JP2002263579A - Ultrasonic transducer drive unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic transducer drive unit capable of increasing percent modulation with a simple structure. SOLUTION: A control system is set to that an ultrasonic transducer 3 is driven in its resonance frequency by a driving signal from a driving signal generation means 5 and that the driving signal generation means 5 follows the resonance frequency by feedback signals from a detection circuit 7. Additionally, signals for modulation are sent from a modulating signal generation means 11 to modulate the frequency of the driving signal. As a result, large modulation can be performed by a small signal for modulation by using a frequency characteristic that load impedance changes significantly in the vicinity of the resonance frequency of the ultrasonic transducer 3.

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 apparatus for driving an ultrasonic vibrator used in, for example, an ultrasonic surgical apparatus for surgical operation, an ultrasonic calculus crushing apparatus, and the like.

[0002]

2. Description of the Related Art An ultrasonic surgical apparatus for emulsifying, coagulating, or incising a living body by ultrasonic vibration or crushing a calculus has been conventionally known. In such an ultrasonic surgical apparatus, resonance frequency tracking control and constant current control are often performed to control the emulsification, coagulation, incision, and crushing capabilities at a constant level as disclosed in Japanese Patent Application Laid-Open No. 7-3036535.

On the other hand, there is known a method of modulating an output for vibrating an ultrasonic vibrator in order to enhance tissue selectivity and crushing ability. Simply turn on / off the output to the ultrasonic transducer
ff, modulation can be realized. However, in this method, a feedback signal cannot be obtained, so that resonance frequency tracking control cannot be performed. In addition, as shown in Japanese Utility Model Publication No. 50-6711, when a drive signal is amplitude-modulated, a constant value is required. Due to the responsiveness of the current control system, a sufficient modulation rate may not be obtained.

In Japanese Patent Publication No. Hei 7-106208, a resonance frequency tracking system for high output and low output is prepared, and modulation is realized by switching the two systems. However, this configuration requires an extra resonance frequency tracking system. They have to be prepared and are somewhat expensive.

(Object of the Invention) The present invention has been made to solve the above-mentioned problems, and has as its object to provide an ultrasonic transducer driving device which can increase the modulation factor with a simple structure. And

[0006]

According to the present invention, there is provided a drive signal generating means for generating a drive signal for driving an ultrasonic transducer, and phase information for detecting phase information of the drive signal output from the drive signal generating means. Detection means, and drive signal control means for controlling the drive signal generation means based on the phase information detected by the phase information detection means to output the drive signal adapted to the resonance frequency of the ultrasonic transducer. And a driving signal modulating means for modulating the frequency of the driving signal output by the driving signal generating means, thereby greatly changing the output level of the driving signal by modulating the frequency of the driving signal by the driving signal modulating means. I can do it.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIGS. 1 to 4 relate to a first embodiment of the present invention, FIG. 1 shows a basic configuration of an ultrasonic transducer driving device of the present invention, and FIG. 3 shows a specific configuration of the ultrasonic transducer driving device according to the embodiment, FIG. 3 shows phase and impedance characteristics when the ultrasonic transducer driving device and the ultrasonic transducer are combined, and FIG. The output waveform characteristics when point tracking is performed and the output waveform characteristics when modulation is performed are shown.

An ultrasonic surgical apparatus 1 shown in FIG. 1 includes an ultrasonic vibrator driving device 2 of the present invention and an ultrasonic vibrator 3 connected to the ultrasonic vibrator driving device 2 to which a driving signal is applied. And a built-in ultrasonic surgical instrument 4.

The ultrasonic vibrator driving device 2 includes an ultrasonic vibrator 3
Drive signal generating means 5 for generating a drive signal for driving the drive signal near its resonance frequency;
An amplifier 6 for amplifying the drive signal from the amplifier, a detection circuit 7 for detecting a signal containing the phase information from the drive signal supplied to the ultrasonic transducer 3 via the amplifier 6, and an output from the detection circuit 7. A switch circuit 9 for selectively supplying a feedback signal to be generated and an oscillation reference signal generated from the reference oscillator 8 to the drive signal generation means 5; and a frequency of the drive signal of the drive signal generation means 5 (more broadly, a frequency And a control circuit 12 for controlling the switch circuit 9 and the modulation signal generating means 11.

