Capacitive sensing device, parasitic capacitance compensation method, and electronic device

Abstract

The present application discloses a capacitance sensing device and a parasitic capacitance compensation method and an electronic device, wherein the capacitance sensing device comprises: a capacitance detection circuit, which is used to connect to a sensing capacitor and generate a sensing signal corresponding to the capacitance change value of the sensing capacitor; the capacitance detection circuit comprises a compensation module, which is used to provide a parasitic compensation capacitor to eliminate the influence of the parasitic capacitance of the sensing capacitor on the sensing signal; the compensation module comprises at least two compensation units with different capacitance compensation precisions, and the parasitic compensation capacitance value is the sum of the compensation capacitance values ​​provided by each compensation unit. The above-mentioned capacitance sensing device has a high requirement for the parasitic capacitance compensation precision.

Description

Technical Field

[0001] The present application relates to the field of sensor technology, and in particular to a capacitance sensor device, a parasitic capacitance compensation method, and an electronic device. Background Art

[0002] Capacitive sensor is a conversion device that converts the measured physical quantity or mechanical quantity into a change in capacitance. Capacitive sensor is widely used in industrial and consumer electronic products due to its simple structure, stable performance, high sensitivity and other advantages, such as: pressure, displacement, acceleration, thickness, liquid level and other measurements.

[0003] Through the capacitance detection circuit, the change in sensor capacitance can be converted into an electrical signal output. By measuring the size of the electrical signal, the size of the measured value can be determined. This is the basic working principle of the capacitive sensor. The capacitance (Cx) of the capacitive sensor consists of two parts, parasitic capacitance (Cp) and variable capacitance (ΔC), where the parasitic capacitance Cp is a fixed capacitance value. When the finger approaches the sensor, it will cause the variable capacitance ΔC of the capacitive sensor to change.

[0004] For a capacitive sensor with a self-capacitive structure, the self-capacitor has only one plate, and an inherent parasitic capacitance Cp is formed between the plate and the ground. When a finger approaches the sensor, a variable capacitance ΔC is formed between the finger and the sensor plate. Since the human body capacitance is relatively large, its potential is equivalent to the ground, so ΔC is related to the distance between the finger and the plate. By detecting the size of ΔC, it is possible to determine whether the finger is approaching or calculate the distance of the finger. For a capacitive sensor with a mutual capacitance structure, the mutual capacitance includes two plates, and an inherent parasitic capacitance CP is formed between the two plates. Since the human body capacitance is relatively large, its potential is equivalent to the ground. When a finger approaches the sensor, the electric field lines between the two plates are blocked by the hand, so the capacitance between the two plates of the sensing capacitor decreases, and its capacitance value becomes: C X =C P -ΔC. By measuring the change in Cx, it is possible to determine whether a finger is touching and where it is touching.

[0005] In practical applications, the value of parasitic capacitance Cp may be much larger than the variable capacitance ΔC, and the capacitance that is truly 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 capacitance detection circuit to saturate and fail to detect the change of ΔC. Therefore, it is necessary to compensate for the inherent parasitic capacitance of the sensor. The compensated parasitic capacitance Cp' is: CP' = Cp-Cb, where Cb is the compensation capacitance value.

[0006] Regardless of which capacitor structure is used for detection, the purpose of parasitic capacitance compensation is to find a suitable compensation capacitance value Cb so that Cp' is equal to or as close to 0 as possible, so that when the variable capacitance ΔC = 0, the output signal of the sensor device is near zero, so that when an object approaches, the change in the variable capacitance ΔC can be effectively reflected in the change of the output signal.

[0007] In the prior art, parasitic capacitance compensation is performed in a parasitic capacitance compensation module inside a chip where a capacitance detection circuit is located. The parasitic capacitance compensation module usually includes a capacitive DAC, which includes a capacitor array. The compensation capacitance value is adjusted by adjusting the capacitance value of the DAC capacitor array.

[0008] The capacitance compensation accuracy of the parasitic capacitance compensation method in the prior art needs to be further improved. Summary of the invention

[0009] In view of this, the present application provides a capacitance sensor device, a parasitic capacitance compensation method, and an electronic device to solve the problem of low accuracy of existing capacitance compensation.

