JP2920935B2 - Drive circuit for piezoelectric element - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving circuit for a piezoelectric element, and is suitably applied to, for example, a driving circuit for driving an actuator of a magneto-optical disc device.

B. Outline of the Invention According to the present invention, a piezoelectric element can be efficiently driven with a simple configuration by boosting and applying an AC component of a drive signal in a piezoelectric element drive circuit.

C Conventional Technology Conventionally, in a magneto-optical disk device, an actuator using electromagnetic force (hereinafter referred to as an electromagnetic actuator) is used.
Is driven by a focus error signal, whereby the objective lens mounted on the electromagnetic actuator is held at a predetermined position with respect to the magneto-optical disk, so that desired information is reliably recorded and reproduced. I have.

D. Problems to be Solved by the Invention Incidentally, an actuator using a piezoelectric element (hereinafter referred to as a piezoelectric actuator) has a feature that it can be driven at a high speed with a simple configuration as compared with an electromagnetic actuator.

Therefore, if the piezoelectric actuator is used instead of the electromagnetic actuator, it is considered that the entire configuration can be simplified and the objective lens can be driven at a high speed.

Furthermore, electromagnetic actuators use electromagnetic force, so that magnetic flux required for driving may leak to the outside of the electromagnetic actuator, whereas piezoelectric actuators use the electrostrictive effect of the piezoelectric element to prevent leakage. There is a feature that no magnetic flux is generated.

Therefore, if a piezoelectric actuator is used in the magneto-optical disc device, the effect of the leakage magnetic flux on the magneto-optical disc can be effectively avoided, and the magnetic shield around the objective lens is omitted, thereby simplifying the overall configuration. It is thought to get.

That is, as shown in FIG.
Giving S _FE to the amplifier circuit 3 via a phase compensation circuit 2, after amplified to a predetermined signal level, considered may be applied to the piezoelectric element 4 of the piezoelectric actuator.

However, the piezoelectric element has a feature that the displacement amount is small with respect to the applied voltage, and is 0.
A displacement of only about 5 μm to about 1 μm can be obtained.

On the other hand, in a magneto-optical disc device, it is necessary to displace the objective lens by about 100 [μm] with respect to a predetermined reference position.

Therefore, in order to drive the objective lens with the piezoelectric actuator, it is necessary to drive the piezoelectric element with an amplitude of about 200 [V].

However in practice, in order to amplify the Fuo Kas error signal S _FE to the amplitude of about 200 [V] in amplitude circuit 3 needs to drive the amplifier circuit 3 in ± 100 to 300 [V] about that of the power supply is there.

Consequently, the result is that the power of the number [W] is consumed by the amplifier circuit 3 itself, and there is a problem that the power consumption increases as the whole magneto-optical disc device.

Further, since the power supply voltage is increased, the configuration of the amplifier circuit 3 becomes complicated, and there is a problem that the configuration of the magneto-optical disk device becomes complicated despite the use of the piezoelectric actuator.

The present invention has been made in view of the above points, and has as its object to propose a driving circuit for a piezoelectric element having a simple configuration and low power consumption.

Means for Solving E Problem In order to solve such a problem, in the present invention, a piezoelectric element 23 for driving an actuator 24 using the piezoelectric element 23 is used.
Drive circuit 50, the DC component S of the predetermined drive signal _SFE
Step-up means 61 for stepping up _DC , step-up transformer 55 for stepping up the _AC component _SAC of the drive signal _SFE , and step-up transformer 5
The AC component S _ACO obtained by boosting from step 5 is
And an application means 24 for applying the DC component V _DC obtained by boosting the voltage to the piezoelectric element 23 while superimposing the DC component V _DC .

F action boosting means 61 for boosting the DC component S _DC of the drive signal S _FE ,
Step-up transformer that steps up the _AC component S _AC of the drive signal S _FE
55 and an application unit 24 for applying the AC component S _ACO obtained by boosting the boost transformer 55 to the DC component V _DC obtained by boosting the voltage from the boosting unit 61 and applying the DC component V _DC to the piezoelectric element 23. With this configuration, the drive circuit 50 can be driven with a low power supply voltage, so that power consumption can be reduced and the configuration can be simplified.

