CN206593664U - A kind of micro-mechanical gyroscope closed-loop driving circuit of anti-electricity vibration - Google Patents

Abstract

The utility model discloses a micromechanical gyroscope closed-loop driving circuit for preventing electrical oscillation, which is characterized in that a closed-loop is composed of a gyroscope sensor, a readout circuit, a comparator, a phase-locked loop, an amplitude adjustment circuit and a switch 2, and is responsible for driving The gyroscope sensor device oscillates along the drive shaft; the amplitude extraction circuit, the amplitude adjustment circuit, the readout circuit, and the gyroscope sensor device form a closed loop, which is responsible for controlling the oscillation amplitude of the gyroscope sensor device to be constant; the excitation circuit is responsible for exciting the gyroscope sensor device to oscillate, and the frequency measurement The circuit is responsible for reading the frequency value of the oscillating signal, and the voltage preset circuit is responsible for converting the frequency value into a preset voltage signal and applying it to the voltage-controlled oscillator in the phase-locked loop to preset the start-up frequency of the voltage-controlled oscillator. The advantage of the closed-loop driving circuit of the utility model is that by presetting the start-up frequency of the voltage-controlled oscillator, the narrow-band filtering and frequency tracking functions of the phase-locked loop are used to effectively avoid the occurrence of electrical oscillations, and it can be realized by normal-voltage integrated circuit technology.

Description

A micromechanical gyroscope closed-loop drive circuit against electrical oscillation

technical field

The utility model relates to a closed-loop driving circuit of a micro-mechanical gyroscope, in particular to a closed-loop driving circuit of a micro-mechanical gyroscope for preventing electrical oscillation.

Background technique

Micro-Electro-Mechanical System (MEMS) is a micro-electromechanical system that integrates micro-sensors, micro-actuators, micro-mechanical structures, micro-power sources, signal processing and control circuits, high-performance electronic integrated devices, interfaces, and communications. device or system. Micromachined gyroscope is an important inertial MEMS device. A typical micromachined gyroscope consists of two parts: a sensing device and an interface circuit, and its working principle is based on the Coriolis Force effect. Taking the resonant capacitive micromachined gyroscope as an example, as shown in Figure 1, the closed-loop drive circuit first drives the drive mode (X direction) of the sensing device to the resonance state, and when there is an external angular velocity Ω _z input, in the detection mode state (Y direction) will generate a Coriolis force F _c of 2MΩv, and this Coriolis force will cause the Y direction to generate an amplitude modulation displacement signal y(t) with the same frequency as the X direction, thus causing the equivalent capacitance C of the detection plate (t) changes, the output voltage signal V _out reflecting the input angular velocity signal Ω _z can be obtained by reading C(t) through the detection circuit and demodulating and filtering it.

Due to the limited precision of the processing technology of the micromechanical gyroscope sensor device, there is inevitably a parasitic capacitance between the driving plate and the driving feedback plate in the driving direction of the sensor device, which is called a parasitic jumper capacitance, as shown in Figure 2 . Due to the existence of the parasitic cross-connection capacitance, the driving signal can be directly coupled to the driving feedback terminal through the capacitance, which brings many negative effects. The main negative effects include preventing "electro-mechanical" oscillations from occurring and inducing "electrical oscillations". As shown in Figure 3, the "electrical-mechanical" oscillation refers to the oscillation formed by the closed-loop drive circuit, the equivalent capacitance C _d of the driving plate, and the equivalent capacitance C _s of the driving feedback plate, which is generally determined by the resonant frequency of the gyroscope drive shaft. It is expected to occur in the range of several thousand hertz (kHz) to tens of thousand hertz (kHz); while "electrical oscillation" refers to the oscillation formed by the closed-loop drive circuit and the parasitic cross-connection capacitance C _f , which is caused by the closed-loop drive circuit structure and parasitic It is related to the size of the cross-connect capacitance C _f , which is generally above hundreds of kilohertz (kHz), which is not expected to happen. However, when the loop formed by the closed-loop drive circuit and the parasitic jumper capacitor meets the gain and phase conditions for oscillation, the gyroscope may fall into the electrical oscillation frequency point and fail to work normally. Therefore, it is necessary to find a way to avoid electrical oscillation.