[0010] The present application provides a capacitance sensing device, comprising: a capacitance detection circuit, connected to a sensing capacitor, generating a sensing signal corresponding to a capacitance change value of the sensing capacitor; the capacitance detection circuit comprising a compensation module, configured to provide a parasitic compensation capacitor to eliminate the influence of the parasitic capacitance of the sensing capacitor on the sensing signal; the compensation module comprising at least two compensation units with different capacitance compensation accuracies, the parasitic compensation capacitance value being the sum of the compensation capacitance values ​​provided by each compensation unit.

[0011] Optionally, the compensation module further includes: a control unit, configured to control the compensation capacitance value provided by each compensation unit according to a sensing signal generated by the capacitance detection circuit when the sensing capacitor does not generate a capacitance change.

[0012] Optionally, the compensation unit includes a capacitive DAC, which includes a capacitor array consisting of a plurality of capacitors, wherein a lower plate of each capacitor is grounded, and upper plates are connected to a common terminal through respective corresponding switches.

[0013] Optionally, each capacitor includes a plurality of unit capacitors connected in parallel, and different compensation units have different unit capacitance values. The greater the capacitance compensation accuracy, the greater the unit capacitance value in the compensation unit.

[0014] Optionally, the compensation unit includes at least one of a capacitive DAC, a current DAC or a resistor array.

[0015] Optionally, the capacitance detection circuit also includes: a capacitance-to-digital module, which is used to output a digital sensing signal corresponding to the change in sensing capacitance based on the electrical signal of the inductor capacitance and the compensation module; the capacitance-to-digital module includes: a capacitance-to-analog unit and an analog-to-digital conversion unit; the capacitance-to-analog unit is used to obtain the electrical signal of the sensing capacitance and the electrical signal output by the compensation module, and output an analog sensing signal corresponding to the change in sensing capacitance; the analog-to-digital conversion unit is connected to the capacitance-to-analog unit, and is used to perform analog-to-digital conversion on the analog sensing signal and output a digital sensing signal.

[0016] Optionally, the capacitance-to-analog unit includes: a compensation processing unit, a detection unit and an analog output unit; the compensation processing unit is used to obtain the electrical signal output by the compensation module, and output a corresponding analog compensation signal based on the electrical signal; the detection unit is used to obtain the electrical signal of the sensor capacitor and output a corresponding analog detection signal; the analog output unit is used to output an analog sensing signal after compensating the analog detection signal based on the analog compensation signal and the analog detection signal.

[0017] Optionally, a sensing capacitor is also included, and the sensing capacitor includes at least one of a self-capacitance structure and a mutual capacitance structure.

[0018] The technical solution of the present application also provides a parasitic capacitance compensation method for a capacitance sensing device, comprising: obtaining a sensing signal output by the capacitance detection circuit when no capacitance change is generated by the sensing capacitor; and adjusting the compensation capacitance value of each compensation unit in turn within a plurality of configurable capacitance value ranges according to the capacitance compensation accuracy from large to small according to the sensing signal, so that the sensing signal output by the capacitance detection circuit is equal to zero or is closest to zero.

[0019] Optionally, the method for adjusting the compensation capacitance value of the compensation unit includes: setting the initial compensation capacitance value of the compensation unit to 0; if the sensor signal is greater than 0, gradually increasing the value of the compensation capacitance within a configurable capacitance value range until the sensor signal is equal to zero or closest to zero.

[0020] The technical solution of the present application further provides an electronic device, comprising: a capacitive sensing device as described in any one of the above items.

[0021] The compensation module of the above-mentioned capacitance sensing device of the present application includes at least two compensation units with different capacitance compensation precisions. Coarse adjustment compensation is provided by a compensation unit with a larger capacitance compensation precision, and fine adjustment compensation is performed by a compensation unit with a smaller capacitance compensation precision to achieve the compensation precision requirement. Compared with the compensation unit that completely adopts a smaller capacitance compensation precision, reducing the capacitance compensation precision requirement of some compensation units can reduce the difficulty of designing the internal circuit of the compensation unit. And the compensation range that needs to be provided by the compensation unit with a smaller capacitance compensation precision is smaller, which can also reduce the design difficulty, thereby reducing the design difficulty on the premise of meeting the capacitance compensation precision requirement as a whole. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 is a structural diagram of a capacitive DAC according to an embodiment of the present application;

