CN114280330A - MEMS closed-loop accelerometer and control method thereof - Google Patents
MEMS closed-loop accelerometer and control method thereof Download PDFInfo
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Abstract
The invention relates to a MEMS closed-loop accelerometer and a control method thereof, wherein the MEMS closed-loop accelerometer comprises: the MEMS sensitive structure comprises a mass block, a driving capacitor connected with the mass block and a detection capacitor; the detection circuit module is used for converting a capacitance signal of the detection capacitor into a voltage signal; the feedback control circuit module is connected with the detection circuit module; a capacitance detection loop is formed between the detection capacitor and the detection circuit module, and a voltage feedback control loop is formed between the driving capacitor, the detection circuit module and the feedback control circuit module; and the switch control module is used for switching the capacitance detection loop and the voltage feedback control loop and comprises a first fixed capacitor, a first switch connected with the capacitance detection loop and the voltage feedback control loop and a second switch connected with the first fixed capacitor and the capacitance detection loop. By the mode, the size of the driving capacitor can be improved, and the feedback electrostatic force is increased.
Description
Technical Field
The invention relates to the technical field of micro-electro-mechanical systems, in particular to an MEMS closed-loop accelerometer and a control method thereof.
Background
Micro-electromechanical systems (MEMS) are developed on the basis of microelectronics, and incorporate micro-sensors, micro-actuators, micro-mechanical structures, micro-power micro-energy sources, signal processing and control circuits, high-performance electronic integrated devices, interfaces, and communication, etc. into a single micro-device or system. MEMS is a revolutionary new technology, is widely applied to high and new technology industries, and is a key technology related to national science and technology development, economic prosperity and national defense safety.
The MEMS accelerometer is a device for measuring acceleration, and the most commonly adopted technical route of the MEMS accelerometer in the industry at present is a capacitive detection mode, namely the MEMS accelerometer comprises a sensitive unit and a conditioning circuit, wherein the sensitive unit converts external acceleration change into displacement of an internal mass block, the displacement is converted into capacitance change through a capacitance electrode, and the capacitance change is converted into a voltage signal through the conditioning circuit.
The MEMS capacitive accelerometer adopts a closed-loop structure, namely, a conditioning circuit additionally generates direct current bias voltage in proportion to detected acceleration, the direct current bias voltage is fed back and loaded to a driving electrode of a sensitive unit part, inertia force generated by the acceleration on a mass block is counteracted through electrostatic force between the driving electrode and the mass block, and the mass block which is influenced by the acceleration and is displaced is pulled back to an initial position. The closed-loop architecture has the advantages of excellent nonlinearity, low drift and the like.
In the MEMS capacitive closed-loop accelerometer, the system can operate stably when the electrostatic force is sufficient to counteract the inertial force. The magnitude of the electrostatic force which can be generated between the driving electrode and the mass block determines the magnitude of the inertial force caused by the acceleration which can be counteracted by the electrostatic force, namely the upper measuring range limit of the accelerometer. In addition, when the input acceleration is too large, namely overload occurs, the failure problems such as structural collision and fragmentation or capacitor plate adhesion can be caused, and the electrostatic force loaded in the opposite direction can partially offset the overload degree under the condition, so that the acceleration threshold value triggering overload failure is improved, and the failure probability is reduced. Therefore, it is beneficial to increase the upper limit of the feedback electrostatic force in the system.
As can be seen from the calculation formula of the electrostatic force, increasing the feedback electrostatic force in the above system requires increasing the voltage between the driving electrode and the mass, or increasing the capacitance of the driving electrode. The upper limit of the voltage loaded on the driving electrode is determined by the conditioning circuit, and the upper limit of the output voltage of the conditioning circuit is limited by the high-voltage-resistant capability of the circuit chip, namely the high-voltage-resistant capability of the transistor in the adopted processing technology, and the complexity and the cost of the processing technology can be obviously increased by improving the high-voltage-resistant capability of the transistor. The way of increasing the capacitance of the driving electrode includes increasing the relative dielectric constant of the driving electrode, increasing the facing area of the capacitor plate, and decreasing the distance between the capacitor plates. The increase of the relative dielectric constant can significantly affect the working characteristics of the sensitive unit, the increase of the facing area of the capacitor plate can increase the size and cost of the device, and the distance between the capacitor plates is limited by the processing technology and cannot be easily reduced.
