JPH08166244A - Driver of piezoelectric oscillator - Google Patents

Abstract

PURPOSE: To reduce the heat generation by the loss of a dielectric, by resonating a piezoelectric oscillator by B type with high acuteness always with antiresonant frequency. CONSTITUTION: An amplifier 3 amplifies the voltage applied to the reference capacity Cs connected to a piezoelectric oscillator 6a, and a differential amplifier 4 seeks the difference between drive voltage Vf and the voltage from the amplifier 3. Furthermore, a phase comparator 7 seeks the phase difference between the drive voltage Vf and the differential output voltage Vout, and controls the oscillation frequency of a voltage control oscillator 9, based on the phase comparison voltage Vp. By this PLL loop, the piezoelectric oscillator 6a is driven to resonate in B type with antiresonant frequency. By being capable of driving the piezoelectric element with B-type resonance, high acuteness can be obtained, and also even if it is driven with large amplitude, heating value can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive device for driving a piezoelectric vibrator used in a piezoelectric transformer, a piezoelectric motor, a vibration type gyroscope or the like, and in particular, resonating the piezoelectric vibrator at an anti-resonance frequency, The present invention relates to a piezoelectric vibrator driving device that can reduce heat generation.

[0002]

2. Description of the Related Art FIG. 7 shows a piezoelectric vibrator 1 with an AC drive power supply 2
Shows the state of being driven by. FIG. 8 shows the relationship between the current I flowing through the piezoelectric vibrator and the frequency f of the drive power when the AC drive power supply unit 2 is a constant voltage source. P
In a ZT ceramic oscillator or the like, two resonance points appear due to the piezoelectric reaction (due to the influence of the damping capacitance component of the piezoelectric oscillator). As shown in FIG. 8, when the frequency f of the drive power of the AC drive power supply unit 2 is changed, the maximum current and the minimum current appear at the points A and B. The point A appears at the resonance frequency fa when the piezoelectric vibrator 1 is in the resonance state, and the point B appears at the anti-resonance frequency fb when the piezoelectric vibrator 1 is in the anti-resonance state. Point A is a resonance point and point B is an anti-resonance point.

At point A (resonance point), the current flowing through the piezoelectric vibrator 1 is maximized, and at point B (anti-resonance point), the current flowing through the piezoelectric vibrator 1 is minimum and is applied to the piezoelectric vibrator 1. It is when the voltage reaches its maximum. 9A and 9B respectively show equivalent circuits of the piezoelectric vibrator, which are Cd1 and Cd.
d2 is the braking capacity, Cm1 and Cm2, Lm1 and Lm2, R
m1 and Rm2 are an equivalent capacitance, an equivalent inductance, and a vibration resistance at the time of resonance or antiresonance, respectively.

When the AC drive power source section 2 is a constant current source, the voltage applied to the piezoelectric vibrator 1 becomes minimal at the resonance frequency fa and the voltage applied to the piezoelectric vibrator 1 at the anti-resonance frequency fb. Become maximal. Here, in the following, the resonance state of the piezoelectric vibrator 1 when the current becomes maximum is called A-type resonance, and the anti-resonance state of the piezoelectric vibrator 1 when the voltage becomes maximum is called B-type resonance.

In order to drive the piezoelectric vibrator 1 in a resonance state, the frequency of the drive power from the AC drive power source section 2 is fa.
Or it must be close to fb. But the actual P
In a ZT ceramic oscillator or the like, the resonance frequency changes due to changes in the elastic coefficient of the piezoelectric oscillator and the like due to changes in environmental temperature and heat generation of the oscillator itself. Therefore, when driving the piezoelectric vibrator with the drive power having a constant frequency, it is difficult to always match the frequency of the drive power with the resonance frequency. Therefore, recently, a sensor for detecting the electric power acting on the piezoelectric vibrator 1 is provided while driving the piezoelectric vibrator 1 by the driving power, and based on the electric power detected by this sensor, or the driving voltage and the sensor A resonance point tracking type drive device is also considered in which the fluctuation of the resonance point of the piezoelectric vibrator 1 is tracked on the basis of the phase difference from the detected voltage, and drive power having a frequency close to the resonance frequency is always applied. .

