JPH0286874A - Driving circuit for ultrasonic wave vibrator - Google Patents

Abstract

PURPOSE:To prevent sudden change in stress at the time of start-up of a vibrator by supplying a control signal to a voltage controlling amplifier circuit and providing a control circuit for controlling the amplification factor. CONSTITUTION:When vibration start of an ultrasonic wave vibrator 14 is indicated, the amplification factor of a voltage controlling amplifier circuit 2 is gradually increased from zero or extremely small value by a control circuit 3 and regulated to the prescribed amplification factor at the elapse of constant time after start-up thereof. This prescribed amplification factor is decided to such value that the ultrasonic wave vibrator 14 can oscillate required intensive ultrasonic wave. The amplification factor is controlled so as to hold this prescribed amplification factor after the elapse of constant time. Therefor since amplification of ultrasonic wave vibration is gradually increased, sudden change in stress is not caused at a time of start-up. By such control, a control signal Vc supplied to the voltage controlling amplifier circuit 2 from the control circuit 3 is made zero at a time of start-up and gradually increased until constant time t1 elapses and held at prescribed value Vc1 after the elapse of constant time t1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a drive circuit for an electrostrictive type ultrasonic vibrator used in machining, medical treatment, etc.

[Prior Art] Conventionally, there has been an ultrasonic device that converts electro-mechanical vibration using a bolted Langevin type ultrasonic transducer, magnifies the vibration with a horn, and then transmits it to living tissue to ablate the living tissue. being developed. In such devices, large distortions occur in the vibration system components when they are driven, and it is necessary to take mechanical strength, etc. into consideration when designing and selecting materials. Furthermore, on the drive circuit side, a protection circuit is provided to prevent destruction and deterioration of the vibration system due to excessive vibrations and sudden changes in stress.

As an example of such a drive circuit, Japanese Patent Publication No. 7877/1987 describes a drive circuit that changes the set value of a constant current source for driving an ultrasonic perturber depending on whether it is loaded or not. Here, in order to prevent unnecessary power consumption during no load and temperature rise of the resonator and current control transistor, the presence or absence of a load is detected by the admittance of the resonator, and the setting time is reduced during no load. .

Additionally, there is a device in which a starting shock mitigation circuit is installed in the power amplifier circuit in order to prevent the circuit elements from receiving electrical shock at the start of oscillation, and to make it easier to start up when the vibration system is under load. It is described in Japanese Patent Application Laid-Open No. 58-58034.

[Problems to be Solved by the Invention] In the former device, when the no-load state changes to the loaded state, the set value of the constant current source changes rapidly, so a sudden stress change is unavoidable.

Furthermore, since the admittance of the vibration system changes when the tip member of the vibration system is replaced, it may be impossible to detect the presence or absence of a load from the admittance of the vibrator.

Also, in the latter device, a sudden change in stress at the start of oscillation was unavoidable.

This invention was made to deal with the above-mentioned circumstances,
The purpose is to provide a drive circuit for an ultrasonic transducer that prevents sudden changes in stress when the transducer is activated.

[Means for Solving the Problems] As shown in FIG. 1, the ultrasonic transducer drive circuit according to the present invention generates a drive signal that causes an ultrasonic transducer 14 comprising a piezoelectric transducer 5 and a horn 6 to oscillate. an oscillation circuit 1 that amplifies the output signal of the oscillation circuit 1 with a variable amplification factor, a power amplification circuit 4 that amplifies the output signal of the voltage control amplification circuit 2 and supplies it to the ultrasound transducer 14; A control circuit 3 is provided that supplies a control signal to the voltage-controlled amplifier circuit 2 to control its amplification factor.

[Function] In this drive circuit, the ultrasonic transducer 14 starts vibrating (
When there is an instruction (start-up), the control circuit 3 starts the voltage control amplifier circuit 2.
The amplification factor is gradually increased from 0 or a very small value, and is brought to a predetermined amplification factor after a certain period of time after startup. This predetermined amplification factor is determined to a value that allows the ultrasonic transducer 14 to oscillate a desired strong ultrasonic wave. After a certain period of time, the amplification factor is controlled to be maintained at this predetermined amplification factor. Therefore, since the amplitude of the ultrasonic vibration gradually increases, no sudden stress change occurs at startup.

