CN117200701A - MEMS oscillator and control method thereof - Google Patents

Abstract

The application provides a MEMS oscillator and a control method thereof, comprising the following steps: the device comprises an MEMS resonator, a bias voltage generating module and an oscillation maintaining module; the bias voltage generation module is used for generating a preset bias voltage; the oscillation maintaining module receives an oscillation signal in the MEMS resonator, amplifies the oscillation signal to obtain a clock signal, and takes the oscillation signal after gain amplification as a driving voltage; the MEMS resonator generates an oscillation signal based on the driving voltage under the action of the bias voltage; the bias voltage is configured to be a first bias voltage within the preset time when the MEMS oscillator starts to vibrate, and is configured to be a second bias voltage after the preset time is over; the first bias voltage is greater than the second bias voltage, and the phase noise of the MEMS resonator corresponding to the first bias voltage is greater than the phase noise of the MEMS resonator corresponding to the second bias voltage. According to the application, by setting bias voltages with different magnitudes on the vibrators in the MEMS resonator, the MEMS resonator is ensured to be capable of achieving quick vibration starting so as to reduce vibration starting time.

Description

MEMS oscillator and control method thereof

Technical Field

The application relates to the field of circuit manufacturing, in particular to an MEMS oscillator and a control method thereof.

Background

Microelectromechanical systems (Micro-Electro-Mechanical System, MEMS) resonators are devices that vibrate a mechanical structure at its natural frequency, and the MEMS resonator is integrated with an oscillating circuit to form a MEMS oscillator. The oscillator based on the MEMS resonator not only has high-frequency and high-quality factors, but also has the manufacturing process compatible with IC technology, and can realize the integration of the MEMS resonator and the oscillating circuit on the same chip, thereby promoting the miniaturization of the whole system. In recent years, MEMS resonator based oscillators have attracted more and more attention.

The oscillating circuit in the MEMS oscillator applies the driving voltage to the resonator to drive the resonator to vibrate, however, the existing MEMS oscillator usually needs a long time to normally vibrate after the driving voltage is applied to the resonator due to the influence of factors such as self resistance and phase noise, and the vibration starting time is overlong.

Based on the above, the application provides a MEMS oscillator and a control method thereof, which are used for solving the problem that the MEMS oscillator needs a long time to normally start vibrating.

It should be noted that the foregoing description of the background art is only for the purpose of providing a clear and complete description of the technical solution of the present application and is presented for the convenience of understanding by those skilled in the art. The above-described solutions are not considered to be known to the person skilled in the art simply because they are set forth in the background of the application section.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, an object of the present application is to provide a MEMS oscillator and a control method thereof, which are used for solving the problem of longer starting time of the MEMS oscillator in the prior art.

To achieve the above and other related objects, a first aspect of the present application provides a MEMS oscillator, comprising: a MEMS resonator for vibrating to provide an oscillation signal, a bias voltage generation module for providing a bias voltage to the MEMS resonator, and an oscillation maintenance module for maintaining the MEMS resonator vibrating and for generating a frequency signal; the bias voltage generating module is configured to provide a first bias voltage from a first moment when the MEMS resonator starts vibrating up to a second moment, and configured to provide a second bias voltage from the second moment later; the second moment is determined by an oscillation signal output by the MEMS resonator, the first bias voltage is greater than the second bias voltage, and phase noise of the MEMS resonator corresponding to the first bias voltage is greater than phase noise of the MEMS resonator corresponding to the second bias voltage.

Optionally, the second bias voltage is set to a bias voltage value corresponding to when the phase noise of the MEMS resonator is minimum.

Optionally, the MEMS resonator has a resonance point capable of vibrating stably, and the frequency corresponding to the resonance point is a preset oscillation frequency; and from the first moment to the second moment, the frequency of the oscillation signal output by the MEMS resonator reaches the preset oscillation frequency.

Optionally, the bias voltage generating module includes a first voltage generating unit, a second voltage generating unit, a first branch switch, a second branch switch and a switch control unit; the switch control unit is respectively connected with the control ends of the first branch switch and the second branch switch and is used for generating a switch control signal to respectively control the opening or closing of the first branch switch and the second branch switch; the output end of the first voltage generating unit is electrically connected with the MEMS resonator through the first branch switch; the output end of the second voltage generating unit is electrically connected with the MEMS resonator through the second branch switch.

Optionally, the bias voltage generating module comprises a first voltage generating unit, a second voltage generating unit, a selection switch and a switch control unit; the switch control unit is connected with the control end of the selection switch and is used for generating a selection switch control signal to adjust a switch node communicated with the selection switch; the output end of the first voltage generating unit is connected with a switch node and is electrically connected with the MEMS resonator through the selection switch; the output end of the second voltage generating unit is connected with another switch node and is electrically connected with the MEMS resonator through the selection switch.

