Detection circuit

Abstract

The invention provides a detection circuit, which comprises a function selection module and a detection module, and is characterized in that the function selection module is connected with the detection module; the function selection module is used for generating a function instruction of the detection module based on a selection instruction of a user, and the function instruction comprises a function instruction for detecting acceleration or a function instruction for detecting inherent frequency parameters; and the detection module is used for determining a detection result corresponding to the function instruction based on the function instruction. By using the detection circuit provided by the invention, the acceleration and the inherent frequency parameter of the accelerometer can be detected, and the self-detection of the accelerometer is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of accelerometers, and in particular to a detection circuit. Background Art

[0002] The natural frequency of a Micro-Electro-Mechanical Systems Accelerometer (MEMS) is a key parameter in its design and application. The natural frequency not only determines the measurement range and sensitivity of the accelerometer, but also affects the stability and reliability of the accelerometer.

[0003] However, the general capacitive MEMS structure is different from the circuit structure of the accelerometer for measuring acceleration, and a separate circuit needs to be added to detect the natural frequency parameters. Therefore, for an accelerometer detection circuit, it is not possible to detect both the natural frequency and the acceleration signal. Summary of the invention

[0004] The present invention provides a detection circuit to solve the defect in the prior art that an additional circuit needs to be added to the accelerometer to measure the natural frequency parameters of the accelerometer, and realizes the function of detecting both acceleration and natural frequency using the same detection circuit.

[0005] The present invention provides a detection circuit, comprising: a function selection module and a detection module, wherein: The function selection module is connected with the detection module; A function selection module, used for generating a function instruction of the detection module based on a user's selection instruction, wherein the function instruction includes at least one of the following: a function instruction for detecting acceleration or a function instruction for detecting a natural frequency parameter; The detection module is used to determine the detection result corresponding to the functional instruction based on the functional instruction.

[0006] According to a detection circuit provided by the present invention, the detection module includes: a generating circuit, a watch core structure and a capacitance detection circuit, wherein: the generating circuit is respectively connected to the function selection module, the watch core structure and the capacitance detection circuit, the watch core structure is connected to the capacitance detection circuit, and the function selection module is connected to the capacitance detection circuit; the generating circuit is used to generate two complementary carrier signals corresponding to the function instruction based on the function instruction; the watch core structure is used to modulate the capacitance change signal generated by the watch core structure based on the two carrier signals to obtain a charge signal; the capacitance detection circuit is used to convert the charge signal into a target voltage signal and send it to the generating circuit; the generating circuit is also used to determine the detection result corresponding to the function instruction based on the target voltage signal.

[0007] According to a detection circuit provided by the present invention, two carrier signals include a positive carrier signal and a negative carrier signal, and the core structure includes: a first capacitor plate, a second capacitor plate and an intermediate capacitor plate, wherein: a generating circuit is respectively connected to the first capacitor plate and the second capacitor plate, the intermediate capacitor plate is connected to the capacitor detection circuit, and the intermediate capacitor plate is located between the first capacitor plate and the second capacitor plate; the first capacitor plate is used to receive the positive carrier signal, and obtain a first voltage signal based on the positive carrier signal; the second capacitor plate is used to receive the negative carrier signal, and obtain a second voltage signal based on the negative carrier signal; the intermediate capacitor plate is used to determine the charge signal based on the first voltage signal and the second voltage signal.

[0008] According to a detection circuit provided by the present invention, a function selection module includes: a first voltage unit and a second voltage unit, wherein: the first voltage unit is connected to a generating circuit, and the second voltage unit is connected to a capacitor detection circuit; the first voltage unit is used to load a first voltage to a first capacitor plate and a second capacitor plate; the second voltage unit is used to load a second voltage to an intermediate capacitor plate; the core structure is also used to determine a target voltage signal based on a positive carrier signal, a negative carrier signal, a first voltage, and a second voltage.

[0009] According to a detection circuit provided by the present invention, the functional instruction is a functional instruction for detecting natural frequency parameters, and the first voltage and the second voltage are different; the generating circuit is also used to generate at least two groups of two-way carrier signals with gradually increasing frequencies based on the functional instruction for detecting the natural frequency parameters; the minimum frequency corresponding to the two-way carrier signals is less than the ideal natural frequency parameter, and the maximum frequency corresponding to the two-way carrier signals is greater than the ideal natural frequency parameter; the watch core structure is also used to determine the capacitance change signal based on the first voltage and the second voltage; based on the at least two groups of two-way carrier signals that are continuously increasing, the capacitance change signal is modulated to obtain at least two charge signals; the capacitance detection circuit is also used to convert each charge signal into a corresponding target voltage signal and send it to the generating circuit; the generating circuit is also used to demodulate each target voltage signal to obtain a signal waveform related to the carrier frequency, and determine the natural frequency parameter based on the signal waveform, wherein the natural frequency parameter is the detection result.

[0010] According to a detection circuit provided by the present invention, the frequency of each demodulation signal used by the generation circuit when demodulating each target voltage signal is twice the frequency of the corresponding positive carrier signal or negative carrier signal.

[0011] According to a detection circuit provided by the present invention, the functional instruction is a functional instruction for detecting acceleration, the first voltage and the second voltage are the same, and the generating circuit is also used to generate two carrier signals based on the functional instruction for detecting acceleration; the watch core structure is also used to determine the capacitance change signal based on the external force corresponding to the acceleration; based on the two carrier signals, the capacitance change signal is modulated to obtain a charge signal; the capacitance detection circuit is used to convert the charge signal into a target voltage signal and send it to the generating circuit; the generating circuit is also used to demodulate the target voltage signal to obtain acceleration, wherein the acceleration is the detection result.