The reason why the parasitic crossover capacitance prevents the "electrical-mechanical" oscillation from occurring is analyzed as follows. As shown in Figure 3, when there is a parasitic cross-connect capacitance C _f , the current detected by the closed-loop drive circuit is the _{superposition} of the current if coupled by C _f and the current _is of the micro-gyro drive feedback plate. _Because there is a ₉₀ -degree phase difference between if and is, if if _{is much} larger than is, the expected "electrical-mechanical" oscillation will not _occur because the phase condition in the loop cannot be satisfied. The oscillator electrical model in Figure 3 can be expressed as

Among them, X is the displacement of the gyroscope mass block, F _ext is the driving force, m _x is the weight of the gyroscope mass block in the X-axis direction, ω _x is the intrinsic angular frequency of the gyroscope drive shaft, Q is the quality factor of the gyroscope drive shaft, V _dc and V _b are the DC voltage difference between the driving end and the driving feedback end respectively, V _dr is the driving voltage, C _d is the equivalent capacitance of the driving plate, C _s is the equivalent capacitance of the driving feedback plate, and K _F/V ² is The conversion coefficient of driving voltage to driving force, K _c/x is the conversion coefficient of displacement capacitance. From formula (1), the expression of oscillator transconductance can be obtained as

Let the transconductance phase in formula (2) be equal to zero, and the equation can be obtained

Where ω _d is the driving signal frequency. In order to make equation (3) have real roots, it is necessary to satisfy

Equation (4) shows that there are two main ways to avoid electrical oscillations. The first is to minimize the value of the parasitic capacitance C _f across the connection from the perspective of mechanical design of the sensor device; the second is from the perspective of circuit design. Various variables in formula (4), such as increasing the polarization voltage V _p applied to the mass block of the micro gyro, to increase the DC voltage difference V _b and V _dc .

Current methods to avoid electrical oscillation include, in terms of mechanical design, changing the substrate material from silicon to glass (see Alper S E, Akin T. Symmetrical and decoupled nickel microgyroscope on insulating substrate [J]. Sensors & Actuators A Physical, 2004, 115( 2–3):336-350.), adding a bias plate between the driving plate and the driving feedback plate (see Park H W, Kim Y K, Jeong H G, etal. Feed-through capacitance reduction for a micro-resonator with push–pull configuration based on electrical characteristic analysis of resonator with direct drive[J].Sensors&Actuators A Physical,2011,170(1):131-138.), but these methods can only reduce the parasitic cross-connection capacitance in essence, and Electrical oscillation cannot be completely avoided, and it will increase the design complexity of the sensing device. In terms of circuit design, there is currently a method of connecting a compensation capacitor across the transimpedance amplifier to suppress high-frequency oscillation signals (see Alper S E, Sahin K, Akin T. An Analysis to Improve Stability of Drive-Mode Oscillations in Capacitive Vibratory MEMS Gyroscopes [J].2009,51(1):817-820.), but the disadvantage of this method is that a large compensation capacitor will introduce a large phase shift, resulting in a large deviation of the oscillation frequency from the resonance frequency. Another method is to increase the bias voltage on the mass of the sensing device, so as to avoid falling into the electrical oscillation point when the oscillator starts to oscillate (see Wu H M, Yin T, Jiao J W, et al. Analysis of parasitic feed-through capacitance effect in closed-loop drive circuit design for capacitivemicro-gyroscope[J].Microsystem Technologies,2016,22(9):1-7.), but the disadvantage of this method is that the stable high voltage bias is difficult to integrate in the conventional voltage process implemented on a circuit chip.