The control circuit 12 first sends a switching signal for turning on the contact A of the switch circuit 9, and outputs an oscillation reference signal having a frequency corresponding to the resonance frequency fr of the ultrasonic transducer 3 generated by the reference oscillator 8 as a drive signal. Is applied to the ultrasonic vibrator 3, and a signal having the phase information detected (extracted) by the detection circuit 7 from the drive signal at that time is used as a feedback signal to control the phase of the drive signal. After setting to the state locked to the signal, switching is performed so that the contact B of the switch circuit 9 is turned on.

Thereafter, the control circuit 12 controls the modulation signal generation means 11 with the control signal, and outputs a modulation signal from the modulation signal generation means 11 to the drive signal generation means 5, modulates the amplitude of the drive signal, and It is applied to the sound wave oscillator 3.

FIG. 2A shows a more specific configuration of FIG. In the ultrasonic vibrator driving device 2A constituting the ultrasonic surgical device 1 shown in FIG. 2A, the detection circuit 7 connected to the ultrasonic vibrator 3 of the ultrasonic surgical instrument 4 includes the ultrasonic vibrator 3
A voltage phase .theta.v and a current phase .theta.i corresponding to the vibration of the sensor are detected, and the voltage phase .theta.v from the detection circuit 7 is used as a phase lock loop circuit (hereinafter abbreviated as PLL circuit) corresponding to the drive signal generating means 5 in FIG. ) Is input to the phase comparator 21 constituting 5A.

The current phase θi from the detection circuit 7 and the oscillation reference signal of the reference oscillator 8 are input to the phase comparator 21 via the contacts B and A of the switch circuit 9, respectively. The phase comparator 21 compares the phase of the voltage phase θv from the detection circuit 7 with the oscillation reference signal of the reference oscillator 8 input via the switch circuit 8 or the current phase θi from the detection circuit 7, and compares the phase difference. Outputs an output signal according to.

An output signal of the phase comparator 21 is a low-pass filter (hereinafter abbreviated as LPF) 22 that passes low frequency components.
, And is input to a voltage-controlled oscillator (hereinafter abbreviated as VCO) 23 whose oscillation frequency changes according to the control voltage.

The VCO 23 oscillates at a frequency corresponding to the input control voltage. The oscillated signal is input to the amplifier 6 as a drive signal, amplified, applied to the ultrasonic vibrator 3, and detected by the detection circuit. 7, the voltage phase θv
And the current phase θi are detected.

The switching of the contacts A and B of the switch circuit 9 is controlled by a control circuit 12. In FIG. 2A, an oscillation circuit 11a is employed as the modulation signal generating means 11 of FIG.
The oscillation is controlled by the control signal from the CPU. The oscillation signal output from the oscillation circuit 11a is input to the LPF 22 together with the output signal of the phase comparator 21 as a modulation signal.

The frequency of the oscillation signal (modulation signal) generated by the oscillation circuit 11a is determined by adjusting the ultrasonic vibrator 3 to its resonance frequency f.
The frequency is sufficiently lower than the frequency driven by r, and is, for example, on the order of several hundreds. Phase comparator 2
1, the LPF 22 and the VCO 23 constitute a PLL circuit 5A.

In FIG. 2A, the output signal of the oscillation circuit 11a is input to the LPF 22, but it may be input directly to the VCO 23 without passing through the LPF 22, as shown in FIG. 2B. In this case, the attenuation of the modulation signal by the LPF 22 can be eliminated.

In this embodiment, the ultrasonic vibrator 3
When combined with the ultrasonic driving device 2, the phase θ and the absolute value | Z | of the impedance with respect to the frequency f of the driving signal have characteristics as shown in FIG. 3, and are selected so as to be driven near the resonance frequency fr. Is set.

A feedback control loop is formed by the PLL circuit 5A so as to track the resonance point (resonance frequency fr) of the ultrasonic transducer 3. The output waveform at this time is as shown in FIG. That is, by driving in a state locked to the resonance frequency fr, the amplitude and the phase of the drive signal become constant.

Further, in the state where the resonance point is tracked as shown in FIG. 4A, a modulation signal whose frequency is sufficiently lower than the resonance frequency fr and whose amplitude is minute is transmitted from the oscillation circuit 11a to the phase comparator 21 by the oscillation circuit 11a. The drive signal can be frequency-modulated by inputting it to the VCO 23 in addition to the output. The output waveform at this time is as shown in FIG.

