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] The present application relates to the technical field of sensing, in particular to a capacitive sensing device, a parasitic capacitance compensation method and an electronic device. BACKGROUND

[0002] A capacitive sensor is a kind of conversion device that converts a measured physical or mechanical quantity into a capacitance change. The capacitive sensor is widely used in industrial and consumer electronic product fields due to its simple structure, stable performance, high sensitivity and other advantages, such as pressure, displacement, acceleration, thickness, liquid level measurement, etc.

[0003] The change amount of the sensor capacitance can be converted into an electrical signal output through a capacitive detection circuit. The size of the electrical signal can be determined to determine the size of the measured quantity. This is the basic working principle of the capacitive sensor.

[0004] The capacitance (Cx) of the capacitive sensor includes two parts, a parasitic capacitance (Cp) and a variable capacitance (ΔC), Cx=Cp+ΔC, wherein the parasitic capacitance Cp is a fixed capacitance value, and when a finger approaches the sensor, the variable capacitance ΔC of the capacitive sensor changes.

[0005] Please refer to Figure 1 for a schematic diagram of a capacitive sensor with a self-capacitance structure. The capacitive sensor has only one electrode plate 11, and an inherent parasitic capacitance Cp is formed between the electrode plate 11 and the ground 10. When a finger approaches the sensor, a variable capacitance ΔC is formed between the finger and the electrode plate 11 of the sensor. Since the body capacitance is relatively large, its potential is equivalent to the ground, and therefore ΔC is related to the distance between the finger and the electrode plate. By detecting the size of ΔC, it can be determined whether the finger is approaching or the distance between the finger and the capacitive sensor can be calculated.

[0006] In practical applications, the value of the parasitic capacitance Cp may be much larger than the variable capacitance ΔC, and the capacitance that is actually effective for sensing is the value of the variable capacitance ΔC. If the parasitic capacitance Cp is too large, it is easy to cause the capacitive detection circuit to be saturated, and the change of ΔC cannot be detected. Therefore, in the prior art, the capacitive sensing device usually has a parasitic capacitance compensation function to compensate for the inherent parasitic capacitance of the sensor. By selecting a suitable compensation capacitance Cb1, the output signal of the sensing device is near zero when the variable capacitance ΔC=0, so that the change of the variable capacitance ΔC when an object approaches can be effectively reflected in the change of the output signal.

[0007] When the prior art compensates for the parasitic capacitance, a capacitance compensation module is usually set inside the capacitive 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 capacitive sensing device cannot work normally. SUMMARY

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

[0009] The capacitive sensing device provided by the application comprises a sensing capacitor, an off-chip compensation module for providing an off-chip compensation capacitor, and a capacitor detection circuit for detecting the sensing capacitor and outputting a sensing signal corresponding to a change in the capacitance of the sensing capacitor according to 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 capacitor detection circuit is located. When the sensing capacitor does not change in capacitance, the off-chip compensation capacitor causes the sensing signal output by the capacitor detection circuit to be less than a first threshold value, which is a preset value greater than zero.

[0010] Optionally, the capacitor 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 change in capacitance, the sensing signal output by the capacitor detection circuit is further close 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 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 stray 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 connected to the capacitor detection circuit for controlling the on-off state of each switch according to the sensing signal output by the capacitor detection circuit when the sensing capacitor does not change in capacitance, so as to adjust the capacitance value of the on-chip compensation capacitor.

[0015] Optionally, the sensing capacitor is a self-capacitance structure comprising an induction plate, and the induction plate is connected to the capacitor detection circuit.

[0016] Optionally, the off-chip compensation module comprises a single external capacitor or a plurality of parallel external capacitors.

[0017] 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.

[0018] Optionally, the capacitance detection circuit comprises a capacitance-to-analog conversion module, which comprises a compensation processing unit, a detection unit and an analog output unit, the compensation processing unit is configured to acquire 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 acquire 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 after compensation of the analog detection signal according to the analog compensation signal and the analog detection 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 solution of the application further provides a method for compensating for parasitic capacitance of a capacitance sensing device, which comprises the following steps: acquiring 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, 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 in 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 solution of the application further provides an electronic device comprising the capacitance sensing device according to any one of the above.

