Capacitive sensing device and parasitic capacitance compensation method, electronic device

Abstract

The application discloses a capacitive sensing device and a parasitic capacitance compensation method thereof, and an electronic device. The capacitive sensing device comprises a sensing capacitor, an off-chip compensation module for providing an off-chip compensation capacitor, and a capacitance detection circuit for detecting the sensing capacitor and outputting a sensing signal corresponding to a capacitance change of the sensing capacitor according to capacitance values of the off-chip compensation capacitor and the sensing capacitor. The off-chip compensation module is located outside a chip where the capacitance detection circuit is located. When the sensing capacitor does not generate a capacitance change, the off-chip compensation capacitor makes the sensing signal output by the capacitance detection circuit less than a first threshold value. The capacitive sensing device has a large parasitic capacitance compensation range.

Description

Technical Field

[0001] This application relates to the field of sensing technology, specifically to a capacitance sensing device and a parasitic capacitance compensation 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] A capacitance detection circuit converts changes 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.

[0004] The capacitance (Cx) of a capacitive sensor consists of two parts: parasitic capacitance (Cp) and variable capacitance (Cx). C), where the parasitic capacitance Cp is a fixed capacitance value, and when a finger approaches the sensor, it causes the capacitance of the capacitive sensor to change. C changes.

[0005] Please refer to Figure 1 This is a schematic diagram of a capacitive sensor with a mutual capacitance structure. The sensing capacitance of the capacitor includes two plates, plate 11 and plate 12, and an inherent parasitic capacitance C is formed between the two plates. P Because the human body has a relatively large capacitance, its potential is equivalent to ground. When a finger approaches the sensor, the electric field lines between plates 11 and 12 are blocked by the hand, so the capacitance between the two plates of the sensing capacitor decreases, and its capacitance value becomes: By measuring C X By observing the changes in the finger's position, one can determine whether the finger has touched the object and where it has touched it.

[0006] In practical applications, the value of the parasitic capacitance Cp may be much larger than that of the variable capacitance. C, while the capacitor that is truly effective for sensing is the variable capacitor. The value of C. If the parasitic capacitance Cp is too large, it can easily cause the capacitance detection circuit to saturate, making it unable to detect the capacitance. The change of C. Therefore, in existing technologies, capacitive sensing devices typically include parasitic capacitance compensation functionality to compensate for the inherent parasitic capacitance of the sensor. By selecting a suitable compensation capacitor, the parasitic capacitance can be compensated for under varying capacitance conditions. When C=0, the output signal of the sensor is near zero, so when an object approaches, the variable capacitor... Changes in C can be effectively reflected in changes in the output signal.

[0007] In the prior art, when compensating for the parasitic capacitance, a capacitance compensation module is usually arranged inside the capacitance sensing chip. Due to the size and cost limitations of the chip, the size of the compensation capacitance that can be realized inside the chip is limited, usually within 200 pF. When the parasitic capacitance exceeds the compensation range inside the chip, the capacitance sensing device cannot work normally. SUMMARY

[0008] In view of this, the present application provides a capacitance sensing device and a parasitic capacitance compensation method, and an electronic device to solve the problem of small existing capacitance compensation range.

[0009] The technical scheme of the present application provides a capacitance sensing device, comprising: a sensing capacitor, the sensing capacitor comprising a first sensing electrode plate and a second sensing electrode plate; an off-chip compensation module for providing an off-chip compensation capacitor; a capacitance detection circuit connected to the off-chip compensation module and the first and second sensing electrode plates of the sensing capacitor, for outputting a sensing signal corresponding to the capacitance change of the sensing capacitor according to the capacitance values of the off-chip compensation capacitor and the sensing capacitor; wherein the off-chip compensation module is located outside the chip where the capacitance detection circuit is located, and when the sensing capacitor does not produce a capacitance change, the off-chip compensation capacitor makes the sensing signal output by the capacitance detection circuit less than a first threshold value, the first threshold value being a preset value greater than zero.