[0012] According to a detection circuit provided by the present invention, the generating circuit includes: a main control chip and a signal processing circuit, wherein: the main control chip is respectively connected to a function selection module and a signal processing circuit, and the signal processing circuit is connected to a watch movement structure; the main control chip is used to generate an initial carrier signal corresponding to a function instruction based on the function instruction; the signal processing circuit is used to perform signal processing on the initial carrier signal to obtain two carrier signals.

[0013] According to a detection circuit provided by the present invention, two carrier signals include a positive carrier signal and a negative carrier signal, and the signal processing circuit includes a bandpass filter circuit and a reverse circuit, wherein: the bandpass filter circuit is respectively connected to the main control chip, the watch core structure and the reverse circuit, and the reverse circuit is connected to the watch core structure; the bandpass filter circuit is used to amplify the amplitude of the initial carrier signal to obtain the positive carrier signal; the reverse circuit is used to generate a negative carrier signal based on the positive carrier signal.

[0014] According to a detection circuit provided by the present invention, the main control chip includes: an analog-to-digital converter and a demodulation unit, wherein: the analog-to-digital converter is respectively connected to the capacitance detection circuit and the demodulation unit; the analog-to-digital converter is used to convert the analog signal of the target voltage signal into a digital signal; the demodulation unit is also used to demodulate the digital signal to obtain a detection result.

[0015] The detection circuit provided by the present invention utilizes a function selection module to generate a function instruction of the detection module according to a user's selection instruction; after receiving the function instruction, the detection module determines the detection result corresponding to the function instruction according to the function instruction. Among them, the function instruction includes: a function instruction for detecting acceleration or a function instruction for detecting natural frequency parameters. In this way, by utilizing the detection circuit, the same circuit can detect both acceleration and natural frequency parameters, thereby ensuring the compatibility of the detection circuit and simplifying the detection circuit. At the same time, the long-term monitoring of the natural frequency of the accelerometer during the use of the product is realized. When the natural frequency deviates, the in-situ calibration of the accelerometer can be realized in time according to the natural frequency to prevent problems such as spring aging from affecting the performance of the accelerometer. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 It is a schematic diagram of a MEMS accelerometer structure provided by the prior art.

[0018] Figure 2 The present invention is a schematic diagram of the working principle of a MEMS accelerometer provided by the prior art.

[0019] Figure 3 This is one of the connection diagrams of the detection circuit provided by the present invention.

[0020] Figure 4 This is the second connection schematic diagram of the detection circuit provided by the present invention.

[0021] Figure 5 This is the third connection schematic diagram of the detection circuit provided by the present invention.

[0022] Figure 6 It is a schematic diagram of the comb-tooth design of the core structure of the MEMS accelerometer provided by the present invention.

[0023] Figure 7 This is the fourth connection diagram of the detection circuit provided by the present invention.

[0024] Figure 8 It is a schematic diagram of a voltage loading circuit provided by the present invention.

[0025] Fig. 9 It is a schematic diagram of a half-frequency signal and a full-frequency signal provided by an embodiment of the present invention.

[0026] Fig.10 This is the fifth connection diagram of the detection circuit provided by the present invention.

[0027] Fig.11 This is the sixth connection diagram of the detection circuit provided by the present invention.

[0028] Fig.12 This is the seventh connection diagram of the detection circuit provided by the present invention.

[0029] Reference numerals: 100: MEMS accelerometer structure; 101: anchor point; 102: U-shaped elastic beam; 103: fixed comb teeth; 104: movable comb teeth; 105: mass frame; 300: detection circuit; 310: function selection module; 320: detection module; 321: generation circuit; 322: movement structure; 323: capacitance detection circuit; 3221: first capacitor plate; 3222: second capacitor plate; 3223: middle capacitor plate; 311: first voltage unit; 312: second voltage unit; 3211: main control chip; 3212: signal processing circuit; 32121: bandpass filter circuit; 32122: reverse circuit; 32111: analog to digital converter; 32112: demodulation unit; 601: movable capacitor plate; 602: fixed capacitor plate. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] MEMS accelerometers are sensors used to measure the acceleration of objects and are the basic core components of inertial navigation systems. According to different working principles, accelerometers can be divided into capacitive accelerometers, piezoelectric accelerometers, piezoresistive accelerometers, resonant accelerometers, and many other types. Among them, capacitive accelerometers are based on the principle that the change in relative position between the fixed substrate and the movable substrate produces a change in capacitance. The change in capacitance is proportional to the acceleration. By designing an acceleration detection circuit to convert the change in capacitance into a change in voltage, acceleration measurement can be achieved.

[0032] The natural frequency of MEMS accelerometers is a key parameter in their design and application. The natural frequency not only determines the measurement range and sensitivity of the accelerometer, but also affects the stability and reliability of the accelerometer. If the natural frequency of the accelerometer is the same or similar to the external vibration frequency, resonance may occur, causing damage to the accelerometer or performance degradation. After a period of use, the performance of the accelerometer may change due to factors such as environment, temperature, and wear. When the performance of the accelerometer changes, the test results may deviate from the actual results, resulting in the failure of inertial navigation and irreparable consequences.

[0033] The following is a brief description of the principle of the accelerometer.

[0034] Figure 1It is a schematic diagram of a MEMS accelerometer structure provided by the prior art, such as Figure 1 As shown, the MEMS accelerometer structure 100 includes: an anchor point 101, a U-shaped elastic beam 102, a fixed comb tooth 103, a movable comb tooth 104 and a mass frame 105. The movable comb teeth and the mass frame together constitute the sensitive mass of the accelerometer. When subjected to horizontal external acceleration, the sensitive mass will move in the horizontal direction, causing the relative area between the fixed comb teeth 103 and the movable comb teeth 104 to change, thereby generating a differential capacitance, and generating an output charge signal on the movable comb teeth. The charge signal is then converted into a voltage signal through a capacitance detection circuit, thereby realizing the measurement of acceleration.

