Electrostatic capacitance detection device and input device

Abstract

The first detection signal generation unit (10) has detection nodes (N1-1, N1-2) connected one-to-one with the detection electrodes (Ea-1, Ea-2). Charge is supplied from the detection nodes (N1-1, N1-2) to the detection electrodes (Ea-1, Ea-2) via the second wiring (W2-1, W2-2) so that the voltage of the detection nodes (N1-1, N1-2) vibrates according to the AC voltage (Vas), generating a first detection signal (D1-1, D1-2) corresponding to the supplied charge. First filters (F1-1, F1-2) are provided on the first paths (P1-1, P1-2) from the first detection signal generation unit (10), the AC output node (N3) to each branch of the plurality of first wirings (W1). The phase difference signal generation unit (40-1) generates a phase difference signal (P1) corresponding to the phase difference between the first detection signal (D1-1) and the AC voltage (Vas).

Description

Technical Field

[0001] This invention relates to an electrostatic capacitance detection device and an input device. Background Technology

[0002] In self-capacitance capacitive sensors that detect the electrostatic capacitance between an object such as a finger and a detection electrode, parasitic capacitance between an object other than the object and the detection electrode becomes an error in the detection result. As a method to reduce such error, a method is known to arrange a shielding electrode (also called an active shield) having the same potential as the detection electrode around the detection electrode. Patent Document 1 below describes a technique for further reducing the influence of the aforementioned parasitic capacitance in an electrostatic capacitance detection device equipped with a shielding electrode.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: International Publication No. 2018 / 116706

[0006] Patent Document 2: Japanese Patent Application Publication No. 5-288790 Summary of the Invention

[0007] -The problem the invention aims to solve-

[0008] However, when the wiring board with sensing electrodes (detection electrodes, shielding electrodes) and the wiring board with electronic circuitry for detecting electrostatic capacitance are placed in remote locations, wiring must be carried out on these wiring boards via cables, which can easily lead to malfunctions and poor operation due to broken wires.

[0009] When a wire connected to the detection electrode breaks, electrostatic capacitance cannot be detected, making it easy to identify the break. On the other hand, when a portion of multiple wires connected to the shielding electrode breaks, although it is susceptible to external noise or noise radiation, the electrical continuity between the shielding electrode and the electronic circuit is maintained, thus the electrostatic capacitance detection result is less likely to be abnormal. Therefore, there is a disadvantage that the occurrence of a break cannot be easily identified based on the electrostatic capacitance detection result.

[0010] The present invention was made in view of the above circumstances, and its object is to provide an electrostatic capacitance detection device capable of easily identifying a portion of a broken wire in a plurality of wirings connected to a shielding electrode, and an input device having such an electrostatic capacitance detection device.

[0011] -Methods for solving problems-

[0012] The first aspect of this invention is an electrostatic capacitance detection device, which detects the electrostatic capacitance between a detection electrode positioned close to a shielding electrode and an object. The device comprises: an AC voltage output unit that outputs an AC voltage to the shielding electrode via a plurality of first wirings; a first detection signal generation unit having a plurality of detection nodes connected one-to-one to a plurality of the detection electrodes via a plurality of second wirings respectively positioned close to the first wirings, supplying charge from the detection nodes to the detection electrodes via the second wirings, such that the voltage of the detection nodes oscillates according to the AC voltage, generating a plurality of first detection signals corresponding to the charges supplied from the plurality of detection nodes; a plurality of first filters disposed on a plurality of first paths from the AC output node where the AC voltage is output from the AC voltage output unit to each branch of the plurality of first wirings; and at least one phase difference signal generation unit that generates a phase difference signal corresponding to the phase difference between a first detection signal and the AC voltage.

[0013] According to the electrostatic capacitance detection device of the first viewpoint, since the first filters are respectively provided in the multiple first paths from the AC output node to each branch of the multiple first wirings, the number of first filters connected in parallel between the AC output node and the shielding electrode changes when a portion of the multiple first wirings is broken. As a result, the frequency characteristics from the AC output node to the shielding electrode change, and the frequency characteristics from the AC output node to the output node of the first detection signal also change. Therefore, the phase difference between the AC voltage output at the AC output node and the AC component included in the first detection signal changes. Since the phase difference signal generated by the phase difference signal generation unit is a signal corresponding to the phase difference between a first detection signal and the AC voltage, the change in the phase difference between the first detection signal and the AC voltage caused by a partial break in the multiple first wirings can be easily determined based on the phase difference signal.

[0014] Preferably, the first filter is a low-pass filter having a cutoff frequency higher than the frequency of the AC voltage.

[0015] Therefore, high-frequency external noise propagating from the first wiring can be attenuated in the first filter.

[0016] Preferably, a plurality of second filters are provided in a plurality of second paths between the plurality of second wirings and the plurality of detection nodes, wherein the second filters are low-pass filters having a cutoff frequency higher than the frequency of the AC voltage.

[0017] Therefore, high-frequency external noise propagating from the second wiring can be attenuated in the second filter.

[0018] Preferably, the electrostatic capacitance detection device of the first viewpoint described above includes: a sine wave generation unit that generates a sine wave signal; and at least one second detection signal generation unit that generates a second detection signal corresponding to the amplitude of the AC component included in the first detection signal; the AC voltage output unit outputs the AC voltage corresponding to the sine wave signal; the second detection signal generation unit includes: a first multiplication operation unit that multiplies the sine wave signal with the first detection signal; and a first low-pass filter that attenuates the high-frequency components of the output signal of the first multiplication operation unit; the phase difference signal generation unit includes: a first delay unit that delays the phase of the sine wave signal by 90 degrees; a second multiplication operation unit that multiplies the sine wave signal delayed by the first delay unit with the first detection signal; and a second low-pass filter that attenuates the high-frequency components of the output signal of the second multiplication operation unit; the second detection signal generation unit generates the second detection signal corresponding to the output signal of the first low-pass filter; and the phase difference signal generation unit generates the phase difference signal corresponding to the output signal of the second low-pass filter.