[0024] Figure 2 is a structural schematic diagram of a capacitive sensing device according to an embodiment of the present application;

[0025] Figure 3a is a structural schematic diagram of a first compensation unit of a capacitive sensing device according to an embodiment of the present application;

[0026] Figure 3b is a structural schematic diagram of a first compensation unit of a capacitive sensing device according to an embodiment of the present application;

[0027] Figure 4 is a structural schematic diagram of a capacitive sensing device according to an embodiment of the present application;

[0028] Figure 5 is a structural schematic diagram of a capacitive sensing device according to an embodiment of the present application;

[0029] Figure 6 1 is a flow chart of a parasitic capacitance compensation method of a capacitive sensing device according to an embodiment of the present application. DETAILED DESCRIPTION

[0030] As described in the background art, in the prior art, a parasitic capacitance compensation module is usually provided inside a chip where a capacitance detection circuit of a capacitance sensor device is located to perform parasitic capacitance compensation, and the compensation capacitance value is adjusted by adjusting the capacitance value of a capacitance array in a capacitive DAC.

[0031] Please refer to Figure 1, which is a schematic diagram of the structure of the capacitor array part of the capacitive DAC.

[0032] For an n-bit DAC, there are n capacitors C0 to C n-1 , one end of the n capacitors is grounded, and the other end is connected through switches K i Connect to the common terminal. Switch K i The state value k i =0 (Ki is disconnected) or k i =1(K i conduction).

[0033] The output signal of the capacitance detection circuit is linearly related to the capacitance value of the sensing capacitor and the capacitance array of the DAC:

[0034] DOUT=a·[Cx-b·(k0·C0+k1·C1K+k n-1 ·C n-1 )]

[0035] Among them, the size of a and b is determined by the capacitance detection circuit. Typically, a=b=1; C i =2 i Cu, Cu is the unit capacitance in DAC.

[0036] When all k i =0, the minimum value of compensation capacitance is 0; when all k i =1, the maximum compensation capacitance value is CC(max)=b·(2 n -1)·Cu; the capacitance compensation accuracy is: CC(step)=b·Cu.

[0037] When the parasitic capacitance of the external sensing capacitor is large and the accuracy of the parasitic capacitance compensation is very high, the capacitance DAC is required to have a higher accuracy, that is, the number of capacitors in the capacitor array is large. For example, when the parasitic capacitance of the external sensing capacitor is 200pF and the capacitance compensation accuracy is required to be 10fF, then:

[0038]

[0039] That is, the requirement (2 n -1)≥20000, we can get n≥15, which means the DAC accuracy is required to be at least 15 bits. When the capacitive DAC is 15 bits, the number of unit capacitors required is 2 15 -1=32767. Due to the limited chip area, setting so many capacitors inside the chip will make the layout and routing of the chip very difficult. At the same time, due to the inevitable process deviation in chip production, the value of the capacitor will be biased. Even if a sufficient number of unit capacitors are arranged, it is difficult to achieve the target capacitance compensation accuracy.

[0040] To this end, the inventors have proposed a new capacitance sensing device to further improve the capacitance compensation accuracy of parasitic capacitance.

[0041] The technical solutions in the embodiments of the present application are clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application. In the absence of conflict, the following embodiments and their technical features can be combined with each other.

[0042] Please refer to Figure 2 , is a schematic structural diagram of a capacitive sensing device according to an embodiment of the present invention.

[0043] In this embodiment, the capacitance sensing device includes a capacitance detection circuit 210, which is connected to the sensing capacitor and outputs a sensing signal corresponding to the capacitance change value of the sensing capacitor.

[0044] The capacitance detection circuit 210 is located in a chip 200, such as a capacitance sensor chip, and other circuit structures and components may also be formed in the chip 200, such as a power module, an interface device, etc. In one embodiment, the chip 200 where the capacitance detection circuit 130 is located is mounted on a PCB board, and the sensing capacitor is also arranged on the PCB board. The sensing capacitor is connected to the external interface of the chip 200 through an electrical connection on the PCB board, and capacitance sensing detection is performed through the capacitance detection circuit 210 in the chip 200.

