Capacitance detection circuit, detection method and electronic equipment

Abstract

A capacitance detection circuit, detection method and electronic device, the circuit includes a control module, a variable capacitance module and an integration module; the control module includes a control input terminal and a control output terminal, the control input terminal is connected to the input terminal of the integration module, and the control output terminal is connected to the output terminal of the integration module, and is used to output a signal corresponding to the capacitance value of the capacitance to be detected according to the integrated charge on the integration module; the variable capacitance module includes at least one switching capacitor, one end of the switching capacitor is connected to the control input terminal, and the other end is connected to the power supply voltage or ground according to the capacitance control signal; the input terminal of the integration module is also connected to the output terminal of the capacitance to be detected, and is used to realize the charge integration on the capacitor plate to be detected. By adding a variable capacitance module, the capacitance value in the capacitance detection circuit can be increased, the feedback coefficient of the capacitance detection circuit can be reduced, and the stability of the circuit can be improved.

Description

Technical Field

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

[0002] Capacitance detection circuits are usually used in products such as SAR SENSOR (SAR sensor), touch detection and in-ear detection to measure the change of capacitance value. In different products, the capacitance value of the capacitance to be measured varies greatly. For example, in a small touch circuit board, the capacitance of the self-inductance capacitance to be measured is only a few pico-farads, while in a large touch screen, the capacitance of the self-inductance capacitance to be measured can reach hundreds of pico-farads.

[0003] Since the feedback coefficient of the capacitance detection circuit is inversely proportional to the capacitance value of the capacitor to be detected, when the capacitance value of the external input capacitor to be detected varies greatly with the specific product, the feedback coefficient of the capacitance detection circuit also varies greatly, resulting in inconsistent system performance and poor stability. Summary of the invention

[0004] In view of this, the present application provides a capacitance detection circuit, a detection method and an electronic device to solve the problem that the capacitance value of the capacitor to be detected varies greatly with the specific product, resulting in inconsistent system performance and poor stability in the existing capacitance detection circuit.

[0005] A capacitance detection circuit provided by the present application includes: a control module, a variable capacitance module and an integration module; the control module includes a control input end and a control output end, the control input end is connected to the input end of the integration module, and the control output end is connected to the output end of the integration module, and is used to output a signal corresponding to the capacitance value of a capacitance to be detected according to the integrated charge on the integration module; the variable capacitance module includes at least one switching capacitor, one end of the switching capacitor is connected to the control input end, and the other end is connected to a power supply voltage or ground according to a capacitance control signal; the input end of the integration module is also connected to the output end of the capacitance to be detected, and is used to realize the charge integration on the capacitor plate to be detected.

[0006] Optionally, the variable capacitor module also includes at least one capacitor control switch, the number of the capacitor control switches corresponds to the number of the switch capacitors and is connected one-to-one, the first end of the capacitor control switch is connected to one end of the switch capacitor, and the second end of the capacitor control switch is connected to the power supply voltage or ground according to the capacitor control signal.

[0007] Optionally, the second ends of a first number of the capacitor-controlled switches in the capacitor-controlled switches are connected to a power supply voltage, and the second ends of a second number of the capacitor-controlled switches are connected to ground, so that the equivalent capacitance of the variable capacitor module offsets the parasitic capacitance of the capacitor to be detected, and the total number of the capacitor-controlled switches is equal to the sum of the first number and the second number.

[0008] Optionally, the integration module includes at least one integration capacitor, and the control module includes an amplifier; one end of the integration capacitor is connected to a first input terminal of the amplifier, and the other end is connected to an output terminal of the amplifier, and a second input terminal of the amplifier is grounded; the amplifier is used to convert the integrated charge on the integration capacitor into a detection voltage corresponding to the capacitance value of the capacitor to be detected.

[0009] Optionally, the control module further includes a controller, an input end of the controller is connected to an output end of the amplifier, and the controller is used to calculate the capacitance value of the capacitor to be detected according to the detection voltage.

[0010] Optionally, the capacitance detection circuit further includes at least one of the following control switches: a first control switch, one end of which is connected to the first input end of the amplifier, and the other end is respectively connected to the second input end of the amplifier and the ground, and is used to close according to a switch control signal during the sampling phase of capacitance detection to clear the charge on the integral capacitor; a second control switch, one end of which is connected to the first input end of the amplifier, and the other end is connected to the output end of the capacitor to be detected, and is used to be disconnected according to the switch control signal during the sampling phase of capacitance detection to prevent charge transfer, and closed during the integration phase of capacitance detection to provide a charge transfer path; a third control switch, one end of which is connected to one end of the capacitor to be detected, and the other end is connected to the power supply voltage, and the other end of the capacitor to be detected is grounded; and is used to be closed according to the switch control signal during the sampling phase of capacitance detection, and disconnected during the integration phase of capacitance detection to realize charge sampling of the capacitor to be detected; a fourth control switch, one end of which is connected to the output end of the amplifier, and the other end is grounded, and is used to be closed according to the switch control signal during the sampling phase of capacitance detection to control the value of the detection voltage to be a preset voltage value.

[0011] Optionally, the variable capacitor module further includes at least one on-off control switch, and at least one of the switch capacitors is connected to the control input terminal of the control module via the corresponding on-off control switch; the on-off state of the on-off control switch is controlled by an on-off control signal.

[0012] Optionally, the variable capacitance module is a variable capacitance matrix, the variable capacitance matrix includes a plurality of parallel switched capacitors and corresponding capacitance control switches, one end of each switched capacitor is connected to the control input end, and the other end is connected to a power supply voltage or ground through the corresponding capacitance control switch according to the capacitance control signal, and the equivalent capacitance of the variable capacitance matrix satisfies the following formula:

[0013]

[0014] Among them, the C off is the equivalent capacitance of the variable capacitance matrix, the C p is the parasitic capacitance of the capacitor to be detected, C is the switch capacitance, N is the number of switch capacitances, a i is the capacitance control signal.

[0015] Optionally, the feedback coefficient of the amplifier satisfies the following formula:

[0016]

[0017] Wherein, β is the feedback coefficient of the amplifier, C fb is the integrating capacitor, the C x is the capacitance to be detected, the C p is the parasitic capacitance of the capacitor to be detected, C is the switch capacitor, and N is the number of the switch capacitors.

[0018] Optionally, the feedback coefficient of the amplifier varies within a range of:

[0019]

[0020] Among them, the C fb is the integrating capacitor, C is the switching capacitor, N is the number of switching capacitors, and β is the feedback coefficient of the amplifier.

