MEMS sensor

Abstract

The application provides a MEMS sensor, which comprises a first driving capacitor and a second driving capacitor; a driver comprising a first driving unit, a second driving unit and a multiplexer. During a starting period of the resonator, the multiplexer outputs a first opposite-wave driving signal opposite in phase to the first driving unit output; during normal operation of the resonator, the multiplexer outputs a second opposite-wave driving signal opposite in phase to the second driving unit output; and the opposite-wave driving signal output by the multiplexer is coupled to the second connection end of the first driving capacitor and the second driving capacitor respectively. The high level of the first opposite-wave driving signal is higher than that of the second opposite-wave driving signal. In this way, the starting time of the MEMS sensor can be reduced.

Description

[Technical Field]

[0001] This invention relates to the field of sensors, and more particularly to a fast-start MEMS (Micro-Electro-Mechanical System) sensor. [Background Technology]

[0002] In MEMS gyroscopes or other resonator-based MEMS sensors, the resonator's resonance serves as the reference for the entire system. However, the startup time of existing MEMS sensor resonators from a stationary state to a stable simple harmonic motion state with the amplitude reaching the desired value is typically 100 milliseconds, which is too slow for advanced applications in portable settings and reduces overall power efficiency.

[0003] Therefore, there is an urgent need to propose a new technical solution to address the above problems. [Summary of the Invention]

[0004] One of the objectives of this invention is to provide a fast-start MEMS sensor that can significantly shorten the startup time of MEMS sensors.

[0005] To achieve the above objectives, according to one aspect of the present invention, a MEMS sensor is provided, comprising: a resonator including a first driving capacitor and a second driving capacitor, wherein a first connection terminal of the first driving capacitor and a first connection terminal of the second driving capacitor are coupled to a predetermined DC driving voltage; a driver including a first driving unit, a second driving unit, and a multiplexer, wherein the first driving unit outputs a first square wave driving signal with opposite phase, the second driving unit outputs a second square wave driving signal with opposite phase, the high level of the first square wave driving signal is higher than the high level of the second square wave driving signal, the multiplexer selects either the first square wave driving signal or the second square wave driving signal as its output according to a selection control signal, the square wave driving signal output by the multiplexer is respectively coupled to a second connection terminal of the first driving capacitor and a second connection terminal of the second driving capacitor, wherein during the resonator startup period, the selection control signal is configured to a first logic level, causing the multiplexer to output the first square wave driving signal, and during the resonator normal operation, the selection control signal is configured to a second logic level, causing the multiplexer to output the second square wave driving signal.

[0006] Compared with the prior art, the present invention drives the resonator of the MEMS sensor during startup using a first square wave drive signal with a higher high level, and drives the resonator of the MEMS sensor during normal operation using a second square wave drive signal with a lower high level, which can greatly shorten the startup time. [Attached Image Description]

[0007] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0008] Figure 1 This is a partial structural diagram of the MEMS sensor in one embodiment of the present invention;

[0009] Figure 2 for Figure 1 A schematic diagram of the structure of the driver in one embodiment;

[0010] Figure 3 for Figure 1 A schematic diagram of the resonator and driving detection capacitor bank in one embodiment;

[0011] Figure 4 An RLC simulation model of the resonator of a MEMS sensor;

[0012] Figure 5 To drive using the first and second square wave drive signals Figure 4 The simulation results of the RLC model are shown.

Detailed Implementation Methods

[0013] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0014] The term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the invention. The phrase "in one embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that excludes other embodiments. Unless otherwise specified, the terms "connected," "linked," and "connected" used herein to indicate electrical connection refer to direct or indirect electrical connection.

[0015] In this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," "coupled," etc., should be interpreted broadly; for example, they can refer to direct connection or indirect connection through an intermediate medium, which can be electronic components, functional circuits, etc. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances. In this document, MEMS gyroscope or MEMS sensor refers to MEMS-based gyroscopes and sensors.

[0016] In existing solutions, the startup time is the time required for the MEMS sensor's resonator to begin resonating to its desired mechanical displacement amplitude, which is set by a control loop that locks the frequency and amplitude via electrostatic actuation and sensing.

[0017] To achieve lower power consumption, the resonator of a MEMS sensor obtains the maximum mechanical displacement amplitude by actuating with minimum amplitude when in a resonant steady state (or a simple harmonic motion state where the amplitude reaches the desired amplitude). However, during the initial startup, the startup time can be reduced by increasing the actuation amplitude that drives the MEMS sensor.

[0018] Figure 1 This is a partial structural schematic diagram of the MEMS sensor 100 in one embodiment of the present invention.