Disclosure of Invention
Based on the MEMS closed-loop accelerometer and the control method thereof, the size of the driving capacitor can be improved, and the feedback electrostatic force is increased, so that the measuring range and the reliability of the MEMS closed-loop accelerometer are improved.
In order to solve the technical problems, the invention adopts a technical scheme that: there is provided a MEMS closed-loop accelerometer comprising:
the MEMS sensitive structure comprises a mass block, a driving capacitor and a detection capacitor, wherein the driving capacitor is connected with the mass block and used for driving the mass block to displace through electrostatic force, and the detection capacitor is connected with the mass block and used for detecting the displacement of the mass block;
the detection circuit module is used for converting a capacitance signal of the detection capacitor into a voltage signal;
the feedback control circuit module is connected with the detection circuit module and is used for controlling the driving voltage loaded to the driving capacitor according to the output of the detection circuit module; a capacitance detection loop is formed between the detection capacitor and the detection circuit module, and a voltage feedback control loop is formed between the driving capacitor, the detection circuit module and the feedback control circuit module; and
the switch control module is used for switching the capacitance detection loop and the voltage feedback control loop and comprises a first fixed capacitor, a first switch and a second switch, wherein the first switch is connected with the capacitance detection loop and the voltage feedback control loop, and the second switch is connected with the first fixed capacitor and the capacitance detection loop.
According to an embodiment of the present invention, the driving capacitors include a first driving capacitor located on one side of the mass and a second driving capacitor located on an opposite side of the first driving capacitor, and the detection capacitors include a first detection capacitor located on the same side as the first driving capacitor or the second driving capacitor and a second detection capacitor located on an opposite side of the first detection capacitor.
According to one embodiment of the present invention, the voltage feedback control loop includes a first loop for controlling the driving voltage applied to the first driving capacitor and a second loop for controlling the driving voltage applied to the second driving capacitor.
According to an embodiment of the present invention, one of the first loop and the second loop feeds back a driving voltage of a corresponding driving capacitor, and the direction of change of the voltage output by the capacitor detection loop is consistent; the other remaining loop feeds back the driving voltage of the corresponding driving capacitor, and the change direction of the voltage output by the capacitor detection loop is opposite to that of the voltage output by the capacitor detection loop.
According to an embodiment of the invention, the detection circuit module comprises a first input terminal for detecting the first detection capacitance and a second input terminal for detecting the second detection capacitance, when the driving voltage fed back to the corresponding driving capacitor by the second loop is opposite to the change direction of the voltage output by the capacitor detection loop, the second input end is connected with the second detection capacitor, the main body of the first switch is connected with the first detection capacitor, a first contact of the first switch is arranged in the capacitance detection loop, a second contact of the first switch is arranged in the first loop, the main body of the second switch is connected with the first input end, the first contact of the second switch is connected with the first contact of the first switch, and the second contact of the second switch is connected with the first fixed capacitor.
According to an embodiment of the invention, the detection circuit module comprises a first input terminal for detecting the first detection capacitance and a second input terminal for detecting the second detection capacitance, when the driving voltage fed back to the corresponding driving capacitor by the first loop is opposite to the change direction of the voltage output by the capacitor detection loop, the first input end is connected with the first detection capacitor, the main body of the first switch is connected with the second detection capacitor, the first contact of the first switch is arranged in the capacitance detection loop, the second contact of the first switch is arranged in the second loop, the main body of the second switch is connected with the second input end, the first contact of the second switch is connected with the first contact of the first switch, and the second contact of the second switch is connected with the first fixed capacitor.
According to an embodiment of the invention, the switch control module comprises a second fixed capacitor electrically connected to the mass, a third switch connected to both the capacitance detection loop and the voltage feedback control loop, and a fourth switch connected to both the second fixed capacitor and the capacitance detection loop.
According to an embodiment of the present invention, the detection circuit module includes a first input terminal for detecting the first detection capacitor and a second input terminal for detecting the second detection capacitor, a main body of the first switch is connected to the first detection capacitor, a first contact of the first switch is disposed in the capacitor detection circuit, a second contact of the first switch is disposed in the first circuit, a main body of the second switch is connected to the first input terminal, a first contact of the second switch is connected to the first contact of the first switch, and a second contact of the second switch is connected to the first fixed capacitor; the main body of the third switch is connected with the second detection capacitor, the first contact of the third switch is arranged in the capacitor detection loop, the second contact of the third switch is arranged in the second loop, the main body of the fourth switch is connected with the second input end, the first contact of the fourth switch is connected with the first contact of the third switch, and the second contact of the fourth switch is connected with the second fixed capacitor.
