HU207915B - Circuit arrangement for detecting resonant frequency of piezoresistiv converters, favourably for ultrasonic therapy apparatuses - Google Patents

Abstract

Field of the Invention The present invention relates to a circuit arrangement for automatically detecting the resonance frequency of piezoresistive transducers, preferably for ultrasound therapy devices. It is an object of the present invention to use a digital signal processing oscillator (3) output signal of a programmable frequency oscillator (3) as a signal to control the output signal of the power amplifier (2) at the piezo-resistive converter (1) at a resonant frequency, so that a power amplifier oscillator (3) is output so that the power amplifier (2) The frequency of the drive signal of the piezo-resistive converter (1) connected to the output is the same as the resonance frequency of the piezo-resistive converter (1). Figure 1 I_______I EN 207 915 B Description description: 4 pages (including 1 page figure)

Description

The present invention provides a circuit arrangement for finding the resonance frequency of piezoresistive transducers, preferably in ultrasound therapy devices.

The most critical point in ultrasound therapy equipment is to properly match the piezoresistive transducer to the power amplifier stage and to match the frequency of the signal at the output of the amplifier to the resonant frequency of the piezoresistive transducer. The better the efficiency of the piezoresistive transducer, the closer the output frequency of the high frequency power amplifier is to the resonant frequency of the converter itself. The biggest problem so far has been the fact that the manufacturing inaccuracy of piezoresistive converters is approx. 5%, while the power amplifier output signal frequency is max. It may deviate by 0.1% from the resonance frequency of the piezoresistive transducer. The ultrasound devices manufactured so far operated at a precisely set frequency, since it is extremely important to keep the frequency stable. However, this required tuning the piezoresistive transducers to the same frequency, which could be adjusted by the thickness of the tuning pad glued to the transducer. In extreme cases, this resulted in significant waste energy production, which occurred as the converters warmed up. However, in the case of therapeutic devices, this warming cannot be allowed, so a significant part of the converters are wasted, increasing the price of the converters and thus the device. The piezoresistive transducers - and the frequency change due to the aging of the adhesive - were not solved, nor could any replacement of the ultrasonic probes be possible, because the piezoresistive transducers were tuned to the same frequency, but the patient and the transducer must contact each other separately. set. Therefore, the devices differed slightly, which did not allow any change of the control heads without any adjustment of the devices. The following ultrasound therapy devices are designed in this way:

IMPULSAPHON-U, HM

ULTRON MY AUTOMATIC SONOPULS 646, ENRAF

ERBOSONAT, ERBE

The object of the present invention is to overcome these drawbacks by providing a circuit arrangement in which the piezoresistive converter always operates at its own resonant frequency, thereby preventing any wasteful power, and thus not maximizing the efficiency of the converter. The difference in resonance frequency resulting from the manufacturing inaccuracy and aging of the converters is not a malfunction because the power amplifier always operates at the operating point typical of the converter.

The invention thus provides a circuit arrangement for finding the resonance frequency of piezoresistive devices, preferably for ultrasound therapy devices, which comprises an oscillator, a power amplifier connected to its output, and a piezoresistive transducer connected to the output of the power amplifier, such that the power amplifier the oscillator is a programmable frequency oscillator whose programmable input is connected to the output of a data processing and control unit, the input of the data processing and control unit being connected to an output of the power amplifier control signal via an A / D converter.

The invention will now be described in detail with reference to FIG. Figure 1 is a block diagram of a circuit layout. The output of the power amplifier (6) controlling the piezoresistive converter (1) which controls the piezoresistive converter (2) is connected to the analog-to-digital converter input (5). The output of the analog-to-digital converter (5) is connected to the input of the data processing and control unit (4). The data processing and control unit (4) is connected to the programming input (7) of the programmable frequency oscillator (3). The programmable frequency oscillator (3) is connected to the input of the power amplifier (2).

