A MEMS gyroscope drive mode control circuit

Abstract

The application discloses a MEMS gyroscope driving mode control circuit, which comprises two parts of self-excitation starting loop and driving loop. The self-excitation starting loop comprises a CV conversion circuit, a frequency selection filter, a phase shift circuit, a low-pass filter and a driving circuit. The driving loop comprises a CV conversion circuit, an ADC, a digital filter, an AGC amplitude control circuit, a PLL phase control circuit, a DAC, a loop filter and a driving circuit. The application adopts a driving mode control technology combining a self-excitation oscillation driving mode and a phase-locked loop driving mode, which utilizes the advantage of fast starting speed of the self-excitation oscillation driving mode and avoids the deficiency of needing to set an initial frequency in advance of the phase-locked loop driving mode. Meanwhile, an adjustment mode combining adaptive adjustment and register adjustment is adopted, different gyroscopic table resonant frequencies are different, and each key parameter is configured quickly, so that the driving loop can track the resonant frequency of the gyroscopic table quickly, and stable frequency and amplitude oscillation is realized.

Description

TECHNICAL FIELD

[0001] The application relates to a MEMS gyroscope driving mode control circuit and belongs to the technical field of integrated circuits. BACKGROUND

[0002] The MEMS gyroscope is an angular velocity sensor based on the Coriolis effect, has the advantages of low cost, small size, easy integration, low power consumption and high reliability, and is widely applied in the fields of aerospace, automobile electronics, consumer electronics and industrial control. The driving mode control circuit is an important measurement and control circuit of the MEMS gyroscope, and the stable frequency and amplitude oscillation of the driving mode is the basis for the stable and reliable work of the MEMS gyroscope. When the sensitive axis has an angular velocity input, based on the Coriolis effect, only when the driving mode has the stable frequency and amplitude oscillation, the detection branch will have an output proportional to the input angular velocity.

[0003] Common MEMS gyroscope driving mode control methods include a self-excited oscillation driving method and a phase-locked loop driving method. The self-excited oscillation driving method fully utilizes the resonance characteristics of the MEMS gyroscope, has the advantage of fast start-up, but has the disadvantages of poor flexibility and difficulty in digitalization. The phase-locked loop driving method is flexible in design and easy to realize in digitalization, but has the disadvantage of needing to set an initial frequency in advance. Due to the influence of the MEMS processing technology and other factors, the resonance frequencies of different gyroscope heads have great differences, and the initial frequency usually needs to be determined by manual frequency sweeping in advance. The start-up speed of the gyroscope is related to the closeness of the initial set frequency of the PLL to the actual resonance frequency of the gyroscope. SUMMARY

[0004] The application solves the technical problem of overcoming the deficiencies of the prior art and provides a MEMS gyroscope driving mode control circuit design scheme. The circuit adopts the driving mode control technology combining the self-excited oscillation driving method and the phase-locked loop driving method, utilizes the advantage of fast start-up of the self-excited oscillation driving method, and avoids the deficiency of needing to set the initial frequency in advance of the phase-locked loop driving method. In addition, the circuit of the application also adopts the adjustment mode combining adaptive adjustment and register adjustment, can quickly configure each key parameter in view of the problem that the resonance frequencies of different gyroscope heads have differences, so that the driving loop can quickly track the resonance frequency of the gyroscope head to realize the stable frequency and amplitude oscillation.

[0005] The technical scheme adopted by the application is as follows:

[0006] A MEMS gyroscope driving mode control circuit, comprising a CV conversion circuit, a frequency selection filter, a phase shift circuit, a low-pass filter, a driving circuit, an ADC, a DAC, a digital filter, an AGC amplitude control circuit and a PLL phase control circuit.

[0007] The CV conversion circuit, the frequency selection filter, the phase shift circuit, the low pass filter and the driving circuit form a self-excitation starting loop; in the self-excitation starting loop, the input end of the CV conversion circuit is connected with the detection electrode of the MEMS gyroscope meter head driving mode, the CV conversion circuit converts the capacitance variation of the MEMS gyroscope into a voltage signal and amplifies, and the amplified signal is sent to the frequency selection filter; the frequency selection filter extracts the signal with the same frequency as the resonance frequency of the MEMS gyroscope meter head and sends it to the phase shift circuit; the phase shift circuit is used for generating 90° phase shift to offset the 90° phase difference between the driving force and the displacement of the MEMS gyroscope meter head; the phase-shifted signal is transmitted to the driving circuit after being filtered by the low pass filter, the driving capacity is enhanced, and then output to the driving electrode of the MEMS gyroscope meter head, so that the MEMS gyroscope meter head resonates quickly at its inherent resonance frequency.

