EP0254237B1 - Method for phase controlled power- and frequency adjustement of an ultrasonic transducer and apparatus for application of the method - Google Patents

Method for phase controlled power- and frequency adjustement of an ultrasonic transducer and apparatus for application of the method Download PDF

Info

Publication number
EP0254237B1
EP0254237B1 EP87110425A EP87110425A EP0254237B1 EP 0254237 B1 EP0254237 B1 EP 0254237B1 EP 87110425 A EP87110425 A EP 87110425A EP 87110425 A EP87110425 A EP 87110425A EP 0254237 B1 EP0254237 B1 EP 0254237B1
Authority
EP
European Patent Office
Prior art keywords
transducer
phase
frequency
resonance frequency
voltage
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP87110425A
Other languages
German (de)
French (fr)
Other versions
EP0254237A3 (en
EP0254237A2 (en
Inventor
Herbert Gässler
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of EP0254237A2 publication Critical patent/EP0254237A2/en
Publication of EP0254237A3 publication Critical patent/EP0254237A3/en
Application granted granted Critical
Publication of EP0254237B1 publication Critical patent/EP0254237B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/0207—Driving circuits
    • B06B1/0223—Driving circuits for generating signals continuous in time
    • B06B1/0238—Driving circuits for generating signals continuous in time of a single frequency, e.g. a sine-wave
    • B06B1/0246—Driving circuits for generating signals continuous in time of a single frequency, e.g. a sine-wave with a feedback signal
    • B06B1/0253—Driving circuits for generating signals continuous in time of a single frequency, e.g. a sine-wave with a feedback signal taken directly from the generator circuit
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B2201/00—Indexing scheme associated with B06B1/0207 for details covered by B06B1/0207 but not provided for in any of its subgroups
    • B06B2201/50—Application to a particular transducer type
    • B06B2201/55—Piezoelectric transducer
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S323/00—Electricity: power supply or regulation systems
    • Y10S323/901—Starting circuits

Definitions

  • the invention relates to a method for phase-controlled power and frequency control of an ultrasound transducer, which is fed by the frequency-variable oscillator of a phase-locked loop with voltage pulses amplified by a driver stage, the frequency of the oscillator initially being varied by a wobbler to find the resonance of the ultrasound transducer, and the wobbler after locking the phase-locked loop to the resonant frequency of the converter is locked.
  • the invention further relates to a device for performing this method.
  • the swinging of the Transducer with great damping for example if there is a remaining drop of liquid on the converter or if non-atomized liquid flows along the converter even before it starts to vibrate. Then the available excitation energy is often not sufficient to allow the transducer to vibrate.
  • a general increase in the excitation power would have the disadvantage of uneconomical operation and would entail the risk of overloading the converter.
  • the vibration amplitude influenced by the transducer power also determines the droplet size, which is generally determined by the intended use, so that for this reason alone there are limits to the free variation of the excitation power.
  • care must also be taken to operate the ultrasonic transducer with a constant vibration amplitude in order to obtain a uniform droplet spectrum during liquid atomization.
  • the invention has for its object to improve a method of the type mentioned so that a swinging of the transducer is guaranteed even with high initial damping and a breakdown of the vibration is reliably avoided even with strong changes in damping.
  • This object is achieved according to the invention in that after the ultrasound transducer has started to vibrate A capacitive phase angle between the current and voltage in the converter is set and maintained in operation in the region of its series resonance frequency, so that the operating frequency of the oscillator is reduced compared to the series resonance frequency of the converter by the phase control of the phase-locked loop, with a change in the phase angle due to a mechanical load on the converter an increase in the operating frequency of the oscillator and thus leads to a shift towards the series resonance frequency of the converter.
  • the progress achieved by the invention essentially consists in the fact that, in contrast to the previously known method, the ultrasonic transducer is not operated in resonance, but rather just below its resonance frequency in a quasi-forced oscillation. Although this requires, due to the significantly higher converter impedance outside the resonance frequency, a higher converter voltage than would be necessary when operating in resonance, however, the excitation power in the converter can be significantly increased due to the strong change in impedance in the region of the resonance frequency, even through lower frequency changes.
  • the method is excellently suited to automatically supply the converter with the power required for optimal atomization for all operating cases. In particular, this also prevents the vibration from breaking off when the liquid throughput is too great.
  • the converter output also adjusts itself accordingly to different liquid densities and viscosities of the liquids to be atomized.
  • the capacitive phase angle between current and voltage in the converter is preferably in the range between -30 ° and -85 °.
  • phase steepness in the frequency range below the series resonance frequency is set by an additional impedance in the converter circuit so that the converter power, which rises above the falling converter impedance when the operating frequency is shifted toward the series resonance frequency, substantially compensates the damping of the converter .
  • the converter is supplied with the power required for this in each of its operating states.
  • the transducer Since the excitation of the transducer takes place in pulsed fashion due to the desired high efficiency, but the transducer would then continue to oscillate with its natural frequency, which is different from that, it is recommended that the transducer be supplied with two voltage pulses of opposite polarity per oscillation period, which are half the oscillation period in time are offset. This prevents the phase-locked loop, particularly when there is a large deviation between the natural resonance of the transducer and the excitation frequency, from disengaging.
  • the duration of the voltage pulses be less than a quarter of the period of the transducer vibration.
  • the duration of the two voltage pulses per oscillation period are compared with one another by integration and the duration of at least one of the two voltage pulses is regulated to ensure that the two voltage pulses are identical.
  • the wobbler provided for locating the resonance frequency starts up at a frequency below the resonance frequency of the converter.
  • the wobble process should extend over about 5 ⁇ 103 periods of the resonance frequency oscillation. It is also recommended that the wobble range be limited to a frequency range that has no further secondary resonances of the transducer, so that it is ensured that the phase-locked loop can only lock onto the series resonance frequency of the transducer.
  • the invention further relates to a device for carrying out the method, in particular for operating a piezoelectric ultrasound transducer, with an oscillator controlled by a phase-locked loop for generation, a driver stage for amplification and a transformer for transmitting the excitation pulses for the transducer, with this influencing the phase-locked loop required synchronization signal is tapped on a winding of the transformer, as well as with a wobbler, which initially varies the oscillator frequency to find the resonance frequency of the converter and is locked to the resonance frequency after the phase-locked loop has engaged.
  • the object on which the invention is based is achieved in that the phase detector of the phase-locked loop is preceded by an adjustable phase-shifting element, the phase rotation angle of which is set such that when the phase-locked loop is engaged a capacitive phase angle between current and voltage is maintained in the converter.
  • an additional impedance is expediently provided in the converter circuit, which reduces the frequency-dependent phase steepness below the series resonant frequency of the converter.
  • this additional impedance is formed by a capacitor connected in parallel with the converter.
  • a particularly expedient adaptation results when the capacitor forming the additional impedance and the other capacitances, which are not caused by the transducer, each amount to approximately one third of the low-capacitance measured by the transducer.
  • the inductance of the secondary winding of the transformer is then dimensioned according to the Thompson formula, taking into account all capacitances of the converter circuit and a frequency which is about a factor of 1.3 higher than the converter series resonant frequency.
  • the driver stage is expediently designed as a push-pull driver, so that two voltage pulses of opposite polyarity are fed to the converter during each oscillation period.
  • the driver stage Expediently upstream of a symmetry stage which integrates the two voltage pulses of the push-pull driver and compares them with one another by means of a comparator which, in the case of asymmetry, adjusts the operating point of one of the push-pull drivers.
  • the operating voltage of the driver stage can be variably adjustable by the wobbler and / or the latching signal of the phase locked loop.
  • the operating voltage is regulated by a clocked power supply, the clock frequency of which corresponds to the oscillator frequency of the phase locked loop. In this way, disturbances in the phase-locked loop otherwise caused by clocked power supplies can be largely avoided.
  • the circuit arrangement shown in FIG. 1 serves in particular to operate a piezoelectric ultrasound transducer 1.
  • an oscillator controlled by a conventional phase-locked loop 2 and not shown in detail in the drawing is provided, the output frequency of which is from a driver stage 3, 4 is amplified, which feeds the converter 1 via a transformer 5.
  • the synchronization signal required to influence the phase-locked loop 2 is tapped at a winding 6 of the transformer 5.
  • a wobbler 7 is provided, which initially varies the oscillator frequency in a forced manner in order to find the series resonance frequency of the converter 1 denoted by 1.1 in FIG.
  • An adjustable phase shifter 8 which carries out a phase shift of the synchronization signal, is connected upstream of the phase detector of the phase locked loop 2.
  • the phase angle is set so that when the phase-locked loop 2 is engaged, a capacitive phase angle between current and voltage in the converter.
  • the phase-locked loop 2 In order to be able to maintain this phase condition, the phase-locked loop 2 must reduce the excitation frequency, as can be seen from the mutually assigned phase and impedance curve in FIG. 2a, so that the converter is operated in a quasi-forced oscillation below its resonance frequency.
  • FIG. 2a even small changes in the phase position lead to a likewise relatively small change in frequency, which, however, then results in a relatively strong change in the converter impedance.
  • phase angle in the converter 1 undergoes a slight shift due to a stronger damping of the converter 1, as shown in FIG. 3a, this results in an increase in frequency, which results in a reduction in the converter impedance and thus an increase in the power supplied pulls itself.
  • I L the current through the secondary winding 5.1 of the transformer 5
  • I C the current through an additional impedance 9 to be described below
  • I W the converter current and with U the voltage at the converter 1.
  • an additional impedance 9 which is formed by a capacitor connected in parallel with the converter 1, is provided in the converter circuit and reduces the phase steepness of the converter 1.
  • Both the capacitor forming the additional impedance 9 and the other capacitances not caused by the transducer 1, such as the cable capacitance, are dimensioned such that they each amount to approximately one third of the low-frequency measured basic capacitance of the transducer 1.
  • the inductance of the secondary winding 5.1 of the transformer 5 is then determined according to the Thompson formula, taking into account all capacitances of the converter circuit and on the basis of a frequency which is about a factor of 1.3 higher than the converter series resonant frequency.
  • 2c shows the phase and impedance curve associated with one another when the electrical resonance frequency is shifted to lower frequencies due to an LC element connected in parallel with the converter, that is to say it lies below the mechanical resonance frequency which is unchanged in terms of position. In this case, care must be taken to ensure that the electrical resonance frequency is so far away from the mechanical resonance frequency that the capacitive branch in turn has the necessary steepness.
  • the driver stage 3, 4 is designed in particular as a push-pull driver, as a result of which the converter 1 receives an excitation pulse during each half period. This ensures that the transducer 1, which oscillates freely outside the excitation pulses and is otherwise operated in forced oscillation, cannot run from the excitation frequency to the extent that disengagement of the phase locked loop 2 would have to be feared. In order to obtain an undistorted form of oscillation of the transducer 1 which is also in view of a uniform one If the droplet spectrum is desirable, the driver stage 3, 4 is preceded by a balancing stage 10 which integrates the two voltage pulses of the push-pull driver and compares them with one another by means of a comparator. In the event of an asymmetry of the two voltage pulses, the operating point of one of the two push-pull drivers is adjusted accordingly by the balancing stage.
  • the operating voltage of the voltage regulator 11 for the driver stage 3, 4 can be variably adjusted by the wobbler 7 or possibly also by the latching signal of the phase locked loop 2, as is indicated in the drawing by the line 12.
  • the voltage regulator 11 can therefore initially provide its maximum output voltage, which is reduced to the intended operating value after the start of the oscillation.
  • the transducer 1 always starts to oscillate with maximum power, since the phase-locked loop 2 initially engages at the series resonance frequency of the transducer 1, where it has its minimum impedance and therefore consumes the maximum possible power. It is only after the oscillation has started that the frequency is lowered and the excitation power is reduced as a result of the rise in impedance caused by this.
  • the operating voltage can also be regulated by a clocked power supply, the clock frequency of which advantageously corresponds to the oscillator frequency of the phase-locked loop, so that faults in the control loop are avoided.
  • a separate voltage regulator 13 is provided for the phase locked loop itself.
  • an overload protection 14 is provided, with the aid of which the primary-side current through the transformer 5 is monitored and, if necessary, the modulation is limited.
  • the liquid supply to the converter 1 can be delayed via a liquid valve 16 actuated by a timing element 15.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Apparatuses For Generation Of Mechanical Vibrations (AREA)