Contents of the invention

The purpose of this utility model is to provide a micro-mechanical gyroscope closed-loop drive circuit for preventing electrical oscillation, so as to solve the problem that the oscillation frequency deviates from the resonant frequency and the high-voltage bias in the design of the current closed-loop drive circuit for preventing electrical oscillation. The problem of implementation is to avoid the gyroscope drive shaft from falling into electrical oscillation and cause the gyroscope to not work properly.

The technical solution adopted by the utility model to solve the problems of the technologies described above is:

A micromechanical gyroscope closed-loop drive circuit for preventing electrical oscillation, comprising a gyroscope sensor, a readout circuit, a comparator, a phase-locked loop, an amplitude extraction circuit, an amplitude adjustment circuit, a frequency measurement circuit, a voltage preset circuit, and an excitation circuit And switch 1, switch 2, switch 3 and timing control circuit. The design idea of this closed-loop drive circuit connects the phase-locked loop into the closed-loop drive circuit in series, and presets the voltage-controlled oscillator in the phase-locked loop to the resonant frequency of the gyroscope drive shaft to start the oscillation. Tracking function to avoid electrical oscillation.

The driving feedback plate of the gyro sensor device is connected to the readout circuit, the readout circuit is connected to the comparator, the comparator is connected to the phase-locked loop, the phase-locked loop is connected to the amplitude adjustment circuit, and the amplitude adjustment circuit The switch 2 is disconnected or connected with the driving plate of the gyro sensor device to form a closed loop, which is responsible for driving the gyro sensor device to oscillate along the drive axis.

The amplitude extraction circuit is respectively connected with the readout circuit and the amplitude adjustment circuit, and forms a closed-loop feedback control oscillation signal amplitude with the gyroscope sensor device.

The excitation circuit is disconnected or connected to the driving plate of the gyroscope sensor device through the switch 1, and is responsible for exciting the gyroscope sensor device to oscillate. The setting circuit is connected with the frequency measuring circuit to convert the frequency value into a preset voltage signal, and is disconnected or connected to the voltage-controlled oscillator in the phase-locked loop through the switch 3, which is responsible for preset the start-up frequency of the voltage-controlled oscillator.

The timing control circuit is responsible for controlling the timing of closing and opening of the switch 1 , the switch 2 and the switch 3 .

The specific working principle and working sequence of the closed-loop drive circuit are as follows: switch 1, switch 2, and switch 3 are all open in the initial stage; in the first stage, switch 1 is quickly opened after it is closed, and switch 2 and switch 3 are kept open. The principle of excitation-attenuation, the excitation circuit excites the gyroscope sensor device, and then cancels the excitation, the sensor attenuates and oscillates at the resonant frequency, the frequency measurement circuit reads the frequency value of the attenuation oscillation signal, and the voltage preset circuit calculates the corresponding phase-locked loop The preset voltage of the VCO; in the second stage, switch 1 and switch 2 are kept open, and switch 3 is closed, and the preset voltage is applied to the VCO; in the third stage, switch 1 is kept open, switch 3 is opened, and switch 2 Closed, the phase-locked loop is used to track the resonant frequency of the gyroscope, and the vibration amplitude of the sensor is controlled by feedback from the amplitude extraction circuit and the amplitude adjustment circuit, so that the gyroscope sensor oscillates at a constant amplitude at the resonant frequency.

The initial oscillation frequency of the voltage-controlled oscillator of the phase-locked loop can be preset through the preset input control voltage.

The voltage preset circuit establishes a mapping relationship between the measured frequency value and the frequency corresponding to the voltage-controlled oscillator through the conversion of the frequency value into the voltage.

The amplitude adjustment circuit obtains a difference by comparing the amplitude signal output by the amplitude extraction circuit with the reference signal, and uses the difference to adjust the amplitude of the square wave signal output by the phase-locked loop.

Compared with the prior art, the utility model has the advantage that the closed-loop driving circuit connects the phase-locked loop into the closed-loop loop, and uses the phase-locked loop with the preset start-up frequency to track the resonant frequency of the gyroscope drive shaft, thereby effectively avoiding the occurrence of electrical oscillations , and can be realized by atmospheric pressure integrated circuit technology.