[0019] Figure 2 for Figure 1 The diagram shows the structure of the driver DR in one embodiment. The MEMS sensor 100 can be a MEMS gyroscope or other resonator-based MEMS sensors employing correlation principles.

[0020] like Figure 1 As shown, the MEMS sensor 100 includes a resonator 110 and a driver (DR) 120. The resonator 110 includes a first driving capacitor D_p and a second driving capacitor D_n, wherein a first connection terminal of the first driving capacitor D_p and a first connection terminal of the second driving capacitor D_n are coupled to a predetermined DC driving voltage V. PM .like Figure 2As shown, the driver 120 includes a first driving unit D1, a second driving unit D2, and a multiplexer MUX. The first driving unit D1 outputs first square wave driving signals S1_1 and S1_2 with opposite phases. The second driving unit D2 outputs second square wave driving signals S2_1 and S2_2 with opposite phases. The high level of the first square wave driving signals S1_1 and S1_2 is higher than the high level of the second square wave driving signals S2_1 and S2_2. For example, the high level of the first square wave driving signals S1_1 and S1_2 can be 4V, while the high level of the second square wave driving signals S2_1 and S2_2 can be 2V. Opposite phases of the square wave driving signals mean that when one square wave driving signal is high, the other square wave driving signal is low, and when one square wave driving signal is low, the other square wave driving signal is high, with a phase difference of 180 degrees. The multiplexer MUX selects either the first square wave drive signal S1_1 and S1_2 or the second square wave drive signal S2_1 and S2_2 as output according to the selection control signal ST. The square wave drive signal output by the multiplexer MUX is respectively coupled to the second connection terminal of the first drive capacitor D_p and the second connection terminal of the second drive capacitor D_n.

[0021] In this invention, during the startup period of the resonator of the MEMS sensor, the selection control signal ST is configured to a first logic level, causing the multiplexer MUX to output a first square wave drive signal. This higher-level square wave drive signal is used to start the resonator 110, thereby accelerating the startup time. The startup time can be the time required for the resonator of the MEMS sensor to go from a static state to a simple harmonic motion state with an amplitude reaching the desired value. During normal operation of the resonator, the selection control signal ST is configured to a second logic level, causing the multiplexer MUX to output a second square wave drive signal.

[0022] Figure 3 for Figure 1 A schematic diagram of the resonator and driving detection capacitor bank in one embodiment is shown. Figure 3 As shown, the first driving capacitor D_p and the second driving capacitor D_n include a first driving capacitor electrode 111, a second driving capacitor electrode 112, and a movable mass block 113 located between the first driving capacitor electrode 111 and the second driving capacitor electrode 112. The movable mass block 113 serves as the first connection terminal of the first driving capacitor D_p and the first connection terminal of the second driving capacitor D_n, and is connected to a predetermined DC driving voltage V. PMCoupling. The first driving capacitor electrode 111 serves as the second connection terminal of the first driving capacitor D_p, and the second driving capacitor electrode 112 serves as the second connection terminal of the second driving capacitor D_n. Under the drive of a square wave driving signal output by the multiplexer MUX, the movable mass block 113 performs simple harmonic motion. For detailed operating procedures and principles of the resonator 110, please refer to existing literature, which will not be elaborated here.

[0023] A higher level of the square wave drive signal during startup means that the resonator of the MEMS sensor can obtain a higher driving force. In one embodiment, the driving force α on the movable mass block 113 is:

[0024]

[0025] Where V S It represents the voltage difference between the high and low levels of the square wave drive signal.

[0026] For example, if V PM 25V, V S If V is 2V, then α is 23. PM 25V, V S If V is 4V, then α is 42. As shown in the formula above, when V S When the power is doubled, the driving force is almost doubled.

[0027] Figure 4 This is an RLC simulation model of the resonator of a MEMS sensor. The RLC simulation model is used to simulate the state of the first driving capacitor D_p and the second driving capacitor D_n under a square wave driving signal. In the example, V... PM With a voltage of 24V, and square wave drive signals S_1 and S_2 at a high level of 2V or 4V and a frequency of 26.48kHz, observe the input current i over time. in,p i in,n . Figure 5 To drive using the first and second square wave drive signals Figure 4 The simulation results of the RLC model are shown. Where S2 is the input current i when driven by a square wave drive signal with a high level of 4V. in,p i in,n The waveform diagram shows that S1 is the input current i when driven by a square wave drive signal with a high level of 2V. in,p i in,n A waveform diagram. From Figure 5 As can be seen, the slope of the differential current entering the RLC model of the MEMS (resonator) doubles during startup, which in turn reduces startup time.

