Capacitive sensing device and capacitive detection method, electronic device

Abstract

The application discloses a capacitive sensing device, a capacitive detection method and an electronic device. The capacitive sensing device comprises a common terminal connected to a sensing electrode, at least one detection module, the detection module comprising an amplifier, a first input terminal of the amplifier being connected to the common terminal, a second input terminal of the amplifier being connected to a fixed potential terminal, and a feedback capacitor being connected between the first input terminal and an output terminal of the amplifier; a compensation module comprising a compensation capacitor, a first terminal of the compensation capacitor being connected to the first input terminal of the amplifier; and a control module for controlling the compensation capacitor and the feedback capacitor to be pre-charged, then controlling the detection module to detect an electrical signal of the common terminal and output a sensing signal in a single detection period. In the detection process, based on the charge transfer of the pre-charging, the effective compensation capacitor value provided by the compensation module is greater than the actual capacitor value of the compensation capacitor. The capacitive sensing device can improve the capacitive compensation multiplication effect.

Description

Technical Field

[0001] This application relates to the field of integrated circuit technology, specifically to a capacitance sensing device and capacitance detection method, and electronic equipment. Background Technology

[0002] A capacitive sensor is a device that converts the measured physical or mechanical quantity into a change in capacitance. Due to its advantages such as simple structure, stable performance, and high sensitivity, capacitive sensors are widely used in industrial and consumer electronics products, such as for measuring pressure, displacement, acceleration, thickness, and liquid level.

[0003] The capacitance detection module converts the change in the sensor's capacitance into an electrical signal output. By measuring the magnitude of this electrical signal, the magnitude of the measured quantity can be determined; this is the basic working principle of a capacitive sensor. The capacitance (C) of a capacitive sensor... X It consists of two parts: parasitic capacitance (C) P ) and variable capacitance (ΔC), where parasitic capacitance C P The capacitance is a fixed value. When a finger or other object approaches the sensor, the variable capacitance ΔC of the capacitance sensor changes.

[0004] For a capacitive sensor with a self-capacitance structure, the self-capacitance has only one plate, and an inherent parasitic capacitance C is formed between the plate and ground. P When a finger approaches the sensor, a variable capacitance ΔC is formed between the finger and the sensor plate. Since the human body has a relatively large capacitance, its potential is equivalent to ground; therefore, ΔC is related to the distance between the finger and the plate. By detecting the magnitude of ΔC, it is possible to determine whether a finger is close or to calculate the distance to the finger; the capacitance value becomes C. X =C P +ΔC.

[0005] In practical applications, the parasitic capacitance C P The value of may be much larger than the variable capacitance ΔC, while the capacitance that is truly effective for sensing is the value of the variable capacitance ΔC. If the parasitic capacitance C P If the capacitance is too large, it can easily cause the capacitance detection module to saturate, making it unable to detect changes in ΔC. Therefore, it is necessary to compensate for the inherent parasitic capacitance of the sensor. The compensated parasitic capacitance C P 'For: C P =C P -C b C b To compensate for the capacitance value. Regardless of the capacitor structure used for testing, the purpose of parasitic capacitance compensation is to find a suitable compensation capacitance value C. b This makes C PThe variable capacitance ΔC is equal to or as close to 0 as possible, so that when the variable capacitance ΔC = 0, the output signal of the sensing device is near zero. Thus, when an object approaches, the change in the variable capacitance ΔC can be effectively reflected in the change in the output signal.

[0006] In existing technologies for compensating parasitic capacitance, a compensation capacitor module is typically placed inside the capacitive sensing chip. However, due to limited chip area, placing too many capacitors inside the chip leads to complex layout and routing, consumes excessive area, and increases costs. While compensating with both on-chip and off-chip capacitors can reduce the area of ​​the on-chip compensation capacitor, the addition of an off-chip capacitor reduces the ease of use of the capacitive sensing chip. Therefore, when chip area is limited, external parasitic capacitance is much larger than the compensation capacitor, and off-chip compensation capacitors are not used, the capacitance compensation effect of existing technologies needs further improvement. Summary of the Invention

[0007] In view of this, this application provides a capacitance sensing device and a capacitance detection method and electronic device thereof to improve the parasitic capacitance compensation effect, thereby improving the accuracy of capacitance detection.

[0008] This application provides a capacitive sensing device, comprising: a common terminal for connection to a sensing electrode; at least one detection module, the detection module including an amplifier, a first input terminal of the amplifier connected to the common terminal, a second input terminal connected to a fixed potential terminal, and a feedback capacitor connected between the first input terminal and the output terminal of the amplifier; a compensation module including a compensation capacitor, the first terminal of the compensation capacitor connected to the first input terminal of the amplifier; and a control module for controlling the compensation capacitor and the feedback capacitor to pre-charge within a single detection cycle, and then controlling the detection module to detect the electrical signal of the common terminal and output a sensing signal. During the detection process, based on the charge transfer from the pre-charge, the effective compensation capacitance value provided by the compensation module is greater than the actual capacitance value of the compensation capacitor.