Description of drawings

Fig. 1 is a schematic diagram of the working principle of a capacitive resonant micromachine gyroscope involved in the present invention, but not limited to the capacitive type, other types of resonant micromachines are also applicable to the present invention;

FIG. 2 is a schematic diagram of a micro-mechanical gyroscope sensor device in the prior art where stray capacitance exists across the bridge;

FIG. 3 is a model of an oscillator composed of a gyroscope sensor and a closed-loop drive circuit when parasitic jumper capacitors exist in the prior art;

Fig. 4 is the block diagram of the micromechanical gyroscope closed-loop driving circuit for preventing electrical oscillation described in the utility model;

Fig. 5 is a working sequence diagram of the closed-loop driving circuit described in the utility model;

Fig. 6 is a kind of implementation structure of excitation circuit in Fig. 4, is a kind of relaxation oscillator with adjustable frequency;

Fig. 7 is a kind of realization structure of frequency measurement circuit in Fig. 4;

Fig. 8 is a kind of implementation structure of phase-locked loop in Fig. 4;

Fig. 9 is a kind of realization circuit of voltage-controlled oscillator in Fig. 8, is four-stage ring structure;

FIG. 10 is a realization structure of the readout circuit in FIG. 4, which is a readout circuit with a transimpedance amplification structure;

Fig. 11 is a kind of implementation structure of comparator in Fig. 4, is hysteresis structure comparator;

Figure 12 is a realization structure of the amplitude extraction circuit in Figure 4, which is a rectifier structure;

FIG. 13 is an implementation structure of the amplitude adjustment circuit in FIG. 4 , which is an amplitude adjustment circuit based on a proportional-integral controller structure.

detailed description

The block diagram and working principle of a micromechanical gyroscope closed-loop drive circuit for preventing electrical oscillation of the present utility model are shown in Figure 4. The closed-loop drive circuit consists of a gyroscope sensor, a readout circuit, a comparator, a phase-locked loop, and an amplitude extraction circuit. , Amplitude adjustment circuit, frequency measurement circuit, voltage preset circuit, excitation circuit, switch 1, switch 2, switch 3 and timing control circuit. The gyro sensor device, readout circuit, comparator, phase-locked loop, amplitude adjustment circuit and switch 2 form a closed loop, which is responsible for driving the gyro sensor device to oscillate along the drive axis. The amplitude extraction circuit, the amplitude adjustment circuit, the readout circuit, and the gyroscope sensor form a closed loop, which is responsible for controlling the oscillation amplitude of the gyroscope sensor to be constant. The excitation circuit is responsible for exciting the gyroscope sensor device to oscillate, the frequency measurement circuit is responsible for reading the frequency value of the oscillation signal, and the voltage preset circuit is responsible for converting the frequency value into a preset voltage signal and applying it to the voltage-controlled oscillator in the phase-locked loop. Preset the start-up frequency of the VCO. The timing control circuit controls the working timing of the circuit by controlling the closing and opening of the switch 1 , the switch 2 and the switch 3 .

The initial oscillation frequency of the voltage-controlled oscillator of the phase-locked loop can be preset through the preset input control voltage.

The voltage preset circuit establishes a mapping relationship between the measured frequency value and the frequency corresponding to the voltage-controlled oscillator through the conversion of the frequency value to the voltage.

The amplitude adjustment circuit obtains the difference by comparing the amplitude signal output by the amplitude extraction circuit with the reference signal, and uses the difference to adjust the amplitude of the square wave signal output by the phase-locked loop.