[0010] Optionally, the capacitance detection circuit further comprises: an on-chip compensation module for providing an on-chip compensation capacitor on the basis of the off-chip compensation capacitor, so that when the sensing capacitor does not produce a capacitance change, the sensing signal output by the capacitance detection circuit is further closer to zero on the basis of being less than the first threshold value.

[0011] Optionally, the on-chip compensation module comprises a plurality of on-chip capacitors connected in parallel, and the lower plate of each on-chip capacitor is connected to ground, and the upper plate of each on-chip capacitor is connected to a common terminal through a respective corresponding switch.

[0012] Optionally, the capacitance value of the off-chip compensation capacitor is fixed; and the capacitance value of the on-chip compensation capacitor is adjustable.

[0013] Optionally, the capacitance value of the off-chip compensation capacitor is less than the capacitance value of the parasitic capacitance of the sensing capacitor, and the capacitance value of the on-chip compensation capacitor is less than the capacitance value of the off-chip compensation capacitor.

[0014] Optionally, the on-chip compensation module further comprises a control unit for controlling the on-off state of each switch to adjust the capacitance value of the on-chip compensation capacitor according to the sensing signal output by the capacitance detection circuit when the sensing capacitor does not produce a capacitance change.

[0015] Optionally, the off-chip compensation module comprises a single external capacitor or a plurality of parallel external capacitors.

[0016] Optionally, one end of the external capacitor is grounded, and the other end is connected to the capacitance detection circuit; or both ends of the external capacitor are connected to the capacitance detection circuit.

[0017] Optionally, the capacitance detection circuit comprises a capacitance-to-analog module, which comprises a compensation processing unit, a detection unit and an analog output unit; the compensation processing unit is configured to obtain electrical signals of the off-chip compensation capacitor and the on-chip compensation capacitor, and output corresponding analog compensation signals according to the electrical signals; the detection unit is configured to obtain an electrical signal of the sensing capacitor, and output a corresponding analog detection signal; and the analog output unit is configured to output an analog sensing signal obtained by compensating the analog detection signal according to the analog compensation signal and the analog detection signal.

[0018] Optionally, the detection unit comprises a receiving unit and a sending unit, which are connected to the first sensing electrode plate and the second sensing electrode plate of the sensing capacitor, respectively; the sending unit is configured to send an excitation signal to the second sensing electrode plate, and the receiving unit is configured to receive an induced signal generated on the first sensing electrode plate due to the excitation signal.

[0019] Optionally, the capacitance detection circuit further comprises an analog-to-digital conversion module configured to convert the analog sensing signal into a digital sensing signal and output the digital sensing signal.

[0020] The technical scheme of the present application further provides a method for compensating for parasitic capacitance of the above-mentioned capacitance sensing device, which comprises: obtaining a sensing signal output by the capacitance detection circuit when the sensing capacitor does not generate a capacitance change; configuring a suitable off-chip compensation capacitor according to the sensing signal, so that the sensing signal output by the capacitance detection circuit is less than a first threshold value; and configuring a suitable on-chip compensation capacitor according to the sensing signal, so that the sensing signal output by the capacitance detection circuit is further close to zero on the basis of being less than the first threshold value.

[0021] Optionally, the method for configuring a suitable on-chip compensation capacitor comprises adjusting a capacitance value of the on-chip compensation capacitor provided by the on-chip compensation module according to the sensing signal output by the capacitance detection circuit when the sensing capacitor does not generate a capacitance change.

[0022] Optionally, the method for adjusting the capacitance value of the on-chip compensation capacitor provided by the on-chip compensation module comprises setting an initial value of the on-chip compensation capacitor to 0; and if the sensing signal is greater than 0, gradually increasing the value of the on-chip compensation capacitor within a range of a plurality of configurable capacitance values of the on-chip compensation capacitor until the sensing signal is equal to or closest to zero.

[0023] The technical scheme of the present application also provides an electronic device comprising the capacitive sensing device according to any one of the above.

[0024] The capacitive sensing device of the present application comprises an off-chip compensation module arranged outside the chip where the capacitive detection circuit is arranged, which can provide an off-chip compensation capacitor in a larger capacitive range, expand the range of the parasitic capacitance that can be compensated, and improve the application range of the capacitive sensing device.