[0006]

The resonance point tracking type drive device utilizes, for example, that the phase of the detection current or the detection voltage detected from the piezoelectric vibrator 1 changes at the resonance frequency fa, and A circuit configuration that tracks this phase change point is conceivable. However, in a PZT ceramic oscillator or the like, as shown in FIG. 8, the resonance frequency fa and the anti-resonance frequency fb exist in the close frequency bands, and the detected current is detected at both the resonance frequency fa and the anti-resonance frequency fb. Alternatively, since the phase of the detected voltage changes, it is actually difficult to distinguish between the resonance point and the anti-resonance point, and it is difficult to track only the resonance frequency fa, for example.

Also, as a resonance point tracking type drive circuit, an inductance element such as a coil is used to change the phase of the detection current or the detection voltage at the anti-resonance frequency fb to track only the resonance frequency fa on the circuit. It is also possible to let them do. However, when an inductance element such as a coil is interposed as described above, the current or voltage detected from the piezoelectric vibrator 1 is affected by the inductance, and as described above, the variation of the resonance frequency fa due to temperature change or the like. Becomes difficult to track with high accuracy.

Further, in a PZT ceramic oscillator or the like, the resonance sharpness Qa when resonating at the A type resonance at the resonance frequency fa is the resonance sharpness Qb when resonating at the B type resonance at the antiresonance frequency fb. Will be lower than. This is due to the dielectric loss of the piezoelectric vibrator. Therefore,
In the A-type resonance tracking type drive circuit that tracks the frequency fa,
High resonance sharpness cannot be obtained. Further, in the tracking of the A-type resonance, heat generation due to dielectric loss becomes large. Due to this heat generation, the fluctuation of the resonance frequency fa further increases, and when driving with a large amplitude, the amount of heat generation gradually increases, and eventually the piezoelectric vibrator may be damaged.

The present invention solves the above-mentioned conventional problems, in which the piezoelectric vibrator always resonates at the anti-resonance frequency fb (B
Drive device for a piezoelectric vibrator, in which the driving power is applied by following the frequency fb so that the resonance can be performed, and the piezoelectric vibrator can always vibrate at a frequency with a high resonance sharpness and a small heat generation amount. It is intended to be provided.

Further, according to the present invention, the detected voltage from the piezoelectric vibrator is not affected by the inductance, and the fluctuation of the anti-resonance frequency can be always tracked with high accuracy to supply the driving power. It is an object to provide a drive device for a vibrator.

[0011]

A drive device for a piezoelectric vibrator according to the present invention is a differential device for obtaining a difference between a reference capacitor connected to the piezoelectric vibrator and a voltage applied to the reference capacitor from a voltage applied to the piezoelectric vibrator. Means, a phase comparator for comparing the phase of the drive signal applied to the piezoelectric vibrator and the phase of the differential output from the differential means, and a voltage controlled oscillator whose oscillation is controlled based on the output of the phase comparator. And a drive signal based on the oscillation frequency from the voltage controlled oscillator is applied to the piezoelectric vibrator.

In the above, the reference capacitance is connected in series to the piezoelectric vibrator, the voltage applied to the reference capacitance is amplified by the amplifier, and the differential means uses the drive voltage applied to the piezoelectric oscillator and the reference capacitance and the amplifier. It is possible that the difference from the amplified voltage is sought. Here, when the reference capacitance Cs is n times the braking capacitance Cd2 of the piezoelectric vibrator, it is preferable that the amplification degree of the amplifier is approximately (n + 1) times.

When the piezoelectric vibrator is driven by a constant voltage, the phase difference compared by the phase comparator is 90.
When the oscillating frequency of the voltage controlled oscillator is controlled on the basis of the phase difference, or when the piezoelectric vibrator is driven by a constant current, the phase difference compared by the phase comparator is based on 0 degree. As a result, the oscillation frequency of the voltage controlled oscillator is controlled.

[0014]

FIG. 3 illustrates the operation of the present invention.
A state in which a piezoelectric vibrator 1 such as a PZT ceramic vibrator is driven by an AC driving power supply unit 2 is shown. In the circuit that detects the voltage applied to the piezoelectric vibrator 1, an equivalent circuit of the piezoelectric vibrator 1 can be represented by FIG. Here, Cd2 is a braking capacity. When the piezoelectric vibrator 1 is clamped so as not to vibrate and the drive voltage Vf is applied, only the voltage Vd applied to the braking capacitance Cd2 is obtained. This voltage Vd is the voltage applied to the braking capacitance Cd2. Equivalent capacitance Cm2 at resonance, equivalent inductance Lm2, vibration resistance R
m2 can be expressed as being connected in parallel, and the voltage Vm applied to this portion is the motional voltage at the B-type resonance.