[0009] Optionally, the compensation capacitor includes several capacitor arrays connected in parallel, the actual capacitance value of each capacitor array is adjustable, and the actual capacitance value of the compensation capacitor is the sum of the actual capacitance values ​​of each capacitor array.

[0010] Optionally, the compensation capacitor may include at least two capacitor arrays with different capacitance adjustment accuracies.

[0011] Optionally, it also includes: a signal processing module, connected to the output terminal of the detection module, for converting the sensing signal output by the detection module into a digital sensing signal and outputting it.

[0012] Optionally, the capacitive sensing chip includes: during pre-charging, the control module controls the output terminal of the amplifier to be connected to a reference voltage terminal, both input terminals of the amplifier to a fixed potential terminal, and connects the sensing electrode and the first terminal of the compensation capacitor to a power supply voltage or ground; during detection of the electrical signal at the common terminal, the control module disconnects the amplifier from the reference voltage terminal, disconnects the first input terminal of the amplifier from the second input terminal, electrically connects the common terminal to the first input terminal of the amplifier, and switches the connection relationship between the second terminal of the compensation capacitor and ground and power supply voltage.

[0013] Optionally, the control module includes: a first switch connected between the second terminal of the compensation capacitor and ground; a second switch connected between the second terminal of the compensation capacitor and the power supply voltage; a third switch connected between the two input terminals of the amplifier; a fourth switch connected between the output terminal of the amplifier and the reference voltage terminal; a fifth switch connected between the common terminal and the power supply voltage; a sixth switch connected between the common terminal and ground; and a seventh switch connected between the common terminal and the first input terminal of the amplifier.

[0014] Optionally, the reference voltage terminal is grounded.

[0015] Optionally, the ratio of the voltage at the fixed potential terminal to the power supply voltage is 1:n or (n-1):n; the effective compensation capacitor value provided by the compensation module is n times the actual capacitance value of the compensation capacitor, where n≥1.

[0016] Optionally, it includes two detection modules, namely a first detection module and a second detection module, wherein the second input terminal of the amplifier of the first detection module is connected to a first fixed potential terminal, and the second input terminal of the amplifier of the second detection module is connected to a second fixed potential terminal.

[0017] Optionally, the control module is used to control the two detection modules to output sensing signals sequentially.

[0018] Optionally, the ratio of the voltage at the first fixed potential terminal to the power supply voltage is (n-1):n; and the ratio of the voltage at the second fixed potential terminal to the power supply voltage is 1:n.

[0019] This application also provides a capacitance detection method, comprising: providing a capacitance sensing device as described in any of the above claims; controlling the compensation capacitor and the feedback capacitor to pre-charge during a single detection cycle, and then controlling the detection module to detect the electrical signal at the common terminal and output a sensing signal.

[0020] Optionally, the detection method includes: during pre-charging: connecting the output terminal of the amplifier to a reference voltage terminal and connecting both input terminals to a fixed potential terminal; connecting the common terminal and the first terminal of the compensation capacitor to a power supply voltage, or grounding both the common terminal and the first terminal of the compensation capacitor; when detecting the electrical signal at the common terminal: disconnecting the amplifier from the reference voltage terminal and disconnecting the two input terminals of the amplifier, connecting the common terminal to the first input terminal of the amplifier, switching the connection relationship between the first terminal of the compensation capacitor and ground and the power supply voltage, and obtaining the output signal of the amplifier's output terminal as a sensing signal.

[0021] Optionally, when the capacitive sensing device includes a first detection module and a second detection module, the first sensing signal and the second sensing signal output by the two detection modules are acquired respectively; the first sensing signal and the second sensing signal are differentially processed, and the analog signal after differential processing is processed to obtain a digital sensing signal.

[0022] This application also provides an electronic device, including: a capacitive sensing device as described in any of the preceding claims.

[0023] The capacitance sensing device and capacitance detection method described in this application achieve a capacitance compensation multiplication effect without increasing the actual compensation capacitor area. This is particularly effective when external parasitic capacitance is large, as compensation for parasitic capacitance can be achieved using a smaller internal compensation capacitor area. Furthermore, by adjusting the ratio between the fixed potential terminal and the power supply voltage, the compensation capacitance can be multiplied, and the ratio between the effective compensation capacitance value and the actual compensation capacitance value can be adjusted accordingly. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the structure of a capacitive sensing device according to an embodiment of this application;

[0026] Figure 2a This is a schematic diagram of the structure of a compensation module according to an embodiment of this application;

[0027] Figure 2b This is a schematic diagram of the capacitor array within a compensation module according to an embodiment of this application;

[0028] Figure 3This is a schematic diagram of the structure of a capacitive sensing device according to an embodiment of this application;

[0029] Figure 4 This is a schematic flowchart of a capacitance detection method according to an embodiment of this application;

[0030] Figure 5 This is a schematic flowchart of a capacitance compensation multiplication method according to an embodiment of this application. Detailed Implementation

[0031] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. In the absence of conflict, the following embodiments and their technical features can be combined with each other.

