Detection device

Abstract

To provide a detection device capable of better suppressing the occurrence of interference.SOLUTION: A detection device 1 includes: a detector 40 including first electrodes 421,... 42n and a shield electrode 44; an MCU 60; an AFE 15 that generates a rectangular wave Tx; and an active filter block 20 that is connected to the AFE 15 via a second isolator 16 and accepts as input the rectangular wave transmitted via the second isolator 16. The active filter block 20 has an LPF 23 and a DP 22, and is configured such that the frequency of a second reference potential GND2 can be changed according to an electrical resistance value of the LPF 23. The second reference potential GND2 output from the active filter block 20 is applied to the AFE 15 and the shield electrode 44. A first reference potential GND1 of the active filter block 20 is a fixed potential and the AFE 15 is configured such that the frequency of the rectangular wave Tx can be changed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] A detection device that detects the proximity of an object is known (for example, Patent Document 1). The detection device is provided with multiple detection electrodes and a shield electrode that is arranged around a detection area in which the multiple detection electrodes are provided, and an electrical signal is applied to the shield electrode. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 9,151,792 Summary of the Invention [Problem to be solved by the invention]

[0004] When a periodically varying potential that functions like an alternating current is applied to the shield electrode, the frequency of the periodically varying potential may interfere with the frequency of an external periodically varying potential.

[0005] The present disclosure has been made in view of the above-mentioned problems, and aims to provide a detection device that can better suppress the occurrence of interference. [Means for solving the problem]

[0006] a power supply circuit that generates a rectangular wave based on an external power supply; and a filter unit that is connected to the power supply circuit via an isolator and receives the rectangular wave transmitted through the isolator. The filter unit has a low-pass filter circuit and a digital potentiometer. A periodically varying potential output from the filter unit is provided as a reference potential for the power supply circuit and is also provided to the second electrode. The reference potential of the filter unit is a fixed potential. The power supply circuit is configured to be able to change the frequency of the rectangular wave it generates. The filter unit is controlled so that the digital potentiometer has an electrical resistance value corresponding to the frequency of the rectangular wave. The power supply circuit is configured to be able to change the frequency of the rectangular wave it generates. The frequency of the periodically varying potential is changed in response to a change in the frequency of the rectangular wave generated by the power supply circuit. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing the main configuration of the detection device. [Figure 2] FIG. 2 is a diagram illustrating an example of the configuration of an active filter block. [Figure 3] FIG. 3 is a schematic diagram showing the change in signal waveform caused by DP and LPF. [Figure 4] FIG. 4 is a schematic diagram showing the action of the LPF in the reference example. [Figure 5] FIG. 5 is a graph showing a schematic relationship between the frequency of a sine wave and the electrical resistance value of the DP according to the frequency. [Figure 6] FIG. 6 is a diagram showing an example of waveforms of a plurality of sine waves Wa1, Wa2, and Wa3 having different amplitudes. [Figure 7] FIG. 7 is a schematic diagram showing the flow of electricity in an electric field that occurs when the potential of the second electrode is higher than the potential of the first electrode. [Figure 8] FIG. 8 is a schematic diagram showing the flow of electricity in an electric field that occurs when the potential of the second electrode is lower than the potential of the first electrode. [Figure 9] FIG. 9 is a schematic graph showing an example of the detection signal intensity obtained from each of the first electrodes. [Figure 10] FIG. 10 is a block diagram illustrating an example of the functional configuration of the detection device. [Figure 11] FIG. 11 is a schematic diagram showing an example of a layered structure of a hover and touch panel display to which a detection device is attached. [Figure 12] FIG. 12 is a flowchart showing an example of a processing flow regarding the operation of the detection device. [Figure 13] FIG. 13 is a timing chart showing an example of the flow of operations of a detection device capable of frequency hopping. [Figure 14] FIG. 14 is a diagram showing the configuration of an LPF according to a modified example. [Figure 15] FIG. 15 is a schematic diagram showing an example of a configuration in which the detection unit 40 and the display panel 250 are overlapped. [Figure 16] FIG. 16 is a schematic diagram showing another example of a configuration in which the detection unit 40 and the display panel 250 are overlapped. DETAILED DESCRIPTION OF THE INVENTION

[0008] Each embodiment of the present disclosure will be described below with reference to the drawings. The disclosure is merely an example, and appropriate modifications that a person skilled in the art can easily conceive while maintaining the gist of the invention are naturally included within the scope of the present disclosure. Furthermore, to clarify the explanation, the drawings may show the width, thickness, shape, etc. of each part schematically compared to the actual embodiment, but these are merely examples and are not intended to limit the interpretation of the present disclosure. Furthermore, in this specification and each drawing, elements similar to those described above with reference to the previous drawings will be designated by the same reference numerals, and detailed descriptions may be omitted as appropriate.

[0009] FIG. 1 is a diagram showing the main configuration of a detection device 1. The detection device 1 includes a main body 10, an active filter block 20, and an MCU (Micro Controller Unit) 60. The detection device 1 is a detection device that detects the proximity of an object. Hereinafter, the term "hover detection" refers to the detection of the proximity of an object performed by the detection device 1.

[0010] The main body 10 includes a first isolator 11, a DC-DC converter 12, LDOs (Low Drop Out) 13 and 14, an AFE (Analog Front End) 15, a second isolator 16, a detection unit 40, and a third isolator 50.

[0011] The first isolator 11 insulates the power source EP from the main body 10 and supplies power to the main body 10 in response to the power supply from the power source EP. Specifically, the first isolator 11 has, for example, coils 11o and 11i. When power is supplied from the power source EP to the coil 11o, the coil 11o generates a magnetic field. The coil 11i is located within the range of influence of the magnetic field generated by the coil 11o. The coil 11i generates an induced electromotive force in response to the magnetic field generated by the coil 11o. The power generated in the coil 11o is supplied to the DC-DC converter 12.