[0045] The capacitance detection circuit 200 includes a compensation module 211, and the compensation module 211 is used to provide a parasitic compensation capacitor to eliminate the influence of the parasitic capacitance of the sensing capacitor on the sensing signal output by the capacitance sensing device.

[0046] The capacitance detection circuit 200 further includes a capacitance-to-digital (CDC) module 212 for outputting a digital sensing signal DOUT corresponding to a change in the sensing capacitance Cx according to the inductor capacitance Cx and the electrical signal of the compensation module 211 .

[0047] The compensation module 211 includes at least two compensation units with different capacitance compensation precisions, and the parasitic compensation capacitance value is the sum of the compensation capacitance values ​​provided by each compensation unit. In this embodiment, the compensation module 211 includes a first compensation unit 2112a and a second compensation unit 2112b, wherein the capacitance compensation precision of the first compensation unit 2112a is greater than the capacitance compensation precision of the second compensation unit 2112b. The capacitance compensation precision is a compensation capacitance value that can be adjusted once, and the smaller the capacitance compensation precision, the more accurate the compensation for parasitic capacitance.

[0048] The first compensation unit 2112a with greater capacitance compensation accuracy is used to coarsely adjust the compensation capacitance so that the uncompensated parasitic capacitance range is within the compensation range of the second compensation unit 2112b; the second compensation unit 2112b with less capacitance compensation accuracy is used to fine-tune the compensation capacitance so that the parasitic compensation capacitance finally provided by the compensation module 211 is closer to the parasitic capacitance of the sensing capacitor, thereby obtaining a higher compensation effect.

[0049] Since the various compensation units in the compensation module 211 have different capacitance compensation accuracies, compared with the compensation units that completely adopt the lower capacitance compensation accuracies, the capacitance compensation accuracies of some compensation units are reduced, thereby reducing the difficulty of designing the internal circuits of the compensation units. Moreover, the second compensation unit 2112b with the lower capacitance compensation accuracies needs to provide a smaller adjustable range of compensation capacitance values, which can also reduce the difficulty of designing the second compensation unit 2112b, thereby reducing the difficulty of designing the compensation module 211 on the premise of satisfying the capacitance compensation accuracies requirements as a whole.

[0050] Further, in this embodiment, the compensation module 211 also includes: a control unit 2111, connected to the capacitance detection circuit 210, for controlling the compensation capacitance value provided by each compensation unit according to the sensing signal generated by the capacitance detection circuit 210 when the sensing capacitor does not generate a capacitance change. The sensing signal can be the digital sensing signal DOUT finally output by the capacitance conversion (CDC) module 212, or it can be other intermediate signals corresponding to the capacitance value generated by the capacitance conversion (CDC) module 212 during the signal processing process, such as analog sensing signals.

[0051] When the sensing capacitance produces a capacitance change, the control unit 2111 adjusts the compensation capacitance provided by the first compensation unit 2112a and the second compensation unit 2112b. Specifically, the initial values ​​of the compensation capacitance provided by the first compensation unit 2112a and the second compensation unit 2112b are controlled to be 0, and then, according to the size of the sensing signal, the compensation capacitance value provided by the first compensation unit 2112a with a larger capacitance compensation accuracy is first adjusted, and the compensation capacitance value provided by the first compensation unit 2112a is gradually increased by controlling the internal parameters of the first compensation unit 2112a, until the sensing signal is closest to 0 within the adjustable capacitance value range of the first compensation unit 2112a, and the remaining parasitic capacitance to be compensated is within the compensable range of the second compensation unit 2112b; and then the compensation capacitance value provided by the second compensation unit 2112b with a smaller capacitance compensation accuracy is further controlled, so that the sensing signal is closest to 0 or equal to 0 within the adjustable capacitance value range of the second compensation unit 2112b.

[0052] In this embodiment, the first compensation unit 2112a plays a major role in compensating for parasitic capacitance (offsetting parasitic capacitance), and the second compensation unit 2112b plays a role in improving compensation accuracy and further compensating for parasitic capacitance. It is not difficult to understand that in general, the capacitance value of the first compensation unit 2112a is less than the capacitance value of the parasitic capacitance, and the capacitance value of the second compensation unit 2112b is less than the capacitance value of the first compensation unit 2112a.

