JPH04325149A - Ultrasonic vibrator transducer driving circuit - Google Patents

Abstract

PURPOSE:To provide the ultrasonic vibrator transducer driving circuit which can highly efficiently drive an ultrasonic vibrator transducer with a high voltage and large current and is small in size, low in cost and simple in constitution. CONSTITUTION:Two switching circuit driving signals which are complemental with each other are formed by one source driving signal by a driving signal forming circuit 3 of the simple constitution consisting of an inversion circuit and a differentiating circuit. Switching circuits 4 and 5 are driven by such switching circuit driving signals, by which the ultrasonic vibrator transducer 1 is driven with the high voltage and the large current.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic transducer drive circuit in an ultrasonic generator.

0002

[Prior Art] Conventionally, ultrasonic treatment devices such as an ultrasonic dissolution promoting device for in-vivo coagulation such as gallstones and blood clots, an ultrasonic suction device, a shock wave lithotripter, and a shock wave cancer treatment device,
A compact and highly efficient switching drive system has often been used in an ultrasonic transducer drive circuit in an ultrasonic generator having an ultrasonic transducer drive circuit for an ultrasonic or shock wave generator. For example, U.S. Patent No. 473,619
As disclosed in No. 2, the frequency of a resonant circuit formed by an inductance connected in series with a piezoelectric element and a capacitance of the piezoelectric element is made to match the resonant frequency of the piezoelectric element, thereby achieving a small size and high efficiency. There is an ultrasonic transducer drive circuit that uses a switching drive method.

However, the switching drive method has problems in that due to variations in the parameters of the piezoelectric element, it is difficult to tune to the resonant frequency using a single inductance, and high frequency components are likely to occur.

[0004] Therefore, in order to solve the above-mentioned problems, the present applicant has overcome the difficulty of tuning to the resonant frequency with a single inductance due to variations in the parameters of the piezoelectric element, and at the same time In order to suppress this occurrence, a parallel circuit of an inductance and a capacitor is connected to the power supply terminal of the switching means to form a series circuit with the inductance, as shown in Japanese Patent Application No. 1-74429. On the other hand, we have proposed an ultrasonic transducer drive circuit in which ultrasonic transducers are connected in parallel.

Furthermore, in the above-mentioned ultrasonic treatment apparatus, water as an acoustic transmission medium, a living body, etc. are applied as a load to the ultrasonic transducer in the ultrasonic generator, so the ultrasonic transducer is operated at a large amplitude. Since driving at a higher voltage is necessary for driving, the applicant has proposed the above-mentioned patent application No.
-74429 and Japanese Patent Application No. 2-48255, the two switching means are alternately turned on and off.
We proposed an ultrasonic transducer drive circuit that uses a push-pull switching method to turn on/off the ultrasonic transducer to drive it with high efficiency at a very high voltage to obtain large-amplitude ultrasonic radiation or ultrasonic vibration. There is.

Now, in order to employ the push-pull switching type ultrasonic transducer drive circuit, two complementary rectangular wave signals are required as drive signals for the switching drive. By the way, as a means to generate two complementary rectangular wave signals from a single drive signal,
For example, circuits using flip-flops and the like are known.

However, since the drive signal generation circuit using the flip-flops etc. has a complicated circuit configuration, it is possible to create a drive signal generation circuit with a smaller, cheaper and simpler circuit configuration without using the flip-flops etc. It is hoped that the formation of

However, the drive signal generation circuit is formed of a circuit that simply outputs a single source drive signal as it is and a signal that is an inversion of the source drive signal as the push-pull switching signal. However, even when the source drive signal is not input, there is a risk that the switching means will be turned on, and there is a problem in that it is difficult to obtain normal switching drive.

[0009]

As described above, in conventional or related ultrasonic transducer drive circuits, it is difficult to tune to the resonant frequency using a single inductance due to variations in the parameters of the piezoelectric element. The problem is that high frequency components are likely to be generated, or the ultrasonic transducer is driven with high efficiency at a very high voltage to obtain large amplitude ultrasonic radiation or ultrasonic vibration.
In addition, in order to operate the ultrasonic transducer reliably, the circuit configuration becomes complicated or large, resulting in an increase in cost.