[0021] A capacitance detection method comprises: providing a capacitance detection circuit, the capacitance detection circuit at least comprising: a variable capacitance module, the variable capacitance module comprising at least one switch capacitor, one end of the switch capacitor being connected to the input end of the capacitance detection circuit, and the other end being connected to a power supply voltage or a ground according to a capacitance control signal; in a sampling phase of capacitance detection, connecting a capacitance to be detected to a power supply voltage for charge sampling, and controlling a first number of switch capacitors to be connected to the power supply voltage and a second number of switch capacitors to be grounded according to a capacitance control signal, wherein the number of switch capacitors is greater than or equal to the sum of the first number and the second number; in an integration phase of capacitance detection, transferring the charge collected by the capacitance to be detected to the capacitance detection circuit, and controlling the switch capacitor connected to the power supply voltage in the sampling phase to be grounded according to the capacitance control signal, and the switch capacitor connected to the ground in the sampling phase to be connected to the power supply voltage; converting the integrated charge on the capacitance detection circuit into a detection voltage, and calculating the capacitance value of the capacitance to be detected according to the detection voltage.

[0022] Optionally, the detection method also includes: during the sampling stage, adjusting the value of the capacitor control signal to a preset control value to offset the parasitic capacitance of the capacitor to be detected, and the preset control value is the value corresponding to the capacitor control signal when the detection voltage value is a preset voltage value.

[0023] Optionally, the capacitance detection circuit also includes at least one on-off control switch, and the switch capacitor is connected to the input end of the capacitance detection circuit through the corresponding on-off control switch; the capacitance detection circuit also includes: controlling the on-off control switch to close according to an on-off control signal to connect the corresponding switch capacitor to the capacitance detection circuit.

[0024] Optionally, the feedback coefficient of the capacitance detection circuit varies within a range of:

[0025]

[0026] Among them, the C fb is the integrating capacitor, C is the switching capacitor, N is the number of switching capacitors, and β is the feedback coefficient of the capacitance detection circuit.

[0027] An electronic device comprises the capacitance detection circuit.

[0028] The capacitance detection circuit of the present invention increases a variable capacitance module, wherein the variable capacitance module includes at least one switching capacitor, wherein one end of the switching capacitor is connected to a control input end of a control module, and the other end is connected to a power supply voltage or a ground according to a capacitance control signal. Since the feedback coefficient of the capacitance detection circuit is inversely proportional to the capacitance in the circuit, the capacitance value in the capacitance detection circuit can be increased by increasing the variable capacitance module, thereby reducing the feedback coefficient of the capacitance detection circuit and improving the stability of the circuit.

[0029] Furthermore, by controlling the switch through capacitance, the switch capacitance is controlled according to the capacitance control signal to be connected to the capacitance detection circuit, thereby further reducing the feedback coefficient of the capacitance detection circuit.

[0030] Furthermore, the second ends of the first number of capacitor control switches are connected to the power supply voltage, and the second ends of the second number of capacitor control switches are connected to the ground, so that the equivalent capacitance of the variable capacitance module offsets the parasitic capacitance of the capacitor to be detected, thereby improving the detection accuracy of the capacitance detection circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] 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.

[0032] Figure 1 is a structural schematic diagram of a capacitance detection circuit according to an embodiment;

[0033] Figure 2 is a circuit diagram of a variable capacitance module according to an embodiment;

[0034] Figure 3 for Figure 1 The equivalent circuit diagram of the capacitance detection circuit in the AC working state;

[0035] Figure 4 It is a structural schematic diagram of a capacitance detection circuit according to an embodiment of the present invention;

[0036] Figure 5 is a circuit diagram of a variable capacitor module according to an embodiment of the present invention;

[0037] Figure 6 It is a structural schematic diagram of a capacitance detection circuit according to an embodiment of the present invention;

[0038] Figure 7 is a circuit diagram of a variable capacitor module according to an embodiment of the present invention;

[0039] Figure 8FIG. 4 is a flow chart of a capacitance detection method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0040] 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.

[0041] Please see Figure 1 , a schematic diagram of the structure of a capacitance detection circuit of an embodiment.

[0042] Among them, C x is the external input capacitance to be detected, C p The capacitance C to be detected x Intrinsic parasitic capacitance, including parasitic capacitance on the line, C fb is the integral capacitance, which is also the range of capacitance detection, C off It is a variable capacitor array used to offset the parasitic capacitance C p . Parasitic capacitance C p and the capacitance to be detected C x The capacitor detection circuit is connected to the power supply voltage VCC through the switch m3, and the capacitor to be detected C x The output terminal is connected to the variable capacitor array C off One end of the variable capacitor array C is connected to the first input end of the amplifier. off The other end is connected to the power supply voltage VCC or ground through the connection switch m5, the second input end of the amplifier is grounded, and is connected to the first input end of the amplifier through the switch m1. The integral capacitor C fb The two ends of the amplifier are connected between the first input terminal and the output terminal of the amplifier. The output terminal of the amplifier is grounded through the switch m4. The detection voltage V o With the capacitor C to be detected x Correspondingly, the first input terminal of the amplifier is the negative input terminal of the amplifier, and the second input terminal of the amplifier is the positive input terminal of the amplifier.

[0043] Figure 1 The detection principle of the capacitance detection circuit in the capacitor detection is:

[0044] In the sampling phase, switches m1, m3, and m4 are closed, switch m2 is open, and switch m5 is connected to the power supply voltage VCC. off The lower plate of the capacitor is connected to VCC. fb , C x , Cp and C off The charge on the capacitor C fb The charge on is 0):

[0045] Q 1 =VCC·(C x +C p )-VCC·C off

[0046] In the integration phase, switch m2 is closed, switches m1, m3, and m4 are open, switch m5 is grounded, and the variable capacitor array C off The lower plate is connected to the ground, and the capacitor C fb , C x , C p and C off The charge on the capacitor C x With C off The charge on both sides is 0) is:

[0047] Q 2 =-Vo·C fb

[0048] According to the law of conservation of charge, Q1=Q2, and the output voltage Vo in the second stage can be obtained as:

[0049]

[0050] It can be concluded that the capacitance to be detected C x The capacitance value is:

[0051]

[0052] Please see Figure 2 , a schematic structural diagram of a variable capacitor module according to an embodiment.

[0053] The variable capacitance module includes a variable capacitance matrix C off Among them, s 0 、s 1 、s 2 、s 3 ...s N-3 、s N-2 and N-1 is the on-off control switch, C is the switch capacitor, and the on-off control switch s 0 、s 1 、s 2 、s 3 ...s N-3 、s N-2 and N-1One end is connected to the negative input of the amplifier, and the other end is connected to one end of the switch capacitor C. The other end of the switch capacitor C is connected to the power supply voltage VCC or ground through the switch m5, and is closed or opened by the capacitor control signal. 0 、s 1 、s 2 、s 3 ...s N-3 、s N-2 and N-1 The on-off control signal Code is used to control the closing so as to connect the corresponding switch capacitor C to the capacitance detection circuit. The on-off control signal Code is a set of multi-bit code words, and each bit corresponds to an on-off control switch.