[0008] The CV conversion circuit, the ADC, the digital filter, the AGC amplitude control circuit, the PLL phase control circuit, the DAC, the loop filter and the driving circuit form a closed-loop driving loop; in the closed-loop driving loop, the CV conversion circuit is used for converting the capacitance variation of the MEMS gyroscope into a voltage signal and amplifying, and the amplified signal is sent to the ADC circuit to convert the analog signal into a digital signal; the digital signal is filtered by the digital filter, and then the signal representing the driving mode amplitude is output to the AGC amplitude control circuit, and the signal representing the driving mode phase is output to the PLL phase control circuit, the two signals are modulated by the multiplier and then output to the DAC circuit; the DAC circuit converts the digital signal into an analog signal, which is sent to the driving circuit after filtering; the driving circuit is used for increasing the driving capacity of the signal to provide sufficient driving force for the gyroscope; the AGC amplitude control circuit is used for automatically adjusting the amplitude of the driving voltage to realize precise control of the driving amplitude; the PLL phase control circuit is used for tracking and locking the phase of the driving mode resonance frequency and the driving mode detection signal.

[0009] Further, the circuit of the present application further comprises switches PH1, PH2 and PH3; the switch PH1 is arranged between the frequency selection filter and the phase shift circuit, the switch PH2 is arranged between the low pass filter and the driving circuit, and the switch PH3 is arranged between the driving circuit and the loop filter.

[0010] Further, in the starting stage of the gyroscope, the switches PH1 and PH2 are closed, the switch PH3 is opened, the self-excitation starting loop works normally, and the closed-loop driving loop is disconnected; after the gyroscope resonates, the switches PH1 and PH2 are opened, the switch PH3 is closed, the self-excitation starting loop is disconnected, and the closed-loop driving loop works normally.

[0011] Further, the circuit further comprises a clock phase-locked loop circuit, the output of the frequency selection filter is connected to the input of the clock phase-locked loop circuit in addition to the phase-shifting circuit in the self-excitation starting loop, so as to provide a reference frequency signal for the clock phase-locked loop circuit, and the clock phase-locked loop circuit is used to provide a system clock.

[0012] Further, the center frequency of the frequency selection filter, the phase shift of the phase-shifting circuit, the bandwidth of the loop filter and the main frequency of the phase-locked loop are all adjustable designs, and are controlled in coordination through the same adjustment control word; the adjustment control word is composed of two parts, one part is an adaptive adjustment control word automatically generated according to the resonant frequency of the gyro head, and the other part is configured through a register; the adjustment control word is generated by an adaptive adjustment control word generation circuit.

[0013] Further, the adaptive adjustment control word generation circuit comprises a current source I1, a variable capacitor C1, a fixed capacitor C2, a variable resistor R1, a switch network, a comparator and a counter; the switch network comprises switches CLK1, CLK2, CLK3 and CLK1N.

[0014] One end of the current source I1 is connected to a power supply voltage, and the other end is connected to the common end of the switches CLK1 and CLK1N, and is used to provide a charging current; the switch network is used to close and open the charging and discharging path, CLK1 is the charging switch of the variable capacitor C1, and CLK2 is the discharging switch of the variable capacitor C1; one end of the variable capacitor C1 is connected to the ground, and the other end is connected to the negative input end of the comparator, and is used to adjust the charging and discharging time constant and change the voltage value of the negative input end of the comparator; one end of the fixed capacitor C2 is connected to the ground, and the other end is connected to the positive input end of the comparator, and is used to preset the charging and discharging time constant of the positive input end of the comparator together with the variable resistor R1; one end of the variable resistor R1 is connected to the ground, and the other end is connected to the common end of the switches CLK3 and CLK1N, and the resistance value of the variable resistor R1 can be configured through a register, and the basis for the configuration is a preset time constant, and the preset time constant is designed according to the resonant frequency of the gyro head; because the resonant frequencies of different gyro heads have certain differences, R1 is designed as an adjustable resistor; the output signal of the comparator is connected to the input of the counter, the counting clock of the counter is CLK3N, and the N-bit digital code value D[N-1:0] output by the counter controls the variable capacitor C1.

[0015] Further, at the beginning of the circuit power, the initial state of the adjustable resistance and capacitance in the frequency selection filter, the phase shift circuit and the loop filter, and the charging current of the oscillator in the phase-locked loop is configured by the register; then the adaptive adjustment control word generation circuit is started, the preset time constant of the adaptive adjustment control word generation circuit is designed according to the resonant frequency of the gyro table head; the adaptive adjustment control word adjusts the adjustable resistance of the frequency selection filter, the phase shift circuit and the loop filter, and the charging current of the oscillator; after the adaptive adjustment is completed, the adjustable capacitance of the frequency selection filter, the phase shift circuit and the loop filter, and the adjustment current of the oscillator are fine-tuned through the register.