[0032] Please refer to Figure 1 This is a schematic diagram of the equivalent circuit of a capacitive sensing device according to an embodiment of the present invention.

[0033] The capacitance sensing device 10 includes a common terminal PAD, at least one detection module 102, a compensation module 101, and a control module.

[0034] The common terminal PAD is used to connect the sensing electrode. A capacitance Cx is formed between the sensing electrode and the object being measured. A sensing signal is obtained by detecting changes in the capacitance Cx, and the sensing signal is proportional to the distance between the sensing electrode and the object being measured. The common terminal PAD can be a pin of the capacitance sensing chip 100, and the sensing electrode is typically a metal electrode plate on a circuit board.

[0035] The detection module 102 includes an amplifier AMP. The first input terminal IN1 of the amplifier AMP is connected to the common terminal PAD, and the second input terminal IN2 is connected to the fixed potential terminal A. A feedback capacitor Cv is connected between the first input terminal IN1 and the output terminal VOUT of the amplifier AMP. The operational amplifier AMP and the feedback capacitor Cv constitute an integrating amplifier, which is used to integrate and amplify the charge on the sensing electrode Cx of the sensing capacitor Cx and output the analog sensing signal Vout.

[0036] The compensation module 101 includes a compensation capacitor Cb, the first end of which is connected to the first input terminal of the amplifier AMP.

[0037] The control module 1001, connected to the compensation module 101 and the detection module 102, is used to control the compensation capacitor Cb and the feedback capacitor Cv to precharge within a single detection cycle, and then control the detection module 102 to detect the electrical signal of the common terminal PAD and output a sensing signal. During the detection process, based on the charge transfer of the precharge, the effective compensation capacitor value provided by the compensation module 101 is greater than the actual capacitance value of the compensation capacitor.

[0038] In this embodiment, the various modules of the capacitance sensing device 100 are integrated onto a single chip, serving as a capacitance sensing chip. In other embodiments, the various modules within the capacitance sensing device 100 may also be housed within different chips.

[0039] In embodiments of the present invention, Figure 1 In the capacitance sensing device shown, the compensation module 101 can provide an effective compensation capacitor that is greater than the actual capacitance value of the compensation capacitor. Without increasing the area of ​​the actual compensation capacitor, it can achieve a capacitance compensation multiplication effect. In particular, when the external parasitic capacitance is large, the internal compensation capacitor with a small area can be used to compensate for the parasitic capacitance.

[0040] In some embodiments, during pre-charging, the control module 1001 controls the output terminal of the amplifier AMP to be connected to the reference voltage terminal VREF, both input terminals of the amplifier AMP to the fixed potential terminal VA, and the first terminal of the sensing electrode and the compensation capacitor Cb to be connected to the power supply voltage VCC or ground GND; when detecting the electrical signal of the common terminal PAD, the control module 1001 disconnects the amplifier AMP from the reference voltage terminal VREF, disconnects the first input terminal IN1 and the second input terminal IN2 of the amplifier AMP, electrically connects the common terminal PAD to the first input terminal of the amplifier PAD, and switches the connection relationship between the second terminal of the compensation capacitor Cb and ground and the power supply voltage.

[0041] Figure 1In the illustrated embodiment, the control module 1001 includes: a first switch K1 connected between the second terminal of the compensation capacitor Cb and ground GND; a second switch K2 connected between the second terminal of the compensation capacitor Cb and the power supply voltage VCC; a third switch K3 connected between the two input terminals of the amplifier AMP; a fourth switch K4 connected between the output terminal of the amplifier AMP and the reference voltage terminal VREF; a fifth switch K5 connected between the common terminal PAD and the power supply voltage VCC; a sixth switch K6 connected between the common terminal PAD and ground GND; and a seventh switch K7 connected between the common terminal PAD and the first input terminal IN1 of the amplifier AMP.

[0042] The connection between the compensation capacitor Cb and the ground (GND) and the power supply voltage (VCC) can be switched by controlling the on / off states of the first switch K1 and the second switch K2. For example, opening the first switch K1 and closing the second switch K2 connects the first terminal of the compensation capacitor Cb to the power supply voltage VCC; opening the second switch K2 and closing the second switch K1 grounds the first terminal of the compensation capacitor Cb.