[0054] Please see Figure 3 ,for Figure 1 Equivalent circuit diagram of the capacitance detection circuit in the AC working state.

[0055] In AC working state, the amplifier and the integral capacitor C fb A closed-loop system is formed. The feedback coefficient of the amplifier is the feedback coefficient of the capacitance detection circuit. The feedback coefficient β of the capacitance detection circuit satisfies the following formula:

[0056]

[0057] In a closed-loop system, the larger the feedback coefficient, the more unstable the corresponding system is, especially when the capacitor C to be detected is x With parasitic capacitance C p The problem is particularly acute in smaller cases.

[0058] Depend on Figure 2 It can be seen that in the on-off control switch s 0 、s 1 、s 2 、s 3 ...s N-3 、s N-2 and N-1 When disconnected, the corresponding switch capacitor C is not connected to the circuit. p The size of the capacitor C varies greatly in different applications (from a few picofarads to hundreds of picofarads). x The variation range will not exceed the integral capacitance C fb .so Figure 1 The feedback coefficient β of the capacitance detection circuit in the range of variation is:

[0059]

[0060] When the parasitic capacitance C p When it is very big (Cp >>C fb ), the feedback coefficient β is close to 0, but the parasitic capacitance C p When I was very young (C p < <C fb ), the feedback coefficient is close to 1, and the feedback coefficient varies approximately between 0 and 1. For the amplifier, the closer the feedback coefficient is to 1, the worse the stability of the feedback system. So for the parasitic capacitance C p When the capacitance is too small, the feedback system of the capacitance detection circuit will have stability problems. In addition, the feedback coefficient varies widely, which will cause different input capacitances C to be detected. x and parasitic capacitance C p There are large differences in the performance of capacitance detection circuits under different conditions.

[0061] In view of the above problems, the present application further improves the above capacitance detection circuit.

[0062] Please see Figure 4 , a schematic diagram of the structure of a capacitance detection circuit according to an embodiment of the present invention.

[0063] In this embodiment, the capacitance detection circuit includes a variable capacitance module 1 , an integration module 2 and a control module 3 .

[0064] The variable capacitor module 1 includes at least one switch capacitor, one end of which is connected to the control input end of the control module 3, and the other end is connected according to the capacitor control signal a. i Connected to the power supply voltage VCC or ground, the variable capacitor module 1 is used to reduce the feedback coefficient of the capacitance detection circuit. One end of the switch capacitor can be connected to the control input end of the control module 3, or it can be controlled by the on-off control switch to connect to the detection circuit. Capacitor control signal a i It can be generated by other modules of the capacitance detection circuit or provided externally.

[0065] In other optional embodiments, the variable capacitor module 1 may further include other capacitors or other circuit elements, such as a switching device, and the capacitor or the switching device may be connected in parallel or in series with the switching capacitor.

[0066] The integration module 2 is connected between the control input terminal and the control output terminal of the control module 3. The input terminal of the integration module 2 is also connected to the capacitor C to be detected. x The integration module 2 includes at least one integration capacitor. When there are multiple integration capacitors, each integration capacitor can be connected in parallel or in series.

[0067] In other optional implementations, the integration module 2 may also include an integration capacitor and other electronic components, such as a switch device.

[0068] The control module 3 is used to output a signal corresponding to the capacitance value of the capacitor to be detected according to the integrated charge on the integration module 2. The control module 3 includes a digital-to-analog converter, a digital processor, and an amplifier or a comparator, and the amplifier is preferably an amplifier.

[0069] For example, the variable capacitor module 1 includes a variable capacitor array, the integration module 2 includes at least one integration capacitor, and the control module 3 includes an amplifier.

[0070] Please see Figure 5 , a circuit diagram of a variable capacitor module according to an embodiment of the present invention.

[0071] Figure 5 In the example, the variable capacitor module includes N switch capacitors C, 2 1 C. 2 2 C. 2 3 C...2 N-3 C. 2 N-2 C and 2 N-1 C, and the corresponding capacitor control switch b 0 、b 1 、b 2 、b 3 ...b N-3 、b N-2 and b N-1 . Switching capacitor C, 2 1 C. 2 2 C. 2 3 C...2 N-3 C. 2 N-2 C and 2 N-1 One end of C is connected to the control input end of the control module, and the other end is connected to the corresponding capacitor control switch b 0 、b 1 、b 2 、b 3 ...b N-3 、b N-2 and b N-1 The first end of the capacitor is connected to the switch b 0 、b 1 、b 2 、b 3 ...b N-3 、b N-2 and b N-1 The second end of the capacitor controls the signal a 0 、a 1 、a 2 、a 3 ...a N-3 、a N-2 and a N-1 Connect the power supply voltage VCC or ground, due to the switch capacitor 21 C. 2 2 C. 2 3 C...2 N-3 C. 2 N-2 C and 2 N-1 C is connected to the power supply voltage VCC or ground, that is, the switching capacitor 2 1 C. 2 2 C. 2 3 C...2 N-3 C. 2 N-2 C and 2 N-1 C are all connected to the capacitance detection circuit. By connecting all the switch capacitors C to the capacitance detection circuit, the feedback coefficient of the capacitance detection circuit can be reduced and the stability of the circuit can be improved.

[0072] Please see Figure 6 , a schematic diagram of the structure of a capacitance detection circuit according to an embodiment of the present invention.

[0073] The capacitance detection circuit of this embodiment further includes a first control switch K1, a second control switch K2, a third control switch K3 and a fourth control switch K4. The control module 3 includes an amplifier 31 and a controller 32. The variable capacitance module includes a variable capacitance array C off Each control switch can be implemented by using electronic components with switching characteristics such as switching transistors, diodes, triodes, etc.

[0074] Variable capacitor array C off The specific circuit implementation is as follows Figure 5 As shown. Variable capacitor array C off One end is connected to the first input end of the amplifier 31, and the other end is connected to the first input end of the amplifier 31 according to the capacitance control signal a i Control capacitor control switch b i Connect to power supply voltage VCC or ground.

[0075] Integral capacitor C fb One end of the amplifier 31 is connected to the first input end of the amplifier 31, and the other end is connected to the output end of the amplifier 31. The second input end of the amplifier 31 is grounded, and the output end of the amplifier 31 is connected to the controller 32. The amplifier 31 is used to connect the integral capacitor C fb The charge on the capacitor C is converted into a detection voltage V0, and the controller 32 is used to calculate the capacitance C to be detected according to the detection voltage V0. x Capacitance value.

