CN112234972A - Capacitance sensing device, parasitic capacitance compensation method and electronic equipment - Google Patents
Capacitance sensing device, parasitic capacitance compensation method and electronic equipment Download PDFInfo
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- CN112234972A CN112234972A CN202011148415.5A CN202011148415A CN112234972A CN 112234972 A CN112234972 A CN 112234972A CN 202011148415 A CN202011148415 A CN 202011148415A CN 112234972 A CN112234972 A CN 112234972A
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Abstract
The application discloses capacitance sensing device and parasitic capacitance compensation method thereof, an electronic device, the capacitance sensing device includes: a sensing capacitance; the off-chip compensation module is used for providing an off-chip compensation capacitor; the capacitance detection circuit is used for detecting a sensing capacitor and outputting a sensing signal corresponding to the capacitance change of the sensing capacitor according to the off-chip compensation capacitor and the capacitance value of the sensing capacitor; the off-chip compensation module is located outside a chip where the capacitance detection circuit is located, and when the capacitance change of the sensing capacitor is not generated, the off-chip compensation capacitor enables a sensing signal output by the capacitance detection circuit to be smaller than a first threshold value. The capacitance sensing device has a large parasitic capacitance compensation range.
Description
Technical Field
The present disclosure relates to the field of sensing technologies, and in particular, to a capacitance sensing device, a parasitic capacitance compensation method, and an electronic device.
Background
The capacitive sensor is a conversion device for converting a physical quantity or a mechanical quantity to be measured into capacitance change, and the capacitive sensor is widely applied to the fields of industrial and consumer electronic products due to the advantages of simple structure, stable performance, high sensitivity and the like, for example: pressure, displacement, acceleration, thickness, level, etc.
Through the capacitance detection circuit, the variation of the capacitance of the sensor can be converted into an electric signal to be output. The magnitude of the electrical signal is measured, and the magnitude of the measured quantity can be judged. This is the basic working principle of capacitive sensors.
The capacitance (Cx) of the capacitive sensor includes two parts, a parasitic capacitance (Cp) and a variable capacitance (Δ C), wherein the parasitic capacitance Cp is a fixed capacitance value, and when a finger approaches the sensor, the variable capacitance Δ C of the capacitive sensor changes.
Fig. 1 is a schematic diagram of a capacitive sensor with a mutual capacitance structure. The sensing capacitor of the capacitor comprises two polar plates, namely a polar plate 11 and a polar plate 12, wherein an inherent parasitic capacitance C is formed between the two polar platesP. Since the capacitance of the human body is relatively large and the potential is equal to ground, when a finger approaches the sensor, the electric field lines between the plate 11 and the plate 12 are blocked by the hand, so that the capacitance between the two plates of the sensing capacitor is reduced, and the capacitance value thereof becomes: cX＝CP- Δ C. By measuring CXThe change of the touch position can be judged according to whether the finger touches or not and the touch position.
In practical applications, the value of the parasitic capacitance Cp may be much larger than the value of the variable capacitance Δ C, while the capacitance really effective for sensing is the value of the variable capacitance Δ C. If the parasitic capacitance Cp is too large, the capacitance detection circuit is easily saturated and the change in Δ C cannot be detected. Therefore, in the conventional capacitive sensor device, a parasitic capacitance compensation function is usually provided to compensate for a parasitic capacitance inherent to the sensor, and an appropriate compensation capacitance is selected so that an output signal of the sensor device is in the vicinity of zero when the variable capacitance Δ C becomes 0, and thus, when an object approaches, a change in the variable capacitance Δ C can be effectively reflected in a change in the output signal.
When prior art carries out parasitic capacitance's compensation, set up the capacitance compensation module in capacitance sensing chip inside usually, because chip size and chip cost limit, the size of the compensation electric capacity that can realize inside the chip is limited, usually within 200pF, when parasitic capacitance surpassed the inside compensation scope of chip, the unable normal work of capacitance sensing device.
Disclosure of Invention
In view of this, the present application provides a capacitance sensing device, a parasitic capacitance compensation method, and an electronic apparatus, so as to solve the problem of a small capacitance compensation range in the prior art.
