阅读说明：本技术 Mems传感器检测装置以及mems传感器系统 (MEMS sensor detection device and MEMS sensor system ) 是由 李宗伟 韩可都 刘婧 冯方方 杨长春 于 2019-11-06 设计创作，主要内容包括：本发明公开了一种MEMS传感器检测装置以及MEMS传感器系统,所述MEMS传感器检测装置包括：读出电路,用于对MEMS传感器的输出信号进行模拟信号处理,以产生检测电压；抵消电压产生电路,用于根据所述检测电压产生重力抵消电压,所述重力抵消电压和重力加速度成正比例关系；选择电路,用于在反馈阶段选择所述检测电压输出,在重力抵消阶段选择所述重力抵消电压输出,其中,在一个检测周期内所述反馈阶段位于所述重力抵消阶段之后；反馈电路,用于根据所述选择电路的输出电压产生反馈电压,所述反馈电压和所述选择电路的输出电压成正比例关系。本发明公开的MEMS传感器检测装置以及MEMS传感器系统,能够抵消重力加速度的影响,提高MEMS传感器系统的灵敏度。(The invention discloses a MEMS sensor detection device and a MEMS sensor system, wherein the MEMS sensor detection device comprises: the reading circuit is used for carrying out analog signal processing on an output signal of the MEMS sensor to generate a detection voltage; the offset voltage generating circuit is used for generating a gravity offset voltage according to the detection voltage, and the gravity offset voltage and the gravity acceleration are in a direct proportional relation; a selection circuit for selecting the detection voltage output in a feedback phase and the gravity cancellation voltage output in a gravity cancellation phase, wherein the feedback phase is located after the gravity cancellation phase within a detection period; and the feedback circuit is used for generating a feedback voltage according to the output voltage of the selection circuit, and the feedback voltage and the output voltage of the selection circuit are in a direct proportion relation. The MEMS sensor detection device and the MEMS sensor system disclosed by the invention can offset the influence of gravity acceleration and improve the sensitivity of the MEMS sensor system.)

1. A MEMS sensor detection device, comprising:

the reading circuit is used for carrying out analog signal processing on an output signal of the MEMS sensor to generate a detection voltage;

the offset voltage generating circuit is used for generating a gravity offset voltage according to the detection voltage, and the gravity offset voltage and the gravity acceleration are in a direct proportional relation;

a selection circuit for selecting the detection voltage output in a feedback phase and the gravity cancellation voltage output in a gravity cancellation phase, wherein the feedback phase is located after the gravity cancellation phase in a detection period;

and the feedback circuit is used for generating a feedback voltage according to the output voltage of the selection circuit, and the feedback voltage and the output voltage of the selection circuit are in a direct proportion relation.

2. The MEMS sensor sensing apparatus of claim 1, wherein the cancellation voltage generating circuit comprises:

and the first low-pass filter is used for carrying out low-pass filtering processing on the detection voltage so as to generate the gravity counteracting voltage.

3. The MEMS sensor sensing apparatus of claim 1, wherein the cancellation voltage generating circuit comprises:

the second low-pass filter is used for carrying out low-pass filtering processing on the detection voltage to generate a filtering voltage;

the pulse generator is used for generating a positive pulse when the filtering voltage exceeds a preset positive voltage and generating a negative pulse when the filtering voltage exceeds a preset negative voltage;

the counter is used for counting the pulses generated by the pulse generator within a preset time interval, counting and adding 1 when the positive pulses are received, and counting and subtracting 1 when the negative pulses are received;

a register for storing a count value of the counter;

and the first digital-to-analog converter is used for performing digital-to-analog conversion processing on the count value stored by the register so as to generate the gravity offset voltage.

4. The MEMS sensor sensing apparatus of claim 1, wherein the cancellation voltage generating circuit comprises:

the first analog-to-digital converter is used for performing analog-to-digital conversion on the detection voltage to generate a digital signal corresponding to the detection voltage;

the first processing circuit is used for generating a digital signal corresponding to the gravity offset voltage according to the digital signal corresponding to the detection voltage;

and the second digital-to-analog converter is used for performing digital-to-analog conversion processing on the digital signal corresponding to the gravity offset voltage so as to generate the gravity offset voltage.