[0076] One end of the first control switch K1 is connected to the first input end of the amplifier 31, and the other end is connected to the second input end of the amplifier 31 and the ground respectively, and is used to close in the sampling phase according to the switch control signal to increase the integration capacitor C fbIn an optional implementation, the second input terminal of the amplifier 31 may be connected to a fixed reference voltage, and the first control switch K1 may be omitted.

[0077] One end of the second control switch K2 is connected to the first input end of the amplifier 31, and the other end is connected to the capacitor C to be detected. x The first end of the second control switch K2 is connected to the first end of the second control switch K3, and is used to be disconnected in the sampling phase according to the switch control signal, and closed in the integration phase to provide a charge transfer path. In an optional embodiment, the capacitor to be detected can be connected to the capacitor detection circuit by a manual or automatic connection device, and the second control switch K2 can be omitted.

[0078] One end of the third control switch K3 is connected to the capacitor C to be detected x One end of the capacitor is connected to the power supply voltage VCC, and the other end is connected to the power supply voltage VCC. x The other end of the third control switch K3 is used to close in the sampling phase according to the switch control signal and to open in the integration phase to realize the capacitance C to be detected. x In an optional embodiment, the charging of the capacitor to be detected can be achieved by a manual or automatic connection device, and the third control switch K3 can be omitted.

[0079] One end of the fourth control switch K4 is connected to the output end of the amplifier 31, and the other end is grounded, and is used to close according to the switch control signal during the sampling phase to control the value of the detection voltage V0 to be a preset voltage value. The preset voltage value is 0 or other values. In an optional embodiment, the value of the detection voltage V0 can be other fixed voltage values, and the fourth control switch K4 can be omitted.

[0080] Capacitor to be tested C x The inherent parasitic capacitance C p The two ends of the capacitor C x The parasitic capacitance C p Includes parasitic capacitance in the signal path.

[0081] Figure 6 The specific detection process of the capacitance detection circuit includes the sampling stage and the integration stage. The sampling stage is to charge the capacitor to be detected to the power supply voltage to realize charge sampling. The integration stage is to transfer all the charges on the capacitor to be detected to the integration capacitor. According to the principle of charge conservation, the output voltage of the amplifier after the charge transfer can be obtained. By obtaining the output voltage, the capacitance of the capacitor to be detected can be calculated. The specific process is as follows:

[0082] In the sampling stage of capacitance detection, the first control switch K1, the third control switch K3 and the fourth control switch K4 are closed according to the switch control signal, and the second control switch K2 is opened. i Control capacitor control switch b i The second end of the capacitor is connected to the power supply voltage VCC. i At this time, since the second control switch K2 is disconnected and the third control switch K3 is closed, the capacitor C to be measured x and parasitic capacitance C p Since the first control switch K1 is closed, the first input terminal of the amplifier 31 is grounded, and the second terminal of the capacitance control switch is connected to the power supply voltage, the variable capacitance matrix C off As the fourth control switch K4 is closed, the integral capacitor C fb Both ends of the capacitor are grounded, so the integral capacitor C fb The charge on the capacitor is 0. Therefore, the capacitor C x , parasitic capacitance C p , variable capacitor array C off and the integrating capacitor C fb The charge superposition sum on is:

[0083]

[0084] Among them, Q 1 is the charge superposition sum of the capacitor to be detected, the parasitic capacitance of the capacitor to be detected and the switch capacitor, VCC is the power supply voltage, C x is the capacitance to be detected, C p is the parasitic capacitance of the capacitor to be detected, a i is the capacitance control signal, C is the switch capacitance, and N is the number of switch capacitances. i When the value is 1, the corresponding capacitor controls the switch b i Connect the power supply voltage VCC, the corresponding switch capacitor C starts to charge, and there is charge on it. i When the value is 0, the corresponding capacitor controls the switch b i When connected to ground, the corresponding switch capacitor C is not charged and has no charge.

[0085] In the integration phase of capacitance detection, the first control switch K1, the third control switch K3 and the fourth control switch K4 are disconnected according to the switch control signal, and the second control switch K2 is closed, and the value of the capacitance control signal is taken as the preset control value minus 1, so that in the sampling phase, the capacitance control switch b i The second end, which was originally connected to the power supply voltage, is now connected to the ground. During the sampling phase, the capacitor controls the switch b. iThe second end originally connected to the ground is connected to the power supply voltage. In other optional implementations, the value of the capacitor control signal can also be taken as the inverse of the preset control value or a fixed value, so that in the sampling stage, the capacitor control switch b i The second end, which was originally connected to the power supply voltage, is now connected to the ground. During the sampling phase, the capacitor controls the switch b. i The second end, which was originally connected to the ground, is connected to the power supply voltage.

[0086] At this time, since the second control switch K2 is closed and the third control switch K3 is open, the capacitor C x and parasitic capacitance C p The charge on the capacitor begins to transfer to the capacitor detection circuit. Since the first control switch K1 is turned off, the integral capacitor C fb Start charging, the variable capacitor matrix C off The second end of the capacitor control switch is connected to the power supply voltage and the switch capacitor starts to charge. fb The charge on the capacitor C begins to be converted into the detection voltage V0 output by the amplifier 31. At the end of the integration phase, the capacitor C x and parasitic capacitance C p All the charges on the capacitor are transferred to the capacitor detection circuit, and the charge on it is 0. At this time, the integral capacitor C fb and variable capacitor array C off The charge superposition sum on is:

[0087]

[0088] Among them, Q 2 is the charge superposition sum of the integral capacitor and the switch capacitor, Vo is the detection voltage output by the amplifier, C fb is the integral capacitor, VCC is the power supply voltage, a i is the capacitance control signal, C is the switch capacitance, and N is the number of the switch capacitances.

[0089] According to the law of conservation of charge, Q1 = Q2. From the above formulas (1) and (2), we can get the detection voltage Vo output by the amplifier in the integration stage of capacitance detection as:

[0090]

[0091] Among them, V o is the detection voltage output by the amplifier, a i is the capacitance control signal, C is the switch capacitance, N is the number of switch capacitances, C fb is the integrating capacitor, C x is the capacitance to be detected, C pare the parasitic capacitance of the capacitor to be detected and the VCC power supply voltage.