The technical scheme of the invention provides a capacitance sensing device, which comprises: the sensing capacitor comprises a first sensing polar plate and a second sensing polar plate; the off-chip compensation module is used for providing an off-chip compensation capacitor; the capacitance detection circuit is connected to the off-chip compensation module, and a first sensing polar plate and a second sensing polar plate of the sensing capacitor, and is used for outputting a sensing signal corresponding to the capacitance change of the sensing capacitor according to the off-chip compensation capacitor and the capacitance value of the sensing capacitor; the off-chip compensation module is located outside a chip where the capacitance detection circuit is located, and when the capacitance change of the sensing capacitor is not generated, the off-chip compensation capacitor enables a sensing signal output by the capacitance detection circuit to be smaller than a first threshold value, and the first threshold value is a preset value larger than zero.
Optionally, the capacitance detection circuit further includes: and the on-chip compensation module is used for providing an on-chip compensation capacitor on the basis of the off-chip compensation capacitor, so that when the capacitance change of the sensing capacitor is not generated, the sensing signal output by the capacitance detection circuit is further close to zero on the basis of being smaller than a first threshold value.
Optionally, the on-chip compensation module includes a plurality of on-chip capacitors connected in parallel, a lower electrode plate of each on-chip capacitor is grounded, and an upper electrode plate is connected to the common terminal through a corresponding switch.
Optionally, the capacitance value of the off-chip compensation capacitor is fixed; the capacitance value of the compensation capacitor in the chip is adjustable.
Optionally, a capacitance value of the off-chip compensation capacitor is smaller than a capacitance value of a parasitic capacitor of the sensing capacitor, and a capacitance value of the on-chip compensation capacitor is smaller than a capacitance value of the off-chip compensation capacitor.
Optionally, the on-chip compensation module further includes a control unit, configured to control on/off states of the switches according to a sensing signal output by the capacitance detection circuit when the capacitance of the sensing capacitor does not change, so as to adjust a capacitance value of the on-chip compensation capacitor.
Optionally, the off-chip compensation module includes: a single external capacitor or a plurality of external capacitors connected in parallel.
Optionally, one end of the external capacitor is grounded, and the other end of the external capacitor is connected to the capacitor detection circuit; or both ends of the external capacitor are connected to the capacitance detection circuit.
Optionally, the capacitance detection circuit includes: the electric capacity changes analog module, electric capacity changes analog module includes: the device comprises a compensation processing unit, a detection unit and an analog output unit; the compensation processing unit is used for acquiring electric signals of the off-chip compensation capacitor and the on-chip compensation capacitor and outputting corresponding analog compensation signals according to the electric signals; the detection unit is used for acquiring the electric signal of the sensing capacitor and outputting a corresponding analog detection signal; the analog output unit is used for outputting an analog sensing signal after compensating the analog detection signal according to the analog compensation signal and the analog detection signal.
Optionally, the detecting unit includes: the receiving unit and the sending unit are respectively connected to a first induction polar plate and a second induction polar plate of the sensing capacitor; the sending unit is used for sending an excitation signal to the second induction polar plate, and the receiving unit is used for receiving an induction signal generated on the first induction polar plate due to the excitation signal.
Optionally, the capacitance detection circuit further includes: and the analog-to-digital conversion module is used for converting the analog sensing signal into a digital sensing signal and outputting the digital sensing signal.
The technical solution of the present invention further provides a parasitic capacitance compensation method of the capacitance sensing device, including: when the capacitance change of the sensing capacitor is not generated, a sensing signal output by the capacitance detection circuit is obtained; configuring a proper off-chip compensation capacitor according to the sensing signal, so that the sensing signal output by the capacitor detection circuit is smaller than a first threshold value; and configuring a proper 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 smaller than a first threshold value.
Optionally, the method for configuring the appropriate on-chip compensation capacitor includes: and adjusting the capacitance value of the on-chip compensation capacitor provided by the on-chip compensation module according to the output sensing signal of the capacitance detection circuit when the capacitance change is not generated in the sensing capacitor.