5. The MEMS sensor detection device of claim 4, wherein the digital signal corresponding to the gravity cancellation voltage is an average value of the digital signal corresponding to the detection voltage within a preset time interval.

6. The MEMS sensor sensing apparatus of claim 1, wherein the selection circuit comprises a first switch and a second switch;

one end of the first switch is used for receiving the detection voltage, one end of the second switch is used for receiving the gravity offset voltage, and the other end of the first switch is connected with the other end of the second switch and serves as the output end of the selection circuit.

7. The MEMS sensor sensing apparatus of claim 1, further comprising:

a detection voltage output terminal for outputting the detection voltage;

and the offset voltage output end is used for outputting the gravity offset voltage.

8. The MEMS sensor sensing apparatus of claim 1, further comprising:

the second analog-to-digital converter is used for performing analog-to-digital conversion on the detection voltage to generate a digital signal corresponding to the detection voltage;

the third analog-to-digital converter is used for performing analog-to-digital conversion on the gravity counteracting voltage to generate a digital signal corresponding to the gravity counteracting voltage;

and the second processing circuit is used for carrying out digital signal processing on the digital signal corresponding to the detection voltage and the digital signal corresponding to the gravity offset voltage.

9. A MEMS sensor system comprising a MEMS sensor, further comprising a MEMS sensor detection device according to any of claims 1 to 8.

10. The MEMS sensor system of claim 9, wherein the MEMS sensor is a three-electrode MEMS sensor;

in a detection period, the ending time of the gravity counteracting stage is the starting time of the feedback stage, and the ending time of the feedback stage is the starting time of the reading stage.

11. The MEMS sensor system of claim 9, wherein the MEMS sensor is a five-electrode MEMS sensor;

in a detection period, the start time of the gravity counteracting stage is read out, the end time of the gravity counteracting stage is the start time of the feedback stage, and the end time of the feedback stage is the end time of the reading out stage.

12. The MEMS sensor system of claim 10 or 11, wherein the duration of the gravity cancellation phase is greater than the duration of the feedback phase.

Technical Field

The invention relates to the technical field of micro electro mechanical systems, in particular to a MEMS sensor detection device and an MEMS sensor system.

Background

Under the further development of artificial intelligence, automatic driving, inertial navigation and the internet of things, signal detection is particularly important, and sensor technologies closely related to signal detection are rapidly developed. Particularly, the development of the internet of things greatly increases the demand of sensor products, and the center of gravity gradually turns to the field of Micro-Electro-Mechanical Systems (MEMS) sensors with higher technical content. The micro-electro-mechanical system is a micro device or system which integrates a micro sensor, a micro actuator, a micro mechanical mechanism, a signal processing and control circuit, a high-performance electronic integrated device, an interface, communication and a power supply into a whole by utilizing the traditional semiconductor process and materials, and has the advantages of small volume, low cost, integration and the like.

Fig. 1 is a schematic circuit diagram of a conventional MEMS sensor system, which employs an analog closed-loop negative feedback architecture, and includes a MEMS sensor 10 and a detection device of the MEMS sensor 10, where the detection device includes a readout circuit 11, a feedback circuit 12, and a switch S11. Specifically, the MEMS sensor 10 is a capacitive MEMS acceleration sensor, and is configured to convert acceleration into a weak signal and output the weak signal; the readout circuit 11 is used for performing analog signal processing such as amplification and filtering on the output signal of the MEMS sensor 10 to generate a detection voltage V_S(ii) a The switch S11 is turned on when the detection device is in the feedback phase to connect the detection voltage V_STo the feedback circuit 12; the feedback circuit 12 is used for detecting the voltage V according to the detection voltage_SGenerating and detecting voltage V_SProportional feedback voltage V_FTo provide a feedback electrostatic force to the MEMS sensor 10 that keeps the proof mass in the MEMS sensor 10 at equilibrium position for a small range of fluctuation at all times.

