JPH02265681A - Ultrasonic converter driving circuit - Google Patents

Abstract

PURPOSE:To always certainly lock in resonance frequency by simple circuit constitution by locking a drive signal in reference signal frequency in a surgical ultrasonic knife and detecting a rosonance point to transfer to rosonance point tracking control. CONSTITUTION:At the time of starting, a switch circuit 18 is connected to a reference signal generating circuit 19 and a reference signal is inputted to the PC 15 in a phased lock loop PLL 12 from a transmitter 21 and the voltage phase signal of the drive signal applied to the vibrator 11 of a handpiece 10 is fed back through a VCO 17 and a power amplifier 13 and the PLL 12 is operated so as to lock an output signal in the reference signal. When the current phase signal from a voltage current detection circuit 14 coincides with the voltage phase signal locked in the reference signal in phase, the resonance point state thereof is detected by a resonance point detection circuit 22 to change over the switch circuit 18 to transfer to resonance point tracking control due to the PLL 12. By this method, a drive signal can be always locked in resonance frequency.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an ultrasonic transducer drive circuit.

[Conventional technology]

Various devices using ultrasonic transducers have been proposed in the past, such as surgical ultrasonic scalpels, ultrasonic processing devices, and the like. Ultrasonic transducers used in such ultrasonic surgical scalpels and ultrasonic processing equipment are preferably driven at their resonant frequency in order to increase efficiency, but the resonant frequency varies depending on load conditions and temperature. There is a problem with doing so.

For this reason, conventionally, so-called phase locking techniques have been used, for example, to detect the phase difference between the drive voltage and drive current of the ultrasonic transducer or the vibration speed detection signal, and to control the drive frequency of the ultrasonic transducer based on the detected output. A system using a loop (PLL) type resonance point tracking circuit has been proposed.

[Problem to be solved by the invention]

However, according to experiments conducted by the present inventor, it has been found that the conventionally proposed PLL type drive circuits have serious problems as described below.

That is, the ultrasonic transducer includes a resistor R1 connected in series, as shown in FIG.
It consists of an inductor L1 capacitor C and a braking capacitance Cd connected in parallel to this series circuit, and in actual use, a correction inductor Ld is generally connected in parallel to cancel the braking capacitance cd. In this case, the frequency characteristic of the phase difference θ between the drive voltage and drive current of the vibrator 1 is the 12th
Impedance I Z l (
The Dm wavenumber characteristic is as shown in FIG. 12B. That is, the phase difference θ is the resonance point f1 and the sub-resonance points f+ before and after it.
, fz, and the impedance I21 is at the resonance point [,
, and is the maximum at the sub-resonance points f+ and fz.

In the conventional drive circuit, the PLL monitors the phase difference θ and controls the drive frequency to be r, so as is clear from FIGS. 12A and 12B, the PLL
The resonance point tracking range is only between the sub-resonance point f and f, and below f or above 12, loop feedback control does not work and tracking becomes impossible. For this reason, there is a problem in that it is not possible to lock onto the resonant frequency, especially at the start of oscillation.

One possible way to solve the above problem is to control the oscillation frequency range in the PLL using a limiter or the like. However, in this case, it is necessary to set the limiter with high precision, which makes the circuit configuration complicated and impractical.

In addition, as another method, as disclosed in Japanese Patent Laid-Open No. 56-10792, a voltage controlled oscillator (V
It is conceivable to sweep the oscillation frequency of the VCO by changing the control voltage of the VCO with a sweep circuit, stop the sweep when the resonance point is detected, and start the tracking operation by the PLL. However, in this case, the output of the sweep circuit is applied to the VCO during the tracking operation, resulting in an offset to the control voltage of the Vco, which poses a problem of adversely affecting the loop characteristics of the PLL.

