CN114018298B - Capacitance-voltage conversion circuit for MEMS capacitive sensor - Google Patents

Capacitance-voltage conversion circuit for MEMS capacitive sensor Download PDF

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CN114018298B
CN114018298B CN202111234468.3A CN202111234468A CN114018298B CN 114018298 B CN114018298 B CN 114018298B CN 202111234468 A CN202111234468 A CN 202111234468A CN 114018298 B CN114018298 B CN 114018298B
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operational amplifier
node
differential operational
differential
amplifier
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CN114018298A (en
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朱樟明
商鹏鹏
钟龙杰
刘术彬
梁宇华
沈易
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Xidian University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
    • G01D5/24—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying capacitance

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Abstract

The present invention provides a capacitance-voltage conversion circuit for a MEMS capacitive sensor, comprising: the charge voltage conversion circuit comprises a voltage excitation source, a common-mode charge controller and a charge voltage conversion module; wherein, the charge-voltage conversion module includes: the active noise canceller comprises a first-stage differential amplifier, a second-stage differential amplifier, a gain error corrector, an active noise canceller and a charge feedback unit, wherein after the first-stage differential amplifier amplifies a set noise signal of a parasitic capacitor of a preset capacitive sensor, the active noise canceller connected with the first-stage differential amplifier can absorb the set noise signal, and the gain error correctors respectively connected with the active noise canceller and the second-stage differential amplifier can correct gain errors generated by the first-stage differential amplifier and the second-stage differential amplifier, so that the gain precision is improved while noise is reduced, and the energy efficiency is remarkably improved.

Description

Capacitance-voltage conversion circuit for MEMS capacitive sensor
Technical Field
The invention belongs to the technical field of MEMS capacitive sensors, and particularly relates to a capacitance-voltage conversion circuit for an MEMS capacitive sensor.
Background
MEMS (Micro Electro-Mechanical System) capacitive sensor technology is an important branch of the field of MEMS research and manufacturing, and has been rapidly developed in the fields of miniaturization, multi-functionalization, and intellectualization in recent years. The micro-capacitance type sensor is most represented by a micro-mechanical pressure gauge and an accelerometer, has the advantages of small volume, low cost, light weight, low power consumption and the like, and is widely applied to the fields of motion perception, security alarm, attitude control and the like.
Under the trend of continuous progress of semiconductor technology and continuous reduction of device size, the requirements on the precision and power consumption of an interface circuit of the MEMS capacitive sensor are higher and higher, but the noise deterioration caused by the parasitic capacitance effect is more and more significant. In a capacitance-voltage conversion circuit of the MEMS capacitive sensor in the related art, due to the existence of setting noise and operational amplifier output noise generated by parasitic capacitance, signals are deteriorated, and the requirement of signal to noise ratio cannot be met.
Disclosure of Invention
To solve the above problems in the prior art, the present invention provides a capacitance-voltage conversion circuit for a MEMS capacitive sensor. The technical problem to be solved by the invention is realized by the following technical scheme:
the present invention provides a capacitance-voltage conversion circuit for a MEMS capacitive sensor, comprising: a voltage stimulus source, a common-mode charge controller, and a charge-to-voltage conversion module, the charge-to-voltage conversion module comprising: the device comprises a first-stage differential amplifier, a second-stage differential amplifier, a gain error corrector, an active noise canceller and a charge feedback unit; wherein,
the voltage excitation source is used for exciting a preset capacitance sensor to generate a charge signal;
the common mode charge controller is used for absorbing a common mode component in the charge signal;
the first-stage differential amplifier is connected with the common-mode charge controller and is used for amplifying a set noise signal of a parasitic capacitor of a preset capacitive sensor;
the active noise canceller is connected with the first-stage differential amplifier and is used for absorbing the set noise signal amplified by the first-stage differential amplifier;
the gain error corrector is respectively connected with the active noise canceller and the second-stage differential amplifier and is used for correcting gain errors generated by the first-stage differential amplifier and the second-stage differential amplifier;
the second-stage differential amplifier is connected with the gain error corrector and is used for amplifying the corrected signal differential component;
the charge feedback unit, the first-stage differential amplifier and the second-stage differential amplifier form a closed loop, and are used for converting the differential component of the excited charge signal into a voltage signal and realizing differential signal readout.
