Integrated circuit and sensor controller

Abstract

[Problem] The present invention provides an integrated circuit capable of switching the connection configuration between a reception-side coil of an EMR sensor and a sensor controller. [Solution] An integrated circuit according to the present invention is a switch circuit 30 connected to a plurality of loop coils LCx that are reception-side coils of an EMR sensor. The plurality of loop coils LCx include a plurality of end parts including end parts T12, T21 along a first side of a touch surface. The switch circuit 30 includes a differential amplifier 401 having a non-inverting input terminal and an inverting input terminal, and a group of switches for switching a connection destination of the end part T12 between the inverting input terminal of the differential amplifier 401 and one of the end part T21, a ground terminal, and the non-inverting input terminal of the differential amplifier 401.

Description

Integrated Circuit and Sensor Controller

[0001] The present invention relates to integrated circuits and sensor controllers, and more particularly to integrated circuits and sensor controllers for use with EMR sensors.

[0002] The electromagnetic induction method (EMR method) is known as one method for detecting the position of an electromagnetic induction pen on a panel surface of a tablet terminal or the like. An EMR-based position detection device includes 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 includes a transmitting coil consisting of multiple Tx coils arranged in the y direction and a receiving coil consisting of multiple Rx coils arranged in the x direction. The sensor controller sequentially transmits alternating magnetic fields from the multiple Tx coils and receives reflected signals (hereinafter referred to as "pen signals") transmitted by the electromagnetic induction pen from each Rx coil, thereby detecting the position of the electromagnetic induction pen (hereinafter referred to as the "pen position") and receiving data (hereinafter referred to as "pen data") transmitted by the electromagnetic induction pen. Patent documents 1 to 3 disclose examples of EMR sensors.

[0003] 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.

[0004] Japanese Patent No. 6698386 Japanese Patent Application Laid-Open No. 2018-185559 Japanese Patent Application Laid-Open No. 2022-117491

[0005] Incidentally, there are several methods for connecting each Rx coil that constitutes the receiving coil of an EMR sensor to the sensor controller. Specifically, there are 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 advantages, but conventional position detection devices are limited to one of these methods. Therefore, there was a need for a method that allows the connection method between each Rx coil and the sensor controller to be switched.

[0006] Therefore, one object of the present invention is to provide an integrated circuit capable of switching the connection method between the receiving coil of an EMR sensor and a sensor controller.

[0007] The inventors of the present application have also considered using, as the receiving coil of the EMR sensor, a coil (hereinafter referred to as a "comb coil") configured by connecting a single wire (hereinafter referred to as a "base") extending in the x direction to a number of wires (hereinafter referred to as "comb-shaped coils") extending in the y direction, instead of the multiple Rx coils described above. One end of each comb-shaped coil is connected to the base, and the other end is connected to the sensor controller. According to the inventors' research, the sensor controller receives pen signals by regarding the other ends of two adjacent comb-shaped coils as both ends of the Rx coil. This allows the sensor controller to receive pen signals as if the two comb-shaped coils and the portion of the base connecting them were forming an Rx coil, even though each of the two comb-shaped coils is actually connected to the other comb-shaped coil via the base. Therefore, using a comb-shaped coil also makes it possible to detect the pen position in the same way as using multiple Rx coils.

[0008] However, the comb coil has the problem that the accuracy of detecting the pen position is low because the configuration of the comb coil is equivalent to virtual loop coils formed by two adjacent comb teeth arranged at an interval in the x direction.

[0009] Therefore, another object of the present invention is to provide an integrated circuit that can improve the accuracy of detecting the pen position when an interdigital coil is used as the receiving coil of an EMR sensor.

[0010] Furthermore, since an alternating magnetic field appears in the Rx coil while the Tx coil is transmitting the alternating magnetic field, the sensor controller receives the pen signal at the Rx coil after stopping the transmission 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 transmission of the alternating magnetic field from the Tx coil has stopped, deteriorating the SNR (Signal to Noise Ratio) of the pen signal.

[0011] Therefore, it is yet another object of the present invention to provide an integrated circuit and a sensor controller that can improve the SNR of a pen signal.

[0012] The inventors of the present application have also considered using, as the receiving coil of the EMR sensor, a coil (hereinafter referred to as a "comb coil") configured by connecting a single wire (hereinafter referred to as a "base") extending in the x direction to a number of wires (hereinafter referred to as "comb-shaped coils") extending in the y direction, instead of the multiple Rx coils described above. One end of each comb-shaped coil is connected to the base, and the other end is connected to the sensor controller. According to the inventors' research, the sensor controller receives pen signals by regarding the other ends of two adjacent comb-shaped coils as both ends of the Rx coil. This allows the sensor controller to receive pen signals as if the two comb-shaped coils and the portion of the base connecting them were forming an Rx coil, even though each of the two comb-shaped coils is actually connected to the other comb-shaped coil via the base. Therefore, using a comb-shaped coil also makes it possible to detect the pen position in the same way as using multiple Rx coils.

[0013] However, the comb coil has the problem that the accuracy of detecting the pen position is low because the configuration of the comb coil is equivalent to virtual loop coils formed by two adjacent comb teeth arranged at an interval in the x direction.

[0014] Therefore, it is still another object of the present invention to provide an integrated circuit and a sensor controller that can improve the accuracy of detecting the pen position when an interdigital coil is used as the receiving coil of an EMR sensor.

[0015] Furthermore, when linear electrodes are used instead of Rx coils as in Patent Document 2, the sign of the pen signal is opposite between the linear electrodes on one side of the pen position in the x direction and the linear electrodes 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 becomes weak near the pen position.

[0016] Therefore, a further 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.

[0017] Furthermore, in conventional position detection devices, when the electromagnetic induction pen is tilted relative to the panel surface, the peak position of the pen signal received by the Rx coil may deviate from the actual position of the pen tip depending on the azimuth angle of the electromagnetic induction pen. This reduces the detection accuracy of the pen position, and so improvements were needed.

[0018] Therefore, a further 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.

[0019] In addition, in recent years, displays that can be bent (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 has been a problem in that the reception strength of the pen signal is weakened near the hinge parts, i.e., near the folding line.

[0020] Therefore, it is yet another object of the present invention 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.

[0021] An integrated circuit according to a 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, the integrated circuit including: a differential amplifier having a first input terminal and a second input terminal; and a group of switches that switch the connection destination of the first end between the second input terminal and any of the second end, a ground terminal, and the first input terminal.

[0022] An integrated circuit according to a second aspect of the present invention is the integrated circuit according to the first aspect, wherein the receiving coil is a comb coil having the plurality of 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.

[0023] An integrated circuit according to a third aspect of the present invention is an integrated circuit connected to an EMR sensor, wherein the receiving coil of the EMR sensor is composed of a plurality of first loop coils, and the integrated circuit includes a plurality of differential amplifiers each having a first input terminal and a second input terminal, a first wiring connecting one end of each of the plurality of first loop coils to the first input terminal of the corresponding differential amplifier, a second wiring connecting 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.

[0024] A sensor controller according to a third aspect of the present invention is a sensor controller connected to the EMR sensor via the integrated circuit according to the first aspect of the present invention, wherein 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 formed by a plurality of second loop coils each extend in a second direction and are arranged side by side in the first direction, and the integrated circuit has two states: a first state in which one end and the other end of a 2n-1th (n is a natural number) first loop coil from one end side in the second direction among 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 a 2n-1th first loop coil from one end side in the second direction are disconnected from the first input terminal and the second input terminal of the corresponding differential amplifier; and a second state in which the 2n-1th (n is a natural number) first loop coil from one end side in the second direction among 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 configured to be switchable between a first state in which one end and the other end of a 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 a (2n-1)th first loop coil are disconnected from the first input terminal and the second input terminal of the corresponding differential amplifier, and the switch circuit is configured to be switchable between a first state in which one end and the other end of a (2n-1)th first loop coil are connected to the first input terminal and the second input terminal of the corresponding differential amplifier, and the switch circuit is configured to be switchable between a first state in which one end and the other end of a (2n-1)th first loop coil are connected to the first input terminal and the second input terminal of the corresponding differential amplifier, and the switch circuit is configured to be switchable between a first state in which one end and the other end of a (2n-1)th first loop coil are connected to the first input terminal and the second input terminal of the corresponding differential amplifier, and the switch circuit is configured to be switchable between a first state in which one end and the other end of a (2n-1)th

[0025] An integrated circuit according to a fourth aspect of the present invention is an integrated circuit connected to an EMR sensor, wherein the receiving coil of the EMR sensor is 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, and the integrated circuit 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 a 2n-1th (n is a natural number) comb tooth portion from one end side in the second direction among the plurality of comb tooth portions and the other end of a 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, respectively; and a second state in which the other end of the 2nth comb tooth portion from one end side in the second direction among the plurality of comb tooth portions and the other end of a 2n+1th comb tooth portion from one end side in the second direction among the plurality of comb tooth portions are connected to the first input terminal and the second input terminal of the same differential amplifier, respectively.

[0026] A sensor controller according to a 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, wherein the transmitting coil of the EMR sensor is composed of a plurality of loop coils each extending in the second direction and arranged side by side in the first direction, and wherein an alternating magnetic field is transmitted from the EMR sensor by sequentially passing a current through each of the plurality of loop coils, and the switch circuit is set to the first state when the current is passed through the 2m-1th loop coil (m is a natural number) from one end side in the first direction among the plurality of loop coils, and the switch circuit is set to the second state when the current is passed through the 2mth loop coil from one end side in the first direction among the plurality of loop coils, thereby receiving pen signals output from each of the plurality of differential amplifiers.

[0027] An integrated circuit according to a fifth aspect of the present invention is an integrated circuit connected to an EMR sensor, wherein the receiving coil of the EMR sensor is composed of a plurality of linear electrodes each extending in a first direction and arranged in a line 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 wiring connecting the end of the 2n-kth (k is an odd natural number, and 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.

[0028] A sensor controller according to a 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, wherein the transmitting coil of the EMR sensor is composed of a plurality of loop coils each extending in the second direction and arranged side by side in the first direction, and an alternating magnetic field is transmitted from the EMR sensor by sequentially passing a current through each of the plurality of loop coils, and the switch circuit is set to the first state when the current is passed 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, 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 pen signals output from each of the plurality of differential amplifiers.