Still another method, as disclosed in U.S. Pat. No. 4,754,186, is to
While oscillating at a certain frequency below f1 shown in B, P
It is conceivable to load a pulse during the feedback signal to the LL, thereby increasing the apparent frequency of the feedback signal and biasing and locking the oscillation frequency of the VCO toward the resonant frequency of the ultrasonic transducer. . However, in this case, the locking operation depends on the loop characteristics of the PLL, so it is extremely difficult to reliably lock the oscillation frequency of the VCO to the resonant frequency of the ultrasonic transducer, and the reliability of the locking operation is The problem is that it is extremely low.

This invention was made by focusing on the various problems mentioned above, and allows the driving frequency of an ultrasonic transducer using a PLL to be changed to various types of ultrasonic transducers using a simple circuit configuration without causing an offset. It is an object of the present invention to provide an ultrasonic transducer drive circuit that is appropriately configured so as to be able to reliably lock-in to the resonant frequency at all times.

[Means and operations for solving the problem] In order to achieve the above object, in the present invention, two feedback signals based on the drive signal of the ultrasonic transducer are supplied to the phase comparator of the phase-locked loop, and the phase In an ultrasonic transducer drive circuit that tracks and controls the ultrasonic transducer using a lock loop so that the drive signal frequency becomes the resonance frequency of the ultrasonic transducer, a reference signal whose frequency changes is generated. a reference signal generating means; a signal switching means for switching between the reference signal from the reference signal generating means and one of the two feedback signals and supplying the same to the phase comparator; a resonance point detection means for detecting whether the drive signal frequency of the ultrasonic transducer is substantially equal to the resonance frequency of the ultrasonic transducer; and a control means for controlling the signal switching means based on the output of the resonance point detection means. ,
By supplying the reference signal from the reference signal generating means and the other of the two feedback signals to the phase comparator,
The phase-locked loop is configured to be able to shift to resonance frequency tracking control using the two feedback signals when the drive signal frequency is approximately equal to the resonance frequency.

〔Example〕

FIG. 1 is a block diagram showing one embodiment of the present invention.

This embodiment is applied to an ultrasonic scalpel device using a Langevin type vibrator, and the Langevin type vibrator 11 provided in the hand piece 10 is connected to and the voltage phase θ9 applied to the vibrator 11 by the voltage/current detection circuit 14 based on the drive signal.
The current phase θ1 and impedance Z1 corresponding to vibration are detected.

The PLL 12 is configured to supply the output of the phase comparator (PC) 15 to the voltage controlled oscillator (■Co) 17 via the loop filter 16, and drives the resonator 11 with the output of the VCO 1'l) by the power amplifier 13. In addition, the PCl
Voltage/current detection circuit 1 is connected to the barrier pull input terminal (V) of 5.
4, and selectively supplies the current phase signal θ output from the voltage/current detection circuit 14 to the reference input terminal (R) via the switch circuit 1. do.

In addition, the reference signal generation circuit 19 is connected to the R input terminal of PCl5.
Reference signal θ9. is selectively supplied via the switch circuit 18. The reference signal generation circuit 19 includes a generator 20 and an oscillator 21, and the oscillator 21 outputs reference signals θ, , □ whose frequency changes based on the output of the generator 20.

On the other hand, the voltage phase signal θ9, current phase signal θ1, and impedance signal IZ1 output from the voltage/current detection circuit 14 are supplied to the resonance point detection circuit 22, where these voltage phase signal θ9, current phase signal θ1, and impedance signal Based on I71, it is detected whether the frequency of the drive signal applied to the vibrator 11 is approximately equal to the resonant frequency of the vibrator 11, and based on the output, the switch circuit 18
The switching operation between the current phase signal θ and the reference signal θrof is controlled.

FIGS. 2 to 5 show four examples of the switch circuit 18 shown in FIG. 1. Switch circuit 18 shown in FIG.
supplies the current phase signal θ1 and the reference signals θr, f to the 3-state buffers 25-1 and 25-2, respectively, and directly supplies the output of the resonance point detection circuit 22 to the control terminal of the 3-state buffer 25-1. , by supplying the output of the resonance point detection circuit 22 to the control terminal of the 3-state buffer 25-2 via the inverter 26, when the output of the resonance point detection circuit 22 is at a high (H) level, for example, the current phase When the signal θ, is at low (L) level, the reference signal θ, , □ is set to the PCL in the PLL 12.
The signal is supplied to the R input terminal of No. 5.