Description

Die Erfindung betrifft ein Verfahren zur phasengesteuerten Leistungs- und Frequenzregelung eines Ultraschallwandlers, der von dem frequenzveränderlichen Oszillator eines Phasenregelkreises mit durch eine Treiberstufe verstärkten Spannungspulsen gespeist wird, wobei zunächst die Frequenz des Oszillators zum Auffinden der Resonanz des Ultraschallwandlers von einem Wobbler zwangsgeführt variiert und der Wobbler nach Einrasten des Phasenregelkreises auf die Resonanzfrequenz des Wandlers gesperrt wird. Weiter betrifft die Erfindung eine Vorrichtung zur Durchführung dieses Verfahrens.The invention relates to a method for phase-controlled power and frequency control of an ultrasound transducer, which is fed by the frequency-variable oscillator of a phase-locked loop with voltage pulses amplified by a driver stage, the frequency of the oscillator initially being varied by a wobbler to find the resonance of the ultrasound transducer, and the wobbler after locking the phase-locked loop to the resonant frequency of the converter is locked. The invention further relates to a device for performing this method.

Aus der DE-PS 34 01 735 ist bereits eine Vorrichtung bekannt, die eine Durchführung des oben genannten Verfahrens ermöglicht. Diese Vorrichtung hat sich in der Praxis bewährt, zumal sie zahlreiche der früher beim Betrieb von Ultraschallwandlern bestandenen Probleme und Schwierigkeiten beseitigt hat. Bekanntlich muß bei der Verwendung von Ultraschallwandlern zur Flüssigkeitszerstäubung oder zu Schweißzwecken der die Anregungsfrequenz für den Wandler liefernde Oszillator sich auf zahlreiche sich ändernde Betriebseigenschaften des piezoelektrischen oder magnetostriktiven Wandlers einstellen können. So können zunächst Änderungen der Resonanzfrequenz des Wandlers auftreten, die von der Last am Wandler, von der Temperatur, sowie dem Alterungsgrad der Piezokeramik bzw. des magnetostriktiven Materials abhängig sind. Ferner treten Impedanzänderungen des Wandlers auf, die eine Abhängigkeit von der Frequenz, der Last, der Amplitude sowie der Temperatur zeigen. Diese Impedanzänderungen können darüber hinaus von den spezifischen Eigenschaften des Wandlerwerkstoffes, insbes. der physikalischen Eigenschaften der Piezoscheiben verursacht sein. Schließlich teten auch noch Änderungen des Phasenwinkels zwischen Strom und Spannung um Wandler auf, die ebenfalls von der Anregungsfrequenz, der Last, der Amplitude sowie der Temperatur abhängig sind. Diese genannten Erscheinungen treten in der praktischen Anwendung gemeinsam auf, so daß sich der Oszillator auf die sich daraus ergebenden Änderungen der Betriebsbedingungen einstellen können muß. Bei der Vorrichtung aus der DE-PS 34 01 735 gelingt dies insbes. durch die Verwendung eines Phasenregelkreises bereits weitgehend. Schwierigkeiten bereitet jedoch nach wie vor das Anschwingen des Wandlers unter großer Bedämpfung, wenn sich also beispielsweise ein restlicher Flüssigkeitstropfen auf dem Wandler befindet oder bereits vor dem Anschwingen nicht zerstäubte Flüssigkeit an dem Wandler entlang strömt. Dann reicht nämlich häufig die zur Verfügung stehende Anregungsenergie nicht aus, um den Wandler anschwingen zu lassen. Eine generelle Erhöhung der Anregungsleistung hätte dagegen den Nachteil eines unwirtschaftlichen Betriebs und würde die Gefahr einer Überlastung des Wandlers in sich bergen. Im übrigen bestimmt die von der Wandlerleistung beeinflußte Schwingungsamplitude auch die Tröpfchengröße, die sich in der Regel aus dem Anwendungszweck bestimmt, so daß schon aus diesem Grund der freien Variation der Anregungsleistung Grenzen gesetzt sind. Schließlich ist auch auf einen Betrieb des Ultraschallwandlers mit konstanter Schwingungsamplitude zu achten, um bei der Flüssigkeitszerstäubung ein gleichmäßiges Tröpfchenspektrum zu erhalten.From DE-PS 34 01 735 a device is already known which enables the above-mentioned method to be carried out. This device has proven itself in practice, especially since it eliminates many of the problems and difficulties that previously existed in the operation of ultrasonic transducers Has. As is known, when using ultrasonic transducers for liquid atomization or for welding purposes, the oscillator providing the excitation frequency for the transducer must be able to adjust to numerous changing operating properties of the piezoelectric or magnetostrictive transducer. For example, changes in the resonant frequency of the transducer can first occur, which are dependent on the load on the transducer, on the temperature and on the degree of aging of the piezoceramic or the magnetostrictive material. Furthermore, impedance changes of the converter occur, which show a dependence on the frequency, the load, the amplitude and the temperature. These changes in impedance can also be caused by the specific properties of the transducer material, in particular the physical properties of the piezo disks. Finally, changes in the phase angle between current and voltage around converters also occurred, which are also dependent on the excitation frequency, the load, the amplitude and the temperature. These mentioned phenomena occur together in practical use, so that the oscillator must be able to adjust to the resulting changes in the operating conditions. In the device from DE-PS 34 01 735, this is largely achieved by using a phase-locked loop. However, the swinging of the Transducer with great damping, for example if there is a remaining drop of liquid on the converter or if non-atomized liquid flows along the converter even before it starts to vibrate. Then the available excitation energy is often not sufficient to allow the transducer to vibrate. A general increase in the excitation power, on the other hand, would have the disadvantage of uneconomical operation and would entail the risk of overloading the converter. In addition, the vibration amplitude influenced by the transducer power also determines the droplet size, which is generally determined by the intended use, so that for this reason alone there are limits to the free variation of the excitation power. Finally, care must also be taken to operate the ultrasonic transducer with a constant vibration amplitude in order to obtain a uniform droplet spectrum during liquid atomization.

Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren der eingangs genannten Art so zu verbessern, daß ein Anschwingen des Wandlers auch bei hoher Anfangsbedämpfung sicher gewährleistet ist und auch bei starken Bedämpfungsänderungen ein Abreißen der Schwingung sicher vermieden wird.The invention has for its object to improve a method of the type mentioned so that a swinging of the transducer is guaranteed even with high initial damping and a breakdown of the vibration is reliably avoided even with strong changes in damping.

Diese Aufgabe wird nach der Erfindung dadurch gelöst, daß nach dem Anschwingen des Ultraschallwandlers im Bereich seiner Serienresonanzfrequenz ein kapazitiver Phasenwinkel zwischen Strom und Spannung im Wandler eingestellt und betriebsmäßig aufrecht erhalten wird, so daß durch die Phasenregelung des Phasenregelkreises die Betriebsfrequenz des Oszillators gegenüber der Serienresonanzfrequenz des Wandlers verringert wird, wobei eine Änderung des Phasenwinkels infolge einer mechanischen Belastung des Wandlers zu einer Erhöhung der Betriebsfrequenz des Oszillators und damit zu einer Verschiebung in Richtung zur Serienresonanzfrequenz des Wandlers führt.This object is achieved according to the invention in that after the ultrasound transducer has started to vibrate A capacitive phase angle between the current and voltage in the converter is set and maintained in operation in the region of its series resonance frequency, so that the operating frequency of the oscillator is reduced compared to the series resonance frequency of the converter by the phase control of the phase-locked loop, with a change in the phase angle due to a mechanical load on the converter an increase in the operating frequency of the oscillator and thus leads to a shift towards the series resonance frequency of the converter.

Der durch die Erfindung erreichte Fortschritt besteht im wesentlichen darin, daß der Ultraschallwandler im Gegensatz zu dem bisher bekannten Verfahren nicht in Resonanz, sondern knapp unterhalb seiner Resonanzfrequenz in einer quasi-erzwungenen Schwingung betrieben wird. Dies bedingt zwar, wegen der deutlich höheren Wandlerimpedanz außerhalb der Resonanzfrequenz, eine höhere Wandlerspannung als sie bei Betrieb in Resonanz nötig wäre, dafür kann jedoch wegen der starken Impedanzänderung im Bereich der Resonanzfrequenz schon durch geringere Frequenzänderungen die Anregungsleistung im Wandler wesentlich erhöht werden. Da ferner in der Nähe der Resonanzfrequenz des Wandlers die Phasensteilheit der Phasenwinkeländerung zwischen Strom und Spannung im Wandler in Abhängigkeit von der Frequenz sehr groß ist, führen durch die Bedämpfung des Wandlers verursachte Phasenwinkeländerungen zu einer Frequenzänderung in Richtung zur Resonanzfrequenz, die dann die beschriebene Erhöhung der Wandlerleistung zur Folge hat. Auf diese Weise ist das Verfahren hervorragend geeignet, dem Wandler für alle Betriebsfälle automatisch die zum optimalen Zerstäuben notwendige Leistung zuzuführen. Dadurch wird insbes. auch ein Abreißen der Schwingung bei zu großem Flüssigkeitsdurchsatz verhindert, darüber hinaus stellt sich die Wandlerleistung auch verschiedenen Flüssigkeitsdichten und Viskositäten der zu zerstäubenden Flüssigkeiten entsprechend ein.The progress achieved by the invention essentially consists in the fact that, in contrast to the previously known method, the ultrasonic transducer is not operated in resonance, but rather just below its resonance frequency in a quasi-forced oscillation. Although this requires, due to the significantly higher converter impedance outside the resonance frequency, a higher converter voltage than would be necessary when operating in resonance, however, the excitation power in the converter can be significantly increased due to the strong change in impedance in the region of the resonance frequency, even through lower frequency changes. Furthermore, since the phase steepness of the phase angle change between current and voltage in the converter as a function of the frequency is very large in the vicinity of the resonant frequency of the converter phase angle changes caused by the damping of the converter lead to a frequency change in the direction of the resonance frequency, which then results in the described increase in converter power. In this way, the method is excellently suited to automatically supply the converter with the power required for optimal atomization for all operating cases. In particular, this also prevents the vibration from breaking off when the liquid throughput is too great. In addition, the converter output also adjusts itself accordingly to different liquid densities and viscosities of the liquids to be atomized.

Der kapazitive Phasenwinkel zwischen Strom und Spannung im Wandler liegt dabei vorzugsweise im Bereich zwischen -30° ind -85°.The capacitive phase angle between current and voltage in the converter is preferably in the range between -30 ° and -85 °.

Weiter empfiehlt es sich im Rahmen der Erfindung, daß die Phasensteilheit in dem unterhalb der Serienresonanzfrequenz liegenden Frequenzbereich durch eine Zusatzimpedanz im Wandlerkreis so eingestellt ist, daß die über die sinkende Wandlerimpedanz bei Verschiebung der Betriebsfrequenz hin zur Serienresonanzfrequenz ansteigende Wandlerleistung die Bedämpfung des Wandlers im wesentlichen kompensiert. Dadurch wird dem Wandler in jedem seiner Betriebszustände gerade etwa die hierfür erforderliche Leistung zugeführt.It is also recommended in the context of the invention that the phase steepness in the frequency range below the series resonance frequency is set by an additional impedance in the converter circuit so that the converter power, which rises above the falling converter impedance when the operating frequency is shifted toward the series resonance frequency, substantially compensates the damping of the converter . As a result, the converter is supplied with the power required for this in each of its operating states.

Da wegen des angestrebten hohen Wirkungsgrades die Anregung des Wandlers pulsförmig erfolgt, der Wandler jedoch anschließend mit seiner demgegenüber abweichenden Eigenfrequenz weiterschwingen würde, empfiehlt es sich, daß dem Wandler pro Schwingungsperiode zwei Spannungsimpulse jeweils entgegen gesetzter Polarität zugeführt werden, die zeitlich um die halbe Schwingungsdauer gegeneinander versetzt sind. Dadurch wird verhindert, daß die Phasenregelschleife insbes. bei größerer Abweichung zwischen Eigenresonanz des Wandlers und Anregungsfrequenz ausrastet.Since the excitation of the transducer takes place in pulsed fashion due to the desired high efficiency, but the transducer would then continue to oscillate with its natural frequency, which is different from that, it is recommended that the transducer be supplied with two voltage pulses of opposite polarity per oscillation period, which are half the oscillation period in time are offset. This prevents the phase-locked loop, particularly when there is a large deviation between the natural resonance of the transducer and the excitation frequency, from disengaging.