FIG. 2 shows a control signal Vc supplied from the control circuit 3 to the voltage control amplifier circuit 2 for such control. That is, the control signal Vc is O at startup, and for a certain period of time t1.
It gradually increases until the predetermined time t1 has elapsed, and is maintained at the predetermined value Vcl after the predetermined time t1 has elapsed.

[Example] Hereinafter, an example of the driving circuit for an ultrasonic transducer according to the present invention will be described.

FIG. 3 is a block diagram of the first embodiment. A signal from the oscillation circuit 1 is supplied to the multiplication circuit 7. The output of the multiplication circuit 7 is supplied to the piezoelectric transducer 5 of the ultrasonic transducer 14 via the power amplification circuit 4. The ultrasonic transducer 14 includes a piezoelectric transducer 5,
Consists of 6 horns.

By setting the coefficients of the multiplier circuit 7, the power amplifier circuit 4
The output of an amplitude setting circuit 9 consisting of a variable voltage source that sets the amplitude of the input signal is supplied to the + side input terminal of the comparator 12 via a start switch 30 and a resistor R. + of comparator 12
The side input terminal is connected to ground or a reference potential via a relay switch 10 and a capacitor C.

The signal from the start switch 30 is supplied to the timer circuit 11, and the signal from the timer circuit 11 is supplied to the relay switch 1.
0.

A current detector 8 is installed between the power amplifier circuit 4 and the ultrasonic transducer 14.
is connected, and the output VF of the current detector 8 is supplied to one side input terminal of the comparator 12. The comparator 12 detects the voltage Vc at the connection point between the resistor R and the relay switch 10, and the current detector 8.
, that is, the voltage vF corresponding to the amplitude of the current value flowing through the ultrasonic transducer 14, and supplies a voltage signal corresponding to the difference to the multiplication circuit 7. The multiplication circuit 7 is a comparator 12
The output signal of the oscillation circuit 1 is multiplied by the output signal of the oscillation circuit 1, and the multiplied signal is supplied to the power amplifier circuit 4.

The operation of the first embodiment will be explained. First, the ultrasonic vibrator 14
The amplitude is set by the amplitude setting circuit 9 before starting up. When the start switch 30 is pressed, the timer circuit 11 is started, the relay switch 10 is turned on, and the capacitor C is connected to the + side input terminal of the comparator 12. As a result, a time constant circuit of resistor R and capacitor C is formed. Therefore, the input voltage Vc to the + side input terminal of the comparator 12 gradually increases due to this time constant circuit.

When a certain period of time t1 has elapsed since the start switch 30 was turned on, the timer circuit 11 turns off the relay switch 10. As a result, the capacitor C is disconnected from the resistor R, and the voltage Vc supplied to the + side input terminal of the comparator 12 matches the setting value of the amplitude setting circuit 9.

FIG. 4(a) shows the relationship between the input voltage Vc and time when the set voltage is high, and FIG. 4(b) shows the relationship between the input voltage Vc and time when the set voltage is low.

The comparator 12 compares the output voltage VF of the current detection circuit 8 and the input voltage Vc, and supplies a voltage corresponding to the difference to the multiplication circuit 7. The multiplier circuit 7 multiplies (amplifies) the output of the oscillation circuit 1 by a predetermined number so that the output VF of the current detection circuit 8 and the input voltage VC match. Thereby, even if the current flowing through the ultrasonic transducer 14 varies depending on the magnitude of the load, a predetermined power can always be supplied to the ultrasonic transducer 14.

In this way, irrespective of the setting value of the amplitude setting circuit 9, the amplitude of the ultrasonic transducer can smoothly approach a predetermined value by appropriately setting the resistor R and the capacitor C1 timer time t1.

Further, according to this embodiment, the oscillation circuit 1 and the power amplifier circuit 4 operate and are in a warm-up state during the period from when the power is turned on until when the start switch 30 is pressed.

Therefore, when the start switch 30 is pressed, stable operation starts immediately. No matter what the load condition of the ultrasonic transducer 14 is, the amplitude is gradually increased by the time constant circuit of CR from startup to a predetermined time t1, and after the predetermined time t1, the amplitude is gradually increased by the time constant circuit of the CR. Since the circuit is disconnected, complete constant current control is performed without any operational delay.