[0012] The DC-DC converter 12 converts the DC voltage supplied from the coil 11i. The LDOs 13 and 14 are linear regulators interposed between the DC-DC converter 12 and the AFE 15, and adjust the output voltage to the AFE 15 to a more appropriate voltage. The AFE 15 is an integrated circuit including multiple analog circuits related to the various functions performed by the main body 10. The output voltage of the LDO 13 corresponds to the voltage required as the analog power supply (AVDD) of the AFE 15. The output voltage of the LDO 14 corresponds to the voltage required as the input / output power supply (IOVDD) of the AFE 15.

[0013] The AFE 15 is a circuit that operates in response to power supply from the power supply EP. The AFE 15 outputs a periodically varying potential having a periodic potential fluctuation pattern. In this embodiment, the AFE 15 outputs a square wave Tx as the periodically varying potential. The square wave Tx is transmitted via the second isolator 16 and output to the active filter block 20. The second isolator 16 generates a substantially similar square wave based on the insulation between the active filter block 20 and the main body 10 and the square wave Tx output from the AFE 15 and input to the second isolator 16, and outputs the generated square wave to the inverter circuit 21 of the active filter block 20. Specifically, the second isolator 16 has, for example, an input section 16i and an output section 16o. Signal transmission between the input section 16i and the output section 16o is performed using an optical isolation method, for example, using a photocoupler. However, magnetic isolation based on the same principle as the first isolator 11 or capacitive isolation based on the principle of a capacitor may also be used. In response to the square wave Tx being output from the AFE 15 to the output unit 16o, the input unit 16i generates a similar square wave.

[0014] Hereinafter, when a rectangular wave Tx is described, it refers to a rectangular wave as an example of a periodically varying potential output from the AFE 15. In Fig. 1, the waveform of the rectangular wave Tx output from the AFE 15 and the waveform of the rectangular wave output to the inversion circuit 21 via the second isolator 16 are schematically shown as waveform SB1.

[0015] The DC-DC converter 12, LDOs 13 and 14, AFE 15, and detector 40 in the main body 10 are electrically isolated from other components connected via the first isolator 11, the second isolator 16, and the third isolator 50. Components isolated from the main body 10, such as the coil 11o, the output unit 16o, and the other end 50o (described later), receive a reference potential from a first reference potential GND1. The first reference potential GND1 is, for example, a ground potential or a fixed potential maintained by a large electrode such as a solid electrode. Components isolated from the components connected to the first reference potential GND1, such as the DC-DC converter 12, the input unit 16i, and the one end 50i (described later), receive a reference potential from a second reference potential GND2. The second reference potential GND2 is a periodically fluctuating potential generated by the active filter block 20. The second reference potential GND2 periodically fluctuates relative to GND1.

[0016] Of the components of the main body 10, the detection section 40 and the third isolator 50 will be described in detail below. Next, the active filter block 20 will be described.

[0017] The active filter block 20 includes an inverting circuit 21, a DP (Digital Potentiometer) 22, an LPF (Low Pass Filter) 23, and an AMP (Amplifier) ​​24.

[0018] The inverter circuit 21 inverts the square wave output from the AFE 15 and applied to the active filter block 20 via the second isolator 16. The inverter circuit 21 may be, for example, a CMOS logic circuit that functions as an inverter using a NOT circuit, or may be an FPGA (Field Programmable Gate Array) configured to perform a similar function. In FIG. 1, the waveform of the square wave inverted by the inverter circuit 21 is schematically shown as waveform SB2. If it is not necessary to invert the polarity of the periodically varying potential applied to the active filter block 20, the inverter circuit 21 can be omitted.

[0019] The DP22 generates an intermediate wave based on the square wave inverted by the inverter circuit 21. The DP22 is a digital potentiometer (DP circuit) that generates an electrical resistance in response to a command from the MCU 60 on the output transmission path of the square wave inverted by the inverter circuit 21. The electrical resistance causes the square wave inverted by the inverter circuit 21 to become an intermediate wave. In FIG. 1, the waveform of the intermediate wave generated by the DP22 is schematically shown as waveform SB3.

[0020] FIG. 2 is a diagram illustrating an example configuration of the active filter block 20. The LPF 23 generates a sine wave based on the intermediate wave generated by the DP 22. Specifically, the LPF 23 is, for example, a Sallen-Key fourth-order active LPF, as shown in FIG. 2. As shown in FIG. 2, the LPF 23 has a first partial circuit 230A and a second partial circuit 230B. The first partial circuit 230A and the second partial circuit 230B are connected in series on the transmission path between the DP 22 and the AMP 24, from the DP 22 side toward the AMP 24 side, in this order: first partial circuit 230A, second partial circuit 230B.

[0021] The first partial circuit 230A has resistors 231A and 232A, an AMP233, and capacitance elements 234 and 235. The resistors 231A, 232A, and AMP233 are connected in series on a transmission path between the DP22 and the AMP24, from the DP22 side to the AMP24 side, in the order of resistor 231A, resistor 232A, and AMP233. An output terminal of the resistor 232A is connected to a positive input of the amplifier AMP233. A wiring branching from the output of AMP233 is connected to a negative input of AMP233. The AMP233 is, for example, an operational amplifier.

[0022] The capacitance elements 234 and 235 are capacitors that store electric charges. One end of the capacitance element 234 is connected to the signal transmission path between the resistor 231A and the resistor 232A. The other end of the capacitance element 234 is connected to the output path of the AMP 233. One end of the capacitance element 235 is connected to the signal transmission path between the resistor 232A and the AMP 233. The other end of the capacitance element 235 is connected to the first reference potential GND1.

