JPH0234008A - Driver for ultrasonic vibrator - Google Patents

Abstract

PURPOSE:To obtain a driver for an ultrasonic vibrator able to be driven at the mechani cal resonance frequency at all times and able to eliminate a damping capacitor by providing 1st-3rd current detection means, the drive means for the vibrator and a characteristic adjusting means for a 2nd current detection means. CONSTITUTION:The gain of an operational amplifier 28 is set to Cd/Cc by adjusting a variable resistor 26 in response to the damping capacitance Cd measured in advance at first. Then a current ic flowing through the capacitor Cc is amplified by the ampli fier 28 at a multiple of Ca/Cc and a current id flowing to the capacitor Cd is obtained. Moreover, the amplifier 28 subtracts the current id from a current (i) flowing to an ultrasonic wave vibrator 10 to calculate a motional current ia flowing to a series circuit L-C-R. A phase comparator 30 detects a phase difference between the current ia and a voltage (v) applied to the vibrator 10 and controls the oscillating frequency of a VCO 12 via a filter 32 and an integration device 34 so as to make the phase difference zero. Thus, the vibrator is driven at the mechanical resonance frequency. Even if the capacitance Cd is dispersed, the driver is controlled under the optimum drive condition by the gain setting through the adjustment of the variable resistor 26.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a drive device for an ultrasonic transducer in an ultrasonic treatment device or the like.

[Conventional technology]

The conventional ultrasonic transducer drive circuit is disclosed in Japanese Patent Application Laid-Open No. 103-1983.
As described in Japanese Patent Laid-open No. 321 and Japanese Patent Application Laid-Open No. 51-3217, there is a phase-locked loop circuit using a phase comparator.

Alternatively, in order to detect the motional current of the vibrator, a coil (Japanese Patent Application No. 51-66419), a current transformer (Japanese Patent Application No. 54-81442), a differential transformer, or a bridge circuit and a differential amplifier can be used. (Special application 1972-15
No. 5955).

[Problem to be solved by the invention]

However, in these conventional examples, the phase difference between the voltage applied to the vibrator and the current flowing into the vibrator is controlled to be zero. For this reason, it is not always possible to drive at the mechanical resonance point, and the braking capacity cannot be completely removed.

Furthermore, when dealing with various vibrators, if the braking capacity changes depending on each vibrator, the braking capacity may not be removed. Further, even when one type of vibrator is used, if the braking capacity changes due to heat generation of the vibrator, changes over time, etc., the braking capacity may still not be removed.

As described above, in the conventional example, it cannot be said that the vibrators are driven under the optimum driving conditions for each vibrator, and the braking capacity cannot be removed.

This invention was made to deal with the above-mentioned circumstances,
The purpose is to provide an ultrasonic transducer drive device that can always drive at a mechanical resonance point and eliminate braking capacity even if the characteristics of the transducer change due to transducer replacement etc. .

[Means to solve the problem]

FIG. 1 shows an outline of the invention. The ultrasonic transducer 10 consists of a series circuit of C and R and a parallel circuit of a braking capacity Cd. The ultrasonic transducer 10 includes a voltage controlled oscillator (VCO) 1
A signal from 2 is supplied.

The current i flowing into the ultrasonic transducer 10 is detected by the current transformer 14 and supplied to the + side input terminal of the subtracter 16.

A braking current detector 18 is connected in parallel with the ultrasonic transducer 10, and the detected braking current id is supplied to one input terminal of the differential amplifier 16. As the braking current detector 18, there are various circuits such as a differentiation circuit that differentiates the voltage applied to the vibrator 10. Here, the detection characteristics of the braking current detector 18 are variable.

The output of the differential amplifier 16 is connected to a phase-locked loop (PLL
) is input to the circuit 20, and the output voltage of the PLL circuit 20 is V
It is supplied to the control voltage terminal of CO12.

[Effect]

The braking current detector 18 is an ultrasonic vibrator]-braking capacity c
Detect the current id flowing through d. The differential amplifier 16 calculates L by subtracting the current id flowing through the braking capacitance Cd from the current i flowing through the ultrasonic transducer 10 detected by the current transformer 14.

Calculate the current flowing in the series circuit of C and H, that is, the motional current ia.

The PLL circuit 20 performs resonance frequency tracking and amplitude control by comparing the phase of this motional current ia with a reference phase, thereby matching the oscillation frequency of the VCO 12 with the mechanical resonance frequency.

By changing the detection characteristics of the braking current detector 18, even when the braking capacity ff1cd of the vibrator changes, the detection output can be changed accordingly, making it possible to accurately detect the braking current id. As a result, the differential amplifier 16 can always accurately detect the motional current ia.

