Embodiment
Fig. 1 is the block diagram of a part of an example that comprises the electronic system of MEMS transducer 105 and IC110.The MEMS transducer can comprise the MEMS gyroscope, for example, and vibratory gyroscope.Vibratory gyroscope can comprise the test block (proof mass) that is suspended in the substrate top.Test block is in driving direction and mechanically vibration on the induction direction perpendicular to driving direction.Test block is ordered about by external drive source and be in resonance state on driving direction.When gyroscope is rotated by angle, produce Coriolis force (Coriolis force) on induction mode, Coriolis force detects with sense capacitor.In the figure, capacitor gdp and gdn represent the driving input to MEMS transducer 105, and capacitor gp and gn represent the sensing signal output of MEMS transducer 105.
IC110 comprises configuration or is designed to the mechanical oscillation of MEMS transducer 105 is remained to the circuit of target mechanical oscillation.These circuit comprise electric charge-voltage translator circuit 115(C2V) and transducer driving amplifier circuit 120.The charge conversion that C2V will be produced by the mechanical oscillation of MEMS transducer becomes voltage.Transducer driving amplifier circuit 120 provides electrostatic force to transducer, to cause mechanical oscillation.IC110 also comprises automatic gain control (AGC) circuit 125 and drive signal circuit 130.Agc circuit 125 is regulated electrostatic force, so that mechanical oscillation is remained to desired value.
Drive signal circuit 130 provides the referenced drive signal to transducer driving amplifier circuit 120.This referenced drive signal can be based on the signal that induced by MEMS transducer 105.Because the sensing that is undertaken by the MEMS transducer and the driving of MEMS transducer are 90 degree out-phase, so the signal of institute's sensing skew 90 degree roughly, to produce the referenced drive signal.Yet therefore, when electronic system starts first or powers on, do not have the driving signal that can be used for MEMS transducer 105, and do not exist sensing signal from MEMS transducer 105 to create the referenced drive signal.
Drive signal in order to create initial reference, drive signal circuit 130 produces an oscillator signal when powering on.Therefore, even when ought be non-existent from the sensing signal of MEMS transducer 105, drive signal and also can be provided to transducer driving amplifier circuit 120.This oscillator signal causes mechanical oscillation in MEMS transducer 105, mechanical oscillation then produces electric charge and at the output of C2V circuit, produces sensing signal.The initial signal that drives can comprise a plurality of harmonic frequencies.When the sensing signal that produces reached threshold amplitude, the referenced drive signal was locked into the frequency of the sensing signal that produces.Due to the mechanical resonance of MEMS transducer 105, the sensing signal that is produced by the MEMS transducer is high Q signal, and with this signal, produces high Q referenced drive signal.
Fig. 2 is the flow chart of a kind of generation for the method 200 of the driving signal of MEMS transducer (for example, MEMS free gyroscope or gyroscope).At square frame 205 places, oscillator signal is certainly to be produced by the output of drive signal circuit in drive signal circuit.Oscillator signal is applied to the driving input of MEMS transducer.
At square frame 210 places, in response to the driving input that oscillator signal is applied to the MEMS transducer, expression is received at the input end of drive signal circuit by the voltage signal of the electric charge that the MEMS transducer produces.
At square frame 215 places, the phase place of received voltage signal is offset 90 degree substantially, and through the signal of phase shift, is used to produce the driving signal, rather than uses from the signal that produces.At square frame 220 places, the driving signal that produces is applied to the driving input of MEMS transducer.
Fig. 3 is the circuit diagram of a part of an example of drive signal circuit.Drive signal circuit provides the referenced drive signal for the MEMS transducer.Drive signal circuit comprises input 335, and input 335 receives the voltage signal that represents the electric charge that is produced by the MEMS transducer.In some instances, voltage signal receives from electric charge-voltage translator circuit.
Voltage signal circuit also comprises phase-shift circuit 340 and comparator circuit 345.Phase-shift circuit 340 can be electrically coupled to input 335.Phase-shift circuit 340 with the phase deviation of input signal substantially 90 the degree (90 °).In some instances, phase-shift circuit 340 comprises integrator circuit.Comparator circuit 345 has hysteresis.When input during greater than first threshold, the output of comparator circuit 345 is from the low height that is transformed into, and when input during less than the Second Threshold different from first threshold, export be transformed into from height low.The input of comparator circuit 345 can be electrically coupled to the output of phase-shift circuit 340, and the output of comparator circuit 345 can be electrically coupled to the output 350 of drive signal circuit.