The switch circuit 18 shown in FIG.
D game) Resonance point detection circuit 2 is connected to the other input terminal of 27-1.
The output of the resonance point detection circuit 22 is directly supplied to the other input terminal of the AND gate 27-2.
For example, when the output of the resonance point detection circuit 22 is at H level, the current phase signal θ1 is supplied, and when the output of the resonance point detection circuit 22 is at L level, the reference signal θ, . It is designed to be supplied to the R input terminal of PCl5 inside.

The switch circuit 18 shown in FIG. 4 includes a current phase signal θ1 and a reference signal θ4. Each analog switch 30-
1 and 30-2, the output of the resonance point detection circuit 22 is directly supplied to the control terminal of the analog switch 30-1, and the output of the resonance point detection circuit 22 is directly supplied to the control terminal of the analog switch 30-2. When the output of the resonance point detection circuit 22 is at H level,
For example, when the current phase signal θ1 is at the L level, the reference signal θrmf is set to the R of PCl5 in the PLL 12.
It is designed to be supplied to the input terminal.

Further, the switch circuit 18 shown in FIG. 5 sends the current phase signal θ1 and the reference signal θraf to the relay contacts 31 and
-1 and 31-2, and also supplies the output of the resonance point detection circuit 22 to the relay 32.
When the output of No. 2 is at the H level, for example, the relay 32 is energized to generate the current phase signal θ, and when the output is at the L level, the relay 32 is deenergized to generate the reference signal θ. , respectively, PL
The signal is supplied to the P in L12 and the R input terminal of C15.

Next, the operation of this embodiment will be explained.

At startup, the switch circuit 18 connects the reference signal θ1 from the oscillator 21 to the R input terminal of PCl5 in the PLL 12.
．． The voltage phase signal θ7 of the drive signal applied to the vibrator 11 via the VCO 17 and the power amplifier 13 is connected to the input terminal (1) of the PCl5.
is fed back, so that the PLL 12 operates such that its output signal is locked to the reference signal θ,...f from the oscillator 21. That is, the drive signal frequency of the vibrator 11 operates so as to be equal to the frequency of the reference signal θref from the oscillator 21, and when the frequency of the reference signal θr, , changes based on the output of the generator 20, the vibration increases accordingly. The drive signal frequency of the child 11 will also change.

Figure 6 shows the reference signal θr, t and voltage phase signal θ at this time.
9 and the current phase signal θ. As is clear from FIG. 6, the reference signals θ,..., f are
For example, from the lower frequency side (f side) to the higher frequency side (rz side)
When the current phase signal θ1 is a feedback signal corresponding to the vibration of the vibrator 11, its phase matches that of the voltage phase signal θ9 at the resonance frequency f. Furthermore, since the voltage phase signal θ9 is locked to the reference signal θ, . . . by the PLL 12, the current phase signal θ1 also has the same phase as the reference signal θrot.

This resonance point state is detected by the resonance point detection circuit 22, and when it is detected, its output is set to, for example, an H level, and the switch circuit 18 is switched so that the current phase signal θ1 is inputted to the R input terminal of the PCl5. . As a result, P.L.
L12 enters a phase comparison operation between the voltage phase signal θ9 and the current phase signal θ1, and as a result, the drive signal frequency of the vibrator 11 is controlled so that the phases of the voltage phase signal θ9 and the current phase signal θ1 always match. , a resonance point tracking operation of the vibrator 11 is performed. Here, the reference signal θ, generated by the switch circuit 18. , to the current phase signal θ, if this is done instantaneously, the reference signal θrat and the current phase signal θ1
Since the phase of the input signal matches the PLL 12, the phase of the input signal does not change, so the lock state is effectively maintained without any adverse effect on the lock state of the PLL 12, and the PLL 12 can track the resonance point. It is possible to reliably shift to control.

