Inductive Capacitance Compensation Circuit and Compensation Method

Abstract

The present invention discloses a capacitive induction compensation circuit and a compensation method. The compensation circuit includes: a first switch, a compensation unit, and a compensation control unit. When the first switch is closed, charge is provided to the capacitive induction through a reference voltage; the compensation unit is connected to both ends of the compensation capacitor. The compensation control unit includes a clamping circuit, a third switch, and a fourth switch. The third switch and the fourth switch are used to connect the compensation capacitor to the capacitive induction. After the charges of the compensation capacitor and the capacitive induction are stabilized during each connection, the clamping circuit controls the voltages at both ends of the compensation capacitor to be equal. According to the capacitive induction compensation circuit of the present invention, the capacitive induction is compensated by the compensation capacitor. After the compensation capacitor is connected to the capacitive induction and the charges of the compensation capacitor and the capacitive induction are stabilized, the clamping circuit controls the voltages at both ends of the compensation capacitor to be equal, so as to ensure that the charges of each compensation of the capacitive induction by the compensation capacitor are the same, thereby enabling the size of the capacitive induction to change linearly under compensation.

Description

Technical Field

[0001] The present invention relates to the field of integrated circuits, and particularly to a capacitive induction compensation circuit and a compensation method. Background Art

[0002] In a capacitive induction identification system without touch, there is a parasitic capacitance. After touch occurs, due to the existence of the parasitic capacitance, the induced capacitance will deviate from the actual value and change. In order to reduce the influence of the parasitic capacitance on the induced capacitance, a compensation capacitance is required for compensation. In order to save area, its value is much smaller than the parasitic capacitance. Therefore, it is necessary to perform multiple compensations to compensate the parasitic capacitance to an acceptable range. However, after each compensation, the voltage on the induced capacitance will change, which will affect the amount of charge compensated by the compensation capacitance each time, and then affect the change amount of the induced capacitance, thus generating non-linearity.

[0003] The information disclosed in this background art section is only intended to enhance the overall understanding of the present invention and should not be regarded as an admission or any form of suggestion that this information constitutes prior art already known to those of ordinary skill in the art. Summary of the Invention

[0004] An object of the present invention is to provide a capacitive induction compensation circuit and a compensation method, which can make the amount of charge compensated for the induced capacitance the same each time.

[0005] To achieve the above object, an embodiment of the present invention provides a capacitive induction compensation circuit, including: a first switch, a compensation unit, and a compensation control unit.

[0006] The first switch is connected between a reference voltage and an induced capacitance. When the first switch is in a closed state, charge is provided to the induced capacitance through the reference voltage.

[0007] The compensation unit is connected between the first switch and the induced capacitance, and the compensation unit includes a compensation capacitance.

[0008] The compensation control unit is connected to both ends of the compensation capacitance. The compensation control unit includes a clamping circuit, a third switch, and a fourth switch. The third switch and the fourth switch are used to connect the compensation capacitance to the induced capacitance. After the charge of the compensation capacitance and the induced capacitance is stable in each connection, the clamping circuit controls the voltages at both ends of the compensation capacitance to be equal.

[0009] In one or more embodiments of the present invention, the clamping circuit includes a first operational amplifier having a first input terminal, a second input terminal, and a first output terminal. The first end of the third switch is connected to the first input terminal of the first operational amplifier and the first end of the sensing capacitor. The second end of the third switch is connected to the first end of the compensation capacitor. The first end of the fourth switch is connected to the second input terminal and the first output terminal of the first operational amplifier. The second end of the fourth switch is connected to the second end of the compensation capacitor.

[0010] In one or more embodiments of the present invention, the compensation unit further includes a fifth switch and a sixth switch. The first end of the fifth switch is connected to the reference voltage. The second end of the fifth switch is connected to the second end of the compensation capacitor. The first end of the sixth switch is connected to the reference voltage. The second end of the sixth switch is connected to the first end of the compensation capacitor.

[0011] In one or more embodiments of the present invention, during one working cycle of the sensing capacitor compensation circuit, the first switch is controlled by a first pulse signal. The first pulse signal flips from a first level to a second level, and the first switch changes from an open state to a closed state. The first pulse signal flips from the second level to the first level, and the first switch changes from the closed state to the open state.

[0012] After the first switch changes from the closed state to the open state, the fifth switch and the sixth switch are controlled by a second pulse signal. The fifth switch and the sixth switch act synchronously under the control of the second pulse signal. The second pulse signal flips multiple times between the first level and the second level. When the second pulse signal flips from the first level to the second level, the fifth switch and the sixth switch change from the open state to the closed state. When the second pulse signal flips from the second level to the first level, the fifth switch and the sixth switch change from the closed state to the open state.

