EP0446195B1 - One-channel circuit for hearing aid - Google Patents

One-channel circuit for hearing aid Download PDF

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Publication number
EP0446195B1
EP0446195B1 EP91890015A EP91890015A EP0446195B1 EP 0446195 B1 EP0446195 B1 EP 0446195B1 EP 91890015 A EP91890015 A EP 91890015A EP 91890015 A EP91890015 A EP 91890015A EP 0446195 B1 EP0446195 B1 EP 0446195B1
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EP
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Prior art keywords
voltage
circuit
transistor
rectifier circuit
controlled
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EP91890015A
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German (de)
French (fr)
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EP0446195A2 (en
EP0446195A3 (en
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Zlatan Dipl. Ing. Dr. Ribic
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Viennatone GmbH
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Viennatone GmbH
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R25/00—Deaf-aid sets, i.e. electro-acoustic or electro-mechanical hearing aids; Electric tinnitus maskers providing an auditory perception
    • H04R25/50—Customised settings for obtaining desired overall acoustical characteristics
    • H04R25/502—Customised settings for obtaining desired overall acoustical characteristics using analog signal processing

Definitions

  • the invention relates to a single-channel circuit for a hearing aid for the hearing impaired with a preamplifier and a power amplifier, a microphone and a receiver, and a rectifier circuit, preferably constructed as a full-wave rectifier circuit, for generating a control voltage for a voltage-dependent amplifier or attenuator, which is connected downstream of the preamplifier is, a timing element and a voltage-controlled filter.
  • a circuit was known from AT-PS 371 306 in which the timing element is arranged in the signal channel in order to suppress the short-term signal peaks which occur due to the delay time of the automatic gain control.
  • Such circuits result in an amplification dependent on the signal level of the acoustic signals to be amplified, as a result of which overdriving can be avoided and the output signal of the hearing aid can be kept within a certain volume range, as a result of which uncomfortably large fluctuations in volume can be avoided.
  • the frequency response remains essentially the same over the entire amplification range, which means that speech intelligibility suffers from louder background noise.
  • a better adaptation of the frequency response of the amplification to the hearing loss of the user is achieved in the case of hearing aids by two-channel and multi-channel circuits, which usually have dynamic compression in the low-frequency channel and linear amplification in the high-frequency channel, the two signals being summed upstream of the output stage.
  • the compression in the bass channel is achieved with a voltage-controlled amplifier.
  • the aim of the invention is to avoid these disadvantages and to propose a circuit of the type mentioned at the outset which, with regard to speech intelligibility, enables a very favorable characteristic over the entire amplification range.
  • this is achieved in that the preamplifier, the voltage-controlled amplifier or attenuator, the voltage-controlled filter and the rectifier circuit are connected in series, the rectifier circuit being connected on the input side to the output of the voltage-controlled filter and on the output side via the timing element to the control input of the voltage-controlled filter.
  • Voltage-controlled filters are to be understood as circuit configurations that change the frequency response of a device depending on the level of an input signal in any way, apart from simple amplification or attenuation.
  • the voltage-controlled amplifier is also connected to the rectifier circuit via a separate timer.
  • the smallest possible battery is used for the power supply for reasons of a compact structure, so that only very low voltages can be used. For these reasons, it is necessary to use a rectifier circuit that can operate at low voltages.
  • the rectifier circuit is formed by two transistors, the main current paths of which are connected in series with resistors and these series circuits are connected in parallel with one another, the base of the one via a diode with the collector of the second transistor and the bases of the two transistors is connected to one another via at least one resistor and the collector of one transistor connected to the diode is connected to the base of this transistor via a further resistor and the control DC voltage at the collector of the transistor connected to the diode by its base can be tapped off.
  • the starting voltage of the diode has virtually no effect due to the amplification by means of the first transistor.
  • the voltage-controlled filter is formed by a three- or four-pole, which is followed by a transistor connected in bootstrap circuit, preferably a control transistor is provided, the main current path of which is connected in series with that of the transistor switched in bootstrap circuit and the base thereof is connected to the rectifier circuit supplying the control voltage.
  • the voltage-controlled filter is formed by two different three-pole, but preferably four-pole, which are followed by transistors connected in bootstrap circuit, at least one of whose bases is connected to the rectifier circuit via a timing element and the preamplifier, if appropriate is connected to the inputs of the three or four poles via the center connection of a potentiometer.
  • the voltage-controlled filter is controlled via a potentiometer circuit to which a signal voltage taken from the preamplifier and the control DC voltage coming from the rectifier circuit is applied, the signal voltage taken from the preamplifier damping the filter at high signal levels .
  • FIG. 1 The basic structure of a hearing aid according to the invention is shown in FIG. 1.
  • a microphone 1 is followed by a preamplifier 2 in the usual way.
  • This is connected on the output side to a voltage-controlled amplifier 3, which also has a gain factor ⁇ 1 and can therefore act as an attenuator.
  • This voltage controlled amplifier 3, which is connected by a bipolar transistor or e.g. can be formed by an operating point-controlled amplifier and is used for automatic volume control, a voltage-controlled filter 4 is connected downstream, which enables automatic frequency response control.
  • This is preferably designed as an automatic depth reduction when loud signals occur, which makes it easier to hear and understand speech in a noisy environment.
  • the signal processed by the filter 4 reaches the power amplifier 5, to which a receiver 6 is switched on. Furthermore, a rectifier circuit 7 is also provided, which rectifies a signal taken between the voltage-controlled filter 4 and the power amplifier 5, or between the voltage-controlled amplifier 3 and the voltage-controlled filter 5, and supplies it as a control voltage to the voltage-controlled amplifier 3 and the voltage-controlled filter 5. It depends on the installation location of the volume control, not shown, whether the control is designed as an input- or output-controlled control.
