MEMS accelerometer and pull-in failure self-recovery method thereof

Abstract

The accelerometer comprises a sensitive structure and a detection circuit, the sensitive structure comprises an upper fixed pole plate, a lower fixed pole plate and a middle movable pole plate, the upper fixed pole plate and the lower fixed pole plate are respectively connected with the output end of one-out-of-two circuit, and the output end of the other-out-of-two circuit is connected with the output end of the other-out-of-two circuit. The first input end and the second input end of the alternative circuit are connected with feedback voltage Vf / -Vf and preset voltage Vref2 respectively, the output end of the alternative circuit is connected with upper fixed pole plate voltage VT / lower fixed pole plate voltage VB, and accelerometer fixed pole plate voltage VT / VB is not fixedly and uniquely connected with the feedback voltage Vf / -Vf any more. Instead, the feedback voltage Vf / -Vf or the preset voltage Vref2 is automatically selected to be connected in an alternative manner according to the feedback voltage state. According to the invention, the loading voltage on the fixed pole plate is changed online in real time, so that the electrostatic force causing the pull-in failure is removed, and the MEMS accelerometer returns to normal; according to the invention, normal work can be automatically recovered under the condition of uninterruptible power supply when pull-in failure occurs.

Description

Technical Field

[0001] The invention belongs to the technical field of accelerometers, and in particular relates to a MEMS accelerometer and a method for self-recovery of a pull-in failure thereof. Background Art

[0002] As the core component of inertial sensors, MEMS accelerometers have been widely used in consumer electronics, automotive electronics, industrial automation, aerospace, and national defense science and technology. Compared with traditional accelerometers, the introduction of MEMS technology has significantly reduced the size of sensors, reduced power consumption and costs, and improved integration. In particular, closed-loop capacitive MEMS accelerometers have become the first choice for many high-performance applications due to their high sensitivity, low temperature drift, and excellent accuracy.

[0003] The working principle of the closed-loop capacitive MEMS accelerometer is based on the electrostatic servo feedback system, which balances the inertial force caused by external acceleration by precisely controlling the electrostatic force, so that the movable mass block is maintained in a static position. However, this design has inherent limitations when facing extreme environmental stresses, such as acceleration overload, strong vibration or impact. Specifically, adhesion or attraction may occur between the movable mass block and the fixed electrode, that is, adhesion failure or attraction failure, which may lead to sensor failure in severe cases. In the prior art, the stop structure has been proven to be effective for adhesion failure, while the solution to attraction failure mainly relies on power off and restart. However, power off and restart is not only not feasible in some applications, but the stabilization period after restart will temporarily interrupt the normal operation of the sensor, affecting the continuity and real-time nature of the data.

[0004] In view of the above problems, there is an urgent need for a new method that can effectively deal with the failure of pull-in under acceleration overload and vibration shock environment without power off and restart, so as to improve the reliability and robustness of MEMS accelerometers in practical engineering applications. Summary of the invention

[0005] The main purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and to provide a MEMS accelerometer and a method for self-recovery of a pull-in failure thereof. By setting the plate voltage, the plate voltage can be changed in real time to cope with a pull-in failure while ensuring the normal operation of the device, thereby achieving self-recovery of the pull-in failure of the MEMS accelerometer.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention provides a MEMS accelerometer sensitive structure, including an upper fixed plate, a lower fixed plate and a middle movable plate, wherein the upper fixed plate and the lower fixed plate are respectively connected to the output end of a two-choice circuit, and the first input end and the second input end of the two-choice circuit are respectively connected to a feedback voltage V f / -V f and preset voltage V ref2 The output end of the two-choice circuit is connected to a fixed plate voltage V T / Lower fixed plate voltage V B The control end of the two-choice circuit is also connected to a voltage comparator, the output end of the voltage comparator is connected to the control end of the two-choice circuit, and the reverse input end of the voltage comparator is configured as a feedback voltage V f , the positive input terminal of the voltage comparator is configured as a characteristic voltage Vc; the voltage comparator compares the feedback voltage V in real time f and the size of the characteristic voltage Vc, if the feedback voltage V f ≥ characteristic voltage Vc, then the output of the voltage comparator V D High level, control the output voltage to connect to the preset voltage V ref2 ; If the feedback voltage V f <characteristic voltage Vc, then the output of the voltage comparator V D is low level, controlling the output voltage to conduct and connect the feedback voltage V f .

[0008] As a preferred technical solution, the characteristic voltage is a voltage determined according to the voltage value of the feedback voltage when the MEMS accelerometer fails to pull in.

[0009] As a preferred technical solution, the intermediate preload voltage is V ref1 , the preset voltage V ref2 Equal to the preload voltage V ref1 .

[0010] As a preferred technical solution, the two-choice circuit includes a first two-choice circuit and a second two-choice circuit, the first two-choice circuit is electrically connected to the upper fixed plate, and the second two-choice circuit is electrically connected to the lower fixed plate circuit.

[0011] In a second aspect, the present invention provides a MEMS accelerometer, including a sensitive structure and a detection circuit, wherein the sensitive structure is the MEMS accelerometer sensitive structure.

[0012] As a preferred technical solution, the detection circuit includes a C / V converter, a PID controller, a gain adjuster, a force feedback sensor, an A / D collector and a processor. One end of the sensitive structure is connected to the C / V converter, and the other end is connected to the force feedback sensor. The C / V converter, PID controller, gain adjuster, and force feedback sensor are connected in sequence. The A / D collector is connected between the gain adjuster and the force feedback sensor, and the A / D collector is also connected to the processor.

[0013] In a third aspect, the present invention provides a method for self-recovery of a pull-in failure of a MEMS accelerometer, comprising the following steps:

[0014] Assume the DC voltage of the upper plate is V T , the DC voltage of the lower plate is V B , the preload voltage of the movable electrode middle plate is V ref1 ;

[0015] Make the upper plate voltage V T The only connection that is no longer fixed is the feedback voltage V f Connect the upper plate feedback voltage, but choose one of the two to connect the feedback voltage V f / -V f Or the preset voltage V ref2 , where the preset voltage V ref2 Equal to the middle plate preload voltage V ref1 ;

[0016] Obtaining a saturation voltage value Vs of the feedback voltage when the MEMS accelerometer fails to pull in, and setting a value of a characteristic voltage Vc according to the voltage value;

[0017] The feedback voltage V of the MEMS accelerometer f or -V f Compare it with the characteristic voltage Vc when the accelerometer fails to pull in;

[0018] When working, the accelerometer plate voltage V T or V B Connect the feedback voltage V f or -V f , according to V f The comparison result with Vc determines the plate voltage V T or V B Connect V f / -V f Or the preset voltage V ref2 .

[0019] As a preferred technical solution, the accelerometer plate voltage V T / V B Connect the feedback voltage V f / -V f , according to V f The comparison result with Vs determines the plate voltage V T or V B Connect V f / -V f Or the preset voltage V ref2 , specifically:

[0020] If the feedback voltage V fThe voltage value is equal to or higher than the characteristic voltage Vc, indicating that the pull-in failure has occurred at this time, then the accelerometer plate voltage V T / V B Connect the preset voltage V ref2 ;

[0021] If the feedback voltage V f The voltage value is less than the characteristic voltage Vc by a certain value, indicating that the accelerometer is working normally at this time, so the accelerometer plate voltage V T / V B Connect the feedback voltage V f / -V f .

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0023] The present invention is aimed at a closed-loop capacitive MEMS accelerometer, and proposes a MEMS accelerometer and a self-recovery method for its pull-in failure caused by environmental stresses such as acceleration overload, mechanical vibration, and mechanical shock. The method changes the loading voltage on the fixed electrode plate in real time online, thereby releasing the electrostatic force that causes the pull-in failure of the accelerometer, so that the MEMS accelerometer returns to normal, solving the problem that the existing method can only solve the pull-in failure of the MEMS accelerometer by powering off and restarting. The method can realize high-reliability application of MEMS accelerometer products during use, and avoid the situation where the MEMS accelerometer fails and cannot be recovered.

[0024] The closed-loop capacitive MEMS accelerometer failure self-recovery method proposed in the present invention can be completed within milliseconds, and basically does not affect the normal use of the MEMS accelerometer. Therefore, the high-reliability MEMS accelerometer proposed in the present invention can be used in environments with acceleration overload, vibration and shock. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 It is a schematic diagram of a closed-loop capacitive MEMS accelerometer in the prior art;

[0027] Figure 2 It is a schematic diagram of the sensitive structure of a MEMS accelerometer in the prior art;

[0028] Figure 3It is a schematic diagram of the pull-in failure of the sensitive structure of the MEMS accelerometer in the prior art;

[0029] Figure 4 Schematic diagram of voltage connection of the sensitive structure of the MEMS accelerometer according to an embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present application.

[0031] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

[0032] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0033] As described in the background technology, MEMS accelerometers are prone to reliability problems such as pull-in failure under environmental stresses such as acceleration overload, mechanical vibration, and mechanical shock. The solution in the prior art can only be solved by powering off and restarting, because the MEMS accelerometers in the prior art do not have the ability to recover from pull-in failure. Therefore, in order to improve the reliability of MEMS accelerometers during use, the present invention proposes a self-recovery method for pull-in failure caused by environmental stresses such as acceleration overload, mechanical vibration, and mechanical shock for closed-loop capacitive MEMS accelerometers.

[0034] like Figure 1As shown, the closed-loop capacitive MEMS accelerometer of the prior art mainly includes two parts, one is the sensitive structure, and the other is the closed-loop detection circuit. Among them, the capacitive plate of the sensitive structure is composed of an upper plate, a mass block, and a lower plate, wherein the upper plate and the lower plate are fixed, and the mass block connected by a mechanical beam and a fixed anchor is movable. The movable mass block is displaced under the action of the inertial force caused by the external acceleration, thereby causing a change in the differential capacitance, and then the changed capacitance is detected by the capacitance / voltage conversion circuit. The closed-loop detection circuit loads the feedback voltage onto the sensitive structure, and the electrostatic force generated offsets the inertial force, keeping the movable mass block from displacing, so that the feedback voltage reflects the magnitude of the external acceleration, and the magnitude of the external acceleration can be output through the A / D converter and the processor. Define the voltage after C / V conversion and before the PID controller as V a , closed-loop control makes the differential capacitance difference 0, that is, V a Therefore, a key point in the closed-loop detection circuit is that under normal working conditions, after the closed-loop feedback, V a It is a voltage close to 0.

[0035] The sensitive structure of the MEMS accelerometer is an important component. Figure 2 The sensitive structure of the MEMS accelerometer in the prior art is taken as the analysis object, and the force analysis is performed on the movable mass block as the force object:

[0036] When the MEMS accelerometer works normally, the force balance formula of its movable mass block is as follows:

[0037] F s +F e +ma=0

[0038] Among them, F s is the elastic force, F e is the electrostatic force, m is the mass of the movable mass block, and a is the acceleration loaded on the accelerometer by the outside world.

[0039] When acceleration overload occurs (i.e. acceleration is greater than the accelerometer range) or mechanical vibration or mechanical shock occurs, the movable mass block will be displaced. Under certain conditions, the movable mass block cannot return to its normal working position. The accelerometer sensitive structure is generally provided with a stopper structure, which can avoid large-area contact on the interface, thus avoiding adhesion failure. However, at this time, due to the effect of electrostatic force, the MEMS accelerometer will fail to attract, as shown in the schematic diagram. Figure 3 .

[0040] Furthermore, the electrostatic force F between the upper and lower plates e The expression is as follows:

[0041]

[0042] Among them, ε r and ε0 are the absolute and relative dielectric constants, A is the overlapping area of ​​the plates, V1 and V2 are the voltages on the two plates, and d is the distance between the plates.

[0043] The electrostatic force on the movable mass block from the upper and lower plates is as follows:

[0044]

[0045] Among them, F eT When is the electrostatic force of the upper plate on the movable mass block, F eB When is the electrostatic force of the upper plate on the movable mass block, V T and V B is the voltage between the upper plate and the lower plate, V ref is the preload voltage of the movable mass block (middle plate), d0 is the plate spacing when the mass block is in the middle position, and x is the displacement distance of the movable mass block.

[0046] When the movable mass moves toward one side of the plate under the action of acceleration overload, vibration, and impact, the distance between the plates on one side decreases sharply, while the distance between the plates on the other side increases sharply, which causes the electrostatic force applied to the movable mass on one side to be much greater than the other side. Then, the electrostatic force on the movable mass will be much greater than the elastic force, causing the movable mass to be attracted to one side of the plate.

[0047] It can be seen that the power-off restart method previously adopted, that is, to make the voltage on the plate disappear, that is, the electrostatic force disappears, under the action of the elastic force, the mass block will return to the middle position, thereby restoring the attraction failure to normal.

[0048] It is understandable that the voltage V between the upper and lower plates of the conventional MEMS accelerometer sensitive structure is T or V B Connect the feedback voltage V f or -V f When the MEMS accelerometer fails to engage due to acceleration overload, vibration, or impact, the feedback voltage is generally the characteristic voltage Vc of the circuit, which is generally different from the voltage on the movable mass block (middle plate). This results in the electrostatic force increasing without power failure, and the MEMS accelerometer cannot return to normal.

[0049] like Figure 4 As shown, an embodiment of the present application provides a MEMS accelerometer, the core technology of which is that the upper plate and the lower plate are no longer fixed and the only connection feedback voltage V f or -V f , but choose to connect the feedback voltage V fOr the preset voltage V ref2 , preset voltage V ref2 The value is equal to the preload voltage V ref1 When the voltage on the upper plate and the lower plate is equal to the voltage on the middle plate, the electrostatic force on the movable mass block is 0. Under the action of the elastic force, the movable mass block returns to the middle position of the plate. At this time, the MEMS accelerometer can work normally.

[0050] like Figure 4 As shown, the MEMS accelerometer sensitive structure of this embodiment includes an upper fixed plate, a lower fixed plate and a middle movable plate, wherein the upper fixed plate and the lower fixed plate are respectively connected to a two-choice circuit, wherein the first input terminal and the second input terminal of the two-choice circuit are respectively connected to a feedback voltage V f / -V f and preset voltage V ref2 The output end of the two-choice circuit is connected to a fixed plate voltage V T / Lower fixed plate voltage V B The control end of the two-choice circuit is also connected to a voltage comparator, the output end of the voltage comparator is connected to the control end of the two-choice circuit, and the reverse input end of the voltage comparator is configured as a feedback voltage V f , the positive input terminal of the voltage comparator is configured as a characteristic voltage Vc; the voltage comparator compares the feedback voltage V in real time f and the size of the characteristic voltage Vc, if the feedback voltage V f ≥ characteristic voltage Vc, then the output of the voltage comparator V D High level, control the output voltage to connect to the preset voltage V ref2 ; If the feedback voltage V f <characteristic voltage Vc, then the output of the voltage comparator V D is low level, controlling the output voltage to conduct and connect the feedback voltage V f The characteristic voltage Vc is the voltage value of the feedback voltage when the MEMS accelerometer fails to pull in. The intermediate preload voltage is V ref1 , the preset voltage V ref2 Equal to the preload voltage V ref1 .

[0051] It can be understood that the above-mentioned sensitive structure not only refers to the mechanical mechanism, but also includes the electrical connection relationship between the mechanical structures. It is precisely because of the improvement of the sensitive structure in this patent that the MEMS accelerometer based on the above-mentioned sensitive structure can overcome the technical defects of the attraction failure in the prior art. In this patent, the loading voltage on the fixed electrode is changed in real time online, thereby releasing the electrostatic force that causes the attraction failure, so that the MEMS accelerometer returns to normal.

[0052] Please refer again Figure 4 The two-choice circuit in this embodiment can be a two-choice selector, a two-choice analog switch or other circuits that can realize the two-choice function. The two-choice circuit in this embodiment is configured as two, namely the first two-choice circuit and the second two-choice circuit, and the voltage comparator is also configured as two, namely the first voltage comparator and the second voltage comparator. The first two-choice circuit is electrically connected to the upper fixed plate, and the second two-choice circuit is electrically connected to the lower fixed plate circuit. More specifically, the first input terminal and the second input terminal of the first two-choice circuit are respectively connected to the feedback voltage V f and preset voltage V ref2 The output end of the first two-choice circuit is connected to a fixed plate voltage V T The control end of the first two-choice circuit is also connected to a first voltage comparator, the output end of the first voltage comparator is connected to the control end of the first two-choice circuit, and the inverting input end of the first voltage comparator is configured as a feedback voltage V f , the positive input terminal of the first voltage comparator is configured as a characteristic voltage Vc. Similarly, the first input terminal and the second input terminal of the second two-choose-one circuit are respectively connected to the feedback voltage -V f and preset voltage V ref2 The output end of the second two-choose-one circuit is connected to the fixed plate voltage V B The control end of the second two-choose-one circuit is also connected to a second voltage comparator, the output end of the second voltage comparator is connected to the control end of the second two-choose-one circuit, and the inverting input end of the second voltage comparator is configured as a feedback voltage -V f , the positive input terminal of the second voltage comparator is configured as a characteristic voltage Vc.

[0053] Furthermore, the detection circuit in this example adopts Figure 1 The detection circuit shown in the figure includes a C / V converter, a PID controller, a gain adjuster, a force feedback sensor, an A / D collector and a processor. One end of the sensitive structure is connected to the C / V converter, and the other end is connected to the force feedback sensor. The C / V converter, PID controller, gain adjuster and force feedback sensor are connected in sequence. The A / D collector is connected between the gain adjuster and the force feedback sensor, and the A / D collector is also connected to the processor.

[0054] In another embodiment of the present application, a method for self-recovery of a pull-in failure of a MEMS accelerometer is provided, comprising the following steps:

[0055] S1, MEMS accelerometer fixed electrode upper plate DC voltage is V T , the DC voltage of the fixed electrode bottom plate is V B , the preload voltage of the movable electrode intermediate plate is Vref1 ;

[0056] S2, accelerometer plate voltage V T or V B The only connection that is no longer fixed is the feedback voltage V f or -V f , but choose to connect the feedback voltage V f Or the preset voltage V ref2 , preset voltage V ref2 The value is equal to the preload voltage V ref1 ;

[0057] S3. Obtain the voltage value V of the feedback voltage when the accelerometer fails to pull in s , according to the voltage V s Determine the characteristic voltage Vc;

[0058] S4, the feedback voltage V f Compare with characteristic voltage Vc;

[0059] S5, under normal conditions, the accelerometer plate voltage V T or V B Connect the feedback voltage V f or -V f , according to V f The comparison result with Vs determines the plate voltage V T or V B Connect V f / -V f Or the preset voltage V ref2 , specifically:

[0060] S51, if the feedback voltage V f The voltage value is equal to or higher than the characteristic voltage Vs, indicating that the pull-in failure has occurred at this time, then the accelerometer plate voltage V T or V B Connect the preset voltage V ref2 ;

[0061] S52, if the feedback voltage V f The voltage value is less than the characteristic voltage Vs, indicating that the accelerometer is working normally. Then the accelerometer plate voltage V T or V B Connect the feedback voltage V f or -V f .

[0062] It can be understood that based on the working principle of the closed-loop capacitive MEMS accelerometer and the fault mechanism that leads to the failure of the pull-in, the present invention sets the plate voltage. While ensuring the normal operation of the device, the plate voltage can be changed in real time to cope with the pull-in failure, thereby achieving self-recovery of the MEMS accelerometer's pull-in failure.

[0063] In a more specific embodiment, taking a comb-tooth closed-loop capacitive MEMS accelerometer as an example, the method of self-recovery of its pull-in failure is further described:

[0064] (1) First, a comb-tooth closed-loop capacitive MEMS accelerometer is selected, whose characteristics are as follows:

[0065] (1.1) The operating voltage of the accelerometer is 5V;

[0066] (1.2) The accelerometer zero bias voltage is 2.5V, the scale factor is 200mV / g, and the range is ±10g. The accelerometer normally operates with an output voltage of 0.5V-4.5V.

[0067] (1.3) The preload voltage of the middle plate of the accelerometer is 3V;

[0068] (2) Make the sample fail to close and obtain the feedback saturation voltage V of the accelerometer s is 4.8V, determine the characteristic voltage V c 4.7V;

[0069] (3) Design the upper / lower plate voltage of the MEMS accelerometer sensitive structure:

[0070] (3.1) Real-time comparison of feedback voltage V through voltage comparator f and characteristic voltage V c (4.7V): a. If the feedback voltage ≥ characteristic voltage V c , then the output of the voltage comparator V D is high level; b. If the feedback voltage is less than the characteristic voltage V c , then the output of the voltage comparator V D is low level;

[0071] (3.2) The output of the voltage comparator V D (high level or low level) as the control voltage of the voltage two-choice selection circuit;

[0072] (3.3) The input of the two-choice selection circuit is connected to the feedback voltage V f and preset voltage V ref2 =V ref1 =3V, the output end is connected to the upper plate V T / Electrode plate voltage V B, the control voltage controls whether the upper plate voltage at the output is connected to the feedback voltage or the preset voltage:

[0073] (3.3.1) If the control terminal voltage V D is low level, the output voltage V T (Upper plate voltage) is connected to the feedback voltage V f ;

[0074] (3.3.2) If the control terminal voltage V D is high, the output voltage V T The preset voltage V ref2 ;

[0075] (4) When V f =4V (indicating that the device is working properly), the voltage comparator output is low level, the upper plate voltage is connected to the feedback voltage, and the MEMS accelerometer works normally;

[0076] (5) When V f =4.8V (indicating that the device is not working properly and the pull-in may fail), the voltage comparator outputs a high level, the upper plate voltage is connected to the preset voltage, the voltage difference between the plates is 0, the electrostatic force between the plates disappears, the movable mass block returns to the middle position, and the feedback voltage drops to less than 4.8V. At this time, the voltage comparator outputs a low level, the upper plate voltage is connected to the feedback voltage, and the MEMS accelerometer resumes normal operation.

