JP5344955B2 - Solid oscillator oscillation circuit and physical quantity sensor using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid vibrator oscillation circuit which shortens the time needed to regularly excite a vibrator, that is the activation time, and solves problems such as the saturation of the output voltage waveform of an amplifier, the amplification of noise and the stability of the oscillation state of the vibrator after amplification degree change. <P>SOLUTION: The solid vibrator oscillation circuit 10 includes the vibrator 12, a current/voltage conversion circuit 14 for converting an output current from the vibrator to a voltage, and amplifiers 16 and 18 for amplifying an output voltage from the current/voltage conversion circuit 14. The amplifiers 16 and 18 are provided with variable current switches 20 and 22 for changing the amplification degrees of the amplifiers, and the variable current switches 20 and 22 are configured such that the size of a flowing current is continuously changed on the basis of the output voltage from the current/voltage conversion circuit 14 and the amplification degrees of the amplifiers 16 and 18 are continuously changed. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a solid oscillator oscillation circuit for oscillating a vibrator such as a crystal vibrator or a ceramic oscillator. More specifically, the present invention relates to a solid vibrator oscillation capable of accelerating steady-state excitation of a vibrator. The present invention relates to a circuit and a physical quantity sensor using the circuit.

  Conventionally, vibration gyro sensors that detect angular velocities as physical quantities using vibrators have been used for car navigation systems, robot posture control, camera shake correction, etc. as extremely small and inexpensive gyro sensors. In recent years, as the demand for these products has expanded, the demand for vibration gyro sensors has also increased rapidly.

  Such a vibration gyro sensor includes an oscillation circuit that applies a voltage to the vibrator to vibrate the vibrator and a detection circuit that detects a Coriolis force applied to the vibrator. In particular, the configuration of the oscillation circuit is an important circuit for shortening the time required for starting the physical quantity sensor because it affects the time required for the vibrator to perform steady excitation.

  In general, an oscillation circuit oscillates a vibrator by converting an output current from the vibrator into a voltage by a current-voltage conversion circuit and feeding back this voltage to the vibrator through an amplifier. For this reason, in order to shorten the time until the vibrator is normally excited, the amplification degree of the amplifier may be increased.

However, when the amplification degree of the amplifier is increased, problems occur in saturation of the output voltage waveform of the amplifier, amplification of noise, stability of the oscillation state of the vibrator, and the like.
For this reason, as shown in FIG. 11, the oscillator 101, the current-voltage conversion circuit (first amplifier) 102 that converts the output current from the oscillator 101 into a voltage, and the output signal of the current-voltage conversion circuit 102 are rectified. A rectifier circuit 103 that obtains a DC voltage, and a variable gain amplifier 105 that receives the output signal of the current-voltage converter circuit 102 and changes the amplification degree according to the value of the output voltage of the rectifier circuit. And a switching means 121 for switching the amplification degree of the variable gain amplifier 105 or the voltage amplifier 106 provided at the subsequent stage of the variable gain amplifier 105. The switching means 121 is switched by the output of the level determination circuit 126. An oscillation circuit 100 that controls the amplitude of the vibrator 101 is disclosed (Patent Document 1).

  In this oscillation circuit 100, when the power is turned on, the switch means 121 is in the on state, and the time required for the vibrator 101 to be in the steady excitation is shortened by increasing the amplification degree of the voltage amplifier 106. . When the vibrator 101 is in steady excitation, the switch circuit 121 is turned off by the level determination circuit 126, and the output voltage waveform of the variable gain amplifier 105 is reduced by reducing the amplification degree of the voltage amplifier 106. Problems such as saturation, reduction and maintenance of noise, and stabilization of the oscillation state of the vibrator 101 have been solved.

  In the oscillation circuit shown in FIG. 12, the vibrator 101, the current-voltage conversion circuit (first amplifier) 102 that converts the output current from the vibrator 101 into a voltage, and the output signal of the current-voltage conversion circuit 102 are rectified. A rectifier circuit 103 for obtaining a DC voltage; a variable gain amplifier 105 that receives an output signal of the current-voltage converter circuit 102 and whose amplification degree changes according to the value of the output voltage of the rectifier circuit 103; and an output signal of the variable gain amplifier 105 Between the second amplifier 106, the level determination circuit 126 to which the output voltage of the rectifier circuit 103 and the output voltage of the reference voltage generator 125 are input, and the current-voltage conversion circuit 102 and the second amplifier 106. The third amplifier 120 and the switch means 121 are provided, and the output signal of the current-voltage conversion circuit 102 is input to the positive input terminal of the third amplifier 120, and the third amplifier 120. A voltage having a magnitude close to ½ of the power supply voltage is applied to the negative input terminal via a capacitor, and a second resistor is connected between the output terminal of the third amplifier 120 and the input terminal of the second amplifier 106. An oscillation circuit 100 is disclosed in which a switch unit 121 is connected in series, the switch unit 121 is controlled by the output of the level determination circuit 126, and the amplitude of the vibrator 101 is controlled by changing the amplification degree of the second amplifier 106. (Patent Document 2).