That is, since the input signal level for determining the oscillation frequency applied to the VCO 23 fluctuates due to the modulation signal from the oscillation circuit 11a in addition to the signal component fed back, the oscillation frequency of the VCO 23 becomes close to the resonance frequency fr. And its amplitude also fluctuates.

In this case, as shown in FIG.
r, the impedance of the ultrasonic transducer 3 becomes a minimum value,
In the vicinity thereof, the impedance of the ultrasonic transducer 3 shows a frequency characteristic in which the impedance changes abruptly. Therefore, a low frequency and a slight change in the amplitude of the modulation signal change the impedance with respect to the frequency. Can be greatly varied. That is, the drive signal can be largely modulated by the small modulation signal.

The ultrasonic vibrator 3 used in the ultrasonic surgical instrument 4 is a Langevin type vibrator used at a resonance frequency of a piezoelectric element plate such as a thin quartz plate sandwiched between metal disks. Have been.

As described above, in the present embodiment, during driving for performing an ultrasonic operation, the control circuit 12 controls the switch circuit 9 so that the voltage phase θv and the current phase θi from the detection circuit 7 are obtained. Is supplied to the phase comparator 21 and further modulates the drive signal.
Controls the oscillation circuit 11a so that the modulation signal is added to the output of the phase comparator 21 and input to the VCO 23 through the LPF 22.

Next, the operation of the above configuration will be described. When the device 2A is operated, the control circuit 12 controls the contact A of the switch circuit 9 to be turned on so that the oscillation reference signal fref from the reference oscillator 8 is supplied to the PLL circuit 5A. In this case, the frequency of the oscillation reference signal fref from the reference oscillator 8 is set so as to match the resonance frequency fr of the ultrasonic transducer 3 actually connected.

Then, after the voltage phase θv and the oscillation reference signal fref are in a phase-locked operation in that state, the control circuit 12 switches the switch circuit 9 and the contact B
Is turned on, and the voltage phase θv of the drive signal itself is
And the current phase θi is shifted to the phase lock operation. In this state, the ultrasonic transducer 3 is driven in a state where the amplitude and the frequency are constant as shown in FIG.

Thereafter, the control circuit 12 causes the oscillation circuit 11a to oscillate the modulation signal, synthesizes it with the output of the phase comparator 21, and inputs the synthesized signal to the VCO 23. By adding this modulation signal, the drive signal for driving the ultrasonic transducer 3 fluctuates near the resonance frequency fr. Since the conversion efficiency with respect to the frequency f fluctuates greatly near the resonance frequency fr, the ultrasonic vibrator 3 vibrates with its amplitude and frequency modulated as shown in FIG.

The frequency and amplitude of the modulation signal may be sufficiently small with respect to the resonance frequency fr, and may be large enough that the resonance frequency tracking control is not deviated. Generally, a frequency of 20 kHz to 60 kHz is used as the resonance frequency fr,
For example, when the resonance frequency fr is 23.5 kHz, the function of modulating the frequency of the modulation signal by about 100 Hz and the amplitude of the drive signal by the order of 1/100 can be increased.

Therefore, by changing the output level and frequency of the modulation signal, it is possible to easily set the incision and coagulation ability by the ultrasonic surgical instrument 4 to a level necessary for the treatment.

As described above, according to the present embodiment, it is possible to generate a drive signal capable of greatly changing the output of the ultrasonic transducer 3 with a simple configuration without substantially changing the response of the resonance frequency tracking control system. . Therefore, cost reduction and the like can be achieved.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. Note that parts common to the first embodiment are omitted, and only different parts will be described. In the first embodiment shown in FIG. 2A or FIG. 2B, the modulation signal of the oscillation circuit 11a is applied to the VCO 23, but in this embodiment, the detection circuit 7 is applied as described below. The phase of the output signal is changed.

The ultrasonic transducer driving device 2B shown in FIG.
In the ultrasonic transducer driving device 2A in FIG. 2A, the voltage phase θv of the detection circuit 7
And the current phase θi
Are input to the switch circuit 9 via the phase shift circuit 24b.

The phase shift circuits 24a, 24a
b is constituted by employing, for example, an electronic volume, and its resistance value is electrically changed by an applied voltage, so that the phase amount of the voltage phase θv or the current phase θi can be varied.