Optionally, 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 be 0; if the sensing signal is greater than 0, gradually increasing the value of the on-chip compensation capacitor within a plurality of configurable capacitance values of the on-chip compensation capacitor until the sensing signal is equal to zero or closest to zero.
The technical scheme of the invention also provides electronic equipment which comprises the capacitance sensing device.
The capacitance sensing device comprises an off-chip compensation module which is arranged outside a chip where the capacitance detection circuit is arranged, and can provide off-chip compensation capacitance in a larger capacitance range, so that the range of compensable parasitic capacitance is expanded, and the application range of the capacitance sensing device is improved.
Furthermore, the capacitance sensing device can carry out coarse compensation on the parasitic capacitance through the off-chip compensation module, and after the parasitic capacitance is compensated to a reasonable range, the parasitic capacitance is finely compensated through the on-chip compensation module, so that the accuracy of parasitic capacitance compensation can be further improved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic diagram of a capacitive sensor of a self-capacitance configuration in accordance with an embodiment of the present application;
FIG. 2a is a schematic structural diagram of a capacitive sensing device according to an embodiment of the present application;
FIG. 2b is a schematic structural diagram of a capacitive sensing device according to an embodiment of the present application;
FIG. 3 is a schematic structural diagram of an off-chip compensation module according to an embodiment of the present application;
FIG. 4 is a schematic structural diagram of an on-chip compensation module according to an embodiment of the present application;
FIG. 5 is a schematic structural diagram of a capacitive sensing device according to an embodiment of the present application;
fig. 6 is a flowchart illustrating a parasitic capacitance compensation method according to an embodiment of the present application.
Detailed Description
The technical solutions in the embodiments of the present application are clearly and completely described below with reference to the accompanying drawings, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application. The following embodiments and their technical features may be combined with each other without conflict.
Fig. 2a is a schematic structural diagram of a capacitance sensing device according to an embodiment of the invention.
In this embodiment, the capacitance sensing device includes: a sensing capacitor 110, an off-chip compensation module 120, and a capacitance detection circuit 130.
In this embodiment, the sensing capacitor 110 is a mutual capacitor structure, and includes a first sensing plate and a second sensing plate, where the distance between the first sensing plate and the second sensing plate is fixed, so as to form a parasitic mutual capacitance Cp, and when a finger approaches any one of the sensing plates, the electric field lines between the two plates are cut off, so that the capacitance is reduced. Therefore, the capacitance value Cx of the sensor capacitor 110 is Cp- Δ C, and Δ C is a capacitance change amount. When the finger is close, Δ C changes, which is exactly the amount to be detected in the capacitive sensing detection process.
The off-chip compensation module 120 is configured to provide an off-chip compensation capacitor CB 2; the capacitance detection circuit 130 is configured to detect a capacitance value Cx of the sensing capacitor 110, and output a sensing signal corresponding to a capacitance variation Δ C of the sensing capacitor according to the off-chip compensation capacitor CB2 and the capacitance value Cx of the sensing capacitor 110.
The off-chip compensation module 120 and the sensing capacitor 110 are both located outside the chip 100 where the capacitance detection circuit 130 is located, for example, a capacitance sensing chip, and when the sensing capacitor 110 does not generate capacitance change, the off-chip compensation capacitor CB2 makes the sensing signal output by the capacitance detection circuit 130 smaller than a first threshold, where the first threshold is a preset value greater than zero. In one embodiment, the chip on which the capacitance detection circuit 130 is disposed is mounted on a PCB, the sensing capacitor 110 and the off-chip compensation module 120 are also disposed on the PCB, and the off-chip compensation module 120 is connected to the external interface Cc of the chip 100 through an electrical connection on the PCB. The two sensing plates of the sensing capacitor 110 are respectively connected to the capacitance detecting circuit 130 through the external interfaces Rx and Tx of the chip 100.