  The oscillation circuit 100 basically has the same configuration as the oscillation circuit 100 shown in FIG. 11, but further includes a third amplifier 120 to increase the amplification factor of the second amplifier 106. The time required for the vibrator 101 to become steady excitation is shortened.

Japanese Patent No. 3932661 Japanese Patent No. 4075152

  However, when the amplification degree of the voltage amplifier 106 is changed using such a switch means 121, the amplification degree of the voltage amplifier 106 is changed to that shown in FIG. 13 when the switch means 121 changes from the on state to the off state. As shown, it will change drastically.

  For this reason, when the switch unit 121 changes from the on state to the off state, ringing or the like occurs, the oscillation state of the vibrator 101 becomes unstable, and the time until the vibrator 101 is normally excited is long. It became a factor to become.

  Further, in the case of such an oscillation circuit 100, a level determination circuit 126 and a reference voltage generation unit 125 for the level determination circuit 126 to perform level determination are necessary for turning on and off the switch means 121. As a result, this has hindered circuit miniaturization and power saving.

  In view of such a current situation, the present invention reduces the time required for steady-state excitation of the vibrator, that is, the start-up time, saturation of the output voltage waveform of the amplifier, amplification of noise, and vibration after change of the amplification degree. An object of the present invention is to provide a solid state oscillator circuit that solves the problem of the stability of the oscillation state of the child.

  In addition, the present invention provides a solid oscillator oscillation circuit capable of reducing the size and power consumption of the oscillation circuit by changing the amplification degree of the oscillation circuit without using a level determination circuit or a reference voltage generator. The purpose is to provide.

  Furthermore, an object of the present invention is to provide a physical quantity sensor that has such a solid state oscillator circuit and can be reduced in startup time and reduced in size and power consumption.

The present invention has been invented in order to achieve the problems and objects in the prior art as described above.
A vibrator,
A current-voltage conversion circuit that converts an output current from the vibrator into a voltage;
A solid-state oscillator oscillation circuit including an amplifier for amplifying an output voltage from the current-voltage conversion circuit,
The amplifier is composed of a plurality of stages of amplifiers,
Each of the multi-stage amplifiers includes a variable current switch that changes an amplification degree,
The variable current switch is configured to continuously change the magnitude of the flowing current based on the output voltage from the current-voltage conversion circuit, and to continuously change the amplification degree of the amplifier ,
Each of the variable current switches has a cut-off voltage,
When the input voltage to the variable current switch is equal to or lower than a predetermined cut-off voltage, the magnitude of the flowing current becomes 0, and the amplification degree of the amplifier is set to the minimum value.
After the vibrator starts oscillating, the variable current switch provided in another amplifier is cut off earlier than the variable current switch provided in the first-stage amplifier among the plurality of stages of amplifiers .

  With this configuration, the magnitude of the current flowing through the variable current switch is continuously controlled by the magnitude of the output voltage from the current-voltage conversion circuit corresponding to the output current of the vibrator. For this reason, the amplification level of the amplifier also changes continuously, so that when the switch is turned on and off, the amplification level does not change drastically and ringing does not occur. Can be excited.

  In addition, since it is not necessary to provide a level determination circuit, a reference voltage generation unit, or the like in order to change the amplification degree of the amplifier, it is possible to achieve downsizing and power saving as a solid vibrator oscillation circuit. Therefore, if a physical quantity sensor such as a vibration type gyro sensor is configured using such a solid vibrator oscillation circuit, for example, the physical quantity sensor itself can be reduced in size and use time can be improved due to power saving. .

Further, by configuring the amplifier with a plurality of stages of amplifiers, the degree of amplification as a solid oscillator oscillation circuit can be increased, and the time required for steady-state excitation of the oscillator can be shortened.

  Note that the number of stages of amplifiers can be selected as appropriate according to the time until the vibrator is normally excited. Accordingly, by appropriately selecting the number of stages of amplifiers according to the startup time required for the physical quantity sensor in which the solid oscillator oscillation circuit is used, it is possible to balance the startup time of the physical quantity sensor and the power saving of the physical quantity sensor. it can.

Further, with this configuration, the amplification degree of the amplifier can be continuously reduced by gradually reducing the input voltage to the variable current switch. Also, when the input voltage to the variable current switch falls below the cut-off voltage, no current flows through the variable current switch, so even if the input voltage to the variable current switch fluctuates below the cut-off voltage, the amplifier The amplification degree can be stabilized at all times.
Further, with this configuration, the variable current switch provided in the amplifiers other than the first-stage amplifier among the multiple-stage amplifiers is cut off first, that is, the amplification degree of the amplifier becomes the minimum value. For this reason, even when the amplification level is changed in the first stage amplifier, the amplification level of the amplifier in the subsequent stage is fixed. The output voltage will be stabilized.
Therefore, since a stable voltage is always input as the voltage fed back to the vibrating body, it is possible to shorten the time required until the vibrator is normally excited. In addition, the oscillation state of the vibrator can always be stabilized.

