Detection device

Abstract

To provide a detection device capable of increasing both hover detection accuracy and touch detection accuracy while dynamically switching between hover detection and touch detection.SOLUTION: A detection device 1 comprises: a sensor circuit 40 having a plurality of sensor electrodes 42 provided on a substrate 43, peripheral electrodes 41 provided around a detection area where the plurality of sensor electrodes 42 are arranged, and a shield electrode 44 provided on a surface opposite to a surface where the sensor electrodes 42 and the peripheral electrodes 41 are provided; an AFE circuit 15 for generating sensing data corresponding to a distance between the sensor electrodes 42 and a proximate object on the basis of detection signals Rx obtained from the sensor electrodes 42; a drive signal generation circuit 20 for generating a substantially sinusoidal drive signal and supplying it to the peripheral electrodes 41 and the shield electrode 44; and a control circuit 60 for controlling the AFE circuit 15 and the drive signal generation circuit 20. The control circuit 60 controls an amplitude value of the drive signal in accordance with the sensing data.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a detection device. [Background technology]

[0002] A capacitance-type detection device that detects the proximity of an object by detecting a change in capacitance is known (for example, Patent Document 1). Such a detection device having a so-called hover detection (proximity detection) function is provided with a plurality of detection electrodes and a shield electrode that is arranged around a detection area in which the plurality of detection electrodes are provided, and an electric signal is applied to the shield electrode.

[0003] Also, in order to improve the accuracy of hover detection, a configuration has been considered in which the ground potential of the detection circuit is set to a potential that periodically changes in synchronization with the detection signal, and this potential is applied to the shield electrode as the ground potential (for example, Patent Document 2). Patent Document 2 discloses a configuration in which a touch panel is overlaid on a detection panel for hover detection, thereby achieving both detection of an object that touches the detection surface (hereinafter also referred to as "touch detection") and hover detection. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 9,151,792 [Patent Document 2] JP 2023-90378 A Summary of the Invention [Problem to be solved by the invention]

[0005] In a detection device capable of performing both touch detection and hover detection, a detection panel for hover detection and a touch panel are generally provided with detection electrodes, respectively. In a detection device having a hover detection function, a configuration capable of performing both touch detection and hover detection at low cost without providing a touch panel is desired.

[0006] In hover detection, in order to capture minute changes in capacitance between the detection surface and an object that is far away, it is necessary to set the detection sensitivity high by relatively increasing the driving voltage and electrode size. Therefore, when the so-called hover state is changed to a touch state, the potential of the detection signal may be saturated. In addition, the detection accuracy may be reduced due to capacitive coupling occurring between adjacent electrodes.

[0007] An object of the present disclosure is to provide a detection device that can dynamically switch between hover detection and touch detection while improving both hover detection accuracy and touch detection accuracy. [Means for solving the problem]

[0008] A detection device according to one embodiment of the present disclosure includes a sensor circuit having a plurality of sensor electrodes provided on a substrate, a peripheral electrode provided around a detection area in which the plurality of sensor electrodes are provided, and a shield electrode provided on a surface opposite to the surface on which the sensor electrodes and the peripheral electrode are provided; an AFE circuit that generates sensing data corresponding to a distance between the sensor electrode and a nearby object based on a detection signal acquired from the sensor electrode; a drive signal generation circuit that generates a substantially sinusoidal drive signal and supplies it to the peripheral electrode and the shield electrode; and a control circuit that controls the AFE circuit and the drive signal generation circuit, wherein the control circuit controls an amplitude value of the drive signal according to the sensing data. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing a main configuration of a detection device according to the first embodiment. [Figure 2A] FIG. 2A is a schematic diagram showing an example of a schematic cross-sectional configuration in which a sensor circuit and a display panel are laminated in the detection device according to embodiment 1. FIG. [Figure 2B] FIG. 2B is a schematic diagram showing a modification of the schematic cross-sectional configuration shown in FIG. 2A. [Diagram 3] FIG. 3 is a schematic diagram showing a first connection example between the sensor circuit and the display panel of the detection device according to the first embodiment. [Figure 4] FIG. 4 is a schematic diagram showing a second connection example between the sensor circuit and the display panel of the detection device according to the first embodiment. [Diagram 5] FIG. 5 is a diagram illustrating an example of a block configuration of the detection device according to the first embodiment. [Figure 6] FIG. 6 is a diagram showing an example of the configuration of a drive signal generating circuit according to a comparative example. [Figure 7] FIG. 7 is a schematic diagram showing an example of signal waveform transition in a drive signal generating circuit according to a comparative example. [Figure 8] FIG. 8 is a schematic diagram showing an example of the operation of an active filter. [Figure 9] FIG. 9 is a graph showing a schematic diagram of frequency characteristics of the electric resistance value of the digital potentiometer. [Figure 10A] FIG. 10A is a schematic diagram showing detection values ​​in a detection region in a heat map. [Figure 10B] FIG. 10B is a schematic diagram showing the detection values ​​in the detection region in a heat map. [Figure 11A] FIG. 11A is a graph showing the relationship between the amplitude value of the drive signal and the sensing data at the contact position of the detection object. [Figure 11B] FIG. 11B is a graph showing the relationship between the amplitude value of the drive signal and the sensing data error due to capacitive coupling. [Figure 12] FIG. 12 is a conceptual diagram showing an example of a phase change of a drive signal when the amplitude value of the drive signal is changed in a configuration of a drive signal generating circuit according to a comparative example. [Figure 13] FIG. 13 is a diagram illustrating an example of the configuration of a drive signal generating circuit according to the first embodiment. [Figure 14] FIG. 14 is a diagram illustrating an example of a functional circuit block configuration of the detection device according to the first embodiment. [Figure 15] FIG. 15 is a main flowchart showing an example of a detection process in the detection device. [Figure 16] FIG. 16 is a sub-flowchart illustrating an example of the baseline setting process. [Figure 17] FIG. 17 is a sub-flowchart showing an example of the detection mode determination process. [Figure 18A] FIG. 18A is a diagram illustrating an example of the configuration of an AFE circuit according to the second embodiment. [Figure 18B] FIG. 18B is a diagram illustrating an example of the configuration of the AFE circuit according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The form (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited by the contents described in the following embodiment. In addition, the components described below include those that a person skilled in the art can easily imagine and those that are substantially the same. Furthermore, the components described below can be appropriately combined. In addition, the disclosure is merely an example, and those that a person skilled in the art can easily imagine appropriate modifications while maintaining the gist of the invention are naturally included in the scope of the present invention. In addition, in order to make the explanation clearer, the drawings may be schematic in terms of the width, thickness, shape, etc. of each part compared to the actual embodiment, but they are merely examples and do not limit the interpretation of the present invention. In addition, in this specification and each figure, elements similar to those described above with respect to the previous figures may be given the same reference numerals, and detailed explanations may be omitted as appropriate.

[0011] In this specification and the claims, when expressing an aspect of arranging another structure on top of a certain structure, the term "on top" is used, unless otherwise specified, to include both a case in which another structure is arranged directly on top of a certain structure so as to be in contact with the certain structure, and a case in which another structure is arranged above a certain structure via yet another structure.

[0012] (Embodiment 1) 1 is a diagram showing a main configuration of a detection device 1 according to embodiment 1. As shown in FIG.

