JPH089488A - Driving device for ultrasonic piezoelectric transducer - Google Patents

Abstract

PURPOSE:To surely lock in (start) respective piezoelectric transducers having plural resonance frequencies different from each other by each of their basic resonance frequencies with s simple circuit. CONSTITUTION:In the driving device for the ultrasonic piezoelectric transducer, the output from a reference oscillator 50 is variably set so as to obtain various oscillation reference signals fref. corresponding to the basic resonance frequencies fr of various piezoelectric transducers 1a, 1b, 1c,... respectively. Thus, since the start is enabled by the oscillation reference signals fref. corresponding to the respective basic resonance frequencies fr for each of piezoelectric transducers 1a, 1b, 1c,..., various piezoelectric transducers 1a, 1b, 1c,... can be surely driven by the respective basic resonance frequencies fr.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic vibrator driving device for driving a Langevin type ultrasonic vibrator at a resonance point.

[0002]

2. Description of the Related Art Generally, it is desirable that an oscillator used in an ultrasonic scalpel for surgical operation or an ultrasonic processing apparatus be driven at or near its fundamental resonance frequency. With respect to such a technique, for example, a driving device using a PLL (phase locked loop) system is known in which the phases of a driving voltage and a current to the vibrator are compared and the driving frequency of the vibrator is controlled to match the resonance frequency. Known as the technology of. FIG. 9 shows a basic configuration of the PLL type driving device.

That is, this type of oscillator can be represented as an equivalent circuit as shown in FIG. 10A in the vicinity of its resonance point. In addition, this impedance is shown in FIG.

[0004]

[Equation 1] Shows the frequency characteristics of.

In the equivalent circuit as described above, FIG.
As shown in (a), the coil Ld for canceling the braking capacity Cd is connected in parallel or in series with the vibrator. At this time, since the characteristic of the vibrator is only the pure resistance component R at the resonance frequency, the frequency at which the phase difference between the voltage and the current becomes zero is the resonance frequency (resonance point) fr of the vibrator. FIG. 11B shows the impedance characteristic of the vibrator centered on this frequency fr. Therefore, by controlling the drive frequency so that the phase difference when the voltage phase θV and the current phase θI are compared by the PLL operation becomes zero,
The device comes to track the resonance point fr.

However, in the driving device having the above-mentioned structure, the oscillation frequency of the VCO (voltage controlled oscillator) is not always between the trackable frequencies f1 and f2 when the oscillation is started. Therefore, if the oscillation frequency at start-up is equal to or lower than the trackable frequency f1, the PLL operation becomes a positive feedback and is oscillated up to the minimum oscillation frequency of the VCO. Similarly, the oscillation frequency is the trackable frequency f2.
In the above cases, the maximum oscillation frequency is swung,
In such a state, tracking of the resonance point fr is no longer possible.

In addition, as shown in FIG.
In addition to the basic resonance point fr, the sub resonance point fr having a different vibration mode
a and frb are present. Each of these sub-resonance points fr, f
Even in rb, there is always a frequency at which the voltage-current phase difference becomes zero. Therefore, if the sub-resonance points fra and frb exist within the oscillating frequency range of the oscillation frequency of the VCO, the sub-resonance points fr and frb may be driven. In such a case, the conversion efficiency of the electro-mechanical vibration is remarkably deteriorated and it becomes unusable.

Therefore, for example, Japanese Patent Laid-Open No. 63-287214.
As disclosed in Japanese Patent Laid-Open Publication No. 2004-242242, there has been proposed a device which limits the oscillation frequency of the VCO by applying a limiter to the input voltage of the VCO. However, in this proposal, the setting of the limiter may be changed due to drift or the like, and in such a case, the oscillation frequency of the VCO may be out of the trackable frequency range f1 to f2.
Alternatively, there has been a problem that the frequency characteristic of the oscillator is fluctuated, and the range of the frequency at which the VCO can oscillate and the range of the trackable frequencies f1 to f2 are deviated.

Further, as disclosed in, for example, Japanese Patent Laid-Open No. 62-195925, it is possible to prevent driving at the sub-resonance points fra and frb existing in the oscillating frequency range of the VCO oscillation frequency. In the case where the range of the limiter is set to the above, when the oscillation frequency of the VCO is out of the range of the trackable frequencies f1 to f2 at the time of starting the oscillation, it becomes impossible to track the resonance point fr. I can't solve it.