In the present invention, the reference capacitance Cs is applied to the piezoelectric vibrator 1.
Are connected in series, and the non-connection side of the reference capacitance Cs is grounded (or has a predetermined potential). The reference voltage applied to this reference capacitance Cs is indicated by Vs. In the present invention, the difference of the reference voltage Vs is obtained from the voltage (Vd + Vm) applied to the piezoelectric vibrator 1, and the braking capacitance C
The effect of d2 is canceled or reduced.

In FIG. 3, an amplifier 3 for amplifying the reference voltage Vs applied to the reference capacitor Cs is provided, and the output voltage from the amplifier 3 is further subtracted from the drive voltage Vf applied to the piezoelectric vibrator 1 and the reference capacitor Cs. A differential amplifier (op-amp) 4 is provided as a moving differential means. FIG.
Then, the reference capacitance Cs is n times the braking capacitance Cd2, and the voltage amplification factor of the amplifier 3 is set to approximately (n + 1) times. The current flowing through the piezoelectric vibrator 1 and the reference capacitance Cs is I
Assuming that f, the voltages Vf and Vs are expressed by Equation 1.

[0017]

[Equation 1]

The differential output Vout in FIG. 3 is calculated from Vf to Vs.
(N + 1) times the differential voltage. Therefore, Vout is calculated by the equation 2.

[0019]

[Equation 2]

As shown in Equation 2, the differential output Vout obtained from the differential amplifier 4 becomes equal to the motional voltage Vm. That is, the voltage (Vd + V
From m), the voltage Vd applied to the braking capacitance Cd2 is removed on the circuit. FIG. 4 shows frequency characteristics of the motional voltage Vm that acts on an equivalent circuit in which the equivalent capacitance Cm2, the equivalent inductance Lm2, and the vibration resistance Rm2 at the time of resonance are connected in parallel. In FIG. 4, the motional voltage Vm peaks at the anti-resonance frequency fb, and a characteristic that is substantially symmetrical with respect to changes in the frequency f is obtained.

This is because the voltage component applied to the braking capacitance Cd2 is equivalently canceled on the circuit by multiplying the voltage Vs applied to the reference capacitance Cs by (n + 1) and differentiating Vs (n + 1) from Vf. It means that. When the voltage component of the braking capacitance Cd2 is canceled and substantially only the motional voltage Vm is detected, at this detection output (differential output) Vout, the resonance of the piezoelectric vibrator when the resonance frequency fa, that is, the current becomes maximum. The points disappear and only the peak of the anti-resonance frequency fb is obtained.

From the above, when the circuit shown in FIG. 3 is used, the antiresonance frequency fb can be detected by the differential output Vout. Therefore, if the drive frequency of the AC drive power supply unit 2 is set to always track the anti-resonance frequency fb obtained at Vout, the piezoelectric vibrator 1 can resonate at the anti-resonance frequency fb, that is, the piezoelectric element. It is possible to cause the vibrator 1 to always resonate with the B-type resonance.

Next, the AC drive power source unit 2 to the piezoelectric vibrator 1
5 and 6 show the relationship between the phase of the drive voltage Vf given to the circuit and the phase of Vout. 5 and 6 show that in the circuit shown in FIG. 3, Cs has almost the same value as Cd2 (n =
1), the case where the amplification factor of the amplifier 3 is almost doubled (n + 1 = 2) is shown. In FIGS. 5 and 6, the horizontal axis represents the frequency f. Vout is a differential output from the differential amplifier 4, and the unit of the vertical axis corresponding to this is represented by (dB). F is the phase difference between the drive voltage Vf and the differential output Vout, and the unit of the vertical axis corresponding to this is (degree: deg).