[0019] According to this structure, when the phase difference between the AC component included in the first detection signal and the sine wave signal is small, the rate of change of the phase difference signal corresponding to the output signal of the second low-pass filter is larger than that of the second detection signal, corresponding to the change in phase difference. Therefore, the change in the phase difference between the first detection signal and the AC voltage caused by a partial break in the plurality of first wirings can be easily determined based on the change in the phase difference signal.

[0020] Furthermore, according to this structure, both the second detection signal and the phase signal can be efficiently generated based on a sinusoidal signal.

[0021] Preferably, the electrostatic capacitance detection device of the first viewpoint described above has a second delay section that delays the sinusoidal signal, the AC voltage output section outputs an AC voltage corresponding to the sinusoidal signal delayed by the second delay section, and the delay amount of the second delay section is adjusted so that the output signal of the second low-pass filter is minimized.

[0022] According to this structure, when the output signal of the second low-pass filter is minimized, the phase difference between the AC component included in the first detection signal and the sine wave signal becomes close to zero, thus improving the detection sensitivity of the electrostatic capacitance based on the second detection signal.

[0023] Furthermore, according to this structure, by observing the change in the phase difference signal corresponding to the change in the delay amount of the second delay portion, it is possible to adjust the phase difference between the AC component included in the first detection signal and the sine wave signal to be close to zero.

[0024] Preferably, the first detection signal generation unit includes: at least one charge amplifier that supplies the charge to the detection node so that the voltage of the detection node oscillates according to the AC voltage and outputs a signal corresponding to the supplied charge; at least one differential amplifier that outputs a signal corresponding to the difference between the output signal of the charge amplifier and the AC voltage; and at least one analog-to-digital converter that converts the output signal of the differential amplifier into a digital signal and outputs it as the first detection signal.

[0025] According to this structure, the first detection signal can be generated using a simple structure that includes the charge amplifier, the differential amplifier, and the analog-to-digital converter.

[0026] Preferably, the AC voltage output unit, the first detection signal generation unit, the second detection signal generation unit, the phase difference signal generation unit, and the sine wave generation unit are disposed in one or more integrated circuits, and the first filter and the second filter are composed of one or more components different from the one or more integrated circuits.

[0027] Therefore, the first filter and the second filter, which have relatively large time constants that are difficult to achieve in integrated circuits, can be constructed from the one or more components.

[0028] Preferably, the first filter includes: a first inductor disposed in the first path; and two first capacitors disposed between the nodes at both ends of the first inductor and ground, and the second filter includes: a second inductor disposed in the second path; and two second capacitors disposed between the nodes at both ends of the second inductor and ground.

[0029] According to this structure, in the first filter, external noise from the first wiring side with higher impedance is easily attenuated, and in the second filter, external noise from the second wiring side with higher impedance is easily attenuated.

[0030] Preferably, the first filter includes: a first resistor disposed in the first path; and two first capacitors disposed between the nodes at both ends of the first resistor and ground. The second filter includes: a second resistor disposed in the second path; and two second capacitors disposed between the nodes at both ends of the second resistor and ground.

[0031] According to this structure, in the first filter, external noise from the first wiring side with higher impedance is easily attenuated, and in the second filter, external noise from the second wiring side with relatively higher impedance is easily attenuated.

[0032] Preferably, the AC voltage output unit, the first detection signal generation unit, the plurality of first filters, and the at least one phase difference signal generation unit are disposed on a common first wiring substrate, the shielding electrode and the plurality of detection electrodes are disposed on one or more second wiring substrates, the first wiring substrate and the one or more second wiring substrates are connected by one or more wiring cables, and the first wiring and the second wiring are respectively included in the wiring cables.

[0033] According to this structure, it is possible to easily determine, based on the phase difference signal, the change in the phase difference between the first detection signal and the AC voltage caused by a break in one or more of the wiring cables, of a portion of the plurality of first wirings.

[0034] Preferably, the AC voltage output section outputs an AC voltage that overlaps with a DC voltage greater than half the amplitude.

[0035] Therefore, a circuit that receives the AC voltage can be operated using a single power supply.

[0036] A second aspect of the present invention is an input device that inputs information corresponding to the proximity of an object, comprising: a plurality of detection electrodes that change the electrostatic capacitance between the object and the object as the object approaches; a shielding electrode disposed close to the plurality of detection electrodes; and the electrostatic capacitance detection device of the first aspect described above, which detects the electrostatic capacitance between the object and the plurality of detection electrodes respectively.

[0037] --Invention Effects--

[0038] According to the present invention, a capacitance detection device capable of easily identifying a portion of a broken wire in a plurality of wirings connected to a shielding electrode, and an input device having such a capacitance detection device, are provided. Attached Figure Description

[0039] Figure 1 This is a diagram illustrating an example of the structure of the input device involved in this embodiment.

[0040] Figure 2 This is a diagram illustrating an example of the structure of the electrostatic capacitance detection device according to this embodiment.

[0041] Figures 3A-3B This is a diagram illustrating an example of the structure of the first and second filters.

[0042] Figure 4 This is a diagram illustrating an example of the structure of the second signal generation unit and the phase difference signal generation unit.

[0043] Figure 5 This is a diagram used to illustrate the state of a broken portion of a plurality of first wirings connected to the shielding electrode.