[0043] In the above description, "open" and "closed" of the switch refer to the switch being in an open-circuit and closed-circuit state, respectively. Each "switch" refers to a component with switching characteristics. The illustrations are only equivalent circuit diagrams and not actual switch structures. The switch can be a MOS transistor, bipolar junction transistor, or diode—a component with switching characteristics—and its on / off state can be controlled by corresponding methods to this component. Those skilled in the art can select appropriate switch structures according to the needs of actual circuit design; details will not be elaborated here.

[0044] The compensation capacitor Cb is a schematic representation of the equivalent capacitance. The compensation capacitor Cb is specifically implemented by a particular circuit structure and can be a single capacitor or multiple capacitors connected in parallel. In one embodiment of the present invention, the compensation capacitor Cb comprises several parallel capacitor arrays, the actual capacitance value of each capacitor array is adjustable, and the actual capacitance value of the compensation capacitor Cb is the sum of the actual capacitance values ​​of each capacitor array.

[0045] Please refer to Figure 2a This is a schematic diagram of the structure of the compensation capacitor Cb according to an embodiment of the present invention.

[0046] In this embodiment, the compensation capacitor Cb includes a plurality of capacitor arrays 201 and a control unit 202 connected to the capacitor arrays.

[0047] Please refer to Figure 2b This is a schematic diagram of the structure of a capacitor array 201 according to an embodiment of the present invention.

[0048] The capacitor array 201 includes multiple capacitors C1 to Cn connected in parallel. One end of each capacitor is connected to the first input terminal IN1, and the other end is connected to a switch K. By controlling the on / off state of the switch K, the actual capacitance value of each capacitor array 201 connected to the circuit is controlled. The control unit 202 is used to control the on / off state of each switch K. The compensation capacitor Cb is the sum of the actual capacitance values ​​of each capacitor array 201 connected to the circuit.

[0049] In some embodiments, the compensation capacitor Cb includes at least two capacitor arrays with different capacitance adjustment accuracies. For example, it includes a first capacitor array with lower adjustment accuracy, in which the capacitance values ​​of the capacitors connected in parallel are larger, and the adjustment accuracy of the actual capacitance value connected to the circuit is smaller, so that the compensation capacitor value can be quickly adjusted to near the target value. It also includes a second capacitor array with higher adjustment accuracy, in which the adjustment accuracy of the actual capacitance value connected to the circuit is smaller, so that high-precision adjustment can be achieved, making the final compensation capacitor even closer to the target value.

[0050] In one embodiment, the ratio of the voltage VA at the fixed potential terminal A to the power supply voltage VCC is 1:n, for example, 1:1, 1:2, etc.; or, the ratio of the voltage VA at the fixed potential terminal A to the power supply voltage VCC is (n-1):n, for example, 1:2, 2:3, etc., and the effective compensation capacitor value provided by the compensation module 101 is n times the actual capacitance value of the compensation capacitor, where n≥1. When the parasitic capacitance to be compensated in the circuit is Cp, the equivalent capacitance value Cb of the compensation module 101 can be adjusted so that, within the adjustable range, Cb is equal to or as close as possible to Cp / n.

[0051] The common terminal PAD is connected to the power supply voltage VCC via a fifth switch K5, and to the ground terminal GND via a sixth switch K6. By controlling the on / off state of the fifth switch K5 and the sixth switch K6, the sensing electrode can be switched to be grounded or connected to the power supply voltage VCC.

[0052] A seventh switch K7 is connected between the common terminal PAD and the first input terminal IN1 of the operational amplifier AMP. When the electrical signal of the common terminal PAD is detected, the first switch K7 is turned on, so that the common terminal PAD is connected to the first input terminal IN1 of the operational amplifier AMP, and the detection module 102 is connected to the sensing capacitor Cx.

[0053] In this embodiment, the capacitance sensing device further includes a signal processing module 103. In this embodiment, the signal processing module 103 employs an analog-to-digital converter (ADC). The input terminal of the signal processing module 103 is connected to the output terminal Vout of the detection module 102, and is used to convert the analog sensing signal Vout output by the detection module 102 into a digital sensing signal Dout and output it. In other embodiments, the signal processing module 103 can also be implemented using an external circuit structure, without needing to be integrated into the capacitance sensing device 100.

[0054] Please refer to Figure 3 This is a schematic diagram of the equivalent circuit structure of a capacitive sensing device according to another embodiment of the present invention.

[0055] In this embodiment, the capacitance sensing device 100 includes two detection modules, namely a first detection module 1021 and a second detection module 1022. In this embodiment, the first detection module 1021 and the second detection module 1022 have the same circuit structure. The control module 1001 is used to control the two detection modules to sequentially output sensing signals.

[0056] The second input terminal IN2 of the operational amplifier AMP of the first detection module 1021 is connected to the first fixed potential terminal A. The second input terminal IN2' of the operational amplifier AMP' of the second detection module 1022 is connected to the second fixed potential terminal A', and a feedback capacitor Cv' is connected between the output terminal and the first input terminal IN1'.

