a) shows a first reception mode of the pen signal, and Figure 15(b) shows a second reception mode of the pen signal. The sensor controller 31 of this modified example detects the pen position by alternating between the first reception mode and the second reception mode.

As a premise, the switch circuit 30 according to this modified example is configured so that the switch elements T1, T2 are controlled by different selection signals sel for the 2n-1th (n is a natural number; odd-numbered) loop coil LCx from one end in the x direction among the multiple loop coils LCx and the 2nth (even-numbered) loop coil LCx from one end in the x direction among the multiple loop coils LCx. As a result, the switch circuit 30 according to this modified example is configured to be able to switch between a first state in which one end and the other end of the 2n-1th (odd-numbered) loop coil LCx from one end side in the x direction among the multiple loop coils LCx are connected to the non-inverting input terminal and the inverting input terminal of the corresponding differential amplifier 40, while one end and the other end of the 2nth (even-numbered) loop coil LCx are disconnected from the non-inverting input terminal and the inverting input terminal of the corresponding differential amplifier 40, and a second state in which one end and the other end of the 2nth (even-numbered) loop coil LCx from one end side in the x direction among the multiple loop coils LCx are connected to the non-inverting input terminal and the inverting input terminal of the corresponding differential amplifier 40, while one end and the other end of the 2n-1th (odd-numbered) loop coil LCx are disconnected from the non-inverting input terminal and the inverting input terminal of the corresponding differential amplifier 40, according to control from the sensor controller 31.

In the first reception mode shown in FIG. 15(a), the sensor controller 31 sets the switch circuit 30 to the first state when passing an AC current through the 2m-1th (m is a natural number; odd-numbered) loop coil LCy from one end in the y direction among the multiple loop coils LCy, and sets the switch circuit 30 to the second state when passing an AC current through the 2mth (even-numbered) loop coil LCy from one end in the y direction among the multiple loop coils LCy, thereby receiving the pen signals output from each of the multiple differential amplifiers 40. According to this process, detection of the pen position is performed centered on the hatched portion in FIG. 15(a).

On the other hand, in the second reception mode shown in FIG. 15(b), the sensor controller 31 sets the switch circuit 30 to the second state when passing an AC current through the 2m-1th (odd-numbered) loop coil LCy from one end in the y direction among the multiple loop coils LCy, and sets the switch circuit 30 to the first state when passing an AC current through the 2mth (even-numbered) loop coil LCy from one end in the y direction among the multiple loop coils LCy, thereby receiving the pen signals output from each of the multiple differential amplifiers 40. According to this process, the detection of the pen position is performed centering on the hatched portion in FIG. 15(b). When compared with FIG. 15(a), it can be seen that hatching has been added to the portion that was not hatched in FIG. 15(a).

According to this modified example, it is possible to detect the pen position with higher accuracy than when, for example, in the first reception mode, the switch circuit 30 is in the first state when an AC current is passed through any loop coil LCy, and in the second reception mode, the switch circuit 30 is in the second state when an AC current is passed through any loop coil LCy. As can be seen from FIGS. 15(a) and (b), this is because the hatched parts (i.e., parts that acquire the intensity of the pen signal) are arranged (i.e., arranged in a grid pattern) above, below, left and right of the non-hatched parts (i.e., parts that do not acquire the intensity of the pen signal), so that the intensity distribution of the pen signal can be derived with higher accuracy in all directions.

In addition, according to this modified example, the number of differential amplifiers 40 used simultaneously is half that of the present embodiment, so it is also possible to halve the number of differential amplifiers 40 provided in the switch circuit 30. For the same reason, it is also possible to halve the number of circuits placed in the sensor controller 31 to receive pen signals.

Figure 16 is a diagram showing the configuration of a position detection system 1 according to a fourth embodiment of the present invention. The position detection system 1 according to this embodiment differs from the position detection system 1 according to the third embodiment in that it uses a comb coil CCx consisting of a base portion PB and multiple comb teeth portions PT as the receiving coil of the EMR sensor, rather than multiple loop coils LCx. In addition, the internal configuration of the switch circuit 30 and the content of the control of the switch circuit 30 by the sensor controller 31 are also different from those of the position detection system 1 according to the third embodiment. In other respects, it is similar to the position detection system 1 according to the third embodiment, so the following description will focus on the differences from the position detection system 1 according to the third embodiment.

As shown in FIG. 16, the comb coil CCx is configured by connecting a base portion PB, which is a single wire extending in the x direction, to multiple comb tooth portions PT, which are wires extending in the y direction. One end of each comb tooth portion PT is connected to the base portion PB, and the other end is connected to the switch circuit 30.

17 and 18 are diagrams showing the internal configuration of the switch circuit 30 according to this embodiment. These diagrams show only the parts of the internal configuration of the switch circuit 30 that are related to receiving pen signals in some of the comb-tooth portions PT. In the following description, the x-th comb-tooth portion PT from one end side in the x direction among the multiple comb-tooth portions PT may be referred to as comb-tooth portion PT _x to distinguish it from the other comb-tooth portions PT.

17 and 18, the switch circuit 30 according to the present embodiment is configured to include a plurality of differential amplifiers 50 and a plurality of switches 51 and 52. One differential amplifier 50 is provided for every two comb tooth portions PT, and the switches 51 and 52 are provided for each comb tooth portion PT. The configuration and operation of each differential amplifier 50 are similar to those of the differential amplifier 40 described in the third embodiment. In the following description, the differential amplifiers 50 provided corresponding to the comb tooth portions PT _x-1 and PT _x among the plurality of differential amplifiers 50 may be referred to as differential amplifier 50 _x to be distinguished from the other differential amplifiers 50.