[0092] Also because,

[0093]

[0094] Therefore, the equivalent capacitance value of the variable capacitor array can be obtained:

[0095]

[0096] Let d i =2a i -1 (6)

[0097] Among them, the value of di is ±1, so the above formula (5) can be transformed into:

[0098]

[0099] Therefore, the variable capacitor array C off It can be seen as the result of the superposition of positive and negative capacitances. When ai=0 (ie di=-1), the corresponding capacitance is a negative capacitance; when ai=1 (ie di=1), the corresponding capacitance is a positive capacitance, thus generating a signed capacitance.

[0100] Figure 6 In the example, the variable capacitor array C off The capacitance control signal a i The value is 0 or 1. When it is 1, the corresponding capacitor controls the switch b i The second end of the capacitor is connected to the power supply voltage VCC. When it is 0, the capacitor controls the switch b i The second end of the capacitor is connected to the ground, that is, regardless of the capacitance control signal a i , including a 0 、a 1 、a 2 、a 3 ...a N-3 、a N-2 and a N-1 The value is 0 or 1, all switch capacitors C, 2 1 C. 2 2 C. 2 3 C...2 N-3 C. 2 N-2 C and 2 N-1 C are all connected to the capacitance detection circuit. off The second end of the capacitance control switch corresponding to all the switch capacitors in is either connected to the power supply voltage or to the ground, so that all the switch capacitors are connected to the capacitance detection circuit. Therefore, for the AC signal, the variable capacitance array C off The capacitance value is fixed, that is

[0101] C off =(2 N -1)·C (8)

[0102] The feedback factor of the amplifier needs to satisfy the following formula:

[0103]

[0104] where β is the feedback factor of the β amplifier.

[0105] From formulas (8) and (9), it can be concluded that the feedback coefficient β of the amplifier is:

[0106]

[0107] Since, in the capacitance detection circuit (2 N -1) C is much larger than the integral capacitor C fb Therefore, it can be deduced from formula (10) that the feedback coefficient β of the amplifier is much smaller than 1, which reduces the feedback coefficient value of the capacitance detection circuit and improves the stability of the capacitance detection circuit.

[0108] The variation range of the amplifier's feedback coefficient β satisfies the following formula:

[0109]

[0110] It can be seen from formula (11) that the change in the amplifier's feedback coefficient β is only the amount of change in the measured capacitance C x and parasitic capacitance C p , since the equivalent capacitance value of the variable capacitor array (2 N -1) C is much larger than the integral capacitor C fb The feedback coefficient β of the amplifier is much smaller than 1. x The variation range is large, and the variation range of the amplifier feedback coefficient β is also small. Therefore, the capacitance detection circuit will not be affected by the capacitance C to be measured. x and parasitic capacitance C p The value is small and there will be no stability problems, nor will the measured capacitance C x and parasitic capacitance C p The larger the variation range, the greater the difference, which improves the consistency of the performance of the capacitance detection circuit.

[0111] In an optional embodiment, the variable capacitance module 1 can also adjust the capacitance control signal a 0 、a 1 、a 2 、a 3 ...a N-3 、a N-2 and aN-1 The value of is used to control the equivalent capacitance of the variable capacitance module 1, and the equivalent capacitance can offset the parasitic capacitance of the external capacitor to be detected.

[0112] Optionally, before performing capacitance detection, the value of the capacitance control signal is adjusted to a preset control value, which is a value corresponding to the capacitance control signal when the second control switch is disconnected and the detection voltage value output by the amplifier is a preset voltage value. The preset voltage value is 0.

[0113] Specifically, the second control switch K2 is first turned off to control the capacitor C to be tested. x Without connecting to the capacitance detection circuit, the control capacitance control signal a is converted into 0 、a 1 、a 2 、a 3 ...a N-3 、a N-2 and a N-1 The highest bit a N-1 Set to 1, the remaining bits are a 0 、a 1 、a 2 、a 3 ...a N-3 、a N-2 are all set to 0. i When the value of is 1, the corresponding capacitor control switch is connected to the power supply voltage, and the corresponding switch capacitor starts to charge. i When the value of is 0, the corresponding capacitor control switch is connected to the ground, and the corresponding switch capacitor is not charged, so the capacitor control signal a i It can be realized that during the sampling stage, part or all of the switch capacitors in the variable capacitor array are grounded. After the charge transfer cycle, it is determined whether the detection voltage value output by the amplifier 31 is close to 0. If not, the control capacitor control signal a is adjusted in turn. 0 、a 1 、a 2 、a 3 ...a N-3 、a N-2 Middle high a N-2 The value of is cycled in sequence until a set of values ​​is found that can make the detection voltage value output by the amplifier 31 close to 0. This set of values ​​is the preset control value of the capacitance control signal. Under the preset control value, the equivalent capacitance value of the variable capacitance array is equal to the capacitance to be detected C x The parasitic capacitance C p The values ​​of are close to equal, that is

[0114]

[0115] Among them, a iThe value is 0 or 1, a 1 to a i The set of values ​​formed is the preset control value.

[0116] From the above formulas (1) and (12), it can be concluded that after the sampling phase, the charge flowing into the capacitance detection circuit is actually:

[0117] Q 1 =VCC·C x (13)

[0118] It can be seen that by adjusting the preset value of the capacitance control signal, the variable capacitance array C off The equivalent capacitance value generated is the same as the capacitance to be detected C x The inherent parasitic capacitance C p equal to the value of the parasitic capacitance C p , eliminate the parasitic capacitance C p The influence of the capacitance detection circuit can be improved to improve the accuracy of the output results.

[0119] The value of the capacitor control signal is taken as the reverse of the preset control value. At this time, the integral capacitor C fb and variable capacitor array C off The charge superposition sum on is:

[0120]

[0121] Among them, a` i Inverts the preset control value.

[0122] According to the law of conservation of charge, Q1 = Q2, and we can get the capacitance C to be detected. x for:

[0123]

[0124] Since the detection voltage Vo can be obtained through detection, the integral capacitor C fb , power supply voltage VCC, a` i The value is the inverse of the preset control value, and the switch capacitance C is a known quantity, so the capacitance to be detected C can be obtained x The value of .

[0125] The capacitance detection circuit of this embodiment uses a variable capacitance array to offset the capacitance C to be detected. x The parasitic capacitance C p Including parasitic capacitance on the signal path can improve the accuracy of the detection results.

[0126] In an optional embodiment, the variable capacitance module further includes at least one on-off control switch, and part of the switch capacitors are connected to the control input terminal of the control module through the corresponding on-off control switch.

[0127] Please see Figure 7 , a circuit diagram of a variable capacitor module according to an embodiment of the present invention.