[0013] The third switch and the fourth switch are controlled by a third pulse signal. The third switch and the fourth switch act synchronously under the control of the third pulse signal. While the second pulse signal flips multiple times between the first level and the second level, the third pulse signal flips multiple times between the second level and the first level. When the third pulse signal flips from the first level to the second level, the third switch and the fourth switch change from the open state to the closed state. When the third pulse signal flips from the second level to the first level, the third switch and the fourth switch change from the closed state to the open state, so that when the third switch and the fourth switch are in the closed state, the fifth switch and the sixth switch are in the open state.

[0014] In one or more embodiments of the present invention, an operating cycle of the inductive capacitance compensation circuit includes an inductive capacitance charging period and an inductive capacitance compensation period. During the inductive capacitance charging period, the first switch is controlled to be in a closed state;

[0015] During the inductive capacitance compensation period, the first switch is kept in an open state. The compensation unit completes multiple compensations to the inductive capacitance during the inductive capacitance compensation period. During one compensation process, the fifth switch and the sixth switch are controlled to be closed to charge the compensation capacitance, and the third switch and the fourth switch are controlled to be closed while the fifth switch and the sixth switch are kept in an open state to achieve charge compensation for the inductive capacitance.

[0016] In one or more embodiments of the present invention, the charge compensated to the inductive capacitance by the compensation capacitance each time is:

[0017] Q Cc =(VREF - VCM)*Cc

[0018] After each compensation of the compensation capacitance, the voltage change on the inductive capacitance is:

[0019]

[0020] After N compensations of the compensation capacitance, the voltage on the inductive capacitance is:

[0021] V Cs =VREF - N*ΔV Cs =VREF - N*(VREF - VCM)*Cc / Cs

[0022] Wherein, Cc is the capacitance value of the compensation capacitance, VREF is the reference voltage, VCM is the reference voltage, and Cs is the capacitance value of the inductive capacitance.

[0023] In one or more embodiments of the present invention, the inductive capacitance compensation circuit further includes a second switch and a measurement unit. The first end of the second switch is connected to the common end of the first switch and the inductive capacitance, and the second end of the second switch is connected to the measurement unit. An operating cycle of the inductive capacitance compensation circuit further includes an inductive capacitance measurement period. During the inductive capacitance measurement period, the second switch is controlled to be closed to transfer the charge of the compensated inductive capacitance to the measurement unit, and after the charge transfer is completed, the second switch is controlled to be opened so that the measurement unit measures the capacitance value of the inductive capacitance.

[0024] In one or more embodiments of the present invention, the inductive capacitance compensation circuit further includes a second switch and a measurement unit. The first end of the second switch is connected to the common end of the first switch and the inductive capacitance. The second end of the second switch is connected to the measurement unit. The second switch is controlled by a fourth pulse signal. After the second pulse signal and the third pulse signal stop flipping, the fourth pulse signal flips from a first level to a second level, and the second switch changes from an open state to a closed state. The fourth pulse signal flips from the second level to the first level, and the second switch changes from the closed state to the open state. When the second switch is in the open state, the measurement unit is used to measure the magnitude of the inductive capacitance.

[0025] In one or more embodiments of the present invention, the measurement unit includes a second operational amplifier, a feedback capacitor, a reset switch, an eighth switch, and a constant current source;

[0026] The second operational amplifier has a third input terminal, a fourth input terminal, and a second output terminal. The feedback capacitor is connected between the third input terminal and the second output terminal of the second operational amplifier. The reset switch is connected between the third input terminal and the second output terminal of the second operational amplifier. The second end of the second switch is connected to the third input terminal of the second operational amplifier. The first end of the second switch is connected to the common end of the first switch and the inductive capacitance. The fourth input terminal of the second operational amplifier is connected to a reference voltage. The first end of the eighth switch is connected to the third input terminal of the second operational amplifier. The second end of the eighth switch is connected to the first end of the constant current source. The second end of the constant current source is grounded. When the eighth switch is in the closed state, the feedback capacitor is discharged through the constant current source.

[0027] In one or more embodiments of the present invention, after the second switch is turned off, the on / off state of the eighth switch is controlled to realize the discharge of the feedback capacitor by the constant current source.