[0035] Figure 2 This is a schematic diagram of the working principle of a MEMS accelerometer provided by the prior art, such as Figure 2 As shown, the digital-to-analog converter (DAC) module of the microcontroller unit chip 201 generates a carrier signal, which is filtered and amplified before being input to the differential structure comb 202. The differential structure comb 202 outputs a voltage signal corresponding to the acceleration, which is filtered and amplified before being input to the microcontroller unit chip 201. After the microcontroller unit chip 201 detects the filtered and amplified voltage signal, it performs synchronous demodulation and low-pass filtering and amplification on the signal to obtain a signal related to the acceleration and outputs it.

[0036] When extracting the natural frequency parameters of a general capacitive MEMS structure, it is necessary to load a driving signal with a gradually increasing frequency onto the movable comb teeth, and detect it at the fixed comb teeth, so that the signal related to the driving frequency can be collected. When the frequency gradually increases to the natural frequency, the system will detect the resonance peak, output the corresponding frequency, and complete the detection of the natural frequency. However, the detection principle and electrical signal connection method of this circuit are different from those of the accelerometer detection circuit. For a watch movement, it can only detect the natural frequency but not the acceleration signal.

[0037] Based on the above problems, the present invention provides a detection circuit. By utilizing the detection circuit, the same circuit can detect both acceleration and natural frequency parameters, thereby ensuring the compatibility of the detection circuit and simplifying the detection circuit. At the same time, long-term monitoring of the natural frequency of the accelerometer during the use of the product is achieved. When the natural frequency deviates, the accelerometer can be calibrated in situ in time according to the natural frequency to prevent problems such as spring aging from affecting the performance of the accelerometer.

[0038] Combine the following Figure 3-Figure 12 The detection circuit of the present invention is described. The detection circuit provided by the present invention can detect any acceleration and the natural frequency of any accelerometer, including but not limited to vehicle acceleration, human motion acceleration, bicycle acceleration, etc.

[0039] Figure 3 is one of the connection diagrams of the detection circuit provided by the present invention, such as Figure 3 As shown, the detection circuit 300 includes: a function selection module 310 and a detection module 320, wherein: The function selection module 310 is connected to the detection module 320; The function selection module 310 is used to generate a function instruction of the detection module based on the user's selection instruction, and the function instruction includes at least one of the following: a function instruction for detecting acceleration or a function instruction for detecting a natural frequency parameter; The detection module 320 is used to determine the detection result corresponding to the functional instruction based on the functional instruction.

[0040] Here, the natural frequency parameter refers to the natural frequency parameter of the accelerometer, which is usually related to the vibration system and refers to the free vibration frequency of the system without the action of external driving force. Among them, the greater the deviation of the actual natural frequency parameter of the accelerometer, the worse the performance of the accelerometer in measuring acceleration. Therefore, evaluating and calibrating the natural frequency before each use of the MEMS accelerometer is the key to ensuring the performance of the MEMS accelerometer.

[0041] Here, the user's selection instruction can be the user's operation instruction on the switch or the user's input instruction or instructions of different levels. For example, when the user closes the switch, it corresponds to the function instruction of detecting the natural frequency parameters, and when the user opens the switch, it corresponds to the function instruction of detecting acceleration; for another example, a high level corresponds to the function instruction of detecting the natural frequency parameters, and a low level corresponds to the function instruction of detecting acceleration.

[0042] Here, the function instruction generated by the function selection module 310 may be input to the detection module through an input / output (I / O) interface, network transmission, wireless transmission, etc.

[0043] It should be noted that although the detection of acceleration and the detection of natural frequency parameters can be realized by the same detection module, the detection of acceleration and the detection of natural frequency parameters use different programs. Therefore, the functional instructions are also used to select programs for realizing different functions. Among them, the programs of the two detection functions can be pre-embedded in the detection module by the staff, and the corresponding program is selected according to the functional instructions, so as to determine the corresponding detection result in combination with the circuit in the detection module.

[0044] Here, the detection result may be an acceleration or a natural frequency parameter.

[0045] In an embodiment of the present invention, a function selection module is used to generate a function instruction of a detection module according to a user's selection instruction; after receiving the function instruction, the detection module determines the detection result corresponding to the function instruction according to the function instruction. Among them, the function instruction includes: a function instruction for detecting acceleration or a function instruction for detecting natural frequency parameters. In this way, a detection circuit is used in the accelerometer to detect both acceleration and natural frequency parameters, thereby ensuring the compatibility of the detection circuit and realizing the self-test of the natural frequency parameters of the accelerometer. At the same time, the long-term monitoring of the natural frequency of the accelerometer during the use of the product is realized. When the natural frequency deviates, the in-situ calibration of the accelerometer can be realized in time according to the natural frequency to prevent problems such as spring aging from affecting the performance of the accelerometer.

[0046] further, Figure 4 This is the second connection diagram of the detection circuit provided by the present invention, such as Figure 4 As shown, the detection module 320 includes: a generation circuit 321, a watch movement structure 322 and a capacitance detection circuit 323, wherein: The generating circuit 321 is respectively connected to the function selection module 310, the watch core structure 322 and the capacitance detection circuit 323, the watch core structure 322 is connected to the capacitance detection circuit 323, and the function selection module 310 is connected to the capacitance detection circuit 323; The generating circuit 321 is used for generating two complementary carrier signals corresponding to the functional instruction based on the functional instruction; The watch core structure 322 is used to modulate the capacitance change signal generated by the watch core structure based on the two carrier signals to obtain a charge signal; The capacitance detection circuit 323 is used to convert the charge signal into the target voltage signal and send it to the generation circuit 321; The generating circuit 321 is further configured to determine a detection result corresponding to the functional instruction based on the target voltage signal.