Therefore, a sudden stress change does not occur in the ultrasonic transducer 14 at the time of startup, and stable constant current control is performed after startup.

Next, a second embodiment will be explained. FIG. 5 is a block diagram of the second embodiment. The output of the voltage controlled oscillator 21 is supplied to the ultrasonic transducer 14 via the multiplication circuit 7, relay contact 411, power amplification circuit 4, and matching circuit 20. The matching circuit 20 is a circuit that performs matching for efficient driving.

The matching circuit 20 includes a voltage detection circuit 201 that detects the phase of the drive voltage of the ultrasonic transducer 14, a current detection circuit 202 that detects the phase of the drive current of the ultrasonic transducer 14, and an amplitude detection circuit 202 that detects the phase of the drive current of the ultrasonic transducer 14. It has a current value detection circuit 203 that detects. The outputs of the voltage detection circuit 201 and the current detection circuit 202 are supplied to the phase comparison circuit 23. The phase comparator circuit 23 supplies a voltage signal corresponding to the difference between both phases to the control terminal of the voltage controlled oscillator 21 via a low pass filter (LPF) 22. Note that the control terminal of the voltage controlled oscillator 21 is grounded via a relay contact 421. The low-pass filter 22 removes harmonic components of the output of the phase comparison circuit 23. The voltage controlled oscillator 21 generates a signal for driving the ultrasonic transducer 14 at a resonant frequency at which the output of the phase comparison circuit 23 becomes 0, that is, the phase difference between the drive voltage and drive current of the transducer 14 becomes 0.

On the other hand, an amplitude lower limit setting variable resistor (VR) 27, an amplitude setting variable resistor 25, and an amplitude upper limit setting variable resistor 26 are connected in series. The amplitude upper limit setting variable resistor 26 sets the upper limit of the amplitude setting voltage so as to prevent the ultrasonic transducer 14 from causing damage due to excessive amplitude. Amplitude setting variable resistor 2
The output of 5 is connected to the non-inverting input terminal of the differential amplifier 24. The output of the current value detection circuit 203 is connected to the inverting input terminal of the differential amplifier 24 via a resistor 54. The output terminal of the differential amplifier 24 is connected to the inverting input terminal via a feedback resistor 53. The output terminal of the differential amplifier 24 is connected to the multiplication circuit 7.

The output of the amplitude setting variable resistor 25 is also connected to one end of the capacitor 28 via a relay contact 431. capacitor 2
The other end of 8 is connected to the connection point between the amplitude lower limit setting variable resistor 27 and the amplitude setting variable resistor 25. In addition, the capacitor 28
A relay contact 422 and a resistor 51 are connected in series between both ends.

The start switch 30 is connected to a timer circuit 11, and the timer circuit 11 controls the relays 41, 42, 43. Relay 41 connects relay contact 411, relay 42 connects relay contacts 421 and 422, and relay 43 connects relay contact 4.
31 respectively.

Here, details of the timer circuit 11 are shown in FIG. The output of the start switch 30 is connected to the clock terminal CK of the J- type flip-flop 31 through inverters 64 and 65 in series.
is input. The output terminal of the flip-flop 31 is connected to the base of the transistor 61, and is also connected to the clock terminal CK of the timer IC32 via the inverter 66.
is also connected to. The emitter of transistor 61 is grounded, and its collector is connected to relay 41.

The output terminal of the timer IC 32 is connected to the base of the transistor 62 via a NOR gate 67.

The emitter of transistor 62 is grounded and the collector of transistor 62 is connected to relay 42 .

The output of the NOR gate 67 is connected to the clock terminal CK of the timer IC 33 via an inverter 68. The output terminal of the timer IC 33 is connected to the base of the transistor 63 via a NOR gate 69. The emitter of transistor 63 is grounded, and its collector is connected to relay 43.

The operation of the second embodiment will be explained with reference to FIG.