[0028] In one or more embodiments of the present invention, the measurement unit further includes a counting unit. The counting unit is used to count the number of discharges of the constant current source. The counting unit includes a comparator and a D flip-flop. The comparator has a fifth input terminal, a sixth input terminal, and a third output terminal. The fifth input terminal of the comparator is connected to the second output terminal of the second operational amplifier. The sixth input terminal of the comparator is connected to the reference voltage. The output terminal of the comparator is connected to the D input terminal of the D flip-flop.

[0029] The present invention also discloses an inductive capacitance compensation method, including the following steps:

[0030] S1. Connect the reference voltage to the inductive capacitance to supply charge to the inductive capacitance by using the reference voltage;

[0031] S2. Disconnect the connection between the reference voltage and the sensing capacitor, control the compensation capacitor to compensate the sensing capacitor with charge multiple times, and control the voltages at both ends of the compensation capacitor to be equal after each compensation of the compensation capacitor, so as to ensure that the charge compensated by the compensation capacitor each time is the same.

[0032] In one or more embodiments of the present invention, it further includes: measuring the magnitude of the compensated sensing capacitor.

[0033] Compared with the prior art, according to the sensing capacitor compensation circuit and compensation method of the embodiments of the present invention, the sensing capacitor is compensated by the compensation capacitor, and after the compensation capacitor and the sensing capacitor are connected and the charges of the compensation capacitor and the sensing capacitor are stable, the clamping circuit is used to control the voltages at both ends of the compensation capacitor to be equal, so as to ensure that the charge compensated by the compensation capacitor to the sensing capacitor each time is the same, so that the magnitude of the sensing capacitor changes linearly under compensation. Description of the Drawings

[0034] Figure 1 is the circuit schematic diagram of a sensing capacitor compensation circuit according to an embodiment of the present invention.

[0035] Figure 2 is the working timing diagram of each switch in a sensing capacitor compensation circuit according to an embodiment of the present invention.

[0036] Figure 3 is the flowchart of a sensing capacitor compensation method according to an embodiment of the present invention. Detailed Embodiments

[0037] The following will combine the drawings to describe the specific embodiments of the present invention in detail, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0038] Unless otherwise clearly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "having" etc. will be understood to include the stated elements or components, without excluding other elements or other components.

[0039] Embodiment 1

[0040] As Figure 1 shown, a sensing capacitor compensation circuit includes: a first switch K1, a compensation unit 10, a compensation control unit 20, a second switch K2, and a measurement unit 30.

[0041] Among them, the first end of the first switch K1 is connected to the reference voltage VREF, the second end of the first switch K1 is connected to the first end of the sensing capacitor Cs, and the second end of the sensing capacitor Cs is grounded. When the first switch K1 is in the closed state, the reference voltage VREF provides charge for the sensing capacitor Cs.

[0042] The compensation unit 10 is connected to the common terminal of the sensing capacitor Cs and the first switch K1. This common terminal is the second terminal of the first switch K1 or the first terminal of the sensing capacitor Cs. Charge is compensated for the sensing capacitor Cs through the compensation unit 10.

[0043] The compensation control unit 20 is connected to the compensation unit 10. The compensation control unit 20 is used to ensure that the charge compensated for the sensing capacitor Cs by the compensation unit 10 is the same each time.

[0044] The first terminal of the second switch K2 is connected to the common terminal of the first switch K1 and the sensing capacitor Cs. The second terminal of the second switch K2 is connected to the measuring unit 30. That is, the measuring unit 30 is connected to the compensation unit 10 and the sensing capacitor Cs through the second switch K2. The magnitude of the sensing capacitor Cs is measured through the measuring unit 30.

[0045] As Figure 1 shown, the compensation unit 10 includes a compensation capacitor Cc, a fifth switch K5, and a sixth switch K6. The first terminal of the fifth switch K5 is connected to the reference voltage VREF. The second terminal of the fifth switch K5 is connected to the second terminal of the compensation capacitor Cc. The first terminal of the sixth switch K6 is connected to the reference voltage VCM. The second terminal of the sixth switch K6 is connected to the first terminal of the compensation capacitor Cc. The compensation capacitor Cc is charged through the voltage difference between the reference voltage VREF and the reference voltage VCM.

[0046] As Figure 1 shown, the compensation control unit 20 is connected to both ends of the compensation capacitor Cc. The compensation control unit 20 includes a clamping circuit, a third switch K3, and a fourth switch K4. The third switch K3 and the fourth switch K4 are used to connect the compensation capacitor Cc to the sensing capacitor Cs. After the charge of the compensation capacitor Cc and the sensing capacitor Cs stabilizes during each connection, the clamping circuit controls the voltages at both ends of the compensation capacitor Cc to be equal.