In the solid state oscillator circuit according to the present invention, the variable current switch may be constituted by a MOSFET.
In this way, if the variable current switch is a MOSFET, the amount of current flowing between the drain and source can be controlled by applying the input voltage for controlling the passing current to the gate terminal of the MOSFET. A switch can be configured.

  Therefore, even when the solid vibrator oscillation circuit is integrated, it is possible to easily reduce the size and save power.

In the solid state oscillator circuit of the present invention, the variable current switch may be configured by connecting a resistance element in parallel to the current passing path.
Thus, by connecting a resistance element in parallel to the current passage path of the variable current switch, the amplification factor of the amplifier is fixed to 1 or more by the resistance element connected in parallel even when the variable current switch is cut off. It becomes possible.

  Further, in the solid state oscillator circuit according to the present invention, the cut-off voltage of the variable current switch provided in the first-stage amplifier among the plural-stage amplifiers is smaller than the cut-off voltage of the variable current switch provided in the other amplifier. It may be.

  With this configuration, the variable current switch provided in the amplifiers other than the first-stage amplifier among the multiple-stage amplifiers is cut off first, that is, the amplification degree of the amplifier becomes the minimum value. For this reason, even when the amplification level is changed in the first stage amplifier, the amplification level of the amplifier in the subsequent stage is fixed. This also stabilizes the output voltage.

  Therefore, since a stable voltage is always input as the voltage fed back to the vibrating body, it is possible to shorten the time required until the vibrator is normally excited. In addition, the oscillation state of the vibrator can always be stabilized.

In the solid state oscillator circuit of the present invention, an offset adjustment circuit may be provided on the output side of at least one of the plurality of stages of amplifiers.
In the solid state oscillator circuit of the present invention, the offset adjustment circuit may be a high pass filter.

  In this way, by providing an offset adjustment circuit such as a high-pass filter on the output side of at least one of the amplifiers in a plurality of stages, even if an offset occurs in the output of the amplifier, this offset is reduced. Can be canceled.

  Therefore, the amplitude of the output voltage of the amplifier can be increased, so that the amplification degree can be kept large as a solid vibrator oscillation circuit, and the time required for steady-state excitation of the vibrator can be shortened.

In the solid state oscillator circuit of the present invention, the minimum value of the amplification degree of the final stage amplifier among the multiple stages of amplifiers may be 1 or more.
In this way, the input signal of the final stage amplifier can be reduced when applying a voltage that saturates to the power supply voltage to the vibrator in order to reduce the time required for steady-state excitation of the vibrator. The amplifier can be operated.

  In the solid-state oscillator circuit of the present invention, a low-pass filter may be provided on the current-voltage conversion circuit and the conductive line of the amplifier.

  In this way, by providing a low-pass filter on the current-voltage conversion circuit and the conducting line of the amplifier, noise input together with the output current from the vibrator can be removed, and an output voltage with less noise is supplied to the vibrator. Can be applied. For this reason, it is possible to reduce the time required for the vibrator to perform steady excitation.

In the solid-state vibrator circuit according to the present invention, a rectifier circuit may be provided on the current-voltage conversion circuit and the conductive line of the variable current switch.
In the solid state oscillator circuit of the present invention, a smoothing circuit may be provided on the output side of the rectifier circuit.

  Since the output current from the vibrator and the output voltage from the current-voltage conversion circuit are alternating current, by converting to direct current through the rectifier circuit and the smoothing circuit in this way, for example, as a variable current switch Even when a MOSFET is used, the gate voltage of the MOSFET can be controlled by a DC voltage.

In the solid state oscillator circuit of the present invention, the resonator may be a crystal resonator or a ceramic resonator.
In this way, if a crystal resonator is used as a resonator, a stable transmission frequency can be obtained. Therefore, the vibration frequency of the resonator is stable against changes in the surrounding temperature, and a vibration gyro with better temperature characteristics. A physical quantity sensor such as a sensor can be realized.

  Further, if a ceramic oscillator is used as the vibrator, a physical quantity sensor such as a vibration gyro sensor that is small and low in cost can be realized.

Moreover, the physical quantity sensor of the present invention includes any one of the solid oscillator oscillation circuits described above,
And a detection circuit that detects a detection current output from the vibrator according to an external force applied to the vibrator.

The physical quantity sensor of the present invention may be a vibration type gyro sensor that detects Coriolis force generated in the vibrator.
Thus, by using the solid state oscillator circuit of the present invention for a physical quantity sensor, a gyro sensor for camera shake correction or a car navigation system gyro sensor that can be started quickly and is highly accurate. Can do.

  According to the present invention, the amplifier includes a variable current switch that changes the amplification degree. The variable current switch continuously changes the magnitude of the flowing current based on the output voltage from the current-voltage conversion circuit. In accordance with this, the amplification degree of the amplifier is continuously changed.

  For this reason, the amplification degree of the amplifier does not change extremely and continuously changes, so that the oscillation state of the vibrator does not become unstable when the amplification degree changes. A steady excitation can be made quickly.