FIG. 5 shows a case where the AC drive power source section 2 is a constant voltage source. In FIG. 5, the peak of Vout appears at the anti-resonance point (anti-resonance frequency fb) of the piezoelectric vibrator, but the phase difference F between the drive voltage Vf and the differential output Vout changes at the anti-resonance point, and the peak of Vout. The phase difference at time (anti-resonance point) is 90 degrees. FIG. 6 shows a case where the AC drive power supply unit 2 is a constant current source. Also in this case, the peak of Vout appears at the anti-resonance point, the phase difference F between the drive voltage Vf and the differential output Vout changes at the peak point (anti-resonance point), and the phase difference at the peak time is 0 degree. is there.

From FIG. 5 and FIG. 6, the phase difference between the phase of the driving voltage Vf and the phase of the differential output voltage Vout is obtained by the phase comparator, and the voltage controlled oscillator (based on the phase comparison voltage from the phase comparator ( By controlling the oscillation frequency of the VCO) and applying the driving power based on this oscillation frequency to the piezoelectric vibrator 1, it is possible to drive the anti-resonance frequency fb, that is, the resonance point of the B-type resonance at all times.

From FIG. 5, when the piezoelectric vibrator 1 is driven by a constant voltage, the oscillation frequency of the voltage controlled oscillator is based on the case where the phase difference between both voltages input to the phase comparator is 90 degrees. Should be controlled. Further, from FIG. 6, when the piezoelectric vibrator is driven by a constant current, if the oscillation frequency of the voltage controlled oscillator is controlled with reference to the phase difference of both voltages input to the phase comparator being 0 degree, It will be good.

If the AC drive power source section 2 is constructed mainly by the phase comparator and the voltage controlled oscillator, the piezoelectric vibrator 1 can be resonantly driven so as to always track the anti-resonance frequency fb. As described above, when the piezoelectric vibrator 1 is driven by the B-type resonance, the resonance sharpness Qb is high, the dielectric loss is small, the heat generation of the piezoelectric vibrator 1 can be suppressed, and the vibration is driven at a large amplitude. The fever of can be made very small.

Further, in the detection system of the voltage applied to the piezoelectric vibrator 1, since the inductance element is not present, the frequency of the detection voltage is not affected by the inductance, and as shown in FIG. 5 and FIG. The resonance point (resonance point in B-type resonance) and the change point of the phase difference can be made to correspond one-to-one. Therefore, the piezoelectric vibrator can always be driven at the anti-resonance frequency fb by using a simple circuit such as a general PLL circuit using a phase comparator or a voltage controlled oscillator.

As shown in FIG. 3, when the reference capacitance Cs is n times the braking capacitance Cd2, the amplification degree of the voltage amplifier 3 is preferably (n + 1) times, but the amplification of the voltage amplifier 3 is preferable. Even if the degree is not exactly (n + 1) times, it is possible to obtain the peak output at the anti-resonance frequency by approximating that in FIG. Also, the above n is not limited to an integer, and may be 1.5 or 2.2.
May be a decimal number, or may be a fraction or a decimal number such as 1/2 or 1/3 less than 1.

In the present invention, it is important to remove the voltage component applied to the braking capacitance Cd2 of the piezoelectric vibrator 1,
Therefore, the reference capacitance Cs is used. Therefore, for example, instead of providing the amplifier 3, an amplifier is provided in the portion (a) and the amplification factor of this amplifier is set to a predetermined value to cancel the voltage Vd applied to the braking capacitance from the voltage applied to the piezoelectric vibrator 1. It is also possible to reduce or decrease.
Further, the differential means in the present invention is not necessarily limited to the differential amplifier 4, and a summing circuit may be used depending on the phase of the operating voltage.

[0031]

EXAMPLES Examples of the present invention will be described below. The first embodiment shown in FIG. 1 shows a driving device in the case where the piezoelectric vibrator is a piezoelectric transformer 6 using a PZT ceramic vibrator. In the piezoelectric transformer 6, the primary side piezoelectric vibrator 6a has a dielectric polarization direction P1 and the secondary side piezoelectric vibrator 6b has a dielectric polarization direction P2. The piezoelectric vibrator 6a on the primary side is provided with electrodes 5a and 5b sandwiching the polarization direction, and the piezoelectric vibrator 6b on the secondary side is provided with an electrode 5c on the end face. Electrodes 5a and 5 of the piezoelectric vibrator 6a on the primary side
The voltage E1 of the drive voltage is applied to b, and the voltage E2 is output from the electrodes 5b and 5c in the piezoelectric vibrator 6b on the secondary side. As shown in the equivalent circuit diagram of FIG. 3, the voltage E1 applied to the primary-side piezoelectric vibrator 6a is Vd + Vm,
That is, it is the voltage applied to the piezoelectric vibrator 1.