The present invention has been made in view of the above problems, and it is possible to drive an ultrasonic transducer with high voltage and large current with high efficiency, and provides an ultrasonic transducer that is small, inexpensive, and has a simple configuration. The purpose is to provide a vibrator drive circuit.

[0011]

[Means for Solving the Problems] In order to achieve the above object, an ultrasonic transducer drive circuit according to the present invention includes an ultrasonic transducer having two electrode surfaces, and a phase difference between each of the two electrode surfaces. an isolation transformer device for supplying an inverted alternating current signal; push-pull switching means for supplying an alternating current square wave signal as a primary input signal of the isolation transformer device; a differentiation circuit that generates a first drive signal according to the signal and differentiates the source drive signal, and an inversion circuit that inverts the differential signal obtained by the differentiation circuit at a predetermined threshold;
The device further includes a drive signal generation circuit that generates a second drive signal complementary to the first drive signal whose phase is delayed with respect to the first drive signal, and outputs the generated second drive signal to the push-pull switching means.

0012

[Operation] In the present invention, in the drive signal generation circuit, 1
generating two mutually complementary switching means drive signals based on the two source drive signals, whereby the two switching means perform complementary switching operations, respectively;
This switching operation drives the ultrasonic transducer.

[0013]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 to 3 relate to one embodiment of the present invention, FIG. 1 is a circuit diagram schematically showing an ultrasonic transducer drive circuit in the embodiment of the present invention, and FIG. FIG. 3 is a circuit diagram showing details of the ultrasonic transducer drive circuit in the embodiment of the present invention.
FIG. 3 is an explanatory diagram showing a process in which two switching circuit drive signals are generated.

In FIG. 1, the drive signal generation circuit 3 receives one pulsed source drive signal (such as the one shown in FIG. 3(a)) from the input terminal 10, and generates a signal from this one pulsed source drive signal. This is a circuit that generates and then outputs mutually complementary pulsed signals (signals as shown in FIGS. 3(c) and (d)), and the circuit 2 that outputs the mutually complementary pulsed signals.
The switching circuit 4 has two output terminals, and this output terminal has two output terminals.
and the gate of the switching circuit 5, respectively.

The switching circuit 4 and the switching circuit 5 are switching circuits that perform switching operations based on the pulsed output signal of the drive signal generating circuit 3, and are composed of elements such as power MOS-FETs. In the switching circuit 4 and the switching circuit 5, the two output terminals of the drive signal generation circuit 3 are connected to the respective gates separately as described above, and the respective drains are connected to both ends of the isolation/step-up transformer 6. It is connected. Further, both sources are grounded. Note that a resistor R is connected between the gate and the source.

The insulating step-up transformer 6 has a center tap on its primary side, and the positive side of a DC power supply 7 is connected to this center tap, and is grounded via the DC power supply 7. The drains of the switching circuit 4 and the switching circuit 5 are connected to both ends of the primary side of the insulation/step-up transformer 6, as described above. Further, one of the secondary output ends of the insulation/step-up transformer 6 is connected to an electrode 51 of the ultrasound transducer 1 that does not come into contact with the patient via an inductance 8, and the other output end is connected to the The acoustic wave transducer 1 is electrically in contact with a patient and is connected to an electrode 52 having the same potential as the patient. Note that a portion having the same potential as the patient is shown as a region 9 indicated by a dotted line in FIG.

The inductance 8 is composed of a single coil or a plurality of coils, and together with an internal parallel capacitance inside the ultrasonic transducer 1, an LC filter is cut off at the resonance frequency, that is, the switching frequency of the ultrasonic transducer 1. It is designed to be configured.

The ultrasonic vibrator 1 is an ultrasonic vibrating element made of a piezoelectric element, and has two electrodes. one of the electrodes is a non-patient electrode and is designated by 51;
The other electrode is in electrical contact with the patient and has the same potential as the patient, and is designated by the reference numeral 52. Further, an internal capacitance component (not shown) exists inside the ultrasonic transducer 1, and as described above, the internal capacitance component and the inductance 8 are cut off at the switching frequency.
It is designed to constitute a C filter.

Next, the configurations of the drive signal generation circuit 3, the switching circuit 4, and the switching circuit 5 will be explained with reference to FIG.