[0053] The capacitance compensation accuracy of the compensation module 211 is determined by the minimum capacitance compensation accuracy of each compensation unit; and the compensable parasitic capacitance range of the compensation module 211 is determined by the compensation capacitance range that can be provided by the compensation unit with the maximum capacitance compensation accuracy in each compensation unit. The compensation range and capacitance compensation accuracy of each compensation unit can be reasonably set according to the actual compensation range and compensation accuracy requirements.

[0054] In other embodiments, the compensation module 211 may also include more than three compensation units, and the control unit 2111 may adjust the compensation capacitance value that can be provided by each compensation unit in sequence according to the compensation capacitance range accuracy from large to small, so that when the sensing capacitance value does not change, the sensing signal is equal to or closest to 0.

[0055] In some embodiments, the capacitive sensing device may further include a sensing capacitor, which may be integrated into the chip 200 or disposed outside the chip 200. The sensing capacitor may be at least one of a mutual inductance capacitor and a self-inductance capacitor. Those skilled in the art may select a suitable sensing capacitor according to actual needs, and may correspondingly set the internal structure of the capacitance-to-digital (CDC) module 212 according to the structure of the sensing capacitor, so as to detect different types of sensing capacitors.

[0056] In the embodiment of the present invention, the division of each functional module in the capacitive sensing device does not impose restrictions on its physical location, and each module or unit can be arranged on the same chip or on different chips. For example, the pressure sensing module 110 and the pressure detection circuit can be formed in the same chip or in two chips respectively, and the signal transmission between the chips is performed through the connection between the chips.

[0057] Please refer to Figure 3a and Figure 3b , respectively, are schematic structural diagrams of a first compensation unit 2112a and a second compensation unit 2112b according to an embodiment of the present invention.

[0058] In this embodiment, the first compensation unit 2112a and the second compensation unit 2112b both include a capacitive DAC. The capacitive DAC includes a capacitor array composed of a plurality of capacitors, each of which has a lower plate connected to ground and an upper plate connected to a common terminal via a switch.

[0059] Please refer to Figure 3a , which is a schematic diagram of the structure of the first compensation unit 2112a of the present invention.

[0060] In this embodiment, the first compensation unit 2112a is a capacitive DAC with an accuracy of m bits, including a capacitor array consisting of m capacitors connected in parallel, namely, capacitors CC0 to CC m-1 One end of the m capacitors is grounded, and the other end is connected to the ground through switches S0 to S1. m-1 Connect to a common terminal.

[0061] The control unit 2111 can control switches S0 to S m-1 The capacitance value of the capacitor array is adjusted by changing the conduction state of the capacitor array, and the size of the compensation capacitance value provided by the first compensation unit 2112a is related to the capacitance value of the capacitor array.

[0062] The capacitance value of the capacitor array of the first compensation unit 2112a is where s j For switch S j Status value: switch S j When disconnected, s j =0; switch S j When conducting, s j =1.

[0063] The capacitance in the first compensation unit 2112a is composed of a unit capacitance C u1 Composition, CC j =2 j ·C u1 .

[0064] Please refer to Figure 3b , is a schematic diagram of the structure of the second compensation unit 2112b of the present invention.

[0065] In this embodiment, the second compensation unit 2112b is a capacitive DAC with an accuracy of n bits, including a capacitor array consisting of n capacitors connected in parallel, namely, capacitors CF0 to CF n-1 One end of the n capacitors is grounded, and the other end is connected to the ground through switches K0~K n-1 Connect to a common terminal.

[0066] The control unit 2111 can control switches K0~K n-1The capacitance value of the capacitor array is adjusted by changing the conduction state of the capacitor array, and the size of the compensation capacitance value provided by the first compensation unit 2112a is related to the capacitance value of the capacitor array.

[0067] The capacitance value of the capacitor array of the second compensation unit 2112b is where k i For switch K i Status value: switch K i When disconnected, k i =0; switch K i When conducting, k i =1.