Um die Eigenschwingung des Wandlers andererseits nicht zu stark zu stören, empfiehlt es sich, daß die Dauer der Spannungspulse kleiner ist als ein Viertel der Periodendauer der Wandlerschwingung. Um eine unsymmetrische Schwingungsform zu vermeiden, empfiehlt es sich weiter, daß die Dauer der beiden Spannungspulse pro Schwingungsperiode durch Integration miteinander verglichen werden und die Dauer zumindest eines der beiden Spannungspulse auf Gleichheit der Beiden Spannungspulse geregelt wird.On the other hand, in order not to disturb the natural vibration of the transducer too much, it is recommended that the duration of the voltage pulses be less than a quarter of the period of the transducer vibration. In order to avoid an asymmetrical form of oscillation, it is further recommended that the duration of the two voltage pulses per oscillation period are compared with one another by integration and the duration of at least one of the two voltage pulses is regulated to ensure that the two voltage pulses are identical.

Um ein schnelles und sicheres Einrasten der Phasenregelschleife zu erreichen, ist es weiter zweckmäßig, wenn der zum Auffinden der Resonanzfrequenz vorgesehene Wobbler bei einer unterhalb der Resonanzfrequenz des Wandlers liegenden Frequenz anläuft. Um dabei das sichere Einrasten des Phasenregelkreises zu erreichen, sollte sich der Wobbelvorgang etwa über 5 · 10³ Periodendauern der Resonanzfrequenzschwingung erstrecken. Weiter empfiehlt es sich, daß der Wobbelbereich auf einen keine weiteren Nebenresonanzen des Wandlers aufweisenden Frequenzbereich beschränkt ist, so daß sichergestellt ist, daß der Phasenregelkreis allein auf die Serienresonanzfrequenz des Wandlers einrasten kann.In order to achieve a quick and secure locking of the phase-locked loop, it is also expedient if the wobbler provided for locating the resonance frequency starts up at a frequency below the resonance frequency of the converter. To ensure that the phase-locked loop snaps into place to achieve, the wobble process should extend over about 5 · 10³ periods of the resonance frequency oscillation. It is also recommended that the wobble range be limited to a frequency range that has no further secondary resonances of the transducer, so that it is ensured that the phase-locked loop can only lock onto the series resonance frequency of the transducer.

Weiter betrifft die Erfindung eine Vorrichtung zur Durchführung des Verfahrens, insbes. zum Betrieb eines piezoelektrischen Ultraschallwandlers, mit einem von einem Phasenregelkreis gesteuerten Oszillator zur Erzeugung, einer Treiberstufe zur Verstärkung und einem Transformator zur Übertragung der Anregungspulse für den Wandler, wobei das zur Beeinflussung des Phasenregelkreises benötigte Synchronisationssignal an einer Wicklung des Transformators abgegriffen wird, sowie mit einem Wobbler, der zunächst zum Auffinden der Resonanzfrequenz des Wandlers die Oszillatorfrequenz zwangsgeführt variiert und nach Einrasten des Phasenregelkreises auf die Resonanzfrequenz gesperrt wird.The invention further relates to a device for carrying out the method, in particular for operating a piezoelectric ultrasound transducer, with an oscillator controlled by a phase-locked loop for generation, a driver stage for amplification and a transformer for transmitting the excitation pulses for the transducer, with this influencing the phase-locked loop required synchronization signal is tapped on a winding of the transformer, as well as with a wobbler, which initially varies the oscillator frequency to find the resonance frequency of the converter and is locked to the resonance frequency after the phase-locked loop has engaged.

Vorrichtungsmäßig wird die der Erfindung zugrunde liegende Aufgabe dadurch gelöst, daß dem Phasendetektor des Phasenregelkreises ein einstellbares Phasendrehglied vorgeschaltet ist, dessen Phasendrehwinkel so eingestellt ist, daß bei eingerastetem Phasenregelkreis ein kapazitiver Phasenwinkel zwischen Strom und Spannung im Wandler aufrecht erhalten wird. Um bei einer Belastungserhöhung des Wandlers eine angepaßte Leistungserhöhung zu erreichen, ist im Wandlerkreis zweckmäßigerweise eine Zusatzimpedanz vorgesehen, die die frequenzabhängige Phasensteilheit unterhalb der Serienresonanzfrequenz des Wandlers verringert. Diese Zusatzimpedanz ist in bevorzugter Ausführungsform von einem dem Wandler parallel geschalteten Kondensator gebildet. Eine besonders zweckmäßige Anpassung ergibt sich dabei dann, wenn der die Zusatzimpedanz bildende Kondensator und die übrigen, nicht durch den Wandler bedingten Kapazitäten jeweils etwa ein Drittel der niederfrequent gemessenen Grundkapazität des Wandlers betragen. In weiter bevorzugter Ausführungsform der Erfindung ist dann die Induktivität der Sekundärwicklung des Transformators nach der Thompson-Formel unter Berücksichtigung aller Kapazitäten des Wandlerkreises und einer um etwa einen Faktor von 1,3 höheren Frequenz als der Wandlerserienresonanzfrequenz bemessen.In terms of the device, the object on which the invention is based is achieved in that the phase detector of the phase-locked loop is preceded by an adjustable phase-shifting element, the phase rotation angle of which is set such that when the phase-locked loop is engaged a capacitive phase angle between current and voltage is maintained in the converter. In order to achieve an adapted increase in power when the converter is subjected to an increase in load, an additional impedance is expediently provided in the converter circuit, which reduces the frequency-dependent phase steepness below the series resonant frequency of the converter. In a preferred embodiment, this additional impedance is formed by a capacitor connected in parallel with the converter. A particularly expedient adaptation results when the capacitor forming the additional impedance and the other capacitances, which are not caused by the transducer, each amount to approximately one third of the low-capacitance measured by the transducer. In a further preferred embodiment of the invention, the inductance of the secondary winding of the transformer is then dimensioned according to the Thompson formula, taking into account all capacitances of the converter circuit and a frequency which is about a factor of 1.3 higher than the converter series resonant frequency.

Um trotz der erzwungenen Schwingung eine gleichmäßige Anregung zu erreichen und ein Ausrasten des Phasenregelkreises zu verhindern, ist die Treiberstufe zweckmäßigerweise als Gegentakttreiber ausgebildet, so daß während jeder Schwingungsperiode dem Wandler jeweils zwei Spannungspulse entgegen gesetzter Polyarität zugeführt werden. Dabei ist der Treiberstufe zweckmäßigerweise eine Symmetriestufe vorgeschaltet, die die beiden Spannungspulse des Gegentakttreibers integriert und durch einen Komparator miteinander vergleicht, der bei Unsymmetrie den Arbeitspunkt eines der Gegentakttreiber verstellt.In order to achieve a uniform excitation despite the forced oscillation and to prevent the phase-locked loop from disengaging, the driver stage is expediently designed as a push-pull driver, so that two voltage pulses of opposite polyarity are fed to the converter during each oscillation period. Here is the driver stage Expediently upstream of a symmetry stage which integrates the two voltage pulses of the push-pull driver and compares them with one another by means of a comparator which, in the case of asymmetry, adjusts the operating point of one of the push-pull drivers.

Um eine noch weiterreichende Anpassung der Anregungsleistung zu erzielen, kann die Betriebsspannung der Treiberstufe durch den Wobbler und/oder das Rastsignal des Phasenregelkreises veränderlich einstellbar sein. Schließlich kann es sich auch zur Erzielung eines besonders günstigen Wirkungsgrades empfehlen, daß die Regelung der Betriebsspannung durch eine getaktete Stromversorgung erfolgt, wobei deren Taktfrequenz der Oszillatorfrequenz des Phasenregelkreises entspricht. Dadurch können sonst von getakteten Stromversorgungen hervorgerufene Störungen im Phasenregelkreis weitgehend vermieden werden.In order to achieve an even more extensive adaptation of the excitation power, the operating voltage of the driver stage can be variably adjustable by the wobbler and / or the latching signal of the phase locked loop. Finally, it can also be recommended to achieve a particularly favorable efficiency that the operating voltage is regulated by a clocked power supply, the clock frequency of which corresponds to the oscillator frequency of the phase locked loop. In this way, disturbances in the phase-locked loop otherwise caused by clocked power supplies can be largely avoided.