Optionally, the first voltage generating unit includes a first charge pump, the second voltage generating unit includes a second charge pump, and one of the first charge pump and the second charge pump is controlled to be connected to the MEMS resonator through the switch control unit to provide a bias voltage, wherein the bias voltage provided by the first charge pump is the first bias voltage; the bias voltage provided by the second charge pump is the second bias voltage.

Optionally, the bias voltage generating module includes a third charge pump, a first capacitor, a second capacitor, a connection switch and a connection switch control unit; the connecting switch control unit is connected with the control end of the connecting switch and is used for generating a connecting switch control signal and controlling the connecting switch to be opened or closed; the upper polar plate of the first capacitor is connected with the output end of the third charge pump, and the lower polar plate is grounded; the upper polar plate of the second capacitor is connected with the upper polar plate of the first capacitor through the connecting switch, and the lower polar plate is grounded; the output end of the third charge pump is used as the output end of the bias voltage generating module.

Optionally, the MEMS resonator has a resonance point capable of vibrating stably, and the frequency corresponding to the resonance point is a preset oscillation frequency, and the time interval between the first time and the second time is a preset time, where the preset time satisfies: 0<t < T, wherein T is denoted as the preset time, 0 is denoted as the first moment when the MEMS resonator starts to vibrate, and T is set as the time required by the MEMS resonator to reach a preset vibration frequency under the action of the first bias voltage.

To achieve the above and other related objects, a second aspect of the present application provides a control method of a MEMS oscillator including a MEMS resonator for vibrating to provide an oscillation signal, a bias voltage generating module for providing a bias voltage to the MEMS resonator, and an oscillation maintaining module for providing a driving signal to maintain the MEMS resonator vibrating. The control method of the MEMS oscillator comprises the following steps: applying the bias voltage and the drive voltage to the MEMS resonator such that the MEMS resonator oscillates under the bias voltage and the drive voltage to generate the oscillation signal; the applied bias voltage is a first bias voltage from a first moment when the MEMS resonator starts vibrating until a second moment, and the applied bias voltage is a second bias voltage from the second moment; the second moment is determined by an oscillation signal output by the MEMS resonator, the first bias voltage is greater than the second bias voltage, and phase noise of the MEMS resonator corresponding to the first bias voltage is greater than phase noise of the MEMS resonator corresponding to the second bias voltage.

Optionally, the MEMS resonator has a resonance point capable of vibrating stably, and the frequency corresponding to the resonance point is a preset oscillation frequency, and the time interval between the first time and the second time is a preset time, where the preset time satisfies: t is larger than or equal to T, wherein T is expressed as the preset time, and T is set as the time required by the MEMS resonator to reach the preset oscillation frequency under the action of the first bias voltage.

As described above, the MEMS oscillator and the control method thereof of the present application have the following advantageous effects:

1. according to the MEMS oscillator and the control method, bias voltages with different magnitudes are applied to the vibrators in the MEMS oscillator, so that the MEMS oscillator is guaranteed to achieve quick starting so as to reduce starting time, and phase noise can be reduced after normal starting, so that the MEMS oscillator has better performance.

2. The MEMS oscillator is simple in structure, and the control method of the MEMS oscillator is simple and convenient to operate and can be well applied to the field of circuit manufacturing.

Drawings

Fig. 1 shows a schematic structure of a MEMS oscillator according to the present application.

Fig. 2A and fig. 2B are schematic structural diagrams of bias voltage generating modules according to different embodiments of the application.

Fig. 3 is a schematic diagram of a bias voltage generating module according to another embodiment of the application.

Fig. 4 is a schematic structural diagram of a MEMS resonator according to the present application.

Fig. 5 is a schematic diagram showing the structure of the oscillation maintaining module according to the present application.

FIG. 6 is a graph showing the relationship between bias voltage and phase noise according to the present application.

FIG. 7 is a schematic diagram showing the bias voltage variation with time according to the present application.

Fig. 8 shows the oscillation frequency of the present application as a function of time.

Description of element reference numerals

1 MEMS oscillator

11 MEMS resonator

111. First electrode

112. Second electrode

113. Vibrator(s)

12. Bias voltage generating module

121. First voltage generating unit

1211. First charge pump

122. Second voltage generating unit

1221. Second charge pump

123. Switch control unit

124. Third charge pump

125. Connection switch control unit

13. Oscillation maintaining module

131. Transimpedance amplifier

132. Level shifter

Detailed Description

Other advantages and effects of the present application will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present application with reference to specific examples. The application may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present application.

Please refer to fig. 1-8. It should be noted that, the illustrations provided in the present embodiment merely illustrate the basic concept of the present application by way of illustration, and only the components related to the present application are shown in the drawings and are not drawn according to the number, shape and size of the components in actual implementation, and the form, number and proportion of the components in actual implementation may be arbitrarily changed, and the layout of the components may be more complex.