[0013] The sensor circuit 40 is provided with a plurality of sensor electrodes (first electrodes) 42 and a peripheral electrode (second electrode) 41 on a substrate 43. The detection device 1 is a device that realizes both hover detection, which detects the position and movement of a detectable object such as a finger when the detectable object is not in contact with the detection surface of the sensor circuit 40, and touch detection, which detects the position and movement of a detectable object when the detectable object is in contact with the detection surface of the sensor circuit 40. In the present disclosure, the detection device 1 performs hover detection and touch detection using a self-capacitance method. In other words, in the detection device 1, the sensor circuit 40 has a hover detection mode (first detection mode) that detects the position and movement of a detectable object when the detectable object is not in contact with the detection surface of the sensor circuit 40, and a touch detection mode (second detection mode) that detects the position and movement of a detectable object when the detectable object is in contact with the detection surface of the sensor circuit 40.

[0014] The sensor circuit 40 has a detection area SA and a peripheral area BE outside the detection area SA. The detection area SA is an area where a sensor electrode 42 is provided, and is an area for detecting an object to be detected that is close to the detection surface. The peripheral area BE is an area outside the detection area SA where the sensor electrode 42 is not provided, and is an area where peripheral electrodes 41 are provided along the four sides of the detection area SA.

[0015] In the following description, the first direction Dx is a direction in a plane parallel to the substrate 43. The second direction Dy is a direction in a plane parallel to the substrate 43, and is a direction perpendicular to the first direction Dx. The second direction Dy may intersect the first direction Dx without being perpendicular thereto. The third direction Dz is a direction perpendicular to the first direction Dx and the second direction Dy, and is a normal direction to the main surface of the substrate 43. In addition, "planar view" refers to the positional relationship when viewed from a direction perpendicular to the substrate 43.

[0016] The multiple sensor electrodes 42 are arranged in a matrix in the detection area SA of the substrate 43. In other words, the multiple sensor electrodes 42 are arranged side by side in the first direction Dx and the second direction Dy. The multiple sensor electrodes 42 are each electrically connected to the AFE circuit 15 via wiring (not shown).

[0017] The peripheral electrode 41 is disposed surrounding a plurality of sensor electrodes 42 provided in the detection area SA. The peripheral electrode 41 and the sensor electrode 42 are electrodes disposed side by side on the substrate 43. As described later, a shield electrode 44 is provided on the surface of the substrate 43 opposite to the surface on which the sensor electrodes 42 and the peripheral electrode 41 are provided. The shield electrode 44 is a film-like or plate-like electrode facing the sensor electrodes 42 across the substrate 43.

[0018] The sensor circuit 40 is connected to the detection circuit 2. The detection circuit 2 includes an AFE circuit 15 that performs hover detection based on the output of the sensor circuit 40, and a control circuit 60 that controls the hover detection operation in the AFE circuit 15. The AFE circuit 15 is, for example, an analog front-end circuit (AFE: Analog Front End). The control circuit 60 includes, for example, an MCU (Micro Control Unit).

[0019] A processing device (external processing device) 110 is connected to the detection circuit 2. The processing device 110 is a device that functions as a host computer (HOST) of the detection device 1 according to the embodiment 1. The processing device 110 is, for example, a POS (Point of Sale) cash register terminal, but is not limited thereto and may be any terminal capable of accepting a hover operation in the detection device 1.

[0020] 2A is a schematic diagram showing an example of a schematic cross-sectional configuration in which the sensor circuit 40 of the detection device 1 according to the embodiment 1 and the display panel 250 are laminated. The display panel 250 is a display panel that displays and outputs an image. FIG. 3 is a schematic diagram showing a first connection example between the sensor circuit 40 of the detection device 1 according to the embodiment 1 and the display panel 250. FIG. 3 illustrates a so-called on-cell type device in which the sensor circuit 40 of the detection device 1 according to the embodiment 1 is mounted on the display panel 250.

[0021] The display panel 250 includes an array substrate SUB1, a counter substrate SUB2, a first polarizer PL1, and a second polarizer PL2. The first polarizer PL1, the array substrate SUB1, the counter substrate SUB2, and the second polarizer PL2 are laminated in this order.

[0022] The array substrate SUB1 is a drive circuit substrate for driving a plurality of pixels. The counter substrate SUB2 is provided opposite the array substrate SUB1. A liquid crystal layer, which is a display function layer, is provided between the array substrate SUB1 and the counter substrate SUB2.

[0023] The sensor circuit 40 is attached onto the display panel 250 via an adhesive layer 260. The adhesive layer 260 is exemplified by an OCA (Optical Clear Adhesive).

[0024] The sensor electrodes 42 and the peripheral electrode 41 are provided on the same substrate 43. The substrate 43 is a film-like or plate-like member formed of an insulating material, such as a resin film or a glass substrate. The sensor electrodes 42 and the peripheral electrodes 41 are not limited to being provided on the same layer of the substrate 43, and may be provided on different layers of the substrate 43. The sensor electrode 42 is formed of a conductive material having translucency, such as ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide). The peripheral electrode 41 may be formed of the same material as the sensor electrode 42, or may be formed of a metal material different from that of the sensor electrode 42.

[0025] A cover member 270 is provided on the sensor circuit 40 via an adhesive layer 280. The adhesive layer 280 is, for example, OCA. A shield electrode 44 is provided on the surface of the substrate 43 opposite to the surface on which the sensor electrode 42 and the peripheral electrode 41 are provided. In other words, the shield electrode 44 is provided between the surface of the sensor circuit 40 opposite to the surface on which the cover member 270 is provided and the display panel 250. The adhesive layer 260 is in contact with the shield electrode 44 provided on the sensor circuit 40.

[0026] The shield electrode 44 contains, for example, a conductive translucent oxide such as ITO or IZO, or a metal. Examples of the metal include metals (zero-valent metals) such as molybdenum, tungsten, tantalum, aluminum, and copper. The shield electrode 44 may have a single-layer structure or a multilayer structure. When the shield electrode 44 has a multilayer structure, the shield electrode 44 may have a layer containing an oxide and a layer containing a metal. The shield electrode 44 may be any layer as long as it has transparency and conductivity, and can be called a transparent conductive layer.

[0027] A second reference potential, which will be described later, is supplied to the shield electrode 44. In addition, the same signal as that supplied to the peripheral electrode 41 is supplied to the shield electrode 44. In this embodiment, since the shield electrode 44 is provided between the sensor circuit 40 and the display panel 250, noise superimposed on the sensor electrode 42 of the sensor circuit 40 from the display panel 250 can be shielded.

[0028] The cover member 270 is attached onto the sensor circuit 40. For example, a glass substrate or a resin substrate is used for the cover member 270. The upper surface of the cover member 270 is a detection surface for hover detection.

[0029] Note that, instead of the schematic cross-sectional configuration shown in Fig. 2A, a schematic cross-sectional configuration shown in Fig. 2B may be adopted. Fig. 2B is a schematic view showing a modified example of the schematic cross-sectional configuration shown in Fig. 2A.

[0030] The display panel 250 is, for example, a liquid crystal display panel (LCD: Liquid Crystal Display). In this case, a backlight is provided on the opposite side of the display panel 250 from the sensor circuit 40. The display panel 250 is not limited to this, and may be, for example, an organic EL display panel (OLED: Organic Light Emitting Diode) or an inorganic EL display panel (micro LED, mini LED). Alternatively, the display panel 250 may be an electrophoretic display panel (EPD: Electrophoretic Display) that uses electrophoretic elements as display elements.

[0031] In a so-called on-cell type device configuration shown in Fig. 3, the detection device 1 includes an FPC (Flexible Printed Circuits) 70. The FPC 70 is connected to a PCB (Printed Circuit Board) 46. Various circuits constituting the detection circuit 2 are mounted on the PCB 46. Fig. 3 illustrates circuits 46a and 46b as examples of the various circuits constituting the detection circuit 2. The circuits 46a and 46b function as, for example, an AFE circuit 15 and a control circuit 60.