The switch 51 is a single-pole, triple-throw switch. The common terminal of the switch 51 is connected to the other end of the corresponding comb tooth portion PT. The first selection terminal of the switch 51, whose common terminal is connected to the comb tooth portion PT _x-1 , is connected to the non-inverting input terminal of the differential amplifier 50 _x-2 , the second selection terminal is connected to the open end, and the third selection terminal is connected to the inverting input terminal of the differential amplifier 50 _x . The first selection terminal of the switch 51, whose common terminal is connected to the comb tooth portion PT _x , is connected to the inverting input terminal of the differential amplifier 50 _x , the second selection terminal is connected to the open end, and the third selection terminal is connected to the non-inverting input terminal of the differential amplifier 50 _x .

The switch 52 is a single-pole, single-throw switch that is provided between a power supply line that is supplied with a predetermined power supply potential Vref (e.g., ground potential) and a line that connects the common terminal of the corresponding switch 51 to the comb tooth portion PT, and serves to supply the power supply potential Vref to the corresponding comb tooth portion PT.

The switches 51 and 52 are controlled by the sensor controller 31. The control of switch 52 is performed to precharge the comb tooth portion PT, and is performed at the same timing as the control of switches S1 and S2 described with reference to FIG. 14. In addition, the control of switch 51 for connecting the common terminal to the second selection terminal (open end) is also performed at the same timing as the timing for turning off switches T1 and T2 described with reference to FIG. 14. As a result, each differential amplifier 50 is connected to the comb tooth portion PT only during the period when the transmission of the alternating magnetic field from the loop coil LCy is stopped.

Regarding the timing of connecting the common terminal to the first selection terminal or the third selection terminal in the control of the switch 51, the sensor controller 31 controls so that the spacing between the virtual loop coils formed within the comb coil CCx is effectively zero, in order to detect the pen position with high accuracy even when the comb coil CCx is used as the receiving coil of the EMR sensor. This point will be explained in detail below.

First, the state of the switch circuit 30 will be described. The switch circuit 30 is configured to be able to switch between a first state (state shown in FIG. 17) in which the third selection terminal is selected in each switch 51 and a second state (state shown in FIG. 18) in which the first selection terminal is selected in each switch 51 under the control of the sensor controller 31. In the first state, as shown in FIG. 17, the other end of the 2n-1th (n is a natural number; odd-numbered) comb tooth portion PT from one end side in the x direction among the multiple comb tooth portions PT and the other end of the 2nth (even-numbered) comb tooth portion PT are connected to the inverting input terminal and non-inverting input terminal of the same differential amplifier 50. As a result, a virtual loop coil is formed by the 2n-1th comb tooth portion PT, the 2nth comb tooth portion PT, and the portion of the base portion PB that connects them (the portion circled in FIG. 17). On the other hand, in the second state, as shown in FIG. 18, the other end of the 2nth (even-numbered) comb tooth portion PT and the other end of the 2n+1th (odd-numbered) comb tooth portion PT from one end side in the x direction among the multiple comb tooth portions PT are connected to the inverting input terminal and non-inverting input terminal of the same differential amplifier 50. As a result, a virtual loop coil is formed by the 2nth comb tooth portion PT, the 2n+1th comb tooth portion PT, and the portion of the base portion PB that connects them (the portion circled in FIG. 18).

For each loop coil LCy, the sensor controller 31 starts supplying AC current to that loop coil LCy, stops the supply, and then switches the switch circuit 30 to the first state to receive the pen signal. It also starts supplying AC current to the same loop coil LCy again, stops the supply, and then switches the switch circuit 30 to the second state to receive the pen signal. This process is common to global scan and local scan. As a result, in both global scan and local scan, the spacing between the virtual loop coils formed by the comb coil CCx can be effectively set to zero, making it possible to improve the detection accuracy of the pen position when the comb coil CCx is used as the receiving coil of the EMR sensor.

As described above, the switch circuit 30 and sensor controller 31 according to this embodiment can execute the reception of the pen signal in the first state and the reception of the pen signal in the second state in a time-division manner, and therefore the spacing between the virtual loop coils can be effectively set to zero, thereby improving the detection accuracy of the pen position when the comb coil CCx is used as the receiving coil of the EMR sensor.

In addition, according to the switch circuit 30 and the sensor controller 31 of this embodiment, each comb tooth portion PT can be precharged by turning on the switch 52, so that, as in the third embodiment, the influence of the alternating magnetic field sent from the loop coil LCy on the transmitting side can be eliminated from each comb tooth portion PT on the receiving side, and the SNR of the pen signal PS can be improved.

Figure 19 is a diagram showing a method of driving an EMR sensor according to a modified example of this embodiment. The sensor controller 31 according to this modified example differs from the sensor controller 31 according to this embodiment in that, when performing one global scan, for each loop coil LCy, only one of receiving a pen signal using the switch circuit 30 in the first state and receiving a pen signal using the switch circuit 30 in the second state is performed, rather than both. The following will focus on the differences and explain them in detail. Note that, for the sake of simplicity, only six loop coils LCy and seven comb-tooth portions PT are shown in Figure 19, but the same applies when the EMR sensor includes more loop coils LCy and comb-tooth portions PT.