As shown in fig. 1, the present embodiment provides a MEMS oscillator 1, the MEMS oscillator 1 including a MEMS resonator 11, a bias voltage generating module 12, and an oscillation maintaining module 13.

Wherein the MEMS resonator 11 may be used for vibration to provide an oscillating signal. The bias voltage generation module 12 may be used to generate a preset bias voltage and provide it to the MEMS resonator 11. The oscillation maintaining module 13 may be used to receive the oscillation signal and provide a driving signal to the MEMS resonator 11 to maintain the MEMS resonator 11 to vibrate. The oscillation maintaining module 13 may also be used to generate and output a frequency signal. It will be appreciated that the MEMS resonator 11 may be vibrated by the bias voltage and the drive signal to generate an oscillating signal.

In this embodiment, the preset bias voltage may be set to different magnitudes over time. Specifically, referring to fig. 7, from a first time t0 when the MEMS resonator 11 starts vibrating, the bias voltage generating module 12 may be configured to supply the first bias voltage Vb1 up to a second time t1, and from the second time t1, the bias voltage generating module 12 may be configured to supply the second bias voltage Vb2. The first bias voltage Vb1 is greater than the second bias voltage Vb2, so as to accelerate the oscillation starting time of the MEMS oscillator 1. And, the phase noise of the MEMS resonator 11 corresponding to the first bias voltage Vb1 is greater than the phase noise of the MEMS resonator 11 corresponding to the second bias voltage Vb2, so as to ensure that the phase noise of the MEMS resonator 11 is smaller after the first bias voltage Vb1 is converted into the second bias voltage Vb2, so that the working performance of the MEMS resonator 11 is better.

In the present embodiment, the second bias voltage Vb2 is set to a bias voltage value corresponding to when the phase noise of the MEMS resonator 11 is minimum, for example, referring to fig. 6, when the bias voltage is the second bias voltage Vb2, the phase noise is minimum; at this time, the subsequent MEMS resonator 11 can be ensured to work in a better working state.

In a first example, referring to fig. 2A, the bias voltage generating module 12 may include a first voltage generating unit 121 and a second voltage generating unit 122.

In the embodiment of the application, the first voltage generating unit 121 and the second voltage generating unit 122 are respectively located in a circuit branch and are electrically connected to the MEMS resonator 11 through a switch. The circuit branch where the first voltage generating unit 121 is located is a first branch, and the circuit branch where the second voltage generating unit 122 is located is a second branch.

In this embodiment, the bias voltage generating module 12 may include a switch control unit 123, and the switch control unit 123 may control the on/off of the switches on the first branch and the second branch, respectively. When the switch on the first branch is closed, the first voltage generating unit 121 may be connected to a circuit to be electrically connected to the MEMS resonator 11; in this case, the first voltage generation unit 121 may provide the MEMS resonator 11 with a bias voltage. When the switch on the first branch is opened, the connection path of the first voltage generating unit 121 and the MEMS resonator 11 is opened, and the signal generated by the first voltage generating unit 121 is difficult to output to the MEMS resonator 11. Likewise, when the switch on the second branch is closed, the second voltage generation unit 122 may be electrically connected to the MEMS resonator 11 by an access circuit; in this case, the second voltage generation unit 122 may provide the MEMS resonator 11 with a bias voltage. When the switch on the second branch is opened, the second voltage generating unit 122 is disconnected from the connection path of the MEMS resonator 11, and the signal generated by the second voltage generating unit 122 is difficult to output to the MEMS resonator 11.

In some embodiments, when the MEMS oscillator 1 is in operation, the switch control unit 123 may select only one of the first voltage generation unit 121 and the second voltage generation unit 122 to be electrically connected to the MEMS resonator 11 at the same time to provide the MEMS resonator 11 with the bias voltage. For example, during operation of the MEMS oscillator 1, the switch control unit 123 may control the voltage generating unit of the switching-in circuit, for example, at a first time t0 when the MEMS resonator 11 starts vibrating, the switch control unit 123 may control the switch on the first branch to be closed, and the switch on the second branch to be opened, so that the first voltage generating unit 121 switches in circuit to provide the MEMS resonator 11 with the bias voltage until a second time t1. After the second time t1, the switch control unit 123 may control the switch on the second branch to be closed, and the switch on the first branch to be opened, so that the second voltage generating unit 122 is connected to the circuit to provide the bias voltage for the MEMS resonator 11. Wherein the bias voltage provided by the first voltage generating unit 121 is a first bias voltage Vb1; the bias voltage supplied from the second voltage generating unit 122 is a second bias voltage Vb2.