[0044] Figure 6 This is a diagram showing a modified example of the phase difference signal generation unit. Detailed Implementation

[0045] Figure 1 This is a diagram illustrating an example of the structure of the input device involved in this embodiment. Figure 1 The input device 1 shown has two detection electrodes Es-1 and Es-2, a shielding electrode Ea disposed close to the detection electrodes Es-1 and Es-2, a capacitance detection device 3, a processing unit 4, a storage unit 5, and an interface unit 6.

[0046] The input device 1 described in this embodiment detects the electrostatic capacitance between the detection electrode Es-i and the object 9 when an object 9, such as a finger or pen, approaches the detection electrode Es-i (where i represents an integer of 1 or 2). Based on this detection result, it inputs information corresponding to the proximity of the object 9. For example, based on the electrostatic capacitance detection result, the input device 1 obtains information such as whether the object 9 is close to the detection electrode Es-i, and information related to the distance between the detection electrode Es-i and the object 9. For example, the input device 1 is applied to user interface devices such as touch sensors and touchpads. Furthermore, in this specification, "proximity" means being nearby and does not limit the contact between objects that are close to each other.

[0047] The detection electrode Es-i generates electrostatic capacitance between itself and the object 9, such as a finger or pen, which is a conductor. The shielding electrode Ea is disposed close to the detection electrode Es-i. The detection electrode Es-i is disposed in a detection area accessible to the object 9. The surface of the detection area is covered, for example, by an insulating layer, and the detection electrode Es-i is disposed on the lower side of the layer. The shielding electrode Ea is an electrostatic shield used to prevent electrostatic coupling between the detection electrode Es-i and objects other than the object 9, and is disposed, for example, on the lower side of the detection area than the detection electrode Es-i.

[0048] like Figure 1 As shown, a parasitic capacitance component Crg is formed between the detection electrode Es-i and the object 9. A parasitic capacitance component Crs is formed between the shielding electrode Ea and the detection electrode Es. A parasitic capacitance component Csg is formed between the shielding electrode Ea and ground.

[0049] The electrostatic capacitance detection device 3 detects the electrostatic capacitance (hereinafter sometimes referred to as "detection object capacitance Crg") of the capacitance components Crg formed between the detection electrodes Es-1 and Es-2 and the object 9, and outputs second detection signals D2-1 and D2-2 representing the detection results.

[0050] Furthermore, as described later, the electrostatic capacitance detection device 3 generates a phase difference signal P-1 corresponding to the phase difference between the first detection signal D1-1 and the AC voltage Vas, and a phase difference signal P-2 corresponding to the phase difference between the first detection signal D1-2 and the AC voltage Vas.

[0051] like Figure 1 As shown, the electrostatic capacitance detection device 3 is connected to the detection electrode Es-1 and the shielding electrode Ea via cable 2-1, and to the detection electrode Es-2 and the shielding electrode Ea via cable 2-2. Inside cable 2-1, the first wiring W1-1 connected to the shielding electrode Ea and the second wiring W2-1 connected to the detection electrode Es-1 are arranged close together. Inside cable 2-2, the first wiring W1-2 connected to the shielding electrode Ea and the second wiring W2-2 connected to the detection electrode Es-1 are arranged close together. In the following description, the first wiring W1-1 and W1-2 are sometimes referred to as "first wiring W1" without distinction.

[0052] The processing unit 4 is a circuit that controls the overall operation of the input device 1, and may include, for example, one or more processors (CPU, DSP, etc.) that process according to the instruction code of the program stored in the storage unit 5. Furthermore, the processing unit 4 may also include dedicated hardware (ASIC, FPGA, etc.) configured to perform specific functions. The processing of the processing unit 4 can be implemented either by the processor executing the program's instruction code or by at least a portion of it being implemented using dedicated hardware.

[0053] The processing unit 4 performs the following processing based on the second detection signals D2-1 and D2-2 output from the electrostatic capacitance detection device 3: determining whether the object 9 is close to the detection electrodes Es-1 and Es-2, calculating the distance between the object 9 and the detection electrode Es-1, calculating the proximity position of the object 9 in the detection area, and calculating the size of the object 9.

[0054] In addition, the processing unit 4 performs a process to determine whether a portion of the multiple first wirings W1 connected to the shielding electrode Ea is disconnected based on the phase difference signal Pi output from the electrostatic capacitance detection device 3.

[0055] The storage unit 5 stores programs including instruction codes executed in the processor of the processing unit 4, data used in processing in the processing unit 4, and data temporarily held during processing. The storage unit 5 is configured using one or more storage devices such as DRAM, SRAM, flash memory, and hard disk.

[0056] Interface unit 6 is a circuit used to exchange data between input device 1 and other devices (such as the host controller of an electronic device equipped with input device 1). Processing unit 4 outputs information obtained based on the detection results of electrostatic capacitance detection device 3 (the presence or absence of object 9, the proximity position of object 9, the distance to object 9, the size of object 9, etc.) to a host device (not shown) via interface unit 6. In the host device, this information is used to construct a user interface, such as recognizing pointing operations and gesture operations.

[0057] exist Figure 1 In this example, the electrostatic capacitance detection device 3, the processing unit 4, the storage unit 5, and the interface unit 6 are disposed on the first wiring substrate B1, and the detection electrodes Es-1 and Es-2 and the shielding electrode Ea are disposed on the second wiring substrate B2. The first wiring substrate B1 and the second wiring substrate B2 are connected by cables 2-1 and 2-2.

[0058] Next, the structure of the electrostatic capacitance detection device 3 will be described. Figure 2 This is a diagram illustrating an example of the structure of the electrostatic capacitance detection device 3 according to this embodiment.