[0047] Here, the two complementary carrier signals refer to two high-frequency complementary carrier signals with the same reference, amplitude and frequency, and a phase difference of 180°. The carrier signal can be a sine wave signal of any suitable frequency, and can form various types of modulation signals according to different modulation methods and application scenarios, such as amplitude modulation signals, frequency modulation signals, phase modulation signals, etc.

[0048] Here, the capacitance change generated by the movement structure is substantially the capacitance change caused by the change in the overlapping area or distance between the fixed comb teeth and the movable comb teeth in the movement structure. The charge signal may be the amount of charge.

[0049] It should be noted that the capacitance detection circuit is mainly used to amplify the weak charge signal output by the detection element such as the vibration sensor, and convert it into a voltage signal for subsequent processing. Its working principle is that when the sensor generates charge, these charges charge the feedback capacitor through a high impedance path, thereby generating a voltage across the capacitor. Due to the virtual short characteristic of the operational amplifier, the voltage at the inverting input is clamped at a level that is almost the reference voltage connected to the non-inverting input, so the output voltage is proportional to the input charge.

[0050] The capacitance detection circuit may be any suitable circuit, for example, an explosion-proof capacitance detection circuit, a precision capacitance detection circuit, or an integrated capacitance detection circuit.

[0051] The target voltage signal may be a voltage signal corresponding to acceleration, or a voltage signal of a natural frequency parameter.

[0052] Here, the method for determining the target voltage signal may be to modulate the capacitance change signal corresponding to the function instruction with two carrier signals, or to process the two carrier signals and then modulate the capacitance change signal corresponding to the function instruction.

[0053] Here, the detection result may be obtained by demodulating the target voltage signal, or by filtering the target voltage signal and then demodulating the filtered target voltage signal.

[0054] In an embodiment of the present invention, a generating circuit generates a carrier signal corresponding to a functional instruction according to a functional instruction, modulates the capacitance change generated by the watch core structure to obtain a charge signal, and utilizes a capacitance detection circuit to amplify the charge signal generated by the capacitance change of the sensor, and converts it into a target voltage signal. In this way, the generating circuit, the watch core structure and the capacitance detection circuit can be used to detect both acceleration and natural frequency parameters, thereby realizing self-test of the natural frequency parameters of the accelerometer. At the same time, the capacitance detection circuit will not introduce new noise in the process of amplifying the charge amount, and can detect weak signal changes, thereby improving the accuracy of the sensor in measuring acceleration or natural frequency parameters.

[0055] further, Figure 5 This is the third connection diagram of the detection circuit provided by the present invention, such as Figure 5 As shown, the two carrier signals include a positive carrier signal and a negative carrier signal, and the core structure 322 includes: a first capacitor plate 3221, a second capacitor plate 3222 and an intermediate capacitor plate 3223, wherein: The generating circuit 321 is connected to the first capacitor plate 3221 and the second capacitor plate 3222 respectively, the middle capacitor plate 3223 is connected to the capacitance detection circuit 323, and the middle capacitor plate 3223 is located between the first capacitor plate 3221 and the second capacitor plate 3222; The first capacitor plate 3221 is used to receive the positive carrier signal and obtain a first voltage signal based on the positive carrier signal; The second capacitor plate 3222 is used to receive the load wave signal and obtain a second voltage signal based on the load wave signal; The intermediate capacitor plate 3223 is used to determine the charge signal based on the first voltage signal and the second voltage signal.

[0056] It should be noted that the first capacitor plate can be understood as an input port formed by one or more capacitor upper plates in the watch core structure, and the main control chip is connected to the first capacitor plate, which is equivalent to being connected to multiple capacitor upper plates. Similarly, the second capacitor plate can be understood as an input port formed by one or more capacitor lower plates in the watch core structure, and the main control chip is connected to the second capacitor plate, which is equivalent to being connected to multiple capacitor lower plates. The intermediate capacitor plate can be understood as an output port formed by one or more capacitor intermediate plates in the watch core structure, and the capacitance detection circuit and the intermediate capacitor plate are equivalent to being connected to multiple intermediate capacitor plates.

[0057] It should be noted that the first voltage signal is substantially the potential difference between the first capacitor plate and the middle capacitor plate, and the second voltage signal is substantially the potential difference between the second capacitor plate and the middle capacitor plate.

[0058] For example, Figure 6 FIG. 1 is a schematic diagram of a comb-tooth design of a core structure of a MEMS accelerometer provided by the present invention, such as Figure 6 As shown, it includes a movable capacitor plate 601 and a fixed capacitor plate 602, wherein the movable capacitor plate 601 is a movable comb-tooth capacitor plate, and the fixed capacitor plate 602 is a fixed comb-tooth capacitor plate. When the accelerometer is working, two carrier signals with opposite phases are applied to the movable comb teeth respectively. When acceleration is generated, the relative area of ​​the two capacitor plates changes, thereby causing a charge change, and a signal is output through the fixed comb teeth. The signal is amplified and filtered, and the output voltage signal is converted into an acceleration signal. Here, the calculation of the comb-tooth capacitance can be as follows (1): (1)

[0059] in, is the dielectric constant, is the relative area of ​​the movable comb capacitor plate and the fixed comb capacitor plate, is the electrostatic force constant, is the distance between the two plates.