[0029] 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 weightings, a pen signal received at a first loop coil among the plurality of loop coils and a pen signal received at each of one or more other loop coils among the plurality of loop coils that are located in the vicinity of the first loop coil, and derives the position of the electromagnetic induction pen using an added pen signal obtained by the addition.

[0030] An integrated circuit according to a seventh aspect of the present invention is an integrated circuit connected to an EMR sensor, wherein a receiving coil of the EMR sensor is 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, and the integrated circuit includes a receiving circuit for receiving 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, and the plurality of comb-tooth portions are connected at one end to a base portion extending in a second direction intersecting the first direction. the selection circuit performs the selection so that a first state in which first and third comb tooth portions are selected from the plurality of comb tooth portions and a second state in which second and fourth comb tooth portions are selected from the plurality of comb tooth portions appear in sequence, a distance between the first comb tooth portion and the third comb tooth portion and a distance between the second comb tooth portion and the fourth comb tooth portion are both a first distance, and a distance between the first comb tooth portion and the second comb tooth portion is a second distance shorter than the first distance.

[0031] A sensor controller according to a 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 performing 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 is connected to the EMR sensor via an integrated circuit that controls the selection circuit so that the first state, the second state, and the third state appear in sequence.

[0032] 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 the group of switches.

[0033] According to the second aspect of the present invention, reception of a pen signal in the first state and reception of a pen signal in the second state can be performed in a time-division manner, and therefore the spacing between the virtual loop coils can be effectively made zero, thereby improving the detection accuracy of the pen position when a comb coil is used as the receiving coil of the EMR sensor.

[0034] According to the third aspect of the present invention, each first loop coil can be precharged by turning on the first switch element, thereby eliminating the influence of the alternating magnetic field sent from the transmitting coil from the receiving coil and improving the SNR of the pen signal.

[0035] According to the fourth aspect of the present invention, reception of a pen signal in the first state and reception of a pen signal in the second state can be performed in a time-division manner, and therefore the spacing between the virtual loop coils can be effectively made zero, thereby improving the detection accuracy of the pen position when a comb coil is used as the receiving coil of the EMR sensor.

[0036] 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.

[0037] 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 weightings, so that even if the electromagnetic induction pen is tilted relative to the panel surface, its position can be detected with high accuracy.

[0038] 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 tooth portions that make up the virtual loop coil, thereby making it possible to increase the reception strength of the pen signal near the folding line of the foldable display.

[0039] 6 is a diagram showing a configuration of a position detection system 1 according to a first embodiment of the present invention. FIG. 6 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. FIG. 6 is a diagram showing an internal configuration of the switch circuit 30 shown in FIG. 1 and a state of the switch circuit 30 in a single-ended system. FIG. 6 is a diagram showing an internal configuration of the switch circuit 30 shown in FIG. 1 and a first state of the switch circuit 30 in a bundled input system. FIG. 6 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 system. FIG. 6 is a diagram showing a configuration of a position detection system 1 according to a second embodiment of the present invention. FIG. 6 is a diagram showing an internal configuration and a first state of the switch circuit 30 shown in FIG. 6. FIG. 6 is a diagram showing an internal configuration and a second state of the switch circuit 30 shown in FIG. 6. FIG. 6 is a diagram showing a first state of the switch circuit 30 according to a first modified example of the second embodiment of the present invention. FIG. 6 is a diagram showing a second state of the switch circuit 30 according to a first modified example of the second embodiment of the present invention. FIG. 6 is a diagram showing a first state of the switch circuit 30 according to a second modified example of the second embodiment of the present invention. FIG. 6 is a diagram showing a second state of the switch circuit 30 according to a second modified example of the second embodiment of the present invention. FIG. 6 is a diagram showing an internal configuration of a switch circuit 30 according to a third embodiment of the present invention. 16 is a diagram showing waveforms of signals etc. relating to the control of switch elements S1, S2, T1, T2 shown in FIG. 13. FIG. 17 is a diagram showing a method of driving an EMR sensor according to a modified example of the third embodiment of the present invention. FIG. 18 is a diagram showing the configuration of a position detection system 1 according to a fourth embodiment of the present invention. FIG. 19 is a diagram showing the internal configuration and a first state of the switch circuit 30 shown in FIG. 16. FIG. 20 is a diagram showing the internal configuration and a second state of the switch circuit 30 shown in FIG. 16. FIG. 21 is a diagram showing a method of driving an EMR sensor according to a modified example of the fourth embodiment of the present invention. FIG. 22 is a diagram showing the configuration of a position detection system 1 according to a fifth embodiment of the present invention. FIG. 23 is a diagram showing the internal configuration and a first state of the switch circuit 30 shown in FIG. 20. FIG. 24 is a diagram showing the internal configuration and a second state of the switch circuit 30 shown in FIG. 20. FIG. 25 is a diagram showing simulation results of the reception strength of a pen signal. FIG. 26 is a diagram showing the internal configuration and a first state of the switch circuit 30 included in the position detection system 1 according to a first modified example of the fifth embodiment of the present invention.27 is a diagram showing the internal configuration and 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. FIG. 28 is a diagram showing a method for driving an EMR sensor according to a second modified example of the fifth embodiment of the present invention. FIG. 29 is a diagram showing problems when receiving a pen signal using a position detection system 1 according to a third embodiment of the present invention. FIG. 29 is a diagram explaining the azimuth angle θ and tilt angle φ used in FIG. 27. (a) is a diagram explaining the processing performed by a sensor controller 31 according to a sixth embodiment of the present invention, and (b) is a diagram showing a virtual loop coil VLCx obtained by the addition shown in (a). Added pen signal PS when the pen tip of the electromagnetic induction pen 2 is at a position where the x coordinate = 0 mm. ＳＵＭ 10A is a diagram showing the reception levels of the EMR sensor 33 included in the position detection device 3 according to the seventh embodiment of the present invention. (a) is a plan view of the EMR sensor 33 included in the position detection device 3 according to the seventh embodiment of the present invention, and (b) is a cross-sectional view of the EMR sensor 33 corresponding to the line A-A shown in (a). (a) is a diagram showing the distribution of the reception levels of the pen signal PS received when the pen tip of the electromagnetic induction pen 2 is at each position in the x direction, assuming that the odd / even system is adopted in the position detection device 3 according to the seventh embodiment of the present invention. (b) is a diagram showing the distribution of the reception levels of the pen signal PS received when the pen tip of the electromagnetic induction pen 2 is at each position in the x direction, assuming that the odd / even system is adopted in the position detection device 3 according to the seventh embodiment of the present invention (i.e., the position detection device 3 adopting the A / B / C system). (c) is a diagram showing the internal configuration and a first state of the switch circuit 30 according to the seventh embodiment of the present invention. (d) is a diagram showing the internal configuration and a second state of the switch circuit 30 according to the seventh embodiment of the present invention. 13 is a diagram plotting the maximum value of the reception level of the pen signal PS observed when the ODD / EVEN method is adopted and the maximum value of the 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 3 a to the pen tip of the electromagnetic induction pen 2. FIG. 14 is a diagram illustrating the processing performed by the sensor controller 31 according to a modified example of the seventh embodiment of the present invention.

[0040] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0041] 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 include 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 include an internal resonant circuit that includes a coil and a capacitor.

[0042] The position detection device 3 is a device configured to be able to detect the position of an electromagnetic induction pen 2 within a touch surface 3a (panel surface) using the EMR system. Within the touch surface 3a, a plurality of loop coils LCx (Rx coils) that are receiving coils of the EMR sensor and a plurality of loop coils LCy (Tx coils) that are transmitting coils of the EMR sensor are arranged. The position detection device 3 also includes 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 laptop computer whose display surface doubles as the touch surface 3a, but the position detection device 3 may also be configured using a digitizer or the like that does not have a display surface.

[0043] The illustrated x and y directions are directions within the touch surface 3a and are perpendicular to each other. The multiple loop coils LCx are each formed to extend in the y direction and are arranged side by side in the x direction. Meanwhile, 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 each of the loop coils LCx and LCy may be arranged to overlap with 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.

[0044] The switch circuit 30 is a group of switches (switch group) configured with a plurality of switches for switching 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.

[0045] 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 using the EMR method. The sensor controller 31 controls the connection state of the loop coils LCx and LCy by controlling the switch circuit 30, thereby supplying AC current to each of the multiple loop coils LCy in sequence and receiving a pen signal generated in each loop coil LCx each time. 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.

[0046] More specifically, when the sensor controller 31 starts supplying AC current to any of the loop coils LCy, that loop coil LCy starts to emit an AC magnetic field. When the coil of the electromagnetic induction pen 2 enters this AC magnetic field, an electromotive force is generated across both ends, charging the capacitor of the electromagnetic induction pen 2. When the sensor controller 31 subsequently 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).

[0047] Here, the electromagnetic induction pen 2 is configured to be able to transmit pen data, such as a writing 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.

[0048] The pen signal sent from the coil of the electromagnetic induction pen 2 is received by each loop coil LCx. The sensor controller 31 receives the pen signal at each loop coil LCx each time while changing the loop coil LCy that supplies AC current under the control of the switch circuit 30, thereby acquiring the pen signal strength for each combination of loop coil LCy and loop coil LCx. The sensor controller 31 then derives the pen signal strength distribution within the touch surface 3a based on the acquired strengths, and detects the apex of the distribution 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 detected position and acquired data as described above to the host processor 32 each time.

[0049] 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 performed when the pen position has not yet been detected, and the sensor controller 31 performs the above-mentioned series of processes using all of the loop coils LCx and LCy. This enables the sensor controller 31 to detect the electromagnetic induction pen 2 over the entire touch surface 3a.

[0050] 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-described 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.