[0023] The second partial circuit 230B has a configuration in which the resistors 231A and 232A of the first partial circuit 230A are replaced with resistors 231B and 232B. As electronic components, the resistors 231B and 232B are resistors provided for the purpose of obtaining a predetermined electrical resistance value, similar to the resistors 231A and 232A.

[0024] The resistors 231A, 232A, 231B, and 232B are assigned individual reference numerals because they do not necessarily have the same electrical resistance value and may be provided with different electrical resistance values ​​to achieve the desired function of the LPF 23. In other words, the resistors are assigned individual reference numerals to avoid the misunderstanding that resistors with the same reference numerals have the same electrical resistance value.

[0025] 2, an AMP221 is provided between the DP22 and the LPF23. An output terminal of the DP22 is connected to a positive input of the amplifier AMP221. A wiring branching from the output of the AMP221 is connected to a negative input of the AMP221. One end of a capacitance element 222 is connected to the wiring connecting the DP22 and the AMP221. The capacitance element 222 is a capacitor that accumulates electric charge. The other end of the capacitance element 222 is connected to a first reference potential GND1. A circuit section 220 including the DP22, the AMP221, and the capacitance element 222, the other end of which is connected to the first reference potential GND1, functions as an LPF.

[0026] The circuit section 220 and the first partial circuit 230A and second partial circuit 230B included in the LPF 23 cut out unnecessary high frequency components when converting a square wave into a sine wave, so that a sine wave can be generated from the square wave Tx transmitted by the second isolator 16 and output to the active filter block 20.

[0027] FIG. 3 is a schematic diagram showing changes in the signal waveform due to the DP 22 and LPF 23. The square wave output from the AFE 15 and output to the active filter block 20 via the second isolator 16 undergoes output adjustment processing based on the electrical resistance value indicated by the DP 22 to become an intermediate wave. The intermediate wave is then filtered by the LPF 23 to become a sine wave. Here, the frequency of the square wave Tx in this embodiment is not fixed. Specifically, the AFE 15 is configured to change the wavelength of the sine wave it outputs within a range from 140 kHz to 200 kHz. Example A shown in FIG. 3 shows a case where the wavelength of the sine wave is 200 kHz. Example B shown in FIG. 3 shows a case where the wavelength of the sine wave is 140 kHz.

[0028] FIG. 4 is a schematic diagram showing the operation of an LPF in a reference example. The "function of generating a sine wave from a square wave" performed by an LPF such as the DP22 is generally optimized for a single predetermined frequency. Therefore, for example, if a square wave of a frequency other than 200 kHz (e.g., 140 kHz) is input to an LPF optimized for 200 kHz, an undesirable signal wave SW may be generated, in which the time-series change in signal strength corresponding to the peaks of the sine wave amplitude exhibits a distorted change pattern Dis, as shown in FIG. 4.

[0029] In contrast, according to the embodiment, by controlling the DP22 to have an electrical resistance value corresponding to the frequency of the square wave Tx, it is possible to generate a more appropriate sine wave from square waves Tx of multiple frequencies, in which undesirable change patterns such as the distorted change pattern Dis described above are suppressed, as shown in Figure 3. In other words, in the active filter block 20 of the embodiment described with reference to Figures 1 and 2, the function of the LPF23 is static, but the electrical resistance value generated by the DP22 is dynamically changeable, so it is possible to generate a sine wave based on a square wave Tx of a frequency included in a predetermined frequency band (e.g., 140 kHz to 200 kHz). In Figure 1, the waveform of the sine wave generated by the LPF23 is schematically shown as waveform SB4.

[0030] 5 is a graph showing a relationship between the frequency of a sine wave and the electrical resistance of the DP 22 corresponding to the frequency. In this embodiment, the electrical resistance of the DP 22 is controlled to be higher as the frequency of the sine wave decreases, and lower as the frequency of the sine wave increases. Controlling the electrical resistance of the DP 22 in this manner allows the LPF 23 to stably output a sine wave. The sine wave in the description of FIG. 5 refers to the sine wave output from the AFE 15, transmitted to the active filter block 20 via the second isolator 16, and inverted by the inverter circuit 21.

[0031] FIG. 6 illustrates examples of waveforms of multiple sine waves Wa1, Wa2, and Wa3 with different amplitudes. FIG. 6 illustrates three sine waves, Wa1, Wa2, and Wa3, in descending order of amplitude relative to the center potential CoP. Controlling the electrical resistance value by the DP22 can also be used to control the amplitude of the sine wave generated by the LPF23. Specifically, the higher the electrical resistance value of the DP22, the smaller the amplitude of the sine wave. Therefore, by controlling the DP22 to have a relatively low electrical resistance within a range of electrical resistance values ​​of the DP22 that does not produce a distorted waveform like the distorted change pattern Dis described with reference to FIG. 4, the LPF23 can generate a sine wave with a relatively large amplitude, like the sine wave Wa1. Furthermore, by controlling DP22 so as to increase the electrical resistance value compared to the electrical resistance value of DP22 when sine wave Wa1 is generated, LPF23 can generate sine waves such as sine waves Wa2 and Wa3 whose amplitudes are relatively smaller than that of sine wave Wa1, depending on the level of the electrical resistance value of DP22.

[0032] The AMP24 is a buffer circuit that amplifies the sine wave output from the LPF 23. The sine wave amplified by the AMP24 is provided as a reference potential (GND) for the AFE 15. The sine wave amplified by the AMP24 is also provided as a reference potential (second reference potential GND2) for various components provided in the main body 10 via the transmission unit 30. For example, the reference potential of the DC-DC converter 12 and the input unit 16i described above is the second reference potential GND2. The sine wave amplified by the AMP24 is also provided to the second electrodes 411, 412 of the detection unit 40.