[0016] Further, the adaptive adjustment control word D[N-1:0] is output to the flip-flop group DFC1, the control clock of the flip-flop group DFC1 is the same as the clock CLK3N of the counter in the adaptive adjustment control word generation circuit; the output of the flip-flop group DFC1 is connected to the 1st input end of the two-way selection switch MUX1, the 0th input end of the two-way selection switch MUX1 is connected to the control word provided by the register regA[N-1:0]; regA[N] is the switch control signal of the two-way selection switch MUX1, when regA[N] is 0, the 0th input end signal is selected, when regA[N] is 1, the 1st input end signal is selected; the output Z1[N-1:0] of the two-way selection switch MUX1 is used to adjust the adjustable resistance of the loop filter; the adjustable capacitance of the loop filter is configured by the register regA1[N-1:0].

[0017] Further, the adaptive adjustment control word D[N-1:0] is output to the flip-flop group DFC2, the control clock of the flip-flop group DFC2 is the same as the clock CLK3N of the counter in the adaptive adjustment control word generation circuit; the output of the flip-flop group DFC2 is connected to the 1st input end of the two-way selection switch MUX2, the 0th input end of the two-way selection switch MUX2 is connected to the control word provided by the register regB[N-1:0]; regB[N] is the switch control signal of the two-way selection switch MUX2, when regB[N] is 0, the 0th input end signal is selected, when regB[N] is 1, the 1st input end signal is selected; the output Z2[N-1:0] of the two-way selection switch MUX2 is used to adjust the adjustable resistance of the frequency selection filter and the phase shift circuit; the adjustable capacitance of the frequency selection filter and the phase shift circuit is configured by the register regB1[N-1:0].

[0018] Further, the adaptive adjustment control word D[N-1:0] is output to the flip-flop group DFC3, the control clock of the flip-flop group DFC3 is the same as the clock CLK3N of the counter in the adaptive adjustment control word generation circuit; the output of the flip-flop group DFC3 is connected to the 1st input end of the two-way selection switch MUX3, the 0th input end of the two-way selection switch MUX3 is connected to the control word provided by the register regC[N-1:0]; regC[N] is the switch control signal of the two-way selection switch MUX2, when regC[N] is 0, the 0th input end signal is selected, when regC[N] is 1, the 1st input end signal is selected; the output Z3[N-1:0] of the two-way selection switch MUX3 is used for adjusting the charging current I1 of the oscillator in the phase-locked loop; the charging current I2 of the oscillator is configured by the register regC1[N-1:0].

[0019] The present application brings the following beneficial effects compared with the prior art:

[0020] (1) The circuit of the present application adopts the drive mode control technology combining the self-oscillation driving mode and the phase-locked loop driving mode, which not only takes advantage of the fast starting speed of the self-oscillation driving mode, but also avoids the deficiency of the phase-locked loop driving mode that requires pre-setting the initial frequency. The self-oscillation driving mode is used in the starting stage of the gyro meter head, after the gyro meter head starts, the self-oscillation driving loop is disconnected, the driving loop is closed, and the circuit works in the phase-locked loop driving mode of AGC-PLL. Because the meter head is in the resonant state at this time, the resonant frequency of the meter head is the initial frequency of the PLL phase control circuit, so the driving loop can quickly realize stable frequency and amplitude oscillation.

[0021] (2) Due to the limitations of MEMS processing technology and other factors, there will be some defects, errors and inconsistencies in the processing of MEMS gyro meter heads, which will directly affect the precision and consistency of the gyro, so it is necessary to compensate and adjust it. The circuit compensation of the gyro meter head structure process deviation is a good solution, and the common adjustment methods mainly include fuse adjustment, Zener breakdown adjustment (also known as anti-fuse adjustment) and laser trimming, etc. The OTP (one-time programmable) adjustment method generally needs to go through multiple links such as testing, trial writing, burning, and retesting for each different parameter, which has a very large time cost and is not conducive to engineering. The circuit of the present application adopts the adjustment mode combining adaptive adjustment and register adjustment, which can quickly configure each key parameter for the problem of different resonant frequencies of different gyro meter heads, so as to make the driving loop quickly track the resonant frequency of the gyro meter head and realize stable frequency and amplitude oscillation. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a structure diagram of a MEMS gyro driving mode control circuit of the present application;

[0023] Figure 2 is a self-excitation start-up loop structure diagram of the present application;

[0024] Figure 3 is a closed loop driving loop structure diagram of the present application;