The off-chip compensation module 120 may include: a single external capacitor or a plurality of external capacitors connected in parallel. Since the off-chip compensation module 120 is located outside the chip 100, it is not limited by the chip area, and the capacitance range of the selectable capacitor is larger, thereby increasing the range of the parasitic capacitor that can be compensated. Since the off-chip compensation module 120 is disposed off-chip and is difficult to adjust, the off-chip compensation capacitor CB2 is usually a fixed value. In other embodiments, the off-chip compensation capacitor CB2 may be a variable capacitor, but the off-chip variable capacitor generally has higher capacitance compensation accuracy, so the off-chip compensation capacitor CB2 can achieve lower parasitic capacitance compensation accuracy. Wherein the capacitance compensation precision is a compensation capacitance value which can be adjusted once.
In one embodiment, the off-chip compensation module 120 includes a single external capacitor, using a common discrete device capacitor, such as a ceramic patch capacitor. However, since the capacitance values of discrete devices are not arbitrarily selectable, a single capacitance can only be selected to certain values, such as: 100pF, 220pF, 330pF, etc., and thus has a limited compensation range for parasitic capacitance.
In other embodiments, the off-chip compensation module 120 employs a plurality of capacitor combinations. Please refer to fig. 3, which is a schematic structural diagram of the off-chip compensation module 120 according to an embodiment of the present invention. The off-chip compensation module 120 includes n capacitors, each of which is C11～C1nThe n capacitors are connected in parallel to provide an off-chip compensation capacitor CB2 ═ C11+C12+……+C1n. The off-chip compensation capacitor CB2 is provided in parallel by using a plurality of capacitors, so that the selectable value of the off-chip compensation capacitor CB2 is more.
In this embodiment, a first end of the off-chip compensation capacitor CB2 is grounded, and the other end of the off-chip compensation capacitor CB2 is connected to the capacitance detection circuit 130, and the capacitance detection circuit 130 obtains an electrical signal corresponding to the capacitance value of the off-chip compensation capacitor CB2 by obtaining a signal at one end of the off-chip compensation capacitor CB 2.
In other embodiments, two ends of the off-chip compensation capacitor CB2 are respectively connected to the capacitance detection circuit 130 (see fig. 2b) through chip interfaces Cc1 and Cc2, and the capacitance detection circuit 130 obtains an electrical signal corresponding to the capacitance value of the off-chip compensation capacitor CB2 by obtaining signals at two ends of the off-chip compensation capacitor CB 2.
Since the off-chip compensation capacitor CB2 provided by the off-chip compensation module 120 has a fixed capacitance value or a high adjustable precision, the parasitic capacitance Cp of the sensor capacitor 110 cannot be optimally compensated. When no object approaches the electrode plate of the sense capacitance Cx, that is, when the capacitance change Δ C of the sense capacitance 110 is equal to or almost 0, the off-chip compensation capacitance CB2 makes the sense signal output by the capacitance detection circuit 130 smaller than the first threshold value. The off-chip compensation module 120 may be configured with an external capacitance of a suitable size according to the first threshold. When the first threshold is set, the first threshold may correspond to a minimum capacitance compensation accuracy that the off-chip compensation capacitor CB2 can adjust, so that the signal output by the capacitance detection circuit 130 is as close to zero as possible in the case where the parasitic capacitance is compensated only by the off-chip compensation capacitor CB 2.
In this embodiment, in order to further improve the compensation effect of the parasitic capacitance (i.e. reduce the capacitance compensation accuracy), the capacitance detection circuit 130 further includes an on-chip compensation module 132, which is configured to provide an on-chip compensation capacitance CB1 based on the off-chip compensation capacitance CB2, so that the sensing signal output by the capacitance detection circuit 130 is further close to zero based on being smaller than the first threshold when the capacitance change is not generated in the sensing capacitor 110. In this embodiment, the off-chip compensation capacitor CB2 plays a role of mainly compensating the parasitic capacitor Cp (canceling the parasitic capacitor Cp), and the on-chip compensation capacitor CB1 plays a role of improving the compensation accuracy, so as to further compensate the parasitic capacitor Cp. It is understood that, in general, the capacitance of the off-chip compensation capacitor CB2 is smaller than that of the compensation parasitic capacitor Cp, and the capacitance of the on-chip compensation capacitor CB1 is smaller than that of the off-chip compensation capacitor CB 2.