Drive signal circuit comprises feedback loop, and the output that this feedback loop prolongs from drive signal circuit reaches the input of phase-shift circuit 340.If phase-shift circuit 340 comprises integrator circuit, feedback loop can be electrically coupled to from the output of comparator circuit 345 input of the amplifier circuit 355 of integrator circuit.As shown in the example of Fig. 3, feedback loop can comprise: the first transconductance amplifier circuit 360(is sometimes referred to as operation transconductance amplifier or OTA), it has the input of the output that is electrically coupled to comparator circuit 350; And second transconductance amplifier circuit 365, the output that it has the input of the output that is electrically coupled to the first transconductance amplifier circuit 360 and is electrically coupled to the input of phase-shift circuit 340.Feedback loop can comprise capacitor 370(C1), capacitor 370 is coupled to output and the circuit ground of the first transconductance amplifier circuit 360.
The output that is configured in drive signal circuit 350 places of feedback loop are from producing vibration signal or self-oscillation signal.Hysteresis comparator circuit keeps minimum with the amplitude of the vibration of (output of integrator) in loop, and controls the scope of self-oscillating frequency.The binary system output of comparator is carried out charge/discharge by 360 pairs of capacitors of the first transconductance amplifier circuit 370.Error in the self-oscillation signal that is caused by 50% duty ratio is stored on capacitor 370, and by the second transconductance amplifier circuit 365, feeds back to phase-shift circuit 340.This feedback arrangement is proofreaied and correct input signal skew, amplifier offset and comparator offset, so that the output signal of 50% duty ratio substantially to be provided.
The output signal that is produced by drive signal circuit is applied to the driving input of MEMS transducer.Can be drive circuit output 350(output as the output signal that provides with reference to driving signal) signal located of the signal of locating or the output (output-sine wave) of phase-shift circuit 340.For the example shown in Fig. 1, the self-oscillation signal of drive signal circuit is the referenced drive signal of being selected when powering on by agc circuit 125 as being used for driving amplifier circuit 120.Should be that to be marked with the circuit node place of output in drive signal circuit available from the oscillator signal that produces.When the amplitude of the signal of institute's sensing be enough (for example, meet the prearranged signal threshold amplitude) time, agc circuit 125 can be switched to the available signal of output-sine wave with the referenced drive signal by from the available signal of output, coming and be used as the referenced drive signal.This is that output-sine wave provides the referenced drive signal of harmonic wave purer (for example, higher Q) for the MEMS transducer because after reaching amplitude threshold.Due to less harmonic frequency, high Q signal is improved driving and the mechanical resonance in the MEMS transducer.The high Q signal at output-sine wave place provides 90 degree phase shifts and 50% duty ratio accurately substantially.
If phase-shift circuit 340 comprises integrator circuit, feedback arrangement provides stable operating point for the forward path integrator.Stable operating point has been avoided problem out of control (run-away problem), and problem out of control can be carried out integration and be caused by the biasing to less.In addition, use makes the self-oscillation signal minimize with the frequency displacement of temperature for the amplifier circuit 355 that direct current (DC) signal has controlled signal gain.Feedback network should be designed to the DC electric current that provides enough large, so that skew compensates to input signal, but should have low-down interchange (AC) gain, so that the 90 degree phase shifts that provided by the forward path integrator not to be provided.
It is the mutual conductance gm value that is difficult to realize that the design of feedback loop can require for the second transconductance amplifier circuit.Less gm value can be by output current is shunted to avoid before the output current with the second trsanscondutance amplifier feeds back to phase-shift circuit.Fig. 4 is the circuit diagram of a part of another example of drive signal circuit, and this drive signal circuit has the feedback loop that comprises the first transconductance amplifier circuit 460 and the second transconductance amplifier circuit 465.Drive signal circuit comprises splitter circuit 475, and splitter circuit 475 is electrically coupled to the output of the second transconductance amplifier circuit 465, with the output current to the second transconductance amplifier circuit 465, shunts.
Fig. 5 is the circuit diagram of a part of the another example of drive signal circuit, and this drive signal circuit has the feedback loop that comprises the first transconductance amplifier circuit 560 and the second transconductance amplifier circuit 565.Drive signal circuit comprises resitstance voltage divider 575, and resitstance voltage divider 575 is electrically coupled to the output of the second transconductance amplifier circuit 565 and the input of phase-shift circuit 540, with the output current to the second transconductance amplifier circuit 565, shunts.