[0033] The detection unit 40 includes first electrodes 421, ..., 42n, second electrodes 411, 412, an insulator 43, and a shield electrode 44. The second electrode 411, the first electrodes 421, ..., 42n, and the second electrode 412 are arranged side by side on the insulator 43. Note that n in the first electrodes 421, ..., 42n is a natural number. For example, when n = 3, the first electrodes 421, ..., 42n refer to the first electrodes 421, 422, and 423, as shown in Figures 7 and 8 (described later). The insulator 43 is a film-like or plate-like member made of an insulating material, such as a resin film or a glass substrate. The shield electrode 44 is a film-like or plate-like electrode that faces the first electrodes 421, ..., 42n across the insulator 43. The second electrodes 411, 412 and the shield electrode 44 function as an active shield whose potential periodically fluctuates in response to changes in potential caused by a sine wave provided by the AMP 24. As shown in FIG. 1, the AFE 15 is connected to the first electrodes 421, ..., 42n. The self-capacitance of the first electrodes 421, ..., 42n generates an electrical signal output from each of the first electrodes 421, ..., 42n to the AFE 15. Therefore, the AFE 15 can acquire the electrical output generated in response to the self-capacitance of each of the first electrodes 421, ..., 42n as a detection signal Rx indicating the state of the detection unit 40. The area where the first electrodes 421, ..., 42n are provided functions as a detection area SA. The first electrodes 421, ..., 42n within the detection area SA function as detection electrodes for hover detection. The second electrodes 411, 412 arranged around the detection area SA function as shield electrodes for hover detection.

[0034] Fig. 7 is a schematic diagram showing a case where an object in proximity to detection unit 40 is at position P1. Fig. 8 is a schematic diagram showing a case where an object in proximity to detection unit 40 is at position P2. The strength of the detection signal obtained from each of first electrodes 421, 422, 423 changes between when the object in proximity to detection unit 40 is at position P1 and when the object in proximity is at position P2.

[0035] FIG. 9 is a schematic graph showing an example of the detection signal strength obtained from each of the first electrodes 421, 422, and 423. The numerical values ​​below each bar indicate the codes of the first electrodes 421, 422, and 423. The first example in FIG. 9 is a graph showing the detection signal strength obtained from each of the first electrodes 421, 422, and 423 when a nearby object is located at position P1. The second example in FIG. 9 is a graph showing the detection signal strength obtained from each of the first electrodes 421, 422, and 423 when a nearby object is located at position P2. The AFE 15 detects the degree of proximity of the nearby object to the insulator 43 based on the relationship between the detection signal strength obtained from each of the first electrodes 421, ..., 42n (e.g., the first electrodes 421, 422, and 423) and the amplitude applied to the second electrodes 411 and 412 at the timing when the detection signal indicating such detection signal strength was obtained. In this way, hover detection can detect the degree of proximity of a nearby object to the insulator 43. Of course, hover detection can also detect whether or not a nearby object has entered the electric field generated between the second electrodes 411, 412 and the first electrodes 421, ..., 42n.

[0036] As described above, the sine wave is applied to the ground (GND) of AFE15, and therefore, based on the input to the ground (GND), AFE15 can obtain information indicating the potential of the second electrodes 411, 412 at the timing of acquiring the detection signal from the first electrodes 421, ..., 42n.

[0037] The AFE 15 outputs data indicating the detection result of the hover detection to the MCU 60 via the third isolator 50. The third isolator 50 insulates the MCU 60 from the main body 10, generates a substantially similar electrical signal based on the electrical signal output from the AFE 15 and input to the MCU 60, and outputs the generated electrical signal to the MCU 60. Specifically, as shown in FIG. 1 , the third isolator 50 has one end 50i and the other end 50o. Signal transmission between the one end 50i and the other end 50o may be the same as or different from the signal transmission between the input unit 16i and the output unit 16o of the second isolator 16 described above. However, when the detection device 1 has a frequency hopping function (described later), the third isolator 50 is configured to be able to both transmit and output an input from the one end 50i to the other end 50o and transmit and output an input from the other end 50o to the one end 50i. In the following description, when the term "sensing data" is used, it refers to data that is output from the AFE 15 and input to the MCU 60 via the second isolator 16, and indicates the detection result of hover detection.

[0038] The MCU 60 outputs sensing data to an external information processing device (not shown). An example of the information processing device is a smartphone SoC (System on a Chip) equipped with the detection device 1 of the embodiment, but the information processing device is not limited to this and can be modified as appropriate.

[0039] Furthermore, the MCU 60 determines the electrical resistance value of the DP 22 according to the settings made in advance. Specifically, the MCU 60 includes a storage unit that stores information indicating the frequency of the square wave Tx output from the AFE 15. The storage unit is, for example, a register, but may also be another storage circuit that functions in a similar manner. The MCU 60 outputs a command OP to control the DP 22 so that the electrical resistance value corresponds to the frequency indicated by the information stored in the storage unit. The DP 22 exhibits an electrical resistance value according to the command OP.

[0040] In the embodiment, the frequency of the square wave Tx output from the AFE 15 is a specific frequency determined within the range of 140 kHz to 200 kHz as described above, but this is merely an example. The power supply frequency of the power supply EP is not limited to this and can be changed as appropriate.

[0041] The MCU 60 also performs noise determination processing on the sensing data and position determination (coordinate calculation processing) of a nearby object based on the sensing data. The noise determination processing refers to processing performed to determine how much noise is present in the sensing data. The coordinate calculation processing refers to calculation processing performed to determine the position of a nearby object relative to the insulator 43. In the coordinate calculation processing, for example, the position of a nearby object relative to the detection unit 40 can be derived in the X direction, Y direction, and Z direction shown in FIG. 11, which will be described later. The details of the noise determination processing and coordinate calculation processing are similar to those well known, and therefore will not be described in detail here.