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 capacitance value adopted by the on-chip compensation module 132 is small, the capacitance value of the on-chip compensation capacitor CB1 which can be provided is also small, and the compensation range is limited. The off-chip compensation module 120 and the on-chip compensation module 132 perform parasitic capacitance compensation together, so that the compensation range can be increased, and high-precision compensation can be realized.
The capacitance detection circuit 130 further includes a capacitance conversion 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 a 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 CB 1. And the analog-to-digital conversion module ADC is used for converting the analog sensing signal into a digital sensing signal DOUT and outputting the digital sensing signal DOUT.
Please refer to fig. 4, which is a schematic structural diagram of the on-chip compensation module 132 according to an embodiment of the present invention.
The on-chip compensation module 132 includes a capacitorAn array 1321 including a plurality of on-chip capacitors C connected in parallel21～C2nThe lower pole plate of each capacitor in the chip is grounded, and the upper pole plates are respectively connected with the corresponding switches K1～KnIs connected to a common terminal, which is connected to the capacitance detection circuit 130 through an interface Cs.
The capacitor array 1321 provides an on-chip compensation capacitor CB1, CB1 ═ k1·C21+k2·C22+L L+kn·C2nWherein k isiIs a switch KiThe corresponding switching coefficient. k is a radical ofiWhen equal to 0, switch KiDisconnecting; k is a radical ofiWhen 1, switch KiAnd conducting. When all the switches are turned on, the capacitance value of the capacitor array 1321 is the largest, and the provided on-chip compensation capacitor CB1 is equal to C21+C22+……+C2n(ii) a When all switches are open, the capacitance value of the capacitor array 1321 is zero.
The on-chip compensation module 132 can adjust the on-chip compensation capacitor CB1 as required to achieve the best compensation effect. In this embodiment, the on-chip compensation module 132 further includes a control unit 1322 connected to the signal output terminal of the capacitance detection circuit 130, and configured to apply a signal to the switch K according to the analog sensing signal AOUT or the digital sensing signal DOUT1～KnRespectively output corresponding control signals S1～SnAccording to the output signal of the capacitance detection circuit 130 when the capacitance change of the sensing capacitance Cx does not occur, the on-off state of each switch is controlled by forming each control signal S1-Sn to adjust the capacitance value of the on-chip compensation capacitance CB1 provided by the final on-chip compensation module 132, so that the output signal when the capacitance change of the sensing capacitance Cx does not occur is equal to zero or as close to zero as possible.
The sizes of the capacitors in the capacitor array 1321 may be set according to a certain rule, so as to facilitate the adjustment of the capacitance value of the on-chip compensation capacitor CB 1. In one embodiment, C21<C22<……<C2n。
In other embodiments, the on-chip compensation module 132 may also be implemented by a current-mode DAC or other methods, and those skilled in the art may select an appropriate method to perform on-chip capacitance compensation according to specific requirements, so as to provide an equivalent on-chip compensation capacitor CB 1.
The output value AOUT of the capacitance conversion simulation module 131 is linearly related to CB1, CB2 and Cx.
In this embodiment, since the sensing capacitor is a mutual inductance capacitor, the parasitic capacitor is compensated by the on-chip compensation capacitor CB1 and the off-chip compensation capacitor CB2, so that the analog sensing signal AOUT output by the capacitance conversion simulation module 131 has the following formula:
AOUT is a · (Cx-b · CB1-c · CB2), where b and c are determined by internal parameters of the capacitance detection circuit 130, such as gain coefficients of internal amplifiers, mirror ratios of current mirrors, and the like. In some embodiments, b-c-1.
When the capacitance change amount Δ C of the variable capacitance of Cx is 0, by selecting appropriate CB1, CB2, AOUT can be made equal to zero or as close to zero as possible to achieve parasitic capacitance compensation. For a specific sensing capacitance Cx, when Δ C is equal to 0, an appropriate off-chip compensation capacitance CB2 may be configured first, so that AOUT or DOUT is smaller than a first threshold value, and the uncompensated parasitic capacitance is within the compensation range of the on-chip compensation capacitance CB 1; then, the on-chip compensation capacitor CB1 is further adjusted according to the sensing signal AOUT or DOUT, so that AOUT or DOUT is equal to or as close to 0 as possible.