[0051] The sensor controller 31 is also configured to select one of the above-described differential, single-ended, and combined input methods for receiving pen signals from each loop coil LCx. This selection may be made during the manufacturing process of the sensor controller 31 or the position detection device 3, or may be made by a user during use. For example, the sensor controller 31 may select the combined input method when the pen pressure value included in the most recently received pen data indicates that the electromagnetic induction pen 2 is hovering (the pen tip is not in contact with the touch surface 3 a), and may select the differential or single-ended method when the pen is touching (the pen tip is in contact with the touch surface 3 a). The sensor controller 31 controls the switch circuit 30 based on the selection result, thereby achieving reception of pen signals using the selected method. The specific content of the control of the switch circuit 30 by the sensor controller 31 will be described in detail later with reference to FIGS. 2 to 5.

[0052] The host processor 32 is a central processing unit of the position detection device 3 that executes programs read from a memory (not shown) to execute the operating system and various applications of the position detection device 3. The processes executed by the host processor 32 in accordance with the programs include various processes performed using the pen position and pen data supplied from the sensor controller 31. These various processes include, for example, moving a cursor displayed on the display surface and generating stroke data that indicates 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.

[0053] 2 to 5 are diagrams showing the internal configuration of the switch circuit 30. These diagrams show only the parts of the internal configuration of the switch circuit 30 that are related to receiving a pen signal in each loop coil LCx. Below, with reference to these diagrams, 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 system, single-ended system, and bundled input system will be described in detail.

[0054] For ease of explanation, two loop coils LCx are shown in FIGS. １ , LCx ２ However, it goes without saying that the actual position detection device 3 has many more loop coils LCx. １ Both ends of １１ , T １２ The loop coil LCx ２ Both ends of ２１ , T ２２ It is called.

[0055] 2, the switch circuit 30 includes a plurality of differential amplifiers 40 and a group of switches each including a plurality of switches 50 to 55. A 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 provided for each loop coil LCx. The switch 55 is also a single-pole double-throw switch, and is provided for every two adjacent loop coils LCx. In the following description, the loop coils LCx will be referred to as needed. １ The subscript "1" is added to the right of the symbol to indicate the configuration corresponding to the loop coil LCx ２ The subscript "2" is added to the right of the symbol to indicate the configuration corresponding to the loop coil LCx １ , LCx ２ In some cases, the subscript "12" is added to the right of the reference numeral to distinguish each configuration from the other configurations.

[0056] 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 with respect to the ground potential. The output terminal of each differential amplifier 40 supplies a pen signal to the sensor controller 31.

[0057] switch 50 １ The common terminal of １１ , one selection terminal is connected to the ground terminal, and the other selection terminal is connected to the node n １１ The switch 51 １ The common terminal of １２ , one selection terminal is connected to the ground terminal, and the other selection terminal is connected to the node n １２ The switch 52 １ The common terminal of １２ One selection terminal is connected to node n １１ and the other selection terminal is connected to the switch 53 １ The switch 53 is connected to the second selection terminal of the １ The common terminal of the differential amplifier 40 １and the first selection terminal is connected to the non-inverting input terminal of node n １１ and the third selection terminal is connected to the ground terminal. １ The common terminal of the differential amplifier 40 １ and the first selection terminal is connected to the inverting input terminal of node n １２ The second selection terminal is connected to a node n ２１ and the third selection terminal is connected to the ground terminal.

[0058] switch 50 ２ The common terminal of ２１ , one selection terminal is connected to the ground terminal, and the other selection terminal is connected to the node n ２１ The switch 51 ２ The common terminal of ２２ , one selection terminal is connected to the ground terminal, and the other selection terminal is connected to the node n ２２ The switch 52 ２ The common terminal of ２２ One selection terminal is connected to node n ２１ and the other selection terminal is connected to the switch 53 ２ The switch 53 is connected to the second selection terminal of the ２ The common terminal of the differential amplifier 40 ２ and the first selection terminal is connected to the non-inverting input terminal of node n ２１ and the third selection terminal is connected to the ground terminal. ２ The common terminal of the differential amplifier 40 ２ and the first selection terminal is connected to the inverting input terminal of node n ２２ The third selection terminal is connected to the ground terminal. ２ The second selection terminal of the loop coil LCx １ On the other side of the loop coil LCx ２ The other selection terminal of the switch 50 corresponding to the other loop coil LCx adjacent to the other loop coil LCx is connected to the other selection terminal of the switch 50 corresponding to the other loop coil LCx adjacent to the other loop coil LCx.

[0059] The common terminal of the switch 55 is the end T １２ , and one selection terminal is connected to the end T ２１The other select terminal of switch 55 is connected to nothing, and therefore switch 55 may be a single-pole, single-throw switch.

[0060] With the above configuration, the switch circuit 30 １２ (first end) is connected to the differential amplifier 40 １ The inverting input terminal (second input terminal) of the terminal T ２１ (second end), a ground end, and a differential amplifier 40 １ The sensor controller 31 controls this switching to receive the pen signal in the differential, single-ended, or bundled input modes. This will be explained in detail below.

[0061] 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 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 differential amplifier 40 １ Regarding the non-inverting input terminal, the loop coil LCx １ End T of １１ The inverting input terminal is connected to the loop coil LCx １ End T of １２ The differential system can remove common mode noise from the pen signal received by each loop coil LCx, and also has the effect of increasing the signal strength of the pen signal received by each loop coil LCx compared to the single-ended system described below.

[0062] 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 the other selection terminal of each switch 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. The other end of each loop coil LCx is connected to the ground terminal. For example, the differential amplifier 40 １ The non-inverting input terminal is the loop coil LCx １ End T of １１ The inverting input terminal is connected to the ground terminal, and the loop coil LCx １ End T of １２ is connected to the ground terminal. The single-ended system has the advantage that the sensor controller 31 can receive the pen signal even if the differential amplifier 40 is not connected to both ends of the loop coil LCx.

[0063] 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 Fig. 4 and the second state shown in Fig. 5 are realized in a time-division manner for each loop coil LCy.

[0064] 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 explain this in more detail with reference to FIG. 4, the sensor controller 31 sets the switch 50 １ , 51 ２ The other selection terminal is connected to the common terminal, and the switch 52 ２ , 55１２ One of the selection terminals is connected to the common terminal, and the switch 53 １ , the first selection terminal is connected to the common terminal, and the switch 54 １ , the second selection terminal is connected to the common terminal, while the switch 50 ２ , 51 １ , 52 １ , 53 ２ , 54 ２ As a result, as shown by the broken lines in FIG. １ , LCx ２ are connected in series to the differential amplifier 40 １ The same applies to the other loop coils LCx (not shown).

[0065] 5, in the second state, compared to the first state, the combination of two loop coils LCx connected in series to each differential amplifier 40 is shifted by one in the x direction. In addition to this shift, the control of the switch circuit 30 performed by the sensor controller 31 to achieve the second state is the same as in the first state.

[0066] According to the bundled input method, since the two loop coils LCx are connected in series, the inductance is doubled, resulting in an effect of correspondingly increasing the reception strength of the pen signal. However, since the first state shown in FIG. 4 and the second state shown in FIG. 5 must be switched in a time-division manner, it takes twice as long to receive the pen signal as compared to the differential or single-ended 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-ended method when the pen is touching. This allows adaptive connection method switching to be realized. During hovering, when the distance between the coil in the electromagnetic induction pen 2 and the touch surface 3 a is large and the reception strength of the pen signal tends to be low, the bundled input method is used to increase the reception strength of the pen signal. During pen touch, when a sufficiently high reception strength is obtained, the differential or single-ended method is used to shorten the time required to receive the pen signal.

[0067] As described above, according to the position detection system 1 of this embodiment, it is possible to switch the connection method between the receiving coil of the EMR sensor and the sensor controller 31 among the differential method, single-ended method, and bundled input method by controlling the group of switches in the switch circuit 30 from the sensor controller 31. Therefore, the sensor controller 31 can detect the pen position and acquire pen data while making the most of the advantages of each method.

[0068] 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, instead of multiple loop coils LCx, an interdigital coil CCx consisting of a base portion PB and multiple interdigital portions PT is used as the receiving coil of the EMR sensor. Accordingly, the internal configuration of the switch circuit 30 and 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, the position detection system 1 according to this embodiment is similar to the position detection system 1 according to the first embodiment, and the following description will focus on the differences from the position detection system 1 according to the first embodiment.

[0069] 6, the comb coil CCx is configured by connecting a base portion PB, which is a single wire extending in the x direction, to a plurality 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 portion PB, and the other end is connected to the switch circuit 30. The other end of each comb tooth portion PT is arranged along a side E1, which is one side of the rectangular touch surface 3a.

[0070] 7 and 8 are diagrams showing the internal configuration of the switch circuit 30 according to this embodiment. These diagrams show only the portion of the internal configuration of the switch circuit 30 that is related to reception of a pen signal by the comb coil CCx. Hereinafter, with reference to these diagrams, a method in which the sensor controller 31 receives a pen signal using the comb coil CCx will be described in detail.

[0071] For ease of explanation, four comb-tooth portions PT are shown in FIGS. 7 and 8. １ ~PT ４ However, it goes without saying that an actual comb coil CCx has many more comb tooth portions PT. １ ~PT ４ The other end of each (the end opposite to the end connected to the base portion PB) is connected to the end T １ ~T ４ It is called.

[0072] 7, the switch circuit 30 according to this embodiment is configured to include a plurality of differential amplifiers 40 and a switch group each 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 provided for every two comb tooth portions 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, the comb tooth portions PT are referred to as "comb tooth portions PT" as needed. １ The subscript "1" is added to the right of the symbol to indicate the configuration corresponding to the comb tooth portion PT ２ The subscript "2" is added to the right of the symbol to indicate the configuration corresponding to the comb tooth portion PT ３ The subscript "3" is added to the right of the symbol to indicate the configuration corresponding to the comb tooth portion PT ４ The subscript "4" is added to the right of the symbol to indicate the configuration corresponding to the comb tooth portion PT １ , P.T. ２ The subscript "12" is added to the right side of the reference numeral to the configuration corresponding to both the comb tooth portion PT ３ , P.T. ４ In some cases, the subscript "34" is added to the right of the reference numeral to distinguish each component from the other components.