G Example Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

In FIG. 1, reference numeral 10 denotes a magneto-optical disc device as a whole, which records and reproduces predetermined information on a magneto-optical disc 12 which is driven to rotate by a spindle motor 11.

That is, in the magneto-optical disc device 10, the light beam LA1 is emitted from the optical information detection unit 13 fixed at a predetermined position, and the light beam LA1 is bent at a predetermined position and then condensed by an objective lens, thereby obtaining a magneto-optical disk. An optical spot is formed on a predetermined recording track on the disk 12.

That is, the magneto-optical disc device 10 responds to a predetermined drive signal and a tracking error signal.
A linear actuator (not shown) adapted to be displaced in the radial direction of the actuator, and as shown in FIG. 2, fixing a bimorph 23 with an attachment member 22 to an arm 21 of the linear actuator. Piezo actuator 24
Is attached to the linear actuator.

The bimorph 23 is configured by laminating two piezoelectric elements 23A and 23B with a cushioning material 25 for preventing resonance therebetween, whereby the applied voltage V of the piezoelectric elements 23A and 23B is _In accordance with _E , the tip is displaced in the vertical direction.

Further, as shown in cross section in FIG.
The reference numeral 23 has a through hole 26 at the tip, and an objective lens 27 and a right-angle prism 28 are mounted on the top of the through hole 26.

As a result, the light beam LA1 emitted from the optical information detection unit 13
Is incident on the right-angle prism 28, and the light beam LA1 is bent toward the magneto-optical disc 12 and is incident on the objective lens 27.

On the other hand, a magnetic head portion 30 is arranged below the through hole 26 of the bimorph 23, so that the light beam passing through the magnetic head portion 30 is focused on the magneto-optical disk 12. Has been made.

That is, as shown in FIG. 4, in the magnetic head portion 30, the transparent member 31 is formed using, for example, a spattering technique.
A magnetic film 32 is formed thereon, and at this time, a through hole 33 concentric with the through hole 26 is formed in the center of the magnetic film 32.

Thus, the light beam LA1 incident on the objective lens 27 is
The light is condensed on the magneto-optical disc 12 through the through hole 26, the transparent member 31, and the through hole 33.

Further, in the magnetic head section 30, a coil 36 is printed on the magnetic film 32, and the coil 36 is printed with a predetermined drive current.
By driving 33, a modulation magnetic field whose polarity is inverted in accordance with the recording information is applied to the magneto-optical disk 12.

Thus, by driving the linear actuator according to the predetermined drive signal and the tracking error signal,
As shown by the arrow b, the piezoelectric actuator 24 can be driven and controlled in the radial direction of the magneto-optical disk 12, whereby the irradiation position of the light beam LA1 is moved to a predetermined recording track to perform tracking control, and the light is controlled. Beam LA
A desired modulation magnetic field can be applied to one irradiation position.

Further, the piezoelectric actuator 24 is driven to drive the objective lens 27.
Can be displaced in the vertical direction as shown by the arrow a, whereby the piezoelectric actuator 24 is driven by a predetermined drive signal, and the objective lens for the magneto-optical disc 12 is moved.
The position of 27 can be held in a predetermined position.

As a result, in the magneto-optical disc 12, the light beam LA1 is applied to the perpendicular magnetization film 40 sandwiched between the substrate 38 and the protective film 39, and at the same time, a modulation magnetic field is applied.
The desired information can be thermomagnetically recorded at the irradiation position.

On the other hand, the reflected light beam reflected by the magneto-optical disk 12 is guided to the optical information detection unit 13 by going backward through the through hole 33, the transparent member 31, the through hole 26, the objective lens 27, and the right-angle prism 28. Thereby, the optical information recorded on the magneto-optical disc 12 is reproduced, and the tracking error signal and the focus error signal are detected. Based on the tracking error signal and the focus error signal, the linear operation is performed. Eta and piezoelectric actuator
24 has been made to drive.