Im folgenden wird die Erfindung an einem in der Zeichnung dargestellten Ausführungsbeispiel näher erläutert; es zeigen:

Fig. 1
eine Vorrichtung nach der Erfindung in einem schematischen Blockschaltbild,
Fig. 2
den Frequenzgang und die Phasenlage eines Ultraschallwandlers im Resonanzbereich, wobei die Teilfigur 2b im wesentlichen der Teilfigur 2a entspricht und Fig. 2c die Dämpfung und Phasenlage bei dem Wandler parallelgeschaltetem LC-Glied zeigt,
Fig. 3
in den Teilfiguren a) und b) ein Vektordiagramm für einen Ultraschallwandler bei geringer bzw. bei hoher Belastung für den in Teilfigur c) dargestellten Sekundärkreis.
In the following the invention is explained in more detail using an exemplary embodiment shown in the drawing; show it:
Fig. 1
1 shows a device according to the invention in a schematic block diagram,
Fig. 2
the frequency response and the phase position of an ultrasound transducer in the resonance range, the partial figure 2b essentially corresponding to the partial figure 2a and FIG. 2c showing the damping and phase position in the converter connected LC element,
Fig. 3
in sub-figures a) and b) a vector diagram for an ultrasonic transducer at low or high loads for the secondary circuit shown in sub-figure c).

Die in Fig. 1 der Zeichnung dargestellte Schaltungsanordnung dient insbes. zum Betrieb eines piezoelektrischen Ultraschallwandlers 1. Zur Erzeugung der Anregungsfrequenz ist ein von einem üblichen Phasenregelkreis 2 gesteuerter, in der Zeichnung nicht im einzelnen dargestellter Oszillator vorgesehen, dessen Ausgangsfrequenz von einer Treiberstufe 3, 4 verstärkt wird, die über einen Transformator 5 den Wandler 1 speist. Das zur Beeinflussung des Phasenregelkreises 2 benötigte Synchronisationssignal wird an einer Wicklung 6 des Transformators 5 abgegriffen. Ferner ist ein Wobbler 7 vorgesehen, der zunächst zum Auffinden der in Fig. 2 mit 1.1 bezeichneten Serienresonanzfrequenz des Wandlers 1 die Oszillatorfrequenz zwangsgeführt variiert und nach Einrasten des Phasenregelkreises 2 auf die Resonanzfrequenz gesperrt wird.The circuit arrangement shown in FIG. 1 serves in particular to operate a piezoelectric ultrasound transducer 1. To generate the excitation frequency, an oscillator controlled by a conventional phase-locked loop 2 and not shown in detail in the drawing is provided, the output frequency of which is from a driver stage 3, 4 is amplified, which feeds the converter 1 via a transformer 5. The synchronization signal required to influence the phase-locked loop 2 is tapped at a winding 6 of the transformer 5. Furthermore, a wobbler 7 is provided, which initially varies the oscillator frequency in a forced manner in order to find the series resonance frequency of the converter 1 denoted by 1.1 in FIG.

Dem Phasendetektor des Phasenregelkreises 2 ist ein einstellbares Phasendrehglied 8 vorgeschaltet, das eine Phasenverschiebung des Synchronisationssignals vornimmt. Dabei ist dessen Phasenwinkel so eingestellt, daß bei eingerastetem Phasenregelkreis 2 ein kapazitiver Phasenwinkel zwischen Strom und Spannung im Wandler besteht. Um diese Phasenbedingung aufrecht erhalten zu können, muß der Phasenregelkreis 2, wie sich aus dem einander zugeordneten Phasen- und Impedanzverlauf in Fig.2a ergibt, die Anregungsfrequenz verringern, so daß der Wandler in einer quasi erzwungenen Schwingung unterhalb seiner Resonanzfrequenz betrieben wird. Wie sich dabei der Fig. 2a weiter entnehmen läßt, führen bereits geringe Veränderungen der Phasenlage zu einer ebenfalls verhältnismäßig geringen Frequenzänderung, die allerdings dann eine relativ starke Änderung der Wandlerimpedanz zur Folge hat. Wenn daher durch eine stärkere Bedämpfung des Wandlers 1, wie dies in Fig. 3a gezeigt ist, der Phasenwinkel im Wandler 1 eine geringfügige Verschiebung erfährt, so hat dies eine Frequenzerhöhung zur Folge, die eine Verringerung der Wandlerimpedanz und damit eine Erhöhung der zugeführten Leistung nach sich zieht. Im übringen ist in Fig. 3 mit IL der Strom durch die Sekundärwicklung 5.1 des Transformators 5, mit IC der Strom durch eine im folgenden noch zu beschreibende Zusatzimpedanz 9, mit IW der Wandlerstrom und mit U die Spannung am Wandler 1 bezeichnet. Der Phasenwinkel φ gibt die Phasenbeziehung zwischen dem Gesamtstrom Iges und der Spannung U an, wobei die sich bei Belastung des Wandlers 1 einstellende Phasenwinkeländerung Δφ = φ₁ - φ₂

Figure imgb0001
von dem Phasenregelkreis ausgewertet wird.An adjustable phase shifter 8, which carries out a phase shift of the synchronization signal, is connected upstream of the phase detector of the phase locked loop 2. The phase angle is set so that when the phase-locked loop 2 is engaged, a capacitive phase angle between current and voltage in the converter. In order to be able to maintain this phase condition, the phase-locked loop 2 must reduce the excitation frequency, as can be seen from the mutually assigned phase and impedance curve in FIG. 2a, so that the converter is operated in a quasi-forced oscillation below its resonance frequency. As can further be seen from FIG. 2a, even small changes in the phase position lead to a likewise relatively small change in frequency, which, however, then results in a relatively strong change in the converter impedance. Therefore, if the phase angle in the converter 1 undergoes a slight shift due to a stronger damping of the converter 1, as shown in FIG. 3a, this results in an increase in frequency, which results in a reduction in the converter impedance and thus an increase in the power supplied pulls itself. In Fig. 3 with I L the current through the secondary winding 5.1 of the transformer 5, with I C the current through an additional impedance 9 to be described below, with I W the converter current and with U the voltage at the converter 1. The phase angle φ indicates the phase relationship between the total current I tot and the voltage U, the phase angle change occurring when the converter 1 is loaded Δφ = φ₁ - φ₂
Figure imgb0001
 is evaluated by the phase locked loop.

Um bei einer Erhöhung der Wandlerbelastung die richtige Nachregelung der Leistung zu erreichen, ist es erforderlich, die Phasensteilheit im Bereich unterhalb der Serienresonanzfrequenz des Wandlers entsprechend einzustellen. Hierzu ist im Wandlerkreis eine von einem dem Wandler 1 parallel geschalteten Kondensator gebildete Zusatzimpedanz 9 vorgesehen, die die Phasensteilheit des Wandlers 1 verringert. Sowohl der die Zusatzimpedanz 9 bildende Kondensator als auch die übrigen, nicht durch den Wandler 1 bedingten Kapazitäten wie etwa auch die Kabelkapazität sind dabei so bemessen, daß sie jeweils etwa ein Drittel der niederfrequent gemessenen Grundkapazität des Wandlers 1 betragen. Die Induktivität der Sekundärwicklung 5.1 des Transformators 5 bestimmt sich dann nach der Thompson-Formel unter Berücksichtigung aller Kapazitäten des Wandlerkreises und unter Zugrundelegung einer um etwa einen Faktor von 1,3 höheren Frequenz als der Wandlerserienresonanzfrequenz.In order to achieve the correct readjustment of the power when the converter load is increased, it is necessary to adjust the phase steepness in the range below the series resonance frequency of the converter accordingly. For this purpose, an additional impedance 9, which is formed by a capacitor connected in parallel with the converter 1, is provided in the converter circuit and reduces the phase steepness of the converter 1. Both the capacitor forming the additional impedance 9 and the other capacitances not caused by the transducer 1, such as the cable capacitance, are dimensioned such that they each amount to approximately one third of the low-frequency measured basic capacitance of the transducer 1. The inductance of the secondary winding 5.1 of the transformer 5 is then determined according to the Thompson formula, taking into account all capacitances of the converter circuit and on the basis of a frequency which is about a factor of 1.3 higher than the converter series resonant frequency.