Figure 19 (a) shows a first reception mode of the pen signal, and Figure 19 (b) shows a second reception mode of the pen signal. The sensor controller 31 of this modified example detects the pen position by alternately performing a global scan in the first reception mode and a global scan in the second reception mode.

In the first reception mode, the sensor controller 31 receives pen signals output from each of the multiple differential amplifiers 50 by setting the switch circuit 30 to the first state when passing an AC current through the 2m-1th (m is a natural number; odd-numbered) loop coil LCy from one end in the y direction among the multiple loop coils LCy, and by setting the switch circuit 30 to the second state when passing an AC current through the 2mth (even-numbered) loop coil LCy from one end in the y direction among the multiple loop coils LCy. According to this process, detection of the pen position is performed centered on the hatched portion in FIG. 19(a).

On the other hand, in the second reception mode, the sensor controller 31 sets the switch circuit 30 to the second state when passing an AC current through the 2m-1th (odd-numbered) loop coil LCy from one end in the y direction among the multiple loop coils LCy, and sets the switch circuit 30 to the first state when passing an AC current through the 2mth (even-numbered) loop coil LCy from one end in the y direction among the multiple loop coils LCy, thereby receiving the pen signals output from each of the multiple differential amplifiers 50. According to this process, the detection of the pen position is performed centering on the hatched portion in FIG. 19(b). When compared with FIG. 19(a), it can be seen that hatching has been added to the portion that was not hatched in FIG. 19(a).

According to this modified example, it is possible to complete one global scan in half the time compared to the present embodiment. The accuracy of the pen position detected in one global scan is lower than in the present embodiment, but since the hatched parts in each global scan are arranged in a lattice pattern similar to the modified example of the third embodiment described with reference to FIG. 15, it is possible to detect the pen position with higher accuracy than, for example, when the switch circuit 30 is in the first state when AC current is passed through any loop coil LCy in the first reception mode, and when the switch circuit 30 is in the second state when AC current is passed through any loop coil LCy in the second reception mode.

Figure 20 is a diagram showing the configuration of a position detection system 1 according to a fifth embodiment of the present invention. The position detection system 1 according to this embodiment differs from the position detection system 1 according to the fourth embodiment in that, instead of an interdigital coil CCx, the receiving coil of the EMR sensor uses a number of linear electrodes LE each extending in the y direction and arranged side by side in the x direction. In other respects, it is similar to the position detection system 1 according to the fourth embodiment, so the following description will focus on the differences from the position detection system 1 according to the fourth embodiment.

The configuration of the EMR sensor according to this embodiment is, in short, a configuration in which the base portion PB is removed from the comb coil CCx of the fourth embodiment. Figures 21 and 22 are diagrams showing the internal configuration of the switch circuit 30 according to this embodiment. As can be understood by comparing these figures with Figures 17 and 18, the configuration within the switch circuit 30 is similar to that within the switch circuit 30 according to the fourth embodiment, except that the connection destination is the linear electrode LE instead of the comb tooth portion PT. Therefore, the switch circuit 30 according to this embodiment is also configured to be switchable between the first state and the second state described in the fourth embodiment under the control of the sensor controller 31. Figure 21 shows the first state, and Figure 22 shows the second state. The reception process of the pen signal performed by the sensor controller 31 using this control may also be similar to that of the fourth embodiment.

In this embodiment, since each linear electrode LE is electrically isolated, a virtual loop coil as described in the fourth embodiment is not formed when the switch circuit 30 is in either the first or second state. Compared to the loop coil LCx described in the third embodiment and the comb coil CCx described in the fourth embodiment, the coupling between the linear electrode LE and the coil in the electromagnetic induction pen 2 is weaker, so the reception strength of the pen signal received by each linear electrode LE is weaker than in the third and fourth embodiments. However, according to the configuration of the switch circuit 30 according to this embodiment, the effect of increasing the reception strength of the pen signal is obtained, especially in the vicinity of the pen position. This is because the sign of the pen signal is opposite between the linear electrode LE on one side of the pen position in the x direction and the linear electrode LE on the other side. This point will be explained below with reference to a graph of reception strength.

Figure 23 shows the simulation results of the reception strength of the pen signal. Graph G1 in the figure shows the simulation results of the reception strength of the pen signal received by the sensor controller 31 according to this embodiment. On the other hand, graph G0 shows the simulation results of the reception strength of the pen signal received by the sensor controller 31 when using a position detection device of a type that supplies the pen signal received by each linear electrode LE to the sensor controller 31 alone without using a differential amplifier 50. The horizontal axis in the figure shows the serial number of the linear electrodes LE. The position on the horizontal axis of each point of graph G1 corresponds to the middle position in the x direction of two linear electrodes LE connected to the same differential amplifier 50. This is also true for graph G2, which will be described later.

Figure 23 shows an example in which the pen tip of the electromagnetic induction pen 2 is between the 10th linear electrode LE and the 11th linear electrode LE. Looking first at graph G0, it can be seen that the sign of the reception strength of the pen signal received at the 10th or lower linear electrodes LE is opposite to that of the reception strength of the pen signal received at the 11th or lower linear electrodes LE, and that in the vicinity of the pen position, the reception strength of the pen signal becomes weak to almost zero.