Note that the resonance point detection circuit 22 detects the resonance point when the frequency change range of the reference signal θraf from the oscillator 21 is the sixth
In the figure, when it is within the range of f, to fz, only the phase difference θ between the voltage phase signal θ9 and the current phase signal θ1 is monitored, and the point where the phase difference θ is zero is detected as the resonance point. Bye. On the other hand, if the handpiece 10 has variations, such as by using a handpiece 10 with a different vibrator 11 or changing the tip of the handpiece 10, the resonance frequencies will vary over a wide range. Therefore, the reference signal θ, from the oscillator 21. , it is necessary to widen the frequency change range accordingly. In this case, similarly to the above, if the point where the phase difference θ between the voltage phase signal θ9 and the current phase signal θ1 is zero is simply detected as the resonance point,
As is clear from FIG. 6, in addition to the resonance frequency f, there is also a sub-resonance point f.

Since the phase difference θ is zero also in and f2, f or f
It malfunctions with z. In such a case, paying attention to the frequency characteristics of impedance +21 shown in FIGS. 12A and 12B, the impedance magnitude IZl at the resonance frequency f is the sub-resonance point f.

By taking advantage of the fact that the impedance is significantly lower than that at f2, the resonance point detection circuit 22
21 may be provided, and a point where IZ is equal to or less than a set value and the phase difference θ is zero may be detected as a resonance point.

As described above, according to this embodiment, even when using the vibrator 11 and handpiece 10 with different resonance frequencies, the PL
It is possible to reliably shift to resonance point tracking control using L12.

FIG. 7 is a block diagram showing the configuration of an example of an ultrasonic scalpel device including an ultrasonic transducer drive circuit according to the present invention.

Langevin type vibrator 3 provided on handpiece 35
6 is configured to drive via a matching transformer 38 based on the output of the PLL 37. The vibrator 36 is connected to the secondary side of a matching transformer 38, and a correction inductor 39 for canceling the braking capacity of the vibrator 36 is connected in parallel to the secondary side of the matching transformer 38.

The PLL 37 includes a phase comparator (PC) 40, a charge pump 41 that converts its digital output into an analog signal, a loop filter 42, and a voltage controlled oscillator (VCO) 4.
3, and the output of the charge pump 41 is supplied to the VCO 43 as a control voltage via the loop filter 42. The output of the VCO 43 is passed through the filter 44.
At the same time, the frequency is divided by the frequency dividing circuit 45 and the filter 4
4, thereby converting the rectangular wave drive signal output from the VCO 43 into a sine wave drive signal containing only the resonant frequency component of the vibrator 36, so as not to cause unnecessary heat generation within the vibrator 36. Make it.

In this example, a switched capacitor filter (SCF) whose cutoff frequency can be changed manually by an external clock is used as the filter 44.

In this way, if the SCF is used as the filter 44, V
Even if the oscillation frequency of CO43 changes, there is no variation in the size or phase rotation of the filter output waveform, and as a result, the influence on constant current control and PLL operation, which will be described later, is reduced, allowing ideal rectangular wave to sine wave conversion. It becomes possible to do so.

The output of the filter 44 is supplied to the primary side of the matching transformer 38 via a voltage control amplifier circuit (VCA) 46 whose amplification factor can be changed, a buffer amplifier 47, a switch circuit 48, and a power amplifier 49. In this way, the matching transformer 38 separates the circuit system of the vibrator 36 and its drive circuit system for electrical insulation, and also matches the power amplifier 49 with the vibrator 36 serving as a load. Make it.

The voltage applied to the vibrator 36 and the current flowing through the vibrator 36 via the power amplifier 49 are detected by a voltage/current detection circuit 50 provided on the primary side of the matching transformer 38, and these voltage detection signals and current detection signals are respectively detected. It is supplied to differential amplifiers 51-1 and 51-2 to remove common mode noise.