[0057] The control module 1001 also includes a switch K3' connected between the two input terminals of the amplifier AMP' and a switch K7' connected between the first input terminal IN1' and the common terminal PAD of the amplifier AMP'.

[0058] The voltage V at the first fixed potential terminal A A1 The ratio of the voltage to the power supply voltage VCC is (n-1):n; the voltage V at the second fixed potential terminal A' is... A2 The ratio of the voltage to the power supply voltage VCC is 1:n.

[0059] Embodiments of the present invention also provide a capacitance detection method according to the above embodiments.

[0060] Please refer to Figure 4 This is a schematic diagram of the capacitance detection method.

[0061] Step S101: Provide a capacitance sensing device.

[0062] Step S102: Within a single detection cycle, control the compensation capacitor and the feedback capacitor to precharge, and then control the detection module to detect the electrical signal at the common terminal and output a sensing signal.

[0063] In one embodiment, step S102 further includes: during pre-charging: connecting the output terminal of the amplifier to a reference voltage terminal and connecting both input terminals to a fixed potential terminal; connecting the common terminal and the first terminal of the compensation capacitor to a power supply voltage, or grounding both the common terminal and the first terminal of the compensation capacitor; during detection of the electrical signal at the common terminal: disconnecting the amplifier from the reference voltage terminal and disconnecting the two input terminals of the amplifier, connecting the common terminal to the first input terminal of the amplifier, switching the connection relationship between the first terminal of the compensation capacitor and ground and the power supply voltage, and obtaining the output signal of the amplifier's output terminal as a sensing signal.

[0064] The following is based on Figure 1 The capacitance sensing device of the illustrated embodiment specifically describes the above-described capacitance detection method.

[0065] Adopting such Figure 1 The capacitance sensing device 100 connects the common terminal PAD to the sensing electrode of the sensing capacitor Cx. The following detection steps are achieved by controlling the various switches within the capacitance sensing device 100:

[0066] During pre-charging: connect the output of the operational amplifier AMP to the reference voltage VREF terminal, and connect both input terminals IN1 and IN2 to the fixed potential terminal A; connect the common terminal PAD to the power supply voltage VCC, and connect the first terminal of the compensation capacitor Cb to the power supply voltage VCC.

[0067] Specifically, to achieve the above control, targeting Figure 1 In the first stage of the capacitive sensing device shown, the second switch K2, the fourth switch K4, the third switch K3 and the fifth switch K5 are turned on, while the first switch K1, the sixth switch K6 and the seventh switch K7 are turned off.

[0068] The potential of the fixed potential terminal A is V A1 In the first stage, the total charge of the circuit is

[0069] Q = V CC C X +(V A1 -V CC C b +(V A1 -V REF C V .

[0070] When detecting the electrical signal at the common terminal: disconnect the operational amplifier AMP from the reference voltage VREF terminal, and disconnect the first input terminal IN1 and the second input terminal IN2 of the operational amplifier AMP. Connect the common terminal PAD to the first input terminal IN1. Switch the connection relationship between the first terminal of the compensation capacitor Cb and ground GND and power supply voltage VCC, that is, switch the first terminal of the compensation capacitor Cb to be connected to ground GND, and obtain the output signal of the output terminal of the amplifier AMP as the sensing signal Vout1.

[0071] Specifically, when detecting the electrical signal at the common terminal, the seventh switch K7 and the first switch K1 are turned on, while the fifth switch K5, the sixth switch K6, the second switch K2, the third switch K3, and the fourth switch K4 are turned off.

[0072] Due to the virtual short effect at the input of the amplifier AMP, the potential of the first input terminal IN1 is the same as the potential of the second output terminal IN2, both being VA1. At this time, the total charge of the circuit is...

[0073] Q′=V A1 (C X +C b )+(V A1 -V OUT1 C V

[0074] Based on the law of charge conservation, Q = Q'

[0075] but,

[0076]

[0077] Where C X =C P +ΔC, C P The externally fixed parasitic capacitance value is given by ΔC, where C is the capacitance when the object approaches. x The change in capacitance.

[0078] The voltage V at point A A1 The power supply voltage VCC is set in a ratio of (n-1):n.

[0079]

[0080] Correspondingly, when the compensation capacitor Cb is n times closer to the parasitic capacitance C P hour,

[0081]

[0082] In this way, theoretically, it is possible to provide an effective compensation capacitance n times greater than the compensation capacitance value while keeping the area of ​​the compensation capacitor Cb constant. Of course, in practical applications, n will not take a large value, because a large value of n will greatly reduce the accuracy of the compensation capacitor. In some embodiments, n is in the range of 2 to 3.

[0083] For example, when n=2, V A1 =V CC / 2,

[0084]

[0085] When twice the compensation capacitor Cb is close to the parasitic capacitance C P hour,

[0086]

[0087] When no object is nearby, i.e., the variable capacitor ΔC = 0, the output signal V of amplifier AMP is... OUT1 In V REF nearby.