  In addition, since the level change circuit and the reference voltage generator are not required for switching the switching means as in the prior art, the amplification degree is changed only by the variable current switch, so that the oscillation circuit can be reduced in size and saved. Electricity can be achieved.

  Therefore, by using such a solid oscillator oscillation circuit for a physical quantity sensor, for example, even when used as a camera shake correction sensor for a camera, the vibrator can be rapidly and constantly excited. The function can be activated quickly, and the activation time of the camera itself can be shortened.

FIG. 1 is a circuit diagram of a solid state oscillator circuit of the present invention. FIG. 2 is a graph showing changes in voltage values V _{1 to} V ₄ and the amplification degree of the solid oscillator oscillation circuit at the respective positions P _{1 to} P ₄ of the solid oscillator oscillation circuit of FIG. FIG. 3 is a circuit diagram showing an example of a rectifier circuit used in the solid state oscillator circuit of FIG. FIG. 4 is a circuit diagram of the first amplifier 16. FIG. 5 is a circuit diagram of the second amplifier 18. FIG. 6 is a circuit diagram of the solid state oscillator circuit of the present invention. FIG. 7A is a graph showing voltages V _{1 to} V ₃ at points P _{1 to} P ₃ when an offset adjustment circuit is provided on the output side of the first amplifier 16, and FIG. ₆ is a graph showing voltages V _{1 to} V ₃ at points P _{1 to} P ₃ when no offset adjustment circuit is provided on the output side of the amplifier 16. FIG. 8 is a circuit diagram of the solid state oscillator circuit of the present invention. FIG. 9 is a circuit diagram of the solid state oscillator circuit of the present invention. FIG. 10 is a block diagram of a physical quantity sensor using the solid state oscillator circuit of the present invention. FIG. 11 is a block diagram showing an example of a conventional solid oscillator oscillation circuit. FIG. 12 is a block diagram showing an example of a conventional solid oscillator oscillation circuit. FIG. 13 is a graph showing a change in the amplification degree of the voltage amplifier when the switch means is switched in the conventional solid oscillator oscillation circuit.

  Hereinafter, embodiments (examples) of the present invention will be described in more detail with reference to the drawings.

1 is a circuit diagram of a solid state oscillator circuit of the present invention, and FIG. 2 is a diagram illustrating voltage values V _{1 to} V ₄ and solid state oscillator circuits at positions P _{1 to} P ₄ of the solid state oscillator circuit of FIG. It is a graph which shows the change of the amplification degree.

In FIG. 1, reference numeral 10 indicates the solid oscillator oscillation circuit of the present invention as a whole.
The solid state oscillator circuit 10 includes a vibrator 12, a current-voltage conversion circuit 14, a first amplifier 16, a second amplifier 18, a first variable current switch 20 for the first amplifier 16, and a second amplifier. 18 comprises a second variable current switch 22, a rectifier circuit 24, and a smoothing circuit 26.

Reference numeral 50 denotes an operational amplifier, reference numeral 52 denotes a resistance element, reference numeral 54 denotes a capacitor, and reference numeral 56 denotes a ground terminal.
In the present embodiment, the vibrator 12 is not particularly limited as long as it is an element that oscillates at a specific frequency. For example, a crystal vibrator or a ceramic oscillator can be used.

In the solid state oscillator circuit 10 configured as described above, when a driving power source (not shown) is turned on, the vibrator 12 starts to oscillate and outputs a current Ixin. When this current Ixin is input to the current-voltage conversion circuit 14, the current-voltage conversion circuit 14 outputs a voltage V ₁ that is a voltage-converted signal (voltage at the position P ₁ ).

The voltage V ₁ is input to the first amplifier 16 and the rectifier circuit 24. Since the current Ixin and the voltage V ₁ output from the vibrator 12 are alternating current, they are rectified to direct current by the rectifier circuit 24 and the smoothing circuit 26 provided at the subsequent stage of the rectifier circuit 24.

Here, the rectifier circuit 24 is not particularly limited, but a diode may be used, and more preferably, the drive power supply is turned on by using a rectifier circuit as shown in FIG. The degree of amplification of the solid oscillator oscillation circuit 10 at the time can be improved.
In FIG. 3, reference numeral 58 denotes a transmission gate configured by connecting MOSFETs symmetrically, and reference numeral 60 denotes a comparator.

The voltage V ₄ output from the smoothing circuit 26 (voltage at the position P ₄ ) is input to the current control terminals of the first variable current switch 20 and the second variable current switch 22. The first variable current switch 20 and the second variable current switch 22 continuously change the amount of current flowing through the current passing path of the variable current switches 20 and 22 according to the magnitude of the voltage input to the current control terminal. It is configured to be controllable.

  The variable current switches 20 and 22 are not particularly limited as long as they are elements configured as described above, but MOSFETs can be preferably used. By using the gate terminal of the MOSFET as a current control terminal and using the drain-source path as a current passing path, the variable current switches 20 and 22 can be easily configured.