[0073] Switch 60 １ The common terminal of １ , one selection terminal is connected to the ground terminal, and the other selection terminal is connected to the node n １ The switch 60 ２ ~60 ４ The same applies to switch 60 ２ The common terminal of ２ , one selection terminal is connected to the ground terminal, and the other selection terminal is connected to the node n ２ and configure the switch 60 ３ The common terminal of ３ , one selection terminal is connected to the ground terminal, and the other selection terminal is connected to the node n ３ and configure the switch 60 ４ The common terminal of ４, one selection terminal is connected to the ground terminal, and the other selection terminal is connected to the node n ４ Configure.

[0074] Switch 61 １２ The common terminal of ２ One selection terminal is connected to node n １ and the other selection terminal is connected to the switch 62 １ The switch 62 is connected to the second selection terminal of the １ The common terminal of the differential amplifier 40 １２ and the first selection terminal is connected to the non-inverting input terminal of node n １ and the third selection terminal is connected to the ground terminal. ２ The common terminal of the differential amplifier 40 １２ and the first selection terminal is connected to the inverting input terminal of node n ２ and the second selection terminal is connected to node n ３ and the third selection terminal is connected to the ground terminal.

[0075] Switch 61 ３４ The common terminal of ４ One selection terminal is connected to node n ３ and the other selection terminal is connected to the switch 62 ３ The switch 62 is connected to the second selection terminal of the ３ The common terminal of the differential amplifier 40 ３４ and the first selection terminal is connected to the non-inverting input terminal of node n ３ and the third selection terminal is connected to the ground terminal. ４ The common terminal of the differential amplifier 40 ３４ and the first selection terminal is connected to the inverting input terminal of node n ４ The third selection terminal is connected to the ground terminal. ４ The second selection terminal of the comb tooth portion PT ３ On the opposite side of the comb tooth part PT ４ The other selection terminal of the switch 60 corresponding to the other adjacent comb tooth portion PT is connected to the other selection terminal of the switch 60 corresponding to the other adjacent comb tooth portion PT.

[0076] With the above configuration, the switch circuit 30 ２(first end) is connected to the differential amplifier 40 １２ the inverting input terminal (second input terminal) of the differential amplifier 40 １ The sensor controller 31 controls this switching to switch between the non-inverting input terminal (first input terminal) of the end T ２ differential amplifier 40 １２ a first state in which the inverting input terminal of the terminal T ２ differential amplifier 40 １２ The first state is connected to the non-inverting input terminal of the first input terminal, and the second state is connected to the non-inverting input terminal of the second input terminal of the first input terminal.

[0077] 7 shows the first state of the switch circuit 30. As shown in the figure, in the first state, the comb-tooth portion PT １ End T of １ is the differential amplifier 40 １２ is connected to the non-inverting input terminal of the comb tooth portion PT ２ End T of ２ is the differential amplifier 40 １２ Also, the comb tooth portion PT ３ End T of ３ is the differential amplifier 40 ３４ is connected to the non-inverting input terminal of the comb tooth portion PT ４ End T of ４ is the differential amplifier 40 ３４ 7. The same applies to the other comb tooth portions PT not shown. As a result, as shown by the dashed lines in FIG. 7, one virtual loop coil is formed by the portion connecting two adjacent comb tooth portions PT and the base portion PB. Hereinafter, the virtual loop coil formed in this manner will be referred to as a "virtual loop coil." Although each virtual loop coil is connected via the base portion PB, research by the inventors of the present application has revealed that this does not substantially affect the reception characteristics of the pen signal.

[0078] 8 shows the second state of the switch circuit 30. As shown in the figure, in the second state, the comb-tooth portion PT ２ End T of ２ is the differential amplifier 40 １２ is connected to the non-inverting input terminal of the comb tooth portion PT３ End T of ３ is the differential amplifier 40 １２ is connected to the inverting input terminal of the comb tooth portion PT. １ End T of １ is the comb tooth portion PT ２ On the opposite side of the comb tooth part PT １ and the ends of the other comb tooth portions PT adjacent to the differential amplifier 40 ３４ On the other side of the differential amplifier 40 １２ Similarly, the comb tooth portion PT ４ End T of ４ is the comb tooth portion PT ３ On the opposite side of the comb tooth part PT ４ and the ends of the other comb tooth portions PT adjacent to the differential amplifier 40 ３４ 8. The same applies to the other comb tooth portions PT not shown. As a result, as in the case of FIG. 7, one virtual loop coil is formed by the portion connecting two adjacent comb tooth portions PT and the base portion PB, as shown by the dashed lines in FIG. 8, but the combination of two comb tooth portions PT that make up 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, the virtual loop coils are also connected via the base portion PB, but as in the first state, this does not substantially affect the reception characteristics of the pen signal.

[0079] If a pen signal is received 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 becomes large, 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, thereby making it possible to reduce the spacing between the virtual loop coils 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.

[0080] As described above, according to the position detection system 1 of this embodiment, reception of a pen signal in the first state and reception of a 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 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.

[0081] In the present 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 employing such connections will be described below.

[0082] 9 and 10 are diagrams showing a first state and a second state, respectively, of the switch circuit 30 according to a first modified example of the present 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 these figures omit illustration of the detailed configuration within the switch circuit 30, and only show the connection state between each comb-tooth portion PT and the differential amplifier 40. The switch circuit 30 according to this modified example has one differential amplifier 40 for every four comb-tooth portions PT.

[0083] The sensor controller 31 according to this modification first selects four comb tooth portions PT from each of the comb tooth portions PT constituting the comb coil CCx, starting from one end in the x direction, as one set of four comb tooth portions PT. In the example of FIG. 9, １ ~PT ４ , comb tooth part PT ５ ~PT ８ Each of the four comb tooth portions PT constitutes one set. The sensor controller 31 commonly 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, and commonly connects the other two to the inverting input terminal of the corresponding differential amplifier 40. As a result, as shown in FIG. 9, a state (first state) is formed in which four adjacent comb tooth portions PT are connected to one differential amplifier 40. This state is called the first state. ４ End T of ４A predetermined number (two in this case) of ends including the first end are connected to the inverting input terminal of the first differential amplifier 40, and the comb tooth portion PT ５ End T of ５ The predetermined number of ends including the second end are connected to the non-inverting input terminal of the second differential amplifier 40 .

[0084] Next, the sensor controller 31 shifts the four comb-tooth portions PT constituting each set one by one. FIG. 10 shows the state after this shift from the state shown in FIG. 9. As shown in the figure, in this case, the comb-tooth portions PT ２ ~PT ５ , comb tooth part PT ６ ~PT ７ 9, the sensor controller 31 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) is formed in which four adjacent comb tooth portions PT are connected to one differential amplifier 40. This state is called the comb tooth portion PT. ４ End T of ４ (first end) and comb tooth portion PT ５ End T of ５ The predetermined number of ends including the second end are connected to the inverting input terminal of the first differential amplifier 40, and the other predetermined number of ends of the comb tooth portions PT are connected to the non-inverting input terminal of the second differential amplifier 40.

[0085] The sensor controller 31 according to this modification performs a similar shift three times to form sets 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 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 and second states described above. The sensor controller 31 according to this modification receives pen signals output from each differential amplifier 40 in each of the four states thus formed. Then, the received pen signals are used to detect the pen position and acquire pen data.

[0086] 11 and 12 are diagrams showing a first state and a second state, respectively, of a switch circuit 30 according to a second modified example of the present embodiment. This modified example is an example in which four comb tooth portions PT are connected to one input terminal of a 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.

[0087] The sensor controller 31 according to this modification first selects eight comb tooth portions PT from each of the comb tooth portions PT constituting the comb coil CCx, starting from one end in the x direction, as one set of eight comb tooth portions PT. In the example of FIG. 11 , １ ~PT ８ The sensor controller 31 commonly connects four of the eight 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, and commonly connects the remaining four to the inverting input terminal of the corresponding differential amplifier 40. As a result, as shown in FIG. 11, a state (first state) is formed in which eight adjacent comb tooth portions PT are connected to one differential amplifier 40. This state is called the first state. ８ End T of ８A predetermined number (four in this case) of ends including the first end are connected to the inverting input terminal of the first differential amplifier 40, and the comb tooth portion PT ９ End T of ９ The predetermined number of ends including the second end are connected to the non-inverting input terminal of the second differential amplifier 40 .

[0088] Next, the sensor controller 31 shifts the eight comb-tooth portions PT constituting each set one by one. FIG. 12 shows the state after this shift from the state shown in FIG. 11. As shown in the figure, in this case, the comb-tooth portions PT ２ ~PT １０ 11, the sensor controller 31 commonly connects four of the eight 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, and commonly connects the remaining four to the inverting input terminal of the corresponding differential amplifier 40. As a result, as shown in FIG. 12, a state (second state) is formed in which eight adjacent comb tooth portions PT are connected to one differential amplifier 40. This state is called the comb tooth portion PT. ８ End T of ８ (first end) and comb tooth portion PT ９ End T of ９ The predetermined number of ends including the second end are connected to the inverting input terminal of the first differential amplifier 40, and the other predetermined number of ends of the comb tooth portions PT are connected to the non-inverting input terminal of the second differential amplifier 40.

[0089] The sensor controller 31 according to this modification performs the same shift seven times to form eight sets 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 in the x direction to the non-inverting input terminal of the corresponding differential amplifier 40, and commonly connecting the remaining 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 and second states described above. The sensor controller 31 according to this modification receives pen signals output from each differential amplifier 40 in each of the eight states thus formed. The received pen signals are then used to detect the pen position and acquire pen data.

[0090] As shown in the two modified examples described above, the position detection system 1 according to this embodiment can receive pen signals in a time-division manner in a plurality of connection states, even when a plurality of comb-tooth portions PT are connected to a single input terminal of the differential amplifier 40. This makes it possible to improve the accuracy of pen position detection when the comb coil CCx is used as the receiving coil of the EMR sensor. Furthermore, according to these modified examples, since a plurality of comb-tooth portions PT are connected to a single input terminal of the differential amplifier 40, it is possible to increase the reception strength of the pen signal compared to this embodiment.

[0091] 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 the same as 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.

[0092] 13 is a diagram showing the internal configuration of the switch circuit 30 according to this embodiment. This diagram shows only the configuration related to the loop coil LCx. Also shown in this diagram are one each of the loop coils LCx and LCy, and the sensor controller 31.