In order to solve the technical problem, the invention adopts another technical scheme that: a control method is provided, which is applied to the MEMS closed-loop accelerometer and comprises the following steps:
monitoring the capacitance value of a detection capacitor of the MEMS sensitive structure in real time through a detection circuit module;
when the capacitance value is monitored to reach a preset first capacitance threshold value, a first switch and a second switch are controlled to switch a detection capacitor in an MEMS sensitive structure connected to the capacitance detection circuit into a voltage feedback control circuit, and a first fixed capacitor is connected to the capacitance detection circuit.
According to an embodiment of the present invention, the control method further includes:
continuously monitoring the capacitance value of a detection capacitor of the MEMS sensitive structure through the detection circuit module;
and when the capacitance value is monitored to reach a preset second capacitance threshold value, controlling the first switch and the second switch to switch a detection capacitor connected into the voltage feedback control loop in the MEMS sensitive structure into the capacitance detection loop.
The invention has the beneficial effects that: the capacitance detection circuit and the voltage feedback control circuit are switched in the MEMS closed-loop accelerometer through the switch control module, when the mass block displaces, the capacitance detection circuit is switched to the voltage feedback control circuit, the detection capacitor originally connected into the MEMS sensitive structure of the capacitance detection circuit is switched into the voltage feedback control circuit, the first fixed capacitor is connected into the capacitance detection circuit, the first fixed capacitor is used as a temporary detection capacitor, the size of the driving capacitor is improved without changing the parameter of the driving capacitor, the electrostatic force feedback effect is increased, and the measuring range and the reliability of the MEMS closed-loop accelerometer are improved.
Drawings
Fig. 1 is a schematic structural diagram of a switch control module of a MEMS closed-loop accelerometer according to an embodiment of the present invention, which connects all detection capacitors to a capacitance detection circuit;
FIG. 2 is a schematic structural diagram of a MEMS sensitive structure according to an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a switch control module of the MEMS closed-loop accelerometer of the present invention, which switches part of the detection capacitor into a voltage feedback control loop.
The meaning of the reference symbols in the drawings is:
100-MEMS closed-loop accelerometer; 10-a MEMS sensitive structure; 20-a detection circuit module; 30-a feedback control circuit module; 40-a switch control module; 50-capacitance detection loop; 60-voltage feedback control loop; 11-cantilever beam; 12-a mass block; 13-a drive capacitance; 14-detecting capacitance; 15-anchor point; c1 — first detection capacitance; c2 — second detection capacitance; c3 — first drive capacitance; c4 — second drive capacitance; c5 — first fixed capacitance; s1 — a first switch; a-a second contact of the first switch; b-a first contact of a first switch; s2 — a second switch; c-a first contact of a second switch; d-a second contact of a second switch; 601-a first loop; 602-a second loop; 603-inverter.
Detailed Description
To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
Referring to fig. 1, which is a schematic structural diagram of a switch control module of a MEMS closed-loop accelerometer according to an embodiment of the present invention, which switches all detection capacitors into a capacitance detection loop, the MEMS closed-loop accelerometer 100 includes a MEMS sensitive structure 10, a detection circuit module 20, a feedback control circuit module 30, and a switch control module 40.
In an implementation, referring to fig. 2, the MEMS sensing structure 10 includes a cantilever beam 11, a mass 12 connected to the cantilever beam 11, a driving capacitor 13 connected to the mass 12 for driving the mass 12 to displace, and a sensing capacitor 14 connected to the mass 12 for sensing the mass 12 to displace.
The shape and size of the mass block 12 are not particularly limited, the mass block 12 of the present embodiment is rectangular, a plurality of, preferably four, cantilever beams 11 are provided, four top corners of the mass block 12 are respectively provided with one cantilever beam 11, each cantilever beam 11 is provided with an anchor point 15, the bottom of the mass block 12 is suspended and movable, and the mass block 12 is fixed on the anchor point 15 through the cantilever beams 11. Further, the driving capacitor 13 includes a first driving capacitor C3 located above the mass block 12 and a second driving capacitor C4 located below the mass block 12, and the detection capacitor 14 includes a first detection capacitor C1 disposed on the same side as the first driving capacitor C3 and a second detection capacitor C2 disposed on the same side as the second driving capacitor C4. The first detection capacitors C1 are disposed in two groups and respectively located at two sides of the first driving capacitor C3, and the second detection capacitors C2 are disposed in two groups and respectively located at two sides of the second driving capacitor C4.