[0042] 10 is a block diagram showing an example of the functional configuration of the detection device 1. The AFE 15 has a readout circuit 151, an ADC (Analog Digital Converter) 152, and a DSP (Digital Signal Processor) 153. The readout circuit 151 acquires a detection signal Rx from each of the first electrodes 421, ..., 42n. The ADC 152 converts the detection signal Rx acquired by the readout circuit 151 from an analog signal to a digital signal. The DSP 153 performs hover detection based on the detection signal Rx converted into a digital signal by the ADC 152. The AFE 15 outputs data indicating the result of the hover detection performed by the DSP 153 to the MCU 60 via the third isolator 50.

[0043] The MCU 60 has a readout unit 61, a noise determination unit 62, and a coordinate calculation unit 63. The readout unit 61 acquires sensing data. The noise determination unit 62 performs the above-mentioned noise determination process based on the sensing data acquired by the readout unit 61. The coordinate calculation unit 63 performs the above-mentioned coordinate calculation process based on the sensing data acquired by the readout unit 61. As shown in FIG. 10 , the reference potential of the MCU 60 is a first reference potential GND1.

[0044] The MCU 60 also holds DP control reference data 64. The DP control reference data 64 is data that associates the frequency of the square wave output from the AFE 15 and output to the active filter block 20 via the second isolator 16 with the electrical resistance value of the DP 22 corresponding to that frequency. More specifically, the DP control reference data 64 is, for example, data in the form of a table that associates the frequency with the electrical resistance on a one-to-one basis. The MCU 60 references the DP control reference data 64 and outputs a command OP to set the electrical resistance value of the DP 22 to the electrical resistance value corresponding to the frequency of the square wave output from the AFE 15 and output to the active filter block 20 via the second isolator 16.

[0045] The MCU 60 also has a function of changing the frequency of the square wave Tx output from the AFE 15. When the frequency of the square wave Tx output from the AFE 15 is changed, the MCU 60 resets the electrical resistance value of the DP 22 according to the changed frequency of the square wave Tx.

[0046] FIG. 11 is a schematic diagram showing an example of a layered structure of a hover & touch panel display 200 to which the detection device 1 is attached. Note that the first electrode 42 shown in FIG. 11 refers to first electrodes 421, ..., 42n. The detection unit 40 of the detection device 1 is provided so as to overlap with the touch panel 210 of the hover & touch panel display 200. The touch panel 210 performs touch detection. Touch detection refers to the detection of an external contact operation on the detection surface 201 of the hover & touch panel display 200 based on a change in electrostatic capacitance. A specific method of touch detection may be a so-called self-capacitance method (self) or a mutual capacitance method (mutual) that uses electrostatic capacitance generated between two electrodes.

[0047] 11 is disposed so as to be sandwiched between the display panel 250 and the detection unit 40 in the Z direction. The display panel 250 is a display panel that displays and outputs images. When the display panel 250 is a liquid crystal display device, a backlight is disposed on the opposite side of the touch panel 210 with the display panel 250 in between.

[0048] The arrangement direction of the second electrode 411, the first electrodes 421, ..., 42n, and the second electrode 412 described above is a direction perpendicular to the Z direction. In FIG. 11, the X direction and the Y direction are shown as directions perpendicular to the Z direction. The X direction and the Y direction are perpendicular to each other. The arrangement direction of the second electrode 411, the first electrodes 421, ..., 42n, and the second electrode 412 is, for example, at least one of the X direction and the Y direction. When the second electrode 411, the first electrodes 421, ..., 42n, and the second electrode 412 are aligned along the X direction and the Y direction, the first electrodes 421, ..., 42n are arranged in a matrix. In this case, two pairs of second electrodes 411 and second electrodes 412 are provided, and one pair of second electrodes 411 and second electrodes 412 face each other in the X direction, with the second electrodes 411 and first electrodes 421, ..., 42n arranged in a matrix pattern sandwiched between them, and another pair of second electrodes 411 and second electrodes 412 face each other in the Y direction, with the second electrodes 411 and first electrodes 421, ..., 42n arranged in a matrix pattern sandwiched between them.

[0049] In the configuration shown in FIG. 11 , 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 that constitute the active filter block 20 described above are mounted on the PCB 46. In FIG. 11 and other drawings, circuits 46a and 46b are illustrated as examples of the various circuits. The circuits 46a and 46b function as, for example, the AFE 15 and the MCU 60. The touch panel 210 also includes an FPC 215. The FPC 215 is provided with various circuits related to the operation of the touch panel 210. The display panel 250 also includes an FPC 255. The FPC 255 is provided with various circuits related to the operation of the display panel 250. The functions performed by the various circuits related to the operation of the touch panel 210 and the various circuits related to the operation of the display panel 250 are similar to known circuits, and therefore detailed description thereof will be omitted. The touch panel 210 and the detection unit 40 are adhered by, for example, an OCA (Optical Clear Adhesive) 260, but the OCA 260 is not essential and there may be a gap (air gap) at the position of the OCA 260. The FPC 255 is connected to the FPC 215. The FPC 255 is connected to the host 110. The host 110 is, for example, a circuit that functions as a host computer for a device including the detection unit 40, the touch panel 210, and the display panel 250. The device is, for example, a point-of-sale (POS) cash register terminal, but is not limited to this and may be another terminal capable of accepting touch operations and hover operations. The PCB 46 is connected to the host 110 via the FPC 47.

[0050] As described above, hover detection by the second electrode 411, the first electrodes 421, ..., 42n, and the second electrode 412 is performed using an electric field caused by capacitance. Touch detection by the touch panel 210 is also performed based on capacitance.

[0051] Here, it is assumed that the frequency of the electrical signal applied to the electrodes of touch panel 210 to generate capacitance in touch panel 210 is the same as the frequency of the sine wave applied to second electrodes 411, 412 by detection unit 40. In this case, touch panel 210 may malfunction due to the influence of the sine wave applied to second electrodes 411, 412 by detection unit 40.