[0059] exist Figure 1 as well as Figure 2 In the example, the electrostatic capacitance detection device 3 includes a first detection signal generation unit 10, an AC voltage output unit 20, a second signal generation unit 30-1 and 30-2, a phase difference signal generation unit 40-1 and 40-2, a sine wave generation unit 50, a second delay unit 60, a D / A conversion unit 70, a first filter F1-1 and F1-2, and a second filter F2-1 and F2-2.

[0060] In addition, Figure 2 In the example, the electrostatic capacitance detection device 3 has capacitors C1-1 and C1-2, capacitors C2-1 and C2-2, and capacitors C3-1 and C3-2.

[0061] [First Detection Signal Generation Unit 10]

[0062] like Figure 2 As shown, the first detection signal generation unit 10 has two detection nodes N1-1 and N1-2 that are connected one-to-one with two detection electrodes Es via two second wirings W2. Detection node N1-i is connected to detection electrode Es-i via second wiring W2-i.

[0063] The first detection signal generation unit 10 supplies charge from the detection node N1-i to the detection electrode Es-i via the second wiring W2-i, so that the voltage of the detection node N1-i oscillates according to the AC voltage Vas output from the AC voltage output unit 20.

[0064] The first detection signal generation unit 10 generates two first detection signals D1-1 and D1-2 corresponding to the charges supplied from the two detection nodes N1-1 and N1-2, respectively. That is, the first detection signal generation unit 10 generates a first detection signal D1-i corresponding to the charge supplied from the detection node N1-i to the detection electrode Es-i.

[0065] exist Figure 2 In the example, the first detection signal generation unit 10 includes charge amplifiers 11-1 and 11-2, attenuation circuits 12-1 and 12-2, differential amplifiers 13-1 and 13-2, A / D conversion units 14-1 and 14-2, and resistors R1-1 and R1-2.

[0066] The attenuation circuit 12-i outputs an AC voltage Vdrv-i that attenuates the amplitude of the AC voltage Vas output by the AC voltage output section 20. The attenuation circuit 12-i maintains the ratio of the amplitude of the AC voltage Vdrv-i to the amplitude of the AC voltage Vas, i.e., the attenuation ratio K, at a ratio that makes the voltage amplitude of the output signal Vo-i of the charge amplifier 11-i near zero in the non-detection state where there is no object 9.

[0067] exist Figure 2 In this example, the attenuation circuit 12-i includes capacitors C4-i and C5-i connected in series. The AC voltage output unit 20 applies an AC voltage Vas to the series circuit of capacitors C4-i and C5-i. One terminal of capacitor C4-i is connected to the AC output node N3 of the AC voltage output unit 20, which outputs the AC voltage Vas. The other terminal of capacitor C4-i is connected to ground via capacitor C5-i. The attenuation circuit 12-i outputs the AC voltage generated in capacitor C5-i as the AC voltage Vdrv-i. The capacitances of capacitors C4-i and C5-i are respectively set such that the voltage amplitude of the output signal Vo-i of the charge amplifier 11-i is near zero in the non-detection state where the object 9 is not present.

[0068] exist Figure 2In the example, capacitor C5-i can have its capacitance value adjusted so that, in the non-detection state where object 9 is not present, the voltage amplitude of the output signal Vo-i of charge amplifier 11.i is near zero. Capacitor C5-i can also be a component such as a semiconductor chip formed inside an IC. In this case, for example, capacitor C5-i may consist of multiple capacitors connected in parallel, and the capacitance value can be adjusted by selecting the number of capacitors connected in parallel using a laser fine-tuning device. Furthermore, capacitor C5-i can also be a discrete component capable of adjusting its value.

[0069] The AC input node N2-i, connecting capacitors C4-i and C5-i, is connected to the AC output node N3 via resistor R2-i. The input of charge amplifier 11-i (the non-inverting input terminal of operational amplifier U1-i, described later) connected to AC input node N2-i has a sufficiently large input impedance compared to resistor R2-i; therefore, the DC potential of AC input node N2-i is approximately equal to the DC potential of AC output node N3. Figure 2 In the example, the resistance value of resistor R2-i can be adjusted during manufacturing. By adjusting this resistance value, the phase of AC voltage Vdrv-i relative to AC voltage Vas can be adjusted.

[0070] Charge amplifier 11-i supplies charge to detection node N1-i, causing the voltage of detection node N1-i to oscillate according to AC voltage Vas, and outputs a signal Vo-i corresponding to the supplied charge. Charge amplifier 11-i inputs AC voltage Vdrv-i, which attenuates the amplitude of AC voltage Vas, into AC input node N2-i, and supplies charge to detection node N1-i, so that the voltage of detection node N1-i is close to the voltage of AC input node N2-i (i.e., an AC voltage Vdrv-i is generated in detection node N1-i).

[0071] exist Figure 2 In the example, charge amplifier 11-i has a feedback capacitor Cag and an operational amplifier U1-i. Operational amplifier U1-i amplifies the voltage difference between the inverting input terminal connected to the detection node N1-i and the non-inverting input terminal connected to the AC input node N2-i, and outputs a signal Vo-i corresponding to the amplified voltage difference. The feedback capacitor Cag is located on the path between the output node of operational amplifier U1-i and the detection node N1-i, where the output signal Vo-i is generated.

[0072] The differential amplifier 13-i outputs a signal Vm-i corresponding to the difference between the output signal Vo-i of the differential amplifier 13-i and the AC voltage Vas. For example, the differential amplifier 13-i includes a fully differential amplifier, outputting the signal Vm-i as a differential signal. Furthermore, in order to suppress aliasing associated with the conversion operation of the subsequent A / D converter 14-i, the differential amplifier 13-i functions as a low-pass filter, attenuating frequency components that are higher than a given frequency band.