[0032] The display panel 250 includes an FPC 255. The FPC 255 is provided with various circuits related to the operation of the display panel 250. The PCB 46 is connected to the processing device 110 via a cable 47. The cable 47 has a function of transmitting signals generated between the detection device 1 and the processing device 110. An example of the cable 47 is a Universal Serial Bus (USB) cable.

[0033] Fig. 4 is a schematic diagram showing a second connection example between the sensor circuit 40 of the detection device 1 according to embodiment 1 and the display panel 250. Fig. 4 illustrates a so-called in-cell type or hybrid type device in which the sensor circuit 40 of the detection device 1 according to embodiment 1 is built into and integrated with the display panel 250. Building the sensor circuit 40 of the detection device 1 according to embodiment 1 into the display panel 250 includes, for example, sharing some of the members such as a substrate and electrodes used as the display panel 250 with some of the members such as a substrate and electrodes used as the sensor circuit 40 of the detection device 1 according to embodiment 1.

[0034] 4, the FPC 255 is connected to the PCB 46. In this case, the cable 47 further has the function of transmitting signals generated between the display panel 250 and the processing device 110.

[0035] FIG. 5 is a diagram showing an example of a block configuration of the detection device 1 according to the first embodiment.

[0036] As shown in FIG. 5, the detection device 1 includes, in addition to the above-mentioned sensor circuit 40, AFE circuit 15, and control circuit 60, a first power supply circuit 11 (POW1), an isolated DC-DC converter 12, a second power supply circuit 13 (POW2), a drive signal generation circuit 20, a first isolator 51, and a second isolator 52.

[0037] In the present disclosure, the processing device 110, the control circuit 60, the first power supply circuit 11, and the drive signal generation circuit 20 are included in the first reference potential block 3. Also, in the present disclosure, the second power supply circuit 13, the AFE circuit 15, and the sensor circuit 40 are included in the second reference potential block 4. The processing device 110, the control circuit 60, the first power supply circuit 11, and the drive signal generation circuit 20 included in the first reference potential block 3 operate with the first reference potential GND1, which is a fixed potential, as the ground potential. The second power supply circuit 13, the AFE circuit 15, and the sensor circuit 40 included in the second reference potential block 4 operate with the second reference potential GND2 generated by the drive signal generation circuit 20 as the ground potential.

[0038] The first power supply circuit 11 converts the voltage of the power supplied via the power line VBUS of the USB cable and supplies the converted voltage to the control circuit 60 and the drive signal generating circuit 20.

[0039] The insulated DC-DC converter 12 performs insulation and power transmission between the processing device 110 and the second power supply circuit 13. The insulated DC-DC converter 12 performs power transmission by a magnetic insulation method.

[0040] In the isolated DC-DC converter 12, power is supplied to the coil on the first reference potential block 3 side via the power line VBUS of the USB cable, causing the coil to generate a magnetic field. The coil on the second reference potential block 4 side is provided within the range of influence of the magnetic field generated by the coil on the first reference potential block 3 side.

[0041] An induced electromotive force is generated in the coil on the second reference potential block 4 side according to the magnetic field generated by the coil on the first reference potential block 3 side. The power generated in the coil on the second reference potential block 4 side is supplied to the second power supply circuit 13.

[0042] The second power supply circuit 13 converts the voltage of the power supplied from the insulating DC-DC converter 12 and supplies the converted power to the AFE circuit 15 .

[0043] The AFE circuit 15 generates a square wave signal Tx as a periodically varying potential having a periodic potential variation pattern. The square wave signal Tx includes a fundamental frequency component and a harmonic component of a drive signal to be supplied to the peripheral electrode 41 and the shield electrode 44 of the sensor circuit 40.

[0044] In addition, the AFE circuit 15 acquires sensing data from the multiple sensor electrodes 42 and outputs the data to the control circuit 60 via the first isolator 51.

[0045] In the present disclosure, signals between the AFE circuit 15 and the control circuit 60 are transmitted by a serial peripheral interface (SPI), which is a clock synchronous serial interface. Note that the serial interface for transmitting signals between the AFE circuit 15 and the control circuit 60 is not limited to the SPI.

[0046] The first isolator 51 provides insulation and signal transmission between the control circuit 60 and the AFE circuit 15. The electrical signals inputted and outputted via the first isolator 51 are synchronized between the control circuit 60 and the AFE circuit 15.

[0047] The second isolator 52 provides insulation between the AFE circuit 15 and the drive signal generation circuit 20 and transmits the square wave signal Tx. The square wave signal Tx input / output via the second isolator 52 is synchronized between the AFE circuit 15 and the drive signal generation circuit 20.

[0048] The second isolator 52 performs optically isolated signal transmission using, for example, a photocoupler. The signal transmission method between the control circuit 60 and the AFE circuit 15 in the first isolator 51 may be the same as that of the second isolator 52, or may be a different method. In other words, examples of the first isolator 51 include an optically isolated photocoupler, or a magnetically isolated digital isolator similar to the isolated DC-DC converter 12.

[0049] The first isolator 51 is capable of bidirectional signal transmission from the control circuit 60 to the AFE circuit 15 and from the AFE circuit 15 to the control circuit 60. In a configuration in which an optically isolated photocoupler is used as the first isolator 51, a photocoupler that transmits a signal from the control circuit 60 to the AFE circuit 15 and a photocoupler that transmits a signal from the AFE circuit 15 to the control circuit 60 are connected in parallel.

[0050] The control circuit 60 transmits various information related to the sensing data and signals such as control commands to and from the processing device 110 .

[0051] Furthermore, based on reference information (DP control reference data) indicating the correspondence between the fundamental frequency of the square wave signal Tx output from the AFE circuit 15 and the electrical resistance value of the digital potentiometer 22 described later, the control circuit 60 outputs an electrical resistance value setting command to the digital potentiometer 22 to set the electrical resistance value of the digital potentiometer 22 to an electrical resistance value corresponding to the fundamental frequency of the square wave signal Tx output from the AFE circuit 15. As a result, the electrical resistance value of the digital potentiometer 22 is controlled to an electrical resistance value corresponding to the fundamental frequency of the square wave signal Tx.

[0052] The control circuit 60 also performs noise determination processing of the sensing data and position determination (coordinate calculation processing) of the detectable object based on the sensing data. The noise determination processing is processing performed to determine the amount of noise components contained in the sensing data. The coordinate calculation processing is processing performed to determine the position of the detectable object adjacent to the sensor circuit 40. Specifically, the coordinate calculation processing can derive, for example, the position in the first direction Dx, the position in the second direction Dy, and the position in the third direction Dz (see FIG. 1) of the detectable object adjacent to the sensor circuit 40. The details of the noise determination processing and the coordinate calculation processing are similar to those well known, and therefore detailed explanations will be omitted.

[0053] In the present disclosure, signals between the control circuit 60 and the processing device 110 are transmitted by USB, which is a serial interface. Specifically, signals between the control circuit 60 and the processing device 110 are transmitted via signal lines D+ and D- of a USB cable. Note that the serial interface for transmitting signals between the control circuit 60 and the processing device 110 is not limited to USB.

[0054] In the above-described configuration, the first reference potential block 3 including the processing device 110, the control circuit 60, the first power supply circuit 11, and the drive signal generating circuit 20, and the second reference potential block 4 including the second power supply circuit 13, the AFE circuit 15, and the sensor circuit 40 are electrically insulated via the insulated DC-DC converter 12, the first isolator 51, and the second isolator 52.

