JPS6335828Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an electrostrictive vibrator drive device used in various ultrasonic processing machines.

An electrostrictive vibrator is represented by an equivalent circuit as shown in FIG. 1a, and always has a capacitive reactance Co between electrodes. This interelectrode reactance Co is
It does not contribute to electrical-mechanical energy conversion and is
On the admittance curve shown in Figure b, the resonance circle is moved upward by jwco.

In general, an electrostrictive vibrator drive device amplifies the output of an oscillating section 1 with an amplifying section 2, as shown in FIG.
It is designed to drive the electrostrictive vibrator P with the output of
to maintain efficient operation.
It is configured using PLL. That is, in the oscillation unit 1, the voltage controlled oscillator 13 is connected to the phase detector 11.
A control signal Si corresponding to the drive voltage and drive current is fed back to the phase detection circuit 11.

In such a configuration, for example, a circuit as shown in FIG. 3 has been used as the current detection circuit 3 for detecting a signal corresponding to the drive current. That is, the primary side of the feedback transformer _T3 is connected in series between the output of the amplifier section 2 and the electrostrictive vibrator P, and a tuning circuit that tunes around the resonance frequency of the electrostrictive vibrator is connected to the secondary side. The output of the tuned circuit was fed back to the phase detection circuit 11 via the phase shifter 4 as a control signal Si.

However, when the electrostrictive vibrator is driven with a rectangular wave in this configuration, the current Io flowing through the capacitive interelectrode reactance Co described above becomes a differential waveform as shown in FIG. 8d, and is mixed into the drive current Ip. Therefore, the feedback control signal Si (FIG. 8f) is often mixed with a substantially sinusoidal signal So as shown by the broken line in FIG. 8g, causing malfunctions.

This idea is based on the fact that the signal So corresponding to the differential wave-like current flowing through the interelectrode reactance Co is the control signal.
It is an object of the present invention to provide an electrostrictive vibrator drive device that prevents contamination with Si and allows the entire circuit to operate normally.

This idea is applied to an electrostrictive vibrator drive device equipped with the PLL described above, in which a current detection circuit 3 is used as shown in FIG.
The first current detection circuit 31 detects a signal Sp corresponding to the current Ip flowing through the electrostrictive vibrator itself, and the current Io flowing through the interelectrode reactance Co of the electrostrictive vibrator.
A second signal So′ corresponding to a current equivalent to
The main feature is that the above object is achieved through a configuration in which the outputs of the current detection circuit 32 are superimposed in opposite phases via a voltage regulator, and will be described in more detail below.

FIG. 5 shows an embodiment of this invention, which is applied to an ultrasonic processing machine using an electrostrictive vibrator, especially a dental ultrasonic scaler. The oscillator 1 controls the oscillation frequency of the voltage controlled oscillator 13 using the output of the phase detector 11, and an amplifier circuit 12 is inserted between the two. Reference numeral 14 denotes a loop filter, which is a type of low-pass filter.The output of the oscillation section 1 is input to the amplification section 2.

The amplifier section 2 includes a driver 21 and the driver 21
It consists of two switching transistors Q ₂₁ Q ₂₂ driven by , and its output drives the electrostrictive vibrator P via the output transformer T ₂ . The output transformer _T2 isolates the electrostrictive vibrator P from the drive circuit to ensure the safety of the human body, and at the same time functions as a step-up transformer.

Control signal corresponding to the drive voltage of the electrostrictive vibrator P
The loop returning Se to the phase detector 11 is taken from the output of the voltage controlled oscillator 13. A control signal Si corresponding to the drive current is detected using a current detection circuit 3 described below and returned to the phase detector 11. In Fig. 5, 4 is a phase shifter, which is used to adjust the phase of the control signal Se corresponding to voltage and the control signal Si corresponding to current to an optimum value, and returns the control signal Si. It is sufficient if it is provided at any position on the loop (Figures 1 and 2).
(see figure).

Further, 6 is a power controller which can adjust the supplied power according to an increase or decrease in the load on the circuit. That is, by adjusting the variable resistor VR ₆ , the base current of the transistor Q ₆ is adjusted, and thus the collector current is increased or decreased depending on the load.

The current detection circuit 3 includes a first current detection circuit 31 and a second current detection circuit 32, which will be described below.

The first current detection circuit 31 is configured as follows.
First, the primary side of the first feedback transformer _T31 is connected in series with the output of the amplifier section 2 and the electrostrictive vibrator P. Next, a tuning capacitor C ₃₁ is connected in parallel to provide a tuning circuit that tunes around the resonance frequency o of the electrostrictive vibrator on the secondary side. however,
The Q of this tuned circuit is lower than the Q of the electrostrictive vibrator P. That is, this is to operate so that the driving frequency of the electrostrictive vibrator P automatically tracks the resonance frequency o of the electrostrictive vibrator itself. If the Q of the electrostrictive vibrator P is lower than the Q of the tuned circuit, the drive frequency will automatically track the resonant frequency of the tuned circuit, and the purpose of this device will not be achieved.