[0025] Further, the capacitive sensing device can coarsely compensate the parasitic capacitance through the off-chip compensation module, and finely compensate the parasitic capacitance through the on-chip compensation module after the parasitic capacitance is compensated to a reasonable range, which can further improve the accuracy of the parasitic capacitance compensation. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort.

[0027] Figure 1 is a schematic diagram of a capacitive sensor of a self-capacitance structure according to an embodiment of the present application;

[0028] Figure 2a is a structural schematic diagram of a capacitive sensing device according to an embodiment of the present application;

[0029] Figure 2b is a structural schematic diagram of a capacitive sensing device according to an embodiment of the present application;

[0030] Figure 3 is a structural schematic diagram of an off-chip compensation module according to an embodiment of the present application;

[0031] Figure 4 is a structural schematic diagram of an on-chip compensation module according to an embodiment of the present application;

[0032] Figure 5 is a structural schematic diagram of a capacitive sensing device according to an embodiment of the present application;

[0033] Figure 6 is a flowchart of a parasitic capacitance compensation method according to an embodiment of the present application. DETAILED DESCRIPTION

[0034] With reference to the drawings, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative effort shall fall within the scope of the present application. In the case of no conflict, each of the described embodiments and technical features can be combined with each other.

[0035] Please refer to Figure 2a FIG. 1 is a structural schematic diagram of a capacitive sensing device according to an embodiment of the present application.

[0036] In this embodiment, the capacitive sensing device comprises a sensing capacitor 110, an off-chip compensation module 120 and a capacitive detection circuit 130.

[0037] In this embodiment, the sensing capacitor 110 is of a mutual capacitance structure, comprising a first sensing electrode plate and a second sensing electrode plate. The distance between the first sensing electrode plate and the second sensing electrode plate is fixed, forming a parasitic mutual inductance capacitor Cp. When a finger approaches either of the sensing electrode plates, the electric field lines between the two electrode plates are cut off, thereby reducing the capacitance value. Therefore, the capacitance value Cx of the sensing capacitor 110 is Cx=Cp-C. C, C is the capacitance change amount. When a finger approaches, C changes, C is exactly the quantity to be detected in the capacitive sensing detection process.

[0038] The off-chip compensation module 120 is configured to provide an off-chip compensation capacitor CB2. The capacitive detection circuit 130 is configured to detect the capacitance value Cx of the sensing capacitor 110, and output a sensing signal corresponding to the capacitance change amount C of the sensing capacitor according to the off-chip compensation capacitor CB2 and the capacitance value Cx of the sensing capacitor 110.

[0039] In this embodiment, the off-chip compensation module 120 and the sensing capacitor 110 are both located outside the chip 100, for example, a capacitive sensing chip, on which the capacitive detection circuit 130 is located. When the sensing capacitor 110 does not produce a capacitance change, the off-chip compensation capacitor CB2 makes the sensing signal output by the capacitive detection circuit 130 less than a first threshold value, which is a preset value greater than zero. In an embodiment, the chip on which the capacitive detection circuit 130 is located is attached to a PCB board. The sensing capacitor 110 and the off-chip compensation module 120 are also arranged on the PCB board. The off-chip compensation module 120 is connected to an external interface Cc of the chip 100 through an electrical connection on the PCB board. The two sensing electrode plates of the sensing capacitor 110 are respectively connected to the capacitive detection circuit 130 through external interfaces Rx and Tx of the chip 100. ​

[0040] The off-chip compensation module 120 can include a single external capacitor or multiple parallel external capacitors. Since the off-chip compensation module 120 is located outside the chip 100, it is not limited by the chip area, and the range of the capacitance of the optional capacitor is larger, thereby improving the range of the compensable parasitic capacitance. Since the off-chip compensation module 120 is arranged outside the chip, it is difficult to adjust, and therefore the off-chip compensation capacitor CB2 is usually a fixed value. In other embodiments, the off-chip compensation capacitor CB2 can also be a variable capacitor, but the capacitance compensation accuracy of the variable capacitor that can be arranged outside the chip is usually larger, and therefore the off-chip compensation capacitor CB2 has lower parasitic capacitance compensation accuracy. The capacitance compensation accuracy is the single-time adjustable compensation capacitor value.