[0060] When acceleration is applied, the fixed comb capacitor plate moves to the right. At this time, the capacitance difference between the two plates is calculated as follows (2): (2)

[0061] Where x is the moving distance of the fixed comb capacitor plate, is the plate thickness.

[0062] From this, it can be seen that when the outside world senses acceleration, the mechanical structure first converts the acceleration signal into the linear movement distance of the sensitive mass block, and then converts it into the capacitance value △C of the differential capacitance change that is linearly related to it. The measurement of the external acceleration signal is achieved by measuring the change in △C.

[0063] According to formula (2), the relationship between the magnitude of the external acceleration signal and △C is expressed as follows: (3)

[0064] in, is the acceleration, and w is the natural angular frequency of the accelerometer.

[0065] In the embodiment of the present invention, the first capacitor plate, the second capacitor plate and the middle capacitor plate in the watch core structure are used to convert acceleration or natural frequency parameters into measurable electrical signals, thereby improving the measurement performance of the accelerometer for acceleration or natural parameter frequency.

[0066] further, Figure 7 FIG. 4 is a fourth connection diagram of the detection circuit provided by the present invention. Figure 7 As shown, the function selection module 310 includes: a first voltage unit 311 and a second voltage unit 312, wherein: The first voltage unit 311 is connected to the generating circuit 321, and the second voltage unit 312 is connected to the capacitance detecting circuit 323; The first voltage unit 311 is used to apply a first voltage to the first capacitor plate 3221 and the second capacitor plate 3222; The second voltage unit 312 is used to apply a second voltage to the middle capacitor plate 3223; The meter core structure 322 is further used to determine the target voltage signal based on the positive carrier signal, the negative carrier signal, the first voltage and the second voltage.

[0067] It should be noted that the voltages provided by the first voltage unit 311 and the second voltage unit 312 can be pre-set through a program. When the function instruction is a function instruction for detecting acceleration, the power supply mode set by the first program is used to control the first voltage unit and the second voltage unit to load voltages to the first capacitor plate 3221, the second capacitor plate 3222 and the middle capacitor plate 322 respectively; when the function instruction is a function instruction for detecting natural frequency parameters, the power supply mode set by the second program is used to control the first voltage unit and the second voltage unit to load voltages to the first capacitor plate 3221, the second capacitor plate 3222 and the middle capacitor plate 322 respectively.

[0068] Here, the first voltage and the second voltage are DC voltages.

[0069] Here, the meter core structure can be to obtain an initial signal based on two carrier signals, a first voltage and a second voltage, and then obtain a target voltage signal after a series of processing such as conversion and filtering of the initial signal; or it can be to directly obtain the target voltage signal based on two carrier signals, a first voltage and a second voltage.

[0070] It should be noted that, in addition to loading the sinusoidal signals Va with the same amplitude and 180 degrees phase difference on both ends of the movable comb teeth, and loading the first voltage on the first and second capacitor plates, the second voltage is loaded on the middle capacitor plate.

[0071] For example, Figure 8 Schematic diagram of the voltage loading circuit provided by the present invention, such as Figure 8 As shown, Va is the carrier signal, is a first voltage loaded on the first capacitor plate and the second capacitor plate, is the second voltage loaded on the middle capacitor plate. Here, according to the electrostatic force formula, it can be known that the capacitance change caused by the first voltage and the second voltage on the middle capacitor plate is The calculation of is as follows formula (4):

[0072] In an embodiment of the present invention, two detection functions are realized by loading a first voltage on the first capacitor plate and the second capacitor plate and loading a second voltage on the middle capacitor plate, thereby ensuring the compatibility of the detection circuit and realizing self-detection of the natural frequency parameters of the accelerometer.

[0073] In an embodiment of the present invention, the functional instruction is the functional instruction for detecting the natural frequency parameter, and the first voltage and the second voltage are different; The generating circuit 321 is further configured to generate at least two groups of the two carrier signals with gradually increasing frequencies based on the functional instruction for detecting the natural frequency parameter; the minimum frequency corresponding to the two carrier signals is less than the ideal natural frequency parameter, and the maximum frequency corresponding to the two carrier signals is greater than the ideal natural frequency parameter; The watch core structure 322 is further used to determine the capacitance change signal based on the first voltage and the second voltage; modulate the capacitance change signal based on the at least two groups of the two carrier signals that are increasing continuously to obtain at least two charge signals; The capacitance detection circuit 323 converts each of the charge signals into the corresponding target voltage signals and sends them to the generation circuit 321; The generating circuit 321 is further used to demodulate each of the target voltage signals to obtain a signal waveform related to the carrier frequency, and determine the natural frequency parameter based on the signal waveform, wherein the natural frequency parameter is the detection result.

[0074] Here, when the functional instruction is a functional instruction for detecting the natural frequency parameters, the main control chip selects to execute a program for detecting the natural frequency parameters to generate at least two two-channel carrier signals with gradually increasing frequencies.

[0075] It should be noted that when detecting the natural frequency parameters, the natural frequency parameters are often located at the peak of the output signal waveform related to the carrier frequency. Therefore, it is necessary to use multiple gradually increasing two-way carrier signals to output the signal waveform related to the carrier frequency. Thus, the natural frequency parameters are determined based on the peak value of the signal waveform related to the carrier frequency and the output frequency data.

[0076] It should be noted that the ideal natural frequency is the preset initial natural frequency parameter. The initial natural frequency parameter of the accelerometer is known. During the use of the accelerometer, the movement may be affected by environmental factors (shock, vibration, etc.), which may damage the structure of the movement and change the natural frequency parameter of the MEMS accelerometer, thereby changing the performance of the accelerometer and reducing the stability of the accelerometer. Therefore, it is necessary to detect whether the current natural frequency parameter of the accelerometer deviates from the initial natural frequency parameter, which affects the performance and stability of the accelerometer.