[0088] When VREF is set to 0, i.e., the reference voltage terminal is grounded, and the variable capacitor ΔC = 0, the output signal V of the operational amplifier AMP is... OUT1 The value is near 0; at this point, when an object approaches, the change in the variable capacitor ΔC can be effectively reflected in the output signal V. OUT1 The changes.

[0089] against Figure 1 The capacitance sensing device shown in the invention also provides another capacitance detection method, as detailed below:

[0090] Adopting such Figure 1 The capacitance sensing device 100 connects the common terminal PAD to the sensing electrode of the sensing capacitor. The following detection steps are achieved by controlling the various switches within the capacitance sensing device 100:

[0091] During pre-charging: connect the output of the operational amplifier AMP to the reference voltage VREF terminal, and connect both input terminals IN1 and IN2 to the fixed potential terminal A; connect the common terminal PAD to ground GND, and connect the first terminal of the compensation capacitor Cb to ground GND.

[0092] Specifically, the sixth switch K6, the first switch K1, the third switch K3, and the fourth switch K4 are turned on, while the fifth switch K5, the seventh switch K7, and the second switch K2 are turned off.

[0093] In this embodiment, the voltage at the fixed potential terminal A is V. A2 At this time, the total charge in the circuit is:

[0094] Q = V A2 C b +(V A2 -V REF C V ;

[0095] When detecting the electrical signal at the common terminal: disconnect the operational amplifier AMP from the reference voltage VREF, and disconnect the first input terminal IN1 and the second input terminal IN2 of the operational amplifier AMP. Connect the common terminal PAD to the first input terminal IN1. Switch the connection relationship between the first terminal of the compensation capacitor Cb and ground GND and power supply voltage VCC, that is, switch the first terminal of the compensation capacitor Cb to be connected to the power supply voltage VCC, and obtain the output signal of the output terminal of the amplifier AMP as the sensing signal Vout2.

[0096] Specifically, switch K7 (seventh switch) and switch K2 (second switch) are turned on, while switches K1 (first switch), K3 (third switch), K4 (fourth switch), K5 (fifth switch), and the sixth switch are turned off. The total charge in the circuit at this time is:

[0097] Q′=(V A2 -V CC C b +V A2 C X +(V A2 -V OUT2 C V

[0098] Since charge is conserved, Q = Q', then

[0099]

[0100] Where C X =C P +ΔC, C P The externally fixed parasitic capacitance value is given by ΔC, where C is the capacitance when the object approaches. X The change in capacitance.

[0101] In this embodiment, the voltage V at point A of the fixed potential terminal is... A2 With power supply voltage V CC Set at a ratio of 1:n.

[0102]

[0103] Correspondingly, when the compensation capacitor Cb is n times closer to the parasitic capacitance C P hour,

[0104]

[0105] In this way, theoretically, the area of ​​the compensation capacitor Cb can remain unchanged, while the actual effective compensation capacitance value provided is n times that of the compensation capacitor Cb. Of course, in practical applications, n will not take a large value, because a large value of n will significantly reduce the accuracy of the compensation capacitor. In some embodiments, n ranges from 2 to 3.

[0106] For example, if n = 2, V A2 =V CC / 2

[0107]

[0108] When twice the compensation capacitor Cb is close to the parasitic capacitance CP...

[0109]

[0110] When the variable capacitor ΔC = 0, the output signal V of the amplifier AMP is... OUT2 In V REF Nearby. When V REF When the value is set to 0, i.e., the reference voltage terminal is grounded and the variable capacitor ΔC = 0, the output signal V of the amplifier AMP is... OUT2 Near 0 voltage, when an object approaches, the change in the variable capacitor ΔC can be effectively reflected in the change of the output signal.

[0111] Embodiments of the present invention also provide a method using... Figure 3 The capacitance detection method of the capacitance sensing device shown.

[0112] Specifically, in this embodiment, the first detection module 1021 and the second detection module 1022 respectively perform the above-mentioned pre-charging and detection of the common terminal signal to obtain the first sensing signal V. OUT1 Second sensing signal V OUT2 ; the first sensing signal V OUT1 Second sensing signal V OUT2 Perform differential operations, convert the resulting analog signal to digital, and output the digital sensing signal D. OUT .

[0113] Specifically, the first detection module 1021 starts working first. During the pre-charging stage, it turns on the second switch K2, the fourth switch K4, the third switch K3 and the fifth switch K5, and turns off the first switch K1, the sixth switch K6 and the seventh switch K7. During the second stage, it turns on the seventh switch K7 and the first switch K1, and turns off the fifth switch K5, the sixth switch K6, the second switch K2, the third switch K3 and the fourth switch K4.