  • the rectifier circuit 7 is designed as a full-wave rectifier and will be explained in more detail later with reference to FIGS. 4 and 5.
  • the voltage-controlled filter 4 can be constructed, for example, according to FIG. 2, a four-pole A being provided, which can be constructed, for example, as an R / C filter and which is followed by a transistor 9 in bootstrap circuit, the collector of which is connected to the supply voltage V CC and whose base and emitter are connected to the four-pin A, which can be designed as a high-low or bandpass or as a bandstop.
  • the emitter resistor R e is connected in series with a control transistor 8, the emitter of which is grounded and the base of which is supplied with a control voltage V c taken from the rectifier circuit 7. If this control voltage has a high potential, the transistor 8 is fully conductive and acts on the output signal of the four-pole A like an emitter follower.
  • the transistor 8 blocks and the input signal of the four-pole A essentially goes unchanged directly to the output O, for example via the capacitors C4, C8 and the resistor R5, as can be seen from FIG. 4 .
  • FIG. 3 Another embodiment of a voltage-controlled filter 4 is shown in FIG. 3.
  • Two four-pole A and B are provided, which are coupled to two transistors 10 and 11 connected in parallel with a common emitter resistor R e .
  • the two four poles A and B are expediently designed as a high-pass or low-pass filter.
  • Control voltages V c1 , V c2 which are derived from the rectifier circuit 7 and can have a different height, are connected via resistors to the outputs of the four-pole A and B, or to the bases of the transistors 10, 11.
  • the two control voltages can be taken, for example, from a voltage divider circuit connected to the rectifier circuit 7 and not shown in FIG. 3.
  • the input signal I can be divided over the two four-pole terminals A and B of the filter via the potentiometer Ri, as a result of which a fixed presetting can be selected.
  • both four-pole circuits A and B function simultaneously and a change in the common control voltage enables the setting of all intermediate functions.
  • Fig. 4 shows an embodiment of a hearing aid according to the invention.
  • the transistor T1 acts as a preamplifier 2, the base of which is connected to the microphone 1 via the capacitor C2.
  • the transistor T1 is connected in the usual way with the resistors R3, R1.
  • the R / C link R2 and C1 is used for screening.
  • the transistor T2 in conjunction with the resistor R4 and the coupling capacitor C3, serves as a voltage-controlled attenuator 3 for an automatic gain control.
  • the capacitors C4 to C7 in conjunction with the resistors R5 to R8 form a four-pole higher order, which in conjunction with the transistor T3, the emitter resistor R e and the control transistor T4 forms a voltage-controlled filter 4, the transistors T3 and T4 being the transistors 8 and 9 in Fig. 2 correspond.
  • the signal reaches resistor R5 and capacitor C8, essentially unchanged, via capacitor C4 to amplifying transistor T5, which has the resistor R11, the capacitor C9, the resistor R13 and the transistor T6 in a known manner forms an output stage to which the receiver 6 is connected.
  • the transistor T3 works as an emitter follower and the four-pole A forms a fourth-order high-pass filter in a bootstrap circuit.
  • the diode D blocks and the signal is transmitted directly via the resistor R20.
  • the ratio of the resistors R19 and R17 determines the gain.
  • the symmetry in the full-wave rectification of the input signal is ensured by the appropriate dimensioning of the resistors R18 to R20.
  • a control voltage that decreases with an increasing signal occurs at the base of transistor T8.
  • a reversely polarized diode D it would also be possible to tap a control voltage which increases as the signal increases.
  • the transistor T8 acts as a control voltage amplifier, the collector of which is connected to a capacitor C12 which, together with the resistors R22 to R24, forms a timing element t1.
  • the control voltage for the transistor T2 is taken from the resistor R23, which, as already mentioned, acts as a voltage-controlled attenuator.
  • the rectified control voltage is fed via resistor R14 to a further timer t2 formed by capacitor C11 and resistors R15 and R16, the time constant of which is greater than that of the timer t1, the control transistor T4 being connected to the timing element t2.
  • the capacitor C11 is also charged via the resistor R14 and the voltage-controlled filter 4 is therefore activated.
  • the decay time for the voltage-controlled attenuator 3 and the voltage-controlled filter 4 is determined by the capacitor C11 and the combination of the resistors R15 and R16 in parallel with the resistors R14 and R22 to R24.
  • FIG. 6 shows a detail of the connection of the control voltage to the filter A of an embodiment that has been slightly modified compared to FIG. 4.
  • the resistor R e is designed as a potentiometer R e ', the two ends of which are connected to the transistor T3 and via a resistor R e to the transistor T4 and the center connection of which to the capacitor C8 is connected.
  • the rest of the circuit remains unchanged compared to that of FIG. 4.
  • the voltage-controlled filter A is therefore acted upon by a signal voltage taken from the preamplifier 2 and the control voltage that the rectifier circuit 7 supplies.
  • a high signal voltage has a dampening effect on the effect of filter A.
  • FIG. 7 A further possibility of applying filter A with a signal voltage taken from preamplifier 2 in addition to applying the control voltage is shown in FIG. 7, which can also be used in the circuit according to FIG. 4.
  • the transistor T3 is connected via a potentiometer R e 'to the capacitor C8, at the center connection of the transistor T4 is connected via the resistor R e .
  • FIG. 5 shows a further exemplary embodiment of a hearing device according to the invention, in which a voltage-controlled filter 4 according to FIG. 3 is arranged.
  • the capacitors C5 to C7 with the resistors R4 to R6 form a high-pass filter and the resistors R10 ', R11' and R12 with the capacitors C9 ', C10' and C11 'form a low-pass filter, which the four-pole A and B in Fig. 3 correspond.
  • the control voltage designated V c1 in FIG. 3 is formed by the rectifier circuit 7, which in the embodiment according to FIG. 5 is formed by the two transistors T7, T8, the diode D and the resistors R18 to R21 and the resistors R25, R26 is removed and fed to the four-pole A via the resistors R8 'and R6. 5, the resistor R18 is used for balancing
  • the control voltage designated V c2 in FIG. 3 is taken from the supply voltage and fed via the divider R13 'to R15' to the four-pin connector B, thus changing the operating point of the transistor T4 ', the response threshold of the transistor T3' and thus also that of the High pass A can be adjusted.
  • the rectifier circuit 7 is constructed in the embodiment according to FIG. 5 with NPN transistors.
  • the rest of the circuit is essentially the same as that of FIG. 4.
  • the timer t1 formed by resistors R22 to R24 and capacitor C12, to which the voltage-controlled attenuator 3 formed by transistor T2 is connected, has a smaller time constant than the timer t2 formed by the capacitor C8 'and the resistor R8', to which the four-pole A is connected.