On the other hand, the voltage V ₁ input to the first amplifier 16 is amplified by the first amplifier 16 and output as the voltage V ₂ (voltage at the position P ₂ ).
Here, as shown in FIG. 4, the amplification degree of the first amplifier 16 includes the resistance values of the resistance elements 52a and 52b provided in the first amplifier 16, and the resistance component R of the variable current switch 20. Determined by the size of _T1 .

Specifically, when the resistance value of the resistance element 52a is Ra, the resistance value of the resistance element 52b is Rb, the current flowing through the resistance element 52a is I _Ra , and the current flowing through the variable current switch 20 is I _T1 , the first amplifier The amplification factor A ₁ = V ₂ / V ₁ of 16 is determined by the following equation (1).

Therefore, for example, when Ra is 100 kΩ and Rb is 10 kΩ, the maximum value is obtained when R _T1 ≈0 [Ω], and the amplification factor A ₁ of the first amplifier 16 is 11 times. Further, when R _T1 = ∞, the minimum value is obtained, and the amplification degree A ₁ of the first amplifier 16 is 1 time. Therefore, the amplification factor A ₁ of the first amplifier 16 can vary from ₁ to 11 times.

Similarly, the voltage V ₂ input to the second amplifier 18 is amplified by the second amplifier 18 and output as the voltage V ₃ (voltage at the position P ₃ ).
The second variable current switch 22 has a resistance element 52 connected in parallel to the current passage path.

As shown in FIG. 5, the amplification degree A ₂ of the second amplifier 18 configured in this way is the resistance value of the resistance element 52c, the resistance element 52d, and the resistance element 52e included in the second amplifier 18, and , Determined by the magnitude of the resistance component R _T2 of the second variable current switch 22.

Specifically, when the resistance value of the resistance element 52c is Rc, the resistance value of the resistance element 52d is Rd, and the resistance value of the resistance element 52e is Re, the amplification degree A ₂ = V ₃ / V _{2 of} the second amplifier 18 is set. Is determined by the following equation (2).

Therefore, for example, when Rc is 150 kΩ, Rd is 10 kΩ, and Re is 80 kΩ, when R _T2 ≈0 [Ω], Equation 3 is obtained, so that the amplification degree A ₂ of the second amplifier 18 is maximum. Value, 16 times.

On the other hand, when R _T2 = ∞, Equation 4 is satisfied, so that the amplification degree A ₂ of the second amplifier 18 is a minimum value, which is 2.6 times.

Unlike the first amplifier 16 shown in FIG. 4, even when the second variable current switch 22 is cut off, the amplification degree A ₂ does not become 1 time, so that the time required for steady-state excitation of the vibrator 12 is shortened. Therefore, when the voltage V ₃ saturated with the power supply voltage is applied to the vibrator 12, the input signal of the second amplifier 18 can be reduced, and the second amplifier 18 can be operated normally.

  Note that the amplification degrees of the first amplifier 16 and the second amplifier 18 can be changed as appropriate depending on, for example, the start-up time required for the physical quantity sensor provided with the solid oscillator oscillation circuit 10. If the maximum value of the amplification degree is increased, the time required for the vibrator 12 to perform steady excitation can be shortened.

  Further, a cut-off voltage is set for each of the first variable current switch 20 and the second variable current switch 22, and the voltage input to the current control terminals of the variable current switches 20 and 22 is the cut-off voltage. When the voltage becomes lower than the voltage, the magnitude of the current flowing through the current passing path of the variable current switches 20 and 22 becomes zero. It should be noted that “the magnitude of the current is 0” is sufficient if the magnitude of the flowing current is not completely zero, but may be almost zero.

  When the first variable current switch 20 and the second variable current switch 22 are constituted by MOSFETs as described above, the threshold voltage (Vth) of the MOSFET plays a role as a cutoff voltage. Become.

  The cut-off voltage Voff1 of the first variable current switch 20 is preferably set smaller than the cut-off voltage Voff2 of the second variable current switch 22.

  As is known, a MOSFET is an element that can control a drain-source current Id in accordance with a gate-source voltage Vgs. The threshold voltage of the MOSFET can be expressed by the absolute value of Vgs when a predetermined Id flows. The MOSFET has an operation mode of a depletion mode and an enhancement mode. In the depletion mode, Id decreases as the absolute value of Vgs increases, and in the enhancement mode, Id increases as the absolute value of Vgs increases.

  As already described, when the first variable current switch 20 and the second variable current switch 22 are configured by MOSFETs, the threshold voltage serves as a cutoff voltage. At this time, the expression of the magnitude of the cut-off voltage varies depending on whether the MOSFET is an element operating in the depletion mode or an element operating in the enhancement mode. Of course, it is possible to appropriately select in which mode the MOSFET that operates the first variable current switch 20 and the second variable current switch 22 is used depending on the device or system using the solid oscillator oscillation circuit 10. In the above description, the magnitude of the cutoff voltage means the magnitude as an absolute value.

  Thus, by setting the cut-off voltage Voff1 of the first variable current switch 20 to be smaller than the cut-off voltage Voff2 of the second variable current switch 22, the second variable current switch 22 is cut off first. That is, the current magnitude is zero.