In one embodiment of the invention, the device further comprises an output voltage signal terminal;
the first stage differential amplifier comprises a first differential operational amplifier, and the active noise canceller comprises a capacitor: cNAnd a switch:
Figure BDA0003316995130000021
the second stage differential amplifier comprises a second differential operational amplifier, and the gain error corrector comprises a capacitor: cC1And CH1And a switch:
Figure BDA0003316995130000022
and
Figure BDA0003316995130000023
the charge feedback unit comprises a capacitor CI1And a switch:
Figure BDA0003316995130000024
and
Figure BDA0003316995130000025
wherein the reverse input end of the first differential operational amplifier is connected with the common mode charge controller, the non-inverting input end is grounded, and the output end passes through CNAnd CC1The non-inverting input end of the second differential operational amplifier is connected with the non-inverting input end of the second differential operational amplifier, the inverting input end of the second differential operational amplifier is grounded, and the output end of the second differential operational amplifier is connected with the output voltage signal end; cNAnd CC1Includes a first node therebetween, the first node is connected to the second node via
Figure BDA0003316995130000031
Ground, CC1A second node is arranged between the same-phase input end of the second differential operational amplifier and the same-phase input end of the second differential operational amplifier
Figure BDA0003316995130000032
And
Figure BDA0003316995130000033
grounding;
Figure BDA0003316995130000034
and
Figure BDA0003316995130000035
includes a third node, CH1One end of the first differential operational amplifier is connected with the third node, the other end of the first differential operational amplifier is connected with the output end of the second differential operational amplifier, and the output end of the second differential operational amplifier passes through
Figure BDA0003316995130000036
And
Figure BDA0003316995130000037
grounding; a fourth node is arranged between the common mode charge controller and the inverting input end of the first differential operational amplifier, and the fourth node is connected with the inverting input end of the first differential operational amplifier
Figure BDA0003316995130000038
Is grounded and is connected with the ground,
Figure BDA0003316995130000039
and with
Figure BDA00033169951300000310
Includes a fifth node, CI1Are connected to the fourth node and the fifth node, respectively.
In one embodiment of the invention, the device further comprises a non-inverting output end and an inverting output end;
the first stage differential amplifier comprises a third differential operational amplifier, and the active noise canceller comprises a capacitor: cC21And CC22The second stage differential amplifier comprises a fourth differential operational amplifier, and the gain error corrector comprises a capacitor: cH21、CH22The C isC21The C isC22And a switch:
Figure BDA00033169951300000311
Figure BDA00033169951300000312
and
Figure BDA00033169951300000313
the charge feedback unit includes a capacitance: cI21And CI22And a switch:
Figure BDA00033169951300000314
Figure BDA00033169951300000315
and
Figure BDA00033169951300000316
wherein,
the non-inverting input end of the third differential operational amplifier is connected with the preset capacitance sensor, the inverting input end of the third differential operational amplifier is connected with the common-mode charge controller, and the first output end of the third differential operational amplifier is connected with the common-mode charge controller through a capacitor CC22The non-inverting input end and the second output end which are connected to the fourth differential operational amplifier are connected through CC21The inverting input end of the fourth differential operational amplifier is connected; cC21A sixth node is arranged between the first differential operational amplifier and the inverting input end of the fourth differential operational amplifier and is connected with the inverting input end of the fourth differential operational amplifier
Figure BDA00033169951300000317
And
Figure BDA00033169951300000318
grounding;
Figure BDA00033169951300000319
and with
Figure BDA00033169951300000320
A seventh node is included in between; cH21One end of the fourth differential operational amplifier is connected with the seventh node, the other end of the fourth differential operational amplifier is connected with the in-phase output end of the fourth differential operational amplifier, and the in-phase output end of the fourth differential operational amplifier passes through
Figure BDA00033169951300000321
And
Figure BDA00033169951300000322
grounding; an eighth node is arranged between the common mode charge controller and the inverting input end of the third differential operational amplifier and passes through
Figure BDA00033169951300000323
Is grounded and is connected with the ground,
Figure BDA00033169951300000324
and with
Figure BDA00033169951300000325
Includes a ninth node, CI21Both ends of the first node are respectively connected with the eighth node and the ninth node;
CC22a tenth node is arranged between the same-phase input end of the fourth differential operational amplifier and the same-phase input end of the fourth differential operational amplifier, and the tenth node is connected with the second differential operational amplifier
Figure BDA00033169951300000326
And
Figure BDA00033169951300000327
grounding;
Figure BDA00033169951300000328
and
Figure BDA00033169951300000329
an eleventh node therebetween; cH22One end of the fourth differential operational amplifier is connected with the eleventh node, the other end of the fourth differential operational amplifier is connected with the inverted output end of the fourth differential operational amplifier, and the inverted output end of the fourth differential operational amplifier passes through
Figure BDA0003316995130000041
And
Figure BDA0003316995130000042
grounding; the preset capacitorA twelfth node is arranged between the sensor and the non-inverting input end of the third differential operational amplifier
Figure BDA0003316995130000043
Is grounded and is connected with the ground,
Figure BDA0003316995130000044
and with
Figure BDA0003316995130000045
Including a thirteenth node, CI22Are connected with the twelfth node and the thirteenth node, respectively.
In one embodiment of the invention, the preset capacitance sensor comprises a variable capacitance: cS1And CS2And a switch:
Figure BDA0003316995130000046
and
Figure BDA0003316995130000047
wherein,
Figure BDA00033169951300000411
one end of which is connected to an excitation voltage,
Figure BDA0003316995130000048
one end of the first and second electrodes is grounded,
Figure BDA0003316995130000049
another end of (1) and
Figure BDA00033169951300000410
the other end connections of the first and second nodes are connected to a fourteenth node; cS1One end of the second differential operational amplifier is connected with the fourteenth node, and the other end of the second differential operational amplifier is connected with a positive phase input end of a third differential operational amplifier; cS2One end of the second differential amplifier is connected with the fourteenth node, and the other end of the second differential amplifier is connected with the inverting input end of the third differential amplifier.