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  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Neurosurgery (AREA)
  • Otolaryngology (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Networks Using Active Elements (AREA)
  • Amplifiers (AREA)
  • Tone Control, Compression And Expansion, Limiting Amplitude (AREA)

Description

Die Erfindung bezieht sich auf eine Einkanal-Schaltung für ein Hörgerät für Schwerhörige mit einem Vor- und einem Endverstärker, einem Mikrophon und einem Hörer, sowie einer vorzugsweise als Vollweggleichrichterschaltung aufgebauten Gleichrichterschaltung zur Erzeugung einer Steuerspannung für einen spannungsabhängigen Verstärker oder Abschwächer, der dem Vorverstärker nachgeschaltet ist, einem Zeitglied und einem spannungsgesteuerten Filter.The invention relates to a single-channel circuit for a hearing aid for the hearing impaired with a preamplifier and a power amplifier, a microphone and a receiver, and a rectifier circuit, preferably constructed as a full-wave rectifier circuit, for generating a control voltage for a voltage-dependent amplifier or attenuator, which is connected downstream of the preamplifier is, a timing element and a voltage-controlled filter.

Eine solche Schaltung wurde durch die US-PS 4 790 018 bekannt. Bei dieser bekannten Lösung ist die Gleichrichterschaltung und der zu dieser in Serie geschaltete Abschwächer in den Steuerkreis des spannungsgesteuerten Filters geschaltet. Dabei erfolgt die Signalabnahme für die Gleichrichterschaltung vor dem spannungsgesteuerten Filter. Dabei ergibt sich jedoch der Nachteil, daß lediglich eine Abschwächung bzw. Dämpfung der tieferen Frequenzen möglich ist. Dies ist aber in vielen Fällen, insbesondere in einer lärmerfüllten Umgebung nicht ausreichend, um eine befriedigende Sprachverständlichkeit zu erreichen. Grund dafür ist der Umstand, daß ein nicht unbeträchtlicher Teil des Lärmes Frequenzen aufweist, die nahe dem Frequenzbereich der menschlichen Sprache liegen.Such a circuit was known from US Pat. No. 4,790,018. In this known solution, the rectifier circuit and the attenuator connected in series with it are connected in the control circuit of the voltage-controlled filter. The signal for the rectifier circuit is taken before the voltage-controlled filter. However, there is the disadvantage that only an attenuation or attenuation of the lower frequencies is possible. However, in many cases, especially in a noisy environment, this is not sufficient to achieve satisfactory speech intelligibility. The reason for this is the fact that a not inconsiderable part of the noise has frequencies that are close to the frequency range of human speech.

Weiters wurde durch die AT-PS 371 306 eine Schaltung bekannt, bei der das Zeitglied im Signalkanal angeordnet ist, um die durch die Verzögerungszeit der automatischen Verstärkungssteuerung auftretenden kurzzeitigen Signalspitzen zu unterdrücken. Bei solchen Schaltungen ergibt sich eine vom Signalpegel der zu verstärkenden akustischen Signale abhängige Verstärkung, wodurch ein Übersteuern vermieden und das Ausgangssignal des Hörgerätes innerhalb eines bestimmten Lautstärke-Bereiches gehalten werden kann, wodurch unangenehm starke Lautstärkeschwankungen vermieden werden können. Bei solchen Schaltungen bleibt jedoch der Frequenzgang über den gesamten Verstärkungsbereich im wesentlichen gleich, was dazu führt, daß bei lauteren Hintergrundgeräuschen die Sprachverständlichkeit leidet.Furthermore, a circuit was known from AT-PS 371 306 in which the timing element is arranged in the signal channel in order to suppress the short-term signal peaks which occur due to the delay time of the automatic gain control. Such circuits result in an amplification dependent on the signal level of the acoustic signals to be amplified, as a result of which overdriving can be avoided and the output signal of the hearing aid can be kept within a certain volume range, as a result of which uncomfortably large fluctuations in volume can be avoided. In such circuits, however, the frequency response remains essentially the same over the entire amplification range, which means that speech intelligibility suffers from louder background noise.

Eine bessere Anpassung des Frequenzganges der Verstärkung an den Hörverlust des Benutzers wird bei Hörgeräten durch zwei- und mehrkanalige Schaltungen erreicht, die meist eine Dynamik-Kompression im Tieftonkanal und eine lineare Verstärkung im Hochtonkanal aufweisen, wobei vor der Endstufe die beiden Signale summiert werden. Dabei wird die Kompression im Tieftonkanal mit einem spannungsgesteuerten Verstärker erreicht.A better adaptation of the frequency response of the amplification to the hearing loss of the user is achieved in the case of hearing aids by two-channel and multi-channel circuits, which usually have dynamic compression in the low-frequency channel and linear amplification in the high-frequency channel, the two signals being summed upstream of the output stage. The compression in the bass channel is achieved with a voltage-controlled amplifier.

Der Nachteil dieser bekannten mehrkanaligen Schaltungen liegt in dem hohen Aufwand, den diese erfordern. Außerdem muß auch das eine solche Schaltung aufnehmende Gehäuse ein entsprechend großes Volumen aufweisen, was gerade bei Hörgeräten ein erheblicher Nachteil ist.The disadvantage of these known multi-channel circuits lies in the high outlay that they require. In addition, the housing accommodating such a circuit must also have a correspondingly large volume, which is a considerable disadvantage particularly in the case of hearing aids.

Ziel der Erfindung ist es diese Nachteile zu vermeiden und eine Schaltung der eingangs erwähnten Art vorzuschlagen, die im Hinblick auf die Sprachverständlichkeit eine sehr günstige Charakteristik über den gesamten Verstärkungsbereich ermöglicht.The aim of the invention is to avoid these disadvantages and to propose a circuit of the type mentioned at the outset which, with regard to speech intelligibility, enables a very favorable characteristic over the entire amplification range.

Erfindungsgemäß wird dies dadurch erreicht, daß der Vorverstärker, der spannungsgesteuerte Verstärker oder Abschwächer das spannungsgesteuerte Filter und die Gleichrichterschaltung in Reihe geschaltet sind, wobei die Gleichrichterschaltung eingangsseitig mit dem Ausgang des spannungsgesteuerten Filters und ausgangsseitig über das Zeitglied mit dem Steuereingang des spannungsgesteuerten Filters verbunden ist. Dabei sind unter spannungsgesteuerten Filter Schaltungskonfigurationen zu verstehen, die den Frequenzgang eines Gerätes in Abhängigkeit vom Pegel eines Eingangssignales in irgend einer Weise, außer einer einfachen Verstärkung oder Abschwächung, verändern.According to the invention, this is achieved in that the preamplifier, the voltage-controlled amplifier or attenuator, the voltage-controlled filter and the rectifier circuit are connected in series, the rectifier circuit being connected on the input side to the output of the voltage-controlled filter and on the output side via the timing element to the control input of the voltage-controlled filter. Voltage-controlled filters are to be understood as circuit configurations that change the frequency response of a device depending on the level of an input signal in any way, apart from simple amplification or attenuation.

Durch diese Maßnahmen ist es möglich, den Frequenzgang über den Verstärkungsbereich in Abhängigkeit vom Pegel des aufgenommenen Schallsignales so zu verändern, daß bei lauten Eingangssignalen eine Absenkung der Verstärkung im Bereich der tiefen Frequenzen stattfindet, bzw. eine breitbandige Wiedergabe bei kleinen Eingangssignalen sichergestellt ist. Weiters wird durch die vorgeschlagenen Maßnahmen bei lauten Eingangssignalen auch eine Anhebung der Signale im Bereich der höheren Frequenzen erreicht, wodurch die Sprachverständlichkeit wesentlich gesteigert wird.These measures make it possible to change the frequency response over the amplification range as a function of the level of the recorded sound signal in such a way that when the input signals are loud, the amplification is reduced in the range of the low frequencies, or a broadband reproduction is ensured for small input signals. Furthermore, the proposed measures for loud input signals also increase the signals in the higher frequency range, which significantly increases speech intelligibility.