Next, looking at graph G1, it can be seen that a normal distribution-like distribution with a peak at the pen position is obtained. Such a distribution is obtained because the pen signals of opposite signs are reinforced by the differential amplifier 50. From this result, it can be seen that the position detection device 3 according to this embodiment has the effect of increasing the reception strength of the pen signal in the vicinity of the pen position.

As described above, according to the position detection device 3 of this embodiment, the pen signals having opposite signs are reinforced by the differential amplifier 50, so that it is possible to increase the reception strength of the pen signal in the vicinity of the pen position when the linear electrode LE is used as an Rx coil.

24 and 25 are diagrams showing the internal configuration of the switch circuit 30 according to the first modified example of this embodiment. FIG. 24 shows a first state, and FIG. 25 shows a second state. As can be understood by comparing FIG. 24 and FIG. 25 with FIG. 21 and FIG. 22, the switch circuit 30 according to this modified example is different from the switch circuit 30 according to this embodiment in that the two linear electrodes LE connected to the same differential amplifier _50x are not two directly adjacent to each other, but two adjacent electrodes LE sandwiched between them. In other respects, it is the same as the switch circuit 30 according to this embodiment, and the contents of the control of the switch circuit 30 by the sensor controller 31 are also the same as those according to this embodiment.

The switch circuit 30 according to this modified example is configured to be able to switch between a first state in which the end of the 2n-kth (k=3, n is a natural number greater than k/2) linear electrode LE from one end side in the x direction and the end of the 2nth linear electrode LE from among the multiple linear electrodes LE are connected to the inverting input terminal and non-inverting input terminal of the same differential amplifier 50, and a second state in which the end of the 2nth linear electrode LE from one end side in the x direction and the end of the 2n+kth linear electrode LE from among the multiple linear electrodes LE are connected to the inverting input terminal and non-inverting input terminal of the same differential amplifier 50. In this modified example, k=3, but if k=1, the switch circuit 30 described in this embodiment is obtained. Generally speaking, k may be any natural number that is an odd number, and the value of k that maximizes the reception strength of the pen signal in the vicinity of the pen position may be selected.

Graph G2 in FIG. 23 shows the simulation results of the reception strength of the pen signal received by the sensor controller 31 according to this modified example. As can be seen by comparing with graph G1, the switch circuit 30 according to this modified example obtains a normal distribution-like shape with a peak at the pen position, similar to graph G1, and the peak reception strength is greater than that of graph G1. Therefore, it can be said that the position detection device 3 according to this modified example makes it possible to further increase the reception strength of the pen signal in the vicinity of the pen position when the linear electrode LE is used as an Rx coil.

Figure 26 is a diagram showing a method of driving an EMR sensor according to a second modified example of this embodiment. The sensor controller 31 according to this modified example differs from the sensor controller 31 according to this embodiment in that, when performing one global scan, for each loop coil LCy, only one of receiving a pen signal using the switch circuit 30 in the first state and receiving a pen signal using the switch circuit 30 in the second state is performed, rather than both. The following will focus on the differences and explain them in detail. Note that, for the sake of simplicity, only six loop coils LCy and seven linear electrodes LE are shown in Figure 26, but the same applies when the EMR sensor includes more loop coils LCy and linear electrodes LE.

Figure 26 (a) shows a first reception mode of the pen signal, and Figure 26 (b) shows a second reception mode of the pen signal. The sensor controller 31 of this modified example detects the pen position by alternately performing a global scan in the first reception mode and a global scan in the second reception mode.

In the first reception mode, the sensor controller 31 receives pen signals output from each of the multiple differential amplifiers 50 by setting the switch circuit 30 to the first state when passing an AC current through the 2m-1th (m is a natural number; odd-numbered) loop coil LCy from one end in the y direction among the multiple loop coils LCy, and by setting the switch circuit 30 to the second state when passing an AC current through the 2mth (even-numbered) loop coil LCy from one end in the y direction among the multiple loop coils LCy. According to this process, detection of the pen position is performed centered on the hatched portion in FIG. 26(a).

On the other hand, in the second reception mode, the sensor controller 31 sets the switch circuit 30 to the second state when passing an AC current through the 2m-1th (odd-numbered) loop coil LCy from one end in the y direction among the multiple loop coils LCy, and sets the switch circuit 30 to the first state when passing an AC current through the 2mth (even-numbered) loop coil LCy from one end in the y direction among the multiple loop coils LCy, thereby receiving the pen signal output from each of the multiple differential amplifiers 50. According to this process, the detection of the pen position is performed centering on the hatched portion in FIG. 26(b). When compared with FIG. 26(a), it can be seen that hatching has been added to the portion that was not hatched in FIG. 26(a).

According to this modified example, it is possible to complete one global scan in half the time compared to the present embodiment. The accuracy of the pen position detected in one global scan is lower than in the present embodiment, but since the hatched parts in each global scan are arranged in a lattice pattern similar to the modified example of the third embodiment described with reference to FIG. 15, it is possible to detect the pen position with higher accuracy than, for example, when the switch circuit 30 is in the first state when AC current is passed through any loop coil LCy in the first reception mode, and when the switch circuit 30 is in the second state when AC current is passed through any loop coil LCy in the second reception mode.