〔Example〕

Embodiments of an ultrasonic transducer driving device according to the present invention will be described below with reference to the drawings. In the following drawings, parts corresponding to those in FIG. 1 are designated by the same reference numerals.

FIG. 2 is a block diagram of the first embodiment. A capacitor Ce is connected in parallel to the ultrasonic transducer 10. The current ic flowing through the capacitor Cc is detected by the current transformer 24 and supplied to the inverting input terminal of the operational amplifier 28 via the variable resistor 26 .

Since the gain of the operational amplifier 28 is determined by the ratio between the variable resistor 26 and the feedback resistor 29, it can be varied by adjusting the variable resistor 26 to:i3.

Ultrasonic transducer 1 detected by current transformer 14
The current i flowing into 0 is supplied to the non-inverting input of the e&

The output ia of the operational amplifier 16 and the voltage V applied to the ultrasonic transducer 10 are input to the phase comparator 30.

The output of the phase comparator 30 is supplied to the pressure terminal of the control 2 of the VCO 12 via a filter 32 and an integrator 34. Phase comparator 30, filter 32, and integrator 34 are PLL circuits, circuit 2
Configure 0.

Next, the operation of the first embodiment will be explained. First, by adjusting the variable resistor 26 according to the value of the braking capacitance Cd measured in advance, the gain of the operational amplifier 28 is set to Cd/C.
Let it be c. As a result, the current ic flowing through the capacitor Cc is multiplied by Cd/Cc by the operational amplifier 28,
The current id flowing through the braking capacity is determined. That is, the variable resistor 26 and the operational amplifier 28 constitute the braking current detector 18-.

Furthermore, the operational amplifier 28 subtracts the braking current id from the current i flowing into the ultrasonic transducer 10, so that L, C
, R, the motional current ia flowing through the series circuit is calculated.

The phase comparator 30 detects the phase difference between the voltage V applied to the vibrator 10 and the motional current ia, and this phase difference is O.
VCO via filter 32 and integrator 34 so that
Controls 12 oscillation frequencies. Thereby, the ultrasonic transducer can be driven at the mechanical resonance frequency.

As described above, according to the first embodiment, the current id flowing through the braking capacitor 1tCd can be calculated from the current ic flowing through the capacitor Cc, and by subtracting this from the current i flowing into the vibrator, the motional current ia can be detected.

Even if the damping capacity Cd of the vibrator changes, the motional current can always be accurately detected by varying the variable resistor 26 accordingly and setting the amplification factor of the operational amplifier 28 to Cd/Cc. Can be done. Also,
Since braking capacity can be reliably removed, control can be achieved under optimal driving conditions.

FIG. 3 is a block diagram of the second embodiment.

A differentiation circuit 38 is connected in parallel with the VCO 12, and the voltage applied to the ultrasonic transducer 10 is differentiated, and the braking capacity ff1C is
A current id flowing through d is detected. This braking current id and the current i detected by the current transformer 14 and flowing into the ultrasonic transducer 10 are supplied to an adder 40 .

In the second embodiment, the current id flowing through the braking capacitance Cd is detected by differentiating the voltage applied to the ultrasonic transducer 10. That is, the differentiating circuit 38 constitutes the braking current detector 18.

Note that since the differentiating circuit 38 generates an inverted output, the adder 40 subtracts the braking current id from the current l flowing into the ultrasonic transducer 10 to calculate the motional current ia. Even if the damping capacitance Cd of the vibrator changes, the adder 40 always accurately detects the motional current by varying the variable resistor 38a of the differentiating circuit 38 and varying the constant of the differentiating circuit 38 accordingly. be able to.

Note that instead of varying the constant of the differentiating circuit 38, the variable resistor 3 connected between the differentiating circuit 38 and the adder 40
A similar effect can be obtained by changing the value of 9.

In the above-described embodiment, the detection characteristics of the braking current detector 18 were manually varied based on the braking capacity value set in advance.Next, the detection characteristics of the braking current detector 18 were automatically varied. An embodiment in which the value can be varied will be described.

FIG. 4 is a block diagram of the third embodiment. An oscillator (O20) 4 is connected in parallel with the VCO 12 that drives the ultrasonic transducer 10.
0 is connected. The oscillation frequency of 0SC40 is a constant frequency different from the mechanical resonance frequency of the ultrasonic transducer 10, and when the braking capacity cd is a predetermined value, the current i flowing from the 03C40 to the ultrasonic transducer 10 matches the braking current id. The frequency is set to The voltage applied to the ultrasonic transducer 10 from the VCO 12 is differentiated by the differentiating circuit 38, and the braking current id is determined. The output of the differentiating circuit 38 is supplied to the inverting input terminal of the differential amplifier 16 via the voltage controlled amplifier (VCA) 25. current transformer 1
The current i flowing into the ultrasonic transducer 10 detected by 4
is supplied to the non-inverting input terminal of the differential amplifier 16.