[0025] Figure 4 is a self-adaptive adjustment control word generation circuit structure diagram of the present application;

[0026] Figure 5 is an adjustment mode structure diagram of the present application combining self-adaptive adjustment with register adjustment. DETAILED DESCRIPTION

[0027] The present application provides a MEMS gyroscope driving mode control circuit design scheme. The circuit adopts a driving mode control technology combining a self-excitation oscillation driving mode and a phase-locked loop driving mode. The self-excitation oscillation driving mode has the advantage of fast start-up speed, and the phase-locked loop driving mode avoids the deficiency of needing to set an initial frequency in advance. The self-excitation oscillation driving mode is used in the start-up stage of the gyroscope meter head. After the self-excitation start-up circuit excites the gyroscope meter head to start up, the self-excitation start-up loop is automatically disconnected, the driving loop based on the AGC-PLL driving mode is closed, and the circuit works in the phase-locked loop driving mode based on the AGC-PLL. Because the meter head is in a resonant state at this time, the PLL phase control circuit directly uses the resonant frequency of the gyroscope as the initial frequency, without needing to set the initial frequency in advance, so that the driving loop quickly realizes frequency and amplitude stabilization oscillation. Meanwhile, the resonant signal of the meter head is used as the reference frequency signal of the clock phase-locked loop for generating a system clock and realizing system synchronization.

[0028] As shown in Figure 1 , Figure 2 , Figure 3 is a MEMS gyroscope driving mode control circuit structure diagram of the present application. The circuit contains two parts of a self-excitation start-up loop and a driving loop. The self-excitation start-up loop includes main circuit modules of a CV conversion circuit, a frequency selection filter, a phase shift circuit, a low-pass filter, and a driving circuit. The driving loop includes main circuit modules of a CV conversion circuit, an ADC, a digital filter, an AGC amplitude control circuit, a PLL phase control circuit, a multiplier, a DAC, a loop filter, and a driving circuit.

[0029] The detection electrode of the MEMS gyro meter head driving mode is connected to the input end of the CV conversion circuit, the output end of the CV conversion circuit is simultaneously connected to the input end of the frequency selection filter in the self-excitation starting loop and the input end of the ADC in the driving loop, the output end of the frequency selection filter is connected to the input end of the phase shift circuit through the switch PH1, the output end of the phase shift circuit is connected to the input end of the low pass filter, the output end of the low pass filter is connected to the input end of the driving circuit through the switch PH2, and the output end of the driving circuit is connected to the driving electrode of the meter head. In the driving loop, the output end of the ADC is connected to the input end of the digital filter, the output end of the digital filter is simultaneously connected to the input end of the AGC amplitude control circuit and the input end of the PLL phase control circuit, the output end of the AGC amplitude control circuit and the output end of the PLL phase control circuit are connected to the input end of the multiplier, the output end of the multiplier is connected to the input end of the DAC, the output end of the DAC is connected to the input end of the loop filter, and the output end of the loop filter is connected to the input end of the driving circuit through the switch PH3. In the starting stage of the gyro, the switches PH1 and PH2 are closed, the switch PH3 is disconnected, the self-excitation starting loop normally works, and the driving loop is disconnected; after the gyro resonates, the switches PH1 and PH2 are disconnected, the switch PH3 is closed, the self-excitation starting loop is disconnected, and the driving loop normally works. The output end of the frequency selection filter is connected to the input end of the clock phase-locked loop in addition to the phase shift circuit in the self-excitation starting loop, so as to provide a reference frequency signal for the clock phase-locked loop, and the clock phase-locked loop is used to provide a system clock.

[0030] As shown in Figure 2 The self-excitation starting loop structure diagram of the application is shown in the figure, wherein the MEMS gyro meter head part only gives an equivalent diagram of the driving mode, Cs1 represents the detection capacitor of the driving mode, Cd1 represents the driving capacitor of the driving mode, S1_P and S1_N represent the positive and negative detection electrodes of the driving mode, and DR1_P and DR1_N represent the positive and negative driving electrodes of the driving mode. The circuit part includes the main circuit modules such as the CV conversion circuit, the amplification circuit, the frequency selection filter, the phase shift circuit, the low pass filter and the driving circuit. The detection electrode of the MEMS gyro meter head driving mode is connected to the input end of the CV conversion circuit, the output end of the CV conversion circuit is connected to the input end of the amplification circuit, the output end of the amplification circuit is connected to the input end of the frequency selection filter, the output end of the frequency selection filter is connected to the input end of the phase shift circuit, the output end of the phase shift circuit is connected to the input end of the low pass filter, the output end of the low pass filter is connected to the input end of the driving circuit, and the output end of the driving circuit is connected to the driving electrode of the meter head.