In one embodiment of the invention, theThe common mode charge controller includes a capacitance: c01And C02And a switch:
Figure BDA00033169951300000412
and
Figure BDA00033169951300000413
wherein,
Figure BDA00033169951300000414
one end of the first and second electrodes is grounded,
Figure BDA00033169951300000415
one end of which is connected to an excitation voltage,
Figure BDA00033169951300000416
another end of (1) and
Figure BDA00033169951300000417
the other end connections of the first and second nodes are all connected to a fifteenth node; c01One end of the first differential operational amplifier is connected with the fifteenth node, and the other end of the first differential operational amplifier is connected with a positive phase input end of a third differential operational amplifier; c02One end of the second differential amplifier is connected with the fifteenth node, and the other end of the second differential amplifier is connected with the inverting input end of the third differential amplifier.
In one embodiment of the present invention, the voltage excitation source generates a step voltage with a preset amplitude to excite the preset capacitive sensor.
Compared with the prior art, the invention has the beneficial effects that:
the present invention provides a capacitance-voltage conversion circuit for a MEMS capacitive sensor, comprising: the charge voltage conversion circuit comprises a voltage excitation source, a common-mode charge controller and a charge voltage conversion module; wherein, the charge-voltage conversion module includes: the active noise canceller comprises a first-stage differential amplifier, a second-stage differential amplifier, a gain error corrector, an active noise canceller and a charge feedback unit, wherein after the first-stage differential amplifier amplifies a set noise signal of a preset capacitance sensor parasitic capacitance, the active noise canceller connected with the first-stage differential amplifier can absorb the set noise signal, and the gain error correctors respectively connected with the active noise canceller and the second-stage differential amplifier can correct gain errors generated by the first-stage differential amplifier and the second-stage differential amplifier, so that the gain accuracy is improved while the noise is reduced, and the energy efficiency is remarkably improved.
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Drawings
Fig. 1 is a block diagram showing a structure of a capacitance-voltage conversion circuit for a MEMS capacitive sensor in the related art;
fig. 2 is a circuit diagram of a charge-voltage conversion module in the related art;
FIG. 3 is a block diagram of a capacitance-to-voltage converter for a MEMS capacitive sensor, according to an embodiment of the present invention;
FIG. 4 is a single-ended circuit diagram of a charge-to-voltage conversion module according to an embodiment of the present invention;
fig. 5 is a circuit diagram of a capacitor-voltage conversion circuit according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to specific examples, but the embodiments of the present invention are not limited thereto.
Fig. 1 is a block diagram showing a structure of a capacitance-voltage converter for a MEMS capacitive sensor in the related art, and fig. 2 is a circuit diagram showing a charge-voltage conversion module in the related art. As shown in fig. 1 to 2, the capacitance-voltage conversion circuit 1' includes: voltage excitation source 10 ', common mode charge controller 20', charge-to-voltage conversion module 30 ', optionally, charge-to-voltage conversion module 30' comprises: a charge feedback unit 301 ', a gain error corrector 302 ', and a differential amplifier 303 '.
Specifically, in the charge-voltage conversion module 30 ', the differential amplifier 303 ' includes a differential operational amplifier, and the gain error corrector 302 ' includes a calibration capacitor CC', the charge feedback unit 301' includes an integrating capacitor CI'the capacitance-voltage conversion circuit 1' shares phi1 and phi 2 working phases; in the phase phi 1 of the first period, all capacitors including the preset capacitive sensor 2' are set, and the output voltage is kept at the holding capacitor CH' is in a holding state; in the phi 2 phase of the first period, the sensing capacitors in the preset capacitive sensor 2' are subjected to step voltage signals V with opposite phases through the differential portsRWhich is activated to generate a charge signal representing the difference in capacitance, which is transmitted to the differential operational amplifier. Ideally, the charge signal is integrated by an integrating capacitor CI' absorb all and convert to an output voltage signal, the expression of the output voltage is:
Figure BDA0003316995130000061
wherein, Δ C represents the capacitance value change generated by the sensing capacitance in the preset capacitance sensor under the excitation of the physical signal, VRThe amplitude of the excitation voltage generated for the excitation source.
However, in practical situations, the gain of the differential operational amplifier is not infinite, and thus a gain error occurs, and the expression of the actual output voltage becomes:
Figure BDA0003316995130000062
wherein A is the amplification factor of the differential operational amplifier, sigmadIn order to be a factor of the deterioration,
Figure BDA0003316995130000063
further, in the Φ 1 phase of the second cycle, the capacitor CH' AND capacitance CC' connected to form a feedback loop with the amplifier such that the capacitor C is present during the first cycleH' the output voltage taken as the gain error is stored in the calibration capacitor CC' in (1). With the gradual increase of the operation period, the error term is gradually absorbed, and the output voltage gradually climbs to an ideal value, and the expression is as follows:
Figure BDA0003316995130000064
however, the actual response in the capacitor-voltage converting circuit 1' in the related art still has a hold error phenomenon, that is, during the process of switching from the Φ 2 phase to the Φ 1 phase, due to the hold capacitor CHThe left plate of' has a voltage jump, resulting in an unexpected drop of the output voltage, so that the output voltage value expression becomes:
Figure BDA0003316995130000071
the percentage error of the gain precision is as follows:
Figure BDA0003316995130000072
the inventor finds that the capacitance-voltage conversion circuit 1' of the MEMS capacitive sensor has limited capability of improving gain accuracy, and due to the existence of a holding error, only the equivalent gain of the operational amplifier can be improved by 2 steps, and the set noise of the parasitic capacitance of the capacitive sensor and the output noise of the operational amplifier cannot be effectively suppressed, so that the signal-to-noise ratio of the charge signal of the sensor is low.
Accordingly, the present invention provides a capacitance-voltage converter for a MEMS capacitive sensor to reduce noise and improve gain accuracy.
Fig. 3 is a block diagram of a capacitance-to-voltage converter for a MEMS capacitive sensor according to an embodiment of the present invention. Referring to fig. 3, an embodiment of the invention provides a capacitance-voltage conversion circuit 1 for a MEMS capacitive sensor, including: voltage excitation source 10, common mode charge controller 20 and charge-to-voltage conversion module 30, charge-to-voltage conversion module 30 includes: a first-stage differential amplifier 301, a second-stage differential amplifier 302, a gain error corrector 303, an active noise canceller 304, and a charge feedback unit 305; wherein,
a voltage excitation source 10 for exciting a preset capacitance sensor 40 to generate a charge signal;
a common mode charge controller 20 for absorbing a common mode component in the charge signal;
the first stage differential amplifier 301 is connected to the common-mode charge controller 20, and is configured to amplify a set noise signal of a parasitic capacitance of the preset capacitance sensor 40;
the active noise canceller 304 is connected with the first-stage differential amplifier 301 and is used for absorbing the setting noise signal amplified by the first-stage differential amplifier 301;
the gain error corrector 303 is respectively connected with the active noise canceller 304 and the second-stage differential amplifier 302, and is used for correcting gain errors generated by the first-stage differential amplifier 301 and the second-stage differential amplifier 302;
the second stage differential amplifier 302 is connected to the gain error corrector 303, and is configured to amplify the corrected signal differential component;
the charge feedback unit 305 forms a closed loop with the first-stage differential amplifier 301 and the second-stage differential amplifier 302, and converts a differential component of the excited charge signal into a voltage signal, and realizes differential signal readout.
It can be understood that, after the first stage differential amplifier 301 amplifies the set noise signal of the parasitic capacitance of the predetermined capacitive sensor 40, the active noise canceller 304 connected to the first stage differential amplifier 301 can absorb the set noise signal, and the gain error correctors 303 respectively connected to the active noise canceller 304 and the second stage differential amplifier 302 can correct the gain error generated by the first stage differential amplifier 301 and the second stage differential amplifier 302, so that the noise is reduced while the gain accuracy is improved, thereby significantly improving the energy efficiency.
Fig. 4 is a single-ended circuit diagram of a charge-to-voltage conversion module according to an embodiment of the present invention. As shown in fig. 3 to 4, the capacitor-voltage converter circuit 1 further includes an output voltage signal terminal OUT;
the first stage differential amplifier 301 includes a first differential operational amplifier, and the active noise canceller 304 includes a capacitor: cNAnd a switch:
Figure BDA0003316995130000081
the second stage differential amplifier 302 comprises a second differential operational amplifier, and the gain error corrector 303 comprises a capacitor: cC1And CH1And a switch:
Figure BDA0003316995130000094
and
Figure BDA0003316995130000095
the charge feedback unit 305 includes a capacitor CI1And a switch:
Figure BDA0003316995130000096
and
Figure BDA0003316995130000097
wherein the reverse input terminal of the first differential operational amplifier is connected with the common-mode charge controller 20, the non-inverting input terminal is grounded, and the output terminal is connected with the common-mode charge controller via the capacitor CNAnd CC1The non-inverting input end of the second differential operational amplifier is connected with the non-inverting input end of the second differential operational amplifier, the inverting input end of the second differential operational amplifier is grounded, and the output end of the second differential operational amplifier is connected with an output voltage signal end OUT; cNAnd CC1Includes a first node N1First node N1Warp beam
Figure BDA0003316995130000098
Ground, CC1A second node N is arranged between the same-phase input end of the second differential operational amplifier and the same-phase input end of the second differential operational amplifier2Second node N2Warp beam
Figure BDA0003316995130000099
And
Figure BDA00033169951300000910
grounding;
Figure BDA00033169951300000911
and with
Figure BDA00033169951300000912
Includes a third node N3, CH1And a third node N3The other end of the second differential operational amplifier is connected with the output end of the second differential operational amplifier, and the output end of the second differential operational amplifier passes through
Figure BDA00033169951300000913
And
Figure BDA00033169951300000914
grounding; a fourth node N is included between the common mode charge controller 20 and the inverting input terminal of the first differential operational amplifier4Fourth node N4Warp beam
Figure BDA00033169951300000915
The grounding is carried out on the ground,
Figure BDA00033169951300000916
and
Figure BDA00033169951300000917
includes a fifth node N5, CI1Are respectively connected with a fourth node N4And a fifth node N5And (4) connecting.