Next, a position detection system 1 according to a sixth embodiment of the present invention will be described. The position detection system 1 according to this embodiment differs from the third embodiment in terms of the internal processing of the sensor controller 31. In other respects, it is similar to the position detection system 1 according to the third embodiment, so the following description will focus on the differences from the position detection system 1 according to the third embodiment.

Figure 27 is a diagram showing the problems that arise when receiving a pen signal using the position detection system 1 according to the third embodiment. Also, Figure 28 is a diagram explaining the azimuth angle θ and tilt angle φ used in Figure 27. Before explaining the position detection system 1 according to this embodiment, the problems that are solved by the position detection system 1 according to this embodiment will be explained below with reference to these figures.

As shown in FIG. 28, three angles are defined for the electromagnetic induction pen 2: azimuth angle θ, tilt angle φ, and rotation angle ψ. The azimuth angle θ is an angle that indicates the direction in which the tip of the electromagnetic induction pen 2 in contact with the touch surface 3a points, and is represented by the angle between a predetermined axis set within the touch surface 3a and the projection of the pen axis of the electromagnetic induction pen 2 onto the touch surface 3a. The tilt angle φ is an angle that indicates the inclination of the electromagnetic induction pen 2 with respect to the touch surface 3a, and is represented by the angle between the pen axis of the electromagnetic induction pen 2 and the touch surface 3a. The rotation angle ψ is an angle that indicates the amount of rotation of the electromagnetic induction pen 2 itself around the pen axis. The problem solved by the position detection system 1 according to this embodiment relates to the azimuth angle θ and tilt angle φ out of these angles.

Figure 27 shows the reception level of the pen signal PS received by the loop coil LCx corresponding to each x coordinate when the tip of the electromagnetic induction pen 2 is at the x coordinate = 0 mm and the azimuth angle θ and tilt angle φ are (θ, φ) = (0°, 0°), (0°, 60°), (180°, 60°), and (90°, 60°), respectively. As shown in the figure, when (θ, φ) = (0°, 0°) (90°, 60°), the peak of the reception level of the pen signal PS is at the x coordinate = 0 mm, while when (θ, φ) = (0°, 60°), the peak position of the reception level of the pen signal PS is shifted to the negative side. Also, when (θ, φ) = (180°, 60°), the peak position of the reception level of the pen signal PS is shifted to the positive side. Thus, in the position detection system 1 according to the third embodiment, the combination of the azimuth angle θ and tilt angle φ of the electromagnetic induction pen 2 may cause the peak position of the reception level of the pen signal PS to shift from the actual position of the pen tip. The position detection system 1 according to this embodiment is intended to improve the deterioration of the detection accuracy of the pen position caused by such a shift.

29A is a diagram for explaining the process performed by the sensor controller 31 according to this embodiment. As shown in the figure, the sensor controller 31 according to this embodiment is configured to add the pen signal PS _n received in the n-th loop coil LCx _n and the pen signals PS received in each of the one or more loop coils _LCx in the vicinity of the loop coil LCx n with different weighting, and derive the position of the electromagnetic induction pen 2 using the sum pen signal PS _SUM obtained by the addition.

Specifically, the sensor controller 31 according to this embodiment performs the above-mentioned addition of the pen signals PS _n-2 to PS n+2 received at the five loop coils LCx, ie, the n-2th loop coil LCx _{n -2} to the n+2th loop coil LCx _n+2 , such that the weighting of the pen signals PS _n-1 to PS _n+1 received at the three loop coils LCx located in the center of the five loop coils LCx is twice the weighting of the pen signals _n-2 and PS _n+2 received at the other two loop coils LCx. As a result, as shown in the figure, PS _SUM becomes PS _n-2 +2.PS _n-1 +2.PS _n +2.PS _n+1 +PS _n+2 .

Fig. 29(b) is a diagram showing a virtual loop coil VLCx obtained by the addition shown in Fig. 29(a). As shown in the figure, the sum pen signal PS _SUM obtained by performing the addition shown in Fig. 29(a) is a signal equivalent to the pen signal PS received by a double-wound coil with an inner wiring width of X1 (the width of three loop coils LCx) and a distance between the outer wiring and the inner wiring of X2 (the width of one loop coil LCx).

Fig. 30 is a diagram showing the reception level of the additive pen signal PS _{SUM when the pen tip of the electromagnetic induction pen 2 is at the position of x coordinate = 0 mm. As in Fig. 27, this figure shows the reception level of the additive pen signal PS SUM} (a signal obtained by weighting and adding the pen signals PS received by five loop coils LCx centered on that loop coil LCx) obtained at the loop coil LCx corresponding to each x coordinate when the azimuth angle θ and tilt angle φ are (θ, φ) ₌ (0°, 0°), (0°, 60°), (180°, 60°), and (90°, 60°), respectively.

30, the peak position of the reception level of the additive pen signal PS _SUM is at the position of x coordinate = 0 mm, regardless of the azimuth angle θ and tilt angle φ of the electromagnetic induction pen 2. When (θ, φ) = (90°, 60°), the reception level of the additive pen signal PS _SUM is slightly depressed at the position of x coordinate = 0 mm, but since the shape is symmetrical, this depression does not deteriorate the detection accuracy of the pen position. Therefore, it can be said that the position detection system 1 according to this embodiment can detect the position of the electromagnetic induction pen 2 with high accuracy even if it is tilted with respect to the touch surface 3a.