Bei Verwendung einer Vollweggleichrichterschaltung ergibt sich der Vorteil, daß auch bei stark unsymmetrischen Signalen, wie Sprachsignalen, eine Regelspannung erzeugt wird, die wertmäßig sehr genau dem Schallsignal entspricht.When using a full-wave rectifier circuit, there is the advantage that even with strongly asymmetrical signals, such as voice signals, a control voltage is generated which corresponds in value to the sound signal very precisely.

Nach einem weiteren Merkmal der Erfindung kann vorgesehen sein, daß auch der spannungsgesteuerte Verstärker über ein separates Zeitglied an der Gleichrichterschaltung angeschlossen ist.According to a further feature of the invention, it can be provided that the voltage-controlled amplifier is also connected to the rectifier circuit via a separate timer.

Durch die Anschaltung des spannungsgesteuerten Verstärkers und des spannungsgesteuerten Filters über separate Zeitglieder ergibt sich der Vorteil, daß deren Charakteristik getrennt voneinander an die jeweiligen Bedürfnisse angepaßt werden kann.By connecting the voltage-controlled amplifier and the voltage-controlled filter via separate timing elements, there is the advantage that their characteristics can be adapted separately to the respective needs.

Bei Hörgeräten wird aus Gründen eines kompakten Aufbaues zur Spannungsversorgung eine möglichst kleine Batterie verwendet, sodaß nur mit sehr kleinen Spannungen gearbeitet werden kann. Aus diesen Gründen ist es erforderlich eine Gleichrichterschaltung zu verwenden, die bei kleinen Spannungen arbeiten kann.In the case of hearing aids, the smallest possible battery is used for the power supply for reasons of a compact structure, so that only very low voltages can be used. For these reasons, it is necessary to use a rectifier circuit that can operate at low voltages.

Erfindungsgemäß wird daher vorgeschlagen, daß die Gleichrichterschaltung durch zwei Transistoren gebildet ist, deren Hauptstrompfade mit Widerständen in Serie geschaltet sind und diese Serienschaltungen zueinander parallel geschaltet sind, wobei die Basis des einen über eine Diode mit dem Kollektor des zweiten Transistors und die Basen der beiden Transistoren über mindestens einen Widerstand miteinander und der mit der Diode verbundene Kollektor des einen Transistors über einen weiteren Widerstand mit der Basis dieses Transistors verbunden ist und die Regelgleichspannung am Kollektor des mit seiner Basis an der Diode angeschlossenen Transistors abgreifbar ist.According to the invention it is therefore proposed that the rectifier circuit is formed by two transistors, the main current paths of which are connected in series with resistors and these series circuits are connected in parallel with one another, the base of the one via a diode with the collector of the second transistor and the bases of the two transistors is connected to one another via at least one resistor and the collector of one transistor connected to the diode is connected to the base of this transistor via a further resistor and the control DC voltage at the collector of the transistor connected to the diode by its base can be tapped off.

Grundsätzlich könnte auch eine Gleichrichterbrücke verwendet werden, doch würden sich in einem solchen Falle aufgrund der relativ hohen Anlaufspannungen der Dioden erhebliche Probleme aufgrund der niedrigen Spannungen ergeben.In principle, a rectifier bridge could also be used, but in such a case there would be considerable problems due to the low voltages due to the relatively high starting voltages of the diodes.

Bei dem vorgeschlagenen Aufbau der Gleichrichterschaltung wirkt sich dagegen aufgrund der Verstärkung mittels des ersten Transistors die Anlaufspannung der Diode praktisch kaum aus.In contrast, in the proposed construction of the rectifier circuit, the starting voltage of the diode has virtually no effect due to the amplification by means of the first transistor.

Weiters kann vorgesehen sein, daß das spannungsgesteuerte Filter durch einen Drei- oder Vierpol gebildet ist, dem ein in Bootstrapschaltung geschalteter Transistor nachgeschaltet ist, wobei vorzugsweise ein Steuertransistor vorgesehen ist, dessen Hauptstrompfad in Serie mit jenem des in Bootstrapschaltung geschalteten Transistors geschaltet ist und dessen Basis mit der die Steuerspannung liefernden Gleichrichterschaltung verbunden ist.Furthermore, it can be provided that the voltage-controlled filter is formed by a three- or four-pole, which is followed by a transistor connected in bootstrap circuit, preferably a control transistor is provided, the main current path of which is connected in series with that of the transistor switched in bootstrap circuit and the base thereof is connected to the rectifier circuit supplying the control voltage.

Auf diese Weise ergibt sich ein sehr einfacher Aufbau eines spannungsgesteuerten Filters, das eine Beeinflussung des Frequenzganges des Hörgerätes in Abhängigkeit vom Pegel des aufgenommenen Schallsignales ermöglicht.This results in a very simple construction of a voltage-controlled filter, which enables the frequency response of the hearing aid to be influenced as a function of the level of the recorded sound signal.

Nach einem weiteren Merkmal der Erfindung ist vorgesehen, daß das spannungsgesteuerte Filter durch zwei unterschiedliche Drei-, vorzugsweise aber Vierpole gebildet ist, denen in Bootstrapschaltung geschaltete Transistoren nachgeschaltet sind, wobei wenigstens eine deren Basen mit der Gleichrichterschaltung über ein Zeitglied verbunden ist und der Vorverstärker gegebenenfalls über den Mittelanschluß eines Potentiometers mit den Eingängen der Drei- bzw. Vierpole verbunden ist.According to a further feature of the invention it is provided that the voltage-controlled filter is formed by two different three-pole, but preferably four-pole, which are followed by transistors connected in bootstrap circuit, at least one of whose bases is connected to the rectifier circuit via a timing element and the preamplifier, if appropriate is connected to the inputs of the three or four poles via the center connection of a potentiometer.

Dies ermöglicht es den Frequenzgang der Verstärkung in Abhängigkeit vom Pegel des aufgenommenen Schallsignales zu verändern und dadurch eine wesentliche Verbesserung der Sprachverständlichkeit zu erreichen.This makes it possible to change the frequency response of the amplification as a function of the level of the recorded sound signal and thereby to achieve a substantial improvement in speech intelligibility.

Bei einer besonders bevorzugten Ausführungsform der Erfindung kann vorgesehen sein, daß das spannungsgesteuerte Filter über eine Potentiometerschaltung angesteuert ist, an der eine vom Vorverstärker abgenommene Signalspannung und die von der Gleichrichterschaltung kommende Regelgleichspannung angelegt ist, wobei die vom Vorverstärker abgenommene Signalspannung bei hohen Signalpegeln das Filter dämpft.In a particularly preferred embodiment of the invention, it can be provided that the voltage-controlled filter is controlled via a potentiometer circuit to which a signal voltage taken from the preamplifier and the control DC voltage coming from the rectifier circuit is applied, the signal voltage taken from the preamplifier damping the filter at high signal levels .