In Fig. 2c ist der einander zugeordnete Phasen- und Impedanzverlauf gezeigt, wenn die elektrische Resonanzfrequenz infolge eines zum Wandler parallel geschalteten LC-Gliedes zu tieferen Frequenzen hin verschoben ist, also unterhalb der - lagemäßig unveränderten - mechanischen Resonanzfrequenz zu liegen kommt. In diesem Fall muß dafür gesorgt werden, daß die elektrische von der mechanischen Resonanzfrequenz so weit entfernt liegt, daß der kapazitive Zweig wiederum die nötige Steilheit aufweist.2c shows the phase and impedance curve associated with one another when the electrical resonance frequency is shifted to lower frequencies due to an LC element connected in parallel with the converter, that is to say it lies below the mechanical resonance frequency which is unchanged in terms of position. In this case, care must be taken to ensure that the electrical resonance frequency is so far away from the mechanical resonance frequency that the capacitive branch in turn has the necessary steepness.

Die Treiberstufe 3, 4 ist im einzelnen als Gegentakttreiber ausgebildet, wodurch der Wandler 1 während jeder Halbperiode einen Anregungspuls erhält. Dadurch ist sichergestellt, daß der außerhalb der Anregungspulse frei schwingende, im übrigen in erzwungener Schwingung betriebene Wandler 1 nicht soweit aus der Anregungsfrequenz laufen kann, daß ein Ausrasten des Phasenregelkreises 2 zu befürchten wäre. Um eine möglichst unverzerrte Schwingungsform des Wandlers 1 zu erhalten, die auch im Hinblick auf ein gleichmäßiges Tröpfchenspektrum wünschenswert ist, ist der Treiberstufe 3, 4 eine Symmetrierstufe 10 vorgeschaltet, die die beiden Spannungspulse des Gegentakttreibers integriert und durch einen Komparator miteinander vergleicht. Bei einer Unsymmetrie der beiden Spannungspulse wird dann der Arbeitspunkt eines der beiden Gegentakttreiber durch die Symmetrierstufe entsprechend verstellt.The driver stage 3, 4 is designed in particular as a push-pull driver, as a result of which the converter 1 receives an excitation pulse during each half period. This ensures that the transducer 1, which oscillates freely outside the excitation pulses and is otherwise operated in forced oscillation, cannot run from the excitation frequency to the extent that disengagement of the phase locked loop 2 would have to be feared. In order to obtain an undistorted form of oscillation of the transducer 1 which is also in view of a uniform one If the droplet spectrum is desirable, the driver stage 3, 4 is preceded by a balancing stage 10 which integrates the two voltage pulses of the push-pull driver and compares them with one another by means of a comparator. In the event of an asymmetry of the two voltage pulses, the operating point of one of the two push-pull drivers is adjusted accordingly by the balancing stage.

Um eine weitere Leistungsregelung zu erreichen, ist die Betriebsspannung des Spannungsreglers 11 für die Treiberstufe 3, 4 durch den Wobbler 7 bzw. gegebenenfalls auch durch das Rastsignal des Phasenregelkreises 2 veränderlich einstellbar, wie dies in der Zeichnung durch die Leitung 12 angedeutet ist. Zum Anschwingen kann daher der Spannungsregler 11 zunächst seine maximale Ausgangsspannung zur Verfügung stellen, die nach erfolgtem Anschwingen auf den vorgesehenen Betriebswert reduziert wird. Aber auch ohne diese zusätzliche Spannungsregelung erfolgt das Anschwingen des Wandlers 1 stets mit maximaler Leistung, da der Phasenregelkreis 2 zunächst auf der Serienresonanzfrequenz des Wandlers 1 einrastet, wo dieser seine minimale Impedanz besitzt und daher die maximal mögliche Leistung aufnimmt. Erst nach deem Anschwingen erfolgt dann über die Regelung der Phasenlage ein Absenken der Frequenz und infolge des dadurch bedingten Impedanzanstiegs eine Verringerung der Anregungsleistung.In order to achieve a further power control, the operating voltage of the voltage regulator 11 for the driver stage 3, 4 can be variably adjusted by the wobbler 7 or possibly also by the latching signal of the phase locked loop 2, as is indicated in the drawing by the line 12. To start the voltage regulator 11 can therefore initially provide its maximum output voltage, which is reduced to the intended operating value after the start of the oscillation. But even without this additional voltage control, the transducer 1 always starts to oscillate with maximum power, since the phase-locked loop 2 initially engages at the series resonance frequency of the transducer 1, where it has its minimum impedance and therefore consumes the maximum possible power. It is only after the oscillation has started that the frequency is lowered and the excitation power is reduced as a result of the rise in impedance caused by this.

Die Regelung der Betriebsspannung kann im übrigen durch eine getaktete Stromversorgung erfolgen, wobei deren Taktfrequenz vorteilhafterweise der Oszillatorfrequenz des Phasenregelkreises entspricht, so daß Störungen im Regelkreis vermieden werden. Für den Phasenregelkreis selbst ist dabei ein eigener Spannungsregler 13 vorgesehen.The operating voltage can also be regulated by a clocked power supply, the clock frequency of which advantageously corresponds to the oscillator frequency of the phase-locked loop, so that faults in the control loop are avoided. A separate voltage regulator 13 is provided for the phase locked loop itself.

Um eine Überlastung der Treiberstufe 3, 4 und/oder des Wandlers 1 zu vermeiden, ist ein Überlastschutz 14 vorgesehen, mit dessen Hilfe der primärseitige Strom durch den Transformator 5 überwacht und gegebenenfalls die Aussteuerung begrenzt wird.In order to avoid overloading the driver stage 3, 4 and / or the converter 1, an overload protection 14 is provided, with the aid of which the primary-side current through the transformer 5 is monitored and, if necessary, the modulation is limited.

Zur weiteren Verbesserung des Anschwingverhaltens kann die Flüssigkeitszufuhr zum Wandler 1 über ein durch ein Zeitglied 15 betätigtes Flüssigkeitsventil 16 verzögert erfolgen.To further improve the start-up behavior, the liquid supply to the converter 1 can be delayed via a liquid valve 16 actuated by a timing element 15.

Claims (18)