[0052] Therefore, in the embodiment, the frequency of the sine wave applied to the second electrodes 411, 412 by the detection unit 40, i.e., the frequency of the square wave Tx that is the source of the sine wave, is made changeable, thereby making it possible to suppress malfunction of the touch panel 210 regardless of the frequency of the electrical signal employed by the touch panel 210. Such a change in the frequency of the square wave Tx may be referred to as frequency hopping.

[0053] 12 is a flowchart showing an example of a processing flow related to the operation of the detection device 1. First, the detection device 1 starts a sensing operation (step S1). Specifically, power is supplied from the power supply EP, and the components of the detection device 1, such as the AFE 15, operate. Next, a baseline scan is performed (step S2). Specifically, a detection signal is acquired assuming a state in which there is no object in proximity to the insulator 43, and a "detection signal in a state in which there is no object in proximity" is measured based on the detection signal. Therefore, during the processing of step S2, a square wave Tx is output from the AFE 15, a sine wave is generated by the active filter block 20, and a detection signal Rx is acquired from each of the first electrodes 421, ..., 42n by the MCU 60.

[0054] After the processing of step S2, sensing is performed (step S3). In the processing of step S3, a square wave Tx is output from the AFE 15, a sine wave is generated by the active filter block 20, and a detection signal Rx is acquired from each of the first electrodes 421, ..., 42n by the MCU 60. Based on the detection signal Rx acquired in the processing of step S3, the noise determination unit 62 performs the above-mentioned noise determination processing (step S4). Furthermore, based on the detection signal Rx acquired in the processing of step S3, the coordinate calculation unit 63 performs coordinate calculation processing (step S5). Note that, although steps S4 and S5 are described in this order in FIG. 12, the processing of step S4 and the processing of step S5 may be performed in any order, may be performed in parallel, or may be performed in reverse order. In the processing of step S4 and step S5, the MCU 60 performs noise determination processing and coordinate calculation processing based on the difference between the detection signal Rx acquired in the processing of step S2 (baseline scan) and the detection signal Rx acquired in the processing of step S3 (sensing).

[0055] Next, the MCU 60 checks whether a condition for performing frequency hopping is met (step S6). Specifically, the MCU 60 checks whether a signal including a command to perform frequency hopping has been input from an external information processing device connected via the FPC 255 described with reference to FIG. 11, for example. The hover & touch panel display 200 may also have a function for automatically meeting the condition for performing frequency hopping. For example, the detection device 1 or a circuit provided in the FPC 255 may have at least a first function, a second function, and a third function. The first function is a function for acquiring information indicating the frequency (first frequency) of an electrical signal applied to an electrode included in the touch panel 210. The second function is a function for acquiring information indicating the frequency (second frequency) of a sine wave applied to the second electrodes 411 and 412 by the detection unit 40. The third function is a function for outputting information indicating that the condition for performing frequency hopping is met to the MCU 60 when the first frequency and the second frequency are the same. In addition, when the detection device 1 performs the first, second, and third functions, a dedicated circuit may be provided to perform some or all of these functions, or the MCU 60 may perform some or all of these functions.

[0056] If the condition for performing frequency hopping is met in the process of step S6 (step S6; Yes), the MCU 60 causes the electrical resistance value of the DP 22 to correspond to the frequency after frequency hopping (step S7). In the process of step S7, the MCU 60, for example, refers to the above-mentioned DP control reference data 64 to identify the electrical resistance value corresponding to the frequency after frequency hopping. The MCU 60 sets the electrical resistance value of the DP 22. As a result, the electrical resistance value of the DP 22 becomes the electrical resistance value corresponding to the rectangular wave Tx after frequency hopping. That is, the DP 22 and the LPF 23 cooperate to generate a sine wave from a rectangular wave. The MCU 60 also changes the frequency of the rectangular wave Tx output from the AFE 15 to the frequency after frequency hopping (step S8). Specifically, the MCU 60 outputs a signal that functions as an instruction to the AFE 15 to change the frequency to the frequency after frequency hopping. The signal is transmitted via the third isolator 50 and output to the AFE 15. The AFE 15 changes the frequency of the square wave Tx to the frequency after frequency hopping in response to the signal. Note that, although steps S7 and S8 are described in the order of steps S7 and S8 in FIG. 12, the processing of steps S7 and S8 may be performed in any order, may be performed in parallel, or may be performed in reverse order. However, the processing of steps S7 and S8 is performed so that the electrical resistance value of the DP 22 has completely adapted to the changed frequency when the frequency of the square wave Tx becomes the changed frequency due to frequency hopping.

[0057] If the sensing operation of the detection device 1 has ended (step S9; Yes), the detection device 1 ends its operation. Examples of cases in which the sensing operation ends include when power supply from the power source EP is no longer supplied, or when a command to end the sensing operation is output to the hover & touch panel display 200 from an external information processing device connected via the FPC 255. If the sensing operation of the detection device 1 has not ended (step S9; No), the process returns to step S3.

[0058] If the condition for performing frequency hopping is not met in the process of step S6 (step S6; No), the process proceeds to the process of step S9. That is, in this case, the process of step S7 and the process of step S8 are not performed.

[0059] It should be noted that, not only the relationship between the frequency of the electrical signal provided to the electrodes of the touch panel 210 to generate capacitance in the touch panel 210 and the frequency of the sine wave provided to the second electrodes 411, 412 by the detection unit 40, but also periodic electrical changes occurring externally may cause noise in the detection signal Rx of the detection unit 40. When such noise occurs, frequency hopping can be performed to reduce the noise caused by the relationship between the periodic electrical change and the frequency of the sine wave provided to the second electrodes 411, 412 by the detection unit 40.