  By configuring in this way, the amplification degree of the second amplifier 18 is fixed to a constant value before the amplification degree of the first amplifier 16, so that the feedback voltage to the vibrator 12 is stabilized. Become. The cut-off voltage Voff1 of the first variable current switch 20 and the cut-off voltage Voff2 of the second variable current switch 22 can be appropriately selected according to a desired time until the vibrator 12 is normally excited. it can.

Further, since the first amplifier 16 of this embodiment does not cut off and the amplification degree changes according to the output voltage V ₄ of the smoothing circuit 26, the first amplifier 16 has an AGC (Automatic Gain Control). It will operate as a control) amplifier. Therefore, even when the output current from the vibrator 12 changes due to an external factor such as a temperature change, the first amplifier 16 can compensate.

Further, it is preferable to set the minimum value of the amplification degree of the second amplifier 18 to be 1 or more. In this way, when the voltage V ₃ that saturates the power supply voltage is applied to the vibrator 12 in order to shorten the time required for the vibrator 12 to be normally excited, the input signal V of the second amplifier 18 is applied. ₂ can be reduced, and the second amplifier 18 can be normally operated.

Hereinafter, changes in the voltage values V _{1 to} V _{4 at} the respective positions P _{1 to} P ₄ of the solid vibrator oscillation circuit and the amplification degree of the solid vibrator oscillation circuit will be described with reference to FIG.
First, immediately after the power is turned on, the output voltage V1 of the current-voltage conversion circuit 14 is 0V, as the vibration of the vibrator 12 becomes large gradually voltages V ₁ is gradually increased.

Here, if the input current to the smoothing circuit 26 is I ₁ and the reference current of the smoothing circuit 26 is I _ref , the voltage V ₁ is 0 V immediately after the power supply is turned on, so that I ₁ << I _ref . V ₄ has a high value corresponding to the reference current I _ref of the smoothing circuit 26, and at least a value higher than the cutoff voltage of the variable current switches 20 and 22.

Therefore, the amplification degree of the first amplifier 16 and the second amplifier 18 is increased, and a large voltage is obtained as the voltage V ₃ immediately after the power supply is turned on as shown in FIG. By feeding back V ₃ to the vibrator 12, a high applied voltage can be applied to the vibrator 12. For this reason, the vibrator 12 quickly comes to steady excitation.

On the other hand, as the vibration of the vibrator 12 increases, the output current from the vibrator 12 increases, and accordingly, the voltage V ₁ also increases as shown in FIG. As the voltage V ₁ increases, the input current I ₁ to the smoothing circuit 26 increases, and accordingly the voltage V ₄ decreases as shown in FIG.

As the voltage V ₄ becomes smaller, as described above, the current passing through the variable current switches 20 and 22 becomes smaller, so that the amplification degree of the first amplifier 16 and the second amplifier 18 gradually becomes smaller.

Thus, as the output current from the vibrator 12 increases, the current passing through the variable current switches 20 and 22 decreases, so that the amplification degree of the solid vibrator oscillation circuit 10 immediately after the power supply is turned on is maximized. Thus, the degree of amplification gradually decreases.
Therefore, it is possible to reduce the time required until the vibrator 12 is normally excited, and when the output current from the vibrator 12 increases, the output voltage waveform of the amplifier is not saturated, and noise is reduced. Amplification does not make the oscillation state of the vibrator 12 unstable.

  Further, since the variable current switches 20 and 22 control the current value that passes continuously by the voltage input to the current control terminal, the amplification degree of the first amplifier 16 and the second amplifier 18 is extremely high. Since no ringing or the like occurs, the time required for steady excitation of the vibrator 12 can be shortened.

FIG. 6 is a circuit diagram of the solid state oscillator circuit of the present invention, and FIG. 7A is a voltage V ₁ at points P _{1 to} P ₃ when an offset adjustment circuit is provided on the output side of the first amplifier 16. graph showing ~V _3, FIG. 7 (B) is a graph showing the voltage V ₁ ~V ₃ at the point P ₁ to P ₃ when the output of the first amplifier 16 is not provided with the offset adjusting circuit.

  The solid state oscillator circuit 10 of this embodiment has basically the same configuration as the solid state oscillator circuit 10 shown in FIG. 1, and the difference is that it has an offset adjustment circuit 30. . In addition, the same code | symbol is attached | subjected to the same structural member, and the detailed description is abbreviate | omitted.

In general, an amplifier causes a phenomenon called offset due to variations in elements. The offset is a DC voltage component in which the output voltage is shifted with respect to the input voltage. When the offset occurs, the output voltage of the amplifier is saturated as shown in FIG. The amplitude of the output voltage V ₃ of the amplifier 18 becomes small, and the amplification degree as the solid oscillator oscillation circuit 10 becomes small.