  1. A process for the phase-controlled power and frequency regulation of an ultrasonic transducer which is fed by the variable-frequency oscillator of a phase-lock loop with voltage pulses which are amplified by a driver stage, wherein firstly the frequency of the oscillator is positively varied by a sweep generator for finding the resonance of the ultrasonic transducer and the sweep generator is blocked after latching of the phase-lock loop on to the resonance frequency of the transducer, characterised in that the ultrasonic transducer (1) is firstly excited for oscillation build-up at its series resonance frequency (1.1) and after the oscillation build-up a capacitive phase angle is set between current and voltage in the transducer (1) and operationally maintained so that the operating frequency of the oscillator is reduced relative to the series resonance frequency (1.1) of the transducer (1) by the phase regulation of the phase-lock loop (2), wherein a change in the phase angle, as a result of a mechanical loading on the transducer (1), results in an increase in the operating frequency of the oscillator and thus in a displacement towards the series resonance frequency (1.1) of the transducer.
  2. A process according to claim 1 characterised in that the capacitive phase angle between current and voltage in the transducer (1) is in the range of between -30° and -85°.
  3. A process according to claim 1 or claim 2 characterised in that the phase slope in the frequency range beneath the series resonance frequency (1.1) is so set by an additional impedance (9) in the transducer circuit that the transducer power which rises by way of the falling transducer impedance upon displacement of the operating frequency towards the series resonance frequency (1.1) substantially compensates for the attenuation of the transducer.
  4. A process according to claim 1 to 3 characterised in that in each oscillation period the transducer (1) is supplied with two voltage pulses of respective opposite polarities, which are displaced relative to each other in respect of time by half the oscillation duration.
  5. A process according to claim 1 to 4 characterised in that the duration of the voltage pulses is less than a quarter of the period duration of the transducer oscillation.
  6. A process according to claim 4 and 5 characterised in that the duration of the two voltage pulses for each oscillation period is compared together by integration and the duration of at least one of the two voltage pulses is regulated to equality of the two voltage pulses.
  7. A process according to claim 1 to 6 characterised in that the sweep generator (7) which is provided for finding the resonance frequency (1.1) starts at a frequency which is below the resonance frequency (1.1) of the transducer (1).
  8. A process according to claim 1 or claim 8 characterised in that the sweep operation extends approximately over 5 . 10³ period durations of the resonance frequency oscillation.
  9. A process according to claim 1 and 7 or 8 characterised in that the sweep range is restricted to a frequency range which does not have any further subordinate resonances of the transducer (1).
  10. Apparatus for carrying out the process according to claim 1 in particular for the operation of a piezoelectric ultrasonic transducer, having an oscillator controlled by a phase-lock loop (2) for producing the excitation pulses for the transducer (1), a driver stage (3, 4) for amplifying the excitation pulses, and a transformer (5) for transmitting the excitation pulses, wherein the synchronisation signal required for influencing the phase-lock loop (2) is taken off at a winding (6) of the transformer (5), and having a sweep generator (7) which initially positively varies the oscillator frequency for finding the resonance frequency (1.1) of the transducer (1) and which is blocked after latching of the phase-lock loop (2) on to the resonance frequency (1.1), characterised in that connected upstream of the phase detector of the phase-lock loop (2) is an adjustable phase rotation member (8) whose angle of phase rotation is so set that with the phase-lock loop (2) latched a capacitive phase angle is maintained between current and voltage in the transducer (1).
  11. Apparatus according to claim 10 characterised in that provided in the transducer circuit is an additional impedance (9) which reduces the frequency-dependent phase slope below the series resonance frequency (1.1) of the transducer (1).
  12. Apparatus according to claim 11 characterised in that the additional impedance (9) is formed by a capacitor which is connected in parallel with the transducer (1).
  13. Apparatus according to claim 12 characterised in that the capacitor forming the additional impedance (9) and the other capacitances which are not caused by the transducer (1) are respectively approximately one third of the basic capacitance, as measured at low frequency, of the transducer (1).
  14. Apparatus according to claims 10 to 13 characterised in that the inductance of the secondary winding (5.1) of the transformer (5) is rated in accordance with the Thomson formula having regard to all capacitances of the transducer circuit and a frequency which is higher by about a factor of 1.3, than the transducer series resonance frequency (1.1).
  15. Apparatus according to claims 10 to 14 characterised in that the driver stage (3,4) is in the form of a push-pull driver.
  16. Apparatus according to claim 15 characterised in that connected upstream of the driver stage (3, 4) is a symmetry stage (10) which integrates the two voltage pulses of the push-pull driver and compares them together by a comparator which in the event of asymmetry adjusts the working point of one of the push-pull drivers.
  17. Apparatus according to claim 10 to 16 characterised in that the operating voltage of the driver stage (3, 4) is variably adjustable by the sweep generator (7) and/or the latch signal of the phase-lock loop (2).
  18. Apparatus according to claim 17 characterised in that regulation of the operating voltage of the driver stage (3, 4) is effected by a clock-controlled current supply, the clock frequency thereof corresponding to the oscillator frequency of the phase-lock loop (2).
EP87110425A 1986-07-25 1987-07-18 Method for phase controlled power- and frequency adjustement of an ultrasonic transducer and apparatus for application of the method Expired - Lifetime EP0254237B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19863625149 DE3625149A1 (en) 1986-07-25 1986-07-25 METHOD FOR PHASE-CONTROLLED POWER AND FREQUENCY CONTROL OF AN ULTRASONIC TRANSDUCER, AND DEVICE FOR IMPLEMENTING THE METHOD
DE3625149 1986-07-25

Publications (3)

Publication Number Publication Date
EP0254237A2 EP0254237A2 (en) 1988-01-27
EP0254237A3 EP0254237A3 (en) 1989-07-05
EP0254237B1 true EP0254237B1 (en) 1994-09-21

Family

ID=6305952

Family Applications (1)

Application Number Title Priority Date Filing Date
EP87110425A Expired - Lifetime EP0254237B1 (en) 1986-07-25 1987-07-18 Method for phase controlled power- and frequency adjustement of an ultrasonic transducer and apparatus for application of the method

Country Status (3)

Country Link
US (1) US4849872A (en)
EP (1) EP0254237B1 (en)
DE (2) DE3625149A1 (en)

Families Citing this family (34)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4736130A (en) * 1987-01-09 1988-04-05 Puskas William L Multiparameter generator for ultrasonic transducers
EP0340470A1 (en) * 1988-05-06 1989-11-08 Satronic Ag Method and circuit for driving an ultrasonic transducer, and their use in atomizing a liquid
JP2537267B2 (en) * 1988-05-30 1996-09-25 キヤノン株式会社 Vibration type actuator device
JPH0628230Y2 (en) * 1989-05-30 1994-08-03 スタンレー電気株式会社 Vibration control device for ultrasonic transducer
DE3933300A1 (en) * 1989-10-05 1991-04-18 Eberspaecher J ULTRASONIC SPRAYER
US5113116A (en) * 1989-10-05 1992-05-12 Firma J. Eberspacher Circuit arrangement for accurately and effectively driving an ultrasonic transducer
JPH03161083A (en) * 1989-11-17 1991-07-11 Aisin Seiki Co Ltd Driving mechanism for piezoelectric vibrator and water drop removing device using same driving mechanism
DE3939419A1 (en) * 1989-11-29 1991-06-06 Licentia Gmbh MULTI-SURFACE SENSOR CONTROL FOR A RADIATOR SHAFT MOTOR
DE4013607A1 (en) * 1990-04-27 1991-10-31 Elektrotechnik Horst Kahl Kg Ultrasonic piezoelectric systems - are controlled by one single generator for all plastics or metal welding, drilling or polishing, and washing or cleaning applications
US5184605A (en) * 1991-01-31 1993-02-09 Excel Tech Ltd. Therapeutic ultrasound generator with radiation dose control
US5394047A (en) * 1993-02-12 1995-02-28 Ciba Corning Diagnostics Corp. Ultrasonic transducer control system
US5585546A (en) * 1994-10-31 1996-12-17 Hewlett-Packard Company Apparatus and methods for controlling sensitivity of transducers
US5900690A (en) * 1996-06-26 1999-05-04 Gipson; Lamar Heath Apparatus and method for controlling an ultrasonic transducer
US6498501B2 (en) 1998-09-15 2002-12-24 Vibro-Meter, S.A. Measuring circuit
EP1095712A1 (en) * 1999-10-26 2001-05-02 Telsonic Ag Method for regulating the power for ultrasound converter and generator
US6997935B2 (en) * 2001-11-20 2006-02-14 Advanced Medical Optics, Inc. Resonant converter tuning for maintaining substantially constant phaco handpiece power under increased load
US7723899B2 (en) 2004-02-03 2010-05-25 S.C. Johnson & Son, Inc. Active material and light emitting device
US7538473B2 (en) * 2004-02-03 2009-05-26 S.C. Johnson & Son, Inc. Drive circuits and methods for ultrasonic piezoelectric actuators
DE102007002315A1 (en) * 2007-01-16 2008-07-24 Health & Life Co., Ltd., Chung Ho Piezoelectric drive system for medical atomizer, has frequency generator for generating electric signal with frequency value and control interface is electrically connected with frequency generator
US8013640B1 (en) * 2008-06-19 2011-09-06 Supertex, Inc. Programmable ultrasound transmit beamformer integrated circuit and method
WO2011053353A1 (en) * 2009-10-26 2011-05-05 Los Alamos National Security, Llc Acoustic imaging of objects in optically opaque fluids
US9722671B2 (en) 2011-05-27 2017-08-01 uBeam Inc. Oscillator circuits for wireless power transfer
US9819399B2 (en) 2011-05-27 2017-11-14 uBeam Inc. Beam interaction control for wireless power transfer
US9831920B2 (en) 2011-05-27 2017-11-28 uBeam Inc. Motion prediction for wireless power transfer
US9094111B2 (en) 2011-05-27 2015-07-28 uBeam Inc. Receiver transducer for wireless power transfer
US10148131B2 (en) 2011-05-27 2018-12-04 uBeam Inc. Power density control for wireless power transfer
US9537322B2 (en) 2011-05-27 2017-01-03 uBeam Inc. Sub-apertures with interleaved transmit elements for wireless power transfer
US8648627B1 (en) 2012-08-16 2014-02-11 Supertex, Inc. Programmable ultrasound transmit beamformer integrated circuit and method
DE102012215993A1 (en) * 2012-09-10 2014-03-13 Weber Ultrasonics Gmbh Ultrasound system, ultrasound generator and method of operating such
DE102012215994A1 (en) * 2012-09-10 2014-03-13 Weber Ultrasonics Gmbh Method and circuit arrangement for determining a working range of an ultrasound oscillating structure
CN103769356A (en) * 2012-10-17 2014-05-07 成都龙冠科技实业有限公司 Novel ultrasonic transmitter
WO2015080901A1 (en) 2013-11-26 2015-06-04 Celleration Inc. Systems and methods for producing and delivering ultrasonic therapies for wound treatment and healing
KR101651731B1 (en) * 2014-07-11 2016-08-26 이완수 Portable ultrasonic beauty device
RU2572657C1 (en) * 2014-10-07 2016-01-20 Федеральное государственное бюджетное учреждение науки Институт машиноведения им. А.А. Благонравова Российской академии наук (ИМАШ РАН) Method of automatic setting of resonant modes of oscillations of vibration machine driven by induction motor