The driving capacitor 13 and the detecting capacitor 14 of the present embodiment are both of an interdigital capacitor structure. Specifically, each of the driving capacitor 13 and the detecting capacitor 14 includes a movable plate (not shown) connected to the mass 12 and a fixed plate (not shown) coupled to the movable plate. Detection circuit module 20 is connected to anchor point 15 and the fixed plate of detection capacitor 14, and feedback control circuit module 30 is connected to anchor point 15 and the fixed plate of drive capacitor 13.
Further, referring to fig. 1, the detection circuit module 20 is configured to convert the capacitance signal of the detection capacitor 14 into a voltage signal; the detection circuit block 20 comprises a first input terminal for detecting the first detection capacitor C1 and a second input terminal for detecting the second detection capacitor C2, an output terminal of the detection circuit block 20 being connected to the feedback control circuit block 30.
Further, the feedback control circuit module 30 is connected to the detection circuit module 20 and configured to control the driving voltage applied to the driving capacitor 13 according to the output of the detection circuit module 20.
Referring to fig. 1 and fig. 3, a capacitance detection loop 50 is formed between the detection capacitor 14 and the detection circuit module 20, and a voltage feedback control loop 60 is formed between the driving capacitor 13, the detection circuit module 20 and the feedback control circuit module 30. The voltage feedback control loop 60 comprises a first loop 601 for controlling the driving voltage loaded to the first driving capacitor C3 and a second loop 602 for controlling the driving voltage loaded to the second driving capacitor C4, wherein one of the first loop 601 and the second loop 602 feeds back the driving voltage of the corresponding driving capacitor in accordance with the change direction of the voltage output by the capacitance detection loop 50; the other loop feeds back the driving voltage of the corresponding driving capacitor, and the change direction of the voltage output by the capacitor detection loop 50 is opposite. Specifically, the driving voltages fed back to the corresponding driving capacitors in the first loop 601 and the second loop 602 are provided with an inverter 603 in a loop opposite to the change direction of the voltage output by the capacitance detection loop 50, the inverter 603 is connected to the output end of the feedback control circuit module 30, and the inverter 603 is used for changing the change direction of the voltage output by the feedback control circuit module 30. For example, if the driving voltage fed back from the first loop 601 to the first driving capacitor C3 changes in a direction opposite to the voltage output from the capacitance detection circuit 50, the inverter 603 is disposed in the first loop 601 and connected to the output terminal of the feedback control circuit module 30; if the driving voltage fed back to the second driving capacitor C4 by the second loop 602 changes in the opposite direction to the voltage output by the capacitance detection circuit 50, the inverter 603 is disposed in the second loop 602 and connected to the output terminal of the feedback control circuit module 30, as shown in fig. 1. The reverser 603 is specifically arranged on the first loop 601 or on the second loop 602 in relation to the direction of acceleration or displacement of the mass 12.
When acceleration in the downward direction in fig. 1 is detected, the mass block 12 moves downward, the capacitance at the upper side decreases, the capacitance at the lower side increases, the detection circuit module 20 detects the magnitudes of the first detection capacitor C1 and the second detection capacitor C2 and calculates a differential capacitance value, and simultaneously converts the differential capacitance value into a voltage value to be output to the feedback control circuit module 30, the feedback control circuit module 30 controls the driving voltages applied to the first driving capacitor C3 and the second driving capacitor C4 according to the voltage value, that is, the voltage fed back to the first driving capacitor C3 at the upper side increases Δ V, and the voltage applied to the second driving capacitor C4 at the lower side decreases Δ V. The electrostatic force between drive capacitor 13 and mass 12 pulls mass 12 upward to counteract the downward inertial force generated by the acceleration, causing it to return to its original position. In the initial state, the voltages applied to the anchor point 15 and the fixed plate by the feedback control circuit module 30 are both V0, and V0 is a preset value.
Further, the switch control module 40 is used to switch the capacitance detection loop 50 and the voltage feedback control loop 60. Specifically, when the external acceleration is large enough and the absolute value of the difference between the first detection capacitor C1 and the second detection capacitor C2 calculated by the detection circuit module 20 reaches a preset first capacitance threshold, the switch control module 40 is controlled to switch the detection capacitor 14 connected to the MEMS sensitive structure 10 of the capacitance detection circuit 50 into the voltage feedback control circuit 60. Continuously monitoring the capacitance value of the detection capacitor 14 of the MEMS sensitive structure 10 through the detection circuit module 20; when the capacitance value is monitored to reach the preset second capacitance threshold value, the control switch control module 40 is controlled to switch the detection capacitor 14 connected to the voltage feedback control loop 60 in the MEMS sensitive structure 10 to the capacitance detection loop 50.
Further, referring to fig. 1 and 3, the switch control module 40 includes a first fixed capacitor, a first switch S1 connected to the capacitance detection circuit 50 and the voltage feedback control circuit 60, and a second switch S2 connected to the first fixed capacitor C5 and the capacitance detection circuit 50.
In an implementation manner, as shown in fig. 1, when the driving voltage fed back to the second driving capacitor C4 by the second loop 602 is opposite to the change direction of the voltage output by the capacitance detection loop 50, the second input terminal of the detection circuit module 20 is connected to the second detection capacitor C2, the main body of the first switch S1 is connected to the first detection capacitor C1, the first contact B of the first switch S1 is disposed in the capacitance detection loop 50, the second contact a of the first switch S1 is disposed in the first loop 601, the main body of the second switch S2 is connected to the first input terminal of the detection circuit module 20, the first contact C of the second switch S2 is connected to the first contact B of the first switch S1, and the second contact D of the second switch S2 is connected to the first fixed capacitor C5.
As shown in fig. 1, when the acceleration is zero, the mass 12 is in an initial equilibrium state, the capacitance values of the first detection capacitor C1 and the second detection capacitor C2 are equal, and the voltage applied to the anchor point 15 and the fixed plate by the feedback control circuit module 30 is V0. When the acceleration is large enough and the direction is downward, an inertia force of downward movement is generated, which causes the mass block 12 to displace downward, thereby causing a capacitance change, at this time, the capacitance of the upper side decreases, the capacitance of the lower side increases, the detection circuit module 20 detects the magnitudes of the first detection capacitor C1 and the second detection capacitor C2 and calculates a differential capacitance value, and simultaneously converts the differential capacitance value into a voltage value to be output to the feedback control circuit module 30, the feedback control circuit module 30 controls the driving voltage applied to the first driving capacitor C3 and the second driving capacitor C4 according to the voltage value, when the output of the detection circuit module 20 reaches a preset first capacitance threshold value, as shown in fig. 3, the first switch S1 is switched from the first contact B to the second contact a, the second switch S2 is switched from the first contact C to the second contact D, the voltage feedback control circuit 60 is turned on, and the capacitance detection circuit 50 is turned off, the detection capacitor 14 connected into the MEMS sensitive structure 10 of the capacitor detection circuit 50 is connected into the voltage feedback control circuit 60, namely the voltage fed back to the first driving capacitor C3 at the upper side is increased by DeltaV, the voltage of the second driving capacitor C4 at the lower side is decreased by DeltaV, and meanwhile, the first fixed capacitor C5 is connected into the capacitor detection circuit 50. The electrostatic force generated between driving capacitor 13 and mass 12 pulls mass 12 upward to counteract the downward inertial force generated by acceleration, causing it to return to its original position.
In this embodiment, the first fixed capacitor C5 is connected to the capacitance detection circuit 50 to be used as the temporary detection capacitor 13, the capacitance value of the first fixed capacitor C5 is equal to the capacitance value of the first detection capacitor C1 at the switching time, so that the differential mode voltage Δ V fed back by the feedback control circuit module 30 maintains the maximum value Δ Vmax, and under the action of the maximum driving voltage difference 2 × Δ Vmax in combination with the additional first fixed capacitor C5, a larger electrostatic force is generated to pull the mass 12 back to the initial position.
Further, in the process of adjusting the displacement of the mass block 12, the detection circuit module 20 continuously monitors the capacitance value of the detection capacitor 14, and when it is detected that the capacitance value of the detection capacitor 14 reaches the preset second capacitance threshold value, the first switch S1 is controlled to switch from the second contact a to the first contact B, the second switch S2 is controlled to switch from the second contact D to the first contact C, the capacitance detection circuit 50 is turned on, and the voltage feedback control circuit 60 is turned off at the same time, so that the detection capacitor 14 connected to the voltage feedback control circuit 60 in the MEMS sensitive structure 10 is switched to the capacitance detection circuit 50, that is, the MEMS closed-loop accelerometer 100 resumes the normal operation mode.