[0068] The capacitance in the second compensation unit 2112b is composed of a unit capacitance C u2 Composition, CF i =2 i ·C u2 .

[0069] The parasitic compensation capacitance value is equal to the sum of the compensation capacitances provided by the first compensation unit 2112a and the second compensation unit 2112b, that is, is related to the sum of the capacitance values ​​of the capacitor arrays of the first compensation unit 2112a and the second compensation unit 2112b.

[0070] In this embodiment, the parasitic compensation capacitance value b is determined by the internal parameters of the capacitance detection circuit 210 , such as the gain coefficient of the internal amplifier, the image ratio of the current mirror, etc.

[0071] Output sensor signal Both a and b are related to internal parameters of the circuit. In some embodiments, a=b=1.

[0072] When all switches in the first compensation unit 2112a and the second compensation unit 2112b are disconnected, that is, s j , k i are all equal to 0, the parasitic compensation capacitance value Cb provided by the compensation module 211 is the smallest, which is 0; when all switches are turned on, that is, all s j , k i are all equal to 1, the parasitic compensation capacitance value Cb provided by the compensation module 211 is the largest, and the maximum value of the parasitic compensation capacitance is The number of bits m and n of the capacitive DACs in the two compensation units may be the same or different.

[0073] The compensation accuracy of the first compensation unit 2112a depends on the unit capacitance C u1 , CC(step)=b·C u1 The compensation accuracy of the second compensation unit 2112b depends on the unit capacitance Cu2 , CF(step)=b·C u2 ; C u1 >C u2 , so that the capacitance compensation accuracy of the first compensation unit 2112a is greater than the capacitance compensation accuracy of the second compensation unit 2112b.

[0074] The smaller the unit capacitance, the smaller the capacitance compensation accuracy. Therefore, when the compensation accuracy requirement is high (that is, the smaller the compensation accuracy requirement), C u2 Much smaller than C u1 , so that Cb(max)=b·[(2 m -1)·C u1 +(2 n -1)·C u2 ]≈b·(2 m -1)·C u1 Therefore, the first compensation unit 2112a with the highest capacitance compensation accuracy determines the maximum value of the parasitic capacitance that can be compensated; and the second compensation unit 2112b with the lowest capacitance compensation accuracy determines the accuracy of the parasitic capacitance that can be compensated. CF(step)=b·C u2 .

[0075] The parasitic capacitance can be compensated to the range of the second compensation unit 2112b by the first compensation unit 2112a, and then the second compensation unit 2112b can be used to perform small precision compensation. In order to ensure the accuracy of compensation, the range of the second compensation unit 2112b is required to be greater than the unit capacitance C of the first compensation unit 2112a. u1 ,Right now

[0076] In one embodiment, when the external parasitic capacitance is large and the parasitic compensation accuracy is required to be very high, for example, the parasitic capacitance is about 200pF and the compensation accuracy is required to be 10fF, the first compensation unit 2112a can be set to use an 8-bit capacitive DAC, the second compensation unit 2112a can be set to use a 7-bit capacitive DAC, and b=1, C u1 =1pF, C u2 =10fF, the maximum compensation capacitance supported by the compensation module 211 The capacitance compensation accuracy is CF(step) = b·C u2 =10fF.

[0077] If a single DAC is used for compensation, the DAC accuracy required in the previous analysis is 15 bits. After adopting the solution of the present invention, only one 8-bit DAC and one 7-bit DAC are needed. The total number of unit capacitors required is reduced to 382, ​​which greatly reduces the requirements for DAC and simplifies the design. On the basis of achieving the high requirements for capacitor compensation accuracy, the chip area is reduced. In addition, the reduction in the number of capacitors can also reduce the impact of process deviations.

[0078] In other embodiments, the compensation module 211 may further include more than two compensation units with different capacitance compensation precisions, each compensation unit may include at least one structure of a capacitive DAC, a current DAC, or a resistor array, and different compensation capacitance values ​​may be provided equivalently by adjusting the capacitance value of the capacitor array in the capacitive DAC, the capacitance value of the current DAC, or the resistance value of the resistor array.

[0079] Please refer to Figure 4 , is a schematic structural diagram of a capacitance detection device according to another embodiment of the present invention.