The piezoelectric vibrator 6a on the primary side of the piezoelectric transformer 6 corresponds to the piezoelectric vibrator 1 in the equivalent circuit shown in FIG. The reference capacitance Cs is connected in series to the electrode 5b of the piezoelectric vibrator 6a on the primary side, and the non-connection side of the reference capacitance Cs is grounded (or has a predetermined potential). A line L extracted from the middle of the reference capacitance Cs and the electrode 5b
The potential of 1 is Vs in FIG. The voltage amplifier 3 amplifies the voltage Vs applied to the reference capacitance Cs. The reference capacitance Cs is the braking capacitance Cd2 of the piezoelectric vibrator 6a on the primary side.
The amplification factor of the voltage amplifier 3 is approximately (n +
It is set to 1). Preferably, n = 1, the reference capacitance Cs has almost the same value as the damping capacitance Cd2, and the amplification degree of the voltage amplifier 3 is almost double.

The AC drive power supply unit 2 is composed of a phase comparator 7, a loop filter 8, a voltage controlled oscillator (VCO) 9, and an amplifier (power amplifier) 10. Line L2
A drive signal output from the amplifier 10, that is, a drive voltage Vf is applied to the. Differential amplifier (op amp)
4, the difference between the drive voltage Vf of the line L2 and the amplified voltage {Vs (n + 1)} from the voltage amplifier 3 is obtained. The differential output from the differential amplifier 4 corresponds to Vout in FIG.
The voltage of the differential output line L3 is Vout = Vm (see Formula 2).

In the phase comparator 7, the phase of the drive voltage Vf on the line L2 is shaped by the waveform shaping circuit 16 and the differential output voltage Vout on the line L3 is shaped by the waveform shaping circuit 15. The phase difference with the phase of the applied voltage is detected. The phase difference detection output from the phase comparator 7 is passed through a loop filter (low-pass filter) 8 to remove high frequency components, and a phase comparison output, that is, a phase comparison voltage Vp is obtained. This phase comparison voltage Vp is given to the voltage controlled oscillator 9. The oscillation frequency of the voltage controlled oscillator 9 is controlled by the phase comparison voltage Vp. The output power from the voltage controlled oscillator 9 is amplified by the amplifier 10 to become a driving power (driving signal), which is given to the electrode 5a (between the electrode 5a and the ground) of the piezoelectric vibrator 6a on the primary side by the line L2.

Here, when the AC drive power supply unit 2 applies a constant voltage drive power to the electrode 5a (between the electrode 5a and the ground) via the line L2, the level of the drive voltage Vf and the differential output voltage Vout is increased. When the phase difference is 90 degrees, the phase comparison voltage V
p becomes a predetermined value. The oscillation frequency of the voltage controlled oscillator 9 is set on the basis of when the phase comparison voltage Vp is the predetermined value. Then, the drive voltage Vf and the differential output voltage Vout
When the phase difference between the phase shift voltage Vp and the phase shift voltage deviates from 90 degrees, the phase comparison voltage Vp fluctuates from a predetermined value and the oscillation frequency of the voltage controlled oscillator 9 changes. The phase comparison voltage Vp is 0 when the compared phase difference is 0 degrees, Vdd when the phase difference is 180 degrees (π), and 90 degrees (π / 2) when the phase difference is 90 degrees (π / 2). Is a predetermined value of Vdd / 2.

Due to the PLL loop shown in FIG. 1, the piezoelectric vibrator 6a on the primary side of the piezoelectric transformer 6 has a driving power (constant power) of a frequency at which the phase difference between the driving voltage Vf and the differential output voltage Vout is always 90 degrees. Voltage drive power) will be given. That is, as described based on FIGS. 3 and 5, the piezoelectric vibrator 6a on the primary side is always driven so as to follow the anti-resonance frequency fb (frequency of B-type resonance).