Sensitivity refers to the detection of the sensor system when it is operating stablyThe ratio of the directional output variation to the input variation. For the MEMS sensor system shown in fig. 1, assuming that the acceleration range detected by the MEMS sensor 10 is ± 2g and the sensitivity is 2V/g, assuming that the maximum value of the output voltage of the readout circuit is 4V, the detection voltage V is_SIs 4V, where g is the acceleration of gravity. If the sensitivity of the MEMS sensor system is to be improved to 4V/g, the voltage V is detected_SThe acceleration range detected by the MEMS sensor 10 is reduced to ± 1g without changing the maximum voltage value of the MEMS sensor. At this time, the MEMS sensor 10 cannot normally operate at the 1g or-1 g position because it cannot detect an acceleration signal greater than 1g at the 1g position and cannot detect an acceleration signal less than-1 g at the-1 g position. It can be seen that the MEMS sensor system shown in fig. 1 contradicts the detection acceleration range and high sensitivity. In applications such as seismic exploration, a high-precision and high-sensitivity MEMS sensor system is required, and the sensitivity of the MEMS sensor system shown in fig. 1 cannot meet the requirement.

Disclosure of Invention

The invention aims to solve the problem of low sensitivity of the existing MEMS sensor system.

The invention is realized by the following technical scheme:

a MEMS sensor detection device, comprising:

the reading circuit is used for carrying out analog signal processing on an output signal of the MEMS sensor to generate a detection voltage;

the offset voltage generating circuit is used for generating a gravity offset voltage according to the detection voltage, and the gravity offset voltage and the gravity acceleration are in a direct proportional relation;

a selection circuit for selecting the detection voltage output in a feedback phase and the gravity cancellation voltage output in a gravity cancellation phase, wherein the feedback phase is located after the gravity cancellation phase in a detection period;

and the feedback circuit is used for generating a feedback voltage according to the output voltage of the selection circuit, and the feedback voltage and the output voltage of the selection circuit are in a direct proportion relation.

Optionally, the cancellation voltage generating circuit includes:

and the first low-pass filter is used for carrying out low-pass filtering processing on the detection voltage so as to generate the gravity counteracting voltage.

Optionally, the cancellation voltage generating circuit includes:

the second low-pass filter is used for carrying out low-pass filtering processing on the detection voltage to generate a filtering voltage;

the pulse generator is used for generating a positive pulse when the filtering voltage exceeds a preset positive voltage and generating a negative pulse when the filtering voltage exceeds a preset negative voltage;

the counter is used for counting the pulses generated by the pulse generator within a preset time interval, counting and adding 1 when the positive pulses are received, and counting and subtracting 1 when the negative pulses are received;

a register for storing a count value of the counter;

and the first digital-to-analog converter is used for performing digital-to-analog conversion processing on the count value stored by the register so as to generate the gravity offset voltage.

Optionally, the cancellation voltage generating circuit includes:

the first analog-to-digital converter is used for performing analog-to-digital conversion on the detection voltage to generate a digital signal corresponding to the detection voltage;

the first processing circuit is used for generating a digital signal corresponding to the gravity offset voltage according to the digital signal corresponding to the detection voltage;

and the second digital-to-analog converter is used for performing digital-to-analog conversion processing on the digital signal corresponding to the gravity offset voltage so as to generate the gravity offset voltage.

Optionally, the digital signal corresponding to the gravity offset voltage is an average value of the digital signals corresponding to the detection voltage within a preset time interval.

Optionally, the selection circuit includes a first switch and a second switch;

one end of the first switch is used for receiving the detection voltage, one end of the second switch is used for receiving the gravity offset voltage, and the other end of the first switch is connected with the other end of the second switch and serves as the output end of the selection circuit.