[0093] As shown in FIG. 13, the switch circuit 30 according to the present embodiment includes, for each loop coil LCx, a differential amplifier 40, lines L1 and L2, and a switch group including switch elements S1, S2, T1, and T2.

[0094] 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 with respect to the ground potential. The output signal of the differential amplifier 40 is supplied to the sensor controller 31 as a pen signal PS.

[0095] 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 midway along the 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.

[0096] The wiring L2 connects the other end of the loop coil LCx to the corresponding inverting input terminal of the differential amplifier 40. The switch element T2 is a single-pole, single-throw switch provided midway along the wiring L2. When the 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 the 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.

[0097] 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 an 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 the 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.

[0098] The switch elements S1 and S2 are controlled by a precharge signal pre generated by the sensor controller 31. The switch elements T1 and T2 are controlled 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.

[0099] 14 is a diagram showing waveforms of signals related to the control of switch elements S1, S2, T1, and T2. The voltage PE shown in the diagram 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 diagram. The sensor controller 31 continues to emit this alternating magnetic field from time t1 until time t3, a predetermined time Ta later.

[0100] 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 just before that, and then returns the precharge signal pre to an inactive state. By performing this series of processes, it is possible to precharge each loop coil LCx, thereby eliminating the influence of the alternating magnetic field sent out from the loop coil LCy from the loop coil LCx and improving the SNR of the pen signal PS.

[0101] Here, 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 precharging in a shorter time. That is, because the loop coil LCx has a time constant as described above, supplying the power supply potential Vref to the loop coil LCx does not immediately bring the entire loop coil LCx to the power supply potential Vref. Instead, over a certain period of time, the loop coil LCx gradually transitions to the power supply potential Vref, starting with the portion closest to the power supply wiring. 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; it is also possible to supply the power supply potential Vref to only one end of the loop coil LCx.

[0102] Returning to FIG. 14 , the sensor controller 31 stops transmitting the alternating magnetic field at time t3, and simultaneously 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 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 acquire 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.

[0103] As described above, according to the switch circuit 30 and 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 loop coil LCy on the transmitting side can be eliminated from each loop coil LCx on the receiving side, and the SNR of the pen signal PS can be improved.

[0104] FIG. 15 is a diagram showing a method for driving an EMR sensor according to a modification of this embodiment. The sensor controller 31 according to this modification differs from the sensor controller 31 according to this embodiment in that, when performing the global scan described above, pen signals are 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 description will focus on this difference. Note that, for simplicity's sake, FIG. 15 shows only six loop coils LCx and LCy, but the same applies when the EMR sensor includes more loop coils LCx and LCy.

[0105] 15(a) shows a first reception mode of the pen signal, and FIG. 15(b) shows a second reception mode of the pen signal. The sensor controller 31 according to this modification detects the pen position by alternately switching between the first reception mode and the second reception mode.

[0106] As a premise, the switch circuit 30 according to this modified example is configured so that the switch elements T1 and 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 side in the x direction among the multiple loop coils LCx and the 2nth (even numbered) loop coil LCx from one end side 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 switchable 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 plurality of 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 plurality of 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, in response to control from the sensor controller 31.

[0107] 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 plurality of 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 plurality of loop coils LCy, thereby receiving pen signals output from each of the plurality of differential amplifiers 40. According to this process, detection of the pen position is performed centered around the hatched area in FIG. 15(a).

[0108] 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 plurality of 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 plurality of loop coils LCy, thereby receiving pen signals output from each of the plurality of differential amplifiers 40. According to this process, pen position detection is performed centered on the hatched portion in FIG. 15(b). Comparing with FIG. 15(a), it can be seen that hatching has been added to the portion that was not hatched in FIG. 15(a).

[0109] According to this modification, 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 set to the first state whenever an AC current is passed through any of the loop coils LCy, and when, in the second reception mode, the switch circuit 30 is set to the second state whenever an AC current is passed through any of the loop coils LCy. This is due to the fact that, as can be seen from Figures 15(a) and 15(b), hatched areas (i.e., areas where the pen signal intensity is acquired) are arranged above, below, left, and right of non-hatched areas (i.e., areas where the pen signal intensity is not acquired) (i.e., arranged in a grid pattern), making it possible to accurately derive the pen signal intensity distribution in all directions.

[0110] Furthermore, according to this modification, 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 arranged in the sensor controller 31 for receiving pen signals.

[0111] 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, instead of multiple loop coils LCx, an interdigital coil CCx consisting of a base portion PB and multiple interdigital portions PT is used as the receiving coil of the EMR sensor. Accordingly, the internal configuration of the switch circuit 30 and 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, the position detection system 1 according to this embodiment is similar to the position detection system 1 according to the third embodiment, and the following description will focus on the differences from the position detection system 1 according to the third embodiment.

[0112] 16, the comb coil CCx is configured such that a base portion PB, which is a single wire extending in the x direction, is connected to a plurality 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 portion PB, and the other end is connected to the switch circuit 30.

[0113] 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 at 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 is referred to as the comb-tooth portion PT. ｘ to distinguish it from the other comb-tooth portions PT.

[0114] 17 and 18, the switch circuit 30 according to this 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 the same as those of the differential amplifier 40 described in the third embodiment. In the following description, the differential amplifiers 50 that are provided for the comb-tooth portions PT are referred to as the differential amplifiers 40. ｘ－１ , P.T. ｘ The differential amplifier 50 is provided corresponding to ｘ to distinguish it from other differential amplifiers 50.

[0115] 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. ｘ－１ The first selection terminal of the switch 51 connected to 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 The common terminal is connected to the inverting input terminal of the comb tooth portion PT ｘ The first selection terminal of the switch 51 connected to the differential amplifier 50 ｘ 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 This is connected to the non-inverting input terminal of the

[0116] The switch 52 is a single-pole, single-throw switch that is provided between a power supply wiring that is supplied with a predetermined power supply potential Vref (e.g., ground potential) and a wiring 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.

[0117] The switches 51 and 52 are controlled by the sensor controller 31. The control of the switch 52 is performed to precharge the comb tooth portion PT, and is performed at the same timing as the control of the switches S1 and S2 described with reference to Fig. 14. Furthermore, the control of the switch 51, which keeps the common terminal connected to the second selection terminal (open end), is also performed with the same timing as the timing of turning off the 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.

[0118] In controlling the switch 51, the sensor controller 31 controls the timing of connecting the common terminal to the first selection terminal or the third selection terminal 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 described in detail below.

[0119] First, the states of the switch circuit 30 will be described. The switch circuit 30 is configured to be switchable, under the control of the sensor controller 31, between a first state (the state shown in FIG. 17 ) in which the third selection terminal of each switch 51 is selected, and a second state (the state shown in FIG. 18 ) in which the first selection terminal of each switch 51 is selected. 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 and the other end of the 2nth (even-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 the 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 connecting them (the circled portion in FIG. 17 ). 18 , the other end of the 2n-th (even-numbered) comb tooth portion PT and the other end of the 2n+1-th (odd-numbered) comb tooth portion PT from one end side in the x direction among the plurality of comb tooth portions PT are connected to the inverting input terminal and the non-inverting input terminal of the same differential amplifier 50. As a result, a virtual loop coil is formed by the 2n-th comb tooth portion PT, the 2n+1-th comb tooth portion PT, and the portion of the base portion PB that connects them (the portion circled in FIG. 18 ).

[0120] For each loop coil LCy, the sensor controller 31 starts supplying AC current to that loop coil LCy, stops the supply, switches the switch circuit 30 to the first state, and receives a pen signal. Then, it starts supplying AC current to the same loop coil LCy again, stops the supply, and switches the switch circuit 30 to the second state, and receives a pen signal. This process is common to both global and local scans. This effectively reduces the spacing between virtual loop coils formed by the comb coils CCx to zero in both global and local scans, thereby improving the accuracy of pen position detection when the comb coils CCx are used as the receiving coils of the EMR sensor.

[0121] As described above, the switch circuit 30 and sensor controller 31 according to this embodiment enable reception of a pen signal in the first state and reception of a pen signal in the second state to 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.

[0122] Furthermore, 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, thereby improving the SNR of the pen signal PS.

[0123] FIG. 19 is a diagram showing a method of driving an EMR sensor according to a modification of the present embodiment. The sensor controller 31 according to this modification differs from the sensor controller 31 according to the present embodiment in that, when performing one global scan, the sensor controller 31 receives only one of the following for each loop coil LCy: receiving a pen signal using the switch circuit 30 in the first state, or receiving a pen signal using the switch circuit 30 in the second state, rather than both. The following description will focus on this difference. Note that, for simplicity's sake, FIG. 19 shows only six loop coils LCy and seven comb-teeth portions PT, but the same applies when the EMR sensor includes more loop coils LCy and comb-teeth portions PT.

[0124] 19(a) shows a first reception mode of the pen signal, and FIG. 19(b) shows a second reception mode of the pen signal. The sensor controller 31 of this modification detects the pen position by alternately performing a global scan in the first reception mode and a global scan in the second reception mode.

[0125] In the first reception mode, 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 plurality of 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 plurality of loop coils LCy, thereby receiving pen signals output from each of the plurality of differential amplifiers 50. According to this process, detection of the pen position is performed centered around the hatched portion in FIG. 19(a).

[0126] 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 plurality of 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 plurality of loop coils LCy, thereby receiving pen signals output from each of the plurality of differential amplifiers 50. According to this process, pen position detection is performed centered on the hatched portion in FIG. 19(b). Comparing with FIG. 19(a), it can be seen that hatching has been added to the portion that was not hatched in FIG. 19(a).

[0127] According to this modification, it is possible to complete one global scan in half the time compared to the present embodiment. Although the accuracy of the pen position detected in one global scan is lower than in the present embodiment, because the hatched areas in each global scan are arranged in a grid pattern similar to that of the modification of the third embodiment described with reference to Figure 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 whenever an AC current is passed through any of the loop coils LCy in the first reception mode, and when the switch circuit 30 is in the second state whenever an AC current is passed through any of the loop coils LCy in the second reception mode.