[0028] like Figure 2As shown, the first driving unit D1 generates first square wave driving signals S1_1 and S1_2 based on a first predetermined voltage V1. The high level of the first square wave driving signals S1_1 and S1_2 is the first predetermined voltage V1, which remains constant during the startup of the resonator of the MEMS sensor. The first predetermined voltage V1 can be a voltage value such as 4V or 5V. The second driving unit D2 is based on an analog automatic gain control signal V... AGC A second square wave drive signal is generated. The low level of each square wave drive signal can be zero.

[0029] In one example, the first driving unit D1 may include a switch combination whose switching period is determined according to the driving clock signal clk_gyro. In the first phase of a switching cycle, a first predetermined voltage V1 is connected to its first output terminal, and a zero level is connected to its second output terminal. In the second phase of a switching cycle, the first predetermined voltage V1 is connected to its second output terminal, and a zero level is connected to its first output terminal. Thus, through the continuous repetition of each switching cycle, the first driving unit D1 can generate first square wave driving signals S1_1 and S1_2 with opposite phases, where the high level is the first predetermined voltage V1. Following the same principle, the second driving unit D2 can also generate second square wave driving signals S2_1 and S2_2 with opposite phases.

[0030] See again Figure 1 As shown, the MEMS sensor further includes: a power supply circuit CP, a drive detection capacitor bank 130, a drive charge amplifier DCSA, a digital processing circuit 140, a drive analog-to-digital converter DADC, a comparator Comp, a phase-locked loop PLL, and an automatic gain control digital-to-analog converter AGC_DAC. The digital processing circuit 140 includes an automatic gain control module AGC.

[0031] The power supply circuit CP output terminal provides the predetermined DC drive voltage V. PM .

[0032] The drive detection capacitor group 130 includes a first drive detection capacitor D_sense_p and a second drive detection capacitor D_sense_n. For example... Figure 3 As shown, the first drive detection capacitor D_sense_p and the second drive detection capacitor D_sense_n include a first drive detection capacitor electrode 131, a first drive detection capacitor electrode 132, and a movable mass block 113 located between the first drive detection capacitor electrode 131 and the second drive detection capacitor electrode 132. The movable mass block serves as the first connection terminal between the first drive detection capacitor D_sense_p and the second drive detection capacitor D_sense_n and the predetermined DC drive voltage V. PMCoupling. The first driving detection capacitor electrode 131 serves as the second connection terminal of the first driving detection capacitor D_sense_p, and the second driving detection capacitor electrode 132 serves as the second connection terminal of the second driving detection capacitor D_sense_n.

[0033] The first input terminal of the drive charge amplifier DCSA is connected to the second connection terminal of the first drive detection capacitor D_sense_p, and its second input terminal is connected to the second connection terminal of the second drive detection capacitor D_sense_n.

[0034] The first input terminal of the driving analog-to-digital converter (DADC) is connected to the first output terminal of the driving charge amplifier (DCSA), its second input terminal is connected to the second output terminal of the driving charge amplifier (DCSA), and its output terminal is connected to the automatic gain control (AGC) module of the digital processing circuit 140. The first input terminal of the comparator (Comp) is connected to the first output terminal of the driving charge amplifier (DCSA), and its second input terminal is connected to the second output terminal of the driving charge amplifier (DCSA).

[0035] The reference input terminal ref_pll of the phase-locked loop (PLL) is connected to the output terminal of the comparator Comp. The comparator Comp provides a reference clock to the PLL. The output terminal of the PLL is connected to the digital processing circuit 140 and provides the PLL clock pll_clk to the digital processing circuit 140.

[0036] The digital processing circuit 140 generates a feedback clock pll_fb_clk that is in phase and frequency with the reference clock based on the phase-locked loop clock pll_clk, and provides the feedback clock pll_fb_clk to the feedback input terminal fb_pll of the phase-locked loop PLL. The digital processing circuit 140 shifts the feedback clock by -90 degrees and provides it as a drive clock signal clk_gyro to the driver 120 through the drive clock port.

[0037] The driving analog-to-digital converter AGC_DAC converts the voltage signal output by the driving charge amplifier DCSA into a digital voltage signal. The automatic gain control module AGC performs low-pass filtering on the digital voltage signal, and then provides a digital gain control signal DAC_da to control the driving amplitude through a PID controller. The digital gain control signal DAC_da is converted into an analog gain control signal VAGC by the automatic gain control digital-to-analog converter AGC_DAC and provided to the driver 120.