Further, the AC drive power source section 2 causes the line L
When a constant-current drive power is applied from 2 to the electrode 5a (between the electrode 5a and the ground), the drive voltage Vf and the differential output voltage V
When the phase difference from out is 0 degree, the phase comparison voltage Vp becomes a predetermined value. The oscillation frequency of the voltage controlled oscillator 9 is set with reference to the phase comparison voltage Vp having a predetermined value. When the phase difference deviates from 0 degree, the oscillation frequency of the voltage controlled oscillator 9 changes accordingly. Phase comparison voltage V in this case
For example, p is Vdd when the phase difference compared is −180 degrees (−π) and Vdd when the phase difference is 180 degrees (+ π), and V is a predetermined value when the phase difference is 0 degrees. / 2. That is, by the PLL loop, the drive voltage Vf is always
The drive power having a frequency such that the phase difference between the differential output voltage Vout and the differential output voltage Vout is 0 degree is applied to the piezoelectric vibrator 6a on the primary side of the piezoelectric transformer 6.

As described above, in both the constant voltage drive and the constant current drive, the piezoelectric vibrator 6a on the primary side of the piezoelectric transformer 6 is used.
Resonates at the anti-resonance frequency fb, and even when the anti-resonance frequency fb of the piezoelectric vibrator fluctuates due to heat or the like, it is driven so as to always track this fluctuation. Since the piezoelectric vibrator is always resonantly driven at the anti-resonance frequency fb, the resonance sharpness Qb of the piezoelectric vibrator 6a on the primary side becomes high. Also, because it is a resonance drive with a small dielectric loss,
The heat generated by the piezoelectric transformer 6 is also small.

FIG. 2 shows a second embodiment of the present invention.
In the second embodiment, a driving device of the mode conversion type motor 11 including the piezoelectric vibrator 1 is shown. In the mode conversion motor 11, a plurality of piezoelectric vibrators 1 vibrating in the thickness direction are laminated and interposed between the base 12 and the vibrating body 13. The tip of the vibrating piece 13a extending from the vibrating body 13 is an inclined surface, and the rotor 14 also rotates about the inclined axis O. When the vibrating body 13 vibrates in the left-right direction in the drawing due to the vibration of the piezoelectric vibrator 1 in the thickness direction, the vibration is converted into a force in the rotating direction of the rotor 14 at the contact portion between the vibrating piece 13a and the rotor 14. To be done.

The circuit configuration of the drive device for the piezoelectric vibrator 1 of the mode conversion motor 11 is the same as that shown in FIG. Each piezoelectric vibrator 1 has electrodes sandwiched from the thickness direction, and the reference capacitance Cs (= n · Cd2) is connected in series to one electrode. The amplification degree of the voltage amplifier 3 that amplifies the voltage Vs applied to the reference capacitance Cs is (n + 1). In the phase comparator 7, the drive voltage Vf and the differential output voltage V
The phase difference from out is detected via the waveform shaping circuits 15 and 16. The loop filter 8, voltage controlled oscillator 9 and amplifier 10 are also the same as those shown in FIG.

Also in the embodiment of FIG. 2, when the piezoelectric vibrator 1 is driven at a constant voltage, the driving voltage Vf and the differential output voltage Vou
When the phase difference from t is 90 degrees, the phase comparison voltage Vp becomes a predetermined value (Vdd / 2), and the oscillation frequency of the voltage controlled oscillator 9 is set with this as a reference. When the piezoelectric vibrator 1 is driven by a constant current, the phase comparison voltage Vp becomes a predetermined value (Vdd / 2) when the phase difference between the drive voltage Vf and the differential output voltage Vout is 0 degree, and this is used as a reference. The oscillation frequency of the voltage controlled oscillator 9 is set as. The piezoelectric vibrator 1 shown in FIG. 2 is also supplied with drive power having a frequency that resonates at the anti-resonance frequency fb at all times, has a high resonance sharpness Qb, and can drive a motor with a small amount of heat generation.

Further, in the embodiments shown in FIGS. 1 and 2, the amplification degree of the voltage amplifier 3 does not need to be strictly (n + 1) times, and if the amplification degree is close to (n + 1) times, the piezoelectric vibrator is obtained. Can be B-type resonated at the anti-resonance frequency fb. Further, since the reference capacitance Cs is used and an inductance element such as a coil is not used, the differential output voltage V
Even if the anti-resonance frequency fb of the piezoelectric vibrator fluctuates due to a temperature change or the like, it is possible to always provide the driving power that tracks the out or the driving power without being affected by the inductance.