For this reason, in the solid state oscillator circuit 10 of this embodiment, as shown in FIG. 6, a high-pass filter is provided as an offset adjustment circuit 30 on the output side of the first amplifier 16.
Thus, by providing the offset adjustment circuit 30, the offset of the first amplifier 16 is canceled, as shown in FIG. 7 (A), to a large amplitude of the output voltage V ₃ of the second amplifier 18 Can do.

  For this reason, since the amplification degree as the solid oscillator oscillation circuit 10 can be maintained large, it is possible to shorten the time required until the vibrator 12 is normally excited. In particular, when the amplification degree of the solid state oscillator circuit 10 immediately after the power supply is turned on is increased, the offset adjustment circuit 30 is provided on the output side of any amplifier, more preferably on the output side of all amplifiers. Accordingly, amplification can be performed appropriately, and the vibrator 12 can be steadily excited more rapidly.

FIG. 8 is a circuit diagram of the solid state oscillator circuit of the present invention.
The solid oscillator oscillation circuit 10 of this embodiment has basically the same configuration as the solid oscillator oscillation circuit 10 shown in FIGS. 1 and 6, and the difference is that it has a low-pass filter 32. It is. In addition, the same code | symbol is attached | subjected to the same structural member, and the detailed description is abbreviate | omitted.

When noise enters the oscillation circuit together with the output current Ixin from the vibrator 12, the noise component is amplified together, noise enters the input voltage V ₃ to the vibrator 12, and a stable voltage cannot be applied to the vibrator 12. The time required for the vibrator 12 to perform steady excitation becomes longer.

For this reason, in the solid state oscillator circuit 10 of this embodiment, a low-pass filter 32 is provided on the conducting line between the current-voltage conversion circuit 14 and the first amplifier 16, as shown in FIG.
Thus, by providing the low-pass filter 32, it becomes a voltage V ₃ with no noise can be applied to the vibrator 12.

Therefore, since a stable voltage V ₃ has can be applied to the vibrator 12, it is possible to shorten the time required to the vibrator 12 to be constant excitation.
The configuration shown in FIG. 8 is an example in which the offset adjustment circuit 30 is also provided, but of course, this may not be provided.

FIG. 9 is a circuit diagram of the solid state oscillator circuit of the present invention.
The solid state oscillator circuit 10 of this embodiment has basically the same configuration as the solid state oscillator circuit 10 shown in FIGS. 1, 6, and 8. The difference is that a third amplifier 34 is used. It is a point. In addition, the same code | symbol is attached | subjected to the same structural member, and the detailed description is abbreviate | omitted.

  In the solid state oscillator circuit 10 of this embodiment, a third amplifier 34 is provided in the subsequent stage of the second amplifier 18, and the third amplifier 34 continuously changes its amplification factor. The third variable current switch 36 is connected.

  In the first to third embodiments, the solid oscillator oscillation circuit 10 is configured with a two-stage amplifier, but is not particularly limited, and may be configured with a three-stage amplifier as in this embodiment. Although not shown in the embodiment, the amplifier may be composed of three or more stages of amplifiers.

  The number of stages of amplifiers can be set as appropriate depending on the degree of amplification required for the solid-state oscillator oscillation circuit 10. If a large degree of amplification is not required, it is not shown in the embodiment, but a single-stage amplifier is used. The solid oscillator oscillation circuit 10 may be configured as described above.

FIG. 10 is a block diagram of a physical quantity sensor using the solid state oscillator circuit of the present invention.
The solid oscillator oscillation circuit 10 used in this embodiment has basically the same configuration as the solid oscillator oscillation circuit 10 shown in FIGS. 1, 6, 8, and 9, and the same components are used. Are denoted by the same reference numerals, and detailed description thereof is omitted.

In FIG. 10, reference numeral 70 denotes the physical quantity sensor of the present invention as a whole.
The physical quantity sensor 70 includes a detection circuit 72 that detects a detection current output from the vibrator 12 according to the Coriolis force applied to the vibrator 12, in addition to the solid vibrator oscillation circuit 10.

  The detection circuit 72 includes current-voltage conversion circuits 14a and 14b that convert a detection current from the vibrator 12 into a voltage, a differential amplifier circuit 74 that receives output voltages from the current-voltage conversion circuits 14a and 14b, and for synchronous detection. A synchronous detection circuit 76, a phase adjustment circuit 78, and a low-pass filter 80 for removing harmonic components are provided.

  The detected current output from the vibrator 12 is converted into a voltage by the current-voltage conversion circuits 14a and 14b, and these voltages are input to the differential amplifier circuit 74, whereby common-mode noise is removed. The output voltage of the differential amplifier circuit 74 is synchronously detected by the synchronous detection circuit 76 using the output from the current-voltage conversion circuit 14 of the solid state oscillator circuit 10 as a reference signal for synchronous detection.

The reference signal for synchronous detection is input from the current-voltage conversion circuit 14 of the solid-state oscillator oscillation circuit 10 to the synchronous detection circuit 76 via the phase adjustment circuit 78.
The harmonic component is removed from the signal synchronously detected by the synchronous detection circuit 76 by the low-pass filter 80 and output as a detection signal.

