EP0712059B1 - Circuit for driving a piezo-electric vibrator - Google Patents

Circuit for driving a piezo-electric vibrator Download PDF

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Publication number
EP0712059B1
EP0712059B1 EP95117055A EP95117055A EP0712059B1 EP 0712059 B1 EP0712059 B1 EP 0712059B1 EP 95117055 A EP95117055 A EP 95117055A EP 95117055 A EP95117055 A EP 95117055A EP 0712059 B1 EP0712059 B1 EP 0712059B1
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EP
European Patent Office
Prior art keywords
vibrator
transistor
switching means
circuit
series connection
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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
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EP95117055A
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German (de)
French (fr)
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EP0712059A1 (en
Inventor
Soltermann Bertrand
Jabbour Saji
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Swatch Group Management Services AG
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SMH Management Services AG
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Publication of EP0712059A1 publication Critical patent/EP0712059A1/en
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B06GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06BMETHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/0207Driving circuits
    • B06B1/0223Driving circuits for generating signals continuous in time
    • B06B1/0238Driving circuits for generating signals continuous in time of a single frequency, e.g. a sine-wave
    • GPHYSICS
    • G04HOROLOGY
    • G04GELECTRONIC TIME-PIECES
    • G04G13/00Producing acoustic time signals
    • G04G13/02Producing acoustic time signals at preselected times, e.g. alarm clocks
    • G04G13/021Details

Definitions

  • the present invention relates to a control circuit a piezoelectric vibrator.
  • a vibrator is intended in particular to equip an electronic watch with a device acoustic alarm.
  • the noise level that can be reached with such a circuit is limited, which constitutes a disadvantage for applications to acoustic alarms. Indeed, the amount of energy that the coil can store is depending on its volume, i.e. its number of turns and the diameter of the wire which constitutes it. As we wish to incorporate the control circuit in a watch for example, we understand that this circuit should not be too big.
  • the object of the present invention is to provide a solution to these problems by presenting a circuit of control of a piezoelectric vibrator which is simple to construction, which is not expensive, and which allows reach a very high noise level, without the dimensions of this circuit become too large, for that it can be incorporated into a watch for example.
  • the solution recommended by the invention consists in supply a piezoelectric vibrator by two ways power supply, each including a coil. So the vibrator can be kept on continuously and he is most excited. Indeed, the vibrator is excited in both directions from its position of rest and so it has a larger displacement than the vibrator of the prior art. We therefore understand that, even if the efficiency of this circuit is reduced, the noise level will be higher compared to art circuits prior.
  • Figure 1 schematically shows a circuit of control of a piezoelectric vibrator according to the invention.
  • the circuit includes a voltage source power supply 1, for example a 3 volt source, supplying two electrical branches.
  • Each branch includes a series connection of a coil 2, 2 'and a diode 3, 3 ', this connection being connected by means a first terminal A, A 'at the high voltage level of the source 1.
  • A first terminal
  • A 'at the high voltage level of the source 1.
  • Each connection is also connected, via a second terminal B, B ', at switching means, for example transistors T1, T2.
  • Each transistor T1, T2 is connected by its emitter to the low voltage level from source 1 so that a current can flow through each branch when a transistor is in the conducting state.
  • the position of the serial connection and the transistor can be reversed.
  • the common terminal of transistors will be the terminal connected to the high voltage level instead of the terminal which is connected to the voltage level bottom of source 1 in the example given.
  • a piezoelectric vibrator 4 such that a piezoelectric membrane is connected between the two terminals B, B '.
  • Each transistor T1, T2 is controlled respectively by a periodic control signal S1 and S2 applied to its base.
  • Signal S2 is out of phase with the signal S1, for example 180 °, so that when the transistor T1 is put in conductive state by the control signal S1, the other transistor T2 is maintained in a state of blocking by control signal S2.
  • the control signals S1, S2 are for example pulse signals, each side of which changes the state of transistors T1 and T2 respectively.
  • transistor T2 When the transistor T2 is put in conductive state, transistor T1 is put in blocking state, and an electric current flows to through coil 2 'and diode 3' from the source of direct voltage 1 passing through transistor T2, the coil 2 'thus storing the corresponding energy.
  • the transistor T1 goes to the state driver thanks to its control signal S1
  • the transistor T2 therefore goes into the blocking state under the action its S2 control signal, out of phase with the signal S1.
  • the voltage induced in the coil 2 ' will then applied to the terminals of vibrator 4 to excite it.
  • a current flows through the coil 2 and the diode 3 from the DC voltage source 1 by the transistor T1, and coil 2 then stores energy corresponding.
  • Vibrator 4 is therefore kept energized continuously by the voltage induced either by the coil 2, or by the coil 2 '. If the frequency of changes of the voltage applied to vibrator 4 corresponds to the resonant frequency of the vibrator, it will be excited in a maximum way.
  • FIG. 2 schematically represents this excitation of the vibrator 4.
  • the voltage applied by the coil 2 energizes vibrator 4 in a first direction by relative to its rest position, for example, in the sense upwards indicated by the dotted line in the figure 2.
  • the voltage applied by the coil 2 ' will excite the vibrator 4 then in the other direction, for example down as also shown in Figure 2, at the time of change of state of transistors T1, T2 as was explained above.
  • the vibrator 4 is therefore attacked in alternating and vibrating in both directions, so comparable to the diaphragm of a speaker, and its displacement d is greater than if it were only excited in one direction.
  • control circuit according to the invention makes it possible to obtain a two-tone alarm, similar to a police alarm, by the use of control signals S1 and S2 which have frequencies slightly different.
  • control signals S1 and S2 which have frequencies slightly different.
  • the control circuit of the invention can then advantageously be used in a wristwatch with alarm device.
  • the circuit according to the invention allows achieve, with a watch battery, a noise level of around 110 dB at 10 cm, which obviously depends on the size of the piezoelectric vibrator and the cavity in which it is placed.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Oscillators With Electromechanical Resonators (AREA)
  • Apparatuses For Generation Of Mechanical Vibrations (AREA)
  • Electromechanical Clocks (AREA)
  • Electric Clocks (AREA)
  • Piezo-Electric Transducers For Audible Bands (AREA)
  • Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
  • Electronic Switches (AREA)