[0038] During normal operation, the second drive unit D2 of the driver 120 generates a second square wave drive signal based on the drive clock signal clk_gyro and the analog gain control signal VAGC, wherein the frequency of the second square wave drive signal is determined based on the drive clock signal clk_gyro. During startup, the first drive unit D1 of the driver 120 generates a first square wave drive signal S1_1 and S1_2 based on a first predetermined voltage V1, and determines the frequency of the first square wave drive signal S1_1 and S1_2 based on the drive clock signal clk_gyro.

[0039] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0040] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications and variations to the above embodiments within the scope of the present invention.

Claims

1. A MEMS sensor, characterized in that, It includes: A resonator includes a first driving capacitor and a second driving capacitor, wherein a first connection terminal of the first driving capacitor and a first connection terminal of the second driving capacitor are coupled to a predetermined DC driving voltage. The driver includes a first driving unit, a second driving unit, and a multiplexer. The first driving unit outputs a first square wave driving signal with opposite phase, and the second driving unit outputs a second square wave driving signal with opposite phase. The high level of the first square wave driving signal is higher than the high level of the second square wave driving signal. The multiplexer selects either the first square wave driving signal or the second square wave driving signal as its output according to a selection control signal. The square wave driving signal output by the multiplexer is coupled to the second connection terminal of a first driving capacitor and the second connection terminal of a second driving capacitor, respectively. The first and second driving capacitors include first driving capacitor electrodes, second driving capacitor electrodes, and a movable mass block located between the first driving capacitor electrodes and the second driving capacitor electrodes. The movable mass block is coupled to a predetermined DC driving voltage as the first connection terminal of the first driving capacitor and the second driving capacitor, respectively. The first driving capacitor electrode is the second connection terminal of the first driving capacitor, and the second driving capacitor electrode is the second connection terminal of the second driving capacitor. Under the drive of the square wave driving signal output by the multiplexer, the movable mass block performs simple harmonic motion. The power supply circuit provides the predetermined DC drive voltage at its output terminal; A drive detection capacitor bank, comprising a first drive detection capacitor and a second drive detection capacitor, wherein the movable mass block serves as a first connection terminal of the first drive detection capacitor and the second drive detection capacitor and is coupled to a predetermined DC drive voltage. A driving charge amplifier, wherein its first input terminal is connected to the second connection terminal of the first driving detection capacitor, and its second input terminal is connected to the second connection terminal of the second driving detection capacitor; Digital processing circuitry, including an automatic gain control module; The driver analog-to-digital converter has its first input terminal connected to the first output terminal of the driver charge amplifier, its second input terminal connected to the second output terminal of the driver charge amplifier, and its output terminal connected to the automatic gain control module of the digital processing circuit. A comparator, the first input terminal of which is connected to the first output terminal of the driving charge amplifier, and the second input terminal of which is connected to the second output terminal of the driving charge amplifier; A phase-locked loop (PLL) has its reference input connected to the output of the comparator, the comparator providing a reference clock to the PLL, and the output of the PLL connected to the digital processing circuit and providing the digital processing circuit with the PLL clock. Automatic gain control digital-to-analog converter; The digital processing circuit generates a feedback clock that is in phase and frequency with the reference clock based on the phase-locked loop clock, and provides the feedback clock to the feedback input terminal of the phase-locked loop. The digital processing circuit then shifts the feedback clock by -90 degrees and provides it as a drive clock signal to the driver through the drive clock port. The driving analog-to-digital converter converts the voltage signal output by the driving charge amplifier into a digital voltage signal. The automatic gain control module performs low-pass filtering on the digital voltage signal and then provides a digital gain control signal to control the driving amplitude through a PID controller. This digital gain control signal is converted into an analog gain control signal by the automatic gain control digital-to-analog converter and provided to the driver. During normal operation, the driver generates a second square wave drive signal based on the drive clock signal and the analog gain control signal; The selection control signal is configured to a first logic level during the resonator startup period, causing the multiplexer to output a first square wave drive signal, and the selection control signal is configured to a second logic level during the resonator normal operation, causing the multiplexer to output a second square wave drive signal.

2. The MEMS sensor according to claim 1, characterized in that, The first driving unit generates a first square wave driving signal based on a first predetermined voltage. The high level of the first square wave driving signal is the first predetermined voltage, which remains unchanged during the resonator startup period. The second drive unit generates a second square wave drive signal based on the analog automatic gain control signal.

3. The MEMS sensor according to claim 2, characterized in that, The low level of each square wave drive signal is zero level.

4. The MEMS sensor according to claim 1, characterized in that, The MEMS sensor is a MEMS gyroscope.

Images