[0077] It should be noted that detecting the natural frequency parameter of the accelerometer is essentially to determine whether the current natural frequency parameter deviates from the initial natural frequency deviation. Therefore, during the detection, the initial natural parameter frequency should be within the frequency range of the multiple two-channel carrier signals used for the detection. For example, if the initial natural frequency parameter is 3000 Hz (Hz), the frequency range of the multiple two-channel carrier signals is 1000Hz-4000Hz, and the frequency increases gradually.

[0078] It should be noted that when detecting the natural frequency parameters, no external force is applied to the accelerometer, and no capacitance change will occur in the processing circuit of the accelerometer. Therefore, the first voltage and the second voltage need to be different to generate different electrostatic forces, thereby causing capacitance changes in the processing circuit and generating signals. Because the frequencies of the two carrier signals are different, the capacitance changes are different. Therefore, it is necessary to load two carrier signals of different frequencies to obtain a signal waveform related to the carrier frequency, thereby realizing the detection of the natural frequency parameters.

[0079] According to formula (4), when the first voltage and the second voltage are different, the electrostatic force will not cancel each other out, resulting in a capacitance change. The capacitance change is related to the frequency of the carrier signal. By loading carrier signals of different frequencies, the detection of the natural frequency parameters can be achieved.

[0080] In an embodiment of the present invention, by loading different voltages on the capacitor plates, when the accelerometer has no external force, only a capacitance change signal caused by the electrostatic force generated by the different voltages is generated, and a carrier signal with a gradually increasing frequency is generated, and a signal waveform related to the carrier frequency is generated, so as to realize the detection of the natural frequency parameters of the accelerometer.

[0081] In the embodiment of the present invention, the frequency of each demodulation signal used by the generation circuit 321 when demodulating each of the target voltage signals is twice the frequency of the corresponding positive carrier signal or negative carrier signal.

[0082] It should be noted that when detecting the natural frequency parameters, there are multiple two-way carrier signals with different frequencies to modulate the capacitance change. Therefore, during the subsequent demodulation, there are also multiple demodulation signals with different frequencies. Each of the two-way carrier signals corresponds to the demodulation signal one by one, and the frequency of the demodulation signal is twice the frequency of the corresponding two-way carrier signals. It can also be said that the two-way carrier signals are half-frequency signals, and the demodulation signal is a full-frequency signal.

[0083] It should be noted that the charge amount is calculated as follows:

[0084] (5)

[0085] Where Q represents the charge, express and The voltage difference between Represents static capacitance.

[0086] Combining formula (4) and formula (5), we can get the following formula (6): (6)

[0087] From formula (6), we can see that the first term in the expression of charge quantity is the square of the carrier signal. Therefore, only by using the half-frequency signal as the carrier signal and the full-frequency signal as the demodulation signal can a DC signal be obtained. The frequency corresponding to the maximum amplitude of the DC signal is the natural frequency parameter.

[0088] For example, Fig. 9 Schematic diagram of a half-frequency signal and a full-frequency signal provided by an embodiment of the present invention. Fig. 9 As shown, the horizontal axis represents frequency, the vertical axis represents digital quantity, the solid line represents half-frequency signal, and the dotted line represents full-frequency signal. Fig. 9 It can be seen that the frequency of the full-frequency signal is twice that of the half-frequency signal.

[0089] In the embodiment of the present invention, a variable frequency carrier signal is used to demodulate the full frequency demodulation signal to obtain a DC signal, and the DC signal is used to check the natural frequency parameters, thereby improving the accuracy of detecting the natural frequency parameters.

[0090] In the embodiment of the present invention, the functional instruction is the functional instruction for detecting acceleration, the first voltage is the same as the second voltage,

[0091] The generating circuit 321 further generates the two carrier signals using a function instruction based on the detected acceleration; The watch core structure 322 is further used to determine the capacitance change signal based on the external force corresponding to the acceleration; modulate the capacitance change signal based on the two carrier signals to obtain the charge signal; The capacitance detection circuit is used to convert the charge signal into the target voltage signal and send it to the generating circuit; The generating circuit 321 is further used to demodulate the target voltage signal to obtain acceleration, wherein the acceleration is the detection result.

[0092] Here, when the functional instruction is a functional instruction for detecting acceleration, the main control chip selects to execute a program for detecting acceleration and generates two carrier signals.

[0093] When detecting acceleration, the frequencies of the two carrier signals are the same as the frequency of the demodulated signal.

[0094] It should be noted that when detecting acceleration, since the first voltage is equal to the second voltage, according to formula (4), the electrostatic forces generated by the first voltage and the second voltage cancel each other out, so the electrostatic force does not affect the acceleration, and the capacitance change in the processing circuit is caused by the external force corresponding to the acceleration.

[0095] In an embodiment of the present invention, the same voltage is set on the capacitor plates to offset the electrostatic force, thereby ensuring that the capacitance change signal of the accelerometer is only generated by the external force of the accelerometer, thereby achieving the measurement of acceleration. In addition, the same voltage can also ensure the stability of the signal and provide accuracy in measuring acceleration.

[0096] further, Fig.10 FIG. 5 is a fifth connection diagram of the detection circuit provided by the present invention. Fig.10 As shown, the generating circuit 321 includes: a main control chip 3211 and a signal processing circuit 3212, wherein: The main control chip 3211 is connected to the function selection module 310 and the signal processing circuit 3212 respectively, and the signal processing circuit 3212 is connected to the watch movement structure 322; The main control chip 3211 is used to generate an initial carrier signal corresponding to the functional instruction based on the functional instruction; The signal processing circuit 3212 is used to perform signal processing on the initial carrier signal to obtain the two carrier signals.