[0047] Specifically, the clamping circuit includes a first operational amplifier AMP1. The first operational amplifier AMP1 has a first input terminal, a second input terminal, and a first output terminal. The second input terminal and the first output terminal are short-circuited. Among them, the first input terminal is the positive input terminal, and the second input terminal is the negative input terminal. In other embodiments, the first input terminal can also be the negative input terminal, and the second input terminal can also be the positive input terminal.

[0048] The first terminal of the third switch K3 is connected to the first input terminal of the first operational amplifier AMP1 and the first terminal of the sensing capacitor Cs. The second terminal of the third switch K3 is connected to the first terminal of the compensation capacitor Cc and the second terminal of the sixth switch K6. The first terminal of the fourth switch K4 is connected to the second input terminal and the first output terminal of the first operational amplifier AMP1. The second terminal of the fourth switch K4 is connected to the second terminal of the compensation capacitor Cc.

[0049] As shown Figure 1 in the figure, the compensation unit 10 further includes a seventh switch K7. The first end of the seventh switch K7 is connected to the common end of the first switch K1 and the induction capacitor Cs, and the second end of the seventh switch K7 is connected to the first end of the third switch K3 and the first input end of the first operational amplifier AMP1. The connection between the compensation unit 10, the compensation control unit 20 and the induction capacitor Cs is achieved by closing the seventh switch K7. When the compensation capacitor Cc needs to compensate the induction capacitor Cs for charge, the seventh switch K7 is in the closed state.

[0050] As shown Figure 1 in the figure, the measurement unit 30 includes a second operational amplifier AMP2, a feedback capacitor Cint, a reset switch Krset, an eighth switch K8, and a constant current source A1. The measurement unit 30 is connected to the compensation unit 10 and the induction capacitor Cs through the second switch K2, and is used to measure the magnitude of the induction capacitor Cs.

[0051] Specifically, the second operational amplifier AMP2 has a third input end, a fourth input end, and a second output end. The third input end is the negative input end, and the fourth input end is the positive input end. In other embodiments, the third input end is the positive input end, and the fourth input end is the negative input end.

[0052] The feedback capacitor Cint is connected between the third input end and the second output end of the second operational amplifier AMP2, and the reset switch Krset is connected between the third input end and the second output end of the second operational amplifier AMP2. The second end of the second switch K2 is connected to the third input end of the second operational amplifier AMP2, and the first end of the second switch K2 is connected to the common end of the first switch K1 and the induction capacitor Cs. The connection between the measurement unit 30 and the induction capacitor Cs is achieved by closing the second switch K2. The fourth input end of the second operational amplifier AMP2 is connected to the reference voltage VCM.

[0053] The first end of the eighth switch K8 is connected to the third input end of the second operational amplifier AMP2, the second end of the eighth switch K8 is connected to the first end of the constant current source A1, the second end of the constant current source A1 is grounded, and the current direction of the constant current source A1 is flowing to the ground. When the eighth switch is in the closed state, the feedback capacitor Cint is discharged through the constant current source A1.

[0054] As shown Figure 1 in the figure, the measurement unit 30 further includes a counting unit 31, and the counting unit 31 is used to count the number of discharges of the constant current source A1.

[0055] Specifically, the counting unit 31 includes a comparator COMP and a D flip-flop M. The comparator COMP has a fifth input terminal, a sixth input terminal, and a third output terminal. The fifth input terminal is the negative input terminal, and the sixth input terminal is the positive input terminal. In other embodiments, the fifth input terminal is the positive input terminal, and the sixth input terminal is the negative input terminal. The fifth input terminal of the comparator COMP is connected to the second output terminal of the second operational amplifier AMP2. The sixth input terminal of the comparator COMP is connected to the reference voltage VCM. The output terminal of the comparator COMP is connected to the D input terminal of the D flip-flop M. The comparator COMP converts the quantified number of discharge times into a digital signal and performs counting through the D flip-flop M.

[0056] Combined with Figure 2 and Figure 1 to illustrate the working principle of this embodiment. Figure 2 is the timing diagram of the operation of the first switch K1, the second switch K2, the third switch K3, the fourth switch K4, the fifth switch K5, the sixth switch K6, and the eighth switch K8.

[0057] Specifically, in one working cycle of the inductive capacitance compensation circuit, the first switch K1 is controlled to open and close by the first pulse signal. When the first pulse signal flips from the first level to the second level, the first switch K1 switches from the off state to the on state. When the first pulse signal flips from the second level to the first level, the first switch switches from the on state to the off state. That is, the first switch K1 closes once when the first pulse signal jumps from the first level to the second level and then from the second level to the first level, so as to charge the inductive capacitance Cs with the reference voltage VREF.