FIG. 8 shows a voltage/current detection circuit 50 and a differential amplifier 51.
-1.51-2 shows the configuration of an example. The voltage applied to the vibrator 36 is detected by voltage division using a resistor 52, and its output is supplied to a differential amplifier 51-1 to obtain a voltage detection signal (2). Further, the current flowing through the vibrator 36 is detected by a current sensor 53, and its output is supplied to a differential amplifier 51-2 to obtain a current detection signal I. In this way, by supplying the voltage and current detected by the voltage/current detection circuit 50 to the differential amplifier 51-151-2 to obtain the voltage detection signal (■) and the current detection signal (I), high voltage, It can effectively solve the problem of common mode noise when detecting a large current at a low voltage, and even if the positive and negative connections of the output of the power amplifier 49 are reversed, it is not an output type in which one of the outputs is grounded. Even if there is voltage.

Each of the current signals ■ and ■ can be detected stably.

In FIG. 7, the voltage detection signal obtained from the differential amplifier 51-1 is supplied to a comparator 54 and an absolute value detection circuit 55, respectively. Absolute value I of detection signal
Detect VI. Similarly, the differential amplifier 51-
The current detection signal obtained from 2 is supplied to a comparator 56 and an absolute value detection circuit 57, respectively, and the comparator 56 detects the current phase signal θ, and the absolute value detection circuit 57 detects the absolute value III of the current detection signal. do it like this.

The voltage phase signal θ9 obtained from the comparator 54 is supplied to the phase comparator 5, and is also supplied to the PC 40 that constitutes the PLL 37.
The current phase signal θ1 obtained from the comparator 56 is supplied to the phase comparator 58 and is also supplied to the reference input terminal R of the PC 40 via the switch circuit 59. Further, the absolute value +V+ of the voltage detection signal obtained from the absolute value detection circuit 55 is determined by the voltage comparator 6
0 and compares it with a predetermined set value, and its output is supplied to the phase detector 58. In this way, the phase detector 58
The output of voltage comparator 60, the voltage phase signal θ9 from comparator 54 and the current phase signal θ1 from comparator 56 at
Based on this, it is detected whether the frequency of the drive signal applied to the vibrator 36 is approximately equal to the resonance frequency of the vibrator 36, and based on the output, a current phase signal θ1 in the switch circuit 59 is determined, which will be described later. Reference signal θr from oscillator
In addition to controlling the switching operation with "off", the lighting of the light emitting diode 61 is controlled to display whether or not the PLL 37 has shifted to the resonance point tracking operation.

FIG. 9 shows the configuration of an example of the phase detector 58 and voltage comparator 60. The phase detector 58 includes three D-flip-flops (1)-FF) 62, 63 and 64, and an OR gate 65. The voltage phase signal θ9 obtained from the comparator 54 is supplied to the D input terminal of the D-FF 61, and the current phase signal θ9 obtained from the comparator 56 is
is supplied to the clock input terminal of the D-FF62. The Q output and page output of this D-FF62 are respectively supplied to the clock input terminal of D-FF63 and the clock input terminal of D-FF64, and the Q outputs of these D-FF63 and 64 are supplied to the OR gate 65 to switch Control signals for the circuit 59 and the light emitting diode 61 are obtained.

Note that the D input terminals of D-FF63 and 64 are connected to VC
Apply C. Further, the voltage comparator 60 is configured with an OP amplifier, and supplies the absolute value IVI of the voltage detection signal obtained from the absolute value detection circuit 55 to its inverting input terminal, and applies a set voltage VSEa to its non-inverting input terminal. and supplies its output to the clear terminals of D-FF 6.3 and 64. The output of the OR gate 65 is supplied to a control circuit 66 (see FIG. 7), and the control circuit 66 supplies a reset signal to the clear terminal of the D-FF 62.