Specifically, there are two types of total output noise of the capacitance-voltage conversion circuit 1, one is a preset setting noise of the parasitic capacitance of the capacitance sensor 40, that is, Type-a noise, which is a discrete noise; the second Type is output noise of the first differential operational amplifier and the second differential operational amplifier, namely Type-B noise, which is continuous noise. The embodiment can cancel discrete aliasing noise, namely Type-a noise, by using an active noise cancellation technology, and cannot process continuous time, namely Type-B noise, so that the noise reduction effect depends on the dominance of the Type-a noise, namely, the equivalent input noise of the first differential operational amplifier should be much smaller than the intrinsic thermal noise voltage kT/Cs of the Type-a. The output noise spectrum of the first differential operational amplifier is as follows:
Figure BDA0003316995130000091
wherein,
Figure BDA0003316995130000092
Figure BDA0003316995130000093
then the total output power of Type-B noise is:
Figure BDA0003316995130000101
then the total input power of Type-B noise is:
Figure BDA0003316995130000102
the total input power of Type-a noise is:
Figure BDA0003316995130000103
therefore, the gain of the first stage differential amplifier 301 needs to satisfy the condition:
Figure BDA0003316995130000104
namely A1CL＞＞CS
Fig. 5 is a circuit diagram of the capacitor-voltage conversion circuit 1 according to the embodiment of the present invention. Optionally, as shown in fig. 5, the capacitor-voltage converter circuit 1 further includes a non-inverting output terminal VO+ and an inverted output terminal VO-；
The first stage differential amplifier 301 includes a third differential operational amplifier, and the active noise canceller 304 includes a capacitor: cC21And CC22The second stage differential amplifier 302 comprises a fourth differential operational amplifier, and the gain error corrector 303 comprises a capacitor: cH21、CH22、CC21、CC22And, andswitching:
Figure BDA0003316995130000105
Figure BDA0003316995130000106
and
Figure BDA0003316995130000107
the charge feedback unit 305 includes a capacitance: cI21And CI22And a switch:
Figure BDA0003316995130000108
and
Figure BDA0003316995130000109
wherein,
the non-inverting input terminal of the third differential operational amplifier is connected to the pre-set capacitive sensor 40, the inverting input terminal is connected to the common-mode charge controller 20, and the first output terminal is connected via CC22The non-inverting input end and the second output end which are connected to the fourth differential operational amplifier are connected through CC21The inverting input end of the fourth differential operational amplifier is connected; cC21A sixth node N is arranged between the first differential operational amplifier and the inverting input end of the fourth differential operational amplifier6The sixth node N6Warp beam
Figure BDA00033169951300001010
And
Figure BDA00033169951300001011
grounding;
Figure BDA00033169951300001012
and with
Figure BDA0003316995130000111
Includes a seventh node N7；CH21And a seventh node N7The other end of the fourth differential operational amplifier is connected with the in-phase output end of the fourth differential operational amplifier, and the in-phase output end of the fourth differential operational amplifier is connected with the in-phase output end of the fourth differential operational amplifier
Figure BDA00033169951300001119
And
Figure BDA00033169951300001120
grounding; an eighth node N is included between the common mode charge controller 20 and the inverting input terminal of the third differential operational amplifier8The eighth node N8Warp beam
Figure BDA0003316995130000112
Is grounded and is connected with the ground,
Figure BDA0003316995130000113
and with
Figure BDA0003316995130000114
Includes a ninth node N9，CI21Are respectively connected with an eighth node N8And the ninth node N9Connecting;
CC22a tenth node N is arranged between the fourth differential operational amplifier and the non-inverting input end10The tenth node N10Warp beam
Figure BDA0003316995130000115
And
Figure BDA0003316995130000116
grounding;
Figure BDA0003316995130000117
and with
Figure BDA0003316995130000118
Includes an eleventh node N11；CH22And an eleventh node N11The other end of the fourth differential operational amplifier is connected with the inverted output end of the fourth differential operational amplifier, and the inverted output end of the fourth differential operational amplifier passes through
Figure BDA0003316995130000119
And
Figure BDA00033169951300001110
grounding; preset powerA twelfth node N is arranged between the capacitance sensor 40 and the non-inverting input end of the third differential operational amplifier12The twelfth node N12Warp beam
Figure BDA00033169951300001111
The grounding is carried out on the ground,
Figure BDA00033169951300001112
and
Figure BDA00033169951300001113
between a thirteenth node N13，CI22Are respectively connected with the twelfth node N12And a thirteenth node N13And (4) connecting.
Optionally, the preset capacitance sensor 40 comprises a variable capacitance: cS1And CS2And a switch:
Figure BDA00033169951300001121
and
Figure BDA00033169951300001122
wherein,
Figure BDA00033169951300001123
to one end of and an excitation voltage VRThe connection is carried out by connecting the two parts,
Figure BDA00033169951300001114
one end of the first and second electrodes is grounded,
Figure BDA00033169951300001115
the other end of (1) and
Figure BDA00033169951300001116
are all connected to a fourteenth node N14；CS1And a fourteenth node N14The other end of the third differential operational amplifier is connected with the positive phase input end of the third differential operational amplifier; cS2And a fourteenth node N14The other end of the third differential operational amplifier is connected with the inverting input end of the third differential operational amplifierAnd (4) connecting.