Optionally, the MEMS sensor detection apparatus further includes:

a detection voltage output terminal for outputting the detection voltage;

and the offset voltage output end is used for outputting the gravity offset voltage.

Optionally, the MEMS sensor detection apparatus further includes:

the second analog-to-digital converter is used for performing analog-to-digital conversion on the detection voltage to generate a digital signal corresponding to the detection voltage;

the third analog-to-digital converter is used for performing analog-to-digital conversion on the gravity counteracting voltage to generate a digital signal corresponding to the gravity counteracting voltage;

and the second processing circuit is used for carrying out digital signal processing on the digital signal corresponding to the detection voltage and the digital signal corresponding to the gravity offset voltage.

Based on the same inventive concept, the invention also provides a MEMS sensor system, which comprises the MEMS sensor and the MEMS sensor detection device.

Optionally, the MEMS sensor is a three-electrode MEMS sensor;

in a detection period, the ending time of the gravity counteracting stage is the starting time of the feedback stage, and the ending time of the feedback stage is the starting time of the reading stage.

Optionally, the MEMS sensor is a five-electrode MEMS sensor;

in a detection period, the start time of the gravity counteracting stage is read out, the end time of the gravity counteracting stage is the start time of the feedback stage, and the end time of the feedback stage is the end time of the reading out stage.

Optionally, the duration of the gravity counteracting stage is longer than the duration of the feedback stage.

Compared with the prior art, the invention has the following advantages and beneficial effects:

according to the MEMS sensor detection device and the MEMS sensor system, the time division multiplexing and gravity counteracting technology is adopted, the counteracting voltage generating circuit is arranged in the MEMS sensor detection device, and the gravity counteracting voltage which is in a direct proportion relation with the gravity acceleration is generated by the counteracting voltage generating circuit according to the detection voltage, so that the influence of the gravity acceleration is counteracted, and the MEMS sensor system can achieve high sensitivity.

Drawings

The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:

FIG. 1 is a schematic circuit diagram of a prior art MEMS sensor system;

FIG. 2 is a timing diagram of the operation of a prior art three-electrode MEMS sensor system;

FIG. 3 is a schematic diagram of a three-electrode MEMS sensor operating in +1g, 0g, and-1 g positions;

FIG. 4 is a schematic circuit diagram of a MEMS sensor system in accordance with an embodiment of the present invention;

FIG. 5 is a schematic circuit diagram of a cancellation voltage generating circuit according to an embodiment of the invention;

fig. 6 is a schematic circuit diagram of a cancellation voltage generating circuit according to another embodiment of the invention;

FIG. 7 is a schematic diagram of a pulse generator generating positive and negative pulses in accordance with an embodiment of the present invention;

FIG. 8 is a schematic circuit diagram of a cancellation voltage generating circuit according to yet another embodiment of the present invention;

FIG. 9 is a diagram illustrating the relationship between the detection voltage and the gravity-offset voltage according to an embodiment of the present invention;

FIG. 10 is a timing diagram of the operation of a three electrode MEMS sensor system of an embodiment of the present invention;

FIG. 11 is a schematic circuit diagram of a MEMS sensor system in accordance with another embodiment of the invention;

FIG. 12 is a schematic circuit diagram of a MEMS sensor system in accordance with yet another embodiment of the invention;

FIG. 13 is a schematic diagram of a five electrode MEMS sensor;

FIG. 14 is a timing diagram of the operation of a prior five electrode MEMS sensor system;

FIG. 15 is a timing diagram of the operation of a five electrode MEMS sensor system of an embodiment of the present invention.