As described above, according to the position detection system 1 of this embodiment, the position of the electromagnetic induction pen 2 is derived using the sum pen signal PS _SUM obtained by adding up the pen signals PS received by multiple loop coils LCx with different weightings, so that even if the electromagnetic induction pen 2 is tilted with respect to the touch surface 3a, its position can be detected with high accuracy.

Next, a position detection system 1 according to a seventh embodiment of the present invention will be described. The position detection system 1 according to this embodiment differs from the fourth embodiment in that the position detection device 3 is a smartphone with a built-in foldable display, in the internal configuration of the switch circuit 30, and in the internal processing of the sensor controller 31. In other respects, it is the same as the position detection system 1 according to the fourth embodiment, so the following description will focus on the differences from the position detection system 1 according to the fourth embodiment.

Here, in the following description, the position detection method of the electromagnetic induction pen 2 realized by the switch circuit 30 and the sensor controller 31 according to the fourth embodiment may be referred to as the "ODD/EVEN method." "ODD" and "EVEN" respectively correspond to the first state and the second state of the switch circuit 30 described in the fourth embodiment. Also, the position detection method of the electromagnetic induction pen 2 realized by the switch circuit 30 and the sensor controller 31 according to this embodiment may be referred to as the "A/B/C method." As will be described in detail later, the switch circuit 30 according to this embodiment is configured to be switchable between three states, from the first state to the third state, and "A," "B," and "C" respectively correspond to the first state to the third state.

Figure 31(a) is a plan view of the EMR sensor 33 included in the position detection device 3 according to this embodiment, and Figure 31(b) is a cross-sectional view of the EMR sensor 33 corresponding to the line A-A shown in Figure 31(a). As shown in these figures, the EMR sensor 33 is composed of a substrate 34 on which a receiving coil and a transmitting coil are formed, and a magnetic sheet 35 composed of a magnetic material. The magnetic sheet 35 is a member that functions as a magnetic path for the magnetic field generated by the coil in the substrate 34, and is arranged so as to cover the entire one surface of the substrate 34 (the surface opposite the touch surface 3a).

If the display (not shown) included in the position detection device 3 is a foldable display, it is of course necessary for the EMR sensor 33 to also be configured to be foldable. The illustrated part 36 is a conductive hinge part required for this purpose, and is disposed between the substrate 34 and the magnetic sheet 35 along the folding line FL.

Figure 32(a) is a diagram that shows the distribution of the reception level of the pen signal PS received when the tip of the electromagnetic induction pen 2 is at each position in the x direction, assuming that the ODD/EVEN method is adopted in the position detection device 3 according to this embodiment. As shown in the figure, according to the ODD/EVEN method, the reception level of the pen signal PS drops significantly near the folding line FL. This is because the magnetic field is disturbed by the hinge part 36 shown in Figures 31(a) and 31(b). With the reception level as shown in Figure 32(a), it is difficult to derive the pen position near the folding line FL, and it was necessary to improve the reception level of the pen signal PS near the folding line FL. The position detection system 1 according to this embodiment aims to achieve such an improvement in the reception level of the pen signal PS by using the A/B/C method instead of the ODD/EVEN method.

Figures 33 to 35 are diagrams showing the internal configuration of the switch circuit 30 according to this embodiment. As with Figures 17 and 18, these diagrams show only the parts of the internal configuration of the switch circuit 30 that are related to reception of pen signals in some of the comb-tooth portions PT. In the following description, the x-th comb-tooth portion PT from one end side in the x direction among the multiple comb-tooth portions PT may be referred to as comb-tooth portion PT _x to distinguish it from the other comb-tooth portions PT.

33 to 35, the switch circuit 30 according to the present embodiment has one differential amplifier 50 for every three comb tooth portions PT. In the following description, among the multiple differential amplifiers 50, those provided corresponding to the comb tooth portions PT _x−1 , PT _x , and PT _x+1 may be referred to as differential amplifier 50 _x to be distinguished from the other differential amplifiers 50.

The common terminal of the switch 51 according to this embodiment is connected to the other end of the corresponding comb tooth portion PT. The first selection terminal of the switch 51, whose common terminal is connected to the comb tooth portion PT _x, is connected to the inverting input terminal of the differential amplifier 50 _x , the second selection terminal is connected to the open end, and the third selection terminal is connected to the non-inverting input terminal of the differential amplifier 50 _x . The first selection terminal of the switch 51, whose common terminal is connected to the comb tooth portion PT _x-1, is connected to the inverting input terminal of the differential amplifier 50 _x , the second selection terminal is connected to the open end, and the third selection terminal is connected to the non-inverting input terminal of the differential amplifier 50 _x-2 . The first selection terminal of the switch 51, whose common terminal is connected to the comb tooth portion PT _x+1, is connected to the inverting input terminal of the differential amplifier 50 _x+2 , the second selection terminal is connected to the open end, and the third selection terminal is connected to the non-inverting input terminal of the differential amplifier 50 _x . To summarize the above configuration from the perspective _of the differential amplifier 50 _x , the first selection terminals of the three switches 51 corresponding to the comb tooth portions PT _x-2 , PT _x-1 , and PT _x are commonly connected to the inverting input terminal of the differential amplifier 50 _x , and the third selection terminals of the three switches 51 corresponding to the comb tooth portions PT _x , PT _x+1 , and PT _x+2 are commonly connected to the non-inverting input terminal of the differential amplifier 50 x.