Optionally, the common mode charge controller 20 comprises a capacitance: c01And C02And a switch:
Figure BDA00033169951300001117
and
Figure BDA00033169951300001118
wherein,
Figure BDA00033169951300001124
one end of the first and second electrodes is grounded,
Figure BDA00033169951300001125
one terminal of (1) and an excitation voltage VRThe connection is carried out by connecting the two parts,
Figure BDA00033169951300001126
the other end of (1) and
Figure BDA00033169951300001127
are all connected to a fifteenth node N15；C01And a fifteenth node N15The other end of the third differential operational amplifier is connected with the positive phase input end of the third differential operational amplifier; c02And a fifteenth node N15And the other end of the third differential operational amplifier is connected with the inverting input end of the third differential operational amplifier.
Compared to the charge-to-voltage conversion module 30 shown in fig. 4, the charge-to-voltage conversion module 30 in fig. 5 cancels the active noise by the capacitance CNAnd a calibration capacitor CC1Merging, the merged capacitance CC21Can absorb both the set noise of the parasitic capacitance of the predetermined capacitive sensor 40 and the gain error, and CNAnd CC21The effect of reducing the set noise amplitude after combination is better.
In the present embodiment, the capacitance-voltage conversion circuit 1 has three operating phases Φ 1, Φ 2, and Φ 3 in total, wherein,
Figure BDA0003316995130000121
and
Figure BDA0003316995130000122
in correspondence with the working phase phi 1,
Figure BDA0003316995130000123
and
Figure BDA0003316995130000124
in correspondence with the operating phase phi 2 of the phase,
Figure BDA0003316995130000125
and
Figure BDA0003316995130000126
corresponding to the operating phase Φ 3. In the phase phi 1, the non-inverting input terminal and the inverting input terminal of the first stage differential amplifier 301 are grounded, all capacitors including the sensing capacitor of the preset capacitive sensor 40 are set, and the output voltage is maintained at the holding capacitor CH21And CH22Is in a holding state under the action of the input set noise, and the input set noise is grounded; in the phase phi 2, the parasitic capacitance setting noise of the preset capacitive sensor 40 is frozen to show a stable voltage value, and the noise value is amplified by the capacitor C after passing through the first stage differential amplifier 301C21And CC22Absorption; in the phase Φ 3, the charge signal inputted from the preset capacitive sensor 40 after the set noise is absorbed is integrated by the integrating capacitor CI21And CI22And absorbing and converting the signal into an output voltage signal to realize the signal reading of the capacitive sensor.
It should be understood that, because the charge-voltage conversion module 30 employs two stages of differential amplifiers, the open-loop gain of the circuit can be effectively increased, and thus the gain accuracy can be improved. Optionally, the percentage error of the gain accuracy of the capacitance-voltage conversion circuit is calculated according to the following formula:
Figure BDA0003316995130000127
if the amplification factor A of the first differential operational amplifier1Amplification equal to second differential operational amplifierMultiple A2Then, then
Figure BDA0003316995130000128
Therefore, after the capacitor-voltage conversion circuit 1 provided by the invention is used, the equivalent gain of the operational amplifier can be improved by 3 orders. However, the present invention adopts a two-stage differential amplifier, and when the open-loop gain is increased, the system becomes a double pole, and particularly when the main pole frequency approaches the secondary frequency, the phase margin starts to decrease, and even a gain spike occurs, resulting in oscillation. In order to guarantee a certain phase margin and gain error, the invention provides a weak feedback technology, and by introducing weak feedback, the phase margin at the GBW position is not required to be enough, and only the phase margin at the gain bandwidth of the weak feedback is required to be enough, so that the bandwidth sacrifice of the dominant pole is greatly avoided, and the energy efficiency reduction caused by compensation is avoided while the phase margin is released.
Alternatively, the voltage excitation source 10 generates a step voltage of a predetermined magnitude to excite the predetermined capacitive sensor 40.
It can be understood that, in the capacitance-voltage conversion circuit 1 for the MEMS capacitive sensor according to the present invention, after the voltage excitation source 10 generates the pulse voltage signal with a certain duty ratio, the capacitance signal is converted into the charge signal by exciting the two differential capacitors of the preset capacitance sensor 40; further, the common mode charge controller 20 absorbs the common mode component in the excited charge signal, so as to suppress the common mode charge interference, and the differential component of the charge signal after the common mode charge interference is suppressed enters the charge-voltage conversion module 30, and the charge signal is converted into a voltage signal, so as to implement differential signal reading. According to the invention, through an active noise cancellation technology and a weak feedback technology, under the condition that the sampling frequency is not remarkably increased, the set noise of the common-mode parasitic capacitor can be reduced, the gain precision is improved, theoretically, the gain precision can be improved by 3 orders, and the energy efficiency is further greatly improved; in addition, the problem of insufficient cascade phase margin is solved by using a weak feedback technology, and energy efficiency reduction caused by compensation is avoided while the phase margin is released.