Detailed Description

As described in the background, the sensitivity of the MEMS sensor system of FIG. 1 application is not satisfactory. Taking the MEMS sensor 10 as a three-electrode MEMS sensor as an example, FIG. 2 is a working timing diagram of the MEMS sensor system, wherein φ_FFor the duration of the operation of the MEMS sensor system in the feedback phase, phi_SThe time length of the MEMS sensor system working in the reading phase is defined, namely in a detection period, the end time of the feedback phase is the starting time of the reading phase. FIG. 3 is a schematic diagram of the MEMS sensor system 10 operating in the +1g, 0g, and-1 g positions with the maximum input acceleration of the MEMS sensor system defined by the maximum output voltage of the sensing circuit as:

wherein A is_maxIs the maximum input acceleration, phi_FFor the duration of the feedback phase, F_FFor feedback of electrostatic force, m is the mass of the mass in the MEMS sensor 10, k₁Is a proportionality coefficient, V, related to the electrode parameter and the reference voltage in the MEMS sensor 10_sIs the detection voltage. If the MEMS sensor 10 can operate in all 0g, 1g, and-1 g positions, | A must be satisfied_maxI > 1 g. If the range of the MEMS sensor 10 is + -0.5 g, | A must be satisfied_max| ≧ 1.5 g. Assuming that the detection voltage V is_sFull scale of 3V, when | A_maxWhen |, is 1.5g, the sensitivity is 2V/g. Based on this, the invention provides a MEMS sensorThe system and the MEMS sensor detection device adopt a time division multiplexing technology to offset gravity, and can effectively improve the sensitivity of the MEMS sensor system.

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.

The present embodiment provides a MEMS sensor system and a MEMS sensor detection apparatus, and fig. 4 is a schematic circuit structure diagram of the MEMS sensor system. The MEMS sensor system includes a MEMS sensor 40 and the MEMS sensor detection device, which includes a readout circuit 41, a feedback circuit 42, a cancellation voltage generation circuit 43, and a selection circuit 44.

Specifically, the MEMS sensor 40 is a capacitive MEMS acceleration sensor, and is configured to convert acceleration into a weak electrical signal for output. In a capacitive MEMS acceleration sensor, the movable mass forms one movable electrode of the variable capacitance. When the mass is displaced by the acceleration, the capacitance formed between the fixed electrode and the movable electrode changes, and the magnitude of the acceleration can be measured by detecting the change with the detection device.

The readout circuit 41 is used for performing analog signal processing on the output signal of the MEMS sensor 40 to generate a detection voltage V_S. The readout circuit 41 generally includes a preamplifier and a signal conditioning circuit, where the preamplifier is composed of an operational amplifier and some other components, and is used to amplify the output signal of the MEMS sensor 40, and may be a correlated double sampling circuit or an auto-zero circuit; the signal conditioning circuit is also composed of an operational amplifier and some other components, and is used for processing the output signal of the preamplifier by filtering and the like, and the signal conditioning circuit can be a proportional differentiator, an integrator or a proportional differential integrator and the like.

The cancellation voltage generating circuit 43 is used for generating the cancellation voltage according to the detection voltage V_SGeneratingGravity offset voltage V_DSaid gravity offset voltage V_DAnd is in direct proportion to the gravitational acceleration.

Fig. 5 is a schematic diagram of a circuit structure of the cancellation voltage generating circuit 43, and the cancellation voltage generating circuit 43 includes a first low-pass filter 51. The first low-pass filter 51 is used for filtering the detection voltage V_SLow pass filtering to generate the gravity-offset voltage V_DI.e. the input of the first low-pass filter 51 is used for receiving the detection voltage V_SAn output terminal of the first low-pass filter 51 is used for outputting the gravity-canceling voltage V_D。

Fig. 6 is a schematic diagram of another circuit structure of the cancellation voltage generating circuit 43, and the cancellation voltage generating circuit 43 includes a second low-pass filter 61, a pulse generator 62, a counter 63, a register 64, and a first digital-to-analog converter 65.