[0073] The A / D converter 14-i converts the signal Vm-i output from the differential amplifier 13-i into a digital signal, namely the first detection signal D1-i.

[0074] Resistor R1-i is set in the second path P2-i of the conductive path between detection node N1-i and second wiring W2-i.

[0075] [AC Voltage Output Section 20]

[0076] The AC voltage output unit 20 outputs an AC voltage Vas to the shielding electrode Ea via a plurality of first wirings W1. For example, the AC voltage output unit 20 outputs an AC voltage Vas that is a sine wave with a fixed amplitude and frequency.

[0077] exist Figure 2 In this example, the AC voltage output section 20 includes a constant voltage source 21 that outputs a DC voltage, an operational amplifier U2, and resistors R3 and R4. The DC voltage Vb of the constant voltage source 21 is applied to the non-inverting input terminal of the operational amplifier U2, and a sinusoidal signal Vsin is input to the inverting input terminal of the operational amplifier U2 via resistor R3. Resistor R4 is placed in the path between the output terminal and the inverting input terminal of the operational amplifier U2. The output terminal of the operational amplifier U2 is connected to the AC output node N3. The operational amplifier U2 outputs an AC voltage Vas, which is superimposed with the DC voltage Vb of the constant voltage source 21, from its output terminal to the AC output node N3. Since the amplitude of the DC voltage Vb is greater than half that of the AC voltage Vas, the AC voltage Vas is always a positive voltage. Figure 2 In the example, the resistance value of resistor R4 can be adjusted so that the AC voltage Vas has a given amplitude.

[0078] [First filter F1_i, Second filter F2-i]

[0079] The first filters F1-1 and F1-2 are disposed on the two conductive paths (first paths P1-1 and P1-2) of the respective branches of the two first wirings W1 from the AC output node N3. That is, the first filter F1-i is disposed on the first path P1-i of the branch from the AC output node N3 to the first wiring W1-i.

[0080] The second filters F2-1 and F2-2 are disposed in the two conductive paths (second paths P2-1 and P2-2) between the second wiring W2-1 and W2-2 and the detection nodes N1-1 and N1-2. That is, the second filter F2-i is disposed in the second path P2-i between the second wiring W2-i and the detection node N1-i.

[0081] The first filter F1-i and the second filter F2-i are, for example, low-pass filters with a cutoff frequency higher than that of the AC voltage Vas. Through these filters, external noise propagating from the first wiring W1-i and the second wiring W2-i to the capacitance detection device 3 is attenuated, and noise radiated from the capacitance detection device 3 to the surroundings through the first wiring W1-i and the second wiring W2-i is also attenuated.

[0082] Figure 3A This is a diagram illustrating an example of the structure of the first filter F1-i and the second filter F2-i. Figure 3A In the example, the first filter F1-i and the second filter F2-i are low-pass filters with inductors and capacitors connected in a π-type configuration.

[0083] Figure 3A The first filter F1-i shown has a first inductor L1-i disposed on the first path P1-i, and a first capacitor C6-i and a first capacitor C7-i disposed between the nodes at both ends of the first inductor L1-i and ground. The first capacitor C6-i is connected to one terminal of the first inductor L1-i (the first wiring W1-i side), and the first capacitor C7-i is connected to the other terminal of the first inductor L1-i.

[0084] Figure 3A The second filter F2-i shown has a second inductor L2-i disposed on the second path P2-i, and second capacitors CS-i and C9-i disposed between the nodes at both ends of the second inductor L2-i and ground, respectively. The second capacitor C8-i is connected to one terminal of the second inductor L2-i (the second wiring W2-i side), and the second capacitor C9-i is connected to the other terminal of the second inductor L2-i.

[0085] Figure 3B This is a diagram illustrating another structural example of the first filter F1-i and the second filter F2-i. Figure 3B In the example, the first filter F1-i and the second filter F2-i are low-pass filters with resistors and capacitors connected in a π-type configuration.

[0086] Figure 3BThe first filter F1-i shown has a first resistor R5-i disposed on the first path P1-i and a first capacitor C10-i and a first capacitor C11-i disposed between the nodes at both ends of the first resistor R5-i and ground. The first capacitor C10-i is connected to one terminal of the first resistor R5-i (the first wiring W1-i side), and the first capacitor C11-i is connected to the other terminal of the first resistor R5-i.

[0087] Figure 3B The second filter F2-i shown has a second resistor R6-i disposed on the second path P2-i, and second capacitors C12-i and C13-i disposed between the nodes at both ends of the second resistor R6-i and ground, respectively. The second capacitor C12-i is connected to one terminal of the second resistor R6-i (the second wiring W2-i side), and the second capacitor C13-i is connected to the other terminal of the second resistor R6-i.

[0088] [Capacitors C1-i, C2-i, C3-i]

[0089] Capacitor C1-i is positioned between resistor R1-i and the second filter F2-i in the second path P2-i. Capacitor C2-i is positioned between the terminal of capacitor C1-i on the second filter F2-i side and ground. Through capacitors C1-i and C2-i, the increase in charge of charge amplifier 11-i caused by the large electrostatic capacitance of the capacitive component Crs can be suppressed, thus keeping the detection sensitivity within an appropriate range.

[0090] Capacitor C3-i is positioned between the terminal of the second filter F2-i side of capacitor C1-i and the AC output node N3. Capacitor C3-i reduces external noise propagating from the first wiring W1-i and the second wiring W2-i to the electrostatic capacitance detection device 3.