The piezoelectric vibrator of the present invention is not limited to the one used in the device shown in FIG. 1 or FIG. 2, but can be applied to a vibration type gyroscope or an acceleration sensor. In a vibrating gyroscope, for example, a constant-elastic material such as an elinvar is vibrated by a piezoelectric vibrator, and this is installed in a rotating system to vibrate the elastic material backward by a Coriolis force, which is different from the driving direction. Thus, the vibration due to the Coriolis force is detected and the angular velocity of the rotating system is obtained. The present invention can be applied as a driving device of the piezoelectric vibrator in the vibration type gyroscope.

[0044]

As described above, according to the present invention, the piezoelectric vibrator can always resonate at the resonance frequency of B-type resonance,
The resonance sharpness can be increased, and heat generation due to dielectric loss can be suppressed.

Further, since an inductance component such as a coil is not used, even if the resonance frequency of the piezoelectric vibrator fluctuates due to heat or the like, it is possible to highly accurately track and drive the fluctuation of the resonance frequency.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing a driving device for driving a piezoelectric transformer as a piezoelectric vibrator, showing a first embodiment of the present invention;

FIG. 2 is a circuit block diagram showing a driving device for driving a piezoelectric vibrator of a piezoelectric motor according to a second embodiment of the present invention,

FIG. 3 illustrates the principle of the present invention, and is a circuit configuration diagram including an equivalent circuit of a piezoelectric vibrator,

4 is a diagram showing the frequency characteristics of the differential output voltage of the circuit of FIG.

5 is a diagram showing a differential output and a phase difference between the drive voltage and the differential output voltage when the piezoelectric vibrator is driven at a constant voltage in the circuit of FIG.

6 is a diagram showing a differential output and a phase difference between a driving voltage and a differential output voltage when a piezoelectric vibrator is driven by a constant current in the circuit of FIG.

FIG. 7 is a block diagram showing a conventional piezoelectric vibrator driving device;

8 is a diagram showing a frequency characteristic of a current flowing through the piezoelectric vibrator when the piezoelectric vibrator is driven at a constant voltage in FIG. 7;

9A is an equivalent circuit diagram showing a piezoelectric vibrator during A-type resonance, and FIG. 9B is an equivalent circuit diagram showing a piezoelectric vibrator during B-type resonance.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric vibrator 2 AC drive power supply section 3 Voltage amplifier 4 Differential amplifier 6 Piezoelectric transformer 7 Phase comparator 8 Loop filter 9 Voltage controlled oscillator 10 Amplifier 11 Mode conversion type motor 15, 16 Wave shaping circuit

Claims (5)

[Claims] 1. A reference capacitor connected to a piezoelectric vibrator, differential means for obtaining a difference between a voltage applied to the piezoelectric vibrator and a voltage applied to the reference capacitor, and a phase difference between a drive signal given to the piezoelectric vibrator. A phase comparator that compares the phase of the differential output from the moving means and a voltage controlled oscillator whose oscillation is controlled based on the output of the phase comparator, and a drive signal based on the oscillation frequency from the voltage controlled oscillator. Is provided to the piezoelectric vibrator, and a driving device of the piezoelectric vibrator. 2. The reference capacitor is connected in series to the piezoelectric vibrator, the voltage applied to the reference capacitor is amplified by an amplifier, and in the differential means, the drive voltage applied to the piezoelectric vibrator and the reference capacitor, and the amplifier. The drive device for a piezoelectric vibrator according to claim 1, wherein a difference from the amplified voltage is obtained. 3. The reference capacitance is a braking capacitance Cd2 of a piezoelectric vibrator.
The amplification factor of the amplifier is approximately (n + 1)
The drive device for a piezoelectric vibrator according to claim 2, wherein the number is double. 4. The oscillating frequency of the voltage controlled oscillator is controlled on the basis of when the piezoelectric vibrator is driven by a constant voltage and the phase difference compared by the phase comparator is 90 degrees. A drive device for a piezoelectric vibrator according to claim 1. 5. The oscillating frequency of the voltage controlled oscillator is controlled on the basis of when the piezoelectric vibrator is driven by a constant current and the phase difference compared by the phase comparator is 0 degree. A drive device for a piezoelectric vibrator according to claim 1.