The design idea of the closed-loop drive circuit is to preset the voltage-controlled oscillator in the phase-locked loop to the resonant frequency of the gyroscope drive shaft to start oscillation, and use the narrow-band filtering and frequency tracking functions of the phase-locked loop to avoid electrical oscillations. Therefore, the working sequence of the closed-loop drive circuit can be divided into four stages, as shown in Figure 5, in the initial stage, switch 1, switch 2 and switch 3 are all open, and the circuit is on standby; Switch 3 is kept closed, using the "excitation-attenuation" principle of the oscillator, the excitation circuit excites the gyroscope sensor device, the sensor attenuates and oscillates according to the resonant frequency, and then the frequency measurement circuit reads out the frequency value of the attenuation oscillation signal and presets it by the voltage The circuit calculates the preset voltage of the voltage-controlled oscillator in the corresponding phase-locked loop; in the second stage, switch 1 and switch 2 are kept open, switch 3 is closed, and the preset voltage is applied to the voltage-controlled oscillator, and the preset voltage of the voltage-controlled oscillator is Initial oscillation frequency; in the third stage, switch 1 is kept open, switch 3 is opened, and switch 2 is closed. The phase-locked loop is used to track the resonant frequency of the gyroscope, and the vibration amplitude of the sensor is controlled by feedback from the amplitude extraction circuit and the amplitude adjustment circuit, so that the gyroscope sensor device Oscillates with a constant amplitude at the resonant frequency. The implementation manner or structure of the involved circuit modules will be described in sequence below in accordance with the above sequence.

The "excitation-attenuation" principle means that when the gyroscope sensor device is stimulated for a period of time and then the excitation is withdrawn, the sensor device will attenuate the oscillation at its resonant frequency, which can be expressed as

In formula (5), V ₀ is the initial voltage, which depends on the initial state of the sensor and the circuit, ω ₀ is the resonant frequency of the drive shaft of the sensor, Q is the quality factor of the drive shaft, and t is time.

Figure 6 is an implementation of an excitation circuit, which is a relaxation oscillator with adjustable frequency. During operation, the output signal frequency of the oscillator can be tuned to be close to the resonant frequency of the drive shaft of the gyroscope sensor device by adjusting the off-chip resistance R _set , and then revoke after a period of incentives. The basic principle of the relaxation oscillator in Figure 6 is described as follows: the reference current I _c alternately charges the two capacitors C _m1 and C _m2 , the voltages on the two capacitors are compared with the reference voltage V _ref by the comparator, and the obtained digital signal The control signals V _c1 and V _c2 are generated through the SR flip-flop, and applied to the inverter composed of M _2~5 to control the charging and discharging of the capacitor. Since the discharge rate is much faster than the charge, the discharge time can be ignored in the calculation, and the period of the control signal V _c2 can be expressed as

Among them, ΔV is the charging voltage range, and C _m is the charging and discharging capacitance. The frequency of the output signal f _c can be expressed as

The size of the charging current I _c can be adjusted by the off-chip resistor R _set , the expression is

Among them, V _ref is the reference voltage. Combining equations (6), (7) and (8), the center frequency of the bandpass filter can be obtained as

Wherein, it can be seen from formula (9) that by adjusting the off-chip resistance R _set , the frequency adjustment of the output signal can be realized.

FIG. 6 is only an implementation structure of the excitation circuit, but is not limited to this structure.

Fig. 7 is an implementation structure of a frequency measurement circuit, but it is not limited to this structure. The comparator converts the attenuated input signal V _in into a square wave signal V _comp , and then the counter outputs a digital signal through the control of the clock Clk.

The voltage preset circuit can be implemented by a digital-to-analog converter, but is not limited to this structure. The digits of the digital-to-analog converter are unified with the output digits of the frequency measurement circuit, and the frequency corresponding to the voltage-controlled oscillator in the phase-locked loop is realized by controlling the reference voltage of the digital-to-analog converter. For example, if the output of the frequency measurement circuit is a 14-bit digital signal, the maximum can represent (2 ¹⁴ -1) Hz, that is, a signal of about 16.4kHz, and the digital-to-analog converter is selected to be 14-bit; assuming that the voltage in the phase-locked loop The maximum oscillation frequency of the controlled oscillator is 2 ²⁴ Hz. If the maximum resonant frequency of the sensing device is 2 ¹⁴ Hz, the frequency divider in the phase-locked loop is set to 2 ¹⁰ frequency division. If the control voltage range is 1-4V, the digital-analog If the reference voltage of the converter is set to 1.5V and the bias is set to 2.5V, then the output of the digital-to-analog converter is also 1-4V, so that the actual measured frequency can be transmitted to the voltage-controlled oscillator through the preset voltage.