[0058] When the first pulse signal jumps from the second level to the first level, that is, the first switch K1 switches from the on state to the off state. The fifth switch K5 and the sixth switch K6 are controlled by the second pulse signal. At this time, the fifth switch K5 and the sixth switch K6 act synchronously under the control of the second pulse signal. The second pulse signal flips multiple times between the first level and the second level. When the second pulse signal flips from the first level to the second level, the fifth switch K5 and the sixth switch K6 switch from the off state to the on state. When the second pulse signal flips from the second level to the first level, the fifth switch K5 and the sixth switch K6 switch from the on state to the off state. That is, in the subsequent continuous jumping process of the second pulse signal between the second level and the first level, the fifth switch K5 and the sixth switch K6 repeat the alternating actions of closing and opening.

[0059] The third switch K3 and the fourth switch K4 are controlled by a third pulse signal, and the third switch K3 and the fourth switch K4 act synchronously under the control of the third pulse signal. While the second pulse signal flips multiple times between the first level and the second level, the third pulse signal also flips multiple times between the first level and the second level. When the third pulse signal flips from the first level to the second level, the third switch K3 and the fourth switch K4 switch from the off state to the on state. When the third pulse signal flips from the second level to the first level, the third switch K3 and the fourth switch K4 switch from the on state to the off state.

[0060] In this embodiment, when the third switch K3 and the fourth switch K4 are in the on state, the fifth switch K5 and the sixth switch K6 are in the off state. When the fifth switch K5 and the sixth switch K6 are in the on state, the third switch K3 and the fourth switch K4 are in the off state. The third switch K3, the fourth switch K4, the fifth switch K5, and the sixth switch K6 can be in the off state simultaneously.

[0061] Furthermore, when the second pulse signal jumps from the first second level to the first level, the third pulse signal jumps from the first level to the second level. At this time, the third switch K3 and the fourth switch K4 start to act. The third switch K3 and the fourth switch K4 switch from the off state to the on state, and also repeat the alternate on and off actions during the subsequent continuous jumps of the third pulse signal between the second level and the first level. It can be seen that the third switch K3 and the fourth switch K4 act out of phase with respect to the fifth switch K5 and the sixth switch K6, that is, when the fifth switch K5 and the sixth switch K6 switch from on to off, the third switch K3 and the fourth switch K4 switch from off to on.

[0062] When the fifth switch K5 and the sixth switch K6 are on and the third switch K3 and the fourth switch K4 are off, the compensation capacitor Cc is charged by the reference voltage VREF and the reference voltage VCM. When the third switch K3 and the fourth switch K4 are on and the fifth switch K5 and the sixth switch K6 are off, the compensation capacitor Cc compensates the charge of the sensing capacitor Cs. By setting the first operational amplifier AMP1, the voltages at both ends of the compensation capacitor Cc are made equal, so that each time the third switch K3 and the fourth switch K4 are on and the compensation capacitor Cc compensates the charge of the sensing capacitor Cs, the compensated charges are equal. Only when the amount of charge compensated each time is the same and the number of compensations is a fixed value can the change in the amount of charge caused by the change in the sensing capacitor Cs be accurately quantified, preventing the remaining charge from changing due to different amounts of charge compensated each time, which affects the magnitude of the change in the sensing capacitor Cs and causes non-linearity.

[0063] In this embodiment, the charge compensated by the compensation capacitor Cc to the sensing capacitor Cs each time is:

[0064] Q Cc = (VREF - VCM) * Cc

[0065] After each compensation of the compensation capacitor Cc, the voltage change on the induction capacitor Cs is:

[0066]

[0067] After N compensations of the compensation capacitor Cc, the voltage on the induction capacitor Cs is:

[0068] V Cs = VREF - N * ΔV Cs = VREF - N * (VREF - VCM) * Cc / Cs

[0069] Where Cc is the capacitance of the compensation capacitor, VREF is the reference voltage, VCM is the reference voltage, and Cs is the capacitance of the induction capacitor.