The circuit layout works as follows:

In the case of ultrasound therapy devices, the signal (1) is most commonly applied to the piezoresistive converter by means of a transformer coupling. The piezoresistive converter (1) is connected to the secondary circuit of the transformer coupling. The primary side is controlled by the power amplifier (2), characterized in that it can control the signal to the piezoresistive converter (1) over a very wide power range. Thus, if the power amplifier (2) transmits the signal to the piezoresistive converter (1) by means of a transformer coupling, the current flowing through the primary side of the transformer as a function of frequency shows an extreme value of the resonant frequency of the piezoresistive converter (1). By converting the current to a voltage, the signal at the output of the control signal providing the extreme value (6) can be processed.

As described above, the frequency-dependent signal obtained from the power amplifier (2) obtained from the output of the control signal providing the extreme value (6) to the analog-to-digital converter (5) becomes dependent on the piezoresistive converter frequency (1). .

This data processing is performed by the data processing and control unit (4).

The data processing and control unit (4) is not detailed because there are several possibilities for its implementation.

Its tasks are as follows.

The programmable frequency oscillator (3) generates a signal to the programming input of the oscillator (7), which causes the programmable frequency oscillator (3) to generate a specific frequency. This frequency should be below the lowest value resulting from the manufacturing standard deviation of the piezoresistive converter (1). The signal generated by the programmable frequency oscillator (3) is amplified by the power amplifier (2) in the piezorescence (1).

EN 207 915 Β converter. The signal characteristic of this frequency is converted from the output of the control signal providing the extreme value (6) by means of the analog-to-digital converter (5). The now digital signal is stored in a memory circuit by the data processing and control unit (4), that is, it assigns a digital value to each frequency.

Thereafter, the data processing and control unit (4) generates a new signal which in turn generates a value higher than the former frequency at the output of the programmable frequency oscillator (3) and reassigns a digital value as described above. This process is repeated until the maximum value of the manufacturing standard deviation of the piezoresistive converter (1) is not exceeded by the generated frequency.

As a result of the process described above, the values stored in the memory of the data processing and control unit (4) characterize the frequency dependence of the piezoresistive converter (1).

The next task of the data processing and control unit (4) is to find the extreme value from the stored digital values, since this is the value where the piezoresistive converter (1) has the resonance frequency. Thus, depending on the design of the power amplifier (2), it is necessary to look for the minimum or maximum values stored in the memory of the data processing and control unit (4). The corresponding frequency value gives the resonance frequency of the piezo-resistive converter (1).

This value is again stored by the data processing and control unit (4) and now forces this frequency through the programmable frequency oscillator (3) to the power amplifier (2) and thus to the piezoresistive converter (1). The power amplifier (2), i.e. the magnitude of the signal to be applied to the piezoresistive converter (1), can now be controlled over a wide power range, since the frequency of the control signal does not change until the resonance frequency is determined again.

Thus, the greatest advantage of the circuit arrangement according to the invention is that the piezoresistive transducer always operates at its optimum operating point, thus avoiding harmful heating of the ultrasonic probes and the disposal of unused transducers. It allows any replacement of the ultrasonic probes to be carried out without any intervention on the devices.

Claims (2)

A circuit arrangement for finding the resonance frequency of piezoresistive transducers, preferably for ultrasound therapy devices, comprising an oscillator, a power amplifier connected to its output and a piezoresistive transducer connected to the output of a power amplifier, characterized in that 6), furthermore, the oscillator (3) is a programmable frequency oscillator whose programming input (7) is connected to the output of a data processing and control unit (4), the input of the data processing and control unit (4) via an A / D converter (5). the power amplifier (2) is connected to the output (6) of a control signal providing an extreme value. Circuit arrangement according to claim 1, characterized in that the data processing and control unit (4) is a unit for programming an oscillator (3) at the output of the oscillator (3) at the output of a digitalized extreme signal at its input at the resonance frequency of the piezoresistive converter (1). .