Abstract

A source of electrical potential (1) is connected to two parallel circuits. Each circuit comprises an inductor coil (2, 2'), a diode (3, 3') and a switching transistor (T1, T2). A piezoelectric buzzer (4) is connected between the two diode to transistor junctions (B, B'). The two switching transistors (T1, T2) are supplied with signals (S1, S2) which make them alternately conduct and block. When one transistor (T2) conducts and the other (T1) blocks, energy is stored in the corresponding inductor (2') which is then applied to the buzzer as the transistor switching is reversed by the signals (S1, S2).

Description

La présente invention concerne un circuit de commande d'un vibreur piézo-électrique. Un tel vibreur est destiné notamment à équiper une montre électronique à dispositif d'alarme acoustique.The present invention relates to a control circuit a piezoelectric vibrator. Such a vibrator is intended in particular to equip an electronic watch with a device acoustic alarm.

On connaít déjà des circuits de commande d'un vibreur piézo-électrique, par exemple grâce au brevet américain US-A-4 232 241. Ce document décrit un tel circuit qui comprend une branche comportant une bobine et une diode connectées en série, et un vibreur piézo-électrique connecté en parallèle avec la branche formant ainsi un circuit parallèle. Un côté de ce circuit parallèle est connecté à une source d'alimentation, tandis que l'autre coté de ce circuit parallèle est connecté à un transistor, connecté lui aussi à la source. Pendant que le transistor est à l'état conducteur, un courant circule à travers la branche et le transistor, et la bobine emmagasine l'énergie électromagnétique correspondante. Quand le transistor est mis à l'état de blocage, le courant circule dans le circuit parallèle, et la tension induite dans la bobine est alors appliquée aux bornes du vibreur afin d'exciter ce dernier.We already know control circuits of a vibrator piezoelectric, for example thanks to the American patent US-A-4 232 241. This document describes such a circuit which includes a branch with a coil and a diode connected in series, and a piezoelectric vibrator connected in parallel with the branch thus forming a parallel circuit. One side of this parallel circuit is connected to a power source, while the other side of this parallel circuit is connected to a transistor, also connected to the source. While the transistor is in the conductive state, a current flows through the branch and the transistor, and the coil stores the corresponding electromagnetic energy. When the transistor is put in blocking state, current flows in the parallel circuit, and the voltage induced in the coil is then applied across the vibrator so to excite the latter.

Toutefois, le niveau sonore pouvant être atteint avec un tel circuit est limité, ce qui constitue un désavantage pour les applications à des alarmes acoustiques. En effet, la quantité d'énergie que la bobine peut emmagasiner est fonction de son volume, c'est-à-dire de son nombre de spires et du diamètre du fil qui la constitue. Comme l'on souhaite incorporer le circuit de commande dans une montre par exemple, on comprend que ce circuit ne doit pas être trop grand.However, the noise level that can be reached with such a circuit is limited, which constitutes a disadvantage for applications to acoustic alarms. Indeed, the amount of energy that the coil can store is depending on its volume, i.e. its number of turns and the diameter of the wire which constitutes it. As we wish to incorporate the control circuit in a watch for example, we understand that this circuit should not be too big.

Le but de la présente invention est d'apporter une solution à ces problèmes en présentant un circuit de commande d'un vibreur piézo-électrique qui est simple de construction, qui ne coûte pas cher, et qui permet d'atteindre un niveau sonore très élevé, sans que les dimensions de ce circuit deviennent trop grandes, pour qu'il puisse être incorporé dans une montre par exemple.The object of the present invention is to provide a solution to these problems by presenting a circuit of control of a piezoelectric vibrator which is simple to construction, which is not expensive, and which allows reach a very high noise level, without the dimensions of this circuit become too large, for that it can be incorporated into a watch for example.

Ce but est atteint grâce aux caractéristiques particulières que présente le circuit de commande de la revendication 1.This goal is achieved thanks to the characteristics features of the control circuit of the claim 1.

La solution préconisée par l'invention consiste à alimenter un vibreur piézo-électrique par deux voies d'alimentation, chacune comprenant une bobine. Ainsi, le vibreur peut être maintenu sous tension continuellement et il est excité d'une façon maximale. En effet, le vibreur est excité dans les deux sens par rapport à sa position de repos et il a donc un déplacement plus grand que le vibreur de l'art antérieur. On comprend donc que, même si le rendement de ce circuit est diminué, le niveau sonore sera plus élevé par rapport aux circuits de l'art antérieur.The solution recommended by the invention consists in supply a piezoelectric vibrator by two ways power supply, each including a coil. So the vibrator can be kept on continuously and he is most excited. Indeed, the vibrator is excited in both directions from its position of rest and so it has a larger displacement than the vibrator of the prior art. We therefore understand that, even if the efficiency of this circuit is reduced, the noise level will be higher compared to art circuits prior.

D'autres caractéristiques et avantages de l'invention apparaítront mieux à la lecture de la description détaillée qui suit, et qui sera faite en se référant aux dessins annexés, donnés à titre d'exemple uniquement, dans lesquels :

  • la figure 1 représente schématiquement un circuit de commande d'un vibreur piézo-électrique selon l'invention, et
  • la figure 2 représente schématiquement l'excitation du vibreur piézo-électrique par le circuit de la figure 1.
Other characteristics and advantages of the invention will appear better on reading the detailed description which follows, and which will be made with reference to the appended drawings, given by way of example only, in which:
  • FIG. 1 schematically represents a control circuit for a piezoelectric vibrator according to the invention, and
  • FIG. 2 schematically represents the excitation of the piezoelectric vibrator by the circuit of FIG. 1.

La figure 1 représente schématiquement un circuit de commande d'un vibreur piézo-électrique selon l'invention.Figure 1 schematically shows a circuit of control of a piezoelectric vibrator according to the invention.

Le circuit comprend une source de tension d'alimentation 1, par exemple une source de 3 volts, alimentant deux branches électriques. Chaque branche comporte un raccordement en série d'une bobine 2, 2' et d'une diode 3, 3', ce raccordement étant connecté au moyen d'une première borne A, A' au niveau de tension haut de la source 1. Bien entendu, la position de la bobine 2 respectivement 2' et de la diode 3 respectivement 3', peut être inversée. Chaque raccordement est en outre connecté, par l'intermédiaire d'une deuxième borne B, B', à des moyens commutateurs, par exemple des transistors T1, T2. Chaque transistor T1, T2 est connecté par son émetteur au niveau de tension bas de la source 1 de sorte qu'un courant peut circuler dans chaque branche quand un transistor est à l'état conducteur. Bien entendu, ici aussi, la position du raccordement série et du transistor peut être inversée. Dans ce cas, la borne commune des transistors sera la borne reliée au niveau de tension haut au lieu de la borne qui est reliée au niveau de tension bas de la source 1 dans l'exemple donné. Un vibreur piézo-électrique 4 tel qu'une membrane piézo-électrique est connecté entre les deux bornes B, B'.The circuit includes a voltage source power supply 1, for example a 3 volt source, supplying two electrical branches. Each branch includes a series connection of a coil 2, 2 'and a diode 3, 3 ', this connection being connected by means a first terminal A, A 'at the high voltage level of the source 1. Of course, the position of the coil 2 respectively 2 'and diode 3 respectively 3', can be reversed. Each connection is also connected, via a second terminal B, B ', at switching means, for example transistors T1, T2. Each transistor T1, T2 is connected by its emitter to the low voltage level from source 1 so that a current can flow through each branch when a transistor is in the conducting state. Of course, here also, the position of the serial connection and the transistor can be reversed. In this case, the common terminal of transistors will be the terminal connected to the high voltage level instead of the terminal which is connected to the voltage level bottom of source 1 in the example given. A piezoelectric vibrator 4 such that a piezoelectric membrane is connected between the two terminals B, B '.

Chaque transistor T1, T2 est commandé respectivement par un signal périodique de commande S1 et S2 appliqué à sa base. Le signal S2 est déphasé par rapport au signal S1, par exemple de 180°, de sorte que quand le transistor T1 est mis en état conducteur par le signal de commande S1, l'autre transistor T2 est maintenu dans un état de blocage par le signal de commande S2.Each transistor T1, T2 is controlled respectively by a periodic control signal S1 and S2 applied to its base. Signal S2 is out of phase with the signal S1, for example 180 °, so that when the transistor T1 is put in conductive state by the control signal S1, the other transistor T2 is maintained in a state of blocking by control signal S2.

Les signaux de commande S1, S2 sont par exemple des signaux d'impulsions, dont chaque flanc change l'état des transistors T1 et T2 respectivement. Lorsque le transistor T2 est mis en état conducteur, le transistor T1 est mis en état de blocage, et un courant électrique circule à travers la bobine 2' et la diode 3' depuis la source de tension continue 1 en passant par le transistor T2, la bobine 2' emmagasinant ainsi l'énergie correspondante.The control signals S1, S2 are for example pulse signals, each side of which changes the state of transistors T1 and T2 respectively. When the transistor T2 is put in conductive state, transistor T1 is put in blocking state, and an electric current flows to through coil 2 'and diode 3' from the source of direct voltage 1 passing through transistor T2, the coil 2 'thus storing the corresponding energy.

Au moment où le transistor T1 passe à l'état conducteur grâce à son signal de commande S1, le transistor T2 passe donc à l'état de blocage sous l'action de son signal de commande S2, déphasé par rapport au signal S1. La tension induite dans la bobine 2' sera alors appliquée aux bornes du vibreur 4 pour l'exciter. D'autre part, un courant circule à travers la bobine 2 et la diode 3 depuis la source de tension continue 1 par le transistor T1, et la bobine 2 emmagasine alors l'énergie correspondante.At the moment when the transistor T1 goes to the state driver thanks to its control signal S1, the transistor T2 therefore goes into the blocking state under the action its S2 control signal, out of phase with the signal S1. The voltage induced in the coil 2 'will then applied to the terminals of vibrator 4 to excite it. Else part, a current flows through the coil 2 and the diode 3 from the DC voltage source 1 by the transistor T1, and coil 2 then stores energy corresponding.

Le vibreur 4 est donc maintenu sous tension continuellement par la tension induite soit par la bobine 2, soit par la bobine 2'. Si la fréquence des changements de la tension appliquée au vibreur 4 correspond à la fréquence de résonance du vibreur, celui-ci sera excité d'une façon maximale.Vibrator 4 is therefore kept energized continuously by the voltage induced either by the coil 2, or by the coil 2 '. If the frequency of changes of the voltage applied to vibrator 4 corresponds to the resonant frequency of the vibrator, it will be excited in a maximum way.

La figure 2 représente schématiquement cette excitation du vibreur 4. La tension appliquée par la bobine 2 excite le vibreur 4 dans un premier sens par rapport à sa position de repos, par exemple, dans le sens vers le haut indiqué par la ligne pointillée à la figure 2. La tension appliquée par la bobine 2' excitera le vibreur 4 alors dans l'autre sens, par exemple vers le bas comme également indiqué à la figure 2, au moment du changement d'état des transistors T1, T2 comme cela a été expliqué ci-dessus. Le vibreur 4 est donc attaqué en alternance et vibre dans les deux sens, de façon comparable à la membrane d'un haut parleur, et son déplacement d est plus grand que s'il n'était excité que dans un seul sens.Figure 2 schematically represents this excitation of the vibrator 4. The voltage applied by the coil 2 energizes vibrator 4 in a first direction by relative to its rest position, for example, in the sense upwards indicated by the dotted line in the figure 2. The voltage applied by the coil 2 'will excite the vibrator 4 then in the other direction, for example down as also shown in Figure 2, at the time of change of state of transistors T1, T2 as was explained above. The vibrator 4 is therefore attacked in alternating and vibrating in both directions, so comparable to the diaphragm of a speaker, and its displacement d is greater than if it were only excited in one direction.

Avantageusement, le circuit de commande selon l'invention permet d'obtenir une alarme à deux tons, semblable à une alarme de police, par l'utilisation des signaux de commande S1 et S2 qui ont des fréquences légèrement différentes. Bien entendu, il est également possible d'obtenir une alarme à quatre tons avec le circuit de l'invention par l'utilisation d'un balayage de fréquences des signaux de commande d'une façon connue de l'homme de métier.Advantageously, the control circuit according to the invention makes it possible to obtain a two-tone alarm, similar to a police alarm, by the use of control signals S1 and S2 which have frequencies slightly different. Of course, it is also possible to get a four tone alarm with the circuit of the invention by the use of a scan of frequencies of control signals in a known way of the skilled person.

Ainsi, on obtient un circuit pouvant atteindre un niveau sonore plus élevé que les circuits connus de l'art antérieur, sans que le circuit devienne beaucoup plus grand.Thus, we obtain a circuit that can reach a higher sound level than circuits known in the art previous, without the circuit becoming much more tall.

Le circuit de commande de l'invention peut alors avantageusement être utilisé dans une montre-bracelet à dispositif d'alarme. Le circuit selon l'invention permet d'atteindre, avec une pile horlogère, un niveau sonore de l'ordre de 110 dB à 10 cm, qui dépend évidemment de la grandeur du vibreur piézo-électrique et de la cavité dans laquelle il est placé.The control circuit of the invention can then advantageously be used in a wristwatch with alarm device. The circuit according to the invention allows achieve, with a watch battery, a noise level of around 110 dB at 10 cm, which obviously depends on the size of the piezoelectric vibrator and the cavity in which it is placed.

Claims (4)

  1. Control circuit for a piezoelectric vibrator comprising :
    a first branch comprising :
    first switching means (T1) arranged to be put into its blocking and into its conducting state following the reception of a first periodic control signal (S1), and
    a first series connection of a coil (2) and a diode (3), a first terminal (A) of said first series connection being connected to a voltage supply source (1) and a second terminal (B) of said first series connection being connected to said first switching means (T1), characterized in that it further comprises
    a second branch comprising :
    second switching means (T2) arranged to go into its blocking and into its conducting state following the reception of a second periodic control signal (S2), and
    a second series connection of a coil (2') and a diode (3'), a first terminal (A') of said second series connection being connected to said voltage supply source (1) and a second terminal (B') of said second series connection being connected to said second switching means (T2),
    said vibrator (4) being connected between said second terminals (B, B') in such a way that when said first switching means (T1) are in the blocking state, said second switching (T2) are in the conducting state and are electrically connected in series with said vibrator (4) and with said first series connection (2,3), while when said second switching means (T2) are in the blocking state, said first switching means (T1) are in the conducting state and are electrically connected in series with said vibrator (4) and with said second series connection (2',3').
  2. Circuit according to claim 1, characterized in that said switching means, each comprises a transistor each having a base to which one of said first and second control signals (S1,S2) is applied and each having a path collector-emitter connected to said second terminals (B, B').
  3. Circuit according to claim 1 or 2, characterized in that said second control signal (S2) is dephased by 180° with respect to said first control signal (S1).
  4. Watch having an acoustic alarm device, characterized in that it comprises a control circuit according to any of the claim 1, 2 or 3.
EP95117055A 1994-11-08 1995-10-30 Circuit for driving a piezo-electric vibrator Expired - Lifetime EP0712059B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH3333/94 1994-11-08
CH03333/94A CH687115B5 (en) 1994-11-08 1994-11-08 Control circuit for a piezoelectric vibrator.