[0041] In one embodiment, the off-chip compensation module 120 includes a single external capacitor, which uses a general discrete device capacitor, such as a ceramic patch capacitor. However, since the capacitance value of the discrete device is not arbitrarily selectable, the single capacitor can only select certain specific values, such as 100 pF, 220 pF, 330 pF, etc., and therefore the compensation range of the parasitic capacitance is limited.

[0042] In other embodiments, the off-chip compensation module 120 uses a multiple-capacitor combination structure. Please refer to Figure 3 , which is a structural schematic diagram of the off-chip compensation module 120 of an embodiment of the present application. The off-chip compensation module 120 includes n capacitors, which are C 11 , C 1n , C 11 , C 12 , and C 1n . The n capacitors are connected in parallel to provide the off-chip compensation capacitor CB2=C 11 +C 12 +……+C 1n . By using multiple capacitors in parallel to provide the off-chip compensation capacitor CB2, more values of the off-chip compensation capacitor CB2 can be selected.

[0043] In this embodiment, the first end of the off-chip compensation capacitor CB2 is grounded, and the other end is connected to the capacitor detection circuit 130. The capacitor detection circuit 130 obtains an electrical signal corresponding to the capacitance value of the off-chip compensation capacitor CB2 by acquiring a signal at one end of the off-chip compensation capacitor CB2.

[0044] In other embodiments, the two ends of the off-chip compensation capacitor CB2 are respectively connected to the capacitor detection circuit 130 through chip interfaces Cc1 and Cc2 (please refer to Figure 2b ). The capacitor detection circuit 130 obtains an electrical signal corresponding to the capacitance value of the off-chip compensation capacitor CB2 by acquiring signals at the two ends of the off-chip compensation capacitor CB2.

[0045] Since the capacitance value of the off-chip compensation capacitor CB2 provided by the off-chip compensation module 120 is a fixed value or has a large adjustable precision, the optimal compensation of the parasitic capacitance Cp of the sensing capacitor 110 cannot be achieved. When no object approaches the electrode plate of the sensing capacitor Cx, i.e., the capacitance variation of the sensing capacitor 110 is When the capacitance variation of the sensing capacitor 110 is equal to or close to 0, the off-chip compensation capacitor CB2 causes the sensing signal output by the capacitance detection circuit 130 to be less than the first threshold value. The off-chip compensation module 120 can be configured with an external capacitor of a suitable size according to the first threshold value. When setting the first threshold value, the first threshold value can correspond to the minimum capacitance compensation precision that can be adjusted by the off-chip compensation capacitor CB2, so that the signal output by the capacitance detection circuit 130 is as close to zero as possible in the case of compensating the parasitic capacitance only by the off-chip compensation capacitor CB2.

[0046] In this embodiment, in order to further improve the compensation effect of the parasitic capacitance (i.e., reduce the capacitance compensation precision), the capacitance detection circuit 130 further includes an on-chip compensation module 132 for providing an on-chip compensation capacitor CB1 on the basis of the off-chip compensation capacitor CB2, so that the sensing signal output by the capacitance detection circuit 130 is further close to zero on the basis of being less than the first threshold value when the sensing capacitor 110 does not produce a capacitance variation. In this embodiment, the off-chip compensation capacitor CB2 mainly compensates the parasitic capacitance Cp (offsets the parasitic capacitance Cp), and the on-chip compensation capacitor CB1 improves the compensation precision and further compensates the parasitic capacitance Cp. It is not difficult to understand that, in general, the capacitance value of the off-chip compensation capacitor CB2 is less than the capacitance value of the parasitic capacitance Cp, and the capacitance value of the on-chip compensation capacitor CB1 is less than the capacitance value of the off-chip compensation capacitor CB2.