Fig. 5 is a schematic structural diagram of a capacitance sensing device according to another embodiment of the invention.
In this embodiment, the capacitance conversion simulation module 131 includes: a compensation processing unit 1311, a detection unit 1312, and an analog output unit 1313.
In this embodiment, one end of the off-chip compensation capacitor CB2 is grounded, and the other end is connected to the compensation processing unit 1311; in another embodiment, both ends of the off-chip compensation capacitor CB2 are connected to the compensation processing unit 1311.
The compensation processing unit 1311 is configured to obtain electrical signals of the off-chip compensation capacitor CB2 and the on-chip compensation capacitor CB1, and output corresponding analog compensation signals according to the electrical signals.
The detection unit 1312 is configured to obtain an electrical signal of the sensing capacitor, where the electrical signal corresponds to a capacitance value of the sensing capacitor, and output a corresponding analog detection signal.
The detecting unit 1312 further includes a receiving unit 1312a and a transmitting unit 1312 b. The transmitting unit 1312b applies an excitation signal to one sensing plate of the sensing capacitor 110 through the interface Tx, the excitation signal can be sensed and received on the other sensing plate due to the existence of the mutual capacitance, the receiving unit 1312a receives a signal on the other sensing plate through the structure Rx, and the magnitude and the phase shift of the signal received by the receiving unit 1312a are related to the frequency of the excitation signal sent by the transmitting unit 1312b and the magnitude of the capacitance Cx.
The analog-to-digital conversion unit 1313 is configured to output an analog sensing signal AOUT compensated for 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, where AOUT is a (Cx-b · CB1-c · CB 2).
In some embodiments, the compensation processing unit 1311 and the detection module 1312 may use a frequency modulation circuit, an operational amplification circuit, or other methods to convert the received electrical signal into an analog voltage signal. 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 capacitance Cx by the on-chip compensation capacitance CB1 and the off-chip compensation capacitance CB2, the analog sensing signal AOUT is only related to the capacitance variation Δ C.
The capacitance sensing device is provided with the off-chip compensation module which is arranged outside a chip where the capacitance detection circuit is located, and can provide off-chip compensation capacitance in a larger capacitance range, so that the range of the compensable parasitic capacitance is expanded, and the application range of the capacitance sensing device is improved.
An embodiment of the present invention further provides an electronic device, including the capacitance sensing apparatus in the above embodiment. The electronic equipment comprises intelligent terminal equipment such as a mobile phone and a tablet personal computer.
Embodiments of the present invention further provide a parasitic capacitance compensation method of the capacitive sensing device in the above embodiments.
Fig. 6 is a schematic flow chart illustrating a parasitic capacitance compensation method according to an embodiment of the invention.
The parasitic capacitance compensation method comprises the following steps:
step S601: and when the capacitance change of the sensing capacitor is not generated, the sensing signal output by the capacitance detection circuit is obtained.
The sensing signal OUT may be a digital sensing signal DOUT which is finally output, or an analog sensing signal AOUT which is output by a capacitance analog conversion module in the capacitance detection circuit.
Step S602: and providing a proper off-chip compensation capacitor, so that the sensing signal output by the capacitance detection circuit is smaller than a first threshold value.
Because the off-chip compensation module outside the chip where the capacitance detection circuit is located provides the on-chip compensation capacitor, the capacitance value of the off-chip compensation capacitor is not easy to adjust at any time according to the situation, and therefore the off-chip compensation capacitor usually adopts a fixed capacitance value. After a proper off-chip compensation capacitor is obtained according to a specific sensing capacitor, the off-chip compensation capacitor value is fixedly adopted to carry out off-chip compensation.
And step S603, providing a proper on-chip compensation capacitor, so that the sensing signal output by the capacitance detection circuit is further close to zero on the basis of being smaller than the first threshold value.