[0031] The CV conversion circuit in the self-excitation starting loop is used to convert the capacitance variation of the MEMS gyroscope into a voltage signal; the signal is amplified by the amplification stage and then sent to the frequency selection filter; the frequency selection filter is responsible for extracting the signal with the same frequency as the resonant frequency of the MEMS gyroscope meter; the phase shift circuit is used to generate a 90° phase shift to offset the 90° phase difference between the driving force and displacement of the MEMS gyroscope meter, so as to meet the condition of self-excitation vibration of the gyroscope; the signal after phase shift is transmitted to the driving circuit after filtering processing, and the driving capacity is enhanced and then output to the driving electrode of the MEMS gyroscope meter. In this way, the MEMS gyroscope meter and the self-excitation starting circuit together constitute a self-excitation loop, so that the meter resonates quickly at its inherent resonant frequency.

[0032] As Figure 3 shown is a closed-loop driving loop structure of the application, wherein the MEMS gyroscope meter, CV conversion and amplification circuit, driving circuit modules are common circuit modules with the self-excitation starting loop structure shown in Figure 2 In addition, the circuit part further includes ADC, digital filter, AGC amplitude control circuit, PLL phase control circuit, multiplier, DAC, loop filter and other circuit modules. The digital filter, AGC amplitude control circuit, PLL phase control circuit, multiplier are all realized in the digital circuit. The input end of the CV conversion circuit is connected with the detection electrode of the driving mode of the MEMS gyroscope meter, the output end of the CV conversion circuit is connected with the input end of the ADC circuit, the output end of the ADC circuit is connected with the input end of the digital filter, the output end of the digital filter is connected with the input end of the AGC amplitude control circuit and the PLL phase control circuit, the output end of the AGC amplitude control circuit and the PLL phase control circuit is connected with the input end of the multiplier, the output end of the multiplier is connected with the input end of the DAC, the output end of the DAC circuit is connected with the input end of the loop filter, the output end of the loop filter is connected with the input end of the driving circuit, and the output end of the driving circuit is connected with the driving electrode of the driving mode of the MEMS gyroscope meter.

[0033] The CV conversion circuit in the closed-loop driving loop is used for converting the capacitance variation of the MEMS gyroscope into a voltage signal; the signal is amplified by an amplification stage and then sent to an ADC circuit; the ADC is used for converting an analog signal into a digital signal; the digital signal is filtered by a digital filter and then the signal representing the driving mode amplitude is output to an AGC amplitude control circuit, and the signal representing the driving mode phase is output to a PLL phase control circuit; the two signals are modulated by a multiplier and then output to a DAC circuit; the DAC circuit is used for converting a digital signal into an analog signal; a loop filter is used for filtering the signal converted from digital to analog; a driving circuit is used for increasing the driving capacity of the signal to provide sufficient driving force for the gyroscope; the AGC amplitude control circuit is used for automatically adjusting the amplitude of the driving voltage to realize accurate control of the driving amplitude; and the PLL phase control circuit is used for tracking and locking the phase of the driving mode resonance frequency and the driving mode detection signal.

[0034] As shown in Figure 4 The adaptive adjustment control word generation circuit structure diagram of the application is shown in the figure. The circuit includes a current source, a variable resistance capacitor, a switch network, a comparator and a counter.

[0035] The current source I1 is connected to the power supply voltage at one end and connected to the common end of switches CLK1 and CLK1N at the other end, and is used for providing a charging current; the switch network is used for closing and opening the charging and discharging path, CLK1 is the charging switch of the variable capacitor C1, and CLK2 is the discharging switch of the variable capacitor C1; the variable capacitor C1 is connected to the ground at one end and connected to the negative input end of the comparator at the other end, and is used for adjusting the charging and discharging time constant and changing the voltage value of the negative input end of the comparator; the fixed capacitor C2 is connected to the ground at one end and connected to the positive input end of the comparator at the other end, and is used together with the variable resistor R1 to preset the charging and discharging time constant of the positive input end of the comparator; the variable resistor R1 is connected to the ground at one end and connected to the common end of CLK3 and CLK1N at the other end, and the resistance value of R1 can be configured through a register, and the basis for the configuration is the preset time constant, which is designed according to the resonance frequency of the gyro head, because the resonance frequencies of different gyro heads have certain differences, so R1 is designed as an adjustable resistor; the output signal of the comparator is connected to the input of the counter, the counting clock of the counter is CLK3N, and the N-bit digital code value D[N-1:0] output by the counter controls the variable capacitor C1.