[0114]

[0115] After the first detection module 1021 completes its operation, the second detection module 1022 begins operation, entering the pre-charging process of the first detection module 1022. This involves turning on the sixth switch K6, the first switch K1, the third switch K3, and the fourth switch K4, while turning off the fifth switch K5, the seventh switch K7, and the second switch K2. In the second stage, the seventh switch K7 and the second switch K2 are turned on, while the first switch K1, the third switch K3, the fourth switch K4, and the fifth switch K5 are turned off. According to the law of conservation of charge...

[0116]

[0117] In other embodiments, the second detection module 1022 may operate first, followed by the first detection module 1021; or the electrical signal at the common terminal may be detected after the pre-charging processes of the two detection modules are completed sequentially.

[0118] Subtracting the two voltage signals yields the voltage difference signal, which is quantized by the analog-to-digital converter (ADC) of the subsequent signal processing module 103.

[0119]

[0120] In this embodiment, the signal processing module 103 has two input terminals, which are used to perform differential operations on the two input analog signals and then perform analog-to-digital conversion.

[0121] As can be seen from the above equation, the reference voltage VREF, which is a DC signal, has been canceled out. The output signal of the detection module 102 is independent of the reference voltage VREF. Therefore, the reference voltage VREF can take any value from 0 to VCC without affecting the sampling and quantization of the ADC in the subsequent signal processing module 103.

[0122] When V A2 =V CC / n and V A1 = (n-1)V CC When / n,

[0123]

[0124] For example, when n = 2, V A1 =Vcc / 2 and V A2 =V CC / 2 o'clock,

[0125]

[0126] Correspondingly, when n times the compensation capacitor Cb is close to the parasitic capacitance CP,

[0127]

[0128] Therefore, when V A1 With V A2 When set proportionally, it is possible to increase the compensation capacitor value by n times while keeping the area of ​​the compensation capacitor Cb constant, and at this time, the VREF voltage value does not need to be considered.

[0129] Embodiments of the present invention also provide a method for parasitic capacitance compensation multiplication.

[0130] Please refer to Figure 4 This is a flowchart illustrating a parasitic capacitance compensation and multiplication method according to an embodiment of the present invention.

[0131] The parasitic capacitance compensation and multiplication method includes the following steps:

[0132] Step S201: Provide a capacitance sensing device.

[0133] The structure of the capacitance sensing device is as described in the previous embodiments, and will not be repeated here.

[0134] Step S202: Set the ratio between the voltage at the fixed potential terminal and the power supply voltage to n-1:n, or 1:n, where n≥1.

[0135] Preferably, the value of n can be in the range of 2 to 3. Preferably, n is an integer.

[0136] When the capacitive sensing device includes only one detection module, the ratio of the fixed potential terminal voltage to the power supply voltage is (n-1):n, or 1:n.

[0137] When there are two detection modules, one detection module is connected to a fixed potential voltage with a power supply voltage ratio of n-1:n; the other detection module is connected to a fixed potential voltage with a power supply voltage ratio of 1:n.

[0138] Step S203: When the sensing capacitor does not change capacitance, acquire the sensing signal output by the real-time capacitance sensing device.

[0139] When the sensing capacitance Cx remains unchanged, Cx = Cp, where Cp is the integrated capacitor, meaning no object is near the sensing electrode. The sensing signal D is obtained when the initial compensation capacitance value is 0. OUT The sensing signal D here OUT With parasitic capacitance value C P correspond.

[0140] Step S204: Adjust the compensation capacitor value according to 1 / n times the magnitude of the sensing signal, so that the sensing signal output by the capacitive sensing device is equal to zero or as close to zero as possible.

[0141] Sensing signal D OUTDividing by n represents the sensing signal Dout / n corresponding to the required compensation capacitor. Based on the sensing signal Dout / n corresponding to the compensation capacitor value, the compensation capacitor value is adjusted sequentially within a range of configurable capacitor values, according to the capacitor compensation accuracy within the compensation module from large to small, so that the sensing signal output by the capacitance sensing device is equal to zero or as close to zero as possible, thereby obtaining a suitable compensation capacitor value Cb.

[0142] The capacitance sensing device and corresponding capacitance detection method in the above embodiments can achieve a multiplication of the compensation capacitance, providing an effective compensation capacitance value that is n times greater than the actual compensation capacitance value. Without increasing the actual compensation capacitance area, the effective compensation capacitance can be multiplied, improving the capacitance compensation effect. Especially when the external parasitic capacitance is large, the internal compensation capacitance with a small area can be used to compensate for the parasitic capacitance.

[0143] Embodiments of this application also provide an electronic device including the capacitive sensing device described in any of the above embodiments. The electronic device includes mobile phones, tablet computers, smart terminals, etc.