In FIG. 2, a circuit indicated by a dotted line 3 shows one embodiment of the drive signal generation circuit 3, and a dotted line 4 indicates an embodiment of the drive signal generation circuit 3.
The circuits indicated by the dotted lines 5 and 5 are the switching circuits 4 and 5, respectively.
and one embodiment of the switching circuit 5 is shown.

In the drive signal generation circuit 3, the input terminal 10
is a terminal to which a source drive signal for controlling the drive of the power MOS-FETs 24 to 29, which are an example of the switching circuit 4 and the switching circuit 5, is input, and is connected to the input terminal of the inverter 11 via a resistor R31. . This inverter 11 is an element that inverts and outputs an input signal, and its output terminal is connected to the input terminal of the inverter 12 and the input terminal of the inverter 14, and supplies the output signal to the inverter 12 and the inverter 14. It is supposed to be done.

The output terminal of the inverter 12 is connected to a resistor R3.
The output terminal of the inverter 13 is connected to the input terminal of the buffer 17 via a parallel circuit composed of a resistor R33 and a capacitor C34. The buffer elements below the buffer 17, which will be described later, are inverted output buffers that invert and output an input signal. The output terminal of the buffer 17 is connected to a coupling capacitor C35.
It is connected to the input end of the buffer 18 via. At the input end of the buffer 18, the input signal is pulled up to the power supply via a pull-up resistor R36 and then input to the buffer 18. The output end of the buffer 18 is connected to one side (
Push side) Power MOS-F which is a switching circuit
It is connected to the gates of the ETs 24 to 26, and the power M
It is designed to supply to OS-FETs 24 to 26.

The output terminal of the inverter 14 is connected to the input terminal of the inverter 15 via a differentiating circuit composed of a capacitor C21, a fixed resistor R22, and a variable resistor R23. Hereinafter, similarly to the configuration described above, the output terminal of the inverter 15 is connected to the inverter 16 via the resistor R38.
The output end of this inverter 16 is connected to the input end of the buffer 19 via a parallel circuit composed of a resistor R39 and a capacitor C40. The output terminal of the buffer 19 is connected to a coupling capacitor C4.
1 to the input end of the buffer 20. still,
At the input end of the buffer 20, the input signal is pulled up to the power supply via a pull-up resistor R42 and then input to the buffer 20. The buffer 20
The output end of
It is connected to the gates of T27 to T29, and supplies the output signal to the power MOS-FETs 27 to 29 as the other switching circuit drive signal.

In the ultrasonic transducer drive circuit according to the embodiment of the present invention configured as described above, first, the drive signal generation circuit 3 generates two mutually complementary signals based on one source drive signal.
These two switching circuit drive signals cause the switching circuits 4 and 5 to perform a switching operation, and the ultrasonic transducer 1 is driven by this switching operation. These effects will be explained below with reference to FIGS. 2 and 3.

First, in the drive signal generation circuit 3, when a source drive signal as shown in FIG. 3(a) is input from the input terminal 10, the source drive signal is inverted by the inverter 11 and becomes an inverted source drive signal. , after being branched at the output end of the inverter 11, the inverter 12 and the inverter 14
is input.

One of the inversion source drive signals is input to the inverter 12 and inverted, and then inverted again by the inverter 13. The output signal of the inverter 13 is
After the pulse operation is stabilized by a parallel circuit formed by resistor R33 and capacitor C34, it is input to buffer 17 and inverted. The output signal of the buffer 17 is AC-coupled by a coupling capacitor 35, and then pulled up to the power supply via a pull-up resistor R36.
It is input to buffer 18. The output signal of this buffer 18 is AC-coupled by a coupling capacitor C37, and then is used as a push-side switching circuit drive signal as shown in FIG. FET24 or 2
6 gates are input.

On the other hand, the other of the inversion source drive signals is:
After being input to the inverter 14 and inverted, the signal is differentiated by a differentiating circuit composed of a capacitor C21, a fixed resistor R22, and a variable resistor R23, and converted into a differential signal. Thereafter, the differential signal is input to the inverter 15. At this time, the differential signal has a waveform as shown in FIG. 3(b).