[0070] When the first switch K1 operates, the noise voltage of the reference voltage VREF on the induction capacitor Cs is: Vn REF(K1)

[0071] When the fifth switch K5 and the sixth switch K6 operate, the noise charge of the reference voltage VREF on the compensation capacitor Cc is: Qn REF(Cc) = Vn REF(K5、K6) * Cc

[0072] When the third switch K3 and the fourth switch K4 operate, the noise voltage generated by the noise charge on the compensation capacitor Cc on the induction capacitor Cs is: Vn1 = Qn REF(Cc) / Cs

[0073] After N compensations of the compensation capacitor Cc, the total noise voltage on the induction capacitor Cs is:

[0074]

[0075] The noise voltage of the first operational amplifier AMP1 is: Vn AMP1 , and the noise charge it generates on the compensation capacitor Cc is:

[0076] Qn AMP1(Cc) = Vn AMP1 * Cc

[0077] The noise voltage generated by the noise voltage of the first operational amplifier AMP1 on the induction capacitor Cs is:

[0078]

[0079] After the N - th compensation of the compensation capacitor Cc, the noise voltage generated by the noise voltage of the first operational amplifier AMP1 on the induction capacitor Cs is as follows:

[0080]

[0081] In this embodiment, after the compensation capacitor Cc finishes compensating the charge of the induction capacitor Cs, the second pulse signal and the third pulse signal stop flipping, that is, when the third switch K3, the fourth switch K4, the fifth switch K5, and the sixth switch K6 all change from the closed state to the open state, the fourth pulse signal is used to control the second switch K2. The fourth pulse signal flips between the first level and the second level. When the fourth pulse signal flips from the first level to the second level, the second switch K2 changes from the open state to the closed state. When the fourth pulse signal flips from the second level to the first level, the second switch K2 changes from the closed state to the open state. When the second switch K2 changes from the closed state to the open state, the measurement unit 30 is used to measure the magnitude of the induction capacitor Cs.

[0082] In this embodiment, when the fourth pulse signal jumps from the first level to the second level, the second switch K2 closes. At this time, the charge on the induction capacitor Cs is transferred to the feedback capacitor Cint. When the fourth pulse signal jumps from the second level to the first level, the second switch K2 opens. At this time, by controlling the on - off of the eighth switch, the constant - current source A1 discharges the feedback capacitor Cint.

[0083] The fifth pulse signal is used to control the eighth switch K8, and the eighth switch K8 operates under the control of the fifth pulse signal. The fifth pulse signal flips between the first level and the second level multiple times. When the fifth pulse signal flips from the first level to the second level, the eighth switch K8 changes from the open state to the closed state. When the fifth pulse signal flips from the second level to the first level, the eighth switch K8 changes from the closed state to the open state. In this embodiment, the fifth pulse signal continuously flips between the first level and the second level, and the eighth switch K8 repeats the alternating actions of closing and opening. Each time the eighth switch K8 closes, the constant - current source A1 discharges the feedback capacitor Cint once until the charge on the feedback capacitor Cint is completely discharged. The counting unit 31 counts the number of discharges of the constant - current source A1, and the magnitude of the induction capacitor Cs can be determined from the obtained number of times.

[0084] As Figure 3 shown, this embodiment also discloses an induction capacitor compensation method, including the following steps:

[0085] S1. Connect the reference voltage to the induction capacitor to supply charge to the induction capacitor using the reference voltage;

[0086] S2. Disconnect the connection between the reference voltage and the sensing capacitor, control the compensation capacitor to compensate the sensing capacitor with charge multiple times, and control the voltages at both ends of the compensation capacitor to be equal after each compensation of the compensation capacitor, so as to ensure that the charge compensated by the compensation capacitor each time is the same.

[0087] The sensing capacitor compensation method further includes measuring the size of the compensated sensing capacitor.

[0088] Embodiment 2

[0089] Combined with Figure 1 As shown, one working cycle of the sensing capacitor compensation circuit includes a sensing capacitor charging period, a sensing capacitor compensation period, and a sensing capacitor measurement period.

[0090] In the sensing capacitor charging period, control the first switch K1 to be in the closed state, and charge the sensing capacitor Cs through the reference voltage VREF.

[0091] In the sensing capacitor compensation period, keep the first switch in the open state, and the compensation unit 10 completes multiple compensations to the sensing capacitor Cs during the sensing capacitor compensation period. During one compensation process, control the fifth switch K5 and the sixth switch K6 to be closed to charge the compensation capacitor Cc through the voltage difference between the reference voltage VREF and the reference voltage VCM. After the charging is completed, control the third switch K3, the fourth switch K4, and the seventh switch K7 to be closed and keep the fifth switch K5 and the sixth switch K6 in the open state to realize the charge compensation of the sensing capacitor Cs through the compensation capacitor Cc.

[0092] In the sensing capacitor measurement period, control the second switch K2 to be closed, and disconnect between the compensation capacitor Cc and the sensing capacitor Cs, so as to transfer the charge of the compensated sensing capacitor Cs to the measurement unit 30. After the charge transfer is completed, control the second switch K2 to be opened, so that the measurement unit 30 measures the size of the sensing capacitor Cs.