The amplifier of feedforward integrator circuit should have low gain, in larger input signal operating period, to provide good phase margin.A kind of alternative method is to use high-gain amplifier, but changes the configuration of feedback loop.Fig. 6 is the circuit diagram of a part of another example of drive signal circuit, and this drive signal circuit has the feedback loop that comprises the first transconductance amplifier circuit 660 and the second transconductance amplifier circuit 665.The second transconductance amplifier circuit 665 has the input of the output that is electrically coupled to the first transconductance amplifier circuit, and has the output of the input that is electrically coupled to the integrator amplifier circuit.Feedback loop also comprises the resistor 680 of the output that is coupled to the first transconductance amplifier circuit 660 and the capacitor 670 that is coupled to resistor 680 and circuit ground.This compensating resistor R
1Increased a zero point to feedback transfer function.It is leading that this has increased phase place, with the phase margin to the high-amplitude input signal, improves.
For be provided effective zero point in feedback, the value of compensating resistor may be too large for the realization on IC.Fig. 7 is the also circuit diagram of the part of an example of drive signal circuit, and this drive signal circuit has the feedback loop that comprises the 3rd transconductance amplifier circuit 785.The input of the 3rd transconductance amplifier circuit 785 is electrically coupled to the input of the output sum-product intergrator amplifier circuit of comparator circuit 745, to form the feedback loop of the second parallel connection.The transconductance stage of this increase has been eliminated the needs to the large compensation resistor, and can be provided effective zero point, to provide phase place in advance and the phase margin of high-amplitude input signal is improved.
Fig. 8 is a kind of flow chart of an example of method 800 of drive signal circuit of the MEMS of being formed for transducer.At square frame 805 places, the input of drive signal circuit is electrically coupled to the input of integrator circuit.Integrator circuit can have circuit topological structure as shown in example herein.At square frame 810 places, the output of integrator circuit is electrically coupled to the comparator circuit with hysteresis.
At square frame 815 places, when circuit power was applied to drive signal circuit, the output that the feedback loop in drive signal circuit is formed in drive signal circuit produced the self-oscillation signal.Feedback loop extends to the input of the amplifier (for example, operational amplifier or opamp) of integrator circuit from the output of comparator circuit.Integrator circuit will be offset at the phase angle of the received input signal of input end 90 degree substantially.Received input signal is in response to the driving input that the self-oscillation signal is applied to the MEMS transducer and produces.Drive signal circuit can be electrically coupled to the capacitance-voltage converter circuit, and input signal can be in response to the voltage signal that the self-oscillation signal is applied to the MEMS transducer and from the electric charge by the generation of MEMS transducer, changes.
Drive signal circuit provides reliable self-starting that the driving oscillator signal is provided, and 50% duty ratio is provided reliably.Drive signal circuit further provides 90 ° of phase shifts accurately, and the noise that is associated with the differentiator phase shifter has been avoided in 90 ° of phase shifts accurately.
Extra explanation and example
Example 1 can comprise theme (for example, a kind of device), and this theme comprises the drive signal circuit for MEMS (micro electro mechanical system) (MEMS) transducer.This drive signal circuit comprises: input, and it is configured to the receiver voltage signal, and described voltage signal represents the electric charge that is produced by described MEMS transducer; Phase-shift circuit, it is electrically coupled to described input, and be configured to phase shifted input signal substantially 90 the degree; Comparator circuit with hysteresis; And feedback loop, its output from described drive signal circuit extends to the input of described phase-shift circuit.The input of described comparator can be electrically coupled to the output of described phase-shift circuit, and the output of described comparator circuit is electrically coupled to the output of described drive signal circuit.Described feedback loop can be configured to produce the self-oscillation signal at the output of described drive signal circuit, and is applied to the driving input of described MEMS transducer by the output signal that described drive signal circuit produces.
Example 2 can comprise or can optionally with the theme of example 1, combine optionally to comprise: the first transconductance amplifier circuit, and it has the input of the output that is electrically coupled to described comparator circuit; The second transconductance amplifier circuit, it has the input of the output that is electrically coupled to described the first transconductance amplifier circuit, and is electrically coupled to the output of the input of described phase-shift circuit; And capacitor, it is coupled to output and the circuit ground of described the first transconductance amplifier circuit.
Example 3 can comprise or can be optionally with example 1 and example 2 in one or the theme of combination in any combine optionally to comprise: splitter circuit, it is electrically coupled to the output of described the second transconductance amplifier circuit.