The second current detection circuit 32 is provided before the first current detection circuit 31 as described below.

First, the primary side of the second feedback transformer _T32 is connected in series to the output of the amplifier 2 and the detection reactance _C3 , with the detection reactance C3 being used as a load. This detection reactance _C3 is intended to detect a current equivalent _to the current flowing through the interelectrode reactance Co of the electrostrictive vibrator P. It is therefore desirable that the reactances of both are approximately equal. A tuning capacitor _C32 is also connected in parallel to the secondary side of the second feedback transformer _T32 , providing a tuning circuit that tunes in the vicinity of the resonance frequency o of the electrostrictive vibrator P. The Q of this tuning circuit is also set lower than the Q of the electrostrictive vibrator.
The Q of the tuning circuits provided in the first and second feedback transformers _T31 and _T32 is approximately equal to each other.

Voltage regulator 34 which describes the above two detection circuits below.
If they are connected in opposite phase to each other through the electrostrictive vibrator P
This means that the voltage So corresponding to the current Io flowing through the electrode reactance Co can be removed from the control signal.

As the voltage regulator 34, a variable resistor _VR3 is generally used. In FIG. 5, both detection circuits 3
The outputs of 1 and 32 are input in opposite phases to both ends of a variable resistor as a voltage regulator, and a control signal is output from the variable terminal.
Taking out Si. Configure it like this,
By changing the position of the variable terminal, the voltage So corresponding to the current Io flowing through the interelectrode reactance Co
and the voltage So' corresponding to the current Io flowing through the detection reactor _C3 are made equal, and as a result, the voltage So' corresponding to the current Io flowing through the interelectrode reactance is equalized from the control signal Si output from the variable terminal.
So can be removed. In this case, it is naturally possible to use a variable capacitance or a variable reactance instead of the variable resistor VR ₃ .

The output of the variable terminal is fed back to the phase detector 11, but if the phase detector 11 is affected by voltage fluctuations at this time, it is preferable to use a limiter 5 as shown in FIG. .

FIG. 6 shows another embodiment of the current detection circuit 3.
The first feedback transformer _T31 in Fig. 5
Instead of , the first feedback resistor R ₃₁ is connected in series with the electrostrictive vibrator to form the first current detection circuit 31, and further, instead of the second feedback transformer T ₃₂ , a variable resistor R ₃₂ is connected as the detection reactance C. ₃ in series to constitute a second current detection circuit 32, and further,
The outputs of both detection circuits 31 and 32 are sent to a differential amplifier circuit 33.
A control signal Si is obtained from the output terminal of the differential amplifier circuit 33. Since the differential amplifier circuit 33 has the function of outputting the difference between two inputs, it is conceptually the same as superimposing the voltages So and So' in opposite phases as in the case shown in FIG. become. Therefore, if the value of the variable resistor R ₃₂ is set appropriately, the voltage So corresponding to the current Io flowing through the interelectrode reactance can be removed from the control signal Si, as in the case of the embodiment shown in FIG. It is possible. Therefore, the variable resistor R ₃₂ also serves as the voltage regulator 34.

FIG. 7 shows yet another embodiment of the current detection circuit 3. Although the principle is substantially the same as the case shown in FIG. 5, a differential amplifier circuit 33 is provided before the phase detector 11, and the outputs of two feedback transformers T ₃₁ T ₃₂ are input. A variable resistor VR ₃ as a voltage regulator 34 is connected in series between the output side of the feedback transformer T ₃₂ and the differential amplifier circuit 33.

When applying this invention to medical equipment such as dental scalers, a feedback transformer T ₃₁ T ₃₂ as shown in Figs. 5 and 7 is used to separate the electrostrictive vibrator P from the drive circuit. It is necessary to keep it isolated. That is, this is to prevent an accident in which a high driving voltage flows directly to the human body for some reason. In that sense, the embodiment shown in FIG. 6 can be said to be a more general embodiment.

The operating state of the electrostrictive vibrator drive device configured as described above can be well understood by looking at the waveform diagram shown in FIG.

FIG. 8a shows the output of the voltage controlled oscillator 13,
The output of the voltage controlled oscillator 13 is adjusted to an appropriate phase by a phase shifter 4 (FIG. 4b) and input to the amplifier 2. FIG. 8c shows the output of the amplifier section 2, which drives the electrostrictive vibrator P with this rectangular wave. Figure d shows the waveform of the drive current Ip of the electrostrictive vibrator P, and the waveform of the differential wave-like current Io flowing through the interelectrode reactance Co can be observed. This waveform appears as a substantially sinusoidal wave as f through the first detection circuit 31, but this waveform includes a voltage So corresponding to Io as shown by the broken line in g. e is a current I'o equivalent to Io flowing through the detection reactance _C3 , and this current appears from the second current detection circuit 32 as a voltage S'o as shown by the solid line g. Since So and So′ are adjusted to the same potential by the voltage regulator 34 and are superimposed with opposite phases, the control signal fed back to the phase detection circuit 11 contains an amount equivalent to the current Io flowing through the interelectrode reactance Co. This means that malfunctions can be eliminated. In addition, Fig. 8h shows limiter 5.
This is the input signal waveform to the phase detection circuit 11 after passing through the phase detection circuit 11.