[0080] In this embodiment, the capacitance-to-digital module 212 includes a capacitance-to-analog unit 2121 and an analog-to-digital conversion unit 2122 .

[0081] The capacitance-to-analog unit 2121 is used to obtain the electrical signal of the sensing capacitor Cx and the electrical signal output by the compensation module 211, and output an analog sensing signal AOUT corresponding to the variation of the sensing capacitor.

[0082] The analog-to-digital conversion unit 2122 is connected to the capacitance-to-analog conversion unit 2121 , and is configured to perform analog-to-digital conversion on the analog sensing signal AOUT and output a digital sensing signal DOUT.

[0083] In this embodiment, the control unit 2111 is connected to the output end of the capacitance-to-analog unit 2121, and is used to adjust the compensation capacitance of the first compensation unit 2112a and the second compensation unit 2112b according to the analog sensing signal AOUT output by the capacitance-to-analog unit 2121. In other embodiments, the control unit 2111 may also be connected to the analog-to-digital conversion unit 2122, and is used to adjust the compensation capacitance according to the digital sensing signal DOUT.

[0084] Please refer to Figure 5 , is a schematic structural diagram of a capacitance detection device according to another embodiment of the present invention.

[0085] In this embodiment, the capacitance-to-analog unit 2121 of the capacitance detection device further includes: a compensation processing unit 2121a, a detection unit 2121b and an analog output unit 2121c.

[0086] The compensation processing unit 2121a is used to obtain the electrical signal output by the compensation module 211, and output a corresponding analog compensation signal based on the electrical signal; the detection unit 2121b is used to obtain the electrical signal of the sensing capacitor Cx, and output a corresponding analog detection signal; the analog output unit 2121c is used to output an analog sensing signal AOUT after compensating the analog detection signal based on the analog compensation signal and the analog detection signal.

[0087] An embodiment of the present invention further provides an electronic device, wherein the electronic device has the capacitive sensing device described in the above embodiment. The electronic device includes a smart terminal device such as a mobile phone and a tablet computer.

[0088] An embodiment of the present invention further provides a parasitic capacitance compensation method for the above-mentioned capacitance sensor device.

[0089] Please refer to Figure 6 , is a flow chart of the parasitic capacitance compensation method in one embodiment of the present invention.

[0090] The parasitic capacitance compensation method comprises the following steps:

[0091] Step S601: When the sensing capacitor does not generate a capacitance change, obtaining a sensing signal output by the capacitance detection circuit.

[0092] The sensing signal may be a digital sensing signal DOUT which is finally output, or may be an analog sensing signal AOUT which is output by a capacitance analog conversion module in a capacitance detection circuit.

[0093] Step S602: According to the sensing signal, and in accordance with the capacitance compensation accuracy from large to small, the compensation capacitance value of each compensation unit is adjusted in sequence within a plurality of configurable capacitance value ranges, so that the sensing signal output by the capacitance detection circuit is equal to zero or is closest to zero.

[0094] Specifically, the method for adjusting the compensation capacitance value of the compensation unit includes: setting the initial compensation capacitance value of all compensation units to 0; if the sensor signal is greater than 0, gradually increasing the value of the compensation capacitance provided by the compensation unit within a range of several adjustable capacitance values ​​until the sensor signal is closest to zero.

[0095] In one embodiment of the present invention, when the variable part of the sensing capacitor Cx is close to zero, the compensation capacitance value provided by the first compensation unit 2112a is adjusted so that the output signal DOUT1 is greater than zero and close to zero. Thus, the state value s of each switch in the first compensation unit 2112a is determined. j .

[0096] Then, the compensation capacitance value provided by the second compensation unit 2112b is further adjusted so that the final output signal Further approaches zero, thereby determining the state value ki of the switch Ki.

[0097] In other embodiments, during the use of the capacitance sensor device, if the environment changes, the parasitic compensation capacitor provided by the compensation module can be further adjusted. Since the temperature and humidity in the use environment change, the parasitic capacitance of the sensor capacitor will change. After the use environment changes, the parasitic compensation capacitor provided by the compensation module can be further adjusted by the method of step S602 to ensure the accuracy of the detection result of the capacitance detection device.