Example 4 can comprise or can be optionally with example 1-3 in one or the theme of combination in any combine optionally to comprise: resistive divider circuit, it is electrically coupled to the output of described the second transconductance amplifier circuit and the input of described phase-shift circuit, wherein, described resitstance voltage divider is configured to the output current of described the second transconductance amplifier circuit is shunted.
Example 5 can comprise or can be optionally with example 1-4 in one or the theme of combination in any combine optionally to comprise: phase-shift circuit, it comprises integrator circuit, described integrator circuit comprises amplifier circuit; And feedback loop, its output from described comparator circuit optionally is electrically coupled to the input of described integrator amplifier circuit.
Example 6 can comprise or can be optionally with example 5 in theme combine optionally to comprise: the integrator amplifier circuit, it is that direct current (DC) signal provides controlled signal gain.
Example 7 can comprise or can be optionally with example 5 and example 6 in one or the theme of combination in any combine optionally to comprise the 3rd transconductance amplifier circuit, and, the input of described the 3rd transconductance amplifier circuit is electrically coupled to the output of described comparator circuit and the input of described integrator amplifier circuit, to form the second feedback loop.
Example 8 can comprise or can be optionally with example 5-7 in one or the theme of combination in any combine optionally to comprise: feedback loop, it comprises: the first transconductance amplifier circuit, and it has the input of the output that is electrically coupled to described comparator circuit; The second transconductance amplifier circuit, it has the input of the output that is electrically coupled to described the first transconductance amplifier circuit, and has the output of the input that is electrically coupled to described integrator amplifier circuit; Resistor, it is coupled to the output of described the first transconductance amplifier circuit; And capacitor, it is coupled to described resistor and circuit ground.
Example 9 can comprise or can be optionally with example 1-8 in one or the theme of combination in any combine optionally to comprise the MEMS transducer, wherein, described MEMS transducer comprises the MEMS gyroscope.
Example 10 can comprise or can be optionally with example 1-9 in one or the theme of combination in any combine optionally to comprise that theme (for example, a kind of method, a kind of device be used to performing an action, the machine readable media that perhaps comprises instruction, when by machine, being carried out, instruction can cause machine to perform an action), this theme comprises: the output in drive signal circuit produces oscillator signal certainly, and described oscillator signal is applied to the driving input of described MEMS transducer; In response to described oscillator signal being applied to the driving input of described MEMS transducer, at the input end receiver voltage signal of described drive signal circuit, described voltage signal represents the electric charge that is produced by described MEMS transducer; , with the phase deviation of received voltage signal 90 degree substantially, and with described signal through phase shift, produce described driving signal; And the driving input that the driving signal that produces is applied to described MEMS transducer.
Example 11 can comprise or can be optionally with example 10 in theme combine optionally to comprise: with integrator circuit, received voltage signal is carried out integration.
Example 12 can comprise or can be optionally with example 11 in theme combine optionally to comprise: will be applied to the comparator circuit with hysteresis through the received voltage signal of integration, and the output of described comparator circuit is fed back to the input of the amplifier of described integrator circuit, to form feedback loop.
Example 13 can comprise or can be optionally with example 12 in theme combine optionally to comprise: use the output of described comparator circuit, by the first transconductance amplifier circuit, capacitor charged; And the electric charge of described capacitor is applied to the input of the described amplifier of described integrator circuit by the second transconductance amplifier circuit.
Example 14 can comprise or can be optionally with example 13 in one or the theme of combination in any combine optionally to comprise: the output current to described the second transconductance amplifier circuit is shunted, to reduce the mutual conductance of described the second transconductance amplifier circuit.
Example 15 can comprise or can be optionally with example 13 and example 14 in one or the theme of combination in any combine optionally to comprise: the input that the output of described comparator circuit is electrically coupled to the 3rd transconductance amplifier circuit, and the output of described the 3rd transconductance amplifier circuit is electrically coupled to the input of the described amplifier circuit of described integrator circuit, to form the second feedback loop.
Example 16 can comprise or can be optionally with example 13-15 in one or the theme of combination in any combine optionally to comprise: by described the 3rd trsanscondutance amplifier and resistor, described capacitor is charged.
Example 17 can comprise or can be optionally with example 11-16 in one or the theme of combination in any combine optionally to comprise: the driving input that the driving signal that produces is applied to the MEMS gyro sensor.
Example 18 can comprise or can be optionally with example 1-17 in one or the theme of combination in any combine optionally to comprise that theme (for example, a kind of method, a kind of device be used to performing an action, the machine readable media that perhaps comprises instruction, when by machine, being carried out, instruction can cause machine to perform an action), this theme comprises: the input of described drive signal circuit is electrically coupled to integrator circuit; The output of described integrator circuit is electrically coupled to the comparator circuit with hysteresis; And form feedback loop in described drive circuit, with when circuit power is applied to described drive signal circuit, output in described drive signal circuit produces the self-oscillation signal, wherein, described feedback loop extends to the input of the amplifier of described integrator circuit from the output of described comparator circuit.Described integrator circuit will be at the phase angle of the received input signal of the input end of described drive signal circuit skew 90 degree substantially, and described input signal is in response to the driving input that described self-oscillation signal is applied to described MEMS transducer and produces.
Example 19 can comprise or can be optionally with example 18 in theme combine optionally to comprise: the output of described comparator circuit is electrically coupled to capacitor by the first transconductance amplifier circuit, and with the second trsanscondutance amplifier, described capacitor electrode is coupled to described phase-shift circuit.
Example 20 can comprise or can be optionally with example 19 in theme combine optionally to comprise: the output that splitter circuit is electrically coupled to described the second trsanscondutance amplifier.
Example 21 can comprise or can be optionally with example 18-20 in one or the theme of combination in any combine optionally to comprise: at described input end, resistive divider circuit is electrically coupled to described integrator circuit.
Example 22 can comprise or can be optionally with example 18-21 in one or the theme of combination in any combine optionally to comprise: amplifier circuit, it has controlled signal gain for the DC signal.
Example 23 can comprise or can be optionally with example 18-22 in one or the theme of combination in any combine optionally to comprise: the input that the output of described comparator circuit is electrically coupled to the 3rd transconductance amplifier circuit, and the output of described the 3rd transconductance amplifier circuit is electrically coupled to the input of the described amplifier circuit of described integrator circuit, to form the second feedback loop.
Example 24 can comprise or can be optionally with example 18-23 in one or the theme of combination in any combine optionally to comprise: produce input signal in response to described self-oscillation signal is applied to the gyrostatic driving input of MEMS.
Example 25 can comprise or can be optionally with example 1-24 in one or the theme of combination in any combine optionally to comprise theme, this theme can comprise: the device of one or more functions that is used for carrying out the function of example 1-24; The machine readable media that perhaps comprises instruction, when by machine, being carried out, instruction causes machine to carry out one or more functions in the function of example 1-24.
Above-mentioned detail specifications is with reference to accompanying drawing, and accompanying drawing is also the part of described detail specifications.Accompanying drawing has shown and can apply specific embodiment of the utility model in graphic mode.These embodiment are known as " example " in the utility model.Related all publications, patent and the patent document of the utility model be all as reference content of the present utility model, although they are in addition references respectively., if there is purposes difference between the utility model and reference paper, with reference to the purposes of file, regard supplementing purposes of the present utility model as; , if there is implacable difference between the two, with purposes of the present utility model, be as the criterion.
In this article, normally used the same with patent document, term " " or " a certain " expression comprises one or more, but other situations or when using " at least one " or " one or more " should except.In this article, except as otherwise noted, otherwise use the term "or" refer to without exclusiveness or, make " A or B " comprising: " A but be not B ", " B but be not A " and " A and B ".In claims, term " comprises " and " therein " is equal to that each term " comprises " and the popular English of " wherein ".Equally, in this article, term " comprises " and " comprising " is open, namely, system, equipment, article or step comprise parts those parts listed after in claim this term, within still being considered as dropping on the scope of this claim.And in claim below, term " first ", " second " and " the 3rd " etc. only, as label, not have quantitative requirement to object.
The effect of above-mentioned specification is to explain orally and unrestricted.In other examples, above-mentioned example (or one or more aspects of example) can be combined with.Can on the basis of understanding above-mentioned specification, utilize certain routine techniques of prior art to carry out other embodiment.In accordance with 37C.F.R. § 1.72(b) regulation summary is provided, allow the reader to determine fast the disclosed character of present technique.Should be understood that while submitting this summary to that this summary is not used in scope or the meaning of explaining or limiting claim.Equally, in superincumbent embodiment, various features can be classified into rationalizes the disclosure.This open feature that does not should be understood to failed call is essential to any claim.On the contrary, the theme of the present utility model feature that can be is less than all features of specific disclosed embodiment.Therefore, following claim is incorporated in embodiment accordingly, and each claim is all as an independent embodiment.Should be referring to appended claim, and all scopes of the equivalent enjoyed of these claims, determine the application's scope.