In FIG. 7, the absolute value II+ of the current detection signal obtained from the absolute value detection circuit 57 is supplied to the inverting input terminal of the differential amplifier circuit 67. A setting signal from a current value setting circuit 68 is supplied to a non-inverting input terminal of this differential amplifier circuit 67,
Based on the output, the amplification factor of the VCA 46 is controlled via the limiter circuit 69 so that the vibrator 36 is always driven with a constant current corresponding to the setting signal. The current value setting circuit 68 is provided with a variable resistor 70 for setting the output amplitude and a variable resistor 71 for setting the low constant current drive, and these are selected based on the signal from the control circuit 66 and set at startup. The output of the variable resistor 71 for setting low constant current drive is supplied to the differential amplifier circuit 67, and the output of the variable resistor 70 for setting output amplitude is supplied to the differential amplifier circuit 67 in the resonance point tracking operation. Like this 5. The absolute value III of the current detection signal obtained from the absolute value detection circuit 57 and the setting signal from the current value setting circuit 68 are compared in the differential amplifier circuit 67, and the amplification factor of the VCA 46 is controlled based on the output thereof. By controlling the signal voltages input to the buffer amplifier 47 and the power amplifier 49, the vibrator 36 can always respond to the setting signal from the current value setting circuit 68 even when the impedance changes due to changes in the load of the handpiece 35. It can be driven with a constant current, and the amplitude of the handpiece 35 can be made constant.

A trigger output circuit 72 is connected to the control circuit 66 to generate a trigger signal under the control of the control circuit 66. This trigger signal is supplied to a generator 73 to generate a sawtooth wave, which is supplied to an oscillator 74 so that the oscillator 74 generates a reference signal θ, . . . whose frequency changes. This reference signal θ1. ．． 1, P that configures the PLL 37 via the switch circuit 59 under the control of the phase comparator 58 as described above.
Supplied to the R input terminal of O40. Further, the trigger signal from the trigger output circuit 72 is supplied to a counter 75 for counting, and when the count value exceeds a set value, the switch circuit 48 is turned off, and the hand piece 35 is turned off.
The light emitting diode 76 for probe check is detected as an abnormality.
so that it lights up. Note that this force counter 75 is reset by a reset signal from the control circuit 66.

On the other hand, the output of the loop filter 42 constituting the PLL 37 is also supplied to a low pass filter (LPF) 77 to remove spike-like noise contained in the control voltage of the VCO 43.

The output of this LPF 77 is supplied to a window comparator 78, which monitors the output frequency range of the VCO 43, and when it is out of a predetermined range, the control circuit 66
output a reset signal. That is, V.C.
The oscillation frequency of O43 changes depending on the control voltage from the loop filter 42, but when the PLL 37 is removed from the resonance point tracking control of the vibrator 36, the oscillation frequency of the VCO 43 is saturated at its highest or lowest oscillation frequency. Therefore, in order to detect this unlocked state, the control voltage of C043 is monitored by the window comparator 78. Here, the control voltage supplied to the VCO 43 becomes a signal that has been smoothed to some extent by the loop filter 42. For example, by using an edge trigger type for PO 20 of the PLL 37, the loop characteristics can be adjusted to the loop filter 42. If the speed is set to some extent by design, spike-like noise will leak into the control voltage supplied to the VCO 43 at the edge comparison portion of the two input signals of the PO 20. This spike-like noise adversely affects the operation of the window comparator 78, so in this example, the LPF
77 is inserted to remove spike-like noise.

The control circuit 66 also includes a 0N1
A foot switch 79 that controls 0FF is connected, and the signal from this foot switch 79 is input to the phase comparator 58 described above.
The operation of the above-mentioned parts is controlled based on the signal from the window comparator 78 and the reset signal from the window comparator 78, and the suction unit 80 that removes the tissue excised by the ultrasonic scalpel and the probe of the hand piece 35 are cooled. , to control the operation of the water supply unit 81 for washing away the excised site.

The operation of this ultrasonic scalpel device will be described below with reference to the flowchart shown in FIG.