Before startup, the resistance values of the amplitude lower limit setting variable resistor 27, the amplitude setting variable resistor 25, and the amplitude upper limit setting variable resistor 26 are set in advance. From power on to startup, all relays 4
1, 42, and 43 do not operate, and the input terminal of the power amplifier circuit 4 is grounded via the contact 411 of the relay 41 and the resistor 55. Therefore, the output of the power amplification circuit 4 is not affected by noise or the like, and the ultrasonic transducer 14 does not erroneously vibrate. The output of the low-pass filter 22 is grounded via the contact 421 of the relay 42 . Therefore, the voltage controlled oscillator 21 is in a free-running oscillation state. A resistor 51 is connected across the capacitor 28 via a contact 422 of the relay 42 , and the capacitor 28 is connected to a non-inverting input terminal of the differential amplifier 24 via a contact 431 of the relay 43 .

Therefore, the voltage Vc at the non-inverting input terminal of the differential amplifier 24
is a voltage value set by the amplitude lower limit setting variable resistor 27.

When the start switch 30 is pressed, the flip-flop 3
An L level pulse as shown in FIG. 7(a) is supplied to the clock terminal CK of No. 1. As a result, Fig. 7(b)
As shown in FIG. 3, the output of the flip-flop 31 becomes H level. As a result, as shown in FIG. 7(C), the relay 4
1 turns on, and the timer IC 32 starts operating. When the relay 41 is turned on, the output of the multiplier 7 is supplied to the power amplifier circuit 4 via its contact 411.

For this reason, the power amplification circuit 4 supplies the ultrasonic transducer 14 with a drive voltage having a value set by the amplitude lower limit setting variable resistor 27. At this time, the phase comparison circuit 23 compares the detected voltage phase of the voltage detection circuit 201 and the detected current phase of the current detection circuit 202, and outputs a signal according to the comparison result. The value of the amplitude lower limit setting variable resistor 27 is determined so that the phase comparison circuit 23 can sufficiently detect the phase, and the amplitude setting voltage is such that it does not give much shock to the ultrasonic transducer 14.

The output of the timer IC 32 becomes H level after a predetermined period of time, and as a result, the relay 42 is turned on as shown in FIG. 7(d), and the timer IC 33 starts operating. When the relay 42 is turned on, its contact 421 is turned off, so the output of the low-pass filter 22 is supplied to the voltage controlled oscillator 21. The voltage controlled oscillator 21, the low-pass filter 22, and the phase comparison circuit 23 constitute a circuit that tracks the resonance frequency of the ultrasonic transducer. At this time, since the contact 422 is opened, the voltage VC at the non-inverting input terminal of the differential amplifier 24 gradually increases due to the CR circuit of the capacitor 28 and the amplitude setting variable resistor 25, as shown in FIG. 7(f). do.

The output of the timer IC 33 becomes H level after a predetermined period of time, thereby turning on the relay 43 as shown in FIG. 7(e). When the relay 43 is turned on, the contact 431 is opened, the capacitor 28 of the CR circuit is disconnected, and the voltage VC at the non-inverting input terminal of the differential amplifier 24 becomes the amplitude setting voltage as shown in FIG. 7(f). Constant current control.

In addition, in the above-mentioned first and second embodiments, a mechanical contact type relay was used to control the on/off etc. of the time constant circuit.
Instead of them, a field effect transistor (FET) 40 as shown in FIG. 8 may be used.

Next, a third example will be described. FIG. 9 is a block diagram of a third embodiment, which is used, for example, in an ultrasonic surgical device. The piezoelectric transducer 5 is designed such that, for example, probes A61 and t't probes B62 of different lengths can be used by replacing them as appropriate depending on the purpose.

The same parts as in the second embodiment shown in FIG. 5 are given the same reference numerals, and their explanation will be omitted.

The probe discrimination circuit 80 is a circuit that discriminates the type of probe connected to the piezoelectric transducer 5 and the horn 6.

The probe discrimination circuit 80 discriminates the type of probe that is connected based on, for example, differences in impedance characteristics and information manually input from an operation panel (not shown).

The discrimination signal generated by this probe discrimination circuit 80 is sent to switching circuits 97 and 98, which will be described later.

The voltage generation circuits 91 and 92 each have a probe A61.
and a voltage generating circuit 93.94 that generates a voltage for determining the maximum amplitude setting value in the probe B62.
similarly generates a voltage for determining the minimum amplitude setting. The switching circuit 97 selects the output of either the voltage generation circuit 93 or the voltage voicing circuit 94 based on the discrimination signal from the probe discrimination circuit 80 and outputs the minimum amplitude set value. Similarly, the switching circuit 98, based on the discrimination signal from the probe discrimination circuit 80,
The output of either the voltage generating circuit 91 or the voltage generating circuit 92 is selected to output the maximum amplitude and set value.