The beneficial effects of the invention are that:
the present invention provides a capacitance-voltage conversion circuit for a MEMS capacitive sensor, comprising: the device comprises a voltage excitation source, a common-mode charge controller and a charge-voltage conversion module; wherein, the charge-voltage conversion module includes: the active noise canceller comprises a first-stage differential amplifier, a second-stage differential amplifier, a gain error corrector, an active noise canceller and a charge feedback unit, wherein after the first-stage differential amplifier amplifies a set noise signal of a preset capacitance sensor parasitic capacitance, the active noise canceller connected with the first-stage differential amplifier can absorb the set noise signal, and the gain error correctors respectively connected with the active noise canceller and the second-stage differential amplifier can correct gain errors generated by the first-stage differential amplifier and the second-stage differential amplifier, so that the gain accuracy is improved while the noise is reduced, and the energy efficiency is remarkably improved.
In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
In the description of the specification, reference to the description of "one embodiment," "some embodiments," "an example," "a specific example," or "some examples" or the like means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples described in this specification can be combined and combined by those skilled in the art.
While the present application has been described in connection with various embodiments, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed application, from a review of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the word "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.
The foregoing is a further detailed description of the invention in connection with specific preferred embodiments and it is not intended to limit the invention to the specific embodiments described. For those skilled in the art to which the invention pertains, numerous simple deductions or substitutions may be made without departing from the spirit of the invention, which shall be deemed to belong to the scope of the invention.

Claims (6)

1. A capacitance-to-voltage conversion circuit for a MEMS capacitive sensor, comprising: a voltage stimulus source, a common mode charge controller, and a charge-to-voltage conversion module, the charge-to-voltage conversion module comprising: the device comprises a first-stage differential amplifier, a second-stage differential amplifier, a gain error corrector, an active noise canceller and a charge feedback unit; wherein,
the voltage excitation source is used for exciting a preset capacitance sensor to generate a charge signal;
the common mode charge controller is used for absorbing a common mode component in the charge signal;
the first-stage differential amplifier is connected with the common-mode charge controller and is used for amplifying a set noise signal of a parasitic capacitor of a preset capacitor sensor;
the active noise canceller is connected with the first-stage differential amplifier and is used for absorbing the set noise signal amplified by the first-stage differential amplifier;
the gain error corrector is respectively connected with the active noise canceller and the second-stage differential amplifier and is used for correcting gain errors generated by the first-stage differential amplifier and the second-stage differential amplifier;
the second-stage differential amplifier is connected with the gain error corrector and is used for amplifying the corrected signal differential component;
the charge feedback unit, the first-stage differential amplifier and the second-stage differential amplifier form a closed loop, and are used for converting the differential component of the excited charge signal into a voltage signal and realizing differential signal readout.
2. The capacitance-to-voltage conversion circuit for a MEMS capacitive sensor of claim 1 further comprising an output voltage signal terminal;
the first stage differential amplifier comprises a first differential operational amplifier, and the active noise canceller comprises a capacitor: cNAnd a switch:
Figure FDA0003316995120000011
the second stage differential amplifier comprises a second differential operational amplifier, and the gain error corrector comprises a capacitor: cC1And CH1And a switch:
Figure FDA0003316995120000021
and
Figure FDA0003316995120000022
the charge feedback unit comprises a capacitor CI1And a switch:
Figure FDA0003316995120000023
and
Figure FDA0003316995120000024
wherein the inverting input terminal of the first differential operational amplifier is connected with the common-mode charge controller, and the non-inverting input terminal is connected with the common-mode charge controllerGround and output end pass through CNAnd CC1The non-inverting input end of the second differential operational amplifier is connected with the non-inverting input end of the second differential operational amplifier, the inverting input end of the second differential operational amplifier is grounded, and the output end of the second differential operational amplifier is connected with the output voltage signal end; cNAnd CC1Includes a first node, the first node is connected with the second node
Figure FDA0003316995120000025
Ground, CC1A second node is arranged between the non-inverting input end of the second differential operational amplifier and the non-inverting input end of the second differential operational amplifier
Figure FDA0003316995120000026
And
Figure FDA0003316995120000027
grounding;
Figure FDA0003316995120000028
and with
Figure FDA0003316995120000029
Includes a third node, CH1One end of the first differential operational amplifier is connected with the third node, the other end of the first differential operational amplifier is connected with the output end of the second differential operational amplifier, and the output end of the second differential operational amplifier passes through
Figure FDA00033169951200000210
And
Figure FDA00033169951200000211
grounding; a fourth node is arranged between the common mode charge controller and the inverting input end of the first differential operational amplifier, and the fourth node is connected with the inverting input end of the first differential operational amplifier
Figure FDA00033169951200000212
The grounding is carried out on the ground,
Figure FDA00033169951200000213
and
Figure FDA00033169951200000214
includes a fifth node, CI1Are connected to the fourth node and the fifth node, respectively.