When the foot switch 79 is in the OFF state, the switch circuit 4
8 is OFF, and the switch circuit 59 switches the output of the oscillator 74 to P.
It is connected to be supplied to the R input terminal of PO40 of LL37.

When the foot switch 79 is turned on, the control circuit 66 obtains a starting signal, resets the phase detector 58 and the counter 75, and also resets the current value setting circuit 6.
The low constant current drive setting variable resistor 71 of No. 8 is selected and its output is supplied to the differential amplifier circuit 67. Further, the switch circuit 48 is turned ON and the ζ trigger output circuit 72 is operated to generate a trigger signal from the trigger output circuit 72. As a result, the PLL 37 has an oscillator 74.
A reference signal θrat whose frequency changes according to the output of the generator 73 is supplied via the switch circuit 59, and as a result, the PLL 37 changes the drive signal frequency of the vibrator 36 to the reference signal θ4. scan so that it is locked.

Here, since the vibrator 36 is driven and controlled with a low constant current set by the variable resistor 71 of the current value setting circuit 68,
The voltage applied to the vibrator 36 is proportional to its impedance, and therefore the voltage applied to the vibrator 36 changes by scanning in a manner similar to the frequency characteristic of its impedance. This change in drive voltage is monitored by the voltage comparator 60 via the voltage/current detection circuit 50, the differential amplifier 51-1, and the absolute value detection circuit 55, and it is determined that the set voltage Vs! y (see FIG. 9) or less, that is, the reference signal θ1. An enable signal is output to the phase comparator 58 when the frequency of f becomes close to the resonance frequency of the handpiece 35 and the impedance becomes less than or equal to the set value. In the phase comparator 58, when the enable signal is output from the voltage comparator 60 and the phase difference between the voltage phase signal θ9 from the comparator 54 and the current phase signal θ1 from the comparator 56 becomes zero, The output becomes H level and is held, thereby switching the switch circuit 59 and supplying the current phase signal θ1 from the comparator 56 to the R input terminal of the PC 40, and the light emitting diode 61 lights up to track the resonance point. A message indicating that the operation has started is displayed. At the same time, based on the output of the phase comparator 5, the control circuit 6
6, the output amplitude setting variable resistor 70 of the current value setting circuit 68 is selected, and its output is supplied to the differential amplifier circuit 67. Therefore, from now on, the handpiece 35 is driven and controlled with a predetermined current set by the variable resistor 70 so that the phases of the voltage phase signal θ9 and the current phase signal θ1 always match. Furthermore, by shifting to the resonance point tracking operation, a drive signal is supplied from the control circuit 66 to the suction unit 80 and the water supply unit 81,
Each action is performed. The above operation is performed using the foot switch 79.
It is canceled by turning OFF.

On the other hand, when the resonance point is not detected by - times of scanning, the oscillation frequency of the VCO 43 is locked to the reference signal θ,...t from the oscillator 74 and rises or falls, and the oscillation frequency of the VCO 43 is locked to the reference signal θ,... This is detected and a reset signal is output to the control circuit 66. As a result, the control circuit 6
6 sends a signal to the trigger output circuit 72 to output the trigger again, and the above operation is repeated. The number of times the trigger signal is output from the trigger output circuit 72, that is, the number of times the drive signal frequency is scanned, is counted by a counter 75, and when it reaches a predetermined value, in this example, the foot switch 79 is turned ON once. If the resonance frequency cannot be locked in even after scanning the drive signal frequency 10 times, it is assumed that there is no resonance point of the handpiece 35 within the predetermined frequency range, and at that point the switch circuit 48 is activated by the output of the counter 75. OFI' occurs and the drive of the vibrator 36 is stopped, and the light emitting diode 76 lights up to indicate an abnormality in the hand piece 35. This effectively prevents the danger of the handpiece 35 continuing to drive in an abnormal state.

According to the above-described ultrasonic scalpel device, it is possible to reliably shift to the resonance point tracking operation, and even if the tracking operation is unlocked, it can be restarted, and it is also possible to detect abnormalities in the handpiece 35.