[0047] Since the on-chip compensation module 132 is formed in the chip 100 where the capacitance detection circuit 130 is located and is formed by an integrated circuit process, the on-chip compensation module 132 adopts a smaller capacitance value and can provide a smaller on-chip compensation capacitor CB1, and the compensable range is limited. By jointly compensating the parasitic capacitance through the off-chip compensation module 120 and the on-chip compensation module 132, the compensable range can be improved and high-precision compensation can be achieved.

[0048] The capacitance detection circuit 130 further includes a capacitance-to-analog module 131 and an analog-to-digital conversion module ADC. The capacitance-to-analog module 131 is configured to output an analog sensing signal AOUT corresponding to the capacitance variation of the sensing capacitor 110 according to the sensing capacitor 110, the off-chip compensation capacitor CB2, and the on-chip compensation capacitor CB1. The analog-to-digital conversion module ADC is configured to convert the analog sensing signal into a digital sensing signal DOUT and output the digital sensing signal DOUT.

[0049] Please refer to Figure 4 This is a schematic diagram of the structure of the on-chip compensation module 132 according to an embodiment of the present invention.

[0050] The on-chip compensation module 132 includes a capacitor array 1321, comprising a plurality of on-chip capacitors C connected in parallel. 21 ~C 2n Furthermore, the lower plate of each capacitor within the chip is grounded, and the upper plate is connected to its respective switch K1~K. n It is connected to a common terminal, which is connected to the capacitance detection circuit 130 via interface Cs.

[0051] The capacitor array 1321 provides an on-chip compensation capacitor CB1. , where k i For switch K i The corresponding switching coefficient. k i When =0, switch K i Disconnect; k i When =1, switch K i When all switches are on, the capacitance of the capacitor array 1321 is at its maximum, providing on-chip compensation capacitor CB1=C. 21 +C 22 +……+C 2n When all switches are off, the capacitance of the capacitor array 1321 is zero.

[0052] The on-chip compensation module 132 can adjust the on-chip compensation capacitor CB1 as needed to achieve the best compensation effect. In this embodiment, the on-chip compensation module 132 also includes a control unit 1322, connected to the signal output terminal of the capacitor detection circuit 130, used to send signals to the switches K1~K according to the analog sensing signal AOUT or the digital sensing signal DOUT. n Output the corresponding control signals S1~S respectively n Based on the output signal of the capacitance detection circuit 130 when the sensing capacitor Cx does not change capacitance, the on / off state of each switch is controlled by forming various control signals S1~Sn, so as to adjust the capacitance value of the on-chip compensation capacitor CB1 provided by the final on-chip compensation module 132, so that the output signal of the sensing capacitor Cx when it does not change capacitance is equal to zero or as close to zero as possible.

[0053] The values ​​of the capacitors within the capacitor array 1321 can be set according to a certain pattern to facilitate the adjustment of the capacitance value of the on-chip compensation capacitor CB1. In one embodiment, C 21 <C 22 < <C 2n .

[0054] In other embodiments, the in-chip compensation module 132 can also be implemented by a current-mode DAC or other ways, and those skilled in the art can select appropriate ways to compensate the in-chip capacitance according to specific requirements, and provide equivalent in-chip compensation capacitance CB1.

[0055] The output value AOUT of the capacitance-to-analog module 131 has a linear relationship with CB1, CB2 and Cx.

[0056] In this embodiment, since the sensing capacitance is a mutual inductance capacitance, the compensation of the parasitic capacitance by the in-chip compensation capacitance CB1 and the out-chip compensation capacitance CB2 makes the analog sensing signal AOUT output by the capacitance-to-analog module 131 as follows:

[0057] Where b and c are determined by internal parameters of the capacitance detection circuit 130, such as the gain coefficient of the internal amplifier, the mirror ratio of the current mirror, etc. In some embodiments, b = c = 1.