That is, as shown in FIG. 5, the driving circuit 50 of the piezoelectric actuator is subjected to Fuo Kas error signal S _FE to the phase compensation circuit 2, adapted to provide its output signal to a low-pass filter circuit 51 and the high-pass filter circuit 52 ing.

Low-pass filter circuit 51 and high-pass filter circuit 52
The cut-off frequency is selected to a frequency lower than the rotational frequency of the magneto-optical disc, thereby being adapted to separate the Fuo Kas error signal S _FE to a direct current component S _DC and AC components S _AC.

When the magneto-optical disk is actually loaded on the spindle motor, dust and the like may be mixed between the disk and the magneto-optical disk. is there.

Therefore, as shown in FIG. 6, the focus error signal S _FE
In FIG. 6 (A), while the DC level V _DC fluctuates by an amount corresponding to the translation of the position of the magneto-optical disk 12, the warp and surface condition of the magneto-optical disk 12 cause
The signal level fluctuates in synchronization with the rotation period T of the magneto-optical disk 12.

Thus, in this embodiment, the Fuo Kas error signal S _FE DC component S _DC (FIG. 6 (B)) and AC component S _AC
(FIG. 6 (C)) and by performing signal processing,
The power consumption is reduced with a simple configuration.

That is, the amplifying circuit 54 is composed of an operational amplifying circuit driven by a power supply voltage of ± 15 [V], amplifies the AC component _SAC at a predetermined amplification factor, and has a signal level of ± 12 V at the maximum. An output signal S _{OAC of} about [V] is output.

Step-up transformer 55, the primary and secondary windings 55A and the ratio of winding number N ₁ and N ₂ of 55B is selected to 1:15 thereby following formula As shown in, it has been made the signal level V ₂ of the output signal S _OAC to boost the signal level V ₂ of 15 fold.

The relationship between the primary and secondary currents I ₁ and I ₂ of the step-up transformer 55 is expressed by the following equation. Is held in a relationship.

Thus, in the case of the output signal S _OAC having the maximum signal level of ± 12 [V], the drive signal S _ACO having the maximum signal level of ± 180 [V] (FIG. 6 (D )).

Further, the step-up transformer 55 is configured to output the drive signal S _ACO to the piezoelectric element 23 of the piezoelectric actuator 24 via the coupling capacitor 56, whereby the rotation signal T of the magneto-optical disk 12 is changed with respect to the magneto-optical disk 12. The position of the objective lens 27 that fluctuates in synchronization is held at a predetermined position. Amplifier contrast 60 is made in the same configuration as the amplifier circuit 54, the DC component S of Fuo Kas error signal S _{FE
The DC} is amplified and output to the DC / DC converter circuit 61.

Thus, a predetermined DC voltage V _DC (FIG. 6 (E)) is obtained via the DC / DC converter circuit 61, and the DC voltage V _DC is supplied to the piezoelectric actuator 2 via the coil 63.
The fourth piezoelectric element 23 is output.

As a result, in the piezoelectric actuator 24, the drive signal S _ACO output from the step-up transformer 55 is superimposed on the DC voltage _VDC, and the piezoelectric actuator 24 is driven by the resulting drive voltage V _E (FIG. 6 (F)). It has been done.

The inductance L ₆₃ of the coil 63 is
Compared with the secondary side inductance L ₅₅ of FIG. 5, the following equation L ₆₃ ≫L ₅₅ is held, so that the impedance of the output side of the DC / DC converter circuit 61 with respect to the step-up transformer 55 is reduced. The height is set high to drive the piezoelectric actuator 24 efficiently.

Thus by boosting the alternating current component S _AC of Fuo Kas error signal S _FE in the step-up transformer 55, resulting drives the amplifier 54 at a low power supply voltage can be reduced by that amount power consumption.