Specifically, the second low-pass filter 61 is used for filtering the detection voltage V_SLow pass filtering processing is performed to generate a filtered voltage. The pulse generator 62 is configured to generate a positive pulse when the filtered voltage exceeds a preset positive voltage and a negative pulse when the filtered voltage exceeds a preset negative voltage. FIG. 7 is a schematic diagram of the pulse generator 62 generating positive and negative pulses, where V_SLFor the filtering voltage, Vth1 is the preset positive voltage, and Vth2 is the preset negative voltage. The counter 63 is configured to count pulses generated by the pulse generator 62 within a preset time interval, count by 1 when the positive pulse is received, and count by 1 when the negative pulse is received. The register 64 is configured to store a count value of the counter 63, and the first digital-to-analog converter 65 is configured to perform digital-to-analog conversion processing on the count value stored in the register 64 to generate the gravity cancellation voltage V_D。

The voltage value of the preset positive voltage may be determined according to the voltage value output when the MEMS sensor 40 operates at the 1g position: when the MEMS sensor 40 operates at the 1g position, the larger the voltage value output is, the larger the voltage value of the preset positive voltage is set, and conversely, the smaller the voltage value of the preset positive voltage is set. Accordingly, the voltage value of the preset negative voltage may be determined according to the voltage value output when the MEMS sensor 40 operates at the-1 g position: when the MEMS sensor 40 works at the-1 g position, the larger the voltage value output is, the larger the voltage value of the preset negative voltage is set, and conversely, the smaller the voltage value of the preset negative voltage is set. Further, the voltage value of the preset positive voltage and the voltage value of the preset negative voltage can be adjusted according to the duration of the gravity counteracting stage: the shorter the duration of the gravity cancellation phase is set, the larger the voltage value of the preset positive voltage and the voltage value of the preset negative voltage can be set, and conversely, the smaller the voltage value of the preset positive voltage and the voltage value of the preset negative voltage can be set. The length of the preset time interval is determined by the frequency characteristics of the detected physical quantity: the higher the frequency of the detected physical quantity is, the shorter the preset time interval may be set, whereas the longer the preset time interval may be set, the common time intervals are 0.5s, 1s, 2s, and the like.

Fig. 8 is a schematic diagram of another circuit structure of the cancellation voltage generating circuit 43, and the cancellation voltage generating circuit 43 includes a first analog-to-digital converter 81, a first processing circuit 82, and a second digital-to-analog converter 83.

In particular, the first analog-to-digital converter 81 is used for comparing the detection voltage V_SPerforming analog-to-digital conversion to generate the detection voltage V_SA corresponding digital signal. The first processing circuit 82 is configured to detect the voltage V according to the detected voltage V_SThe corresponding digital signal generates the gravity offset voltage V_DCorresponding digital signal, in the embodiment of the invention, the gravity offset voltage V_DThe corresponding digital signal is the detection voltage V in a preset time interval_SThe average value of the corresponding digital signal, that is,wherein, V_DDFor the gravity-offset voltage V_DCorresponding digital signal, N being the test acquired within the predetermined time intervalVoltage V is measured_SNumber of (2), V_SDiFor the ith detection voltage V_SA corresponding digital signal. The length of the preset time interval can be set according to actual requirements, and the detection voltage V acquired in the preset time interval is ensured_SThe number of (2) is preferably two or more. The second digital-to-analog converter 83 is used for counteracting the gravity force_DPerforming digital-to-analog conversion on the corresponding digital signal to generate the gravity offset voltage V_DDetection voltage V as described in FIG. 9_SAnd the gravity offset voltage V_DSchematic diagram of the relationship of (1). The first processing circuit 82 may be a processing circuit such as a DSP, an FPGA, or an MCU, and it should be noted that the first processing circuit 82 is not limited to calculating the detection voltage V in the preset time interval_SAverage value of corresponding digital signal, and detecting voltage V in the preset time interval_SThe average value of the corresponding digital signal is used as the gravity offset voltage V_DThe first processing circuit 82 can also perform other calculations according to the corresponding digital signal, as long as it is based on the detected voltage V_SThe generated gravity offset voltage V_DAnd the gravity acceleration is in direct proportion. The length of the preset time interval is determined by the frequency characteristics of the detected physical quantity: the higher the frequency of the detected physical quantity is, the shorter the preset time interval may be set, whereas the longer the preset time interval may be set, the common time intervals are 0.5s, 1s, 2s, and the like.