[0060] FIG. 13 is a timing chart showing an example of the operation flow of the detection device 1 capable of frequency hopping. The operation of the detection device 1 is such that the processing flow is determined for each repetition period Cy. First, a clock signal (V-Sync) indicating the start of the repetition period Cy is output at a predetermined cycle. In FIG. 13, the clock signal is output at times T1 and T2. Below, the processing flow within the repetition period Cy starting from time T1 will be described.

[0061] Starting from timing T1, a sensing operation (Sensing) corresponding to the processing in step S3 described above is performed during a period Pe1 from timing T1 to the start of a period Pe2 when an interrupt signal (IRQ) indicating the end of the sensing operation is generated.

[0062] Between the end of the period Pe2 and timing T2, periods Pe3, Pe4, Pe5, Pe6, and Pe7 occur sequentially. The period Pe3 is a period during which the AFE 15 reads the detection signal Rx (AFE Read). The period Pe4 is a period during which the noise determination process corresponding to the process of step S4 described above and the coordinate calculation process corresponding to the process of step S5 described above are performed in parallel. The period Pe5 is a period during which, when frequency hopping is performed, a command is output (information is written) to reflect in the DP 22 the electrical resistance value corresponding to the frequency of the rectangular wave Tx after frequency hopping. The period Pe6 is a period during which, when frequency hopping is performed, an output is performed to the AFE 15 to change the frequency of the rectangular wave Tx to the frequency after frequency hopping. The period Pe7 is a blank period from the end of the period Pe6 to timing T2.

[0063] Starting from timing T2, the above-described periods Pe1, ..., Pe7 are repeated again. Thereafter, the above-described periods Pe1, ..., Pe7 are repeated again every time a clock signal (V-Sync) indicating the start of a repetition period Cy is output at a predetermined cycle.

[0064] The frequency of the square wave Tx before and after the change in frequency hopping is, for example, within a range of 140 kHz to 200 kHz, but is not limited to this and the range can be changed as appropriate. To give a more specific example, at the time of processing step S1, the initial frequency of the square wave Tx is set to 200 kHz. This initial frequency can be changed within a range of 140 kHz to 200 kHz by frequency hopping.

[0065] As described above, according to the embodiment, the detection device 1 includes a detection unit (detection unit 40) including a plurality of first electrodes (first electrodes 421, ..., 42n) arranged in a predetermined direction (e.g., at least one of the X direction and the Y direction) and a plurality of second electrodes (second electrodes 411, 412) arranged around a detection area (detection area SA) in which the plurality of first electrodes are arranged, a detection circuit (MCU 60) that detects the proximity of an external object to the detection unit based on an electrical change occurring in the first electrodes, a power supply circuit (AFE 15) that generates a square wave (square wave Tx) based on an external power supply, and a filter unit (active filter block 20) ​​connected to the power supply circuit via an isolator (second isolator 16) and receiving the square wave transmitted through the isolator. The filter unit includes a low-pass filter circuit (LPF 23) and a digital potentiometer (DP 22). The periodically varying potential (second reference potential GND2) output from the filter unit is provided as a reference potential for the power supply circuit and is also provided to the plurality of second electrodes. The reference potential of the filter unit is a fixed potential. The power supply circuit is configured to be able to change the frequency of the rectangular wave (rectangular wave Tx) it generates. The filter unit is configured to be able to change the frequency of the periodically varying potential depending on the electrical resistance value of the digital potentiometer.

[0066] As a result, even if an external electrical event interferes with the potential of multiple first electrodes (first electrodes 421, ..., 42n), the frequency of the rectangular wave (rectangular wave Tx) generated by the power supply circuit (AFE15) is changeable, and the filter section (active filter block 20) ​​is changeable in frequency of the periodically varying potential according to the electrical resistance value of the digital potentiometer (DP22). Therefore, by changing the frequency of the rectangular wave and the frequency of the periodically varying potential, the occurrence of interference can be better suppressed.

[0067] The filter unit (active filter block 20) ​​also includes an amplifier circuit (AMP24) that amplifies the periodically varying potential generated by the low-pass filter circuit (LPF23) and supplies the amplified potential to the power supply circuit (AFE15) and the second electrodes (second electrodes 411, 412). This allows the periodically varying potential output from the filter unit to be further amplified.

[0068] Furthermore, the periodically varying potential (second reference potential GND2) output from the filter unit (active filter block 20) ​​is a sine wave that the filter unit generates based on the square wave generated by the power supply circuit (AFE 15) and transmitted via the isolator (second isolator 16). This enables more accurate detection of the proximity of an external object based on the sine wave.

[0069] The frequency band cut by the low-pass filter circuit (LPF23) corresponds to the electrical resistance value of the digital potentiometer (DP22). This allows the frequency components cut by the filter unit (active filter block 20) ​​to be appropriately set according to the setting of the electrical resistance value of the digital potentiometer. In other words, the accuracy with which the periodically varying potential (second reference potential GND2) output from the filter unit is converted into a sine wave can be further improved.

[0070] The detection device 1 also has a setting circuit (MCU60) that sets the frequency of the square wave (square wave Tx) and the frequency of the periodically varying potential (second reference potential GND2) output from the filter unit (active filter block 20). This setting circuit makes it easier to perform settings to better suppress the occurrence of interference. The reference potential of this setting circuit is a fixed potential (first reference potential GND1).

[0071] (Variation) Next, a modified example of the embodiment will be described with reference to Fig. 14. In the description of the modified example, the same components as those in the embodiment will be denoted by the same reference numerals, and the description thereof may be omitted.

[0072] Fig. 14 is a diagram showing the configuration of an LPF 23A according to a modified example. In this modified example, the DP 22, the LPF 23, and the components provided between the DP 22 and the LPF 23, among the components of the active filter block 20 described with reference to Fig. 2, are replaced with the LPF 23A shown in Fig. 14.