The switch circuit 30 according to this embodiment functions as a selection circuit that selects two of the five corresponding comb tooth portions PT (for differential amplifier 50 _x , the five comb tooth portions are PT _x-2 , PT _x-1 , PT _x , PT _x+1 , and PT _x+2 ) for each differential amplifier 50 in accordance with the control of the sensor controller 31, and connects the two selected comb tooth portions PT to the differential amplifier 50 as a receiving circuit.

The sensor controller 31 according to this embodiment controls the switch circuit 30 so that, for example, in the case of the differential amplifier 50 _x , a first state in which the comb teeth PT _{x -2} and PT _x are selected, _a second state in which the comb teeth PT _x- 1 and PT _x+1 are selected, and a third state in which the comb teeth PT x and PT x+2 are selected appear in sequence. That is, the sensor controller 31 according to this embodiment plays a role in realizing the above-mentioned A/B/C method. After controlling the multiple switches 51 so that the third state appears, the sensor controller 31 repeats the same control from the first state. The same is true for the other differential amplifiers 50, and the sensor controller 31 controls the switch circuit 30 so that the state of each switch 51 corresponding to the differential amplifier 50 _x and the state of each switch 51 corresponding to the other differential amplifiers 50 are synchronized with each other and become the same state.

33 to 35 respectively show the cases where the switch circuit 30 is in a first state, a second state, and a third state. In the first state shown in FIG. 33, the comb tooth portions PT _x-2 and PT _x are connected to the input terminals of the differential amplifier 50 _x , and one virtual loop coil is formed by these comb tooth portions PT _x-2 and PT _x and the portion of the base portion PB that connects them. The same is true for the other differential amplifiers 50. Similarly, in the second state shown in FIG. 34, the comb tooth portions PT _x-1 and PT _x+1 are connected to the input terminals of the differential amplifier 50 _x , and one virtual loop coil is formed by these comb tooth portions PT _x-1 and PT _x+1 and the portion of the base portion PB that connects them. In the third state shown in FIG. 35, the comb tooth portions PT _x and PT _x+2 are connected to the respective input terminals of the differential amplifier 50 _x , and one virtual loop coil is formed by these comb tooth portions PT _x and PT _x+2 and the portion of the base portion PB that connects them.

As can be seen from these, according to the A/B/C method, the virtual loop coil shifts in the x direction by a distance (second distance) that is shorter than the distance (first distance) between the two comb tooth portions PT that make up the virtual loop coil. The first distance is the distance between two adjacent comb tooth portions PT that sandwich one comb tooth portion PT, and the second distance is the distance between two adjacent comb tooth portions PT that do not sandwich another comb tooth portion PT.

Figure 36 is a plot of the maximum reception level of the pen signal PS obtained when the ODD/EVEN method is adopted and the maximum reception level of the pen signal PS obtained when the A/B/C method is adopted, for each distance (pen height) from the touch surface 3a to the tip of the electromagnetic induction pen 2. From the results in this figure, it can be seen that with the A/B/C method, the reception level of the pen signal PS is greater than with the ODD/EVEN method, regardless of the pen height.

Figure 32(b) is a diagram illustrating the distribution of the reception levels of the pen signal PS received when the tip of the electromagnetic induction pen 2 is at each position in the x direction for the position detection device 3 according to this embodiment (i.e., a position detection device 3 employing the A/B/C method). As is clear from a comparison with Figure 32(a), when the A/B/C method is employed, the reception level of the pen signal PS is higher both near the folding line FL and at positions away from the folding line FL than when the ODD/EVEN method is employed. Therefore, it can be said that the position detection system 1 according to this embodiment achieves an improvement in the reception level of the pen signal PS near the folding line FL.

As described above, according to the position detection system 1 of this embodiment, the A/B/C method is adopted as the position detection method for the electromagnetic induction pen 2, in which the virtual loop coil is shifted by a distance shorter than the distance between the two comb tooth portions PT that constitute the virtual loop coil, so that it is possible to increase the reception strength of the pen signal PS in the vicinity of the folding line FL of the foldable display.

In this embodiment, the distance (first distance) between the two comb tooth portions PT constituting the virtual loop coil is the distance between two adjacent comb tooth portions PT sandwiching one comb tooth portion PT, and the shift distance (second distance) of the virtual loop coil is the distance between two adjacent comb tooth portions PT without sandwiching another comb tooth portion PT. However, as long as the condition that the second distance is shorter than the first distance is satisfied, the specific values of the first distance and the second distance are not limited to the values described in this embodiment. For example, the first distance may be the distance between two adjacent comb tooth portions PT sandwiching two comb tooth portions PT, or the distance between two adjacent comb tooth portions PT sandwiching three comb tooth portions PT. In addition, the second distance may be the distance between two adjacent comb tooth portions PT sandwiching one comb tooth portion PT, or the distance between two adjacent comb tooth portions PT sandwiching two comb tooth portions PT.

37 is a diagram for explaining the process performed by the sensor controller 31 according to the modified embodiment. The sensor controller 31 according to the modified embodiment is configured to derive the position of the electromagnetic induction pen 2 using an added pen signal PS SUM obtained by adding a pen signal PS (hereinafter referred to as "pen signal _PS1 ") output from the differential amplifier _50x when the switch circuit 30 is in a first state, a pen signal PS (hereinafter referred to as "pen signal PS2") output from the differential amplifier _50x when the switch circuit 30 is in a second state, and a pen signal PS (hereinafter referred to as "pen signal PS3") output from the differential amplifier _50x when the switch circuit 30 is in a third state. The same applies to the other differential amplifiers 50.