[0036] In the high level stage of CLK1N and CLK3, the current source I1 charges the positive input of the comparator and maintains to the end of each comparison counting period; in the high level stage of CLK2, the negative input and output of the comparator are reset and cleared, and the output of the counter remains unchanged; in the high level stage of CLK1 and the low level stage of CLK2, the negative input of the comparator is charged and the comparison result is outputted; when the output of the comparator is low, the counter is incremented by 1, and the capacitance value is increased; when the time constant reaches the preset value, the counter stops counting, and the N-bit digital code value D[N-1:0] outputted by the counter is the control word after adjustment.

[0037] As shown in Figure 5 is a structure diagram of the adjustment mode combining adaptive adjustment and register adjustment. The adaptive adjustment control word D[N-1:0] is outputted to the flip-flop groups DFC1, DFC2 and DFC3, and the control clock of the three flip-flop groups is the same as the clock CLK3N of the counter in the adaptive adjustment control word generation circuit.

[0038] The output of DFC1 is connected to the No. 1 input of the two-way selection switch MUX1, the No. 0 input of the two-way selection switch MUX1 is connected to the control word provided by the register regA[N-1:0]; regA[N] is the switch control signal of the two-way selection switch MUX1, when regA[N] is 0, the No. 0 input signal is selected, and when regA[N] is 1, the No. 1 input signal is selected; the output Z1[N-1:0] of the two-way selection switch MUX1 is used to adjust the adjustable resistance of the loop filter; the adjustable capacitance of the loop filter is configured by the register regA1[N-1:0].

[0039] The output of DFC2 is connected to the No. 1 input of the two-way selection switch MUX2, the No. 0 input of the two-way selection switch MUX2 is connected to the control word provided by the register regB[N-1:0]; regB[N] is the switch control signal of the two-way selection switch MUX2, when regB[N] is 0, the No. 0 input signal is selected, and when regB[N] is 1, the No. 1 input signal is selected; the output Z2[N-1:0] of the two-way selection switch MUX2 is used to adjust the adjustable resistance of the frequency selection filter and the phase shift circuit; the adjustable capacitance of the frequency selection filter and the phase shift circuit is configured by the register regB1[N-1:0].

[0040] The output of the DFC3 is connected to the 1st input of the 2-to-1 multiplexer MUX3, and the 0th input of the 2-to-1 multiplexer MUX3 is connected to the control word provided by the register regC[N-1:0]; regC[N] is the switch control signal of the 2-to-1 multiplexer MUX2, when regC[N] is 0, the 0th input signal is selected, and when regC[N] is 1, the 1st input signal is selected; the output Z3[N-1:0] of the 2-to-1 multiplexer MUX3 is used to adjust the charging current I1 of the oscillator in the phase-locked loop; the charging current I2 of the oscillator is configured by the register regC1[N-1:0].

[0041] The application adopts a driving mode control technology combining a self-excited oscillation driving mode with a phase-locked loop driving mode. The self-excited oscillation driving mode is used in the starting stage of the gyro meter head, and the resonant characteristics of the MEMS gyro meter head are fully utilized to make the gyro meter head start quickly. After the gyro meter head starts, the self-excited starting loop is disconnected, the driving loop is closed, and the circuit works in the phase-locked loop driving mode. Because the meter head is in the resonant state before entering the phase-locked loop driving mode, the initial frequency signal does not need to be set for the phase-locked loop phase control circuit, and the driving loop can quickly realize the stable frequency and amplitude oscillation. The driving mode control technology combining the two driving modes has the advantages of the self-excited oscillation driving mode and avoids the deficiency of the phase-locked loop driving mode. Meanwhile, the circuit of the application adopts an adjustment mode combining adaptive adjustment with register adjustment, and can quickly configure each key parameter aiming at the problem that the resonant frequencies of different gyro meter heads are different, so that the driving loop can quickly track the resonant frequency of the gyro meter head and realize the stable frequency and amplitude oscillation.

[0042] The part not described in detail in the application is common knowledge for those skilled in the art.