[0097] Here, the initial carrier signal may be any suitable carrier signal, for example, a sinusoidal signal.

[0098] The signal processing circuit can amplify, filter, reverse, and perform other operations on the initial carrier signal.

[0099] In the embodiment of the present invention, the main control chip is used to generate an initial carrier signal, and then a signal processing circuit is used to process the initial carrier signal, thereby improving the accuracy of the signal and thus improving the accuracy of detecting acceleration or natural frequency parameters.

[0100] further, Fig.11 This is the sixth connection diagram of the detection circuit provided by the present invention, such as Fig.11 As shown, the two carrier signals include a positive carrier signal and a negative carrier signal, and the signal processing circuit 3212 includes a bandpass filter circuit 32121 and an inverting circuit 32122, wherein: The bandpass filter circuit 32121 is respectively connected to the main control chip 3211, the watch movement structure 322 and the reverse circuit 32122, and the reverse circuit 32122 is connected to the watch movement structure 322; The bandpass filter circuit 32121 is used to amplify the amplitude of the initial carrier signal to obtain the positive carrier signal; The inverting circuit 32122 is used to generate the negative carrier signal based on the positive carrier signal.

[0101] Here, the bandpass filter circuit can be a co-directional amplifier circuit or a circuit combining a co-directional amplifier circuit and a filter. Among them, the co-directional amplifier circuit is usually composed of an operational amplifier and an external resistor. In addition, when the bandpass filter circuit includes a co-directional amplifier circuit and a filter, it can amplify the amplitude of the two-way carrier signal and filter the noise in the two-way carrier signal.

[0102] Here, the positive carrier signal and the negative carrier signal are two high-frequency complementary sinusoidal wave modulation signals with the same reference, amplitude and frequency and a phase difference of 180°.

[0103] Specifically, the initial carrier signal is amplified by the bandpass filter circuit to obtain a positive carrier signal. The positive carrier signal is input into the first end of the meter core structure in one way and generates a negative carrier signal through the reverse circuit in the other way. The positive carrier signal is input into the second end of the meter core structure to modulate the capacitance change signal.

[0104] In an embodiment of the present invention, an inverting circuit is used to obtain two high-frequency complementary carrier signals with the same reference, amplitude and frequency and a phase difference of 180° to modulate the capacitance change signal generated in the watch movement structure. In this way, the two complementary carrier signals are used to offset the superposition effect, improve the performance of the accelerometer, and stimulate the resonant structure inside the accelerometer to vibrate in a more stable and predictable manner, thereby improving the accuracy and sensitivity of the measurement.

[0105] further, Fig.12 FIG. 7 is a seventh connection diagram of the detection circuit provided by the present invention. Fig.12 As shown, the main control chip 3211 also includes: an analog-to-digital converter 32111 and a demodulation unit 32112, wherein: The analog-to-digital converter 32111 is connected to the capacitance detection circuit 323 and the demodulation unit 32112 respectively; The analog-to-digital converter 32111 is used to convert the analog signal of the target voltage signal into a digital signal; The demodulation unit 32112 is further used to demodulate the digital signal to obtain the detection result.

[0106] Here, the analog-to-digital converter 32111 and the demodulation unit 32112 may transmit signals via a serial peripheral interface (SPI).

[0107] Here, the analog-to-digital converter converts the analog signal of the target voltage signal into a digital signal, which is essentially a process of unpacking the target voltage signal. Unpacking refers to converting the continuous changes of the analog signal into discrete values ​​of the digital signal through steps such as sampling, quantization and encoding. It should be understood that the target voltage signal obtained above is an analog voltage signal. Therefore, the analog voltage signal needs to be unpacked to obtain the digital quantity, that is, the voltage signal to be demodulated.

[0108] In an embodiment of the present invention, an analog signal is converted into a digital signal by utilizing an analog-to-digital converter. Compared with the analog signal, the digital signal has higher accuracy, improves the resolution of the signal, and makes signal processing more accurate; and reduces errors caused by fluctuations and noise of the analog signal, making the digital signal more convenient to process, thereby improving the efficiency of signal processing.

[0109] In an embodiment of the present invention, the current function instruction is judged as an acceleration detection function or an inherent frequency parameter extraction function by reading the function instruction signal in the lower computer program. When it is judged as an acceleration detection function instruction, the program first obtains a full-frequency digital code table, then obtains the code table address through DAC, converts the digital code table into an analog code table, and then outputs a carrier signal as a table core structure. After the analog-to-digital converter (ADC) in the circuit converts the analog signal related to acceleration into a digital signal, the lower computer program is set to transmit the signal back to the single chip microcomputer (MCU) through SPI, and uses full-frequency signal demodulation. After demodulation, the lower computer converts the voltage change into the capacitance change through the capacitance voltage conversion relationship. Here, the capacitance change is related to acceleration, and acceleration detection can be realized; when it is judged as an inherent frequency parameter extraction function instruction, the program first obtains a half-frequency digital code table, then obtains the code table address through DAC, converts the digital code table into an analog code table, and then outputs the driving signal as the table core. After the ADC in the circuit converts the analog signal related to acceleration into a digital signal, the lower computer program is set to transmit the signal back to the MCU via SPI and demodulate it using the full-frequency signal. The demodulated signal is then output through the serial port. When the output signal has a resonance peak, the corresponding frequency is the natural frequency.