The selection circuit 44 is used for selecting the detection voltage V in the feedback stage_SOutputting, in a gravity counteracting stage, the gravity counteracting voltage V is selected_DAn output, wherein the feedback phase is after the gravity cancellation phase within one detection period. In the embodiment of the present invention, the selection circuit 44 includes a first switch S41 and a second switch S42. One end of the first switch S41 is used for receiving the detection voltage V_SOne end of the second switch S42 is used for receiving the gravity cancellation voltage V_DThe other terminal of the first switch S41 is connected to the other terminal of the second switch S42 and serves as the output terminal of the selection circuit 44. Further, the turning on and off of the first switch S41 is determined by a control signal received by a control terminal of the first switch S41, and the turning on and off of the second switch S42 is determined by a control signal received by a control terminal of the second switch S42. In the feedback phase, the first switch S41 is turned on, the second switch S42 is turned off, and the selection circuit 44 outputs the detection voltage V_S(ii) a During the gravity counteracting stage, the first switch S41 is turned off, the second switch S42 is turned on, and the selection circuit 44 outputs a gravity counteracting voltage V_D. The first switch S41 and the second switch S42 may be PMOS transistors, NMOS transistors, CMOS switch circuits, or the like, which is not limited in the embodiment of the present invention.

The feedback circuit 42 is used for generating a feedback voltage V according to the output voltage of the selection circuit 44_FSaid feedback voltage V_FIn direct proportion to the output voltage of the selection circuit 44. By generating said feedback voltage V_FThe MEMS sensor 40 may be provided with a feedback electrostatic force that causes the proof mass in the MEMS sensor 40 to remain at equilibrium for a small range of fluctuations at all times. The specific circuit structure of the feedback circuit 42 is not an improvement point of the embodiment of the present invention, and an existing feedback circuit structure may be adopted, which is not described again in the embodiment of the present invention.

Taking the MEMS sensor 40 as a three-electrode MEMS sensor as an example, FIG. 10 is a timing diagram of the operation of a three-electrode MEMS sensor system, wherein φ_FFor the duration of the operation of the MEMS sensor system in the feedback phase, phi_SFor the duration of the operation of the MEMS sensor system in the readout phase, phi_DFor the duration of the MEMS sensor system operating in the gravity cancellation phase. In a detection period, the ending time of the gravity counteracting stage is the starting time of the feedback stage, and the ending time of the feedback stage is the starting time of the reading stage.

After the gravity cancellation technology is adopted, the maximum input acceleration of the system is as follows under the limitation of the maximum output voltage of the reading circuit:

wherein, A'_maxIs the maximum input acceleration, phi_FIs the duration of the feedback phase, phi_DFor the duration of the gravity cancellation phase, m is the mass of the mass block in the MEMS sensor 40, k₁And k₂Is a scaling factor related to the electrode parameters and reference voltages in the MEMS sensor 10. If the range of the MEMS sensor 40 is +/-0.5 g, | A'_max| ≧ 1.5 g. Assuming that the detection voltage V is_sFull scale is 3V when | A'_maxWhen 1.5g, the maximum acceleration allowed to be input by the system corresponding to the output full-scale voltage is 0.5g due to the adoption of the gravity offset technology, and the sensitivity is 6V/g at the moment, so that the sensitivity is improved by 3 times compared with the prior art. Therefore, the embodiment of the invention adopts the time-sharing multiplexing technology to offset the gravity, and can effectively improve the sensitivity of the MEMS sensor system.

Referring to fig. 11, in an alternative implementation, the MEMS sensor detection apparatus may further include a cancellation voltage output terminal 1102 in addition to the detection voltage output terminal 1101. The detection voltage output end 1101 is used for outputting the detection voltage V_SThe offset voltage output terminal 1102 is configured to output the gravity offset voltage V_D. At this time, the acceleration signal A output by the system_DC+ACAs follows:

A_DC+ACthe acceleration direct-current component and the alternating-current component which represent the acceleration output by the system when the accelerometer works at any position can provide information such as the inclination angle position and the like while measuring the acceleration signal. By providing the offset voltage output 1102, one more observation can be provided, approximating the detected voltage V_SThe average value of statistical significance is output within a certain time, and the detection voltage V can be measured_SAnd (6) carrying out correction.