[0055] The first reference potential GND1 given as a ground potential to the first reference potential block 3 is a fixed potential held by a large electrode such as a solid electrode. On the other hand, the second reference potential GND2 given as a ground potential to the second reference potential block 4 is a periodically varying potential generated by the drive signal generating circuit 20.

[0056] In the detection device 1 according to the present disclosure, the fluctuation period of the periodically fluctuating potential (second reference potential GND2) is the same as the generation period (the rectangular wave period of the rectangular wave signal Tx) of the rectangular wave generated by the AFE circuit 15. In other words, the second reference potential GND2 is a potential that fluctuates periodically in synchronization with the rectangular wave signal Tx generated by the AFE circuit 15.

[0057] Next, a description will be given of the drive signal generating circuit 20. Before describing the specific drive signal generating circuit 20 of the detection device 1 according to the first embodiment, the configuration and operation of a drive signal generating circuit 20a according to a comparative example will be described.

[0058] 6 is a diagram showing an example of the configuration of a drive signal generation circuit according to a comparative example. In the configuration according to the comparative example, a drive signal generation circuit 20a includes an LPF circuit 21a, an active filter (AF) circuit 23, and an amplifier circuit 24a.

[0059] The LPF circuit 21 a generates an intermediate wave signal based on the square wave signal Tx output from the AFE circuit 15 via the second isolator 52 .

[0060] In the configuration of the drive signal generating circuit 20a according to the comparative example, the LPF circuit 21a includes a digital potentiometer (DP) 22. The digital potentiometer 22 is a digital potentiometer circuit capable of adjusting an electric resistance value in response to a command from the control circuit 60. The digital potentiometer 22 is provided on an output transmission path of the square wave signal Tx output from the AFE circuit 15 via the second isolator 52. Hereinafter, the digital potentiometer 22 is also referred to as a "DP circuit 22." Specifically, the electric resistance value of the DP circuit 22 is controlled so that the amplitude value Vpp of the drive signal output from the subsequent amplifier circuit 24a is constant (for example, 6.8 V) regardless of the setting of the fundamental frequency of the square wave signal Tx.

[0061] The LPF circuit 21a functions as a low pass filter (LPF) using an RC circuit formed of a DP circuit 22 and a downstream capacitive element C. An intermediate wave signal that has been impedance converted by a voltage follower circuit connected downstream of the RC circuit is output to an active filter circuit 23.

[0062] In the configuration shown in Fig. 6, the active filter circuit 23 includes a first filter circuit 23A and a second filter circuit 23B. An example of the active filter circuit 23 is a Sallen-Key type fourth-order active LPF shown in Fig. 6. A detailed description of the configurations of the first filter circuit 23A and the second filter circuit 23B will be omitted.

[0063] The LPF circuit 21a and the active filter circuit 23 provide an output signal having a substantially sinusoidal shape (hereinafter, also simply referred to as a "sine wave signal") that suppresses the high frequency components of the square wave signal output from the AFE circuit 15 via the second isolator 52. This makes it possible to prevent unwanted noise components from being amplified in the downstream amplifier circuit 24a, thereby preventing an increase in radiation noise.

[0064] The amplifier circuit 24a is an inverting amplifier circuit that inverts, amplifies, and converts the impedance of the sine wave signal output from the active filter circuit 23. The sine wave signal inverted and amplified by the amplifier circuit 24a is supplied as a drive signal to the peripheral electrode 41 and the shield electrode 44 of the sensor circuit 40, and is also provided as a second reference potential GND2 that is the ground potential of the second reference potential block 4. Depending on the polarity of the sine wave signal, the amplifier circuit 24a may not invert the polarity.

[0065] 7 is a schematic diagram showing an example of signal waveform transition in a drive signal generating circuit according to a comparative example. The square wave signal output from the AFE circuit 15 becomes an intermediate wave signal whose output is adjusted by the electrical resistance of the DP circuit 22. Furthermore, the intermediate wave signal output from the LPF circuit 21a becomes an approximately sinusoidal output signal by the active filter circuit 23.

[0066] In the present disclosure, the AFE circuit 15 has a function of setting the fundamental frequency of the square wave signal Tx within a range of 140 kHz to 200 kHz. Example A shown in Fig. 7 shows a case where the fundamental frequency of the square wave signal Tx is 200 kHz. Example B shown in Fig. 7 shows a case where the fundamental frequency of the square wave signal Tx is 140 kHz. Note that the frequency setting range of the square wave signal Tx in the AFE circuit 15 (140 kHz to 200 kHz) is just an example and is not limited thereto.

[0067] 8 is a schematic diagram showing an example of the operation of an active filter. When a low-pass filter is used to generate a substantially sinusoidal signal from a square wave signal, if the filter is set to be optimized for a square wave signal of a high frequency (e.g., 200 kHz), the amplitude of the sinusoidal signal may become large for a square wave signal of a lower frequency (e.g., 140 kHz), and the signal may become saturated by the power supply potential of the amplifier circuit 24a, resulting in a signal waveform with distortion near the peak.

[0068] In the present disclosure, the electrical resistance value of the DP circuit 22 is controlled to a value that makes the amplitude value Vpp of the drive signal output from the amplifier circuit 24a constant (for example, 6.8 V) in response to the fundamental frequency (within a frequency setting range of 140 kHz to 200 kHz) of the square wave signal Tx output from the AFE circuit 15. This makes it possible to generate an output signal with a substantially sinusoidal waveform in which distortion of the time series change in the signal strength near the peak of the output signal is suppressed, as shown in FIG.

[0069] FIG. 9 is a graph showing a schematic diagram of the frequency characteristic of the electric resistance value of the digital potentiometer. The horizontal axis of FIG. 9 shows the fundamental frequency of the square wave signal Tx, and the vertical axis shows the electric resistance value of the digital potentiometer. In the example shown in FIG. 9, the electric resistance value of the digital potentiometer is controlled so that the lower the fundamental frequency of the square wave signal Tx, the higher the electric resistance value of the digital potentiometer is, and the higher the fundamental frequency of the square wave signal Tx, the lower the electric resistance value of the digital potentiometer is. In this manner, in the present disclosure, the electric resistance value of the DP circuit 22 is controlled according to the fundamental frequency of the square wave signal Tx, so that the amplitude value of the drive signal is constant (for example, 6.8 V).

[0070] 5, the multiple sensor electrodes 42 are each connected to the AFE circuit 15. The peripheral electrode 41 and the shield electrode 44 function as an active shield whose potential varies periodically in response to changes in the second reference potential GND2 provided by the drive signal generating circuit 20a. The AFE circuit 15 acquires an electric signal corresponding to the self-capacitance generated in each sensor electrode 42 as a detection signal Rx.

[0071] The magnitude of the detection signal Rx obtained from each sensor electrode 42 changes depending on the distance between each sensor electrode 42 and a nearby object. The AFE circuit 15 generates sensing data according to the distance between each sensor electrode 42 and a nearby object based on the detection signal Rx acquired from each sensor electrode 42, and outputs the sensing data to the control circuit 60.

[0072] 10A and 10B are schematic diagrams showing detection values ​​in a detection region in a heat map. Here, a heat map is defined as a visualization of the magnitude relationship of sensing data in the detection region SA arranged in a matrix as shown in FIG. 1, using shading in the regions corresponding to the sensor electrodes 42. Also, the greater the sensing data, the darker the region, and the smaller the sensing data, the lighter the region.