[0058] When the variable capacitance of Cx changes by C = 0, by selecting appropriate CB1 and CB2, AOUT can be equal to or as close to zero as possible to achieve parasitic capacitance compensation. For a specific sensing capacitance Cx, CB1 and CB2 can be selected as follows: C = 0, first configure appropriate out-chip compensation capacitance CB2 so that AOUT or DOUT is less than a first threshold value, and the parasitic capacitance that has not been compensated is within the compensation range of the in-chip compensation capacitance CB1; then further adjust the in-chip compensation capacitance CB1 according to the sensing signal AOUT or DOUT so that AOUT or DOUT is equal to or as close to 0 as possible.

[0059] Please refer to Figure 5 for the structure schematic diagram of the capacitance sensing device of another embodiment of the present application.

[0060] In this embodiment, the capacitance-to-analog module 131 includes a compensation processing unit 1311, a detection unit 1312 and an analog output unit 1313.

[0061] In this embodiment, one end of the out-chip compensation capacitance CB2 is grounded, and the other end is connected to the compensation processing unit 1311; in another embodiment, both ends of the out-chip compensation capacitance CB2 are connected to the compensation processing unit 1311.

[0062] The compensation processing unit 1311 is configured to acquire the electrical signals of the out-chip compensation capacitance CB2 and the in-chip compensation capacitance CB1, and output corresponding analog compensation signals according to the electrical signals.

[0063] The detection unit 1312 is configured to acquire an electric signal corresponding to the capacitance of the sensing capacitor, and output a corresponding analog detection signal.

[0064] The detection unit 1312 further includes a receiving unit 1312a and a sending unit 1312b. The sending unit 1312b applies an excitation signal to one of the sensing plates of the sensing capacitor 110 through an interface Tx. Due to the mutual capacitance, the excitation signal can be sensed and received on the other sensing plate. The receiving unit 1312a receives the signal on the other sensing plate through a structure Rx. The size and phase shift of the signal received by the receiving unit 1312a are related to the frequency of the excitation signal sent by the sending unit 1312b and the size of the capacitance Cx.

[0065] The analog-to-digital conversion unit 1313 is configured to output an analog sensing signal AOUT after compensation of the analog detection signal according to the analog compensation signal output by the compensation processing unit 1311 and the analog detection signal output by the detection unit 1312. .

[0066] In some embodiments, the compensation processing unit 1311 and the detection module 1312 can convert the received electric signal into an analog voltage signal by using a frequency modulation circuit, an operational amplifier circuit or other means. The analog output unit 1313 outputs an analog sensing signal AOUT according to the analog compensation signal and the analog detection signal. Due to the compensation of the parasitic capacitance of the sensing capacitor Cx by the on-chip compensation capacitor CB1 and the off-chip compensation capacitor CB2, the analog sensing signal AOUT is only related to the capacitance change C.

[0067] The above-mentioned capacitive sensing device has an off-chip compensation module arranged outside the chip where the capacitive detection circuit is located. The off-chip compensation module can provide an off-chip compensation capacitor in a larger capacitance range, expand the range of compensable parasitic capacitance, and improve the application range of the capacitive sensing device.

[0068] Embodiments of the present application also provide an electronic device including the capacitive sensing device described in the above-mentioned embodiments. The electronic device includes a smart terminal device such as a mobile phone or a tablet computer.

[0069] Embodiments of the present application further provide a parasitic capacitance compensation method for the capacitive sensing device described in the above-mentioned embodiments.

[0070] Please refer to Figure 6 for a flowchart of the parasitic capacitance compensation method of an embodiment of the present application.

[0071] The parasitic capacitance compensation method includes the following steps:

[0072] Step S601: obtaining the sensing signal outputted by the capacitance detection circuit when the sensing capacitance does not change.

[0073] The sensing signal OUT can be a digital sensing signal DOUT outputted finally, or an analog sensing signal AOUT outputted by a capacitance analog conversion module in the capacitance detection circuit.

[0074] Step S602: providing a suitable off-chip compensation capacitance so that the sensing signal outputted by the capacitance detection circuit is less than the first threshold value.