The phase shift amount of each electronic volume is controlled by, for example, an oscillation signal from an oscillation circuit 11b as phase shift control means. The oscillation operation of the oscillation circuit 11b is controlled by the control circuit 12. Other configurations are the same as those in FIG.

In FIG. 5, the detection circuit 7 and the phase comparator 2
Although two phase shift circuits 24a and 24b are provided between them, one of them may be provided alone. When two are provided as shown in FIG. 5, for example, the phase shift circuits 24a and 24b
Are shifted in opposite directions, the function of phase modulation (frequency modulation) can be increased.

The oscillating circuit 11b outputs an oscillating signal at the same frequency as the oscillating circuit 11a in the first embodiment, but its amplitude is shifted by a phase shift with respect to the voltage of the oscillating signal of the phase shift circuits 24a and 24b. Set according to the quantity.

Also in this case, if the phase shift amount is shifted to the order of several hundredths of the phase amount 2π of the period of the resonance frequency, the output of the drive signal can be greatly changed. it can.

In the case of the first embodiment, it is necessary to increase the frequency or amplitude of the modulation signal from outside the resonance frequency tracking control system in order to greatly increase the modulation rate. In such a case, the resonance frequency tracking control is likely to be dislocated because the amplitude is greatly fluctuated by being applied from the outside together with the change in the frequency (phase) of the signal to be fed back, and the resonance frequency tracking control system is in a stable operating state. , There is a limit to a large increase in the modulation rate.

In this embodiment, since only the phase of the signal input to the resonance frequency tracking control system is changed, the amplitude of the resonance frequency tracking control system changes with the change in the phase (frequency). Since the change is caused by a phase (frequency) change and is not directly changed from the outside, it is possible to maintain the operation of the resonance frequency tracking control system more stable than in the case of the first embodiment. Become.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 6, the ultrasonic transducer driving device 2 according to the third embodiment
In C, the voltage phase θv and the current phase θi detected by the detection circuit 7 are input to the phase difference detection circuit 31 constituting the digital PLL circuit 5B. Then, a phase difference between the two is obtained, and a digital output corresponding to the phase difference is output to the register 33 via the switch circuit 32.

The register 33 holds the input value, and the held value is output from the output terminal to the digital oscillator 34. The digital oscillator oscillates at a frequency corresponding to the digital value from the register 33 to generate a drive signal. This drive signal is amplified by the amplifier 6 and applied to the ultrasonic transducer 3. The phase difference detection circuit 31, the switch circuit 32, the register 33, and the digital oscillator 34 constitute a digital PLL circuit 5B.

The switch circuit 32 is turned on and off by the control circuit 12. The control circuit 12 turns off the switch circuit 32 in the initial state, controls the data transmission circuit 35, and causes the data transmission circuit 35 to transmit initial frequency setting data to the register 33. The initial frequency setting data is a value that causes the oscillation frequency of the digital oscillator 34 to match the resonance frequency fr of the ultrasonic transducer 3.

Accordingly, the digital oscillator 34 oscillates according to the data, and the oscillation frequency thereof matches the resonance frequency fr of the ultrasonic transducer 3. Thereafter, the control circuit 12 turns on the switch circuit 32, sets the PLL control state, and sets the state to perform the resonance point tracking.

After the control circuit 12 sets the PLL control state, the control circuit 12 turns on the second switch circuit 36 and inputs a modulation signal to be digitally UP / DOWN from the modulation circuit 37 to the register 33, The oscillation frequency of the oscillator 34 is changed.

Next, the operation of the present embodiment will be described. At the start of oscillation, the control circuit 12 controls the data transmission circuit 35 to transmit initial data from the data transmission circuit 35 to the register 3.
3 and the switch circuits 32 and 36
Are turned off, the digital oscillator 34 is oscillated (step S1 in FIG. 7).

In this case, the initial data is data for causing the ultrasonic transducer 3 to oscillate at its resonance frequency fr, so that the digital oscillator 34 oscillates at the oscillation frequency fr.

Thereafter, the control circuit 12 switches the switch circuit 32
Is turned on to shift to the PLL control state (step S
2). Next, the control circuit 12 turns on the switch circuit 36 to input the UP / DOWN signal output from the modulation circuit 37 to the register 33, and the frequency data which determines the oscillation frequency by the modulation signal periodically UP / DOWN. Is varied.