99. 100 and 101 are analog switches; 102 is a resistor that constitutes a CR time constant circuit together with the capacitor 28;
103 is a diode for discharging the capacitor 28;
04.105 is a diode for preventing backflow. 95 is a foot switch that controls oscillation/stop of the ultrasonic transducer 14. The output of this foot switch 95 is supplied to a control circuit 96. Based on the signal from the foot switch 95, the control circuit 96
Control signals TI, T2 . T3 is generated to temporally control on/off of the analog switches 99, 100, and 101. This control circuit 96 receives a lock detection signal from the phase comparator circuit 23, which indicates that the PLL (lower phase lock loop) has locked to the resonance point frequency and tracking operation has started.

The operation of the third embodiment will be explained with reference to FIG. In the initial state, each analog switch 99°, 100, and 101 is off. Further, in response to a discrimination signal from the probe discrimination circuit 80 indicating that, for example, the probe A61 is connected, the switching circuits 97 and 98 switch the outputs of the voltage generation circuit 91 and the voltage generation circuit 93 that are compatible with the connected probe A61, respectively. is selected, and the maximum amplitude setting voltage and minimum amplitude setting voltage suitable for probe A61 are output.

When the foot switch 95 is pressed in this state and the signal from the foot switch 95 rises as shown in FIG. 10(a), the control signal T1 is first output from the control circuit 96 as shown in FIG. The signal is output and the analog switch 99 is turned on. This makes the diode 10
A voltage of the minimum amplitude setting value is inputted to the non-inverting input terminal of the differential amplifier 24 through 5, thereby causing the PLL to enter a resonance point tracking operation. During this resonance point tracking operation, the amplitude is feedback-controlled at the set minimum value. Next, when the tracking operation is completed and the PLL enters the locked state, the first
As shown in FIG. 0 (C), the phase comparator 23 outputs a lock detection signal indicating this. When this lock detection signal is supplied to the control circuit 96, the control circuit 96 outputs the control signal T2 to turn on the analog switch 100 (see FIG. 10(d)). As a result, the maximum amplitude setting voltage and the minimum amplitude setting voltage are applied to both ends of the amplitude setting variable resistor 25, and the voltage divided by the amplitude setting variable resistor 25 is applied to the variable resistor 102 and the capacitor 2.
The signal is supplied to a time constant circuit consisting of 8 and 8. As explained in the second embodiment, the output voltage of this time constant circuit gradually increases over time and is then applied to the non-inverting input terminal of the differential amplifier 24 (the first
(See Figure 0(f)). Then, after a certain period of time t1 has elapsed, the control circuit 96 outputs a control signal T3 and turns on the analog switch 101, thereby shorting the variable resistor 102, and as shown in FIG. 10(e), the amplitude setting variable resistor 25 The divided voltage is input as is to the non-inverting input terminal of the differential amplifier 24.

Here, even if the variable resistor 102 is short-circuited, a time constant circuit is formed by the amplitude setting variable resistor 25 and the capacitor 28, but the resistance value of the variable resistor 102 is made relatively large and the capacitance of the capacitor 28 is made small. Moreover, if the resistance value of the amplitude setting variable resistor 25 is kept small, the time difference in which the actual amplitude setting is delayed with respect to the setting by the amplitude setting variable resistor 25 can be minimized, so that normal operation is not affected.

Further, when the foot switch 95 is turned off, each of the analog switches 99, 100', and 101 is turned off, and the electric charge accumulated in the capacitor 28 is discharged through the diode 103.

When the probe is replaced from A to B, a discrimination signal from the probe discrimination circuit 80 indicating that the probe B62 is engaged causes the switching circuits 97 and 98 to switch to voltage generating circuits that are compatible with the coupled probe B62. 92 and the outputs of the voltage generating circuit 94 are switched to output the maximum amplitude setting voltage and the minimum amplitude setting voltage suitable for the probe B 62, and the same operation as above is performed thereafter.