[0128] In this embodiment, the variable capacitor module also includes an on-off control switch s N-3 、s N-2 and N-1 , the on-off control switch s N-3 、s N-2 and N-1 One end is connected to the first input end of the amplifier, and the other end is connected to the corresponding switch capacitor 2 N-3 C. 2 N-2 C and 2 N-1 C is connected to one end, the switch capacitor 2 N-3 C. 2 N-2 C and 2 N-1 The other end of C is connected to the first end of the corresponding capacitor control switch, and the on-off control switch s N-3 、s N-2 and N-1 It is used to control the corresponding switch capacitor access circuit according to the on-off control signal. In other optional embodiments, the number of on-off control switches can be equal to the number of switch capacitors. For example, the variable capacitor module includes on-off control switches s 0 to N-1 , the on-off control switch s 0 to N-1 One end is connected to the first input end of the amplifier, and the other end is connected to the corresponding switch capacitor C, 2 1 C. 2 2 C. 2 3 C...2 N-3 C. 2 N-2 C and 2 N-1 C is connected to one end, the C, 2 1 C. 2 2 C. 2 3 C...2 N-3 C. 2 N-2 C and 2 N-1 The other end of C is connected to the corresponding capacitor control switch b 0 、b 1 、b 2 、b 3 ...b N-3 、b N-2 and b N-1 The first end of the on-off control switch s0 to N-1 Used to control the corresponding switch capacitor access circuit according to the on-off control signal. By adding an on-off control switch, the mixed use of signed capacitors and unsigned capacitors can be achieved. For example, an unsigned capacitor is realized by using a switch capacitor connected to the on-off control switch, and an unsigned capacitor is realized by a switch capacitor not connected to the on-off control switch, so as to increase the application scenarios of the capacitor detection circuit and facilitate the control of the equivalent capacitance value of the variable capacitor module.

[0129] An embodiment of the present invention further provides a capacitance detection method.

[0130] Please see Figure 8 , is a flow chart of a capacitance detection method according to an embodiment of the present invention.

[0131] The capacitance detection method of this embodiment includes the following steps:

[0132] Step S1, providing a capacitance detection circuit, the capacitance detection circuit at least includes: a variable capacitance module, the variable capacitance module includes at least one switch capacitor, one end of the switch capacitor is connected to the input end of the capacitance detection circuit, and the other end is connected to the power supply voltage or ground according to the capacitance control signal. For example, the specific implementation of the variable capacitance module is as follows Figure 2 , Figure 5 or Figure 7 shown.

[0133] Step S2: During the sampling phase of capacitance detection, the capacitance to be detected is connected to the power supply voltage for charge sampling, and a first number of the switching capacitors are controlled to be connected to the power supply voltage and a second number of the switching capacitors are controlled to be grounded according to a capacitance control signal, and the number of the switching capacitors is greater than or equal to the sum of the first number and the second number.

[0134] In the sampling stage of capacitance detection, the capacitor to be detected is connected to the power supply voltage to realize charge sampling. Specifically, the switch can be used to control one end of the capacitor to be detected to connect to the power supply voltage and the other end to ground. The first number of switch capacitors connected to the power supply voltage will also perform charge sampling. At this time, the sampled charge amount Q1 is,

[0135]

[0136] Among them, Q 1 is the amount of charge collected, C x is the capacitance to be detected, C p is the parasitic capacitance of the capacitor to be detected, a i is the capacitance control signal, C is the switch capacitance, and N is the number of switch capacitances. i When the value is 1, the corresponding capacitor controls the switch b iConnect the power supply voltage VCC, the corresponding switch capacitor C starts to charge and perform charge sampling. i When the value is 0, the corresponding capacitor controls the switch b i The corresponding switch capacitor C is not charged, and charge sampling is not performed, and there is no charge on it. The first quantity is a i The value of 1 corresponds to the number of switch capacitors, and the second number is a i The value of 0 corresponds to the number of switched capacitors.

[0137] The capacitance control signal can be provided by an external circuit or generated by an additional circuit module. The first number can be greater than the second number or less than the second number. The first number and the second number can be 0 or the total number of the switching capacitors.

[0138] S3. In the integration phase of capacitance detection, the charge collected by the capacitance to be detected is transferred to the capacitance detection circuit, and the switch capacitor connected to the power supply voltage in the sampling phase is controlled to be grounded according to the capacitance control signal, and the switch capacitor grounded in the sampling phase is connected to the power supply voltage.

[0139] Specifically, in the integration stage of capacitance detection, the capacitor to be detected is disconnected from the power supply voltage and its output end is connected to the input end of the capacitance detection circuit to realize the transfer of the charge on the capacitor to be detected to the capacitance detection circuit. At this time, the switch capacitor originally connected to the power supply voltage is grounded, and the switch capacitor originally grounded is connected to the power supply voltage. For example, by inverting the capacitance control signal and taking it as the original value minus 1 or other fixed value, the switch capacitor originally connected to the power supply voltage is grounded, and the switch capacitor originally grounded is connected to the power supply voltage.

[0140] S4. Convert the integrated charge on the capacitance detection circuit into a detection voltage, and calculate the capacitance value of the capacitor to be detected according to the detection voltage.

[0141] Specifically, an integral capacitor and an amplifier can be used to convert the integrated charge on the capacitance detection circuit into a detection voltage, and an analog-to-digital converter plus a processor, or a digital signal processor, or other processors with calculation functions can be used to calculate the capacitance value of the capacitor to be detected based on the detection voltage. In other optional embodiments, a mapping table of charge amount-capacitance value can also be pre-stored, and the capacitance value of the capacitor to be detected can be obtained by looking up the mapping table.

[0142] Specifically, after the integration stage is completed, the charge on the capacitor to be detected and the parasitic capacitor is 0, and the charge after the charge integration is completed is:

[0143]

[0144] Among them, Q2 is the charge amount after charge integration is completed, Vo is the detection voltage, C fb is the integrating capacitor, a` i is the capacitance control signal a i The value is negated, C is the switch capacitor, and N is the number of the switch capacitors.

[0145] According to the law of conservation of charge, Q1 = Q2, and we can get the capacitance C to be detected. x for:

[0146]

[0147] It can be seen that according to the capacitance detection method of this embodiment, the capacitance to be detected C can be calculated. x Capacitance value.

[0148] Since the feedback coefficient of the capacitance detection circuit is related to the capacitance to be detected C x The capacitance value is inversely proportional to the capacitance value of the capacitor to be tested. x The variation range is large in different application scenarios. x When the value is small, or the parasitic capacitance C p When the value is small, the feedback coefficient of the amplifier is large, which leads to poor stability of the capacitance detection circuit, and further leads to a large variation range of the feedback coefficient of the amplifier, resulting in different capacitances C to be detected. x There are large differences in the capacitance detection performance.