[0024] The capacitance sensing device of the application comprises an off-chip compensation module arranged outside a chip where the capacitance detection circuit is arranged, which 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 capacitance sensing device.

[0025] Further, the capacitive sensing device can perform coarse compensation on the stray capacitance through an off-chip compensation module, and perform fine compensation on the stray capacitance through an on-chip compensation module after the stray capacitance is compensated to a reasonable range, so as to further improve the accuracy of stray 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 labor.

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

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

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

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

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

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

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

[0034] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. In the case of no conflict, each of the following embodiments and technical features can be combined with each other.

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

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

[0037] Figure 2a The sensing capacitor 110 is schematically shown as a capacitor Cx. The sensing capacitor 110 is a self-capacitance structure, comprising one sensing electrode plate connected to the capacitor detection circuit 130, and a parasitic capacitor formed between the sensing electrode plate and the ground. In other embodiments, the sensing capacitor 110 can also comprise two electrode plates, one of which is a sensing electrode plate connected to the capacitor detection circuit 130, and the other of which is grounded as a ground terminal. The capacitance value of the sensing capacitor 110 is Cx=Cp+AC; where Cp is a parasitic capacitance, including a fixed capacitance between the sensing electrode plate and the ground and a parasitic capacitance generated by other circuit structures, and AC is a capacitance variation, which changes when a finger approaches the sensing capacitor, and AC 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; and the capacitor 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 variation AC of the sensing capacitor according to the off-chip compensation capacitor CB2 and the capacitance value Cx of the sensing capacitor 110.

[0039] In the embodiment, the off-chip compensation module 120 and the sensing capacitor 110 are both located outside the chip 100, e.g. a capacitive sensing chip, on which the capacitor detection circuit 130 is located, and when the sensing capacitor 110 does not generate a capacitance variation, the off-chip compensation capacitor CB2 causes the sensing signal output by the capacitor detection circuit 130 to be less than a first threshold value, which is a preset value greater than zero. In an embodiment, the chip on which the capacitor detection circuit 130 is located is mounted on a PCB, and the sensing capacitor 110 and the off-chip compensation module 120 are also arranged on the PCB. The off-chip compensation module 120 is connected to an external interface Cc of the chip 100 through an electrical connection on the PCB. The sensing electrode plate of the sensing capacitor 110 is connected to the capacitor detection circuit 130 through an external interface Cs 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 since the capacitance compensation accuracy of the variable capacitor arranged outside the chip is usually large, the off-chip compensation capacitor CB2 can achieve a 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 , the n capacitors are connected in parallel to provide an 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, the value of the off-chip compensation capacitor CB2 can be selected more.

[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 the capacitance compensation precision is relatively large, the optimal compensation of the parasitic capacitance Cp of the sensing capacitor 110 cannot be achieved. When there is no object close to the electrode plate of the sensing capacitor 110, that is, the capacitance variation AC of the sensing capacitor 110 is equal to or almost 0, the off-chip compensation capacitor CB2 makes the sensing signal output by the capacitance detection circuit 130 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 (that is, to 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 when the sensing capacitor 110 does not produce capacitance variation, 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. In this embodiment, the off-chip compensation capacitor CB2 mainly compensates the parasitic capacitance Cp (offsets the parasitic capacitance Cp), the on-chip compensation capacitor CB1 reduces the capacitance compensation precision and improves the compensation precision to further compensate the parasitic capacitance Cp. It is not difficult to understand that generally 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 integrated circuit technology, the on-chip compensation module 132 adopts a smaller capacitance value and can provide a smaller on-chip compensation capacitor CB1, and the compensation range is limited. By jointly compensating the parasitic capacitance through the off-chip compensation module 120 and the on-chip compensation module 132, the compensation 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 corresponding grounding switch K1~K1. 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, CB1 = k1·C 21 +k2·C 22 +L L+k n ·C 2n , 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 an 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 to K2 according to the analog sensing signal AOUT or the digital sensing signal DOUT. n Output the corresponding control signals S1 to S2 respectively. n Based on the output signal of the capacitance detection circuit 130 when the sensing capacitor Cx does not change capacitance, control signals S1 to S2 are generated. n The on / off state of each switch is controlled 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 no capacitance change occurs 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, C21 <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 self-induction capacitance, the parasitic capacitance of the sensing capacitance 110 is compensated by the in-chip compensation capacitance CB1 and the out-chip compensation capacitance CB2, so that the analog sensing signal AOUT output by the capacitance-to-analog module 131 is as follows:

[0057] AOUT=a·(Cx-b·CB1-c·CB2), where b and c are determined by the 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 ΔC=0, by selecting appropriate CB1 and CB2, AOUT can be equal to zero or as close to zero as possible, thereby achieving parasitic capacitance compensation. For a specific sensing capacitance Cx, when ΔC=0, first configure appropriate out-chip compensation capacitance CB2 so that AOUT or DOUT is less than a first threshold, 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 electrical signals of the off-chip compensation capacitor CB2 and the on-chip compensation capacitor CB1, and output analog compensation signals related to CB2 and CB1 according to the electrical signals; the detection unit 1312 is configured to acquire an electrical signal of the sensing capacitor Cx, and output an analog detection signal related to the sensing capacitor Cx according to the electrical signal; and the analog-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 and the analog detection signal, AOUT=a·(Cx-b·CB1-c·CB2).

[0063] In some embodiments, the compensation processing unit 1311 and the detection unit 1312 can convert the received electrical signals into analog voltage signals in a frequency modulation circuit, an operational amplifier circuit or other ways. 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 ΔC.

[0064] The above-mentioned capacitive sensing device has an off-chip compensation module arranged outside the chip where the capacitive detection circuit is located, which 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.

[0065] Embodiments of the present application also provide an electronic device comprising the capacitive sensing device described in the above-mentioned embodiments. The electronic device includes a smart terminal device such as a mobile phone, a tablet computer, etc.

[0066] Embodiments of the present application further provide a parasitic capacitance compensation method for the capacitive sensing device described in the above-mentioned embodiments.

[0067] Please refer to Figure 6 for a flowchart of the parasitic capacitance compensation method of an embodiment of the present application.

[0068] The parasitic capacitance compensation method comprises the following steps:

[0069] Step S601: acquiring a sensing signal output by the capacitive detection circuit when the sensing capacitor does not generate a capacitance change.

[0070] The sensing signal OUT can be a digital sensing signal DOUT finally output, or an analog sensing signal AOUT output by a capacitive analog conversion module in the capacitive detection circuit.

[0071] Step S602: Provide a suitable off-chip compensation capacitor so that the sensing signal output by the capacitor detection circuit is less than the first threshold.

[0072] Since the on-chip compensation capacitor is provided by an off-chip compensation module located outside the chip where the capacitance detection circuit is located, the capacitance value of the off-chip compensation capacitor is not easily adjusted according to the situation. Therefore, the off-chip compensation capacitor usually uses a fixed capacitance value. After obtaining a suitable off-chip compensation capacitor based on the specific sensing capacitance, the off-chip compensation capacitor value is fixed and used for off-chip compensation.

[0073] Step S603: Provide a suitable on-chip compensation capacitor so that the sensing signal output by the capacitor detection circuit is further close to zero, based on the fact that it is less than the first threshold.

[0074] The method for adjusting the on-chip compensation capacitor includes: when the sensing capacitor does not change in capacitance, the method for adjusting the on-chip compensation capacitor 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 until the sensing signal is zero or closest to zero within the adjustable range of the on-chip compensation capacitor.