[0073] Fig. 10A shows an example in which the object to be detected comes into contact with the detection surface of sensor circuit 40 at position A when detection area SA is viewed in a plan view. Fig. 10B shows an example in which the object to be detected comes into contact with the detection surface of sensor circuit 40 near the boundary line between position D and position D'.

[0074] In the detection device 1 according to the present disclosure, the size of the sensor electrode 42 is increased in order to capture minute changes in capacitance occurring between the detection surface and an object distant from the detection surface. Here, as an example, the length of one side of the substantially square sensor electrode 42 is set to 32 mm. Also, the amplitude value Vpp of the drive signal is set to 6.8 V. Note that the numerical examples of the size of the sensor electrode 42 and the amplitude value of the drive signal shown in the present disclosure are merely examples, and are not limited to the description of the present disclosure.

[0075] Furthermore, for example, in a configuration in which wiring connecting each sensor electrode 42 to the AFE circuit 15 is provided between the sensor electrodes 42 arranged in the Dx direction, capacitive coupling occurs between the sensor electrodes 42 adjacent in the Dy direction. In this case, for example, the accuracy of the sensing data at positions C and C' shown in FIG. 10A may decrease.

[0076] Fig. 11A is a graph showing the relationship between the amplitude value of the drive signal and the sensing data at the contact position of the object to be detected. Fig. 11B is a graph showing the relationship between the amplitude value of the drive signal and the sensing data error due to capacitive coupling. Here, a configuration is shown in which wiring connecting each sensor electrode 42 to the AFE circuit 15 is provided between the sensor electrodes 42 arranged in the Dx direction.

[0077] 11A shows sensing data at position A shown in FIG. 10A. As shown in FIG. 11A, the sensing data at position A shown in FIG. 10A where the object to be detected contacts the detection surface of the sensor circuit 40 is significantly larger than the surrounding sensing data, and is saturated in a region where the amplitude value Vpp of the drive signal is approximately 4V or more. Also, as shown in FIG. 10B, in an example where the object to be detected contacts the detection surface of the sensor circuit 40 near the boundary line of the sensor electrode 42, the sensing data is saturated at both positions D and D' where the object to be detected contacts the sensor circuit 40. This may result in a decrease in the accuracy of determining the position of the object to be detected by the coordinate calculation process of the control circuit 60.

[0078] The solid line in Fig. 11B indicates the average value of the sensing data at positions C and C' shown in Fig. 10A. The dashed-dotted line in Fig. 11B indicates the average value of the sensing data at positions B and B' shown in Fig. 10A. The dashed-two-dotted line in Fig. 11B indicates the difference obtained by subtracting the average value of the sensing data at positions B and B' shown in Fig. 10A from the average value of the sensing data at positions C and C' shown in Fig. 10A.

[0079] As shown by the dashed line in Fig. 11B, the sensing data at positions B and B' shown in Fig. 10A changes almost linearly with respect to the change in the amplitude value Vpp of the drive signal. On the other hand, as shown by the solid line in Fig. 11B, when the amplitude value Vpp of the drive signal exceeds 2.5V, the sensing data at positions C and C' shown in Fig. 10A differs from the sensing data at positions B and B' shown in Fig. 10A, as shown by the two-dot chain line in Fig. 11B. This difference can be considered as a sensing data error caused by capacitive coupling occurring between the sensor electrodes 42 adjacent in the Dy direction. In addition to the saturation of the sensing data at the contact position, the sensing data error caused by this capacitive coupling increases the possibility that the accuracy of the position determination of the detected object by the coordinate calculation process of the control circuit 60 will decrease.

[0080] As shown in FIG. 11A, at the contact position of the detection target, the sensing data is saturated in a region where the amplitude value Vpp of the driving signal is approximately 4V or more. Also, as shown in FIG. 11B, when the amplitude value Vpp of the driving signal exceeds 2.5V, the sensing data at positions C and C' shown in FIG. 10A has a sensing data error due to capacitive coupling occurring in adjacent sensor electrodes 42, as shown by the two-dot chain line in FIG. 11B. Therefore, in order to achieve both hover detection and touch detection, it is possible to deal with this by reducing the amplitude value Vpp of the driving signal during touch detection. Specifically, in the example shown in FIG. 11A and FIG. 11B, for example, the amplitude value Vpp of the driving signal during touch detection may be set to 2.5V or less.

[0081] FIG. 12 is a conceptual diagram showing an example of a phase change of a drive signal when the amplitude value of the drive signal is changed in a configuration of a drive signal generating circuit according to a comparative example.

[0082] As described above, in the configuration of the drive signal generation circuit 20a according to the comparative example shown in Fig. 6, the LPF circuit 21a functions as a low-pass filter by an RC circuit configured with the DP circuit 22 and the downstream capacitive element C. For this reason, as shown in Fig. 12, when the amplitude value Vpp of the drive signal is changed by dynamically changing the electrical resistance of the DP circuit 22 without changing the frequency setting of the rectangular wave signal Tx, a phase change (Δφ) occurs, causing a shift in the timing of acquiring the sensing data, which may result in a decrease in detection sensitivity.

[0083] Hereinafter, a specific configuration and operation of the drive signal generating circuit 20 of the detection device 1 according to embodiment 1 for suppressing saturation of the sensing data at the contact position and degradation of position determination accuracy due to sensing data errors resulting from capacitive coupling between adjacent sensor electrodes will be described.

[0084] 13 is a diagram showing an example of the configuration of the drive signal generation circuit according to embodiment 1. In the configuration according to embodiment 1, the drive signal generation circuit 20 includes an LPF circuit 21, an active filter circuit 23, and an amplifier circuit 24. The drive signal generation circuit 20 differs from the drive signal generation circuit 20a according to the comparative example in the electrical position where the DP circuit 22 is provided.

[0085] The LPF circuit 21 is provided with a resistive element R instead of the DP circuit 22. The LPF circuit 21 functions as a low-pass filter by an RC circuit configured with the resistive element R and a capacitive element C in the subsequent stage. An intermediate wave signal that has been impedance converted by a voltage follower circuit connected in the subsequent stage of the RC circuit is output to the active filter circuit 23.

[0086] The amplifier circuit 24 includes a DP circuit 22 as an input resistor of an inverting amplifier circuit including a negative feedback resistor Rf. The output Vout of the amplifier circuit 24 is expressed by the following formula (1), where the input of the amplifier circuit 24 is Vin. Note that the amplifier circuit 24 may include a capacitance element Cf for phase compensation in parallel with the negative feedback resistor Rf.

[0087] Vout = -(Rf / Rdp) × Vin (1)

[0088] The sine wave signal inverted and amplified by the amplifier circuit 24 is impedance-converted by a voltage follower circuit connected downstream of the inverting amplifier circuit, and is supplied as a drive signal to the peripheral electrode 41 and the shield electrode 44 of the sensor circuit 40, and is also provided as a second reference potential GND2, which is the ground potential of the second reference potential block 4. Depending on the polarity of the sine wave signal, the amplifier circuit 24 may not invert the polarity.

[0089] In the configuration of the drive signal generation circuit 20 according to the first embodiment described above, when the amplitude value Vpp of the drive signal is changed by changing the electrical resistance value of the DP circuit 22, no phase change occurs in the LPF circuit 21. Therefore, it is possible to suppress a decrease in detection sensitivity caused by a shift in the acquisition timing of the sensing data.

[0090] FIG. 14 is a diagram illustrating an example of a functional circuit block configuration of the detection device according to the first embodiment.