[0091] [Sine wave generation section 50]

[0092] The sine wave generation unit 50 generates a sine wave signal Dsl that serves as a reference for the AC voltage Vas. The sine wave generation unit 50 generates the sine wave signal Dsl, for example, by sequentially reading the numerical data of the sine wave stored in the memory at a given timing.

[0093] [Second Signal Generation Unit 30-i]

[0094] The second signal generation unit 30-i generates a second detection signal D2-i corresponding to the amplitude of the AC component (the component synchronized with the AC voltage Vas) included in the first detection signal D1-i. The AC component synchronized with the AC voltage Vas included in the first detection signal D1-i has an amplitude corresponding to the capacitance Crg of the object being detected; therefore, the first detection signal D1-i has a value corresponding to the capacitance Crg of the object being detected.

[0095] For example, Figure 4 As shown, the second signal generation unit 30-i includes a first multiplication operation unit 31-i and a first low-pass filter 32-i. The first multiplication operation unit 31-i multiplies the sine wave signal Ds1 with the first detection signal D1-i. The first low-pass filter 32-i outputs the signal after attenuating the high-frequency components of the output signal of the first multiplication operation unit 31-i as the second detection signal D2-i.

[0096] [Phase difference signal generation unit 40-i]

[0097] The phase difference signal generation unit 40-i generates a phase difference signal Pi corresponding to the phase difference between the first detection signal D1-i and the AC voltage Vas.

[0098] For example, such as Figure 4 As shown, the phase difference signal generation unit 40-i includes a second multiplication operation unit 41_i, a second low-pass filter 42-i, and a first delay unit 43-i.

[0099] The first delay unit 43-i delays the phase of the sinusoidal signal Ds1 by 90 degrees. The second multiplication unit 41-i multiplies the sinusoidal signal Ds1 delayed by the first delay unit 43-i with the first detection signal D1-i. The second low-pass filter 42-i outputs the signal after attenuating the high-frequency components of the output signal of the second multiplication unit 41-i as the phase difference signal Pi. When the phase difference between the first detection signal D1-i and the AC voltage Vas is close to zero, the phase difference signal Pi becomes a value close to zero.

[0100] Alternatively, the phase difference signal generation unit 40-i can also generate a phase difference signal Pi corresponding to the phase difference between the first detection signal D1-i and the AC voltage Vas, based on the output signals of the first low-pass filter 32-i and the second low-pass filter 42-i. For example, the sine value of a complex vector with the output signal of the first low-pass filter 32-i as the real part and the output signal of the second low-pass filter 42-i as the imaginary part can also be calculated as the phase difference signal Pi. The phase difference signal Pi calculated in this way also becomes a near-zero value when the phase difference between the first detection signal D1-i and the AC voltage Vas is close to zero.

[0101] [Second Delay Unit 60, D / A Conversion Unit 70]

[0102] The second delay unit 60 generates a sine wave signal Ds2 that delays the sine wave signal Ds1 generated by the sine wave generation unit 50. The D / A conversion unit 70 converts the sine wave signal Ds2 from a digital signal into an analog sine wave signal Vsin and inputs it to the AC voltage output unit 20. The AC voltage output unit 20 generates an AC voltage Vas based on the sine wave signal Vsin that delays and converts the sine wave signal Ds1 into an analog signal.

[0103] The delay amount of the second delay section 60 is adjusted so that the output signal of the second low-pass filter 42-i of the phase difference signal generation section 40-i is minimized. When the output signal of the second low-pass filter 42-i is minimized, the phase difference between the AC component included in the first detection signal D1-i and the sine wave signal Ds1 becomes close to zero, thus increasing the detection sensitivity of the detection target capacitance CRG based on the second detection signal D2-i.

[0104] The electrostatic capacitance detection device 3 is composed of one or more integrated circuits (ICs) and one or more discrete components that are different from the ICs. For example, in the above structure, the first detection signal generation unit 10, the AC voltage output unit 20, the second signal generation unit 30-i, the phase difference signal generation unit 40-i, the sine wave generation unit 50, the second delay unit 60, and the D / A conversion unit 70 are disposed within one or more integrated circuits. Furthermore, the first filter F1_i, the second filter F2-i, the capacitor C1_i, the capacitor C2-i, and the capacitor C3-i are composed of discrete components that are different from the integrated circuits.

[0105] Next, the operation of the electrostatic capacitance detection device 3 in the input device 1 with the above structure will be explained.

[0106] In normal operation without wire breakage, the charge amplifier 11-i of the first detection signal generation unit 10 supplies charge to the detection node N1, so that an AC voltage Vdrv-i is generated at the detection node N1-i that is approximately the same as the AC voltage Vdrv-i after the amplitude of the AC voltage Vas is attenuated by the attenuation circuit 12-i. This charge is supplied from the detection node N1-i to the detection electrode Es-i via the second wiring W2-i. Therefore, the amplitude of the charge fluctuation corresponding to the AC voltage Vdrv-i varies according to the capacitance Crg of the detection object. Thus, the amplitude of the output signal Vo-i of the charge amplifier 11-i varies according to the capacitance Crg of the detection object, and the amplitude of the first detection signal D1-i, which amplifies and converts the difference between the output signal Vo-i of the charge amplifier 11-i and the AC voltage Vas into a digital signal, also varies according to the capacitance Crg of the detection object. The second signal generation unit 30-i generates a second detection signal D2-i corresponding to the amplitude of the AC component (the component synchronized with the AC voltage Vas) included in the first detection signal D1-i. Therefore, the value of the second detection signal D2-i varies according to the capacitance Crg of the object being detected. Thus, the change in the capacitance Crg of the object being detected caused by the object 9 approaching the detection electrode Es-i can be detected as a change in the second detection signal D2-i.