Figure 8 is an implementation structure of a charge pump phase-locked loop, but not limited to this structure, which consists of a frequency detector, a charge pump, a low-pass filter, a voltage-controlled oscillator and a frequency divider, and the preset voltage is loaded on Voltage Controlled Oscillator Input.

FIG. 9 is an implementation structure of a voltage-controlled oscillator, which is a four-stage ring structure, but is not limited to this structure. The gain stage in the figure adopts a fully differential structure with a wide adjustment range. The input control voltage V _cont changes the charge and discharge cycle of the load capacitor _CL by adjusting the size of the tail current source of the gain stage, thereby adjusting the output signal oscillation frequency. The buffer stage adopts the differential gain stage of the current mirror load to convert the differential signal into a single-ended signal, and is shaped into a square wave signal by an inverter.

FIG. 10 is an implementation structure of a readout circuit, which is a transimpedance amplification structure, but is not limited to this structure. The amplifier in the figure is a fully differential structure, which is composed of a fully differential amplifier, a resistor R _F and a compensation capacitor C _F. The fully differential amplifier adopts a folded cascode structure, and the DC operating point of the amplifier is guaranteed to be normal by input common-mode feedback and output common-mode feedback.

FIG. 11 is an implementation structure of a comparator, which is a hysteresis comparator structure, but is not limited to this structure. The comparator is composed of four parts: preamplifier, latch, self-biased differential amplifier stage and output driver, which can better solve the problem of false flipping of the threshold point caused by input signal noise.

FIG. 12 is an implementation of an oscillation signal amplitude extraction circuit, which is a rectifier structure, but is not limited to this structure. The rectifier adopts a self-demodulation structure, and the input differential signal passes through the hysteresis comparator and the non-overlapping clock to generate four demodulation signals for the demodulation switch. Under the control of the demodulation signal, the demodulation switch performs full-wave rectification on the input differential signal, and the output differential signal is converted into a single-ended signal output by the instrumentation amplifier. The filter capacitors and buffers before and after the demodulation switch are used to reduce the impact of the glitch generated by the demodulation switch on the front and rear stages.

Since the output of the phase-locked loop is a square wave signal, the amplitude adjustment circuit cannot be simply implemented with a variable gain amplifier. A realization method of an amplitude adjustment circuit is to compare the signal obtained by the amplitude extraction circuit with a reference value and then output the output signal as a square wave signal power supply voltage, that is, by adjusting the amplitude of the main frequency signal in the square wave signal. The realized circuit structure is shown in Figure 13. The high-gain cascode operational amplifier, the off-chip adjustable resistor R, and the adjustable capacitor C form a proportional-integral controller. After comparing the input amplitude signal V _amp with the reference signal V _ref The output control signal V _ctr is used as the power supply voltage of the inverter to adjust the amplitude of the square wave oscillation signal V _in (output signal of the phase-locked loop), and output the V _out signal. Another implementation method of the amplitude adjustment circuit is to convert the square wave signal output by the phase-locked loop from a square wave to a triangle wave signal circuit and a triangle wave to a sine wave signal circuit into a sinusoidal signal output, and at the same time, a traditional proportional-integral controller can be used. The variable gain amplifier adjusts the amplitude of the oscillating signal, but the disadvantage of this method is that the frequency of the oscillating signal is generally several kilohertz or tens of kilohertz, so the filter capacitors of the square wave to triangular wave signal circuit and the triangular wave to sine wave signal circuit need to be placed It is off-chip and cannot be integrated on-chip.