[0110] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, a person skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features can be replaced by equivalents. However, these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A detection circuit, characterized in that: include: Function selection module and detection module, where: The function selection module is connected to the detection module; The function selection module is used to generate a function instruction of the detection module based on a user's selection instruction, wherein the function instruction includes: a function instruction for detecting acceleration or a function instruction for detecting a natural frequency parameter; The detection module is used to determine the detection result corresponding to the functional instruction based on the functional instruction.

2. The detection circuit according to claim 1, characterized in that: The detection module includes: a generating circuit, a watch core structure and a capacitance detection circuit, wherein: The generating circuit is respectively connected to the function selection module, the watch core structure and the capacitance detection circuit, the watch core structure is connected to the capacitance detection circuit, and the function selection module is connected to the capacitance detection circuit; The generating circuit is used to generate two complementary carrier signals corresponding to the functional instruction based on the functional instruction; The watch core structure is used to modulate the capacitance change signal generated by the watch core structure based on the two carrier signals to obtain a charge signal; The capacitance detection circuit is used to convert the charge signal into the target voltage signal and send it to the generating circuit; The generating circuit is further used to determine the detection result corresponding to the functional instruction based on the target voltage signal.

3. The detection circuit according to claim 2, characterized in that: The two carrier signals include a positive carrier signal and a negative carrier signal, and the core structure includes: a first capacitor plate, a second capacitor plate and an intermediate capacitor plate, wherein: The generating circuit is connected to the first capacitor plate and the second capacitor plate respectively, the middle capacitor plate is connected to the capacitance detection circuit, and the middle capacitor plate is located between the first capacitor plate and the second capacitor plate; The first capacitor plate is used to receive the positive carrier signal and obtain a first voltage signal based on the positive carrier signal; The second capacitor plate is used to receive the load wave signal and obtain a second voltage signal based on the load wave signal; The intermediate capacitor plate is used to determine the charge signal based on the first voltage signal and the second voltage signal.

4. The detection circuit according to claim 3, characterized in that: The function selection module includes: a first voltage unit and a second voltage unit, wherein: The first voltage unit is connected to the generating circuit, and the second voltage unit is connected to the capacitance detecting circuit; The first voltage unit is used to apply a first voltage to the first capacitor plate and the second capacitor plate; The second voltage unit is used to apply a second voltage to the middle capacitor plate; The meter movement structure is also used to determine the target voltage signal based on the positive carrier signal, the negative carrier signal, the first voltage and the second voltage.

5. The detection circuit according to claim 4, characterized in that: The functional instruction is the functional instruction for detecting the natural frequency parameter, and the first voltage is different from the second voltage; The generating circuit is further used to generate at least two groups of the two carrier signals with gradually increasing frequencies based on the functional instruction for detecting the natural frequency parameter; the minimum frequency corresponding to the two carrier signals is less than the ideal natural frequency parameter, and the maximum frequency corresponding to the two carrier signals is greater than the ideal natural frequency parameter; The watch movement structure is further used to determine the capacitance change signal based on the first voltage and the second voltage; modulate the capacitance change signal based on the at least two groups of the two carrier signals that are increasing continuously to obtain at least two charge signals; The capacitance detection circuit is further used to convert each of the charge signals into the corresponding target voltage signals and send them to the generation circuit; The generating circuit is further used to demodulate each of the target voltage signals to obtain a signal waveform related to the carrier frequency, and determine the natural frequency parameter based on the signal waveform, wherein the natural frequency parameter is the detection result.

6. The detection circuit according to claim 5, characterized in that: The frequency of each demodulation signal used by the generation circuit when demodulating each of the target voltage signals is twice the frequency of the corresponding positive carrier signal or negative carrier signal.

7. The detection circuit according to claim 4, characterized in that: The functional instruction is the functional instruction for detecting acceleration, the first voltage is the same as the second voltage, The generating circuit further generates the two carrier signals using a functional instruction based on the detected acceleration; The watch movement structure is further used to determine the capacitance change signal based on the external force corresponding to the acceleration; modulate the capacitance change signal based on the two carrier signals to obtain the charge signal; The capacitance detection circuit is used to convert the charge signal into the target voltage signal and send it to the generating circuit; The generating circuit is further used to demodulate the target voltage signal to obtain acceleration, wherein the acceleration is the detection result.

8. The detection circuit according to any one of claims 2 to 7, characterized in that: The generating circuit comprises: a main control chip and a signal processing circuit, wherein: The main control chip is respectively connected to the function selection module and the signal processing circuit, and the signal processing circuit is connected to the watch movement structure; The main control chip is used to generate an initial carrier signal corresponding to the functional instruction based on the functional instruction; The signal processing circuit is used to perform signal processing on the initial carrier signal to obtain the two carrier signals.

9. The detection circuit according to claim 8, characterized in that: The two carrier signals include a positive carrier signal and a negative carrier signal, and the signal processing circuit includes a bandpass filter circuit and an inverting circuit, wherein: The bandpass filter circuit is respectively connected to the main control chip, the watch core structure and the reverse circuit, and the reverse circuit is connected to the watch core structure; The bandpass filter circuit is used to amplify the amplitude of the initial carrier signal to obtain the positive carrier signal; The inverting circuit is used to generate the negative carrier signal based on the positive carrier signal.

10. The detection circuit according to any one of claims 9, characterized in that: The main control chip includes: an analog-to-digital converter and a demodulation unit, wherein: The analog-to-digital converter is respectively connected to the capacitance detection circuit and the demodulation unit; The analog-to-digital converter is used to convert the analog signal of the target voltage signal into a digital signal; The demodulation unit is further used to demodulate the digital signal to obtain the detection result.

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