In the above embodiment, the analog switch 101 is removed so that the amplitude changes gradually even when the ultrasonic transducer 14 stops oscillating, and the amplitude changes to 0 using the discharge of the capacitor 28. It's okay.

Further, in the above embodiment, the ultrasonic transducer 14 is used for amplitude control.
As shown in Fig. 11,
A signal obtained from the vibration detector 106 may also be used.

As described above, according to the third embodiment, even if the type of probe is changed, it is possible to provide an apparatus in which the amplitude inrush change can be alleviated within the range of the maximum amplitude setting value at which the probe will not be destroyed. In addition, by appropriately setting the value of the variable resistor 102 and the fixed time t1, it is possible to follow the change in the resonance point in the process of increasing vibration to the set amplitude after the resonance point tracking lock of the PLL is completed at the minimum amplitude setting value. This has the effect of improving the reliability of oscillation.

Next, a fourth embodiment will be described. FIG. 12 is a block diagram of the fourth embodiment. In this embodiment, the control circuit 3
The microprocessor 320 is used to control the activation of the ultrasonic transducer 14.

The control circuit 3 is composed of a microprocessor 320 and a D/A converter 310. The other parts are the same as those shown in FIG. 1 mentioned above, so the explanation will be omitted.

When the microprocessor 320 detects an instruction to start oscillation (activation) of the ultrasonic transducer 14, the microprocessor 320 generates a waveform that gradually increases in a stepwise manner and becomes a constant value after a certain period of time t1 has elapsed, as shown in FIG. generates and outputs a digital signal. This digital signal is converted into an analog signal by the D/A converter 310 and supplied to the voltage control amplifier circuit 2. Thereby, the voltage control amplifier circuit 2 controls the drive signal from the oscillation circuit 1 so as to gradually increase the amplification factor according to the output signal of the control circuit 3. The signal from this voltage control amplifier circuit 2 is passed through a power amplifier circuit 4 to a piezoelectric converter 6 and a horn 6.
is supplied to an ultrasonic transducer consisting of. As a result, the amplitude of the ultrasonic vibration of the ultrasonic vibrator increases gradually, and sudden stress changes do not occur.

With this configuration, changes in the amplitude increase (temporal changes and voltage changes) of the ultrasonic vibration of the ultrasonic transducer can be easily set using software built into the microprocessor 320. Furthermore, since the change in the amplitude increase can be easily changed by changing the software, there is also the effect that the adjustment of the apparatus is simplified.

[Effects of the Invention] According to the present invention, there is provided an ultrasonic transducer drive circuit that prevents sudden changes in stress when starting the ultrasonic transducer.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing a driving circuit for an ultrasonic transducer according to the present invention, FIG. 2 is a diagram showing the operation of FIG. 1, and FIG. Block diagram of the embodiment, FIG. 4(a). (b) is a diagram showing the operation of the first embodiment, FIG. 5 is a block diagram of the second embodiment of the ultrasonic transducer drive circuit according to the present invention, and FIG. 6 is a detailed diagram of the timer circuit of the second embodiment. 7 is a diagram showing the operation of the second embodiment, FIG. 8 is a diagram showing a modification, and FIG. 9 is a block diagram of the third embodiment of the ultrasonic transducer drive circuit according to the present invention. , FIG. 10 is a diagram showing the operation of the third embodiment, FIG. 11 is a diagram showing a modified example, FIG. 12 is a block diagram of the fourth embodiment of the ultrasonic transducer drive circuit according to the present invention, and FIG. 13 is a diagram showing the operation of the third embodiment. The figure is a diagram for explaining the operation of the fourth embodiment. 1... Oscillation circuit, 2... Voltage control amplifier circuit, 3...
- Control circuit, 4... Power amplifier circuit, 5... Piezoelectric transducer, 6... Horn, 14... Ultrasonic vibrator. 3 Figure 8 Figure 12 Figure 13

Claims (1)

[Claims] means for generating a drive signal for an ultrasonic transducer; means for amplifying the drive signal with a variable amplification factor; and gradually increasing the amplification factor of the amplification means until a predetermined time elapses from activation;
A driving circuit for an ultrasonic transducer, comprising a control means for setting a predetermined gain after a predetermined time has elapsed.