Dies ermöglicht eine insbesondere bei Vorliegen extremer Verhältnisse eine im Sinne einer besseren Sprachverständlichkeit günstige Beeinflussung der Betriebscharakteristik des Hörgerätes.This enables the operating characteristics of the hearing aid to be influenced, particularly in the presence of extreme conditions, in the sense of better speech intelligibility.

Die Erfindung wird nun anhand der Zeichnung näher erläutert Dabei zeigen:

  • Fig. 1 ein Blockschaltbild eines erfindungsgemäßen Hörgerätes,
  • Fig. 2 und 3 Blockschaltbilder verschiedener Ausführungsformen von spannungsgesteuerten Filtern,
  • Fig. 4 und 5 Schaltbilder zweier Ausführungsformen erfindungsgemäßer Hörgeräte und
  • Fig. 6 und 7 Varianten von Details der Schaltung nach Fig. 4 zur Ansteuerung des spannungsgesteuerten Filters mit der Regelspannung und einer vom Vorverstärker abgenommen Signalspannung.
The invention will now be explained in more detail with reference to the drawing.
  • 1 is a block diagram of a hearing aid according to the invention,
  • 2 and 3 block diagrams of different embodiments of voltage-controlled filters,
  • 4 and 5 circuit diagrams of two embodiments of hearing aids according to the invention and
  • 6 and 7 variants of details of the circuit according to FIG. 4 for controlling the voltage-controlled filter with the control voltage and a signal voltage taken from the preamplifier.

Der prinzipielle Aufbau eines erfindungsgmäßen Hörgerätes ist in der Fig. 1 dargestellt. Dabei ist einem Mikrofon 1 in üblicher Weise ein Vorverstärker 2 nachgeschaltet. Dieser ist ausgangsseitig mit einem spannungsgesteuerten Verstärker 3 verbunden, der auch einen Verstärkungsfaktor < 1 aufweisen und daher als Abschwächer wirken kann. Diesem spannungsgesteuerten Verstärker 3, der durch einen bipolaren Transistor oder z.B. durch einen arbeitspunktgeregelten Verstärker gebildet sein kann und zur automatischen Lautstärkeregelung dient, ist eine spannungsgesteuertes Filter 4 nachgeschaltet, das eine automatische Frequenzgangregelung ermöglicht.The basic structure of a hearing aid according to the invention is shown in FIG. 1. A microphone 1 is followed by a preamplifier 2 in the usual way. This is connected on the output side to a voltage-controlled amplifier 3, which also has a gain factor <1 and can therefore act as an attenuator. This voltage controlled amplifier 3, which is connected by a bipolar transistor or e.g. can be formed by an operating point-controlled amplifier and is used for automatic volume control, a voltage-controlled filter 4 is connected downstream, which enables automatic frequency response control.

Diese ist vorzugsweise als automatische Tiefenabsenkung beim Auftreten lauter Signale ausgebildet, die das Hören und Verstehen von Sprache in einer lärmerfüllten Umgebung erleichtert.This is preferably designed as an automatic depth reduction when loud signals occur, which makes it easier to hear and understand speech in a noisy environment.

Das vom Filter 4 aufbereitete Signal gelangt zum Endverstärker 5, an dem ein Hörer 6 angeschaltet ist. Weiters ist noch eine Gleichrichterschaltung 7 vorgesehen, die ein zwischen dem spannungsgesteuerten Filter 4 und dem Endverstärker 5, oder zwischen dem spannungsgesteuerten Verstärker 3 und dem spannungsgesteuerten Filter 5 abgenommenes Signal gleichrichtet und als Regelspannung dem spannungsgesteuerten Verstärker 3 und dem spannungsgesteuerten Filter 5 zuführt. Dabei hängt es vom Einbauort des nicht dargestellten Lautstärkestellers ab, ob die Regelung als eingangs- oder ausgangsgesteuerte Regelung ausgebildet ist.The signal processed by the filter 4 reaches the power amplifier 5, to which a receiver 6 is switched on. Furthermore, a rectifier circuit 7 is also provided, which rectifies a signal taken between the voltage-controlled filter 4 and the power amplifier 5, or between the voltage-controlled amplifier 3 and the voltage-controlled filter 5, and supplies it as a control voltage to the voltage-controlled amplifier 3 and the voltage-controlled filter 5. It depends on the installation location of the volume control, not shown, whether the control is designed as an input- or output-controlled control.

Die Gleichrichterschaltung 7 ist als Vollweggleichrichter ausgebildet und wird später anhand der Fig. 4 und 5 näher erläutert.The rectifier circuit 7 is designed as a full-wave rectifier and will be explained in more detail later with reference to FIGS. 4 and 5.

Das spannungsgesteuerte Filter 4 kann z.B. gemäß der Fig. 2 aufgebaut sein, wobei ein Vierpol A vorgesehen ist, der z.B. als R/C-Filter aufgebaut sein kann und dem ein Transistor 9 in Bootstrapschaltung nachgeschaltet ist, dessen Kollektor an die Versorgungsspannung Vcc angeschlossen und dessen Basis und Emitter mit dem Vierpol A verbunden sind, der als Hoch- Tief- oder Bandpaß oder als Bandsperre ausgebildet sein kann.The voltage-controlled filter 4 can be constructed, for example, according to FIG. 2, a four-pole A being provided, which can be constructed, for example, as an R / C filter and which is followed by a transistor 9 in bootstrap circuit, the collector of which is connected to the supply voltage V CC and whose base and emitter are connected to the four-pin A, which can be designed as a high-low or bandpass or as a bandstop.

Dabei ist der Emitterwiderstand Re mit einem Steuertransistor 8 in Serie geschaltet, dessen Emitter mit Masse und dessen Basis mit einer von der Gleichrichterschaltung 7 abgenommenen Steuerspannung Vc beaufschlagt ist. Weist diese Regelspannung ein hohes Potential auf, so ist der Transistor 8 voll leitend und wirkt auf das Ausgangssignal des Vierpoles A wie ein Emitterfolger.The emitter resistor R e is connected in series with a control transistor 8, the emitter of which is grounded and the base of which is supplied with a control voltage V c taken from the rectifier circuit 7. If this control voltage has a high potential, the transistor 8 is fully conductive and acts on the output signal of the four-pole A like an emitter follower.

Ist die Regelspannung Vc sehr niedrig, so sperrt der Transistor 8 und das Eingangssignal des Vierpoles A geht im wesentlichen unverändert direkt an den Ausgang O, z.B. über die Kondensatoren C4, C8 und den Widerstand R5, wie dies aus der Fig. 4 ersichtlich ist.If the control voltage V c is very low, the transistor 8 blocks and the input signal of the four-pole A essentially goes unchanged directly to the output O, for example via the capacitors C4, C8 and the resistor R5, as can be seen from FIG. 4 .