The method for adjusting the on-chip compensation capacitance comprises the following steps: under the condition that the capacitance of the sensing capacitor is not changed, the method for adjusting the on-chip compensation capacitor comprises the following steps: setting the initial value of the on-chip compensation capacitor to be 0; and if the sensing signal is larger than 0, gradually increasing the value of the compensation capacitor in the chip until the sensing signal is closest to zero in the adjustable range of the compensation capacitor in the chip.
In one embodiment, the on-chip compensation capacitor is provided by the capacitor array structure shown in fig. 4, and specifically, the method for further finding the suitable on-chip compensation capacitor on the basis of setting the off-chip compensation capacitor includes:
(1) first all switches are opened so that k1＝k2＝……kn0, the initial value of off-chip capacitance CB1 is set to 0;
(2) closing switch Kn(i.e., switch K)nTurned on), the magnitude of the sensing signal OUT output by the capacitance detection circuit 130 is detected, where the sensing signal OUT may be AOUT or DOUT:
if OUT>0, switch KnIs kept on, kn1 is ═ 1; if OUT<0, opening KnI.e. kn＝0；
(3) Closing switch Kn-1I.e. kn-1The magnitude of the output signal OUT of the capacitance detection circuit 130 is detected again as 1:
if OUT>0, switch KnIs kept on, kn-1Holding as 1; if OUT<0, opening KnI.e., kn-1 ═ 0;
(4) in turn close Kn-2、Kn-2…、K1And deriving all switches k according to the value of the output signal OUTiValue to obtain a suitable on-chip compensation capacitance
The output signal OUT is made equal to 0 or closest to 0, thereby achieving the best parasitic capacitance compensation effect.
In other embodiments, further comprising: under different use environments, the on-chip compensation capacitor CB1 is adjusted. Since the parasitic capacitance Cp changes due to the change of the temperature and humidity in the usage environment, the on-chip compensation capacitor CB1 can be further adjusted by the method of step S603 after the usage environment changes, so as to ensure the accuracy of the detection result of the capacitance detection apparatus.
In the above embodiment, the off-chip compensation capacitor is used for performing coarse compensation (i.e. performing a main compensation function) on the parasitic capacitor, and then the on-chip compensation capacitor is used for performing fine compensation (further compensating the parasitic capacitor), so that the accuracy of the parasitic capacitor compensation can be further improved, and the influence of the parasitic capacitor can be reduced or eliminated. The flexibility of the arrangement of the off-chip compensation capacitor is higher, so that the compensation range of the parasitic capacitor can be enlarged, and the application range of the capacitance sensing device is enlarged.
That is, the above description is only an embodiment of the present application, and not intended to limit the scope of the present application, and all equivalent structures or equivalent flow transformations made by using the contents of the specification and the drawings, such as mutual combination of technical features between various embodiments, or direct or indirect application to other related technical fields, are included in the scope of the present application.
Claims (15)
1. A capacitive sensing device, comprising:
the sensing capacitor comprises a first sensing polar plate and a second sensing polar plate;
the off-chip compensation module is used for providing an off-chip compensation capacitor;
the capacitance detection circuit is connected to the off-chip compensation module, and a first sensing polar plate and a second sensing polar plate of the sensing capacitor, and is used for outputting a sensing signal corresponding to the capacitance change of the sensing capacitor according to the off-chip compensation capacitor and the capacitance value of the sensing capacitor;
the off-chip compensation module is located outside a chip where the capacitance detection circuit is located, and when the capacitance change of the sensing capacitor is not generated, the off-chip compensation capacitor enables a sensing signal output by the capacitance detection circuit to be smaller than a first threshold value, and the first threshold value is a preset value larger than zero.
2. The capacitance sensing device according to claim 1, wherein the capacitance detection circuit further comprises: and the on-chip compensation module is used for providing an on-chip compensation capacitor on the basis of the off-chip compensation capacitor, so that when the capacitance change of the sensing capacitor is not generated, the sensing signal output by the capacitance detection circuit is further close to zero on the basis of being smaller than a first threshold value.
3. The capacitance sensing device according to claim 2, wherein the on-chip compensation module comprises a plurality of on-chip capacitors connected in parallel, and a lower plate of each on-chip capacitor is grounded, and an upper plate is connected to the common terminal through a corresponding switch.