As explained above, this device is configured so that the feedback control signal, which corresponds to the drive current, does not include the voltage component that corresponds to the current flowing through the reactance between the electrodes of the electrostrictive vibrator. It operates normally without any activation.

[Brief explanation of the drawing]

Figure 1 shows the characteristics of an electrostrictive vibrator, where a is an equivalent circuit, b is an admittance curve,
Fig. 2 is a block diagram showing an example of a conventional electrostrictive vibrator driving device, Fig. 3 is an example of a conventional current detection circuit in an electrostrictive vibrator driving device, and Fig. 4 is a block diagram showing an example of a conventional electrostrictive vibrator driving device. The block diagram of the current detection circuit, Figure 5, shows one example of this invention when applied to a dental ultrasonic scaler.
Embodiment FIG. 6 is another embodiment of this invention, FIG. 7 is a further embodiment of this invention, and FIG. 8 is a waveform diagram showing the operating state of the device of this invention. In the figure, 1... oscillation section, 2... amplification section, 3... current detection circuit, 31... first current detection circuit, 32...
...Second current detection circuit, 33...Differential amplifier circuit, 3
4... Voltage regulator, 5... Limiter, P... Electrostrictive vibrator, T ₃₁ ... First feedback transformer, T ₃₂ ... Second feedback transformer, Co...
...interelectrode reactance, _C3 ...detection reactance, _C31 , _C32 ...tuning capacitor, _R31 ...first feedback resistance, _R32 ...second feedback resistance, _VR3 ...variable resistor.

Claims (1)

[Claims for Utility Model Registration] (1) An electrostrictive device that includes an oscillation unit and an amplifier unit that drives an electrostrictive resonator, and uses a PLL to control the oscillation frequency by the phase difference between the electrostrictive resonator drive current and voltage. In the vibrator drive device, a current detection circuit for extracting a control signal corresponding to the drive current, a first current detection circuit for detecting a signal corresponding to a current flowing through the electrostrictive vibrator itself, and a first current detection circuit for detecting a signal corresponding to a current flowing through the electrostrictive vibrator itself; The output of a second current detection circuit that detects a signal corresponding to a current equivalent to the current flowing through the inter-electrode reactance of the vibrator is superimposed in opposite phase via a voltage regulator, and the above-mentioned inter-electrode reactance is detected from the control signal. An electrostrictive vibrator driving device characterized in that it removes a voltage corresponding to a current flowing through the oscillator. (2) Connect the first current detection circuit to the primary side of the first feedback transformer in series with the amplifier output and the electrostrictive resonator, and connect the electrostrictive resonator to the secondary side, which is the output side. The configuration includes a tuning circuit that tunes around the resonant frequency, and the second current detection circuit is connected to the amplifier output and the detection reactance, with the current flowing through the interelectrode reactance and the detection reactance for obtaining an equivalent current as the load. The utility model registration request for a configuration in which the primary side of a second feedback transformer is connected in series with the oscillator, and a tuning circuit that is tuned near the resonance frequency of the electrostrictive vibrator is provided on the secondary side, which is the output side. The electrostrictive vibrator drive device according to scope 1. (3) The first current detection circuit is configured by connecting a first feedback resistor in series with the electrostrictive vibrator and the output of the amplifier section, with both ends of the first feedback resistor serving as output terminals, and a second current detection circuit. A detection reactance for obtaining a current equivalent to the current flowing through the interelectrode reactance and a second feedback resistor are connected in series between the amplifier output terminals, and both ends of the second feedback resistor are used as output terminals. An electrostrictive vibrator drive device according to claim 1 of the utility model registration claim. (4) Use a variable resistor as a voltage regulator, and
The electrostrictive vibrator drive according to claim 1, in which the outputs of the current detection circuit and the second current detection circuit are connected in opposite phases to both terminals of the variable resistor, and a control signal is obtained from the variable terminals. Device. (5) Request for utility model registration in which the output of the first current detection circuit and the output of the second current detection circuit are input to a differential amplifier circuit, and the difference between the outputs of both detection circuits is obtained as a control signal from the output of the differential amplifier circuit. The electrostrictive vibrator drive device according to item 1. (6) The electrostrictive vibrator drive device according to claim 3, wherein the second feedback resistor is a variable resistor serving as a voltage regulator so that the output voltage of the second current detection circuit can be adjusted. .