In the embodiment, the switch control module 40 switches the capacitance detection circuit 50 and the voltage feedback control circuit 60 in the MEMS closed-loop accelerometer 100, when the mass block 12 is displaced, the capacitance detection circuit 50 is switched to the voltage feedback control circuit 60, the detection capacitor 14 originally connected to the MEMS sensitive structure 10 of the capacitance detection circuit 50 is switched to the voltage feedback control circuit 60, the first fixed capacitor C5 is connected to the capacitance detection circuit 50, and the first fixed capacitor C5 is used as a temporary detection capacitor, so that the size of the driving capacitor is increased without changing parameters of the driving capacitor, thereby increasing the effect of feeding back electrostatic force, and improving the range and reliability of the MEMS closed-loop accelerometer 100.
In another embodiment, when the driving voltage fed back from the first loop 601 to the first driving capacitor C3 is opposite to the change direction of the voltage output by the capacitance detection loop 50, the first input terminal is connected to the first detection capacitor C1, the main body of the first switch S1 is connected to the second detection capacitor C2, the first contact B of the first switch S1 is disposed in the capacitance detection loop 50, the second contact a of the first switch S1 is disposed in the second loop 602, the main body of the second switch S2 is connected to the second input terminal, the first contact C of the second switch S2 is connected to the first contact B of the first switch S1, and the second contact D of the second switch S2 is connected to the first fixed capacitor C5.
The working process of this embodiment is similar to that of the above embodiment, and is not described in detail here.
In yet another practical embodiment, switch control module 40 includes a second fixed capacitor (not shown) electrically connected to mass 12, a third switch (not shown) connected to both capacitance detection circuit 50 and voltage feedback control circuit 60, and a fourth switch (not shown) connected to both the second fixed capacitor and capacitance detection circuit 50.
Further, a main body of the first switch S1 is connected to the first detection capacitor C1, a first contact B of the first switch S1 is disposed in the capacitance detection circuit 50, a second contact a of the first switch S1 is disposed in the first circuit 601, a main body of the second switch S2 is connected to the first input terminal, a first contact C of the second switch S2 is connected to the first contact B of the first switch S1, and a second contact D of the second switch S2 is connected to the first fixed capacitor C5; the body of the third switch is connected to the second detection capacitor, the first contact of the third switch is arranged in the capacitor detection circuit 50, the second contact of the third switch is arranged in the second circuit 602, the body of the fourth switch is connected to the second input terminal, the first contact of the fourth switch is connected to the first contact of the third switch, and the second contact of the fourth switch is connected to the second fixed capacitor. In this embodiment, the first fixed capacitor C5 and/or the second fixed capacitor can be connected to the capacitor detection circuit 50, the specific number of the connected capacitors needs to be determined according to a specific scenario, and the control manners of the first switch S1, the second switch S2, the third switch and the fourth switch are similar to those of the above embodiments and are not described herein again.
The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above examples only express preferred embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A MEMS closed-loop accelerometer, comprising:
the MEMS sensitive structure comprises a mass block, a driving capacitor and a detection capacitor, wherein the driving capacitor is connected with the mass block and used for driving the mass block to displace through electrostatic force, and the detection capacitor is connected with the mass block and used for detecting the displacement of the mass block;
the detection circuit module is used for converting a capacitance signal of the detection capacitor into a voltage signal;
the feedback control circuit module is connected with the detection circuit module and is used for controlling the driving voltage loaded to the driving capacitor according to the output of the detection circuit module; a capacitance detection loop is formed between the detection capacitor and the detection circuit module, and a voltage feedback control loop is formed between the driving capacitor, the detection circuit module and the feedback control circuit module; and
the switch control module is used for switching the capacitance detection loop and the voltage feedback control loop and comprises a first fixed capacitor, a first switch and a second switch, wherein the first switch is connected with the capacitance detection loop and the voltage feedback control loop, and the second switch is connected with the first fixed capacitor and the capacitance detection loop.