Specifically, referring to fig. 1 and 2A, the bias voltage generating module 12 includes a first voltage generating unit 121, a second voltage generating unit 122, a first branch switch S1, a second branch switch S2, and a switch control unit 123. The switch control unit 123 is connected to the control ends of the first and second branch switches S1 and S2, respectively, and is configured to generate a switch control signal to control the opening or closing of the first and second branch switches S1 and S2, respectively. The first voltage generating unit 121 is located in the first branch, and an output end of the first voltage generating unit 121 is electrically connected to the MEMS resonator 11 through the first branch switch S1. The second voltage generating unit 122 is located in the second branch, and an output end of the second voltage generating unit 122 is electrically connected to the MEMS resonator 11 through the second branch switch S2. Wherein the bias voltage provided by the first voltage generating unit 121 is a first bias voltage Vb1; the bias voltage supplied from the second voltage generating unit 122 is a second bias voltage Vb2.

Alternatively, referring to fig. 2B, the switches on the first and second branches in the bias voltage generating module 12 may share a selection switch S3. The selection switch S3 may have a plurality of switching nodes. The output end of the first voltage generating unit 121 is connected to a switching node and is electrically connected to the MEMS resonator 11 through the selection switch S3, and the output end of the second voltage generating unit 122 is connected to another switching node and is electrically connected to the MEMS resonator 11 through the selection switch S3. The switch control unit 123 may be connected to a control terminal of the selection switch, and is configured to generate a selection switch control signal to adjust a switching node of the selection switch, so that the first voltage generating unit 121 or the second voltage generating unit 122 is connected to a circuit and electrically connected to the MEMS resonator 11, so as to provide a bias voltage for the MEMS resonator 11.

In the present embodiment, as shown in fig. 2A and 2B, the first voltage generating unit 121 includes a first charge pump 1211. The second voltage generating unit 122 includes a second charge pump 1221. When the MEMS vibrator 1 is operated, one of the first charge pump 1211 and the second charge pump 1221 is controlled to be connected to a circuit electrically connected to the MEMS resonator 11 via the switch control unit 123 to supply a bias voltage. Wherein the bias voltage provided by the first charge pump 1211 is a first bias voltage Vb1; the bias voltage supplied by the second charge pump 1221 is the second bias voltage Vb2.

It should be noted that, the first voltage generating unit 121 and the second voltage generating unit 122 in the first example may further include a capacitor connected to the charge pump, and the voltage value output by the charge pump may be adjusted by means of an external capacitor, so as to provide a suitable bias voltage for the MEMS resonator 11. Virtually any structure that can provide a certain bias voltage to the MEMS resonator 11 is within the scope of this embodiment.

In a second example, the bias voltage generating module 12 may include a charge pump, and a regulating circuit that is matched with and electrically connected to the charge pump, and the voltage signal output by the charge pump is processed and regulated by the regulating circuit to obtain the required bias voltages, such as the first bias voltage Vb1 and the second bias voltage Vb2.

Specifically, referring to fig. 3, the bias voltage generating module 12 includes a third charge pump 124, a first capacitor C1, a second capacitor C2, a connection switch S4, and a connection switch control unit 125. That is, the adjusting circuit includes a first capacitor C1, a second capacitor C2, a connection switch S4, and a connection switch control unit 125. The connection switch control unit 125 is connected to a control end of the connection switch S4, and is configured to generate a connection switch control signal (also referred to as a switch control signal) and control the connection switch S4 to be opened or closed. The upper polar plate of the first capacitor C1 is connected with the output end of the third charge pump 124, and the lower polar plate is grounded; the upper electrode plate of the second capacitor C2 is connected with the upper electrode plate of the first capacitor C1 through a connecting switch S4, and the lower electrode plate is grounded; the upper plate of the first capacitor C1 (or the output of the third charge pump 124) serves as the output of the bias voltage generating module 12.

During the first time t0 to the second time t1, the connection switch S4 is opened, and after the second time t1, the connection switch S4 is closed; the output bias voltage value is adjusted by the second capacitor C2. Specifically, when the connection switch S4 is not turned on, the first capacitor C1 is electrically connected to the third charge pump 124, and the connection path between the second capacitor C2 and the third charge pump 124 is disconnected, and the charge amount q1=v1×c1 of the circuit is equal to the current bias voltage output by the bias voltage generating module 12, where the bias voltage may be the first bias voltage Vb1; when the connection switch S4 is turned on, the second capacitor C2 and the first capacitor C1 are electrically connected to the third charge pump 124, and the charge amount q2=v2 (c1+c2) of the circuit is equal to the current bias voltage output by the bias voltage generating module 12, where the bias voltage can be adjusted to the second bias voltage Vb2. For a given third charge pump 124, the output charge amounts may be the same, so q1=q2, and it can be known that the first bias voltage Vb1 is greater than the second bias voltage Vb2, and that vb2=vb1×c1/(c1+c2) is satisfied. Thus, the size of Vb2 can be adjusted by adjusting the capacitance value of the second capacitor C2 so as to meet the circuit requirement, thereby better improving the performance of the MEMS oscillator 1. It will be appreciated that the magnitude of Vb2 can also be adjusted to some extent by adjusting the capacitance of the first capacitor C1.