[0128] 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, a plurality of linear electrodes LE each extending in the y direction and arranged side by side in the x direction are used as the receiving coil of the EMR sensor. In other respects, the position detection system 1 according to this embodiment is the same as the position detection system 1 according to the fourth embodiment, and the following description will focus on the differences from the position detection system 1 according to the fourth embodiment.

[0129] The configuration of the EMR sensor according to this embodiment is essentially the same as that of the comb coil CCx of the fourth embodiment, except that the base portion PB is removed. FIGS. 21 and 22 are diagrams showing the internal configuration of the switch circuit 30 according to this embodiment. Comparing these diagrams with FIGS. 17 and 18 will be understood. The internal configuration of the switch circuit 30 is the same as that of the switch circuit 30 according to the fourth embodiment, except that the connection destination is the linear electrodes 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. FIG. 21 shows the first state, and FIG. 22 shows the second state. The pen signal reception process performed by the sensor controller 31 using this control may also be the same as that of the fourth embodiment.

[0130] In this embodiment, because each linear electrode LE is electrically isolated, a virtual loop coil, as described in the fourth embodiment, is not formed whether the switch circuit 30 is in the first state or the 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 within the electromagnetic induction pen 2 is weaker. Therefore, the reception strength of the pen signal received by each linear electrode LE is weaker than in the third and fourth embodiments. However, the configuration of the switch circuit 30 according to this embodiment has the effect of increasing the reception strength of the pen signal, particularly near 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.

[0131] 23 is a diagram showing the simulation results of the reception strength of a pen signal. Graph G1 in the figure shows the simulation results of the reception strength of a 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 a pen signal received by the sensor controller 31 when using a position detection device that supplies the pen signals received by each linear electrode LE to the sensor controller 31 independently without using a differential amplifier 50. The horizontal axis in the figure indicates the serial number of the linear electrodes LE. The position of each point on the horizontal axis of graph G1 corresponds to the midpoint in the x direction between two linear electrodes LE connected to the same differential amplifier 50. The same applies to graph G2, which will be described later.

[0132] 23 shows an example in which the pen tip of the electromagnetic induction pen 2 is located between the tenth linear electrode LE and the eleventh linear electrode LE. Looking first at graph G0, it can be seen that the signs of the reception strength of the pen signal received by the tenth and lower linear electrodes LE are opposite to those of the reception strength of the pen signal received by the eleventh and lower linear electrodes LE, and that the reception strength of the pen signal becomes weak to almost zero in the vicinity of the pen position.

[0133] 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 pen signals of opposite signs reinforce each other via 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 received strength of the pen signal near the pen position.

[0134] As described above, according to the position detection device 3 of this embodiment, 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.

[0135] 24 and 25 are diagrams showing the internal configuration of the switch circuit 30 according to a first modified example of the present embodiment. FIG. 24 shows a first state, and FIG. 25 shows a second state. As can be seen by comparing FIGS. 24 and 25 with FIGS. 21 and 22, the switch circuit 30 according to this modified example has the same differential amplifier 50. ｘ The switch circuit 30 differs from the switch circuit 30 of the present embodiment in that the two linear electrodes LE connected to the sensor 10 are not directly adjacent to each other, but are adjacent to each other with the two linear electrodes LE sandwiched therebetween. In other respects, the switch circuit 30 is the same as the switch circuit 30 of the present embodiment, and the content of the control of the switch circuit 30 by the sensor controller 31 is also the same as that of the present embodiment.

[0136] The switch circuit 30 according to this modification is configured to be switchable 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 in the x direction and the end of the 2nth linear electrode LE from the plurality of linear electrodes LE are connected to the inverting input terminal and the non-inverting input terminal of the same differential amplifier 50, respectively, and a second state in which the end of the 2nth linear electrode LE from one end in the x direction and the end of the 2n+kth linear electrode LE from the plurality of linear electrodes LE are connected to the inverting input terminal and the non-inverting input terminal of the same differential amplifier 50, respectively. In this modification, k=3, but if k=1, the switch circuit 30 described in the present embodiment can be obtained. Generally speaking, k may be any odd natural number, and the value of k that maximizes the received strength of the pen signal near the pen position may be selected.

[0137] 23 shows the simulation results of the reception strength of the pen signal received by the sensor controller 31 according to this modification. As can be seen from a comparison with graph G1, the switch circuit 30 according to this modification 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 modification can 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.

[0138] FIG. 26 is a diagram illustrating a method for driving an EMR sensor according to a second modification of the present embodiment. The sensor controller 31 according to this modification differs from the sensor controller 31 according to the present embodiment in that, when performing one global scan, the sensor controller 31 receives only one of the following for each loop coil LCy: receiving a pen signal using the switch circuit 30 in the first state, or receiving a pen signal using the switch circuit 30 in the second state, rather than both. The following description will focus on this difference. Note that, for simplicity's sake, FIG. 26 shows only six loop coils LCy and seven linear electrodes LE, but the same applies when the EMR sensor includes more loop coils LCy and linear electrodes LE.

[0139] 26(a) shows a first reception mode of the pen signal, and FIG. 26(b) shows a second reception mode of the pen signal. The sensor controller 31 of this modification detects the pen position by alternately performing a global scan in the first reception mode and a global scan in the second reception mode.

[0140] In the first reception mode, 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 plurality of 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 plurality of loop coils LCy, thereby receiving pen signals output from each of the plurality of differential amplifiers 50. According to this process, detection of the pen position is performed centered around the hatched portion in Figure 26(a).

[0141] 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 plurality of 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 plurality of loop coils LCy, thereby receiving pen signals output from each of the plurality of differential amplifiers 50. According to this processing, pen position detection is performed centered on the hatched portion in FIG. 26(b). Comparing with FIG. 26(a), it can be seen that hatching has been added to the portion that was not hatched in FIG. 26(a).

[0142] According to this modification, it is possible to complete one global scan in half the time compared to the present embodiment. Although the accuracy of the pen position detected in one global scan is lower than in the present embodiment, because the hatched areas in each global scan are arranged in a grid pattern similar to that of the modification of the third embodiment described with reference to Figure 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 whenever an AC current is passed through any of the loop coils LCy in the first reception mode, and when the switch circuit 30 is in the second state whenever an AC current is passed through any of the loop coils LCy in the second reception mode.

[0143] 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 the same as 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.

[0144] Fig. 27 is a diagram showing a problem that occurs when a pen signal is received using the position detection system 1 according to the third embodiment. Fig. 28 is a diagram for explaining the azimuth angle θ and tilt angle φ used in Fig. 27. Before describing 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 described below with reference to these figures.

[0145] 28 , three angles are defined for the electromagnetic induction pen 2: an azimuth angle θ, a tilt angle φ, and a rotation angle ψ. The azimuth angle θ is an angle that indicates the direction in which the pen tip of the electromagnetic induction pen 2 in contact with the touch surface 3a is pointing, 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 its pen axis. The problem solved by the position detection system 1 according to this embodiment relates to the azimuth angle θ and the tilt angle φ out of these angles.

[0146] 27 shows the reception level of the pen signal PS received by the loop coil LCx corresponding to each x coordinate when the pen 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°) or (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. Furthermore, when (θ, φ) = (180°, 60°), the peak position of the reception level of the pen signal PS is shifted to the positive side. As described above, in the position detection system 1 according to the third embodiment, the peak position of the reception level of the pen signal PS may be shifted from the actual position of the pen tip depending on the combination of the azimuth angle θ and tilt angle φ of the electromagnetic induction pen 2. The position detection system 1 according to this embodiment aims to improve the deterioration in the detection accuracy of the pen position caused by such a shift.

[0147] 29A is a diagram illustrating 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 performs the process of detecting the n-th loop coil LCx ｎ The pen signal PS received at ｎ and loop coil LCx ｎ and the pen signal PS received by each of the one or more loop coils LCx in the vicinity of the loop coil LCx, with different weightings, to obtain an added pen signal PS ＳＵＭ The position of the electromagnetic induction pen 2 is derived using the above.

[0148] Specifically, the sensor controller 31 according to this embodiment is configured to: ｎ－２ ~ n+2th loop coil LCx ｎ＋２ The pen signal PS received at the five loop coils LCx is ｎ－２ ~PS ｎ＋２ The pen signal PS received at the three loop coils LCx located at the center of the five loop coils LCx isｎ－１ ~PS ｎ＋１ The weighting of the pen signal received at the other two loop coils LCx is ｎ－２ , P.S. ｎ＋２ The above addition is performed so that the weighting of PS ＳＵＭ =PS ｎ－２ +2 PS ｎ－１ +2 PS ｎ +2 PS ｎ＋１ +PS ｎ＋２ This becomes:

[0149] 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 added pen signal PS ＳＵＭ becomes a signal equivalent to the pen signal PS received by a double-wound coil in which the width of the inner wiring is X1 (the width of three loop coils LCx) and the distance between the outer wiring and the inner wiring is X2 (the width of one loop coil LCx).

[0150] FIG. 30 shows the summed pen signal PS when the pen tip of the electromagnetic induction pen 2 is at the x coordinate = 0 mm position. ＳＵＭ 27, the figure shows the reception level of the added pen signal PS obtained at the loop coil LCx corresponding to each x coordinate when the azimuth angle θ and the tilt angle φ are (θ, φ) = (0°, 0°), (0°, 60°), (180°, 60°), and (90°, 60°), respectively. ＳＵＭ 10 shows the reception level of the signal (a signal obtained by weighting and adding the pen signals PS received by the five loop coils LCx centered around that loop coil LCx).

[0151] As shown in FIG. 30, the additive pen signal PS ＳＵＭ The peak position of the reception level of the added pen signal PS 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 added pen signal PS ＳＵＭHowever, since the shape is symmetrical, this depression does not deteriorate the detection accuracy of the pen position. Therefore, according to the position detection system 1 of this embodiment, even if the electromagnetic induction pen 2 is tilted with respect to the touch surface 3 a, it can be said that the position can be detected with high accuracy.

[0152] As described above, according to the position detection system 1 of this embodiment, the pen signals PS received by the plurality of loop coils LCx are added with different weights to produce the added pen signal PS ＳＵＭ Since the position of the electromagnetic induction pen 2 is derived using the above, even if the electromagnetic induction pen 2 is tilted with respect to the touch surface 3a, the position can be detected with high accuracy.