Further, for example, US Pat. No. 4,754,1
In Japanese Patent Publication No. 86, the VCO is operated at a frequency f11 (see FIG. 11 (b)) which is lower than the trackable frequency f1.
A technique is disclosed in which a pulse is applied to the phase comparison inputs θV and θI to apparently increase the frequency of the feedback signal from the detection circuit to pull the oscillation frequency of the VCO within the range of trackable frequencies f1 to f2. ing. However, in this case as well, the oscillation frequency of the VCO must be limited, and it fluctuates due to drift or the like, and a new sub-resonance point is generated within the range of frequencies f11 to fr by the tip tip of the vibrator. If so, the device may be operated there.

[0011]

As described above, the conventional driving device has a drawback that it is difficult to reliably drive the vibrator at the fundamental resonance frequency. Therefore, it is an object of the present invention to provide an ultrasonic vibrator driving device capable of reliably driving vibrators having different resonance frequencies at a basic resonance frequency with a simple circuit configuration.

[0012]

In order to achieve the above object, in an ultrasonic vibrator driving device of the present invention, an ultrasonic vibrator driving oscillator for driving the ultrasonic vibrator, And a feedback means for feeding back a drive signal supplied from the oscillator for driving the ultrasonic transducer to the ultrasonic transducer, and controlling the oscillator for driving the ultrasonic transducer according to the feedback signal from the feedback means. Thus, in the driving device of the ultrasonic vibrator for driving the ultrasonic vibrator at its resonance point, a reference oscillator that oscillates a frequency signal that serves as a reference for driving the resonance point, and each has a different resonance frequency, A plurality of transducer means each having an indicating means for indicating the resonance frequency, and a switching means for switching between the signal from the reference oscillator and the signal from the feedback means. If, comprising a instruction means of said transducer means is coupled to said reference oscillator, said reference oscillator is configured to generate the resonant frequency of each transducer means.

[0013]

According to the present invention, with the above configuration, the reference oscillator oscillates the frequency signal serving as a reference for driving the resonance point,
The oscillator means have different resonance frequencies, and the switching means switches between the signal from the reference oscillator and the signal from the feedback means. In particular, the indicating means of the oscillator means is coupled to the reference oscillator. The reference oscillator generates the resonance frequency of each vibrator means.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a basic configuration of a drive device for an ultrasonic transducer according to the present invention. This drive is
A drive circuit 2 for generating a drive signal (drive frequency signal) for driving the ultrasonic oscillator 1 at a resonance point, an amplifier 3 for amplifying the drive signal from the drive circuit 2, and the oscillator 1 via the amplifier 3. A detection circuit (feedback means) 4 for detecting a feedback signal from the drive signal supplied to
A switch circuit 6 for selectively supplying a feedback signal from the detection circuit 4 or an oscillation reference signal (reference frequency signal) from a reference oscillator 5 to the drive circuit 2, and a control circuit 7 for controlling the switch circuit 6. Has been done.

The reference oscillator 5 is designed to oscillate at or near the fundamental resonance frequency fr of the vibrator 1, and generates an oscillation reference signal corresponding to the fundamental resonance frequency fr or a frequency near the fundamental resonance frequency fr. It is what is output.

The control circuit 7 supplies the oscillation reference signal from the reference oscillator 5 to the feedback signal input terminal of the drive circuit 2 at the time of oscillation start, and drives the feedback signal from the detection circuit 4 after the start. Circuit 2
The switch circuit 6 is controlled so as to be supplied to the feedback signal input terminal.

In such a configuration, when the vibrator 1 is activated, the switch circuit 6 is controlled to the A side by the control circuit 7 so that the oscillation reference signal from the reference oscillator 5 is first supplied to the drive circuit 2. To do. When the drive circuit 2 is operated after being set in this state, the vibrator 1 is driven at a frequency (drive signal) according to the oscillation reference signal from the reference oscillator 5. That is, the vibrator 1 is activated by the fundamental resonance frequency fr or a frequency close to it.

As a result, the detection circuit 4 detects an output (feedback signal) which is very close to the feedback signal obtained when the vibrator 1 is driven at the basic resonance point. Then, after maintaining the state where the above output is obtained by the detection circuit 4, that is, after activating the vibrator 1, the control circuit 7 controls the switch circuit 6 to the B side. Then, the drive circuit 2 is supplied with an output from the detection circuit 4, which is very close to the feedback signal obtained when the basic resonance point of the vibrator 1 is driven, and the drive circuit 2 moves the vibrator 1 to the resonance point. It is operated so as to be driven by fr. As a result, the vibrator 1 can be reliably driven at the basic resonance point fr.