Eine weitere Ausführungsform eines spannungsgesteuerten Filters 4 ist in der Fig. 3 dargestellt. Dabei sind zwei Vierpole A und B vorgesehen, die mit zwei parallel geschalteten Transistoren 10 und 11 mit einem gemeinsamen Emitterwiderstand Re gekoppelt sind. Die beiden Vierpole A und B sind zweckmäßigerweise als Hochpaß- bzw. als Tiefpaßfilter ausgebildet. An den Ausgängen der Vierpole A und B, bzw. an den Basen der Transistoren 10, 11 sind über Widerstände Steuerspannungen Vc1, Vc2 angeschlossen, die von der Gleichrichterschaltung 7 abgeleitet sind und eine unterschiedliche Höhe aufweisen können. Dabei können die beiden Steuerspannungen z.B. an einer an die Gleichrichterschaltung 7 angeschlossenen, in der Fig. 3 nicht dargestellten Spannungsteilerschaltung abgenommen werden.Another embodiment of a voltage-controlled filter 4 is shown in FIG. 3. Two four-pole A and B are provided, which are coupled to two transistors 10 and 11 connected in parallel with a common emitter resistor R e . The two four poles A and B are expediently designed as a high-pass or low-pass filter. Control voltages V c1 , V c2 , which are derived from the rectifier circuit 7 and can have a different height, are connected via resistors to the outputs of the four-pole A and B, or to the bases of the transistors 10, 11. The two control voltages can be taken, for example, from a voltage divider circuit connected to the rectifier circuit 7 and not shown in FIG. 3.

Das Eingangssignal I kann bei dieser Ausbildung des spannungsgesteuerten Filters über das Potentiometer Ri auf die beiden Vierpole A und B des Filters aufgeteilt werden, wodurch eine feste Voreinstellung gewählt werden kann.In this configuration of the voltage-controlled filter, the input signal I can be divided over the two four-pole terminals A and B of the filter via the potentiometer Ri, as a result of which a fixed presetting can be selected.

Werden die beiden Steuerspannungen Vc1 und Vc2 gleich gewählt, so sind beide Vierpolschaltungen A und B gleichzeitig in Funktion und eine Veränderung der gemeinsamen Steuerspannung ermöglicht die Einstellung aller Zwischenfunktionen.If the two control voltages V c1 and V c2 are chosen to be the same, both four-pole circuits A and B function simultaneously and a change in the common control voltage enables the setting of all intermediate functions.

Fig. 4 zeigt ein Ausführungsbeispiel eines erfindungsgemäßen Hörgerätes. Dabei wirkt der Transistor T1 als Vorverstärker 2, dessen Basis über den Kondensator C2 mit dem Mikrophon 1 verbunden ist. Der Transistor T1 ist in üblicher Weise mit den Widerständen R3, R1 beschaltet.Fig. 4 shows an embodiment of a hearing aid according to the invention. The transistor T1 acts as a preamplifier 2, the base of which is connected to the microphone 1 via the capacitor C2. The transistor T1 is connected in the usual way with the resistors R3, R1.

Das R/C Glied R2 und C1 dient zur Siebung.The R / C link R2 and C1 is used for screening.

Der Transistor T2 dient in Verbindung mit dem Widerstand R4 und dem Koppelkondensator C3 als spannungsgesteuerter Abschwächer 3 für eine automatische Verstärkungsregelung.The transistor T2, in conjunction with the resistor R4 and the coupling capacitor C3, serves as a voltage-controlled attenuator 3 for an automatic gain control.

Die Kondensatoren C4 bis C7 bilden in Verbindung mit den Widerständen R5 bis R8 einen Vierpol höherer Ordnung, der in Verbindung mit dem Transistor T3, dem Emitterwiderstand Re und dem Steuertransistor T4 ein spannungsgesteuertes Filter 4 bildet, wobei die Transistoren T3 und T4 den Transistoren 8 und 9 in der Fig. 2 entsprechen.The capacitors C4 to C7 in conjunction with the resistors R5 to R8 form a four-pole higher order, which in conjunction with the transistor T3, the emitter resistor R e and the control transistor T4 forms a voltage-controlled filter 4, the transistors T3 and T4 being the transistors 8 and 9 in Fig. 2 correspond.

Ist nun die von der Gleichrichterschaltung abgenommene Regelspannung klein, gelangt das Signal im wesentlichen unverändert über den Kondensator C4 den Widerstand R5 und dem Kondensator C8 an den Verstärkungstransistor T5, der mit dem Widerstand R11, dem Kondensator C9, dem Widerstand R13 und dem Transistor T6 in bekannter Weise eine Endstufe bildet, an der der Hörer 6 angeschlossen ist.If the control voltage taken off by the rectifier circuit is now small, the signal reaches resistor R5 and capacitor C8, essentially unchanged, via capacitor C4 to amplifying transistor T5, which has the resistor R11, the capacitor C9, the resistor R13 and the transistor T6 in a known manner forms an output stage to which the receiver 6 is connected.

Ist dagegen die an dem Steuertransistor T4 anliegende Regelspannung hoch, so arbeitet der Transistor T3 als Emitterfolger und der Vierpol A bildet ein Hochpaßfilter vierter Ordnung in einer Bootstrapschaltung.If, on the other hand, the control voltage applied to the control transistor T4 is high, the transistor T3 works as an emitter follower and the four-pole A forms a fourth-order high-pass filter in a bootstrap circuit.

Das Signal für die Gleichrichterschaltung 7, die im wesentlichen durch die beiden Transistoren T7 und T8 und die Diode D gebildet ist, wird am Transistor T5 abgenommen und gelangt über den Kondensator C10 und den Widerstand R17 zur Basis des Transistors T7 der Gleichrichterschaltung 7. Bei dieser Gleichrichterschaltung dient der Widerstand R18 zur Arbeitspunkteinstellung.The signal for the rectifier circuit 7, which is essentially formed by the two transistors T7 and T8 and the diode D, is taken off at the transistor T5 and reaches the base of the transistor T7 of the rectifier circuit 7 via the capacitor C10 and the resistor R17 Rectifier circuit, resistor R18 is used to set the operating point.

Bei negativen Halbwellen des Eingangssignales sperrt die Diode D und die Signalübertragung erfolgt direkt über den Widerstand R20. Bei positiven Halbwellen bestimmt das Verhältnis der Widerstände R19 und R17 die Verstärkung. Die Symmetrie bei der Vollweggleichrichtung des Eingangssignales wird durch die entsprechende Dimensionierung der Widerstände R18 bis R20 sichergestellt.If the half-wave of the input signal is negative, the diode D blocks and the signal is transmitted directly via the resistor R20. In the case of positive half-waves, the ratio of the resistors R19 and R17 determines the gain. The symmetry in the full-wave rectification of the input signal is ensured by the appropriate dimensioning of the resistors R18 to R20.