It is worth noting that the above description is only a preferred embodiment of the utility model, and does not limit the scope of patent protection of the utility model. The utility model can also improve the materials and structures of the above-mentioned various parts and components. Or replace it with a technical equivalent. Therefore, all equivalent structural changes made by using the instructions and illustrations of the utility model, or directly or indirectly applied to other related technical fields are also included in the scope of the utility model.

Claims (4)

1. A micromachined gyroscope closed-loop drive circuit for preventing electrical oscillations, characterized in that it consists of a gyroscope sensing device, a readout circuit, a comparator, a phase-locked loop, an amplitude extraction circuit, an amplitude adjustment circuit, a frequency measurement circuit, and a voltage preset It consists of a setting circuit, an excitation circuit, a switch 1, a switch 2, a switch 3 and a timing control circuit. The drive feedback plate of the gyroscope sensor is connected to the readout circuit, the readout circuit is connected to the comparator, and the comparator It is connected to the phase-locked loop, the phase-locked loop is connected to the amplitude adjustment circuit, and the amplitude adjustment circuit is disconnected or connected to the driving plate of the gyro sensor through the switch 2 to form a closed loop, which is responsible for driving the gyro sensor to oscillate along the drive axis ; The amplitude extraction circuit is respectively connected with the readout circuit and the amplitude adjustment circuit, and forms a closed-loop feedback control oscillation signal amplitude with the gyroscope sensor device; The excitation circuit is disconnected or connected to the driving plate of the gyro sensor device through the switch 1, which is responsible for exciting the gyro sensor device to oscillate, the frequency measurement circuit is connected with the readout circuit to read out the frequency value of the oscillation signal, and the voltage preset circuit is connected with the readout circuit. The frequency measurement circuit is connected to convert the frequency value into a preset voltage signal, and is disconnected or connected to the voltage-controlled oscillator in the phase-locked loop through the switch 3, and is responsible for preset the start-up frequency of the voltage-controlled oscillator; The timing control circuit is responsible for controlling the timing of closing and opening of switch 1, switch 2 and switch 3; The working sequence of the closed-loop drive circuit is that switch 1, switch 2, and switch 3 are all open in the initial stage; in the first stage, switch 1 is closed, switch 2 and switch 3 are kept open, the excitation circuit excites the gyroscope sensor device, and then switch 1 is opened, and the excitation is cancelled. , the sensor attenuates and oscillates according to the resonant frequency, the frequency value of the attenuated oscillation signal is read by the frequency measurement circuit, and the voltage preset circuit outputs the preset voltage of the voltage-controlled oscillator in the phase-locked loop; the second stage switch 1 and switch 2 are kept open , switch 3 is closed, and the preset voltage is applied to the voltage-controlled oscillator; in the third stage, switch 1 is kept open, switch 3 is opened, switch 2 is closed, the phase-locked loop tracks the resonant frequency of the gyroscope, and is controlled by the amplitude extraction circuit and the amplitude adjustment circuit Feedback controls the sensor oscillation amplitude, and the gyro sensing device oscillates at a constant amplitude at the resonant frequency. 2. A micromachined gyroscope closed-loop drive circuit for preventing electrical oscillation according to claim 1, characterized in that the initial oscillation frequency of the voltage-controlled oscillator of the phase-locked loop can be preset by preset input control voltage place. 3. A micromachined gyroscope closed-loop drive circuit for preventing electrical oscillation according to claim 1, characterized in that the voltage preset circuit converts the measured frequency value from the frequency value to the voltage with the voltage-controlled oscillation The frequency corresponding to the device establishes a mapping relationship. 4. The micromachined gyroscope closed-loop drive circuit for preventing electrical oscillation according to claim 1, wherein the amplitude adjustment circuit obtains a difference by comparing the amplitude signal output by the amplitude extraction circuit with the reference signal, and uses this The difference adjusts the amplitude of the square wave signal output by the phase-locked loop.