FIG. 2 shows a first embodiment of the present invention. In FIG. 2, the vibrator 1 has the coil Ld selected and connected so as to have the characteristics shown in FIG. 11B. In this driving device, the voltage phase θV and the current phase θI in response to the vibration in the vibrator 1 are detected by the detection circuit (feedback means) 4, and the voltage phase θV from the detection circuit 4 and the switch circuit 6 are passed. A phase comparator 21 for comparing the current phase θI supplied from the detection circuit 4 and the phase difference between the two, a low-pass filter (LPF) 22 for generating a control voltage from the output from the phase comparator 21, This low pass filter 22
V for generating a drive signal having a frequency corresponding to the control voltage from
A PLL circuit 2a including a CO (voltage controlled oscillator) 23 is provided, and the resonance point tracking control of the vibrator 1 is performed by the PLL circuit 2a. That is, during driving, the control circuit 7 controls the switch circuit 6 so that the voltage phase θV and the current phase θI from the detection circuit 4 are supplied to the phase comparator 21.

On the other hand, at the time of starting the oscillation, instead of the current phase θI from the detection circuit 4, the oscillation reference signal fre oscillated from the reference oscillator 5 in the vicinity of the resonance frequency fr of the vibrator 1.
f. Is supplied to the phase comparator 21, the control circuit 7 controls the switch circuit 6. The control circuit 7 may control the switch circuit 6 temporally by a timer circuit, for example.
Alternatively, the oscillation reference signal fref. And the voltage phase θV from the detection circuit 4 are compared, and the PLL circuit 2a determines that the oscillation reference signal fref. Alternatively, the switching control may be performed when it is detected that the lock state is completely locked.

Next, the operation of the above configuration will be described. Now, when the above device is started up, the oscillation reference signal fref. The switch circuit 6 is controlled by the control circuit 7 so as to be supplied. Then, the voltage phase θV from the detection circuit 4 and the oscillation reference signal fref. The PLL circuit 2a causes the oscillation reference signal fref. It will be locked.

Here, the oscillation reference signal fref. Is oscillated in the vicinity of the basic resonance frequency fr of the vibrator 1, the frequency of the drive signal output from the amplifier 3 is a value in the vicinity of the basic resonance frequency fr of the vibrator 1.
Therefore, the oscillator 1 is driven at a frequency within the range of f1 to f2 that can be tracked with respect to the fundamental resonance frequency fr. At this time, the signal of the current phase θI obtained from the detection circuit 4 becomes zero or has a very small phase difference with respect to the signal of the voltage phase θV. In this state, when the switch circuit 6 is switched by the control circuit 7, the PLL circuit 2a works so that the phase difference when the voltage phase θV and the current phase θI are compared is always zero. In other words, the PLL circuit 2a enters into the resonance point driving operation that also tracks the resonance point fluctuation due to the load fluctuation of the vibrator 1. Therefore, in the driving device for the vibrator 1 using the PLL method, the vibrator 1 can be reliably locked at the basic resonance frequency fr.

FIG. 3 shows a second embodiment of the present invention. In the second embodiment, various oscillation reference signals fref. According to the basic resonance frequency fr of the various vibrators 1a, 1b, 1c ,. So that the output from the reference oscillator 50 can be varied. In this case, for each of the transducers 1a, 1b, 1c, ..., Oscillation reference signal fref. Since the start-up can be performed by a plurality of different types of vibrators 1a, 1b, 1c, ...
Can be driven reliably.

Further, the oscillator 1 is intentionally activated at the frequency of another mode resonance, and at this time, the oscillation reference signal fref. The reference oscillator 50 can also be configured so that

FIG. 4 shows another embodiment of the present invention. In the case of this driving device, a detector 11 is attached to the vibrator 10 so as to obtain a vibration feedback signal in response to mechanical vibration. And this detector 1
1 or the oscillation reference signal from the reference oscillator 5 that oscillates in the vicinity of the resonance frequency fr of the oscillator 10 is supplied to the feedback oscillator 30 via the switch circuit 6 controlled by the control circuit 7. Is configured.

That is, the feedback oscillator 30 is the detector 11
The oscillator 10 is driven by a drive signal supplied from the feedback oscillator 30 via the amplifier 3 by being oscillated at a frequency according to the feedback signal from the feedback oscillator or the oscillation reference signal from the reference oscillator 5. It is like this.

Here, the vibration feedback signal is
When the vibrator 10 is driven at the resonance point fr, the signal has a maximum amplitude, and has the same frequency as the resonance frequency fr. Therefore, when this signal is supplied to the feedback oscillator 30, the feedback oscillator 30 operates so as to always drive the vibrator 10 at the resonance frequency fr.

In the driving device having such a configuration, the control circuit 7 controls the switch circuit 6 so that the oscillation reference signal from the reference oscillator 5 is supplied to the feedback oscillator 30 when the oscillation is started. In this case, since the oscillation reference signal is oscillated near the basic resonance frequency fr of the vibrator 10, the vibrator 10 is driven at a frequency very close to the basic resonance frequency fr.