[0149] The feedback coefficient formula of the capacitance detection circuit is:

[0150]

[0151] It can be seen that by adding a variable capacitor module to the capacitor detection circuit, the switch capacitor in the variable capacitor module is connected to the capacitor detection circuit by connecting the power supply voltage or the ground. The equivalent capacitance of the variable capacitor module will reduce the feedback coefficient of the capacitor detection circuit, thereby improving the stability of the capacitor detection circuit.

[0152] When the number of the switch capacitors is greater than the sum of the first number and the second number, the variable capacitor module can use Figure 2 or Figure 7 In the circuit structure, when using Figure 2 When the variable capacitor module circuit is in the embodiment, the first number of switch capacitors are connected to the power supply voltage and the second number of switch capacitors are connected to the ground according to the on-off control signal. The specific implementation process is similar to the above and will not be repeated here.

[0153] When using Figure 7When the variable capacitor module circuit is in the circuit, the first number of switch capacitors are connected to the power supply voltage according to the capacitor control signal, the second number of switch capacitors are connected to the ground, and the remaining switch capacitors are connected to the circuit through the on-off control switch according to the on-off control signal. The specific implementation process is similar to the above and will not be repeated here.

[0154] When the number of the switch capacitors is equal to the sum of the first number and the second number, that is, all the switch capacitors are connected to the capacitance detection circuit, at this time, the circuit of the variable capacitance module is as follows: Figure 5 As shown, the specific implementation process is similar to the above. At this time, the feedback coefficient β of the capacitance detection circuit is:

[0155]

[0156] Since, in the capacitance detection circuit (2 N -1) C is much larger than the integral capacitor C fb Therefore, it can be deduced that the feedback coefficient β of the amplifier is much smaller than 1, which reduces the feedback coefficient value of the capacitance detection circuit and improves the stability of the capacitance detection circuit.

[0157] The variation range of the amplifier's feedback coefficient β satisfies the following formula:

[0158]

[0159] It can be seen that the change in the feedback coefficient β of the capacitance detection circuit is only the capacitance to be measured C x and parasitic capacitance C p , since the equivalent capacitance value of the variable capacitor array (2 N -1) C is much larger than the integral capacitor C fb The feedback coefficient β of the amplifier is much smaller than 1. x The variation range is large, and the variation range of the amplifier feedback coefficient β is also small. Therefore, the capacitance detection circuit will not be affected by the capacitance C to be measured. x and parasitic capacitance C p The value is small and there will be no stability problems, nor will the measured capacitance C x and parasitic capacitance C p The larger the variation range, the greater the difference, which improves the consistency of the performance of the capacitance detection circuit.

[0160] In an optional embodiment, the detection method also includes: during the sampling stage, adjusting the value of the capacitor control signal to a preset control value to offset the parasitic capacitance of the capacitor to be detected, and the preset control value is the value corresponding to the capacitor control signal when the detection voltage value is a preset voltage value.

[0161] For example, the preset voltage value is 0. Control the capacitor C to be tested x When the capacitance detection circuit is not connected, the control capacitance control signal a is converted into 0 、a 1 、a 2 、a 3 ...a N-3 、a N-2 and a N-1 The highest bit a N-1 Set to 1, the remaining bits are a 0 、a 1 、a 2 、a 3 ...a N-3 、a N-2 are all set to 0. i When the value of is 1, the corresponding switch capacitor starts to charge. i When the value of is 0, the corresponding switch capacitor is not charged, so the capacitor control signal a i It can be achieved that during the sampling phase, part or all of the switch capacitors in the variable capacitor module are grounded. After the charge transfer cycle, it is determined whether the detection voltage value is close to 0. If not, the control capacitor control signal a is adjusted in turn. 0 、a 1 、a 2 、a 3 ...a N-3 、a N-2 Middle high a N-2 The value is cycled in sequence until a set of values ​​is found that can make the detection voltage value close to 0. This set of values ​​is the preset control value of the capacitance control signal. Under the preset control value, the equivalent capacitance value of the variable capacitance module is equal to the capacitance to be detected C x The parasitic capacitance C p The values ​​of are close to equal, that is

[0162]

[0163] Among them, a i The value is 0 or 1, a 1 to a i The set of values ​​formed is the preset control value.

[0164] Therefore, after the sampling phase, the charge flowing into the capacitor detection circuit is actually:

[0165] Q 1 =VCC·C x

[0166] It can be seen that by adjusting the preset value of the capacitance control signal, the variable capacitance array C off The equivalent capacitance value generated is the same as the capacitance to be detected Cx The inherent parasitic capacitance C p equal to the value of the parasitic capacitance C p .

[0167] The value of the capacitor control signal is taken as the reverse of the preset control value. At this time, the integral capacitor C fb and variable capacitor array C off The charge superposition sum on is:

[0168]

[0169] Among them, a` i Inverts the preset control value.

[0170] According to the law of conservation of charge, Q1 = Q2, and we can get the capacitance C to be detected. x for:

[0171]

[0172] Since the detection voltage Vo can be obtained through detection, the integral capacitor C fb , power supply voltage VCC, a` i The value is the inverse of the preset control value, and the switch capacitance C is a known quantity, so the capacitance to be detected C can be obtained x The value of .

[0173] The capacitance detection method of this embodiment is to offset the capacitance C to be detected. x The parasitic capacitance C p Including parasitic capacitance on the signal path can improve the accuracy of the detection results.

[0174] In an optional embodiment, the capacitance detection circuit further includes at least one on-off control switch, and the switch capacitor is connected to the input end of the capacitance detection circuit through the corresponding on-off control switch. The number of on-off control switches is a third number, and the range of the third number is greater than or equal to 0 and less than or equal to the number of all switch capacitors.

[0175] The capacitance detection method further includes: controlling the on-off control switch to close according to the on-off control signal to connect the corresponding switch capacitor to the capacitance detection circuit, and controlling the on-off control switch to open according to the on-off control signal to prevent the corresponding switch capacitor from connecting to the capacitance detection circuit. The connection relationship of the on-off control switch in the capacitance detection circuit is as follows: Figure 7 shown.

[0176] In an optional embodiment, the capacitance detection method further includes: controlling the on-off control switch to be closed or opened according to the on-off control signal to adjust the value of the capacitance control signal to a preset control value. For example, the on-off control signal is used to control part of the switch capacitors not to be connected to the capacitance detection circuit, and then the value of the capacitance control signal is adjusted to the preset control value according to the above method to improve the convenience of control.

[0177] An embodiment of the present invention further provides an electronic device including the above capacitance detection circuit, such as a capacitive sensor, a detector, etc. The electronic device adopts the above capacitance detection circuit, which reduces the feedback coefficient of the electronic device and improves the stability of the electronic device.