Claims

1. A MEMS gyroscope driving mode control circuit, characterized in that: The driving mode control method combines self-excited oscillation driving mode and phase-locked loop driving mode, including CV conversion circuit, frequency selection filter, phase shifting circuit, low-pass filter, driving circuit, ADC, DAC, digital filter, AGC amplitude control circuit and PLL phase control circuit; The self-excited startup loop consists of a CV conversion circuit, a frequency selective filter, a phase shifting circuit, a low-pass filter, and a driving circuit. In this loop, the input of the CV conversion circuit is connected to the detection electrode of the MEMS gyroscope's driving mode. The CV conversion circuit converts the capacitance change of the MEMS gyroscope into a voltage signal and amplifies it. The amplified signal is then sent to the frequency selective filter. The frequency selective filter extracts the signal that resonates with the MEMS gyroscope's resonant frequency and sends it to the phase shifting circuit. The phase shifting circuit generates a 90° phase shift to compensate for the 90° phase difference between the driving force and displacement of the MEMS gyroscope. After being filtered by the low-pass filter, the phase-shifted signal is transmitted to the driving circuit. The enhanced driving capability allows the signal to be output to the driving electrode of the MEMS gyroscope, enabling the MEMS gyroscope to quickly resonate at its inherent resonant frequency. A closed-loop drive loop is composed of a CV conversion circuit, an ADC, a digital filter, an AGC amplitude control circuit, a PLL phase control circuit, a DAC, a loop filter, and a drive circuit. In this closed-loop drive loop, the CV conversion circuit converts the capacitance change of the MEMS gyroscope into a voltage signal and amplifies it. The amplified signal is then sent to the ADC circuit to convert the analog signal into a digital signal. The digital signal is then filtered by the digital filter, outputting a signal representing the amplitude of the drive mode to the AGC amplitude control circuit, and simultaneously outputting a signal representing the phase of the drive mode to the PLL phase control circuit. These two signals are modulated by a multiplier and then output to the DAC circuit. The DAC circuit converts the digital signal into an analog signal, filters it, and then sends it to the drive circuit. The drive circuit increases the driving capability of the signal to provide sufficient driving force to the gyroscope. The AGC amplitude control circuit automatically adjusts the amplitude of the drive voltage to achieve precise control of the drive amplitude. The PLL phase control circuit tracks and locks the resonant frequency of the drive mode and the phase of the drive mode detection signal. The self-excited oscillation drive mode is used in the oscillation stage of the gyroscope instrument head. After the self-excited start-up loop excites the gyroscope instrument head to start oscillating, the self-excited start-up loop is automatically disconnected, and the closed-loop drive loop based on the AGC-PLL drive mode is closed. The circuit works in the phase-locked loop drive mode based on AGC-PLL. At this time, the instrument head is already in the resonant state. The PLL phase control circuit directly uses the resonant frequency of the gyroscope as the initial frequency, without the need to pre-set the initial frequency, so that the closed-loop drive loop can quickly achieve stable frequency and amplitude oscillation. At the same time, the resonant signal of the instrument head is used as the reference frequency signal of the clock phase-locked loop to generate the system clock and realize system synchronization.

2. The MEMS gyroscope drive mode control circuit according to claim 1, characterized in that: It also includes switches PH1, PH2 and PH3; switch PH1 is set between the frequency selective filter and the phase shift circuit, switch PH2 is set between the low-pass filter and the drive circuit, and switch PH3 is set between the drive circuit and the loop filter.

3. The MEMS gyroscope drive mode control circuit according to claim 2, characterized in that: During the startup phase of the gyroscope, switches PH1 and PH2 are closed, switch PH3 is open, the self-excited startup loop works normally, and the closed-loop drive loop is disconnected; after the gyroscope resonates, switches PH1 and PH2 are open, switch PH3 is closed, the self-excited startup loop is disconnected, and the closed-loop drive loop works normally.

4. A MEMS gyroscope drive mode control circuit according to any one of claims 1 to 3, characterized in that: It also includes a clock phase-locked loop circuit. In addition to connecting the phase-shifting circuit in the self-excited startup loop to the output of the frequency selection filter, it is also connected to the input of the clock phase-locked loop circuit to provide a reference frequency signal for the clock phase-locked loop circuit. The clock phase-locked loop circuit is used to provide the system clock.

5. The MEMS gyroscope drive mode control circuit according to claim 4, characterized in that: The center frequency of the frequency-selective filter, the phase shift of the phase-shifting circuit, the bandwidth of the loop filter, and the main frequency of the phase-locked loop are all adjustable and are controlled collaboratively by the same adjustment control word. The adjustment control word consists of two parts: one part is an adaptive adjustment control word automatically generated based on the resonant frequency of the gyroscope head, and the other part is configured through a register. The adjustment control word is generated by an adaptive adjustment control word generation circuit.