Furthermore, in the amplifier circuit 54, the amplifier circuit can be configured with simple insulation by the reduced power supply voltage, and the configuration of the amplifier circuit 54 is simplified accordingly, and the overall configuration of the magneto-optical disk device 10 is reduced. It can be simplified.

In the above configuration, Fuo Kas error signal S _FE is
Low-pass filter circuit 51 and high-pass filter circuit 52
The DC component S _DC and the AC component S _AC are separated into an amplifier circuit 60, a DC / DC converter circuit 61 and an amplifier circuit 54, respectively.
The voltage is applied to the piezoelectric actuator 24 at a predetermined signal level via the step-up transformer 55.

As a result, in the piezoelectric actuator 24, the objective lens 27 is held at a predetermined position with respect to the magneto-optical disk 12, and the light beam (A) can be emitted in a state of a just-in-time focus.

According to the above configuration, by boosting the AC component S _AC of the focus error signal S _FE with the boost transformer 55, the amplifier circuit 54 can be driven with a low power supply voltage, and power consumption can be reduced accordingly. At the same time, the configuration of the amplifier circuit 54 can be simplified, and thus the magneto-optical disk device 10 with low power consumption and a simple configuration can be obtained.

In the above embodiment, the low-pass filter circuit is used.
Although the case where the focus error signal S _FE is separated into the DC component S _DC and the AC component S _AC by the high-pass filter circuit 51 and the high-pass filter circuit 52 has been described, the present invention is not limited to this, and the low-pass filter circuit 51 and the The high-pass filter circuit 52 may be omitted.

That is, since the DC component can be cut off in the step-up transformer 55, the high-pass filter circuit 52 can be omitted as long as the amplifier circuit 54 in the preceding stage is not saturated.

Further, in the DC / DC converter circuit 61, the response to the input signal may be slow, and in that case, the low-pass filter circuit 51 can be omitted within a practically sufficient range.

Further, in the above-described embodiment, the case where the DC component S _DC of the focus error signal S _FE is applied to the piezoelectric actuator 24 at a predetermined signal level has been described, but the present invention is not limited to this, and only the AC component is applied. You may make it.

That is, for example, if the contamination of dust and the like can be sufficiently prevented, the parallel displacement of the magneto-optical disc 12 with respect to the objective lens 27 can be effectively prevented. In this case, even if the piezoelectric actuator 24 is driven only by the AC component, the jumper is not driven. The state of the stomacus can be obtained.

Further, in the above-described embodiment, the present invention has been described for the case where the objective lens of the magneto-optical disc device is driven. However, the present invention is not limited to this and can be widely applied to the case where the piezoelectric element is driven.

H Advantageous Effects of the Invention As described above, according to the present invention, a booster for boosting a DC component of a drive signal, a booster for boosting an AC component of the drive signal, and an AC obtained by boosting the booster from the booster And an application unit for applying the component to the piezoelectric element by superimposing the component on the DC component obtained by boosting the voltage from the boosting unit. Can be reduced, and the configuration can be simplified. Thus, a driving circuit for a piezoelectric element with low power consumption can be realized with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing a magneto-optical disc device according to an embodiment of the present invention, FIG. 2 is a perspective view showing the configuration of a piezoelectric actuator, FIG. 3 is a sectional view showing the detailed configuration thereof, and FIG. 5 is a perspective view showing a magnetic head portion, FIG. 5 is a block diagram showing a driving circuit of the piezoelectric actuator, FIG. 6 is a signal waveform diagram for explaining the operation thereof, and FIG. 7 is a block diagram showing a conventional driving circuit. It is. 10 ... Magneto-optical disk device, 12 ... Magneto-optical disk, 24
... Piezoelectric actuator, 23 ... Bimorph, 27 ... Objective lens, 55 ... Step-up transformer.

Claims (1)

(57) [Claims] A boosting means for boosting a DC component of a predetermined drive signal; a boosting transformer for boosting an AC component of the drive signal; Piezoelectric means for applying the AC component obtained by boosting from the transformer to the DC component obtained by boosting the DC component from the boosting means and applying the DC component to the piezoelectric element. Element driving circuit.