[0144] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, such as the combination of technical features between embodiments, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A capacitive sensing device, characterized in that, include: The common terminal is used to connect to the sensing electrode; At least one detection module, the detection module including an amplifier, the first input terminal of the amplifier being connected to the common terminal, the second input terminal being connected to a fixed potential terminal, and a feedback capacitor being connected between the first input terminal and the output terminal of the amplifier; The compensation module includes a compensation capacitor, the first end of which is connected to the first input terminal of the amplifier. The control module is used to control the compensation capacitor and the feedback capacitor to precharge within a single detection cycle, and then control the detection module to detect the electrical signal of the common terminal and output a sensing signal. During the detection process, based on the charge transfer of the precharge, the effective compensation capacitor value provided by the compensation module is greater than the actual capacitance value of the compensation capacitor. During pre-charging, the control module controls the amplifier's output terminal to be connected to a reference voltage terminal, both input terminals of the amplifier to a fixed potential terminal, and the first terminal of the sensing electrode and the compensation capacitor to be connected to a power supply voltage or ground. When detecting the electrical signal at the common terminal, the control module disconnects the amplifier from the reference voltage terminal and disconnects the first input terminal of the amplifier from the second input terminal, electrically connects the common terminal to the first input terminal of the amplifier, and switches the connection relationship between the second terminal of the compensation capacitor and ground or power supply voltage.

2. The capacitive sensing device according to claim 1, characterized in that, The compensation capacitor comprises several parallel capacitor arrays, the actual capacitance value of each capacitor array is adjustable, and the actual capacitance value of the compensation capacitor is the sum of the actual capacitance values ​​of each capacitor array.

3. The capacitive sensing device according to claim 2, characterized in that, The compensation capacitor includes at least two capacitor arrays with different capacitance adjustment accuracies.

4. The capacitive sensing device according to claim 1, characterized in that, Also includes: A signal processing module, connected to the output of the detection module, is used to convert the sensing signal output by the detection module into a digital sensing signal and output it.

5. The capacitive sensing device according to claim 1, characterized in that, The control module includes: a first switch connected between the second terminal of the compensation capacitor and ground; a second switch connected between the second terminal of the compensation capacitor and the power supply voltage; a third switch connected between the two input terminals of the amplifier; a fourth switch connected between the output terminal of the amplifier and the reference voltage terminal; a fifth switch connected between the common terminal and the power supply voltage; a sixth switch connected between the common terminal and ground; and a seventh switch connected between the common terminal and the first input terminal of the amplifier.

6. The capacitive sensing device according to claim 1, characterized in that, The reference voltage terminal is grounded.

7. The capacitive sensing device according to claim 1, characterized in that, The ratio of the voltage at the fixed potential terminal to the power supply voltage is 1:n or (n-1):n; the effective compensation capacitor value provided by the compensation module is n times the actual capacitance value of the compensation capacitor, where n≥1.

8. The capacitive sensing device according to claim 1, characterized in that, include: The two detection modules are a first detection module and a second detection module. The second input terminal of the amplifier of the first detection module is connected to a first fixed potential terminal, and the second input terminal of the amplifier of the second detection module is connected to a second fixed potential terminal.

9. The capacitive sensing device according to claim 8, characterized in that, The control module is used to control the two detection modules to output sensing signals sequentially.

10. The capacitive sensing device according to claim 8, characterized in that, The ratio of the voltage at the first fixed potential terminal to the power supply voltage is (n-1):n; the ratio of the voltage at the second fixed potential terminal to the power supply voltage is 1:n.

11. A capacitance detection method, characterized in that, include: Provide a capacitive sensing device as described in any one of claims 1 to 10; Within a single detection cycle, the compensation capacitor and the feedback capacitor are pre-charged, and then the detection module is controlled to detect the electrical signal at the common terminal and output a sensing signal.

12. The capacitance detection method according to claim 11, characterized in that, include: During pre-charging: the output terminal of the amplifier is electrically connected to the reference voltage terminal, and both input terminals are electrically connected to the fixed potential terminal; Connect the common terminal and the first terminal of the compensation capacitor to the power supply voltage, or ground both the common terminal and the first terminal of the compensation capacitor. When detecting the electrical signal at the common terminal: disconnect the amplifier from the reference voltage terminal and disconnect the two input terminals of the amplifier, electrically connect the common terminal to the first input terminal of the amplifier, switch the connection relationship between the first terminal of the compensation capacitor and ground and power supply voltage, and obtain the output signal of the amplifier's output terminal as the sensing signal.

13. The capacitance detection method according to claim 12, characterized in that, When the capacitive sensing device includes a first detection module and a second detection module, the first sensing signal and the second sensing signal output by the two detection modules are acquired respectively; the first sensing signal and the second sensing signal are differentially processed, and the analog signal after differential processing is processed to obtain a digital sensing signal.

14. An electronic device, characterized in that, include: The capacitive sensing device as described in any one of claims 1 to 10.

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