[0075] In one embodiment, the on-chip compensation capacitor is composed of Figure 4 The capacitor array structure shown provides, specifically, a method for further finding suitable on-chip compensation capacitors based on the established off-chip compensation capacitors, including:

[0076] (1) First, disconnect all switches so that k1 = k2 = ... k n =0, the initial value of the external capacitor CB1 is set to 0;

[0077] (2) Close switch K n (i.e., switch K) n (Conducted), the magnitude of the sensing signal OUT output by the capacitance detection circuit 130 is detected, wherein the sensing signal OUT can be AOUT or DOUT:

[0078] If OUT>0, switch K n Maintain conduction, k n =1; if OUT<0, disconnect K. n That is, kn = 0;

[0079] (3) Close switch K n-1 , i.e., k n-1 =1, and then check the magnitude of the output signal OUT of the capacitance detection circuit 130 again:

[0080] If OUT>0, switch K nKeep on, kn-1=1; if OUT<0, turn off Kn-1, i.e. kn-1=0;

[0081] (4) Close K n-2 , K n-2 …K1 in turn, and get all switch k i values according to the value of output signal OUT, so as to get appropriate on-chip compensation capacitor so that the output signal OUT is equal to 0 or closest to 0, thereby achieving the best parasitic capacitor compensation effect.

[0082] 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 capacitor Cp will change. After the change of the use environment, 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 capacitor detection device.

[0083] The above embodiments can further improve the accuracy of parasitic capacitor compensation and reduce or eliminate the influence of parasitic capacitor by rough compensation of parasitic capacitor through off-chip compensation capacitor (i.e. main compensation effect) and fine compensation of parasitic capacitor through on-chip compensation capacitor (further compensation of parasitic capacitor). Due to the high flexibility of off-chip compensation capacitor, the compensable range of parasitic capacitor can be improved, thereby improving the application range of the capacitor sensing device.

[0084] That is, the above description is only an embodiment 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 by, The application relates to a sensor capacitor, an off-chip compensation module for providing an off-chip compensation capacitor, a capacitor detection circuit for detecting the sensor capacitor and outputting a sensor signal corresponding to a change in the capacitance of the sensor capacitor according to the capacitance values of the off-chip compensation capacitor and the sensor capacitor. The off-chip compensation module is located outside the chip where the capacitor detection circuit is located, and when the sensor capacitor does not generate a capacitance change, the off-chip compensation capacitor makes the sensor signal output by the capacitor detection circuit less than a first threshold value, the first threshold value is a preset value greater than zero, and the capacitance value of the off-chip compensation capacitor is less than the capacitance value of the parasitic capacitance of the sensor capacitor. The capacitor 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, and the capacitance value of the on-chip compensation capacitor is less than the capacitance value of the off-chip compensation capacitor. The on-chip compensation module makes the sensor signal output by the capacitor detection circuit further close to zero on the basis of being less than the first threshold value when the sensor capacitor does not generate a capacitance change. 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 grounded, and the upper plate is connected to a common end through a corresponding switch. The capacitance value of the off-chip compensation capacitor is fixed, and the capacitance value of the on-chip compensation capacitor is adjustable.

2. The capacitive sensing device of claim 1, wherein, The on-chip compensation module further comprises a control unit connected to the capacitor detection circuit for controlling the on-off state of each switch according to the sensor signal output by the capacitor detection circuit when the sensor capacitor does not generate a capacitance change, so as to adjust the capacitance value of the on-chip compensation capacitor.

3. The capacitive sensing device of claim 2, wherein, The sensor capacitor is a self-capacitance structure comprising an induction plate, and the induction plate is connected to the capacitor detection circuit.

4. The capacitive sensing device of claim 2, wherein, The off-chip compensation module comprises a single external capacitor or a plurality of parallel external capacitors.

5. The capacitive sensing device of claim 3, wherein, One end of the external capacitor is grounded, and the other end is connected to the capacitor detection circuit; or both ends of the external capacitor are connected to the capacitor detection circuit.

6. The capacitive sensing device of claim 1, wherein, The capacitor detection circuit comprises a capacitance-to-analog module, the capacitance-to-analog module comprises a compensation processing unit, a detection unit and an analog output unit, the compensation processing unit is used for acquiring the electric signal of the off-chip compensation capacitor and the on-chip compensation capacitor, and outputting a corresponding analog compensation signal according to the electric signal; the detection unit is used for detecting the electric signal of the sensor capacitor and outputting a corresponding analog detection signal; and the analog output unit is used for outputting an analog sensor signal after the analog detection signal is compensated according to the analog compensation signal and the analog detection signal.

7. The capacitive sensing device of claim 1, wherein, The capacitor detection circuit further comprises an analog-to-digital conversion module for converting the analog sensor signal into a digital sensor signal and outputting the same.