In this state, the control circuit 7 switches the switch circuit 6 so that the vibration feedback signal from the detector 11 is supplied to the feedback oscillator 30. Then, the feedback oscillator 30 works to drive the vibrator 10 at the resonance point fr by the vibration feedback signal from the detector 11. Therefore, the feedback oscillator 3
In the driving device using 0, the vibrator 10 can be driven reliably at the basic resonance frequency fr.

5 to 8 show an example of the configuration of the switch circuit 6 used in the above embodiment. The switch circuit 60 shown in FIG. 5 is a three-state buffer 60.
The control signal is composed of a and 60b and an inverter 60c. For example, the high level "H" of the control signal connects the A side, and the low level "L" connects the B side to the output side.

The switch circuit 61 shown in FIG. 6 is a combination of AND gates 61a and 61b, an OR gate 61c, and an inverter 61d. For example, the high side "H" of the control signal is on the A side, and the low level "L" is on the B side. Each side is connected to the output side.

The switch circuit 62 shown in FIG. 7 is constructed by using analog switches 62a and 62b and an inverter 62c. For example, when the control signal is at a high level "H", the A side is at a low level "L". The B side is connected to the output side, respectively.

The switch circuit 63 shown in FIG. 8 uses a mechanical relay. As described above, at the time of starting oscillation, the oscillator is driven by the drive signal according to the output from the oscillator oscillating at or near the fundamental resonance frequency of the oscillator, and the detector sets the oscillator to the basic resonance frequency. In this state, a feedback signal similar to the one obtained when the oscillator is driven is obtained, and by switching the output of the oscillator to the feedback signal from the detection circuit, the oscillator can be reliably driven at the basic resonance point. ing. That is, by simply adding an oscillator that oscillates at or near the basic resonance frequency of the oscillator and a switch circuit that switches the output of this oscillator and the feedback signal, the oscillator can be reliably driven at its resonance point. ,
The drive device can be operated.

In the above embodiment, the reference oscillator oscillates at or near the fundamental resonance frequency of the oscillator, but the invention is not limited to this, and the drive signal may be generated in the range of the trackable frequency. It suffices as long as it oscillates at a frequency at which a feedback signal capable of obtaining Of course, various modifications can be made without departing from the spirit of the invention.

[0035]

As described above in detail, according to the present invention, a simple circuit configuration surely locks in (starts) a vibrator having a plurality of different resonance frequencies at each basic resonance frequency. It is possible to provide a drive device for an ultrasonic transducer capable of performing the above.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of a drive device for an ultrasonic transducer according to an embodiment of the present invention.

FIG. 2 is a block diagram of a drive device showing a first embodiment of the present invention.

FIG. 3 is a block diagram of a drive device showing a second embodiment of the present invention.

FIG. 4 is a block diagram of a driving device showing another embodiment of the present invention.

FIG. 5 is a diagram showing a configuration example of a switch circuit used in the driving device.

FIG. 6 is a diagram showing a configuration example of a switch circuit used in the driving device.

FIG. 7 is a diagram showing a configuration example of a switch circuit used in the driving device.

FIG. 8 is a diagram illustrating a configuration example of a switch circuit used in the drive device.

FIG. 9 is a diagram for explaining a conventional technique and its problems.

FIG. 10 is a diagram for explaining a conventional technique and its problems.

FIG. 11 is a diagram for explaining a conventional technique and its problems.

FIG. 12 is a diagram for explaining a conventional technique and its problems.

[Explanation of symbols]

1 ... Ultrasonic transducer, 2 ... Drive circuit, 2a ... PLL circuit,
4 ... Detection circuit (feedback means), 5 ... Reference oscillator, 6 ... Switch circuit, 7 ... Control circuit.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H03L 7/06

Claims (1)

[Claims] 1. An ultrasonic transducer driving oscillator for driving an ultrasonic transducer, and feedback means for feeding back a driving signal supplied from the ultrasonic transducer driving oscillator to the ultrasonic transducer. An ultrasonic oscillator driving device that drives the ultrasonic oscillator at its resonance point by controlling the ultrasonic oscillator driving oscillator according to a feedback signal from the feedback means, A reference oscillator that oscillates a frequency signal that serves as a reference, a plurality of oscillator means that each have a different resonance frequency, and each have an indicating means that indicates the resonance frequency; a signal from the reference oscillator and the feedback; Switching means for switching between the signal from the means and the indicating means of the oscillator means is coupled to the reference oscillator, each of the reference oscillators A driving device for an ultrasonic vibrator, which is characterized in that a resonance frequency of the vibrator means is generated.