As a result, the output frequency of the digital oscillator 34 fluctuates near the resonance frequency fr of the ultrasonic transducer 3, and
The vibration of the ultrasonic transducer 3 is amplitude-modulated (step S3).

This embodiment has the same effects as the second embodiment. The present embodiment can also be used for crushing calculi by ultrasonic waves.

[Supplementary Notes] 2. The ultrasonic vibrator driving device according to claim 1, wherein the ultrasonic vibrator is a Langevin type piezoelectric vibrator. 2. 2. The ultrasonic transducer driving device according to claim 1, wherein said drive signal control means and said drive signal modulation means are constituted by digital circuits.

3. The ultrasonic vibrator is driven by a drive signal having a frequency substantially matching the resonance frequency of the ultrasonic vibrator generated by the drive signal generating means, and phase information when the ultrasonic vibrator is driven is detected by the phase information detecting means. In the ultrasonic transducer driving device having a resonance frequency tracking control system by detecting and controlling the drive signal generating means with a feedback signal based on the phase information, the drive signal in the resonance frequency tracking control system is frequency-converted. An ultrasonic vibrator driving device comprising a frequency modulating means for modulating or a phase changing means for changing a phase of the feedback signal. 4. 4. The ultrasonic transducer driving device according to claim 3, wherein the resonance frequency tracking control system is configured by an analog or digital type PLL circuit.

5. A drive signal having a frequency almost equal to the resonance frequency of the ultrasonic transducer generated by the drive signal generation means,
Moreover, the ultrasonic transducer having the characteristic that the impedance of the ultrasonic transducer changes sharply at a frequency near the resonance frequency is driven, and the phase information when the ultrasonic transducer is driven is detected by the phase information detecting means. In the ultrasonic transducer driving device having a resonance frequency tracking control system by controlling the drive signal generation means with a feedback signal based on the phase information, the drive signal in the resonance frequency tracking control system is frequency-modulated. An ultrasonic transducer driving device provided with frequency modulation means for changing the phase of the feedback signal.

[0054]

As described above, according to the present invention,
By utilizing the fact that the impedance of the ultrasonic vibrator greatly changes near the resonance frequency, the frequency of the drive signal is modulated near the resonance frequency, and the drive current value of the ultrasonic vibrator is changed. With such a configuration, it is possible to realize a large change in output level such as amplitude modulation. Further, cost reduction can be achieved.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing a specific configuration of the ultrasonic transducer driving device according to the first embodiment of the present invention.

FIG. 3 is a diagram showing frequency characteristics of phase and impedance in a case where an ultrasonic transducer driving device and an ultrasonic transducer are combined.

FIG. 4 is a characteristic diagram of an output waveform when resonance point tracking is performed and an output waveform when modulation is performed.

FIG. 5 is a block diagram showing a configuration of an ultrasonic transducer driving device according to a second embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of an ultrasonic transducer driving device according to a third embodiment of the present invention.

FIG. 7 is a flowchart for explaining the operation.

[Description of Signs] 1 ... Ultrasonic surgical apparatus 2 ... Ultrasonic transducer driving apparatus 3 ... Ultrasonic transducer 4 ... Ultrasonic surgical instrument 5 ... Drive signal generating means 5A ... PLL circuit 6 ... Amplifier 7 ... Detection circuit 8 ... Reference oscillator 9 Switch circuit 11 Modulation signal generating means 11a Oscillator circuit 12 Control circuit 21 Phase comparator 22 Low-pass filter (LPF) 23 Voltage-controlled oscillator (VCO)

Claims (3)

[Claims] A drive signal generator for generating a drive signal for driving an ultrasonic transducer; a phase information detector for detecting phase information of the drive signal output by the drive signal generator; Based on the phase information detected by the means,
Drive signal control means for controlling the drive signal generation means to output the drive signal suitable for the resonance frequency of the ultrasonic transducer; and a drive signal for modulating the frequency of the drive signal output from the drive signal generation means. An ultrasonic vibrator driving device, comprising: a modulation unit. 2. The ultrasonic transducer drive device according to claim 1, wherein said drive signal control means is a PLL circuit comprising a voltage controlled oscillator. 3. The apparatus according to claim 1, wherein said drive signal modulation means is a feedback signal phase shift means.
The ultrasonic transducer driving device as described in the above.