It should be noted that, the bias voltage generating module 12 in the second example may not be provided with the first capacitor C1, directly rely on the capacitor of the internal circuit of the charge pump to adjust the output voltage value, and then adjust the magnitudes of the output first bias voltage Vb1 and the second bias voltage Vb2 through the connection switch S4, so that virtually any structure capable of providing bias voltages with different magnitudes for the MEMS resonator 11 is the protection scope of the present embodiment.

As shown in fig. 4, the MEMS resonator 11 includes a first electrode 111, a second electrode 112, and a vibrator 113 interposed between the first electrode 111 and the second electrode 112, which are disposed opposite to each other; the first electrode 111 is applied with a driving signal (or driving voltage); the vibrator 113 is applied with a bias voltage; the second electrode 112 serves as an output terminal of the MEMS resonator 11, and outputs an oscillation signal.

When the MEMS oscillator 1 operates, a driving signal (such as an ac voltage signal) is applied to the first electrode 111, and a bias voltage (such as a dc voltage signal) is applied to the vibrator 113, so that an electrostatic force is applied between opposite or same charges established on the first electrode 111 and the vibrator 113, the vibrator 113 vibrates back and forth under the driving of the electrostatic force, so that the capacitance between the second electrode 112 and the vibrator 113 changes, so that an ac current signal (such as an oscillation signal) is generated on the second electrode 112, the oscillation maintaining module 13 receives the ac current to amplify (or gain) and convert the ac current into a voltage signal for outputting, and the first electrode 111 receives the voltage signal to maintain the vibrator 113 to vibrate as the driving signal, thereby forming a closed loop system of "electric energy→mechanical kinetic energy→electric energy". Accordingly, the MEMS resonator 11 of the MEMS oscillator 1 can perform physical vibration of a fixed frequency to generate an oscillation signal, i.e., an alternating current signal.

In addition, the oscillation maintaining module 13 may transmit the voltage signal after gain to a subsequent module in the oscillation maintaining module 13 for processing to generate a frequency signal (e.g. a clock signal).

Specifically, as shown in fig. 5, the oscillation maintaining module 13 includes a transimpedance amplifier 131 and a level shifter 132; the input end of the transimpedance amplifier 131 is connected with the second electrode 112 of the MEMS resonator 11 to receive the oscillation signal, the output end of the transimpedance amplifier 131 is electrically connected with the level shifter 132 and the first electrode 111 of the MEMS resonator 11, and the transimpedance amplifier 131 is used for amplifying the gain of the oscillation signal and converting the gain into a voltage signal; the level shifter 132 receives the voltage signal and processes it to output a frequency signal; the first electrode 111 also receives the voltage signal as a driving signal, thereby achieving energy interaction between the oscillation maintaining module 13 and the MEMS resonator 11 to maintain the vibrator 113 to continuously vibrate.

Next, the operation principle of the MEMS oscillator of the present embodiment will be further described, and fig. 6 is a graph showing the relationship between the phase noise of the MEMS oscillator 1 and the bias voltage applied to the vibrator 113. The phase noise varies with the change of the bias voltage, and when the bias voltage is the first bias voltage Vb1, the phase noise is PN1; when the bias voltage is the second bias voltage Vb2, the phase noise is PN2; the phase noise PN1 of the MEMS resonator 11 corresponding to the first bias voltage Vb1 is greater than the phase noise PN2 of the MEMS resonator 11 corresponding to the second bias voltage Vb2, i.e., PN2 < PN1. It will be appreciated that the phase noise reflects the frequency stability of the MEMS oscillator 1, and that the smaller the phase noise, the stronger the frequency stability, i.e. the better the performance, of the MEMS oscillator 1. Thus, by changing the magnitude of the bias voltage, the performance of the MEMS oscillator 1 can be improved. The bias voltage corresponding to the optimum performance of the MEMS oscillator 1 is the bias voltage corresponding to the phase noise minimum value. Therefore, in order to maintain the stable performance of the MEMS oscillator 1, it is preferable to apply the second bias voltage Vb2 to the MEMS resonator 11 so that the phase noise thereof is reduced correspondingly and the system stability is increased.

However, the equivalent resistance Rm of the MEMS oscillator 1 of the MEMS oscillators 1 satisfies:

wherein keff is the elastic coefficient of the vibrator; q is the quality factor; ω0 is the amplitude of the vibrator when vibrating; η is the conductivity coefficient, which depends on the vibrator-to-electrode spacing and bias voltage; g is the distance between the vibrator and the electrode; meff is the effective mass of the vibrator; csense is the capacitance between the vibrator and the second electrode 112; vdc is the bias voltage.