[0178] The above descriptions are merely embodiments of the present application and are not intended to limit the patent scope of the present application. Any equivalent structural or equivalent process transformations 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 capacitance detection circuit, characterized in that: include: Control module, variable capacitance module and integration module; The control module comprises a control input terminal and a control output terminal, wherein the control input terminal is connected to the input terminal of the integration module, and the control output terminal is connected to the output terminal of the integration module, and is used to output a signal corresponding to the capacitance value of the capacitor to be detected according to the integrated charge on the integration module; The variable capacitance module includes N switch capacitors C, 2 1 C. 2 2 C. 2 3 C...2 N-3 C. 2 N-2 C and 2 N-1 C, and the corresponding capacitor control switches b0, b1, b2, b3...b N-3 、b N-2 and b N-1 , switch capacitor C, 2 1 C. 2 2 C. 2 3 C...2 N-3 C. 2 N-2 C and 2 N-1 One end of C is connected to the control input end of the control module, and the other end is connected to the corresponding capacitor control switch b0, b1, b2, b3...b N-3 、b N-2 and b N-1 The first end of the capacitor is connected to the capacitor control switch b0, b1, b2, b3...b N-3 、b N-2 and b N-1 The second end of the capacitor controls the signals a0, a1, a2, a3, ... a N-3 、a N-2 and a N-1 Connect to the power supply voltage or ground; for AC signals, the capacitance value C of the variable capacitor module off is a fixed value, that is: C off =(2 N -1)·C; The input end of the integration module is also connected to the output end of the capacitor to be detected, so as to realize the charge integration on the plate of the capacitor to be detected; The integration module includes at least one integration capacitor, and the control module includes an amplifier; one end of the integration capacitor is connected to a first input end of the amplifier, and the other end is connected to an output end of the amplifier, and a second input end of the amplifier is grounded; the amplifier is used to convert the integrated charge on the integration capacitor into a detection voltage corresponding to the capacitance value of the capacitor to be detected; The feedback coefficient β of the amplifier is: C fb is the integrating capacitor, C x is the capacitance to be detected, C p is the parasitic capacitance of the capacitor to be detected, (2 N -1) C is much larger than the integral capacitor C fb , so the feedback coefficient β of the amplifier is much smaller than 1.

2. The capacitance detection circuit according to claim 1, characterized in that: The second ends of the first number of the capacitance control switches in the capacitance control switches are connected to the power supply voltage, and the second ends of the second number of the capacitance control switches are connected to the ground, so that the equivalent capacitance of the variable capacitance module offsets the parasitic capacitance of the capacitance to be detected in the sampling stage, and the total number of the capacitance control switches is equal to the sum of the first number and the second number.

3. The capacitance detection circuit according to claim 1, characterized in that: The control module further includes a controller, an input end of the controller is connected to an output end of the amplifier, and the controller is used to calculate the capacitance value of the capacitor to be detected according to the detection voltage.

4. The capacitance detection circuit according to claim 1, characterized in that: Also includes at least one of the following control switches: a first control switch, one end of which is connected to the first input end of the amplifier, and the other end of which is respectively connected to the second input end of the amplifier and the ground, and is used for closing in a sampling phase of capacitance detection according to a switch control signal to clear the charge on the integration capacitor; a second control switch, one end of which is connected to the first input end of the amplifier, and the other end of which is connected to the output end of the capacitor to be detected, and is used to be disconnected in a sampling phase of capacitance detection to prevent charge transfer according to a switch control signal, and closed in an integration phase of capacitance detection to provide a charge transfer path; A third control switch, one end of the third control switch is connected to one end of the capacitor to be detected, the other end is connected to the power supply voltage, and the other end of the capacitor to be detected is grounded; and is used to close in the sampling phase of the capacitance detection according to the switch control signal, and to open in the integration phase of the capacitance detection to realize the charge sampling of the capacitor to be detected; A fourth control switch, one end of which is connected to the output end of the amplifier and the other end of which is grounded, is used to close in the sampling phase of capacitance detection according to a switch control signal to control the value of the detection voltage to be a preset voltage value.

5. The capacitance detection circuit according to claim 1, characterized in that: The variable capacitor module also includes at least one on-off control switch, and at least one switch capacitor is connected to the control input end of the control module through the corresponding on-off control switch; the on-off state of the on-off control switch is controlled by an on-off control signal.

6. The capacitance detection circuit according to claim 1, characterized in that: The feedback coefficient of the amplifier varies within the range of: Among them, the C fb is the integrating capacitor, C is the switching capacitor, N is the number of switching capacitors, and β is the feedback coefficient of the amplifier.

7. A capacitance detection method, characterized in that: include: Provide a capacitance detection circuit according to any one of claims 1 to 6; In the sampling phase of capacitance detection, the capacitor to be detected is connected to the power supply voltage for charge sampling, and a first number of the switch capacitors are controlled to be connected to the power supply voltage and a second number of the switch capacitors are controlled to be grounded according to the capacitance control signal, and the number of the switch capacitors is greater than or equal to the sum of the first number and the second number; In the integration phase of capacitance detection, the charge collected by the capacitance to be detected is transferred to the capacitance detection circuit, and the switch capacitor connected to the power supply voltage in the sampling phase is controlled to be grounded according to the capacitance control signal, and the switch capacitor grounded in the sampling phase is connected to the power supply voltage; The integrated charge on the capacitance detection circuit is converted into a detection voltage, and the capacitance value of the capacitor to be detected is calculated according to the detection voltage.

8. The capacitance detection method according to claim 7, characterized in that: The detection method further comprises: During the sampling phase, the value of the capacitance control signal is adjusted to a preset control value to offset the parasitic capacitance of the capacitor to be detected, and the preset control value is the value corresponding to the capacitance control signal when the detection voltage value is a preset voltage value.

9. The capacitance detection method according to claim 8, characterized in that: The capacitance detection circuit further includes at least one on-off control switch, and the switch capacitor is connected to the input end of the capacitance detection circuit through the corresponding on-off control switch; The capacitance detection circuit further includes: controlling the on-off control switch to be turned on or off according to an on-off control signal.

10. The capacitance detection method according to any one of claims 7 to 9, characterized in that: The variation range of the feedback coefficient of the capacitance detection circuit is: Among them, the C fb is the integrating capacitor, C is the switching capacitor, N is the number of switching capacitors, and β is the feedback coefficient of the capacitance detection circuit.

11. An electronic device, characterized in that: The capacitance detection circuit comprises the capacitance detection circuit described in any one of claims 1 to 6.

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