In addition, by combining a constant current drive circuit,
In addition to being able to perform constant amplitude operation, the frequency characteristics of impedance can be detected using a simple method, thereby making it possible to accurately and reliably detect the resonance point.

Furthermore, the voltage applied to the vibrator 36 and the vibrator 3
Since the current flowing through 6 is detected using a differential method,
In addition to being able to effectively remove common mode noise, the power amplifier 49
It is possible to effectively detect the desired voltage and current regardless of the output format, and this makes it possible to lift the circuitry around the power amplifier that generates high voltages from ground.
The leakage current to ground of the vibrator circuit, that is, the patient circuit, can be significantly reduced.

In the above ultrasonic scalpel device, the voltage applied to the vibrator 36 and the current flowing through the vibrator and 36 are detected on the primary side of the matching transformer 38; It is also possible to detect it on the secondary side. In addition, the oscillator 74
The frequency range of the reference signals θ, . can.

Furthermore, the present invention is not limited to ultrasonic scalpel devices, but can be effectively applied to drive circuits for ultrasonic transducers used in ultrasonic processing devices and other ultrasonic devices.

〔Effect of the invention〕

As described above, according to the present invention, the reference signal from the reference signal generating means is supplied to the phase comparator of the phase-locked loop to lock the drive signal frequency of the ultrasonic transducer to the reference signal frequency, thereby is detected and shifts to resonance point tracking control, so it always reliably locks in to the resonance frequency of many types of ultrasonic transducers with a simple circuit configuration without introducing undesirable offsets. be able to.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIGS. 2 to 5 are diagrams showing four examples of the switch circuit shown in FIG. 1, and FIG. 6 explains the operation of FIG. 1. FIG. 7 is a block diagram showing the configuration of an example of an ultrasonic scalpel device equipped with an ultrasonic transducer drive circuit according to the present invention, and FIG. 8 is a diagram showing the voltage/current detection circuit portion shown in FIG. 7. FIG. 9 is a diagram showing the configuration of an example of the phase detector and voltage comparator. FIG. 10 is a flowchart for explaining the operation of FIG. 7. FIGS. 11 and 12 A and B are diagrams for explaining the conventional technology. 10 - Handpiece 11 - - Vibrator 12 - Phase-locked loop (PLL) 13 -
- Power amplifier 14 - Voltage/current detection circuit 15 - Phase comparator (PC) 16 - Loop filter 17 - Voltage controlled oscillator (VCO) 18 - Switch circuit 19 - Reference signal generation circuit generator 1 - Oscillator resonance point detection circuit Figure 2 Applicant: Olympus Optical Industry Co., Ltd. Figure entrance--1-11--1-Event 9 Figure 9 Figure 10

Claims (1)

[Claims] 1. Two feedback signals based on the drive signal of the ultrasonic transducer are supplied to a phase comparator of a phase-locked loop, and the phase-locked loop controls the ultrasonic transducer according to its drive signal frequency. In an ultrasonic transducer drive circuit that performs tracking control so that the resonant frequency of the ultrasonic transducer becomes the resonant frequency of the ultrasonic transducer, there is provided a reference signal generating means for generating a reference signal whose frequency changes, and a reference signal from the reference signal generating means. signal switching means for switching between the signal and one of the two feedback signals and supplying the signal to the phase comparator; and based on the feedback signal, the driving signal frequency of the ultrasonic transducer is adjusted to match the resonance frequency of the ultrasonic transducer. Resonance point detection means for detecting whether or not they are substantially equal; and control means for controlling the signal switching means based on the output of the resonance point detection means, the reference signal from the reference signal generation means and the two By supplying the other of the feedback signals to the phase comparator, the phase-locked loop is switched to the second one at a frequency where the drive signal frequency is approximately equal to the resonant frequency.
An ultrasonic transducer drive circuit characterized in that the ultrasonic transducer drive circuit is configured to be able to shift to resonance frequency tracking control using two feedback signals.