  As described above, by configuring the physical quantity sensor 70 using the solid vibrator oscillation circuit 10 of the present invention, the time required for the vibrator 12 to perform steady excitation, that is, the physical quantity sensor 70 can be used after being turned on. The time required for the process can be shortened.

  In addition, since the solid state oscillator circuit 10 does not include a level determination circuit, a reference voltage generation unit, and the like, the circuit can be reduced in size and power consumption. Therefore, the physical quantity sensor of the present invention is, for example, a compact digital camera. It can be used as a vibration type gyro sensor such as a gyro sensor for hand shake correction or a gyro sensor for a navigation system such as a mobile phone.

  In addition, by using the physical quantity sensor 70 of the present invention as such a gyro sensor, it is possible to reduce the size of the entire device such as a compact digital camera or a mobile phone, and to improve the use time.

  The solid vibrator oscillation circuit of the present invention can rapidly and constantly excite the vibrator and can always stabilize the oscillation state of the vibrator. Therefore, it is particularly suitable as an oscillation circuit for a gyro sensor for camera shake correction or a gyro sensor for a car navigation system.

DESCRIPTION OF SYMBOLS 10 Solid oscillator oscillation circuit 12 Oscillator 14 Current voltage conversion circuit 16 1st amplifier 18 2nd amplifier 20 1st variable current switch 22 2nd variable current switch 24 Rectifier circuit 26 Smoothing circuit 30 Offset adjustment circuit 32 Low pass Filter 34 Third amplifier 36 Third variable current switch 50 Operational amplifier 52 Resistance element 52a Resistance element 52b Resistance element 52c Resistance element 52d Resistance element 52e Resistance element 54 Capacitor 56 Ground terminal 58 Transmission gate 60 Comparator 70 Physical quantity sensor 72 Detection circuit 74 Differential amplifier circuit 76 Synchronous detection circuit 78 Phase adjustment circuit 80 Low-pass filter 100 Oscillation circuit 101 Oscillator 102 Current-voltage conversion circuit 103 Rectifier circuit 105 Variable gain amplifier 106 Voltage amplifier 120 Amplifier 121 Switch means 1 5 reference voltage generator 126 level detector

Claims (13)

A vibrator,
A current-voltage conversion circuit that converts an output current from the vibrator into a voltage;
A solid-state oscillator oscillation circuit including an amplifier for amplifying an output voltage from the current-voltage conversion circuit,
The amplifier is composed of a plurality of stages of amplifiers,
Each of the multi-stage amplifiers includes a variable current switch that changes an amplification degree,
The variable current switch is configured to continuously change the magnitude of the flowing current based on the output voltage from the current-voltage conversion circuit, and to continuously change the amplification degree of the amplifier ,
Each of the variable current switches has a cut-off voltage,
When the input voltage to the variable current switch is equal to or lower than a predetermined cut-off voltage, the magnitude of the flowing current becomes 0, and the amplification degree of the amplifier is set to the minimum value.
After the vibrator starts oscillating, the variable current switch provided in another amplifier of the plurality of amplifiers is cut off earlier than the variable current switch provided in the first amplifier. Child oscillator circuit. The solid state oscillator circuit according to claim 1 , wherein the variable current switch is configured by a MOSFET. The solid state oscillator circuit according to claim 2 , wherein the variable current switch is configured by connecting a resistance element in parallel to a current passing path. Of the amplifier of the plurality of stages, a cut-off voltage of the variable current switch provided in the first stage of the amplifier, one of claims 1 to 3, characterized in that less than the cut-off voltage of the variable current switches provided in other amplifiers The solid oscillator oscillation circuit according to one. Wherein among the plurality of stages of amplifiers, solid vibrator oscillation circuit according to any one of claims 1 4, characterized in that provision of the offset adjustment circuit on the output side of at least one of the amplifiers. The solid-state oscillator circuit according to claim 5 , wherein the offset adjustment circuit is a high-pass filter. It said plurality of stages of amplifiers, solid vibrator oscillation circuit according to any one of claims 1 to 6, the minimum value of the amplification of the final stage of the amplifier is characterized in that 1 or more. The solid-state oscillator circuit according to any one of claims 1 to 7 , wherein a low-pass filter is provided on the current-voltage conversion circuit and a conducting line of an amplifier. The current-voltage conversion circuit and the solid oscillator oscillating circuit according to any one of claims 1 to 8, characterized in that providing a rectifying circuit conductor path of the variable current switch. The solid state oscillator circuit according to claim 9 , wherein a smoothing circuit is provided on an output side of the rectifier circuit. The transducer is a solid vibrator oscillation circuit according to claim 1, any one of 10, which is a crystal oscillator or ceramic resonator. A solid state oscillator circuit according to any one of claims 1 to 11 ,
A physical quantity sensor comprising: a detection circuit that detects a detection current output from the vibrator in accordance with an external force applied to the vibrator. The physical quantity sensor according to claim 12 , wherein the physical quantity sensor is a vibration type gyro sensor that detects a Coriolis force generated in the vibrator.

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