[0073] The LPF 23A includes a first partial circuit 230C and a second partial circuit 230D. The first partial circuit 230C and the second partial circuit 230D are connected in series on the transmission path between the inverting circuit 21 and the AMP 24, arranged in the order of the first partial circuit 230C and the second partial circuit 230D, from the inverting circuit 21 side toward the AMP 24 side.

[0074] The first partial circuit 230C has a configuration in which the resistors 231A and 232A of the first partial circuit 230A are replaced with DPs 22A and 22B. The second partial circuit 230D has a configuration in which the resistors 231B and 232B of the first partial circuit 230A are replaced with DPs 22C and 22D. Like the DP22, the DPs 22A, 22B, 22C, and 22D are each configured so that their electrical resistance values ​​can be changed individually under the control of the MCU 60.

[0075] The reason why the DPs 22A, 22B, 22C, and 22D are each assigned a different reference numeral is that they do not necessarily have the same electrical resistance value, and that the LPF 23A may have different electrical resistance values ​​in order to perform a desired function. In other words, the components assigned the same reference numeral are assigned different reference numerals so as not to be mistaken for components having the same electrical resistance value.

[0076] According to a modified example, a digital potentiometer (e.g., DP22A, 22B, 22C, 22D) is provided as an electrical resistor constituting a Sallen-Key filter circuit (e.g., LPF 23A) provided as an LPF. This allows the frequency components cut by the Sallen-Key filter circuit to be optimized based on the frequency of the square wave Tx. In other words, it becomes easier to further improve the accuracy of sine wave generation by cutting frequency components using the Sallen-Key filter circuit.

[0077] Furthermore, according to the configuration shown in FIG. 14, the electrical resistance values ​​of the DPs 22A, 22B, 22C, and 22D can be set individually, which further facilitates increasing the accuracy of generating a sine wave by cutting frequency components with the LPF 23A.

[0078] 11, two or more of the detection unit 40, the touch panel 210, and the display panel 250 may be integrated. For example, in the hover & touch panel display 200 illustrated in FIG. 11, the detection unit 40 and the touch panel 210 are provided as out-cells relative to the display panel 250, but the detection unit 40 may be overlaid on a so-called in-cell touch detection display panel in which the display panel 250 and the detection unit 40 are integrated. Alternatively, the detection unit 40 and the touch panel 210 may be integrated and overlaid on the display panel 250.

[0079] Fig. 15 is a schematic diagram showing an example of a configuration in which the detection unit 40 and the display panel 250 are overlapped. As shown in Fig. 15, the configuration including the detection unit 40 can also be a configuration in which the touch panel 210 and the FPC 215 described with reference to Fig. 11 are omitted.

[0080] 16 is a schematic diagram showing another example of a configuration in which the detection unit 40 and the display panel 250 are stacked on top of each other. As shown in FIG. 16, the FPC 255 may be connected to the PCB 46. In this case, the FPC 47 further includes wiring for transmitting signals generated between the display panel 250 and the host 110.

[0081] Furthermore, in the above-described embodiment, the MCU 60 functions as a detection circuit and a setting circuit, but the circuit functioning as the detection circuit and the circuit functioning as the setting circuit may be provided separately. Furthermore, a circuit that integrates the functions of the AFE 15, the various functions of the active filter block 20, and the functions of the MCU 60 may be mounted on the FPC 70. In this case, the PCB 46 and FPC 47 in FIG. 11 and the like may be omitted, and the FPC 70 and FPC 255 may be joined to connect to the host 110.

[0082] Furthermore, other effects and advantages brought about by the aspects described in this embodiment that are clear from the description in this specification or that can be appropriately thought of by a person skilled in the art are naturally understood to be brought about by the present disclosure. [Explanation of symbols]

[0083] 1. Detection device 15 AFE 16 Second isolator 20 Active Filter Blocks 22 Digital Potentiometer 22A, 22B, 22C, 22D DP 23 LPF 24 AMP 40 Detector 60 MCU 411,412 2nd electrode 42,421,422,423,42n 1st electrode GND1 First reference potential GND2 Second reference potential

Claims

1. a detection unit including a plurality of first electrodes arranged in a predetermined direction and a second electrode facing the plurality of first electrodes with an insulating film interposed therebetween; a detection circuit that detects the proximity of an external object to the detection unit based on an electrical change occurring in the first electrode; a power supply circuit that generates a square wave based on an external power supply; a filter unit connected to the power supply circuit via an isolator and receiving the rectangular wave transmitted via the isolator; the filter unit includes a low-pass filter circuit and a digital potentiometer; a periodically varying potential output from the filter section is provided as a reference potential of the power supply circuit and is also provided to the second electrode; the reference potential of the filter unit is a fixed potential; the power supply circuit is configured to be able to change the frequency of the square wave it generates; the filter unit is controlled so that the digital potentiometer has an electrical resistance value corresponding to the frequency of the square wave; the power supply circuit is configured to be able to change the frequency of the rectangular wave to be generated; The frequency of the periodically varying potential is changed in response to a change in the frequency of the rectangular wave generated by the power supply circuit. Detection device.

2. the filter unit includes an amplifier circuit that amplifies the periodically varying potential and applies the amplified potential to the power supply circuit and the second electrode. The detection device according to claim 1 .

3. the periodically varying potential is a sine wave generated by the filter unit based on the rectangular wave; 3. The detection device according to claim 1 or 2.

4. The frequency band cut by the low-pass filter circuit depends on the electrical resistance value of the digital potentiometer.

4. A detection device according to any one of claims 1 to 3.

5. the digital potentiometer is provided as an electrical resistor constituting a Sallen-Key filter circuit provided as the low-pass filter circuit, 5. A detection device according to any one of claims 1 to 4.

6. a setting circuit for setting the frequency of the rectangular wave and the frequency of the periodically varying potential; the reference potential of the setting circuit is the fixed potential; 6. A detection device according to any one of claims 1 to 5.

Images