[0098] 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 process transformation made using the contents of the specification and drawings of the present application, such as the mutual combination of technical features between the embodiments, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A capacitive sensing device, characterized in that: include: A capacitance detection circuit, connected to the sensing capacitor, generates a sensing signal corresponding to a capacitance change value of the sensing capacitor; The capacitance detection circuit includes a compensation module for providing a parasitic compensation capacitance to eliminate the influence of the parasitic capacitance of the sensing capacitor on the sensing signal; The compensation module includes at least two compensation units with different capacitance compensation accuracies, and the parasitic compensation capacitance value is the sum of the compensation capacitance values ​​provided by each compensation unit, wherein the at least two compensation units include a first compensation unit and a second compensation unit, the capacitance compensation accuracy of the first compensation unit is greater than the capacitance compensation accuracy of the second compensation unit, and the measuring range of the second compensation unit is greater than the unit capacitance of the first compensation unit.

2. The capacitive sensing device according to claim 1, characterized in that: The compensation module further includes: a control unit, configured to control the compensation capacitance value provided by each compensation unit according to a sensing signal generated by the capacitance detection circuit when the sensing capacitor does not generate a capacitance change.

3. The capacitive sensing device according to claim 1, characterized in that: The compensation unit comprises a capacitive DAC, which comprises a capacitive array composed of a plurality of capacitors, wherein the lower plate of each capacitor is grounded, and the upper plate is connected to a common terminal through respective corresponding switches.

4. The capacitive sensing device according to claim 3, characterized in that: Each capacitor includes a number of unit capacitors connected in parallel. Different compensation units have different unit capacitance values. The greater the capacitance compensation accuracy, the greater the unit capacitance value in the compensation unit.

5. The capacitive sensing device according to claim 1, characterized in that: The compensation unit includes at least one of a capacitive DAC, a current DAC or a resistor array.

6. The capacitive sensing device according to claim 1, characterized in that: The capacitance detection circuit also includes: a capacitance-to-digital module, which is used to output a digital sensing signal corresponding to the change in sensing capacitance according to the electrical signals of the inductor capacitance and the compensation module; the capacitance-to-digital module includes: a capacitance-to-analog unit and an analog-to-digital conversion unit; the capacitance-to-analog unit is used to obtain the electrical signal of the sensing capacitance and the electrical signal output by the compensation module, and output an analog sensing signal corresponding to the change in sensing capacitance; the analog-to-digital conversion unit is connected to the capacitance-to-analog unit, and is used to perform analog-to-digital conversion on the analog sensing signal and output a digital sensing signal.

7. The capacitive sensing device according to claim 6, characterized in that: The capacitance-to-analog unit includes: a compensation processing unit, a detection unit and an analog output unit; the compensation processing unit is used to obtain the electrical signal output by the compensation module, and output a corresponding analog compensation signal according to the electrical signal; the detection unit is used to obtain the electrical signal of the sensing capacitor and output a corresponding analog detection signal; the analog output unit is used to output an analog sensing signal after compensating the analog detection signal according to the analog compensation signal and the analog detection signal.

8. The capacitive sensing device according to claim 1, characterized in that: It also includes a sensing capacitor, which includes at least one of a self-capacitance structure and a mutual capacitance structure.

9. A parasitic capacitance compensation method for a capacitive sensor device, the capacitive sensor device being as claimed in any one of claims 1 to 8, characterized in that: include: When the sensing capacitor does not generate a capacitance change, obtaining a sensing signal output by the capacitance detection circuit; According to the sensing signal, the compensation capacitance value of each compensation unit is adjusted in sequence within a plurality of configurable capacitance value ranges according to the capacitance compensation accuracy from large to small, so that the sensing signal output by the capacitance detection circuit is equal to zero or closest to zero.

10. The parasitic capacitance compensation method according to claim 9, characterized in that: The method for adjusting the compensation capacitance value of the compensation unit includes: setting the initial compensation capacitance value of the compensation unit to 0; if the sensing signal is greater than 0, gradually increasing the compensation capacitance value within a configurable capacitance value range until the sensing signal is equal to zero or closest to zero.

11. An electronic device, characterized in that: include: A capacitive sensing device as claimed in any one of claims 1 to 8.

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