[0075] Since the on-chip compensation capacitance is provided by the off-chip compensation module outside the chip where the capacitance detection circuit is located, the capacitance value of the off-chip compensation capacitance is not easy to adjust at any time according to the situation, and therefore the off-chip compensation capacitance usually adopts a fixed capacitance value. After obtaining a suitable off-chip compensation capacitance according to a specific sensing capacitance, the off-chip compensation capacitance value is fixedly used for off-chip compensation.

[0076] Step S603: providing a suitable on-chip compensation capacitance so that the sensing signal outputted by the capacitance detection circuit is further close to zero on the basis of being less than the first threshold value.

[0077] The method for adjusting the on-chip compensation capacitance includes: setting the initial value of the on-chip compensation capacitance as 0 in the case that the sensing capacitance does not change; if the sensing signal is greater than 0, gradually increasing the value of the on-chip compensation capacitance until the sensing signal is closest to zero in the adjustable range of the on-chip compensation capacitance.

[0078] In an embodiment, the on-chip compensation capacitance is provided by the capacitance array structure shown in FIG. 1, and specifically, the method for further searching for the suitable on-chip compensation capacitance on the basis of setting the off-chip compensation capacitance includes: Figure 4

[0079] (1) first disconnect all switches so that k1=k2=…k n =0, and the initial value of the off-chip capacitance CB1 is set as 0;

[0080] (2) close the switch K n (i.e. the switch K n is turned on), and detect the size of the sensing signal OUT outputted by the capacitance detection circuit 130, wherein the sensing signal OUT can be AOUT or DOUT:

[0081] If OUT>0, the switch K n is kept turned on, and k n =1; if OUT<0, the switch K n is disconnected, i.e. k n ​= 0;

[0082] (3) Close switch K n-1 , i.e. k n-1 = 1, and again detect the size of the output signal OUT of the capacitance detection circuit 130:

[0083] If OUT > 0, switch K n is kept on, k n-1 = 1 is kept; if OUT < 0, switch K n is turned off, i.e. kn-1 = 0;

[0084] (4) Close K n-2 , K n-2 , K1 in turn, and obtain all switch k i values according to the value of the output signal OUT, so as to obtain a suitable on-chip compensation capacitor , so that the output signal OUT is equal to 0 or closest to 0, thereby achieving the best parasitic capacitance compensation effect.

[0085] In other embodiments, further comprising: adjusting the on-chip compensation capacitor CB1 in different use environments. Due to the change of temperature and humidity in the use environment, the parasitic capacitance Cp will change. After the use environment changes, the on-chip compensation capacitor CB1 can be further adjusted by the method of step S603, to ensure the accuracy of the detection result of the capacitance detection device.

[0086] The above embodiments can further improve the accuracy of parasitic capacitance compensation and reduce or eliminate the influence of parasitic capacitance by rough compensation of the parasitic capacitance by the off-chip compensation capacitor (i.e. mainly compensating) and fine compensation of the parasitic capacitance by the on-chip compensation capacitor (further compensating the parasitic capacitance). Due to the high flexibility of the off-chip compensation capacitor, the compensable range of the parasitic capacitance can be improved, thereby improving the application range of the capacitance sensing device.

[0087] That is, the above only describes the embodiments of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent flow transformation using the content of the specification and drawings of the present application, such as the mutual combination of technical features between embodiments, or direct or indirect application in other related technical fields, is also included in the patent protection scope of the present application.

Claims

1. A capacitive sensing device, characterized in that, include: A sensing capacitor, the sensing capacitor comprising a first sensing plate and a second sensing plate; An off-chip compensation module is used to provide off-chip compensation capacitors; A capacitance detection circuit is connected to the off-chip compensation module and the first and second sensing plates of the sensing capacitor, and is used to output a sensing signal corresponding to the capacitance change of the sensing capacitor based on the capacitance values ​​of the off-chip compensation capacitor and the sensing capacitor. The off-chip compensation module is located outside the chip where the capacitance detection circuit is located. When the sensing capacitor does not change its capacitance, the off-chip compensation capacitor makes the sensing signal output by the capacitance detection circuit less than a first threshold. The first threshold is a preset value greater than zero. The capacitance detection circuit further includes an on-chip compensation module, which provides an on-chip compensation capacitor in addition to the off-chip compensation capacitor, so that when the sensing capacitor does not change capacitance, the sensing signal output by the capacitance detection circuit is further close to zero, which is less than the first threshold. The capacitance value of the off-chip compensation capacitor is less than the capacitance value of the parasitic capacitance of the sensing capacitor, and the capacitance value of the on-chip compensation capacitor is less than the capacitance value of the off-chip compensation capacitor. The off-chip compensation module includes: a single external capacitor or multiple external capacitors connected in parallel.