4. The capacitive sensing device of claim 2, wherein the off-chip compensation capacitor has a fixed capacitance value; the capacitance value of the compensation capacitor in the chip is adjustable.
5. The capacitive sensing device of claim 2, wherein the off-chip compensation capacitor has a capacitance value less than a capacitance value of a parasitic capacitor of the sensing capacitor, and the on-chip compensation capacitor has a capacitance value less than a capacitance value of the off-chip compensation capacitor.
6. The capacitance sensing device according to claim 3, wherein the on-chip compensation module further comprises a control unit, configured to control on/off states of the switches according to a sensing signal output by the capacitance detection circuit when the capacitance of the sensing capacitor does not change, so as to adjust a capacitance value of the on-chip compensation capacitor.
7. The capacitive sensing device of claim 1, wherein the off-chip compensation module comprises: a single external capacitor or a plurality of external capacitors connected in parallel.
8. The capacitance sensing device according to claim 7, wherein the external capacitor has one end connected to ground and the other end connected to the capacitance detection circuit; or both ends of the external capacitor are connected to the capacitance detection circuit.
9. The capacitance sensing device according to claim 1, wherein the capacitance detection circuit comprises: the electric capacity changes analog module, electric capacity changes analog module includes: the device comprises a compensation processing unit, a detection unit and an analog output unit; the compensation processing unit is used for acquiring electric signals of the off-chip compensation capacitor and the on-chip compensation capacitor and outputting corresponding analog compensation signals according to the electric signals; the detection unit is used for acquiring the electric signal of the sensing capacitor and outputting a corresponding analog detection signal; the analog output unit is used for outputting an analog sensing signal after compensating the analog detection signal according to the analog compensation signal and the analog detection signal.
10. The capacitance sensing device according to claim 9, wherein the detection unit comprises: the receiving unit and the sending unit are respectively connected to a first induction polar plate and a second induction polar plate of the sensing capacitor; the sending unit is used for sending an excitation signal to the second induction polar plate, and the receiving unit is used for receiving an induction signal generated on the first induction polar plate due to the excitation signal.
11. The capacitive sensing device of claim 9, wherein the capacitance detection circuit further comprises: and the analog-to-digital conversion module is used for converting the analog sensing signal into a digital sensing signal and outputting the digital sensing signal.
12. A method of compensating for parasitic capacitance of a capacitive sensing device according to any one of claims 2 to 11, comprising:
when the capacitance change of the sensing capacitor is not generated, a sensing signal output by the capacitance detection circuit is obtained;
configuring a proper off-chip compensation capacitor according to the sensing signal, so that the sensing signal output by the capacitor detection circuit is smaller than a first threshold value;
and configuring a proper 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 smaller than a first threshold value.
13. The parasitic capacitance compensation method according to claim 12, wherein the method of configuring the appropriate on-chip compensation capacitance comprises: and adjusting the capacitance value of the on-chip compensation capacitor provided by the on-chip compensation module according to the output sensing signal of the capacitance detection circuit when the capacitance change is not generated in the sensing capacitor.
14. The parasitic capacitance compensation method according to claim 12, wherein the method of 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 be 0; if the sensing signal is greater than 0, gradually increasing the value of the on-chip compensation capacitor within a plurality of configurable capacitance values of the on-chip compensation capacitor until the sensing signal is equal to zero or closest to zero.
15. An electronic device, comprising:
a capacitance sensing device as claimed in any one of claims 1 to 11.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113031081A (en) * | 2021-03-10 | 2021-06-25 | 维沃移动通信有限公司 | Proximity sensing detection circuit, capacitance calibration method and device and electronic equipment |
| CN114113801A (en) * | 2022-01-24 | 2022-03-01 | 上海艾为微电子技术有限公司 | Capacitance detection method and capacitance detection device |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113031081A (en) * | 2021-03-10 | 2021-06-25 | 维沃移动通信有限公司 | Proximity sensing detection circuit, capacitance calibration method and device and electronic equipment |
| CN114113801A (en) * | 2022-01-24 | 2022-03-01 | 上海艾为微电子技术有限公司 | Capacitance detection method and capacitance detection device |
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