As is clear from the formula (1), the higher the applied bias voltage Vdc is, the lower the equivalent resistance Rm is for the given MEMS oscillator 1.

And the start-up time of the MEMS oscillator 1 is related to the equivalent resistance Rm. When the equivalent resistance Rm of the MEMS oscillator 1 is smaller, consumption of the driving voltage supplied to the MEMS resonator 11 by the oscillation maintaining module 13 is smaller. In this case, the smaller the equivalent resistance Rm of the MEMS oscillator 1, the lower the consumption of the MEMS resonator 11 after the driving voltage is applied, and the driving voltage can be increased to the voltage at which the MEMS resonator 11 normally operates (i.e., the MEMS resonator 11 stably operates) with a shorter period of time. The MEMS resonator 11 can be more easily vibrated by setting a larger bias voltage, and the required vibration starting time is significantly reduced.

Based on the above principle, for a given MEMS oscillator 1, a larger bias voltage needs to be set in order to reduce the required start-up time of the MEMS resonator 11; after the MEMS resonator 11 is started to work normally, a smaller bias voltage is required to be set for the MEMS oscillator 1 to have better performance, and the bias voltage value corresponding to the minimum phase noise can be optimally selected. Therefore, referring to fig. 6 and 7, the bias voltage in the present embodiment is at a first time t0 when the MEMS oscillator 1 starts to oscillate, and the bias voltage generating module 12 is configured to supply the first bias voltage Vb1 until a second time t1. From the second time t1, the bias voltage generating module 12 is configured to provide a second bias voltage Vb2. The first bias voltage Vb1 is greater than the second bias voltage Vb2, and the phase noise PN2 corresponding to the second bias voltage Vb2 is reduced relative to the phase noise PN1 corresponding to the first bias voltage Vb 1. In this case, it is ensured that the process of starting oscillation at the start of reception of the driving voltage by the MEMS resonator 11 is controlled by the first bias voltage Vb1 having a larger voltage value, thereby accelerating the process of starting oscillation; and after the MEMS resonator 11 reaches the preset oscillation frequency f1 (i.e., stable operation), it is controlled by the second bias voltage Vb2 having a smaller voltage value, thereby ensuring the stability of the MEMS resonator 11.

In some embodiments, the larger the first bias voltage Vb1 is, the better, however, in order to take into consideration the circuit power consumption and the maximum operating voltage of the MEMS resonator 11, the MEMS oscillator 1 is provided with a voltage threshold upper limit beyond which the first bias voltage Vb1 should not exceed.

In some embodiments, the second time t1 may be determined by an oscillation signal output from the MEMS resonator 11. Specifically, the MEMS resonator 11 has a resonance point that can vibrate stably, and the frequency corresponding to the resonance point is a preset oscillation frequency. From the first time t0 to the second time t1, the frequency of the oscillation signal output from the MEMS resonator 11 reaches a preset oscillation frequency. That is, the time interval between the first time t0 and the second time t1 is a preset time, and the preset time may satisfy: t is equal to or greater than T, wherein T is a preset time, and T is set to be a time required for the MEMS resonator 11 to reach a preset oscillation frequency under the action of the first bias voltage Vb 1. That is, when the time reaches the second time t1, the oscillation frequency of the MEMS resonator 11 may reach the set preset oscillation frequency. However, the embodiments of the present application are not limited thereto, and the preset time may also satisfy: 0<t < T, where 0 is denoted as the first time T0 when the MEMS resonator 11 starts to oscillate.

It will be appreciated that the present application may perform a test on the MEMS resonator 11 in advance to obtain the time required for the MEMS resonator 11 to reach the preset oscillation frequency under the action of the first bias voltage Vb1, so as to set the second time t1 according to the time. A timer device may be disposed in the switch control unit and the connection switch control unit, and the time reaches the second time t1, i.e. a switch control signal is sent to the controlled switch to adjust the output bias voltage. The example of the present application is not limited thereto, and the MEMS oscillator 1 may further include a frequency detection unit that may receive the oscillation signal to detect the frequency, and if the frequency of the oscillation signal reaches the preset oscillation frequency, send the detection signal to the switch control unit or the connection switch control unit in the different embodiments, so that the switch control unit or the connection switch control unit sends the switch control signal to adjust the switches respectively controlled, and adjust the output bias voltage. The application only needs to meet the requirement of adjusting the bias voltage when reaching the set requirement, and the application is not limited by the specific adjusting mode.