3. The capacitance-to-voltage conversion circuit for a MEMS capacitive sensor of claim 1 further comprising an in-phase output and an anti-phase output;
the first stage differential amplifier comprises a third differential operational amplifier, and the active noise canceller comprises a capacitor: cC21And CC22The second stage differential amplifier comprises a fourth differential operational amplifier, and the gain error corrector comprises a capacitor: cH21、CH22Said CC21Said CC22And a switch:
Figure FDA00033169951200000215
Figure FDA00033169951200000216
and
Figure FDA00033169951200000217
the charge feedback unit includes a capacitance: cI21And CI22And a switch:
Figure FDA00033169951200000218
Figure FDA00033169951200000219
and
Figure FDA00033169951200000220
wherein,
the non-inverting input end of the third differential operational amplifier is connected with the preset capacitance sensor, the inverting input end of the third differential operational amplifier is connected with the common-mode charge controller, and the first output end of the third differential operational amplifier is connected with the common-mode charge controller through a capacitor CC22The non-inverting input end and the second output end which are connected to the fourth differential operational amplifier are connected through CC21Is connected toAn inverting input terminal of the fourth differential operational amplifier; cC21A sixth node is arranged between the first node and the inverting input end of the fourth differential operational amplifier and is connected with the inverting input end of the fourth differential operational amplifier
Figure FDA00033169951200000221
And
Figure FDA00033169951200000222
grounding;
Figure FDA0003316995120000031
and
Figure FDA0003316995120000032
a seventh node is included in between; cH21One end of the fourth differential operational amplifier is connected with the seventh node, the other end of the fourth differential operational amplifier is connected with the in-phase output end of the fourth differential operational amplifier, and the in-phase output end of the fourth differential operational amplifier passes through
Figure FDA0003316995120000033
And
Figure FDA0003316995120000034
grounding; an eighth node is arranged between the common mode charge controller and the inverting input end of the third differential operational amplifier and is connected with the output end of the common mode charge controller
Figure FDA0003316995120000035
Is grounded and is connected with the ground,
Figure FDA0003316995120000036
and with
Figure FDA0003316995120000037
Includes a ninth node, CI21Both ends of the second node are respectively connected with the eighth node and the ninth node;
CC22a tenth node is arranged between the same-phase input end of the fourth differential operational amplifier and the same-phase input end of the fourth differential operational amplifier, and the tenth node is connected with the same-phase input end of the fourth differential operational amplifier
Figure FDA0003316995120000038
And
Figure FDA0003316995120000039
grounding;
Figure FDA00033169951200000310
and with
Figure FDA00033169951200000311
An eleventh node is included in between; cH22One end of the fourth differential operational amplifier is connected with the eleventh node, the other end of the fourth differential operational amplifier is connected with the inverted output end of the fourth differential operational amplifier, and the inverted output end of the fourth differential operational amplifier passes through
Figure FDA00033169951200000312
And
Figure FDA00033169951200000313
grounding; a twelfth node is arranged between the preset capacitance sensor and the in-phase input end of the third differential operational amplifier and is connected with the output end of the second differential operational amplifier
Figure FDA00033169951200000314
The grounding is carried out on the ground,
Figure FDA00033169951200000315
and
Figure FDA00033169951200000316
including a thirteenth node, CI22Are connected to the twelfth node and the thirteenth node, respectively.
4. The capacitance-to-voltage conversion circuit for a MEMS capacitive sensor of claim 3 wherein the pre-determined capacitance sensor comprises a variable capacitance: cS1And CS2And a switch:
Figure FDA00033169951200000317
and
Figure FDA00033169951200000318
wherein,
Figure FDA00033169951200000319
one end of which is connected to an excitation voltage,
Figure FDA00033169951200000320
one end of the first and second electrodes is grounded,
Figure FDA00033169951200000321
another end of (1) and
Figure FDA00033169951200000322
are connected to a fourteenth node; cS1One end of the first differential operational amplifier is connected with the fourteenth node, and the other end of the first differential operational amplifier is connected with a positive phase input end of a third differential operational amplifier; cS2One end of the differential amplifier is connected with the fourteenth node, and the other end of the differential amplifier is connected with the inverting input end of the third differential operational amplifier.
5. The capacitance-to-voltage conversion circuit for a MEMS capacitive sensor of claim 4, wherein the common mode charge controller comprises a capacitance: c01And C02And a switch:
Figure FDA00033169951200000323
and
Figure FDA00033169951200000324
wherein,
Figure FDA0003316995120000041
one end of the first and second electrodes is grounded,
Figure FDA0003316995120000042
one end of which is connected to an excitation voltage,
Figure FDA0003316995120000043
the other end of (1) and
Figure FDA0003316995120000044
the other end connections of the first and second nodes are all connected to a fifteenth node; c01One end of the first differential operational amplifier is connected with the fifteenth node, and the other end of the first differential operational amplifier is connected with a positive phase input end of a third differential operational amplifier; c02One end of the second differential operational amplifier is connected with the fifteenth node, and the other end of the second differential operational amplifier is connected with the inverting input end of the third differential operational amplifier.
6. The capacitance-to-voltage conversion circuit of claim 1, wherein said voltage excitation source generates a step voltage of a predetermined magnitude to excite said predetermined capacitive sensor.
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