The current flowing from the 09C40 to the ultrasonic transducer 10 is detected by the current transformer 42 and inputted to the control voltage terminal of the VCA 25 via the smoothing rectifier circuit 44.

In the third embodiment, when the braking capacity Cd changes from the above-mentioned predetermined value, the current i flowing into the ultrasonic transducer 10 from 03C40 is no longer the braking current id, and the detected value of the current transformer 42 changes. As a result, the control voltage input to the VCA 25 via the smoothing rectifier circuit 44 changes, so the amplification factor of the VCA 25 changes, and the output of the VCA 25 can always represent the braking current id.

As described above, according to the third embodiment, changes in braking capacity can be detected while the vibrator is being driven, and the characteristics of the braking current detector can be automatically varied accordingly, and the driving conditions can be adjusted based on this braking current. By controlling this, optimal driving conditions can always be obtained.

FIG. 5 is a block diagram of the fourth embodiment.

The voltage applied to the ultrasonic transducer 10 from the VCO 12 is differentiated by the differentiating circuit 38, and the braking current id is determined. The output of the differentiating circuit 38 is supplied to the inverting input terminal of the differential amplifier 16. Current i detected by current transformer 14 is supplied to a non-inverting input terminal of differential amplifier 16.

The current flowing from the 08C40 to the ultrasonic transducer 10 is detected by the current transformer 42 and inputted to the control terminal of the variable capacitor 38b in the differentiating circuit 38 via the smoothing rectifier circuit 44. The capacitance of the variable capacitor 38b is varied according to the input voltage of the control terminal.

Also in the fourth embodiment, when the braking capacity ff1cd changes, the detected value of the current transformer 42 changes, and as a result, the constant of the differentiating circuit 38 changes, so the differentiating circuit 38
The output of can always represent the braking current id. As a result, the braking capacity can be reliably removed, so that control can be achieved under optimal driving conditions.

FIG. 6 is a block diagram of the fifth embodiment. The fifth embodiment differs from the third embodiment in that the VCO 12 and the OSC 40 are switched by a selector 46, and either one is connected to the ultrasonic transducer 10. Along with this, the output of the smoothing rectifier circuit 44 is temporarily held in the holding circuit 48, and the output is transferred to the VCA2.
It is input to the control voltage terminal of 5.

According to the second embodiment, when detecting the braking current, the selector 46
is switched to the 08C40 side, and the braking current id detected by the current transformer 42 is held in the holding circuit 48.

When driving the ultrasonic transducer 10, the selector 46 is set to VCO.
Switch to the 12 side.

At this time, the current transformer 42 does not detect the braking current id, so the amplification factor of the VCA 25 is determined by the data held in the holding circuit 48.

〔Effect of the invention〕

As explained above, according to the present invention, even if the resonator changes and the damping capacity of the resonator changes, the gain of the operational amplifier, the constant of the differentiating circuit, or the gain of the voltage control amplifier is adjusted accordingly. As a result, an ultrasonic transducer driving device that can always accurately detect the mossinal current, reliably eliminate the influence of braking capacity, and optimally drive the ultrasonic transducer at the mechanical resonance point is realized.

[Brief explanation of the drawing]

FIG. 1 is a block diagram schematically showing a drive device for an ultrasonic transducer according to the present invention, FIG. 2 is a block diagram of a first embodiment of the drive device for an ultrasonic transducer according to the present invention, and FIG. FIG. 4 is a block diagram of the third embodiment of the invention, FIG. 5 is a block diagram of the fourth embodiment of the invention, and FIG. 6 is the fifth embodiment of the invention. FIG. 10... Ultrasonic vibrator, 12... VCo, 14...
-Current transformer, 16...subtractor, 18...braking current detection circuit, 16...PLL circuit.

Claims (1)

[Claims] a first detection means for detecting the current flowing into the ultrasonic transducer; and a second detection means for detecting the current flowing through the braking capacity of the ultrasonic transducer.
a detection means, a means for detecting a motional current from the outputs of the first and second detection means, a means for driving the ultrasonic transducer based on the motional current, and a means for driving the ultrasonic transducer according to the braking capacity of the ultrasonic transducer. An ultrasonic transducer driving device comprising means for adjusting characteristics of the second detection means.