Now, when the differential signal having a waveform as shown in FIG. 3(b) is input to the inverter 15,
This inverter 15 converts the input differential signal according to its own input threshold level as shown in FIG. 3(c).
It is recognized as a signal like the one shown in . Therefore, the output terminal of the inverter 15 has a waveform as shown in FIG. 3(e), that is, a waveform in which the pulse train of the source drive signal as shown in FIG. 3(a) is shifted by about one pulse. Output.

At this time, the pulse width of the final pulse of the pulse train of the signal as shown in FIG. It turns out. Therefore, in order to make the pulse width of the final pulse the same as the pulse width of the pulses before the final pulse in the output pulse train of the inverter 15, the time constant roughly set in the differentiating circuit can be adjusted using the variable resistor R23. good. As a result, the output pulse width of the inverter 15 becomes constant in response to variations in the input threshold level of the inverter 15.

The signal whose pulse width has been adjusted in this way is
Coupling capacitor 37 below inverter 13 mentioned above
In the same way as in the circuits up to this point, the signal passes through the circuit from the inverter 16 to the coupling capacitor 43, and is converted into a pull-side switching circuit drive signal as shown in FIG. 3(c).

As explained above, the drive signal generation circuit 3
The mutually complementary switching circuit drive signals generated by
It is input to T24 to T29. As a result, the power MOS-FETs 24 to 29 perform a push-pull switching operation in response to the switching circuit drive signal, and outputs generated at their respective drains are applied to both ends of the primary side of the isolation/step-up transformer 6. In addition, in this embodiment, three pairs of power M are used as a switching circuit.
Although a circuit in which the OS-FETs 24 to 29 are connected in parallel is employed, for example, a switching circuit using high-speed switching transistors may be employed.

Now, a DC power supply 7 is connected to the center tap of the insulation/step-up transformer 6 having an arbitrary step-up ratio, and the voltage of the DC power supply 7 is increased by the switching circuit 4 and the switching circuit 5. Push-pull switching is performed at the resonant frequency of the acoustic wave vibrator 1, and a voltage with an amplitude twice as high as the step-up ratio of the power supply voltage is excited at the output end of the isolation/step-up transformer 6. This excitation voltage is further boosted by an inductance 8, and at the same time, an LC filter composed of the inductance 8 and the parallel capacitance of the ultrasonic transducer 1 transforms the rectangular voltage waveform and the spike-like current waveform into Ultrasonic transducer 1
The signal is converted into a sine wave at a resonance frequency of , and is applied to the ultrasonic transducer 1.

[0034]

As explained above, according to the present invention, by employing a drive signal generation circuit with a simple configuration including an inversion circuit and a differentiation circuit, two mutually complementary switching signals can be generated from one source drive signal. Since it can generate circuit drive signals, it is possible to drive the ultrasonic transducer at high voltage and large current, and it is also possible to provide a small, inexpensive, and highly efficient ultrasonic transducer drive circuit. effective.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram schematically showing an ultrasonic transducer drive circuit in an embodiment of the present invention.

FIG. 2 is a circuit diagram showing details of an ultrasonic transducer drive circuit in an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing the process of generating two switching circuit drive signals in the ultrasonic transducer drive circuit according to the embodiment of the present invention.

[Explanation of symbols]

1...Ultrasonic vibrator 3...Drive signal generation circuit 4...Switching circuit 5...Switching circuit 6...Isolation/step-up transformer 7...DC power supply 8...Inductance 10...Input end 51...electrode 52...electrode

Claims (1)

[Claims] Claims: 1. An ultrasonic transducer having two electrode surfaces; an isolation transformer device that supplies alternating current signals with inverted phases to the two electrode surfaces; a push-pull switching means for supplying as a side input signal; a differentiating circuit that receives an AC rectangular wave source drive signal, generates a first drive signal according to the source drive signal, and differentiates the source drive signal; an inverting circuit that inverts the differential signal obtained by the differentiating circuit at a predetermined threshold value, and generates a second drive signal complementary to the first drive signal and delayed in phase with respect to the first drive signal. An ultrasonic transducer drive circuit comprising: a drive signal generation circuit that outputs a drive signal to the push-pull switching means.