Bei der in der Fig. 4 dargestellten Ausführungsform tritt eine mit steigendem Signal abnehmende Regelspannung an der Basis des Transistors T8 auf. Bei einer umgekehrt gepolten Diode D wäre es auch möglich eine mit steigendem Signal zunehmende Regelspannung abzugreifen.In the embodiment shown in FIG. 4, a control voltage that decreases with an increasing signal occurs at the base of transistor T8. In the case of a reversely polarized diode D, it would also be possible to tap a control voltage which increases as the signal increases.

Der Transistor T8 wirkt als ein Regelspannungsverstärker, dessen Kollektor mit einem Kondensator C12 verbunden ist, der gemeinsam mit den Widerständen R22 bis R24 ein Zeitglied t1 bildet. Dabei wird an dem Widerstand R23 die Regelspannung für den Transistor T2 abgenommen, der, wie bereits erwähnt als spannungsgesteuerter Abschwächer wirkt.The transistor T8 acts as a control voltage amplifier, the collector of which is connected to a capacitor C12 which, together with the resistors R22 to R24, forms a timing element t1. The control voltage for the transistor T2 is taken from the resistor R23, which, as already mentioned, acts as a voltage-controlled attenuator.

Weiters wird die gleichgerichtete Regelspannung über den Widerstand R14 einem weiteren durch den Kondensator C11 und den widerständen R15 und R16 gebildeten weiteren Zeitglied t2 zugeführt, dessen Zeitkonstante größer als jene des Zeitgliedes t1 ist, wobei an dem Zeitglied t2 der Steuertransistor T4 angeschlossen ist.Furthermore, the rectified control voltage is fed via resistor R14 to a further timer t2 formed by capacitor C11 and resistors R15 and R16, the time constant of which is greater than that of the timer t1, the control transistor T4 being connected to the timing element t2.

Es ergibt sich daher, daß für kurze Impulse bzw. kurze Signale nur die automatische Verstärkungsregelung wirksam ist, die im wesentlichen durch den Transistor T2 gebildet ist, die über das Zeitglied t1 mit der kürzeren Zeitkonstante angesteuert ist, wobei die Einschwingzeit durch den Innenwiderstand des Transistors T8 und den Kondensator C12 bestimmt ist und die Ausschwingzeit durch den Kondensator C12 und den sich aus der Parallelschaltung des Widerstandes R14 mit den Widerständen R22 bis R24 ergebenden Widerstandes bestimmt ist.It follows that only the automatic gain control is effective for short pulses or short signals, which is essentially formed by the transistor T2, which is driven by the timer t1 with the shorter time constant, the settling time by the internal resistance of the transistor T8 and the capacitor C12 is determined and the settling time is determined by the capacitor C12 and the resistance resulting from the parallel connection of the resistor R14 with the resistors R22 to R24.

Bei länger dauernden Signalen mit großen Amplituden wird auch der Kondensator C11 über den Widerstand R14 geladen und daher das spannungsgesteuerte Filter 4 aktiviert. Die Ausschwingzeit für den spannungsgesteuerten Abschwächer 3 und das spannungsgesteuerte Filter 4 ist durch den Kondensator C11 und die Kombination der Widerstände R15 und R16 in Parallelschaltung zu den Widerständen R14 und R22 bis R24 bestimmt.In the case of signals of longer duration with large amplitudes, the capacitor C11 is also charged via the resistor R14 and the voltage-controlled filter 4 is therefore activated. The decay time for the voltage-controlled attenuator 3 and the voltage-controlled filter 4 is determined by the capacitor C11 and the combination of the resistors R15 and R16 in parallel with the resistors R14 and R22 to R24.

Die Fig. 6 zeigt ein Detail der Anschaltung der Regelspannung an das Filter A einer gegenüber der Fig. 4 etwas geänderten Ausführungsform. Diese unterscheidet sich von jener nach der Fig. 4 dadurch, daß der Widerstand Re als Potentiometer Re′ ausgebildet ist, dessen beide Enden mit dem Transistor T3 und über einen Widerstand Re mit dem Transistor T4 verbunden sind und dessen Mittelanschluß mit dem Kondensator C8 verbunden ist. Die übrige Schaltung bleibt gegenüber jener nach der Fig. 4 unverändert. Es kommt daher zu einer Beaufschlagung des spannungsgesteuerten Filters A mit einer vom Vorverstärker 2 abgenommenen Signalspannung und der Regelspannung, die die Gleichrichterschaltung 7 liefert. Dabei wirkt sich eine hohe Signalspannung je nach Potentiometerstellung dämpfend auf Die Wirkung des Filter A aus.FIG. 6 shows a detail of the connection of the control voltage to the filter A of an embodiment that has been slightly modified compared to FIG. 4. This differs from that according to FIG. 4 in that the resistor R e is designed as a potentiometer R e ', the two ends of which are connected to the transistor T3 and via a resistor R e to the transistor T4 and the center connection of which to the capacitor C8 is connected. The rest of the circuit remains unchanged compared to that of FIG. 4. The voltage-controlled filter A is therefore acted upon by a signal voltage taken from the preamplifier 2 and the control voltage that the rectifier circuit 7 supplies. Depending on the potentiometer setting, a high signal voltage has a dampening effect on the effect of filter A.

Eine weitere Möglichkeit einer Beaufschlagung des Filters A mit einer vom Vorverstärker 2 abgenommenen Signalspannung zusätzlich zur Beaufschlagung mit der Regelspannung ist in der Fig. 7 dargestellt, die ebenfalls bei der Schaltung nach der Fig. 4 zur Anwendung kommen kann. Dabei ist der Transistor T3 über ein Potentiometer Re′ mit dem Kondensator C8 verbunden, an dessen Mittelanschluß der Transistor T4 über den Widerstand Re angeschlossen ist.A further possibility of applying filter A with a signal voltage taken from preamplifier 2 in addition to applying the control voltage is shown in FIG. 7, which can also be used in the circuit according to FIG. 4. The transistor T3 is connected via a potentiometer R e 'to the capacitor C8, at the center connection of the transistor T4 is connected via the resistor R e .

Die Fig. 5 zeigt ein weiteres Ausführungsbeispiel eines erfindungsgemäßen Hörgerätes, bei dem ein spannungsgesteuertes Filter 4 gemäß der Fig. 3 angeordnet ist. Bei diesem bilden die Kondensatoren C5 bis C7 mit den Widerständen R4 bis R6 ein Hochpaßfilter und die Widerstände R10′, R11′ und R12 mit den Kondensatoren C9′, C10′ und C11′ ein Tiefpaßfilter, die den Vierpolen A und B in der Fig. 3 entsprechen.FIG. 5 shows a further exemplary embodiment of a hearing device according to the invention, in which a voltage-controlled filter 4 according to FIG. 3 is arranged. In this, the capacitors C5 to C7 with the resistors R4 to R6 form a high-pass filter and the resistors R10 ', R11' and R12 with the capacitors C9 ', C10' and C11 'form a low-pass filter, which the four-pole A and B in Fig. 3 correspond.