[0077] The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0078] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A MEMS accelerometer sensitive structure, characterized in that: It includes an upper fixed plate, a lower fixed plate and a middle movable plate, wherein the upper fixed plate and the lower fixed plate are respectively connected to an output end of a two-choice circuit, and the first input end and the second input end of the two-choice circuit are respectively connected to a feedback voltage V f / -V f and preset voltage V ref2 The output end of the two-choice circuit is connected to a fixed plate voltage V T / Lower fixed plate voltage V B The control end of the two-choice circuit is also connected to a voltage comparator, the output end of the voltage comparator is connected to the control end of the two-choice circuit, and the reverse input end of the voltage comparator is configured as a feedback voltage V f , the positive input terminal of the voltage comparator is configured as a characteristic voltage Vc; the voltage comparator compares the feedback voltage V in real time f and the size of the characteristic voltage Vc, if the feedback voltage V f ≥ characteristic voltage Vc, then the output of the voltage comparator V D High level, control the output voltage to connect to the preset voltage V ref2 ; If the feedback voltage V f <characteristic voltage Vc, then the output of the voltage comparator V D is low level, controlling the output voltage to conduct and connect the feedback voltage V f .

2. The MEMS accelerometer sensitive structure according to claim 1, characterized in that: The characteristic voltage is a voltage determined according to the voltage value of the feedback voltage when the MEMS accelerometer fails to pull in.

3. The MEMS accelerometer sensitive structure according to claim 1, characterized in that: The intermediate preload voltage is V ref1 , the preset voltage V ref2 Equal to the preload voltage V ref1 .

4. The MEMS accelerometer sensitive structure according to claim 1, characterized in that: The two-choice circuit includes a first two-choice circuit and a second two-choice circuit, wherein the first two-choice circuit is electrically connected to the upper fixed plate, and the second two-choice circuit is electrically connected to the lower fixed plate.

5. A MEMS accelerometer, characterized in that: It comprises a sensitive structure and a detection circuit, wherein the sensitive structure is the MEMS accelerometer sensitive structure described in any one of claims 1 to 4.

6. The MEMS accelerometer according to claim 4, characterized in that: The detection circuit includes a C / V converter, a PID controller, a gain adjuster, a force feedback sensor, an A / D collector and a processor. One end of the sensitive structure is connected to the C / V converter, and the other end is connected to the force feedback sensor. The C / V converter, PID controller, gain adjuster, and force feedback sensor are connected in sequence. The A / D collector is connected between the gain adjuster and the force feedback sensor, and the A / D collector is also connected to the processor.

7. A method for self-recovery of a pull-in failure of a MEMS accelerometer as claimed in claim 4 or 5, characterized in that: The steps include: Assume the DC voltage of the upper plate is V T , the DC voltage of the lower plate is V B , the preload voltage of the movable electrode middle plate is V ref1 ; Make the upper plate voltage V T The only connection that is no longer fixed is the feedback voltage V f Connect the upper plate feedback voltage, but choose one of the two to connect the feedback voltage V f / -V f Or the preset voltage V ref2 , where the preset voltage V ref2 Equal to the middle plate preload voltage V ref1 ; Obtaining a saturation voltage value Vs of the feedback voltage when the MEMS accelerometer fails to pull in, and setting a value of a characteristic voltage Vc according to the voltage value; The feedback voltage V of the MEMS accelerometer f or -V f Compare it with the characteristic voltage Vc when the accelerometer fails to pull in; When working, the accelerometer plate voltage V T or V B Connect the feedback voltage V f or -V f , according to V f The comparison result with Vc determines the plate voltage V T or V B Connect V f / -V f Or the preset voltage V ref2 .

8. The method for self-recovery of a pull-in failure of a MEMS accelerometer according to claim 7, characterized in that: Accelerometer plate voltage V T / V B Connect the feedback voltage V f / -V f , according to V f The comparison result with Vs determines the plate voltage V T or V B Connect V f / -V f Or the preset voltage V ref2 , specifically: If the feedback voltage V f The voltage value is equal to or higher than the characteristic voltage Vc, indicating that the pull-in failure has occurred at this time, then the accelerometer plate voltage V T / V B Connect the preset voltage V ref2 ; If the feedback voltage V f The voltage value is less than the characteristic voltage Vc by a certain value, indicating that the accelerometer is working normally at this time, so the accelerometer plate voltage V T / V B Connect the feedback voltage V f / -V f .

Images