[0107] In the absence of a disconnection or other issues, the phase difference between the AC component (the component synchronized with the AC voltage Vas) included in the first detection signal D1-i and the sine wave signal Ds1 is small. Therefore, the phase difference signal Pi generated by the phase difference signal generation unit 40-i becomes a value close to zero.

[0108] Here, for example, Figure 5 As shown, a portion of multiple first wirings W1 (in) Figure 5 In the example, the first wiring (W1-2) is broken. In this case, the number of first filters F1-i connected in parallel between the AC output node N3 and the shielding electrode Ea is reduced. Furthermore, in the first filter F1-i... Figure 3A , Figure 3BIn the case of a π-type low-pass filter as shown, the electrostatic capacitance between the AC output node N3 of the first filter F1-i, which is connected to the first wiring W1 where the disconnection occurred, and ground appears to increase. As a result, the frequency characteristics from the AC output node N3 to the shielding electrode Ea change, and the frequency characteristics from the AC output node N3 to the output node of the first detection signal D1-i also change. Therefore, the phase difference between the AC voltage Vas output at the AC output node N3 and the AC component included in the first detection signal D1-i changes. Specifically, the cutoff frequency of the low-pass filter characteristics from the AC output node N3 to the output node of the first detection signal D1-i decreases, thus the phase of the AC component included in the first detection signal D1-i lags behind the phase of the sine wave signal Ds1. Due to this change in phase difference, the phase difference signal Pi generated by the phase difference signal generation unit 40-i also changes. Therefore, a disconnection occurring in a portion of the plurality of first wiring W1s can be detected based on the change in the phase difference signal Pi.

[0109] When the phase difference between the AC component included in the first detection signal D1-i and the sine wave signal Ds1 is small, the rate of change of the second detection signal D2-i of the second signal generation unit 30-i, obtained based on the product of the first detection signal D1-i and the sine wave signal Ds1, with respect to the phase difference is close to zero. Therefore, it is difficult to detect this phase difference based on the second detection signal D2-i. In contrast, the phase difference signal Pi of the phase difference signal generation unit 40-i, obtained based on the product of the signal that delays the sine wave signal Ds1 by 90 degrees and the first detection signal D1-i, has the largest rate of change with respect to the phase difference. Therefore, the phase difference signal Pi also changes significantly according to the change in phase difference, and thus, the breakage of the first wiring W1 can be easily determined based on the change in the phase difference signal Pi.

[0110] Furthermore, this embodiment is not limited to the examples described above, and includes various variations.

[0111] Figure 6 This is a diagram showing a modified example of the phase difference signal generation unit 40-i. Figure 6 The phase difference signal generation unit 40-i shown includes: a delay unit 44-i that delays the sine wave signal Ds1 according to an input control signal; a phase comparison unit 45-i that compares the phase of the output signal of the delay unit 44-i with the phase of the first detection signal D1-i; and an integrator unit 46-i that integrates the signal corresponding to the phase comparison result of the phase comparison unit 45-i and outputs it as a phase difference signal Pi. The delay unit 44-i takes the phase difference signal Pi output by the integrator unit 46-i as a control signal input and controls the delay amount of the sine wave signal Ds1 according to the phase difference signal Pi.

[0112] exist Figure 6 In the phase difference signal generation unit 40-i shown, the phase comparison unit 45-i outputs a positive or negative signal based on the phase comparison result between the output signal of the delay unit 44-i and the first detection signal D1-i. For example, when the phase of the output signal of the delay unit 44-i leads the phase of the first detection signal D1-i, a positive signal is output; otherwise, a negative signal is output. The delay unit 44-i increases the delay amount when the value of the phase difference signal Pi increases positively, and decreases the delay amount when the value of the phase difference signal Pi increases negatively. Thus, the value of the phase difference signal Pi becomes a value corresponding to the phase difference between the first detection signal D1-i and the sine wave signal Ds1.

[0113] In the above embodiment, there are two detection electrodes, but in other examples of this embodiment, there may be three or more detection electrodes.

[0114] In the above embodiments, the first detection signal generation unit has the same number of charge amplifiers as the detection electrodes. However, in other examples of this embodiment, the connection between multiple detection electrodes and charge amplifiers can be switched by using a selector circuit, so that the number of charge amplifiers in the first detection signal generation unit is less than the number of detection electrodes.

[0115] The input device of this embodiment is not limited to a user interface device that inputs information based on finger operations or the like. That is, the input device of this embodiment can be widely applied to devices that detect the electrostatic capacitance between various objects, not limited to the human body, and detection electrodes.

[0116] -Explanation of Figure Markers-

[0117] 1…Input device, 2-1, 2-2…Cables, 3…Capacitance detection device, 4…Processing unit, 5…Storage unit, 6…Interface unit, 9…Object, 10…First detection signal generation unit, 11-1, 11-2…Chart amplifier, 12-1, 12-2…Attenuation circuit, 13-1, 13-2…Differential amplifier, 14-1, 14-2…A / D conversion unit, 20…AC voltage output unit, 21…Constant voltage source, 30-1, 30-2…Second signal generation unit, 31-1, 31-2…First multiplication unit, 32-1, 32-2…First low-pass filter, 40-1, 40-2…Phase difference signal Generating section, 41-1, 41-2… Second multiplication operation section, 42-1, 42-2… Second low-pass filter, 43-1, 43-2… First delay section, 44-1, 44-2… Delay section, 45-1, 45-2… Phase comparison section, 46-1, 45-2… Integrator, 50… Sine wave generating section, 60… Second delay section, 70… D / A conversion section, Es-1, Es-2… Detection electrode, Ea… Shielding electrode, F1-1, F1-2… First filter, F2-1, F2-2… Second filter, W1, W1-1, W1-2… First wiring, W2-1, W2-2… Second wiring.