Die in der Fig. 3 mit Vc1 bezeichnete Regelspannung wird von der Gleichrichterschaltung 7, die bei der Ausführungsform nach der Fig. 5 durch die beiden Transistoren T7, T8, die Diode D und die Widerstände R18 bis R21 und die Widerstände R25, R26 gebildet ist, abgenommen und über die Widerstände R8′ und R6 dem Vierpol A zugeführt. Bei der Verstärkerschaltung 7 nach der Fig. 5 dient der Widerstand R18 zum SymmetrierenThe control voltage designated V c1 in FIG. 3 is formed by the rectifier circuit 7, which in the embodiment according to FIG. 5 is formed by the two transistors T7, T8, the diode D and the resistors R18 to R21 and the resistors R25, R26 is removed and fed to the four-pole A via the resistors R8 'and R6. 5, the resistor R18 is used for balancing

Die in der Fig. 3 mit Vc2 bezeichnete Regelspannung wird von der Versorgungsspannung abgenommen und über den Teiler R13′ bis R15′ dem Vierpol B zugeführt, womit durch Verändern des Arbeitspunktes des Transistors T4′ die Ansprechschwelle des Transistors T3′ und damit auch die des Hochpasses A verstellt werden kann.The control voltage designated V c2 in FIG. 3 is taken from the supply voltage and fed via the divider R13 'to R15' to the four-pin connector B, thus changing the operating point of the transistor T4 ', the response threshold of the transistor T3' and thus also that of the High pass A can be adjusted.

Die Gleichrichterschaltung 7 ist bei der Ausführungsform nach der Fig. 5 mit NPN Transistoren aufgebaut.The rectifier circuit 7 is constructed in the embodiment according to FIG. 5 with NPN transistors.

Die übrige Schaltung ist im wesentlichen gleich mit jener nach der Fig. 4. Dabei weist das durch die Widerstände R22 bis R24 und den Kondensator C12 gebildete Zeitglied t1, an dem der durch den Transistor T2 gebildete spannungsgesteuerte Abschwächer 3 angeschlossen ist, eine kleinere Zeitkonstante als das durch den Kondensator C8′ und den Widerstand R8′ gebildete Zeitglied t2, auf, an dem der Vierpol A angeschlossen ist.The rest of the circuit is essentially the same as that of FIG. 4. The timer t1 formed by resistors R22 to R24 and capacitor C12, to which the voltage-controlled attenuator 3 formed by transistor T2 is connected, has a smaller time constant than the timer t2 formed by the capacitor C8 'and the resistor R8', to which the four-pole A is connected.

Claims (6)

  1. A single-channel circuit for a hearing aid for persons with an impaired hearing faculty, said circuit having a pre-amplifier and an output amplifier (2, 5), a microphone (1) and an earpiece (6) as well as a rectifier circuit (7) preferably arranged as a full-wave rectifier circuit for producing a control voltage for a non-linear amplifier or attenuator (3) which is connected behind said preamplifier, and a time function element (t2) and a voltage-controlled filter (4) characterized in that the preamplifier (2), the voltage-controlled amplifier or attenuator (3), the voltage-controlled filter (4) and the rectifier circuit (7) are connected in series, whereby the rectifier circuit (7) is connected on the input side to the output of the voltage-controlled filter (4) and is connected on the output side via the time function element (t2) to the control input of the voltage-controlled filter (4).
  2. A circuit as claimed in claim 1, characterized in that the voltage-controlled attenuator (3) is also connected to the rectifier circuit (7) via a separate time function element (t1).
  3. A circuit as claimed in claim 1 or 2, characterized in that the rectifier circuit (7) is formed by two transistors (T7, T8) whose main paths of current are connected in series by means of resistors (R21, R22, R23, R24, R25, R26) and that said series connections are connected in parallel to each other, whereby the base of the one transistor is connected with the collector of the second transistor (T7) via a diode (D) and the bases of the two transistors (T7, T8) are connected to each other via at least one resistor (R19) and the collector of the one transistor (T1) connected to the diode (D) is connected via a further resistor (20) to the base of said transistor and the direct voltage may be tapped from the collector of the transistor (T8) connected with its base to the diode (D).
  4. A circuit as claimed in one of the claims 1 to 3, characterized in that the voltage-controlled filter (4) is formed by a three- or four-pole (A) behind which a transistor (T3) connected in a bootstrap circuit is provided, whereby preferably a control transistor (T4) is provided whose main path of current is connected in series to the transistor (T3) arranged in the bootstrap circuit and whose base is connected to the rectifier circuit (7) providing the control voltage.
  5. A circuit as claimed in one of the claims 1 to 3, characterized in that the voltage-controlled filter (4) is arranged by two different three-poles, but preferably four-poles (A,B), behind which transistors (T3′, T4′) are connected within a bootstrap circuit, whereby at least one of their bases is connected to the rectifier circuit (7) via a time function element (t2) and, optionally, the pre-amplifier (2) is connected to the inputs of the three- or four-poles (A, B) via the central terminal of a potentiometer (Ri).
  6. A circuit as claimed in one of the claims 1 to 5, characterized in that the voltage-controlled filter (4) is controlled by a potentiometer circuit (Re, Re′) to which a signal voltage tapped from the pre-amplifier (2) and the control direct voltage coming from the rectifier circuit (7) are applied, whereby the signal voltage tapped from the pre-amplifier attenuates the effect of the filter in the event of high signal levels.
EP91890015A 1990-02-02 1991-01-28 One-channel circuit for hearing aid Revoked EP0446195B1 (en)

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AT0022890A AT403978B (en) 1990-02-02 1990-02-02 SINGLE CHANNEL CIRCUIT FOR A HEARING AID
AT228/90 1990-02-02

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EP0446195A2 EP0446195A2 (en) 1991-09-11
EP0446195A3 EP0446195A3 (en) 1992-11-25
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AT401129B (en) * 1994-12-21 1996-06-25 Viennatone Gmbh HEARING AID
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CN103458349A (en) * 2013-09-22 2013-12-18 北京九鹤科技有限公司 Hearing assisting system

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DE59103455D1 (en) 1994-12-15
EP0446195A2 (en) 1991-09-11
CA2034176A1 (en) 1991-08-03
CA2034176C (en) 1997-07-15
US5255320A (en) 1993-10-19
DK0446195T3 (en) 1994-12-05
ATA22890A (en) 1994-04-15
EP0446195A3 (en) 1992-11-25
AT403978B (en) 1998-07-27

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