[0091] 14, the AFE circuit 15 has a readout circuit 151, an ADC (Analog Digital Converter) circuit 152, and a DSP (Digital Signal Processor) circuit 153. Each circuit element of the AFE circuit 15 operates with a second reference potential GND2, which is a periodically varying potential generated by the drive signal generation circuit 20, as a ground potential.

[0092] The readout circuit 151 acquires the detection signal Rx from each of the sensor electrodes 42 .

[0093] The ADC circuit 152 converts the detection signal Rx acquired by the readout circuit 151 from an analog signal to a digital signal.

[0094] The DSP circuit 153 performs digital filtering on the digital data converted by the ADC circuit 152 to generate a detection signal Rx.

[0095] The AFE circuit 15 outputs the sensing data generated by the DSP circuit 153 to the control circuit 60 via the first isolator 51.

[0096] The control circuit 60 includes a read circuit 61, a noise determination circuit 62, a coordinate calculation circuit 63, and a memory circuit 64. Each circuit element of the control circuit 60 operates with a first reference potential GND1, which is a fixed potential, as a ground potential.

[0097] The read circuit 61 acquires the sensing data output from the AFE circuit 15 via the first isolator 51 .

[0098] The noise determination circuit 62 performs the above-mentioned noise determination process based on the sensing data acquired by the readout circuit 61 .

[0099] The coordinate calculation circuit 63 performs the above-mentioned coordinate calculation process based on the sensing data acquired by the readout circuit 61 .

[0100] The memory circuit 64 holds in advance DP control reference data indicating the correspondence between the fundamental frequency of the square wave signal Tx output from the AFE circuit 15 and the electrical resistance value of the DP circuit 22. The DP control reference data is, for example, data in a table format in which the fundamental frequency of the square wave signal Tx output from the AFE circuit 15 and the electrical resistance value of the DP circuit 22 are in one-to-one correspondence.

[0101] In addition, in the present disclosure, it is assumed that the memory circuitry 64 stores in advance a threshold value used for determining the detection mode in the detection mode setting process described below.

[0102] The control circuit 60 refers to the DP control reference data stored in the memory circuit 64, and outputs an electrical resistance value setting command to set the electrical resistance value of the DP circuit 22 to an electrical resistance value corresponding to the fundamental frequency of the rectangular wave signal Tx output from the AFE circuit 15.

[0103] Furthermore, the control circuit 60 has a function of changing the fundamental frequency of the square wave signal Tx output from the AFE circuit 15. When the fundamental frequency of the square wave signal Tx output from the AFE circuit 15 is changed, the control circuit 60 resets the electrical resistance value of the DP circuit 22 according to the fundamental frequency of the square wave signal Tx after the change.

[0104] In the present disclosure, the control circuit 60 has a function of changing the fundamental frequency of the square wave signal Tx output from the AFE circuit 15. In the present disclosure, the drive frequency in the self-capacitance hover detection, that is, the fundamental frequency of the square wave signal Tx output from the AFE circuit 15, can be changed. This makes it possible to suppress the influence of noise. Hereinafter, the change in the fundamental frequency of the square wave signal Tx is also referred to as "frequency hopping."

[0105] 15 is a main flowchart showing an example of a detection process in the detection device 1. In the present disclosure, the detection device 1 performs a sensing operation by dynamically switching between a hover detection mode (first detection mode) and a touch detection mode (second detection mode) according to the maximum value of sensing data acquired in the detection area SA.

[0106] When the sensing operation by the detection device 1 starts (step S1), the detection device 1 sets baselines in both the hover detection mode and the touch detection mode (step S2). Fig. 16 is a sub-flowchart showing an example of the baseline setting process.

[0107] In the baseline setting process (step S2), first, the control circuit 60 sets an electrical resistance value for hover detection in the DP circuit 22 (step S21). The electrical resistance value for hover detection is set to, for example, a value that makes the amplitude value Vpp of the drive signal 6.8 V.

[0108] The AFE circuit 15 acquires the detection signals Rx from the sensor electrodes 42 when no object to be detected is in proximity to the sensor circuit 40, and generates baseline data for hover detection based on the detection signals Rx (step S22).

[0109] Next, the control circuit 60 sets an electrical resistance value for touch detection in the DP circuit 22 (step S23). The electrical resistance value for touch detection is set to, for example, a value that makes the amplitude value Vpp of the drive signal 2.5V.

[0110] The AFE circuit 15 acquires the detection signals Rx from the sensor electrodes 42 when the object to be detected is not in proximity to the sensor circuit 40, and generates baseline data for touch detection based on the detection signals Rx (step S24).

[0111] After executing the baseline setting process (step S2), the process returns to the main flow of the detection process shown in FIG. 15. The AFE circuit 15 acquires the detection signal Rx from each sensor electrode 42, generates sensing data, and transmits it to the control circuit 60. The control circuit 60 sets the detection mode based on the sensing data transmitted from the AFE circuit 15 (step S3). FIG. 17 is a sub flowchart showing an example of the detection mode determination process.

[0112] In the detection mode setting process (step S3), first, the control circuit 60 determines whether the current detection mode is the hover detection mode or the touch detection mode. More specifically, the control circuit 60 determines whether the current detection mode is the hover detection mode (step S31).

[0113] If it is the hover detection mode (step S31; Yes), the control circuit 60 determines whether the maximum value RDHmax of each sensing data (RDH(n), where n is a natural number from 1 to N, and N is the number of sensor electrodes in the detection area SA) in the detection area SA is greater than or equal to a predetermined threshold value RDHth (RDHmax≧RDHth, step S32). The threshold value RDHth is stored in advance in the memory circuit 64.

[0114] If the maximum value RDHmax of the sensing data is less than the threshold value RDHth (step S32; No), the control circuit 60 maintains the hover detection mode. If the maximum value RDHmax of the sensing data is greater than or equal to the threshold value RDHth (step S32; Yes), the control circuit 60 changes the detection mode from the hover detection mode to the touch detection mode.

[0115] If it is the touch detection mode (step S31; No), the control circuit 60 determines whether the maximum value RDTmax of each sensing data (RDT(n), where n is a natural number from 1 to N, and N is the number of sensor electrodes in the detection area SA) in the detection area SA is less than a predetermined threshold value RDTth (RDTmax<RDTth, step S34). The threshold value RDTth is stored in advance in the memory circuit 64.

[0116] If the maximum value RDTmax of the sensing data is equal to or greater than the threshold value RDTth (step S34; No), the control circuit 60 maintains the touch detection mode. If the maximum value RDTmax of the sensing data is less than the threshold value RDTth (step S34; Yes), the control circuit 60 changes the detection mode from the touch detection mode to the hover detection mode.

[0117] As described above, when the object to be detected is in contact with the detection surface of the sensor circuit 40, the sensing data becomes prominent at the position where the object to be detected is in contact with the detection surface of the sensor circuit 40. Therefore, by performing threshold judgment on the maximum value of the sensing data, it is possible to determine whether the object to be detected has contacted (touched) the detection surface of the sensor circuit 40.

[0118] The control circuit 60 sets the electrical resistance value of the DP circuit 22 so that the amplitude value Vpp of the drive signal is a value corresponding to the detection mode set in the detection mode setting process (step S3). Specifically, when the detection mode setting process (step S5) is set to the hover detection mode, the control circuit 60 sets the electrical resistance value of the DP circuit 22 so that the amplitude value Vpp of the drive signal is a first amplitude value (e.g., 6.8 V). When the detection mode setting process (step S5) is set to the touch detection mode, the control circuit 60 sets the electrical resistance value of the DP circuit 22 so that the amplitude value Vpp of the drive signal is a second amplitude value (e.g., 2.5 V) smaller than the first amplitude value.