The present embodiment also provides a control method of the MEMS oscillator 1, which is implemented based on the MEMS oscillator 1 in the foregoing embodiment, and the control method may include:

applying a bias voltage and a driving voltage to the MEMS resonator 11 such that the MEMS resonator 11 vibrates under the bias voltage and the driving voltage to generate an oscillation signal; the bias voltage applied from the first time t0 when the MEMS resonator 11 starts vibrating is the first bias voltage Vb1 up to the second time t1, and the bias voltage applied from the second time t1 later is the second bias voltage Vb2.

Specifically, the first electrode 111 in the MEMS resonator 11 is applied with a driving voltage, the vibrator 113 is applied with a bias voltage, and the MEMS resonator 11 is driven to vibrate by the driving voltage and the bias voltage and generates an oscillation signal output. The phase noise of the MEMS resonator 11 can be changed by adjusting the bias voltage so that the MEMS resonator 11 maintains stable operation. In this embodiment, the second bias voltage Vb2 is set to be the bias voltage value corresponding to the minimum phase noise of the MEMS resonator 11, so as to ensure the optimal performance of the stable operation of the MEMS oscillator 1.

As shown in fig. 8, assuming that the second bias voltage Vb2 is always applied to the MEMS resonator 11, the operation process of the MEMS resonator 11 reaching the preset oscillation frequency f1 is shown as L2 in the figure, where the time for the MEMS resonator 11 to reach the preset oscillation frequency f1 is T2, and after the time T2, the MEMS resonator 11 can output the preset oscillation frequency f1 more stably. The working process of the MEMS resonator 11 reaching the preset oscillation frequency f1 is shown as L1 in the figure after the first bias voltage Vb1 is applied to the MEMS resonator 11 and then the first bias voltage is switched to the second bias voltage Vb2; because the MEMS resonator 11 has a high oscillation starting speed under the action of the first bias voltage Vb1, the MEMS resonator 11 of the present application can reach the preset oscillation frequency f1 at the time T1, and if the first bias voltage Vb1 is continuously applied, the frequency stability of the output of the MEMS resonator 1 is poor due to the large phase noise, therefore, the present application adopts the second bias voltage Vb2 to replace the first bias voltage Vb1 in the subsequent step, so as to reduce the phase noise and improve the output stability of the MEMS resonator 11.

Preferably, the time interval between the first time t0 and the second time t1 is a preset time, and the preset time can satisfy: t is equal to or greater than T, wherein T is a preset time, and T is set to be a time required for the MEMS resonator 11 to reach a preset oscillation frequency under the action of the first bias voltage Vb 1.

However, the example of the present application is not limited thereto, and the preset time may also satisfy: 0<t < T, where 0 is denoted as the first time T0 when the MEMS resonator 11 starts to oscillate. That is, referring to fig. 8, if the first bias voltage Vb1 is continuously applied to the MEMS resonator 11, the time for the MEMS resonator 11 to reach the preset oscillation frequency f1 is just the time T1. If the second time T1 is set to the time T' shown in fig. 8, that is, 0<t < T1 is satisfied, the MEMS resonator 11 is switched from the first bias voltage Vb1 to the second bias voltage Vb2 when the first bias voltage Vb1 is biased to have not reached the preset oscillation frequency f1. In this case, the oscillation starting process of the MEMS resonator 11 is divided into two parts, the former part using the first bias voltage Vb1 and the latter part using the second bias voltage Vb2; the first bias voltage Vb1 in the time period of 0-t 'is used for accelerating the vibration of the MEMS resonator 11, and after the second bias voltage Vb2 is used for biasing and reaches the preset oscillation frequency f1 at the moment t', the MEMS resonator 11 stably outputs at the preset oscillation frequency f 1; the required start-up time increases compared to the embodiment in which t.gtoreq.t, however, the start-up time required for the MEMS resonator 11 of the present embodiment may be relatively short compared to the start-up time T2 required for applying only the second bias voltage Vb2. The embodiment can also play a role in accelerating vibration to a certain extent.

In summary, according to the application, by applying bias voltages with different magnitudes to the vibrators in the MEMS resonator, the MEMS oscillator 1 is ensured to achieve rapid starting so as to reduce starting time, and the MEMS oscillator 1 also has better performance. Therefore, the application effectively overcomes various defects in the prior art and has high industrial utilization value.

The above embodiments are merely illustrative of the principles of the present application and its effectiveness, and are not intended to limit the application. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the application. Accordingly, it is intended that all equivalent modifications and variations of the application be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.

Claims (10)

1. A MEMS oscillator, comprising: a MEMS resonator for vibrating to provide an oscillation signal, a bias voltage generation module for providing a bias voltage to the MEMS resonator, and an oscillation maintenance module for maintaining the MEMS resonator vibrating and for generating a frequency signal;

the bias voltage generating module is configured to provide a first bias voltage from a first moment when the MEMS resonator starts vibrating up to a second moment, and configured to provide a second bias voltage from the second moment later;

the second moment is determined by an oscillation signal output by the MEMS resonator, the first bias voltage is greater than the second bias voltage, and phase noise of the MEMS resonator corresponding to the first bias voltage is greater than phase noise of the MEMS resonator corresponding to the second bias voltage.