Claims

1. An electrostatic capacity detection device that detects an electrostatic capacity between a detection electrode disposed in proximity to a shield electrode and an object, characterized by comprising: an alternating-current voltage output section that outputs an alternating-current voltage to the shield electrode via a plurality of first wirings; a first detection signal generation section that has a plurality of detection nodes connected one-to-one to a plurality of the detection electrodes via a plurality of second wirings disposed in proximity to the first wirings, respectively, that supplies electric charges to the detection electrodes from the detection nodes via the second wirings so that voltages of the detection nodes vibrate in accordance with the alternating-current voltage, and that generates a plurality of first detection signals corresponding to the electric charges supplied from the respective detection nodes; a plurality of first filters provided in a plurality of first paths branching from an alternating-current output node that outputs the alternating-current voltage from the alternating-current voltage output section to the respective first wirings; and at least one phase difference signal generation section that generates a phase difference signal corresponding to a phase difference between one of the first detection signals and the alternating-current voltage.

2. The electrostatic capacity detection device according to claim 1, wherein the first filter is a low-pass filter having a cut-off frequency higher than a frequency of the alternating-current voltage.

3. The electrostatic capacity detection device according to claim 2, wherein the electrostatic capacity detection device has a plurality of second filters provided in a plurality of second paths between the plurality of second wirings and the plurality of detection nodes, the second filter is a low-pass filter having a cut-off frequency higher than the frequency of the alternating-current voltage.

4. The electrostatic capacity detection device according to claim 3, wherein the electrostatic capacity detection device has: a sine wave generation section that generates a sine wave signal; and at least one second detection signal generation section that generates a second detection signal corresponding to an amplitude of an alternating-current component included in the first detection signal, the alternating-current voltage output section outputs the alternating-current voltage corresponding to the sine wave signal, the second detection signal generation section includes: a first multiplication operation section that multiplies the sine wave signal and the first detection signal; and a first low-pass filter that attenuates a high-frequency component of an output signal of the first multiplication operation section, the phase difference signal generation section includes: a first delay section that delays a phase of the sine wave signal by 90 degrees; a second multiplication operation section that multiplies the sine wave signal delayed by the first delay section and the first detection signal; and a second low-pass filter that attenuates a high-frequency component of an output signal of the second multiplication operation section, the second detection signal generation section generates the second detection signal corresponding to an output signal of the first low-pass filter, and the phase difference signal generation section generates the phase difference signal corresponding to an output signal of the second low-pass filter.

5. The electrostatic capacity detection device according to claim 4, wherein the electrostatic capacity detection device has a second delay section that delays the sine wave signal, the alternating-current voltage output section outputs the alternating-current voltage corresponding to the sine wave signal delayed by the second delay section. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ adjusting the delay amount of the second delay section so that the output signal of the second low-pass filter becomes minimum.

6. The electrostatic capacity detection device according to claim 4, wherein the first detection signal generation section includes: at least one charge amplifier that supplies the detection node with the electric charge so that the voltage of the detection node vibrates in accordance with the alternating voltage, and outputs a signal corresponding to the supplied electric charge; at least one differential amplifier that outputs a signal corresponding to the difference between the output signal of the charge amplifier and the alternating voltage; and at least one analog-digital conversion section that converts the output signal of the differential amplifier into a digital signal and outputs it as the first detection signal.

7. The electrostatic capacity detection device according to any one of claims 4 to 6, wherein the alternating voltage output section, the first detection signal generation section, the second detection signal generation section, the phase difference signal generation section, and the sine wave generation section are provided within one or more integrated circuits, the first filter and the second filter are constituted by one or more components different from the one or more integrated circuits.

8. The electrostatic capacity detection device according to any one of claims 3 to 6, wherein the first filter includes: a first inductor provided to the first path; and two first capacitors provided between the nodes at both ends of the first inductor and the ground, the second filter includes: a second inductor provided to the second path; and two second capacitors provided between the nodes at both ends of the second inductor and the ground.

9. The electrostatic capacity detection device according to any one of claims 3 to 6, wherein the first filter includes: a first resistor provided to the first path; and two first capacitors provided between the nodes at both ends of the first resistor and the ground, the second filter includes: a second resistor provided to the second path; and two second capacitors provided between the nodes at both ends of the second resistor and the ground.

10. The electrostatic capacity detection device according to any one of claims 1 to 6, wherein the alternating voltage output section, the first detection signal generation section, the plurality of first filters, and the at least one phase difference signal generation section are provided on a common first wiring substrate, the shield electrode and the plurality of detection electrodes are provided on one or more second wiring substrates, the first wiring substrate and the one or more second wiring substrates are connected by one or more wiring cables, the first wiring and the second wiring are respectively included in the wiring cables.

11. The electrostatic capacity detection device according to any one of claims 1 to 6, wherein the alternating voltage output section outputs the alternating voltage superimposed with a direct current voltage larger than half the amplitude.

12. An input device for inputting information corresponding to the proximity of an object, characterized in that, has: a plurality of detection electrodes whose electrostatic capacity with the object changes in accordance with the approach of the object; a shield electrode disposed in proximity to the plurality of detection electrodes; and ​ The electrostatic capacity detection device according to any one of claims 1 to 11, wherein the electrostatic capacity between the object and each of the plurality of detection electrodes is detected.

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