[0119] After executing the detection mode setting process (step S3), the process returns to the main flow of the detection process shown in Fig. 15, and the detection device 1 executes a normal sensing operation (step S4). The AFE circuit 15 acquires the detection signal Rx from each sensor electrode 42, generates sensing data, and transmits it to the control circuit 60. The noise determination circuit 62 of the control circuit 60 executes the above-mentioned noise determination process based on the sensing data transmitted from the AFE circuit 15 (step S5).

[0120] Furthermore, the coordinate calculation circuit 63 executes coordinate calculation processing (step S6) based on the difference between the baseline data acquired by the baseline setting processing (step S2) and the sensing data.

[0121] Note that, although FIG. 15 shows an example in which the coordinate calculation process (step S6) is executed after the noise determination process (step S5), it is also possible to adopt an aspect in which the noise determination process (step S5) is executed after the coordinate calculation process (step S6), or an aspect in which the noise determination process (step S5) and the coordinate calculation process (step S6) are executed in parallel.

[0122] Next, the control circuit 60 determines whether or not the above-mentioned condition for performing frequency hopping (hereinafter also simply referred to as "frequency hopping condition") is met (step S7).

[0123] If the frequency hopping condition is not satisfied (step S7; No), the process proceeds to step S10.

[0124] When the frequency hopping condition is satisfied (step S7; Yes), the control circuit 60 sets the electrical resistance value of the DP circuit 22 to a value corresponding to the frequency of the square wave signal Tx after frequency hopping (step S8).The control circuit 60 also sets the fundamental frequency of the square wave signal Tx output from the AFE circuit 15 to the drive frequency after frequency hopping (step S9).

[0125] In addition, in Figure 15, an example is shown in which the drive frequency is set after the electrical resistance value of DP circuit 22 is set, but it is also possible to set the electrical resistance value of DP circuit 22 after setting the drive frequency, or to perform the setting of the electrical resistance value of DP circuit 22 and the setting of the drive frequency in parallel.

[0126] When setting the electrical resistance value of the DP circuit 22 in step S8, the control circuit 60 sets the electrical resistance value of the DP circuit 22 corresponding to the frequency of the square wave signal Tx after frequency hopping, for example, by referring to the above-mentioned DP control reference data. As a result, the electrical resistance value of the DP circuit 22 is controlled to an electrical resistance value corresponding to the square wave signal Tx after frequency hopping. More specifically, when the detection mode is the hover detection mode, the control circuit 60 sets the electrical resistance value of the DP circuit 22 so that, for example, the amplitude value Vpp of the drive signal is 6.8V. Also, when the detection mode is the touch detection mode, the control circuit 60 sets the electrical resistance value of the DP circuit 22 so that, for example, the amplitude value Vpp of the drive signal is 2.5V.

[0127] When the sensing operation of the detection device 1 is completed (step S10; Yes), the detection device 1 ends the sensing operation. The sensing operation ends, for example, when the power supply to the detection device 1 is stopped, or when a command to end the sensing operation is output from the processing device 110 to the detection device 1, etc. When the sensing operation of the detection device 1 is not completed (step S10; No), the operations from step S3 onwards are repeatedly executed.

[0128] In the configuration according to the above-described first embodiment, the control circuit 60 controls the amplitude value Vpp of the drive signal supplied from the drive signal generation circuit 20 to the peripheral electrode 41 and the shield electrode 44 in response to the sensing data output from the AFE circuit 15.

[0129] More specifically, in the detection mode setting process (step S3), when the current detection mode is the hover detection mode (first detection mode), the control circuit 60 maintains the hover detection mode (first detection mode) if the maximum value RDHmax of the sensing data RDH(n) of the multiple sensor electrodes 42 is less than a predetermined threshold value RDHth, and transitions to the touch detection mode (second detection mode) if the maximum value RDHmax is equal to or greater than the threshold value RDHth.

[0130] In addition, when the current detection mode is the touch detection mode (second detection mode), the control circuit 60 maintains the touch detection mode (second detection mode) if the maximum value RDTmax of the sensing data RDT(n) of the multiple sensor electrodes 42 is equal to or greater than a predetermined threshold value RDTth, and transitions to the hover detection mode (first detection mode) if the maximum value RDTmax is less than the threshold value RDTth.

[0131] Then, the control circuit 60 sets the electrical resistance value of the DP circuit 22 so that the amplitude value Vpp of the drive signal becomes a value according to the detection mode set in the detection mode setting process (step S3).

[0132] More specifically, when the detection mode set in the detection mode setting process (step S3) is the hover detection mode (first detection mode), the control circuit 60 controls the electrical resistance value of the DP circuit 22 so that the amplitude value Vpp of the drive signal becomes a first amplitude value (e.g., 6.8 V).

[0133] In addition, when the detection mode set in the detection mode setting process (step S3) is the touch detection mode (second detection mode), the control circuit 60 controls the electrical resistance value of the DP circuit 22 so that the amplitude value Vpp of the drive signal becomes a second amplitude value (e.g., 2.5 V) smaller than the first amplitude value.

[0134] In this way, in the hover detection mode (first detection mode), the amplitude value Vpp of the drive signal is controlled to be relatively small, and in the touch detection mode (second detection mode), the amplitude value Vpp of the drive signal is controlled to be relatively large. This makes it possible to suppress saturation of the sensing data at the contact position when the detected object contacts the detection surface of the sensor circuit 40, and a decrease in the accuracy of position determination due to a sensing data error caused by capacitive coupling between adjacent sensor electrodes.

[0135] In addition, in a configuration in which a sine wave signal is generated by filtering the square wave signal Tx output from the AFE circuit 15 and the sine wave signal is amplified to generate a drive signal, a DP circuit 22 is connected in series to the input path of the amplifier circuit 24. In addition, the control circuit 60 can set the fundamental frequency of the square wave signal Tx, and the higher the fundamental frequency of the square wave signal Tx, the larger the electrical resistance value of the DP circuit 22 becomes, and the lower the fundamental frequency of the square wave signal Tx, the smaller the electrical resistance value of the DP circuit 22 becomes.

[0136] This makes it possible to maintain the amplitude value Vpp of the drive signal constant (for example, 6.8 V in hover detection mode and 2.5 V in touch detection mode) even if, for example, a frequency hopping condition is met by the noise determination process and the fundamental frequency of the rectangular wave signal Tx (the frequency of the drive signal) is changed.

[0137] (Embodiment 2) 18A and 18B are diagrams illustrating a configuration example of an AFE circuit according to embodiment 2. Note that the block configuration of the detection circuit and the configuration and operation of the drive signal generation circuit are similar to those of embodiment 1 described above, and therefore detailed description thereof will be omitted here.

[0138] The AFE circuit operates as an integrating circuit with a negative feedback capacitance connected between the non-inverting input terminal and the output terminal of the differential amplifier circuit. As shown in Figures 18A and 18B, in the second embodiment, switch circuits SW1 and SW2 are provided to dynamically change the capacitance value of the negative feedback capacitance of the integrating circuit. The switch circuits SW1 and SW2 are on / off controlled by a control circuit 60.

[0139] 18A and 18B, the capacitance value of the negative feedback capacitance Cfb1 is, for example, 10 pF, and the capacitance value of the negative feedback capacitance Cfb2 is, for example, 35 pF, and in the hover detection mode (first detection mode), the switch circuit SW1 is controlled to be on and the switch circuit SW2 is controlled to be off, and in the touch detection mode (second detection mode), the switch circuit SW1 is controlled to be off and the switch circuit SW2 is controlled to be on. As a result, in the hover detection mode, the capacitance value of the negative feedback capacitance of the integrating circuit is controlled to 10 pF, and in the touch detection mode, the capacitance value of the negative feedback capacitance of the integrating circuit is controlled to 35 pF.