[0093] Further, in the sensing capacitor measurement period, after completing the transfer of the charge of the sensing capacitor Cs to the feedback capacitor Cint, control the second switch K2 to be opened. At this time, control the on-off of the eighth switch K8 to realize the discharge of the feedback capacitor Cint by the constant current source A1. The counting unit 31 counts the number of discharges of the constant current source A1, and the size of the sensing capacitor Cs can be determined through the obtained number of times.

[0094] Each switch in this embodiment adopts a control method different from the pulse signal control.

[0095] The foregoing description of the specific exemplary embodiments of the present invention is for purposes of illustration and exemplification. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many modifications and variations are possible in light of the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the invention and its practical applications, so that those skilled in the art can implement and utilize the various different exemplary embodiments of the invention, as well as various different selections and modifications. The scope of the present invention is intended to be defined by the claims and their equivalents.

Claims

1. An inductive capacitance compensation circuit, characterized in that, Comprising: A first switch connected between a reference voltage and a sensing capacitor, and when the first switch is in a closed state, providing charge to the sensing capacitor through the reference voltage; A compensation unit connected to the common terminal of the first switch and the sensing capacitor, the compensation unit comprising a compensation capacitor, a fifth switch, and a sixth switch, a first end of the fifth switch being connected to the reference voltage, a second end of the fifth switch being connected to a second end of the compensation capacitor, a first end of the sixth switch being connected to a reference voltage, and a second end of the sixth switch being connected to a first end of the compensation capacitor; And A compensation control unit connected to both ends of the compensation capacitor, the compensation control unit comprising a clamping circuit, a third switch, and a fourth switch, the third switch and the fourth switch being configured to connect the compensation capacitor to the sensing capacitor, and after the charges of the compensation capacitor and the sensing capacitor are stabilized in each connection, the clamping circuit controls the voltages at both ends of the compensation capacitor to be equal; In one operating cycle of the sensing capacitor compensation circuit, controlling the first switch using a first pulse signal, the first pulse signal flipping from a first level to a second level, the first switch transitioning from an open state to a closed state, the first pulse signal flipping from the second level to the first level, and the first switch transitioning from the closed state to the open state; After the first switch transitions from the closed state to the open state, controlling the fifth switch and the sixth switch using a second pulse signal, the fifth switch and the sixth switch operating synchronously under the control of the second pulse signal, the second pulse signal flipping multiple times between the first level and the second level, when the second pulse signal flips from the first level to the second level, the fifth switch and the sixth switch transitioning from the open state to the closed state, and when the second pulse signal flips from the second level to the first level, the fifth switch and the sixth switch transitioning from the closed state to the open state; Controlling the third switch and the fourth switch using a third pulse signal, the third switch and the fourth switch operating synchronously under the control of the third pulse signal, while the second pulse signal flips multiple times between the first level and the second level, the third pulse signal flips multiple times between the second level and the first level, when the third pulse signal flips from the first level to the second level, the third switch and the fourth switch transitioning from the open state to the closed state, and when the third pulse signal flips from the second level to the first level, the third switch and the fourth switch transitioning from the closed state to the open state, such that when the third switch and the fourth switch are in the closed state, the fifth switch and the sixth switch are in the open state.

2. The inductive capacitance compensation circuit according to claim 1, characterized in that, The clamping circuit includes a first operational amplifier having a first input terminal, a second input terminal, and a first output terminal. The first end of the third switch is connected to the first input terminal of the first operational amplifier and the first end of the sensing capacitor. The second end of the third switch is connected to the first end of the compensation capacitor. The first end of the fourth switch is connected to the second input terminal and the first output terminal of the first operational amplifier. The second end of the fourth switch is connected to the second end of the compensation capacitor.

3. The inductive capacitance compensation circuit according to claim 1, characterized in that, One operating cycle of the sensing capacitor compensation circuit includes a sensing capacitor charging period and a sensing capacitor compensation period. During the sensing capacitor charging period, the first switch is controlled to be in a closed state. During the sensing capacitor compensation period, the first switch is kept in an open state. The compensation unit completes multiple compensations to the sensing capacitor during the sensing capacitor compensation period. During one compensation process, the fifth switch and the sixth switch are controlled to be closed to charge the compensation capacitor, and the third switch and the fourth switch are controlled to be closed while the fifth switch and the sixth switch are kept in an open state to achieve charge compensation for the sensing capacitor.