Publications (2)

Publication Number Publication Date
EP0712059A1 EP0712059A1 (en) 1996-05-15
EP0712059B1 true EP0712059B1 (en) 1998-06-17

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EP95117055A Expired - Lifetime EP0712059B1 (en) 1994-11-08 1995-10-30 Circuit for driving a piezo-electric vibrator

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US (1) US5635788A (en)
EP (1) EP0712059B1 (en)
JP (1) JPH08233957A (en)
CN (1) CN1084001C (en)
AT (1) ATE167581T1 (en)
AU (1) AU694567B2 (en)
CH (1) CH687115B5 (en)
DE (1) DE69503021T2 (en)
HK (1) HK1012168A1 (en)
SG (1) SG45119A1 (en)
TW (1) TW371729B (en)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19644521A1 (en) * 1996-10-25 1998-04-30 Siemens Ag Method and device for controlling a capacitive actuator
CH691089A5 (en) * 1997-05-14 2001-04-12 Asulab Sa timepiece associated with a compass and a viewfinder.
DE19825210C2 (en) * 1998-04-23 2003-09-25 Gsg Elektronik Gmbh Circuit arrangement for dynamic control of ceramic solid state actuators
JP5865029B2 (en) * 2011-11-18 2016-02-17 矢崎エナジーシステム株式会社 Alarm
CN102836811A (en) * 2012-07-30 2012-12-26 西安思坦仪器股份有限公司 Stimulating method and stimulating circuit for piezoelectric ceramic transducer
JP6308788B2 (en) * 2013-03-27 2018-04-11 セイコーインスツル株式会社 Electronic device and impact detection method

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2279254A1 (en) * 1974-07-16 1976-02-13 Gaboriaud Paul High frequency thyristor generator for ultrasonic atomiser - has thyristor triggered from subharmonic of crystal oscillator
JPS5744398Y2 (en) 1977-05-26 1982-09-30
NL7805802A (en) * 1978-05-29 1979-12-03 Philips Nv DEVICE FOR CONTROLLING A PIEEZO ELECTRICAL POSITIONING ELEMENT.
NL7805804A (en) * 1978-05-29 1979-12-03 Philips Nv DEVICE FOR APPLYING A CONTROL VOLTAGE OVER A PIEEZO ELECTRICAL POSITIONING ELEMENT.
DE3230218A1 (en) * 1982-08-13 1984-02-23 Braun Ag, 6000 Frankfurt Electronic clock or clock radio with an alarm signal of differing loudness level
US4714935A (en) * 1983-05-18 1987-12-22 Canon Kabushiki Kaisha Ink-jet head driving circuit
JPH01264575A (en) * 1988-04-13 1989-10-20 Toyota Motor Corp Driver device for piezoelectric element

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Publication number Publication date
DE69503021D1 (en) 1998-07-23
US5635788A (en) 1997-06-03
CN1084001C (en) 2002-05-01
ATE167581T1 (en) 1998-07-15
AU694567B2 (en) 1998-07-23
EP0712059A1 (en) 1996-05-15
HK1012168A1 (en) 1999-07-23
AU3669795A (en) 1996-05-16
CH687115B5 (en) 1997-03-27
DE69503021T2 (en) 1999-02-11
JPH08233957A (en) 1996-09-13
TW371729B (en) 1999-10-11
SG45119A1 (en) 1998-01-16
CN1129821A (en) 1996-08-28
CH687115GA3 (en) 1996-09-30

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