[0153] 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. Since the position detection system 1 according to this embodiment is otherwise similar to the position detection system 1 according to the fourth embodiment, the following description will focus on the differences from the position detection system 1 according to the fourth embodiment.

[0154] In the following description, the position detection method of the electromagnetic induction pen 2 realized by the switch circuit 30 and sensor controller 31 according to the fourth embodiment may be referred to as the "odd / even method." "odd" and "even" correspond to the first state and second state of the switch circuit 30 described in the fourth embodiment, respectively. The position detection method of the electromagnetic induction pen 2 realized by the switch circuit 30 and 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 a first state to a third state, and "A," "B," and "C" correspond to these first to third states, respectively.

[0155] Fig. 31(a) is a plan view of the EMR sensor 33 included in the position detection device 3 according to this embodiment, and Fig. 31(b) is a cross-sectional view of the EMR sensor 33 corresponding to line A-A shown in Fig. 31(a). As shown in these figures, the EMR sensor 33 is configured to include a substrate 34 on which a receiving coil and a transmitting coil are formed, and a magnetic material sheet 35 made of a magnetic material. The magnetic material sheet 35 is a member that functions as a magnetic path for the magnetic field generated by the coils in the substrate 34, and is arranged to cover the entire one surface of the substrate 34 (the surface opposite the touch surface 3a).

[0156] If the display (not shown) included in the position detection device 3 is a foldable display, it is naturally necessary to configure the EMR sensor 33 to be foldable as well. The illustrated component 36 is a conductive hinge component required for this purpose, and is disposed between the substrate 34 and the magnetic sheet 35 along the folding line FL.

[0157] FIG. 32( a ) is a diagram illustrating the distribution of the reception levels of the pen signal PS received when the pen tip of the electromagnetic induction pen 2 is at each position in the x direction, assuming that the odd / even system is adopted in the position detection device 3 according to this embodiment. As shown in the figure, with the odd / even system, the reception level of the pen signal PS drops significantly near the folding line FL. This is due to the magnetic field being disturbed by the hinge part 36 shown in FIGS. 31( a ) and 31 ( b ). With the reception level shown in FIG. 32( a ), it is difficult to derive the pen position near the folding line FL, and therefore, it has been 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 system instead of the odd / even system.

[0158] 33 to 35 are diagrams showing the internal configuration of the switch circuit 30 according to this embodiment. As with FIGS. 17 and 18, these diagrams show only the parts of the internal configuration of the switch circuit 30 that are related to receiving pen signals at 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 is referred to as the comb-tooth portion PT. ｘ to distinguish it from the other comb-tooth portions PT.

[0159] 33 to 35, the switch circuit 30 according to this embodiment has one differential amplifier 50 for every three comb tooth portions PT. In the following description, ｘ－１ , P.T. ｘ , P.T. ｘ＋１ The differential amplifier 50 is provided corresponding to ｘ to distinguish it from other differential amplifiers 50.

[0160] The common terminal of the switch 51 according to this embodiment is connected to the other end of the corresponding comb tooth portion PT. ｘ The first selection terminal of the switch 51 connected to the differential amplifier 50 ｘ 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 common terminal is connected to the non-inverting input terminal of the comb tooth portion PT. ｘ－１ The first selection terminal of the switch 51 connected to the differential amplifier 50 ｘ 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－２ The common terminal is connected to the non-inverting input terminal of the comb tooth portion PT. ｘ＋１ The first selection terminal of the switch 51 connected to 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 above configuration is called a differential amplifier 50. ｘ To summarize from the side, the differential amplifier 50 ｘ The inverting input terminal of ｘ－２ , P.T. ｘ－１ , P.T.ｘ The first selection terminals of the three switches 51 corresponding to the differential amplifiers 50 are connected in common. ｘ The non-inverting input terminal of ｘ , P.T. ｘ＋１ , P.T. ｘ＋２ The third selection terminals of the three switches 51 corresponding to the three switches 51 are connected in common.

[0161] The switch circuit 30 according to this embodiment has five corresponding comb tooth portions PT (differential amplifier 50 ｘ If so, comb tooth portion PT ｘ－２ , P.T. ｘ－１ , P.T. ｘ , P.T. ｘ＋１ , P.T. ｘ＋２ The sensor controller 31 selects two of the five comb tooth portions PT under the control of the sensor controller 31, and functions as a selection circuit that connects the two selected comb tooth portions PT to a differential amplifier 50 as a receiving circuit.

[0162] The sensor controller 31 according to this embodiment includes, for example, a differential amplifier 50 ｘ Regarding this, the comb tooth portion PT ｘ－２ , P.T. ｘ A first state in which the comb tooth portion PT is selected ｘ－１ , P.T. ｘ＋１ A second state in which the comb tooth portion PT is selected ｘ , P.T. ｘ＋２ The sensor controller 31 controls the switch circuit 30 so that the first state, the second state, and the third state, which selects the first state, appear in sequence. That is, the sensor controller 31 according to this embodiment fulfills the role of realizing the A / B / C method described above. After controlling the plurality of switches 51 so that the third state appears, the sensor controller 31 repeats the same control from the first state. The same applies to the other differential amplifiers 50, and the sensor controller 31 controls the differential amplifiers 50 in the same way. ｘ The switch circuit 30 is controlled so that the state of each switch 51 corresponding to the differential amplifier 50 is synchronized with the state of each switch 51 corresponding to the other differential amplifier 50 and becomes the same state.

[0163] 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 differential amplifier 50 ｘ Each input terminal of the comb tooth part PT ｘ－２ , P.T. ｘ are connected, and these comb tooth portions PT ｘ－２ , P.T. ｘ and the portion of the base portion PB that connects them together form one virtual loop coil. The same applies to the other differential amplifiers 50. Similarly, in the second state shown in FIG. 34, the differential amplifiers 50 ｘ Each input terminal of the comb tooth part PT ｘ－１ , P.T. ｘ＋１ are connected, and these comb tooth portions PT ｘ－１ , P.T. ｘ＋１ 35, the differential amplifier 50 ｘ Each input terminal of the comb tooth part PT ｘ , P.T. ｘ＋２ are connected, and these comb tooth portions PT ｘ , P.T. ｘ＋２ and the portion of the base portion PB that connects them together form one virtual loop coil.

[0164] As can be seen from these facts, according to the A / B / C method, the virtual loop coil is shifted 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.

[0165] 36 is a diagram plotting the maximum value of the reception level of the pen signal PS obtained when the ODD / EVEN method is employed and the maximum value of the reception level of the pen signal PS obtained when the A / B / C method is employed for each distance (pen height) from the touch surface 3 a to the pen tip of the electromagnetic induction pen 2. From the results in this figure, it can be seen that the reception level of the pen signal PS is greater when the A / B / C method is employed than when the ODD / EVEN method is employed, regardless of the pen height.

[0166] 32(b) is a diagram illustrating the distribution of the reception level of the pen signal PS received when the pen 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., the position detection device 3 employing the A / B / C system). As is clear from a comparison with FIG. 32(a), when the A / B / C system is employed, the reception level of the pen signal PS is higher both near the bending line FL and at positions away from the bending line FL than when the odd / even system 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 bending line FL.

[0167] 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.

[0168] In the present 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 therebetween, 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 therebetween. However, as long as the second distance is shorter than the first distance, the specific values ​​of the first distance and the second distance are not limited to the values ​​described in the present embodiment. For example, the first distance may be the distance between two adjacent comb-tooth portions PT sandwiching two comb-tooth portions PT therebetween, or the distance between two adjacent comb-tooth portions PT sandwiching three comb-tooth portions PT therebetween. Furthermore, the second distance may be the distance between two adjacent comb-tooth portions PT sandwiching one comb-tooth portion PT therebetween, or the distance between two adjacent comb-tooth portions PT sandwiching two comb-tooth portions PT therebetween.

[0169] 37 is a diagram illustrating the process performed by the sensor controller 31 according to a modification of the present embodiment. The sensor controller 31 according to this modification performs the process of switching the differential amplifier 50 when the switch circuit 30 is in the first state. ｘ When the switch circuit 30 is in the second state, the differential amplifier 50 outputs a pen signal PS (hereinafter referred to as "pen signal PS1"). ｘ When the switch circuit 30 is in the third state, the differential amplifier 50 outputs a pen signal PS (hereinafter referred to as "pen signal PS2"). ｘ and the pen signal PS (hereinafter referred to as "pen signal PS3") output from ＳＵＭ The other differential amplifiers 50 are configured to derive the position of the electromagnetic induction pen 2 using the above.

[0170] As described above, when the switch circuit 30 is in the first state, the comb tooth portion PT ｘ－２ , P.T. ｘ and the portion of the base portion PB that connects them together form a virtual loop coil, and the pen signal PS1 detected by this virtual loop coil is ｘ－２ , P.T. ｘ－１and the part of the base PB that connects them, a pen signal PS (hereinafter referred to as "pen signal PS") is detected by a virtual loop coil. ｘ－２ , ｘ－１ ") and the comb tooth part PT ｘ－１ , P.T. ｘ and the part of the base PB that connects them, a pen signal PS (hereinafter referred to as "pen signal PS") is detected by a virtual loop coil. ｘ－１ , ｘ The same applies when the switch circuit 30 is in the second state or the third state, and the pen signal PS2 is the sum of the pen signal PS ｘ－１ , ｘ and the comb tooth portion PT ｘ , P.T. ｘ＋１ and the part of the base PB that connects them, a pen signal PS (hereinafter referred to as "pen signal PS") is detected by a virtual loop coil. ｘ , ｘ＋１ The pen signal PS3 is the sum of the pen signal PS ｘ , ｘ＋１ and the comb tooth portion PT ｘ＋１ , P.T. ｘ＋２ and the part of the base PB that connects them, a pen signal PS (hereinafter referred to as "pen signal PS") is detected by a virtual loop coil. ｘ＋１ , ｘ＋２ Therefore, the added pen signal PS1 to PS3 is ＳＵＭ As shown in FIG. ｘ－２ , ｘ－１ +2 PS ｘ－１ , ｘ +2 PS ｘ , ｘ＋１ +PS ｘ＋１ , ｘ＋２ This form is expressed as follows: ＳＵＭ Therefore, the position detection system 1 according to this modified example has the same effect as the position detection system 1 according to the sixth embodiment, that is, even if the electromagnetic induction pen 2 is tilted with respect to the touch surface 3 a, the position can be detected with high accuracy.