4. The inductive capacitance compensation circuit according to claim 1, characterized in that, The charge compensated to the sensing capacitor by the compensation capacitor each time is: Q Cc = (VREF - VCM) * Cc After each compensation of the compensation capacitor, the voltage change on the sensing capacitor is: After N compensations of the compensation capacitor, the voltage on the sensing capacitor is: V Cs = VREF - N * ΔV Cs = VREF - N * (VREF - VCM) * Cc / Cs Where, Cc is the capacitance value of the compensation capacitor, VREF is the reference voltage, VCM is the reference voltage, and Cs is the capacitance value of the sensing capacitor.

5. The induction capacitance compensation circuit according to claim 1, wherein, The sensing capacitor compensation circuit further includes a second switch and a measurement unit. The first end of the second switch is connected to the common terminal of the first switch and the sensing capacitor. The second end of the second switch is connected to the measurement unit. One operating cycle of the sensing capacitor compensation circuit further includes a sensing capacitor measurement period. During the sensing capacitor measurement period, the second switch is controlled to be closed to transfer the charge of the compensated sensing capacitor to the measurement unit. After the charge transfer is completed, the second switch is controlled to be opened so that the measurement unit measures the capacitance value of the sensing capacitor.

6. The inductive capacitance compensation circuit according to claim 1, wherein The sensing capacitor compensation circuit further includes a second switch and a measurement unit. The first end of the second switch is connected to the common terminal of the first switch and the sensing capacitor. The second switch is controlled by a fourth pulse signal. After the second pulse signal and the third pulse signal stop toggling, the fourth pulse signal toggles from a first level to a second level, and the second switch toggles from an open state to a closed state. The fourth pulse signal toggles from the second level to the first level, and the second switch toggles from the closed state to the open state. When the second switch is in the open state, the measurement unit is used to measure the capacitance value of the sensing capacitor.

7. The inductive capacitance compensation circuit according to claim 5 or 6, characterized in that The measurement unit includes a second operational amplifier, a feedback capacitor, a reset switch, an eighth switch, and a constant current source. The second operational amplifier has a third input terminal, a fourth input terminal, and a second output terminal. The feedback capacitor is connected between the third input terminal and the second output terminal of the second operational amplifier. The reset switch is connected between the third input terminal and the second output terminal of the second operational amplifier. The second terminal of the second switch is connected to the third input terminal of the second operational amplifier, and the first terminal of the second switch is connected to the common terminal of the first switch and the sensing capacitor. The fourth input terminal of the second operational amplifier is connected to a reference voltage. The first terminal of the eighth switch is connected to the third input terminal of the second operational amplifier, and the second terminal of the eighth switch is connected to the first terminal of a constant current source. The second terminal of the constant current source is grounded. When the eighth switch is in the closed state, the feedback capacitor is discharged through the constant current source.

8. The inductive capacitance compensation circuit according to claim 7, characterized in that, After the second switch is turned off, the on / off state of the eighth switch is controlled to realize the discharge of the feedback capacitor by the constant current source.

9. The inductive capacitance compensation circuit according to claim 8, wherein The measurement unit further includes a counting unit for counting the number of discharges of the constant current source. The counting unit includes a comparator and a D flip-flop. The comparator has a fifth input terminal, a sixth input terminal, and a third output terminal. The fifth input terminal of the comparator is connected to the second output terminal of the second operational amplifier. The sixth input terminal of the comparator is connected to the reference voltage. The output terminal of the comparator is connected to the D input terminal of the D flip-flop.

10. An inductive capacitance compensation method, characterized in that, Based on the sensing capacitor compensation circuit according to any one of claims 1 to 9, the compensation method includes the following steps: S1. Connect the reference voltage to the sensing capacitor to supply charge to the sensing capacitor using the reference voltage. S2. Disconnect the reference voltage from the sensing capacitor. Control the fifth switch and the sixth switch through a second pulse signal to control the connection between the compensation capacitor and the reference voltage and the reference voltage to charge the compensation capacitor through the reference voltage and the reference voltage. Control the third switch and the fourth switch through a third pulse signal to control the connection between the compensation capacitor and the sensing capacitor to compensate the charge of the sensing capacitor through the compensation capacitor. Based on the control of the second pulse signal and the third pulse signal, charging the compensation capacitor through the reference voltage and the reference voltage and compensating the charge of the sensing capacitor through the compensation capacitor are alternated, and the voltage across the compensation capacitor is controlled to be equal at both ends after each compensation through the clamping circuit to ensure that the charge compensated by the compensation capacitor is the same each time.

11. The inductive capacitance compensation method according to claim 10, characterized in that It further includes: Measuring the magnitude of the compensated sensing capacitor.

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