[0140] In the configuration according to the above-described second embodiment, the control circuit 60 controls the switch circuit SW1 to be on and the switch circuit SW2 to be off in the hover detection mode (first detection mode), so that the negative feedback capacitance Cfb1 is selectively connected between the non-inverting input terminal and the output terminal of the differential amplifier circuit.

[0141] In the configuration according to the above-described second embodiment, the control circuit 60 turns off the switch circuit SW1 and turns on the switch circuit SW2 in the touch detection mode (second detection mode), thereby selectively connecting the negative feedback capacitance Cfb2 between the non-inverting input terminal and the output terminal of the differential amplifier circuit.

[0142] In this way, in the hover detection mode (first detection mode), the negative feedback capacitance of the integrating circuit is controlled to be relatively small, and in the touch detection mode (second detection mode), the negative feedback capacitance of the integrating circuit is controlled to be relatively large. As a result, in the touch detection mode (second detection mode), the dynamic range of the AFE circuit 15a can be expanded more than in the hover detection mode (first detection mode), and saturation of the sensing data when the detected object contacts the detection surface of the sensor circuit 40 can be suppressed more than in the configuration of the first embodiment.

[0143] Although the preferred embodiment of the present invention has been described above, the present invention is not limited to such an embodiment. The contents disclosed in the embodiment are merely examples, and various modifications are possible within the scope of the present invention. Appropriate modifications made within the scope of the present invention naturally belong to the technical scope of the present invention. At least one of various omissions, substitutions, and modifications of components can be made within the scope of the gist of each of the above-mentioned embodiments and each modified example. [Explanation of symbols]

[0144] 1. Detection device 2. Detection circuit 3 First reference potential block 4 Second reference potential block 11 1st power supply circuit (POW1) 12. Isolated DC-DC Converter 13 Second power supply circuit (POW2) 15,15a AFE circuit 20 Drive signal generating circuit 21, 21a LPF (Low Pass Filter) circuit 22 DP (Digital Potentiometer) Circuit 23 Active filter circuit 23A 1st filter circuit 23B Second filter circuit 24, 24a Amplification circuit 40 Sensor circuit 41 Peripheral electrode (second electrode) 42 Sensor electrode (first electrode) 43 Substrate 44 Shield electrode 51 First Isolator 52 Second Isolator 60 Control circuit (MCU) 61 Readout circuit 62 Noise Judgment Circuit 63 Coordinate Calculation Circuit 110 Processing device (external processing device, HOST) 151 Readout circuit 152 ADC circuit 153 DSP circuit 250 Display Panel 260 Adhesive layer 270 Cover material 280 Adhesive layer BE Peripheral Area D+, D- signal line GND1 First reference potential GND2 Second reference potential Rx detection signal SA detection area Tx square wave signal VBUS power line

Claims

1. A plurality of sensor electrodes provided on a substrate; a peripheral electrode provided around a detection area in which the plurality of sensor electrodes are provided; a shield electrode provided on a surface opposite to a surface on which the sensor electrode and the peripheral electrode are provided; A sensor circuit having an AFE circuit that generates sensing data according to a distance between the sensor electrode and a nearby object based on a detection signal acquired from the sensor electrode; a drive signal generating circuit that generates a substantially sinusoidal drive signal and supplies the drive signal to the peripheral electrode and the shield electrode; a control circuit for controlling the AFE circuit and the drive signal generating circuit; Equipped with The control circuit includes: controlling an amplitude value of the drive signal in response to the sensing data; Detection device.

2. The control circuit includes: When a maximum value of the sensing data of the plurality of sensor electrodes is less than a predetermined threshold value, an amplitude value of the drive signal is controlled to be a first amplitude value; When a maximum value of sensing data of the plurality of sensor electrodes is equal to or greater than the threshold value, an amplitude value of the drive signal is controlled to be a second amplitude value smaller than the first amplitude value. The detection device according to claim 1 .

3. The drive signal generating circuit includes: an active filter circuit that filters a rectangular wave signal output from the AFE circuit to generate a sine wave signal; an amplifier circuit that amplifies the sine wave signal to generate the drive signal; Equipped with The control circuit includes: controlling the amplification factor of the amplifier circuit in response to the sensing data; 3. The detection device according to claim 2.

4. the amplifier circuit includes a digital potentiometer capable of adjusting an electrical resistance value; The control circuit includes: controlling the electrical resistance value of the digital potentiometer in response to the sensing data; 4. The detection device according to claim 3.

5. The control circuit is capable of setting a fundamental frequency of the rectangular wave signal, and controls an electrical resistance value of the digital potentiometer in accordance with the fundamental frequency of the rectangular wave signal.

5. The detection device according to claim 4.

6. The digital potentiometer is connected in series with the input path of the amplifier circuit.

6. The detection device according to claim 5.

7. The control circuit includes: The higher the fundamental frequency of the square wave signal, the smaller the electrical resistance value of the digital potentiometer is made; The lower the fundamental frequency of the square wave signal, the larger the electrical resistance value of the digital potentiometer is.

7. The detection device according to claim 6.

8. the control circuit operates with a first reference potential, which is a fixed potential, as a ground potential; the AFE circuit operates with a second reference potential, which is a periodically varying potential, as a ground potential; the drive signal generation circuit operates with the first reference potential as a ground potential, and supplies the drive signal to the AFE circuit with the second reference potential as the ground potential; 8. A detection device according to any one of claims 1 to 7.

9. a first isolator provided in a signal transmission path between the control circuit; a second isolator provided in a transmission path of the rectangular wave signal between the AFE circuit and the drive signal generation circuit; Equipped with 8. A detection device according to any one of claims 3 to 7.

10. The first isolator is a magnetic isolation type digital isolator.

10. The detection device according to claim 9.

11. The first isolator includes a first photocoupler that transmits a signal from the control circuit to the AFE circuit and a photocoupler that transmits a signal from the AFE circuit to the control circuit, the first photocoupler being connected in parallel.

10. The detection device according to claim 9.

12. The second isolator is a photocoupler.

10. The detection device according to claim 9.

13. the control circuit operates with a first reference potential, which is a fixed potential, as a ground potential; the AFE circuit operates with a second reference potential, which is a periodically varying potential, as a ground potential; the drive signal generation circuit operates with the first reference potential as a ground potential, and supplies the drive signal to the AFE circuit with the second reference potential as the ground potential; 10. The detection device according to claim 9.

14. the sensor circuit has a first detection mode for detecting a detectable object approaching a detection surface on which the sensor electrode and the peripheral electrode are provided, and for detecting a position of the detectable object when the detectable object is not in contact with the detection surface, and a second detection mode for detecting a position of the detectable object when the detectable object is in contact with the detection surface, The control circuit includes: When the sensing data is equal to or greater than a predetermined threshold, the detection mode of the sensor circuit is set to the first detection mode; When the sensing data is less than the threshold value, the detection mode of the sensor circuit is set to the second detection mode.

8. A detection device according to any one of claims 1 to 7.

15. The AFE circuit operates as an integrating circuit by connecting a negative feedback capacitance between the non-inverting input terminal and the output terminal of the differential amplifier circuit, The control circuit includes: In the first detection mode, the negative feedback capacitance is controlled to be relatively small; In the second detection mode, the negative feedback capacitance is controlled to be relatively large.

15. The detection device of claim 14.

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