6. The MEMS gyroscope drive mode control circuit according to claim 5, characterized in that: The adaptive adjustment control word generation circuit includes a current source I1, a variable capacitor C1, a fixed capacitor C2, a variable resistor R1, a switching network, a comparator, and a counter; the switching network includes switches CLK1, CLK2, CLK3, and CLK1N. One end of current source I1 is connected to the power supply voltage, and the other end is connected to the common terminal of switches CLK1 and CLK1N to provide charging current. The switching network is used to close and open the charging and discharging paths. CLK1 is the charging switch for variable capacitor C1, and CLK2 is the discharging switch for variable capacitor C1. One end of variable capacitor C1 is grounded, and the other end is connected to the negative input terminal of the comparator to adjust the charging and discharging time constant, thus changing the voltage value at the negative input terminal of the comparator. One end of fixed capacitor C2 is grounded, and the other end is connected to the positive input terminal of the comparator, used together with variable resistor R1 to preset the charging and discharging time constant at the positive input terminal of the comparator. One end of variable resistor R1 is grounded, and the other end is connected to the common terminal of switches CLK3 and CLK1N. The resistance value of variable resistor R1 can be configured through a register based on the preset time constant, which is designed according to the resonant frequency of the gyroscope. Because the resonant frequencies of different gyroscopes vary, R1 is designed as an adjustable resistor. The output signal of the comparator is connected to the input of the counter. The counter's counting clock is CLK3N, and the counter outputs an N-bit digital code value. D [N-1:0] controls the variable capacitor C1.

7. The MEMS gyroscope drive mode control circuit according to claim 6, characterized in that: When the circuit is powered on, the register first configures the initial state of the frequency selection filter, the phase shift circuit and the adjustable resistors and capacitors in the loop filter, as well as the charging current of the oscillator in the phase-locked loop; then the adaptive adjustment control word generation circuit is started, and the preset time constant of the adaptive adjustment control word generation circuit is designed according to the resonant frequency of the gyroscope. The adaptive adjustment control word adjusts the adjustable resistors of the frequency selection filter, phase shift circuit, and loop filter, as well as the charging current of the oscillator. After the adaptive adjustment is completed, the adjustable capacitors of the frequency selection filter, phase shift circuit, and loop filter, as well as the adjustment current of the oscillator, are fine-tuned through the register.

8. The MEMS gyroscope drive mode control circuit according to claim 6, characterized in that: The adaptive adjustment control word D[N-1:0] is output to the flip-flop group DFC1. The control clock of the flip-flop group DFC1 is the same as the clock CLK3N of the counter in the adaptive adjustment control word generation circuit. The output of the flip-flop group DFC1 is connected to input terminal 1 of the 2-to-1 selector switch MUX1. Input terminal 0 of the 2-to-1 selector switch MUX1 is connected to the control word provided by the register regA[N-1:0]. regA[N] is the switching control signal of the 2-to-1 selector switch MUX1. When regA[N] is 0, the signal of input terminal 0 is selected. When regA[N] is 1, the signal of input terminal 1 is selected. The output Z1[N-1:0] of the 2-to-1 selector switch MUX1 is used to adjust the adjustable resistor of the loop filter. The adjustable capacitor of the loop filter is configured by the register regA1[N-1:0].

9. A MEMS gyroscope driving mode control circuit according to claim 6, characterized in that: The adaptive adjustment control word D[N-1:0] is output to the flip-flop group DFC2. The control clock of the flip-flop group DFC2 is the same as the clock CLK3N of the counter in the adaptive adjustment control word generation circuit. The output of the flip-flop group DFC2 is connected to input terminal 1 of the 2-to-1 selector switch MUX2. Input terminal 0 of the 2-to-1 selector switch MUX2 is connected to the control word provided by the register regB[N-1:0]. regB[N] is the switching control signal of the 2-to-1 selector switch MUX2. When regB[N] is 0, the signal at input terminal 0 is selected. When regB[N] is 1, the signal at input terminal 1 is selected. The output Z2[N-1:0] of the 2-to-1 selector switch MUX2 is used to adjust the adjustable resistors of the frequency selection filter and the phase shift circuit. The adjustable capacitors of the frequency selection filter and the phase shift circuit are configured by the register regB1[N-1:0].

10. A MEMS gyroscope driving mode control circuit according to claim 6, characterized in that: The adaptive adjustment control word D[N-1:0] is output to the flip-flop group DFC3. The control clock of the flip-flop group DFC3 is the same as the clock CLK3N of the counter in the adaptive adjustment control word generation circuit. The output of the flip-flop group DFC3 is connected to input terminal 1 of the 2-to-1 selector switch MUX3. Input terminal 0 of the 2-to-1 selector switch MUX3 is connected to the control word provided by the register regC[N-1:0]. regC[N] is the switching control signal of the 2-to-1 selector switch MUX2. When regC[N] is 0, the signal of input terminal 0 is selected. When regC[N] is 1, the signal of input terminal 1 is selected. The output Z3[N-1:0] of the 2-to-1 selector switch MUX3 is used to adjust the charging current I1 of the oscillator in the phase-locked loop. The charging current I2 of the oscillator is configured by the register regC1[N-1:0].

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