As described above, when the switch circuit 30 is in the first state, one virtual loop coil is formed by the comb tooth portions PT _{x -2} , PT _x and the portions of the base portion PB that connect them, and the pen signal PS1 detected by this virtual loop coil is the sum of the pen signal PS (hereinafter referred to as "pen signals PS _x-2 , x-1") detected by the virtual loop coil formed by the comb tooth portions PT _{x -2} , PT x- ₁ and the portions of the base portion PB that connect them, and the pen signal PS (hereinafter referred to as "pen signal PS x-1, _x ") detected by the virtual loop coil formed by the comb tooth portions PT _x-1 , _{PT x} and the portions of the base portion PB that connect them. The same is true when the switch circuit 30 is in the second or third state, where the pen signal PS2 is the sum of the pen signal PS _x-1 , _x and the pen signal PS detected by a virtual loop coil formed by the comb tooth portions PT _x , PT _x+1 and the base portion PB that connects them (hereinafter referred to as "pen signal PS _x , _x+1 "), and the pen signal PS3 is the sum of the pen signal PS _x , _x+1 and the pen signal PS detected by a virtual loop coil formed by the comb tooth portions PT _x+1 , PT _x+2 and the base portion PB that connects them (hereinafter referred to as "pen signal PS _x+1 , _x+2 "). Therefore, the sum pen signal PS _SUM obtained by adding the pen signals PS1 to PS3 is expressed as PS _x-2 , _x-1 +2·PS _x-1 , _x +2·PS _x , _x+1 +PS _x+1 , _x+2 , as shown in Fig. 37. Since this form is none other than the form of the sum pen signal PS _SUM described in the sixth embodiment, the position detection system 1 according to this modified example has the effect of being able to detect the position of the electromagnetic induction pen 2 with high accuracy even if it is inclined with respect to the touch surface 3a, just like the position detection system 1 according to the sixth embodiment.

The above describes preferred embodiments of the present invention, but the present invention is not limited to these embodiments, and the present invention can be implemented in various forms without departing from the spirit of the invention.

1 Position detection system 2 Electromagnetic induction pen 3 Position detection device 3a Touch surface 30 Switch circuit 31 Sensor controller 32 Host processor 40, 50 Differential amplifiers 50 to 55, 60 to 62, S1, S2, T1, T2 Switch CCx Comb coils LCx, LCy Loop coil LE Linear electrode PB Base portion PS Pen signal PT Comb tooth portion T Terminal pre Precharge signal sel Selection signal

Claims (8)

an integrated circuit coupled to a receiving coil of an EMR sensor,
the receiving coil has a plurality of ends along a first edge of the touch surface;
the plurality of ends includes a first end and a second end;
a differential amplifier having a first input terminal and a second input terminal;
a group of switches that switch a connection destination of the first end between the second input terminal and any one of the second end, a ground terminal, and the first input terminal;
[0023] An integrated circuit including the receiving coil is composed of a plurality of loop coils including a first loop coil,
the first end is the other end of the first loop coil,
the switch group connects one end of the first loop coil to the first input terminal when the first end is connected to the second input terminal;
10. The integrated circuit of claim 1. the receiving coil is composed of a plurality of loop coils including a first loop coil,
the first end is the other end of the first loop coil,
When the first end is to be connected to the ground end, the switch group connects one end of the first loop coil to the first input terminal and connects the second input terminal to the ground end.
10. The integrated circuit of claim 1. the receiving coil is composed of a plurality of loop coils including a first loop coil and a second loop coil arranged adjacent to each other,
the first end is the other end of the first loop coil,
the second end is one end of the second loop coil,
When the first end is connected to the second end, the switch group connects one end of the first loop coil to the first input terminal and connects the other end of the second loop coil to the second input terminal.
10. The integrated circuit of claim 1. the receiving coil is a comb coil having a configuration in which a plurality of comb teeth are connected at one end to a base portion,
the plurality of ends are other ends of the plurality of comb tooth portions,
the group of switches switches between a first state in which the first end is connected to the second input terminal and a second state in which the first end is connected to the first input terminal in a time division manner;
10. The integrated circuit of claim 1. a plurality of said differential amplifiers including a first differential amplifier and a second differential amplifier;
the first state is a state in which the first end is connected to the second input terminal of the first differential amplifier and the second end is connected to the first input terminal of the second differential amplifier,
the second state is a state in which the first end is connected to the first input terminal of the first differential amplifier and the second end is connected to the second input terminal of the first differential amplifier,
6. The integrated circuit of claim 5. In the first state, a predetermined number of the ends including the first end are connected to the second input terminal of the first differential amplifier, and the predetermined number of the ends including the second end are connected to the first input terminal of the second differential amplifier,
In the second state, the predetermined number of ends including the first end and the second end are connected to the second input terminal of the first differential amplifier, and the predetermined number of ends excluding the first end and the second end are connected to the first input terminal of the second differential amplifier.
7. The integrated circuit of claim 6. an output terminal of the differential amplifier is connected to a sensor controller which detects the position of an electromagnetic induction pen based on a pen signal output from the differential amplifier;
6. An integrated circuit according to any one of claims 1 to 5.

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