2. The capacitive sensing device according to claim 1, characterized in that, The on-chip compensation module includes several on-chip capacitors connected in parallel, and the lower plate of each on-chip capacitor is grounded, while the upper plate is connected to a common terminal through its respective switch.

3. The capacitive sensing device according to claim 1, characterized in that, The capacitance value of the external compensation capacitor is fixed; the capacitance value of the internal compensation capacitor is adjustable.

4. The capacitive sensing device according to claim 2, characterized in that, The on-chip compensation module also includes a control unit, which controls the on / off state of each switch according to the sensing signal output by the capacitance detection circuit when the sensing capacitor does not change capacitance, so as to adjust the capacitance value of the on-chip compensation capacitor.

5. The capacitive sensing device according to claim 1, characterized in that, One end of the external capacitor is grounded, and the other end is connected to the capacitance detection circuit; or, both ends of the external capacitor are connected to the capacitance detection circuit.

6. The capacitive sensing device according to claim 1, characterized in that, The capacitance detection circuit includes a capacitance-to-analog module, which further includes a compensation processing unit, a detection unit, and an analog output unit. The compensation processing unit acquires the electrical signals of the external compensation capacitor and the internal compensation capacitor, and outputs a corresponding analog compensation signal based on the electrical signals. The detection unit acquires the electrical signal of the sensing capacitor and outputs a corresponding analog detection signal. The analog output unit outputs an analog sensing signal after compensation of the analog detection signal based on the analog compensation signal and the analog detection signal.

7. The capacitive sensing device according to claim 6, characterized in that, The detection unit includes a receiving unit and a transmitting unit, which are respectively connected to the first sensing plate and the second sensing plate of the sensing capacitor; the transmitting unit is used to send an excitation signal to the second sensing plate, and the receiving unit is used to receive the sensing signal generated on the first sensing plate due to the excitation signal.

8. The capacitive sensing device according to claim 6, characterized in that, The capacitance detection circuit further includes an analog-to-digital converter module, used to convert the analog sensing signal into a digital sensing signal and output it.

9. A method for compensating parasitic capacitance in a capacitance sensing device, wherein the capacitance sensing device is as described in any one of claims 1 to 8, characterized in that, include: When the sensing capacitor does not change in capacitance, the sensing signal output by the capacitance detection circuit is acquired. Based on the sensing signal, a suitable off-chip compensation capacitor is configured so that the sensing signal output by the capacitor detection circuit is less than the first threshold. Based on the sensing signal, a suitable on-chip compensation capacitor is configured so that the sensing signal output by the capacitor detection circuit is further close to zero, which is already below the first threshold.

10. The parasitic capacitance compensation method according to claim 9, characterized in that, The method for configuring a suitable on-chip compensation capacitor includes: adjusting the capacitance value of the on-chip compensation capacitor provided by the on-chip compensation module based on the sensing signal output by the capacitance detection circuit when the sensing capacitor does not produce a capacitance change.

11. The parasitic capacitance compensation method according to claim 9, characterized in that, The method for adjusting the capacitance value of the on-chip compensation capacitor provided by the on-chip compensation module includes: setting the initial value of the on-chip compensation capacitor to 0; if the sensing signal is greater than 0, gradually increasing the value of the on-chip compensation capacitor within a range of several configurable capacitance values ​​until the sensing signal is equal to zero or closest to zero.

12. An electronic device, characterized in that, include: The capacitive sensing device as described in any one of claims 1 to 8.

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