[0171] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and it goes without saying that the present invention can be embodied in various forms without departing from the spirit of the present invention.

[0172] REFERENCE SIGNS LIST 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 coil LCx, LCy Loop coil LE Linear electrode PB Base PS Pen signal PT Comb tooth portion T Terminal pre Precharge signal sel Selection signal

Claims

1. 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 that switch the connection of the first end between the second input terminal and either the second end, ground, or the first input terminal.

2. The integrated circuit of claim 1, wherein 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, and the group of switches connects one end of the first loop coil to the first input terminal when the first end is connected to the second input terminal.

3. The integrated circuit according to claim 1, wherein 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, and the group of switches, when connecting the first end to the ground end, connects one end of the first loop coil to the first input terminal and connects the second input terminal to the ground end.

4. The integrated circuit of claim 1, wherein 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, and when the first end is connected to the second end, the group of switches 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.

5. The integrated circuit according to claim 1, wherein the receiving coil is a comb coil having a configuration in which one end of each of a plurality of comb tooth portions is connected to a base portion, the plurality of ends are the other ends of each of the plurality of comb tooth portions, 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.

6. The integrated circuit of claim 5, comprising a plurality of said differential amplifiers including a first differential amplifier and a second differential amplifier, said first state being a state in which said first end is connected to said second input terminal of said first differential amplifier and said second end is connected to said first input terminal of said second differential amplifier, and said second state being a state in which said first end is connected to said first input terminal of said first differential amplifier and said second end is connected to said second input terminal of said first differential amplifier.

7. The integrated circuit of claim 6, wherein 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; and in the second state, the predetermined number of the 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 the ends excluding the first end and the second end are connected to the first input terminal of the second differential amplifier.

8. The integrated circuit according to any one of claims 1 to 5, wherein 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.

9. An integrated circuit connected to an EMR sensor, wherein a receiving coil of the EMR sensor is composed of a plurality of first loop coils, the integrated circuit comprising: a plurality of differential amplifiers each having a first input terminal and a second input terminal; first wiring connecting one end of each of the plurality of first loop coils to the first input terminal of the corresponding differential amplifier; second wiring connecting 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.

10. The integrated circuit according to claim 9, further comprising: a second switch element provided between said power supply wiring and said second wiring.

11. A sensor controller connected to the EMR sensor via the integrated circuit according to claim 1 or 2, wherein 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 the transmitting coil of the EMR sensor is constituted by a plurality of second loop coils each extend in the second direction and are arranged side by side in the first direction, the integrated circuit further includes a switch circuit configured to be capable of switching between a first state in which one end and the other end of a 2n-1th (n is a natural number) first loop coil from one end side in the second direction among 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 one end and the other end of a 2nth first loop coil from one end side in the second direction among 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 2n-1th first loop coil are disconnected from the first input terminal and the second input terminal of the corresponding differential amplifier; a sensor controller which receives pen signals output from each of the plurality of differential amplifiers by setting the switch circuit to the first state when the current is to flow 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 setting the switch circuit to the second state when the current is to flow through the loop coil that is 2mth from one end side in the first direction among the plurality of loop coils.

12. A sensor controller as claimed in claim 11, configured to alternately execute a first reception mode in which the switch circuit is set to the first state when the current is passed through the second loop coil that is 2m-1th 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 2m-1th from one end side in the first direction among the plurality of second loop coils, thereby receiving a pen signal output from each of the plurality of differential amplifiers; and a second reception mode in which the switch circuit is set to the second state when the current is passed through the second loop coil that is 2m-1th from one end side in the first direction among the plurality of second loop coils, and the switch circuit is set to the first state when the current is passed through the loop coil that is 2m-1th 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.

13. An integrated circuit connected to an EMR sensor, comprising: a receiving coil of the EMR sensor which is 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; 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, respectively, 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, respectively.

14. A sensor controller connected to the EMR sensor via the integrated circuit of claim 13, wherein the transmitting 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, an alternating magnetic field is transmitted from the EMR sensor by sequentially passing a current through each of the plurality of loop coils, and the switch circuit is set to the first state when the current is passed 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, 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 pen signals output from each of the plurality of differential amplifiers.

15. A sensor controller as claimed in claim 14, configured to alternately execute a first reception mode in which the switch circuit is set to the first state when the current is passed through the loop coil that is 2m-1th from one end side in the first direction among the plurality of loop coils, and the switch circuit is set to the second state when the current is passed through the loop coil that is 2m-1th 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; and a second reception mode in which the switch circuit is set to the second state when the current is passed through the loop coil that is 2m-1th from one end side in the first direction among the plurality of loop coils, and the switch circuit is set to the first state when the current is passed through the loop coil that is 2m-1th 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.

16. An integrated circuit connected to an EMR sensor, wherein the receiving coil of the EMR sensor is composed of a plurality of linear electrodes each extending in a first direction and arranged side by side 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 a 2n-kth (k is an odd natural number, and 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.

17. The integrated circuit according to claim 16, further comprising a switch circuit configured to be able to switch between a first state in which an end of the 2n-kth linear electrode and an end of the 2nth linear electrode from one end side in the second direction among the plurality of linear electrodes are connected to the first input terminal and the second input terminal of the same differential amplifier, and a second state in which an end of the 2nth linear electrode and an end of the 2n+kth linear electrode from one end side in the second direction among the plurality of linear electrodes are connected to the first input terminal and the second input terminal of the same differential amplifier, respectively.

18. A sensor controller connected to the EMR sensor via the integrated circuit of claim 17, wherein the transmitting 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, an alternating magnetic field is transmitted from the EMR sensor by sequentially passing a current through each of the plurality of loop coils, and the switch circuit is set to the first state when the current is passed 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, 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 pen signals output from each of the plurality of differential amplifiers.

19. A sensor controller as claimed in claim 18, configured to alternately execute a first reception mode in which the switch circuit is set to the first state when the current is passed through the loop coil that is 2m-1th from one end side in the first direction among the plurality of loop coils, and the switch circuit is set to the second state when the current is passed through the loop coil that is 2m-1th 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; and a second reception mode in which the switch circuit is set to the second state when the current is passed through the loop coil that is 2m-1th from one end side in the first direction among the plurality of loop coils, and the switch circuit is set to the first state when the current is passed through the loop coil that is 2m-1th 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.

20. A sensor controller connected to an EMR sensor having a plurality of loop coils, the sensor controller adding, with different weighting, a pen signal received at a first loop coil among the plurality of loop coils and a pen signal received at each of one or more other loop coils located in the vicinity of the first loop coil among the plurality of loop coils, and deriving a position of an electromagnetic induction pen using an added pen signal obtained by the addition.

21. The sensor controller of claim 20, wherein the plurality of loop coils include second and third loop coils each adjacent to the first loop coil, a fourth loop coil adjacent to the second loop coil on the opposite side of the first loop coil, and a fifth loop coil adjacent to the third loop coil on the opposite side of the first loop coil, and wherein a weighting in the addition of the pen signals received at the first to third loop coils is twice a weighting in the addition of the pen signals received at the fourth and fifth loop coils.

22. An integrated circuit connected to an EMR sensor, wherein the receiving coil of the EMR sensor is a comb coil having a configuration in which a plurality of comb-tooth portions extending in a first direction are connected at one end to a base portion extending in a second direction intersecting the first direction, the integrated circuit 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 two selected comb-tooth portions to the receiving circuit, the plurality of comb-tooth portions having first to fourth comb-tooth portions in order from one side of the second direction, the selection circuit performing the selection so that a first state in which the first and third comb-tooth portions are selected and a second state in which the second and fourth comb-tooth portions are selected appear in order, a distance between the first comb-tooth portion and the third comb-tooth portion and a distance between the second comb-tooth portion and the fourth comb-tooth portion are both a first distance, and a distance between the first comb-tooth portion and the second comb-tooth portion is a second distance shorter than the first distance.

23. The integrated circuit of claim 22, wherein the first comb tooth portion and the second comb tooth portion, the second comb tooth portion and the third comb tooth portion, and the third comb tooth portion and the fourth comb tooth portion are respectively arranged adjacent to each other, the first distance is the distance between two of the comb tooth portions adjacent to each other with one of the comb tooth portions in between, and the second distance is the distance between two of the comb tooth portions adjacent to each other without another of the comb tooth portions in between.

24. The integrated circuit described in claim 23, wherein the plurality of comb tooth portions have a fifth comb tooth portion on the other side of the fourth comb tooth portion in the second direction, and the selection circuit 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 that order.

25. An integrated circuit as described in claim 24, comprising a plurality of said receiving circuits, wherein the selection circuit is a circuit which selects two of the plurality of comb tooth portions for each of said receiving circuits and connects the two selected comb tooth portions to said receiving circuits, wherein the plurality of comb tooth portions have the first to fifth comb tooth portions in order from one side of said second direction for each of said receiving circuits, and wherein said selection circuit performs said selection so that for each of said receiving circuits, a first state in which the corresponding first and third comb tooth portions are selected, a second state in which the corresponding second and fourth comb tooth portions are selected, and a third state in which the corresponding third and fifth comb tooth portions are selected appear in that order.

26. The integrated circuit according to claim 25, wherein the plurality of receiving circuits include a first receiving circuit and a second receiving circuit adjacent to each other, and the fourth and fifth comb teeth corresponding to the first receiving circuit are the same as the first and second comb teeth corresponding to the second receiving circuit, respectively.

27. A sensor controller connected to the EMR sensor via the integrated circuit of claim 24, the sensor controller controlling the selection circuit to cause the first state, the second state, and the third state to appear in sequence.

28. A sensor controller as described in claim 27, which derives the position of the electromagnetic induction pen using an added pen signal obtained by adding together the pen signal output from the receiving circuit in the first state, the pen signal output from the receiving circuit in the second state, and the pen signal output from the receiving circuit in the third state.

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