8. The capacitive sensing device of claim 7, wherein, The application relates to a sensor capacitor, an off-chip compensation module for providing an off-chip compensation capacitor, a capacitor detection circuit for detecting the sensor capacitor and outputting a sensor signal corresponding to a change in the capacitance of the sensor capacitor according to the capacitance values of the off-chip compensation capacitor and the sensor capacitor.

9. The capacitive sensing device of claim 1, wherein, The off-chip compensation module is located outside the chip where the capacitor detection circuit is located, and when the sensor capacitor does not generate a capacitance change, the off-chip compensation capacitor makes the sensor signal output by the capacitor detection circuit less than a first threshold value, the first threshold value is a preset value greater than zero, and the capacitance value of the off-chip compensation capacitor is less than the capacitance value of the parasitic capacitance of the sensor capacitor.

10. The capacitive sensing device of claim 9, wherein, The capacitor 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, and the capacitance value of the on-chip compensation capacitor is less than the capacitance value of the off-chip compensation capacitor.

11. A method of compensating for parasitic capacitance of a capacitive sensing device, the capacitive sensing device being as defined in any one of claims 1 to 10, characterized by, The on-chip compensation module makes the sensor signal output by the capacitor detection circuit further close to zero on the basis of being less than the first threshold value when the sensor capacitor does not generate a capacitance change. 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 grounded, and the upper plate is connected to a common end through a corresponding switch. The capacitance value of the off-chip compensation capacitor is fixed, and the capacitance value of the on-chip compensation capacitor is adjustable. The on-chip compensation module further comprises a control unit connected to the capacitor detection circuit for controlling the on-off state of each switch according to the sensor signal output by the capacitor detection circuit when the sensor capacitor does not generate a capacitance change, so as to adjust the capacitance value of the on-chip compensation capacitor. The sensor capacitor is a self-capacitance structure comprising an induction plate, and the induction plate is connected to the capacitor detection circuit. The off-chip compensation module comprises a single external capacitor or a plurality of parallel external capacitors. One end of the external capacitor is grounded, and the other end is connected to the capacitor detection circuit; or both ends of the external capacitor are connected to the capacitor detection circuit. The capacitor detection circuit comprises a capacitance-to-analog module, the capacitance-to-analog module comprises a compensation processing unit, a detection unit and an analog output unit, the compensation processing unit is used for acquiring the electric signal of the off-chip compensation capacitor and the on-chip compensation capacitor, and outputting a corresponding analog compensation signal according to the electric signal; the detection unit is used for detecting the electric signal of the sensor capacitor and outputting a corresponding analog detection signal; and the analog output unit is used for outputting an analog sensor signal after the analog detection signal is compensated according to the analog compensation signal and the analog detection signal. The capacitor detection circuit further comprises an analog-to-digital conversion module for converting the analog sensor signal into a digital sensor signal and outputting the same. The application relates to a sensor capacitor, an off-chip compensation module for providing an off-chip compensation capacitor, a capacitor detection circuit for detecting the sensor capacitor and outputting a sensor signal corresponding to a change in the capacitance of the sensor capacitor according to the capacitance values of the off-chip compensation capacitor and the sensor capacitor. According to the sensing signal, a suitable on-chip compensation capacitor is configured, so that the sensing signal output by the capacitance detection circuit further approaches zero on the basis of being less than a first threshold value.

12. The method of parasitic capacitance compensation according to claim 11, wherein, The method for configuring a suitable on-chip compensation capacitor comprises: adjusting the 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 produce a capacitance change.

13. The method of parasitic capacitance compensation according to claim 12, wherein, The method for adjusting the capacitance value of the on-chip compensation capacitor provided by the on-chip compensation module comprises: setting the initial value of the on-chip compensation capacitor to 0; if the sensing signal is greater than 0, gradually increasing the on-chip compensation capacitor value in a range of several configurable capacitance values of the on-chip compensation capacitor until the sensing signal is equal to or closest to zero.

14. An electronic device, comprising: Comprise: The capacitive sensing device according to any one of claims 1 to 10.

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