2. The MEMS closed-loop accelerometer of claim 1, wherein the driving capacitors comprise a first driving capacitor located on one side of the proof mass and a second driving capacitor located on an opposite side of the first driving capacitor, and the sensing capacitors comprise a first sensing capacitor located on a same side as the first driving capacitor or the second driving capacitor and a second sensing capacitor located on an opposite side of the first sensing capacitor.
3. The MEMS closed-loop accelerometer of claim 2, wherein the voltage feedback control loop comprises a first loop for controlling the drive voltage applied to the first drive capacitance and a second loop for controlling the drive voltage applied to the second drive capacitance.
4. The MEMS closed-loop accelerometer of claim 3, wherein the driving voltage fed back to the corresponding driving capacitor in one of the first loop and the second loop is in accordance with the direction of change of the voltage output by the capacitance detection loop; the other remaining loop feeds back the driving voltage of the corresponding driving capacitor, and the change direction of the voltage output by the capacitor detection loop is opposite to that of the voltage output by the capacitor detection loop.
5. The MEMS closed-loop accelerometer of claim 4, wherein the detection circuit module comprises a first input for detecting the first detection capacitance and a second input for detecting the second detection capacitance, when the driving voltage fed back to the corresponding driving capacitor by the second loop is opposite to the change direction of the voltage output by the capacitor detection loop, the second input end is connected with the second detection capacitor, the main body of the first switch is connected with the first detection capacitor, a first contact of the first switch is arranged in the capacitance detection loop, a second contact of the first switch is arranged in the first loop, the main body of the second switch is connected with the first input end, the first contact of the second switch is connected with the first contact of the first switch, and the second contact of the second switch is connected with the first fixed capacitor.
6. The MEMS closed-loop accelerometer of claim 4, wherein the detection circuit module comprises a first input for detecting the first detection capacitance and a second input for detecting the second detection capacitance, when the driving voltage fed back to the corresponding driving capacitor by the first loop is opposite to the change direction of the voltage output by the capacitor detection loop, the first input end is connected with the first detection capacitor, the main body of the first switch is connected with the second detection capacitor, the first contact of the first switch is arranged in the capacitance detection loop, the second contact of the first switch is arranged in the second loop, the main body of the second switch is connected with the second input end, the first contact of the second switch is connected with the first contact of the first switch, and the second contact of the second switch is connected with the first fixed capacitor.
7. The MEMS closed-loop accelerometer of claim 1, wherein the switch control module comprises a second fixed capacitor electrically connected to the mass, a third switch connected to both the capacitance detection loop and the voltage feedback control loop, and a fourth switch connected to both the second fixed capacitor and the capacitance detection loop.
8. The MEMS closed-loop accelerometer of claim 7, wherein the detection circuit module comprises a first input terminal for detecting the first detection capacitor and a second input terminal for detecting the second detection capacitor, the body of the first switch is connected to the first detection capacitor, the first contact of the first switch is disposed in the capacitance detection loop, the second contact of the first switch is disposed in the first loop, the body of the second switch is connected to the first input terminal, the first contact of the second switch is connected to the first contact of the first switch, and the second contact of the second switch is connected to the first fixed capacitor; the main body of the third switch is connected with the second detection capacitor, the first contact of the third switch is arranged in the capacitor detection loop, the second contact of the third switch is arranged in the second loop, the main body of the fourth switch is connected with the second input end, the first contact of the fourth switch is connected with the first contact of the third switch, and the second contact of the fourth switch is connected with the second fixed capacitor.
9. A control method applied to the MEMS closed-loop accelerometer of claims 1-8, the control method comprising:
monitoring the capacitance value of a detection capacitor of the MEMS sensitive structure in real time through a detection circuit module;
when the capacitance value is monitored to reach a preset first capacitance threshold value, a first switch and a second switch are controlled to switch a detection capacitor in an MEMS sensitive structure connected to the capacitance detection circuit into a voltage feedback control circuit, and a first fixed capacitor is connected to the capacitance detection circuit.
10. The control method according to claim 9, characterized by further comprising:
continuously monitoring the capacitance value of a detection capacitor of the MEMS sensitive structure through the detection circuit module;
and when the capacitance value is monitored to reach a preset second capacitance threshold value, controlling the first switch and the second switch to switch a detection capacitor connected into the voltage feedback control loop in the MEMS sensitive structure into the capacitance detection loop.
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| CN117490732A (en) * | 2022-07-25 | 2024-02-02 | 准懋(杭州)科技有限公司 | MEMS device |
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