Referring to fig. 12, in an alternative implementation, the MEMS sensor detection apparatus may further include a second analog-to-digital converter 1201, a third analog-to-digital converter 1202, and a second processing circuit 1203. The second analog-to-digital converter 1201 is used for detecting the voltage V_SPerforming analog-to-digital conversion to generate the detection voltage V_SA corresponding digital signal; the third analog-to-digital converter 1202 is used for counteracting the gravity force counteracting voltage V_DPerforming analog-to-digital conversion to generate the gravity-cancelling voltage V_DA corresponding digital signal; the second processing circuit 1203 is configured to detect the voltage V_SCorresponding digital signal and the gravity offset voltage V_DAnd carrying out digital signal processing on the corresponding digital signal to output a digital signal Dout. Further, the second processing circuit 1203 may be a processing circuit such as a DSP, an FPGA, or an MCU.

The detection voltage V is converted by an analog-to-digital converter_SAnd a gravity-counteracting voltage V_DConverting into digital signal, and detecting voltage V_SCorresponding digital signal and gravity offset voltage V_DThe corresponding digital signal is processed to output the digital signal Dout, so that the adaptability of a system digital circuit can be enhanced, and the application range of the MEMS sensor is expanded. Meanwhile, more digital signal processing technologies can be applied to further improve the system precision, noise, temperature drift, zero drift and other performances, and the purpose of greatly improving the system performance is achieved. The second processing circuit 1203 specifically performs what kind of processing to set according to actual requirements, which is not limited in the embodiment of the present invention.

For the five-electrode real-time feedback MEMS sensor, if the MEMS sensor can normally work at any angle smaller than 1g, the gravity counteracting technology provided by the embodiment of the invention is also applicable. FIG. 13 is a schematic diagram of a five-electrode MEMS sensor, and FIG. 14 is a timing diagram illustrating operation of a conventional five-electrode MEMS sensor system, wherein φ_FFor the duration of the feedback phase, phi, of the five-electrode MEMS sensor system_SThe duration of the five-electrode MEMS sensor system operating in the readout phase is specified. Detection electrode and feedback of five-electrode MEMS sensorThe electrodes are independent of each other, so that the feedback phase and the readout phase of the five-electrode MEMS sensor coincide. The gravity counteracting technology provided by the embodiment of the invention is applied to a five-electrode MEMS sensor, and is a time-sharing technology introduced into a feedback time sequence to realize gravity counteracting.

Taking the MEMS sensor 40 as a five-electrode MEMS sensor as an example, fig. 15 is a working timing diagram of a five-electrode MEMS sensor system according to an embodiment of the present invention, where Φ_FFor the duration of the operation of the MEMS sensor system in the feedback phase, phi_SFor the duration of the operation of the MEMS sensor system in the readout phase, phi_DFor the duration of the MEMS sensor system operating in the gravity cancellation phase. In a detection period, the start time of the gravity counteracting stage is read out, the end time of the gravity counteracting stage is the start time of the feedback stage, and the end time of the feedback stage is the end time of the reading out stage.

Regardless of whether the gravity cancellation technique provided by the embodiment of the present invention is applied to a three-electrode real-time feedback MEMS sensor or a five-electrode real-time feedback MEMS sensor, generally, the duration phi of the gravity cancellation stage_DGreater than the duration phi of the feedback phase_FFurther, the duration phi of the gravity-cancellation phase_DCan be set to the duration phi of the feedback phase_FMore than twice as much. However, the duration φ of the gravity cancellation phase is not limited by the embodiments of the present invention_DAs long as the duration phi of the gravity counteracting stage_DThe gravity counteraction can be realized.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.