2. The MEMS oscillator of claim 1, wherein: the second bias voltage is set to a bias voltage value corresponding to the minimum phase noise of the MEMS resonator.

3. The MEMS oscillator of claim 1, wherein: the MEMS resonator is provided with a resonance point capable of vibrating stably, and the frequency corresponding to the resonance point is a preset oscillation frequency; and from the first moment to the second moment, the frequency of the oscillation signal output by the MEMS resonator reaches the preset oscillation frequency.

4. The MEMS oscillator of claim 1, wherein: the bias voltage generating module comprises a first voltage generating unit, a second voltage generating unit, a first branch switch, a second branch switch and a switch control unit;

the switch control unit is respectively connected with the control ends of the first branch switch and the second branch switch and is used for generating a switch control signal to respectively control the opening or closing of the first branch switch and the second branch switch;

the output end of the first voltage generating unit is electrically connected with the MEMS resonator through the first branch switch;

the output end of the second voltage generating unit is electrically connected with the MEMS resonator through the second branch switch.

5. The MEMS oscillator of claim 1, wherein: the bias voltage generating module comprises a first voltage generating unit, a second voltage generating unit, a selection switch and a switch control unit;

the switch control unit is connected with the control end of the selection switch and is used for generating a selection switch control signal to adjust a switch node communicated with the selection switch;

the output end of the first voltage generating unit is connected with a switch node and is electrically connected with the MEMS resonator through the selection switch;

the output end of the second voltage generating unit is connected with another switch node and is electrically connected with the MEMS resonator through the selection switch.

6. The MEMS oscillator of claim 4 or 5, wherein: the first voltage generating unit comprises a first charge pump, the second voltage generating unit comprises a second charge pump, one of the first charge pump and the second charge pump is controlled and selected by the switch control unit to be connected with the MEMS resonator electrically so as to provide bias voltage, and the bias voltage provided by the first charge pump is the first bias voltage; the bias voltage provided by the second charge pump is the second bias voltage.

7. The MEMS oscillator of claim 1, wherein: the bias voltage generation module comprises a third charge pump, a first capacitor, a second capacitor, a connecting switch and a connecting switch control unit;

the connecting switch control unit is connected with the control end of the connecting switch and is used for generating a connecting switch control signal and controlling the connecting switch to be opened or closed;

the upper polar plate of the first capacitor is connected with the output end of the third charge pump, and the lower polar plate is grounded;

the upper polar plate of the second capacitor is connected with the upper polar plate of the first capacitor through the connecting switch, and the lower polar plate is grounded;

the output end of the third charge pump is used as the output end of the bias voltage generating module.

8. The MEMS oscillator of claim 1, wherein: the MEMS resonator is provided with a resonance point capable of vibrating stably, the frequency corresponding to the resonance point is preset oscillation frequency, the time interval between the first moment and the second moment is preset time, and the preset time satisfies the following conditions:

0<t＜T，

wherein T is denoted as the preset time, 0 is denoted as a first moment when the MEMS resonator starts to vibrate, and T is set as a time required for the MEMS resonator to reach a preset oscillation frequency under the action of the first bias voltage.

9. A control method of a MEMS oscillator including a MEMS resonator for vibrating to provide an oscillation signal, a bias voltage generation module for providing a bias voltage to the MEMS resonator, and an oscillation maintenance module for providing a drive signal to maintain the MEMS resonator vibrating, characterized by comprising:

applying the bias voltage and the drive voltage to the MEMS resonator such that the MEMS resonator oscillates under the bias voltage and the drive voltage to generate the oscillation signal; the applied bias voltage is a first bias voltage from a first moment when the MEMS resonator starts vibrating until a second moment, and the applied bias voltage is a second bias voltage from the second moment;

the second moment is determined by an oscillation signal output by the MEMS resonator, the first bias voltage is greater than the second bias voltage, and phase noise of the MEMS resonator corresponding to the first bias voltage is greater than phase noise of the MEMS resonator corresponding to the second bias voltage.

10. The method of controlling a MEMS oscillator according to claim 9, wherein: the MEMS resonator is provided with a resonance point capable of vibrating stably, the frequency corresponding to the resonance point is preset oscillation frequency, the time interval between the first moment and the second moment is preset time, and the preset time satisfies the following conditions:

t≥T，

wherein T is denoted as the preset time, and T is set as the time required for the MEMS resonator to reach a preset oscillation frequency under the action of the first bias voltage.