Family Cites Families (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3889166A (en) * 1974-01-15 1975-06-10 Quintron Inc Automatic frequency control for a sandwich transducer using voltage feedback
US3975650A (en) * 1975-01-30 1976-08-17 Payne Stephen C Ultrasonic generator drive circuit
US4141608A (en) * 1977-11-10 1979-02-27 L & R Manufacturing Company Circuitry for driving a non-linear transducer for ultrasonic cleaning
JPS5590195A (en) * 1978-12-28 1980-07-08 Ootake Seisakusho:Kk Ultrasonic oscillator with output meter
JPS5610792A (en) * 1979-07-06 1981-02-03 Taga Denki Kk Method and circuit for driving ultrasonic-wave converter
US4271371A (en) * 1979-09-26 1981-06-02 Kabushiki Kaisha Morita Seisakusho Driving system for an ultrasonic piezoelectric transducer
US4551690A (en) * 1982-03-18 1985-11-05 Branson Ultrasonics Corporation Automatic tuning circuit for use in an ultrasonic apparatus
JPS5916572A (en) * 1982-07-21 1984-01-27 多賀電気株式会社 Method of controlling drive frequency of ultrasonic converter drive
US4445063A (en) * 1982-07-26 1984-04-24 Solid State Systems, Corporation Energizing circuit for ultrasonic transducer
US4632311A (en) * 1982-12-20 1986-12-30 Matsushita Electric Industrial Co., Ltd. Atomizing apparatus employing a capacitive piezoelectric transducer
DE3317045A1 (en) * 1983-05-10 1984-11-15 Martin Walter Ultraschalltechnik GmbH, 7516 Karlsbad METHOD AND ARRANGEMENT FOR THE CONSTANT POWER DELIVERY OF ULTRASONIC CLEANING SYSTEMS
DE3331896A1 (en) * 1983-09-03 1985-03-21 Gerhard Prof. Dr.-Ing. 8012 Ottobrunn Flachenecker POWER GENERATOR FOR AN ULTRASONIC transducer
DE3401735C1 (en) * 1984-01-19 1985-05-02 Herbert 7909 Bollingen Gässler Device for operating a piezoelectric ultrasonic transducer

Also Published As

Publication number Publication date
US4849872A (en) 1989-07-18
EP0254237A3 (en) 1989-07-05
DE3625149A1 (en) 1988-02-04
DE3750560D1 (en) 1994-10-27
EP0254237A2 (en) 1988-01-27

Similar Documents

Publication Publication Date Title
EP0254237B1 (en) Method for phase controlled power- and frequency adjustement of an ultrasonic transducer and apparatus for application of the method
DE2905132C2 (en)
EP0848237B1 (en) Device monitoring a predetermined filling level in a container
DE69626455T2 (en) Converter with a piezoelectric converter
EP2591553B1 (en) Method for regulating the phase in an tuned circuit
DE69212983T2 (en) POWER SUPPLY FOR MULTIPOLAR MASS FILTERS
DE3331896C2 (en)
CH615337A5 (en)
CH668877A5 (en) DEVICE FOR OPERATING A PIEZOELECTRIC ULTRASONIC TRANSDUCER.
DE3789206T2 (en) Pendulum feedback detector.
EP0340470A1 (en) Method and circuit for driving an ultrasonic transducer, and their use in atomizing a liquid
DE2849782A1 (en) PIEZOELECTRIC SWINGER
CH678404A5 (en)
DE102007001148A1 (en) Phase locked loop for quick adjustment and related method
DE4100683A1 (en) CIRCUIT ARRANGEMENT FOR QUARTZ CRYSTAL MONITORS
EP0123277B1 (en) Method of driving an ultrasonic oscillator for an atomizing fluid
DE2916540A1 (en) ELECTRICAL CIRCUIT ARRANGEMENT FOR CONTROLLING A PIEZOELECTRIC CONVERTER
EP0303944A1 (en) Method and circuit for the excitation of an ultrasonic vibrator and their use in the atomisation of a liquid
DE102005030777B4 (en) Method and circuit arrangement for operating an ultrasonic vibrator
EP3513152B1 (en) Compensation of a phase shift of at least one electronic component of a vibronic sensor
DE962177C (en) Circuit arrangement for automatically stabilizing the frequency of a high-frequency oscillator with respect to a higher harmonic of a control oscillation
EP0421439B1 (en) Ultrasonic atomiser
EP0875742A1 (en) Device for determining/monitoring of a predefined liquid level in a container
DE2559199A1 (en) Drive and control for ultrasonic dental drill - has phase equilibration circuit to generate oscillator control signal
DE102005030764B4 (en) Method and device for switching on an ultrasonic vibration system

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A2

Designated state(s): BE CH DE FR GB IT LI NL SE

PUAL Search report despatched

Free format text: ORIGINAL CODE: 0009013

AK Designated contracting states

Kind code of ref document: A3

Designated state(s): BE CH DE FR GB IT LI NL SE

17P Request for examination filed

Effective date: 19891006

17Q First examination report despatched

Effective date: 19920713

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): BE CH DE FR GB IT LI NL SE

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: IT

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRE;WARNING: LAPSES OF ITALIAN PATENTS WITH EFFECTIVE DATE BEFORE 2007 MAY HAVE OCCURRED AT ANY TIME BEFORE 2007. THE CORRECT EFFECTIVE DATE MAY BE DIFFERENT FROM THE ONE RECORDED.SCRIBED TIME-LIMIT

Effective date: 19940921

Ref country code: NL

Effective date: 19940921

Ref country code: BE

Effective date: 19940921

REF Corresponds to:

Ref document number: 3750560

Country of ref document: DE

Date of ref document: 19941027

ET Fr: translation filed
GBT Gb: translation of ep patent filed (gb section 77(6)(a)/1977)

Effective date: 19941115

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SE

Effective date: 19941221

NLV1 Nl: lapsed or annulled due to failure to fulfill the requirements of art. 29p and 29m of the patents act
PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

REG Reference to a national code

Ref country code: CH

Ref legal event code: AEN

Free format text: DAS PATENT IST AUFGRUND DES WEITERBEHANDLUNGSANTRAGS VOM 29.02.1996 REAKTIVIERT WORDEN.

REG Reference to a national code

Ref country code: CH

Ref legal event code: NV

Representative=s name: ISLER & PEDRAZZINI AG PATENTANWAELTE

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: CH

Payment date: 19960611

Year of fee payment: 10

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LI

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19970731

Ref country code: CH

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19970731

REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 19980911

Year of fee payment: 12

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 19990421

Year of fee payment: 13

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 19990705

Year of fee payment: 13

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20000503

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20000718

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 20000718

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20010330

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST