GB2084427A - Piezoelectric Sound Generator - Google Patents

Piezoelectric Sound Generator Download PDF

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Publication number
GB2084427A
GB2084427A GB8028063A GB8028063A GB2084427A GB 2084427 A GB2084427 A GB 2084427A GB 8028063 A GB8028063 A GB 8028063A GB 8028063 A GB8028063 A GB 8028063A GB 2084427 A GB2084427 A GB 2084427A
Authority
GB
United Kingdom
Prior art keywords
resistor
generator
voltage
current
crystal
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.)
Withdrawn
Application number
GB8028063A
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
Priority to GB8028063A priority Critical patent/GB2084427A/en
Publication of GB2084427A publication Critical patent/GB2084427A/en
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K9/00—Devices in which sound is produced by vibrating a diaphragm or analogous element, e.g. fog horns, vehicle hooters or buzzers
    • G10K9/12—Devices in which sound is produced by vibrating a diaphragm or analogous element, e.g. fog horns, vehicle hooters or buzzers electrically operated
    • G10K9/122—Devices in which sound is produced by vibrating a diaphragm or analogous element, e.g. fog horns, vehicle hooters or buzzers electrically operated using piezoelectric driving means
    • 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
    • B06B1/0261—Driving circuits for generating signals continuous in time of a single frequency, e.g. a sine-wave with a feedback signal taken from a transducer or electrode connected to the driving transducer
    • 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

Abstract

A sound generator containing a piezoceramic crystal which has two pairs of electrodes (51, 52 and 51, 53), one pair 51, 52, receives a driving signal, which may or may not be increased in voltage by means of a step-up transformer (4), whilst the other pair (51, 53) provides a feed- back voltage. The feed-back voltage switches a current generator (1) which provides the drive signal. A resistor (3) is placed in series with power supply to the circuit and variation of the resistor value provides control over the amplitude of the drive signal whilst maintaining the stability of the oscillation of the crystal over a wide range. <IMAGE>

Description

SPECIFICATION An Electronic Circuit for Piezoelectric Buzzers The object of the present invention is to provide electronic circuit means to drive a piezoelectric crystal, so producing an audible acoustic signal with a wide dynamic range of noise output. To produce an efficient acoustic generator many different types of electronic circuits have been disclosed, where feedback is taken from a contact to the piezoelectric crystal to the circuit, in order that the crystal oscillates on or close to a resonant frequency of the crystal and its associated diaphragm. In general, any attempt to incorporate a variable resistor into such circuits to provide volume control giving wide dynamic range fail due to lack of stability of the system at the top or bottom of the range. The present invention overcomes these limitations.
According to the invention, there exists a piezoelectric crystal for generating sonic signals with electronic circuit drive means, containing a switchable current generator in association with resistor means to determine the strength of the sonic signals.
An embodiment of the invention will now be described by reference to Figure 1. 1 is a switchable current generator controlled by a voltage input to terminal 11 whereupon current flows into terminal 12 and out of terminal 13. The current flows through the primary of transformer 4 and through a resistor 3, which may be fixed or variable. The value of resistor 3 determines the voltage swing in the input of the transformer and hence the output voltage applied across the electrodes 51 and 52 of a piezoelactric crystal 5.
As a result of the vibration of the piezocrystal 5 a voltage is generated at electrode 53, and this voltage is fed back to control the switchable current generator, 1, such that the system sustains an oscillation at a frequency determined by the mechanical resonance of the piezocrystal.
The presence of resistor 2 is to ensure that the current generator is switched on when power is first applied between terminals 9 and 10.
Three alternative forms of current switch are shown. 1 consists of an enhancement mode FET, which may be a VMOS device to handle substantial currents. 1A and 1 B show alternative current switches using a single high gain bipolar transistor or a Darlington pair. The presence of the zener diodes 8, 8A and 8B are to clamp the input voltage and hence determine a maximum current flowing through the respective switch. To this end the bipolar versions of the current switch require base resistors 6A and 6B to limit the base current.
The advantage of using a current switch which acts as a constant current generator for large input voltages is that the value of resistor 3 gives good control of the noise output of the piezocrystal over a wide dynamic range. If resistor 3 is variable then this provides means for (a large range of) volume control and a high degree of stability is maintained especially using a VMOS device.
A second embodiment of the invention is shown in Figure 2. This embodiment is essentially the same in operation as the first embodiment except that no transformer is present to step up the voltage to the crystal drive electrodes 512 and 522. This embodiment is useful if very high volume is not required, but has the same attribute as the first embodiment regarding control of the volume by means of resistor 32.
Claims
1. A sound generator containing a piezoelectric crystal driven by electronic circuit means which contains a switchable current generator in association with resistor means to determine the strength of the sonic output.
2. A sound generator as claimed in 1 where the circuit means contains a transformer.
3. A sound generator as claimed in 1 or 2 where the switchable current generator contains a VMOS transistor.
4. A sound generator as claimed in 1 or 2 where the switchable current generator contains a bipolar transistor.
5. A sound generator as claimed in 1 or 2 where the switchable current generator contains a bipolar transistor pair in Darlington configuration.
6. A sound generator containing circuit means described in the accompanying drawings.
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION An Electronic Circuit for Piezoelectric Buzzers The object of the present invention is to provide electronic circuit means to drive a piezoelectric crystal, so producing an audible acoustic signal with a wide dynamic range of noise output. To produce an efficient acoustic generator many different types of electronic circuits have been disclosed, where feedback is taken from a contact to the piezoelectric crystal to the circuit, in order that the crystal oscillates on or close to a resonant frequency of the crystal and its associated diaphragm. In general, any attempt to incorporate a variable resistor into such circuits to provide volume control giving wide dynamic range fail due to lack of stability of the system at the top or bottom of the range. The present invention overcomes these limitations. According to the invention, there exists a piezoelectric crystal for generating sonic signals with electronic circuit drive means, containing a switchable current generator in association with resistor means to determine the strength of the sonic signals. An embodiment of the invention will now be described by reference to Figure 1. 1 is a switchable current generator controlled by a voltage input to terminal 11 whereupon current flows into terminal 12 and out of terminal 13. The current flows through the primary of transformer 4 and through a resistor 3, which may be fixed or variable. The value of resistor 3 determines the voltage swing in the input of the transformer and hence the output voltage applied across the electrodes 51 and 52 of a piezoelactric crystal 5. As a result of the vibration of the piezocrystal 5 a voltage is generated at electrode 53, and this voltage is fed back to control the switchable current generator, 1, such that the system sustains an oscillation at a frequency determined by the mechanical resonance of the piezocrystal. The presence of resistor 2 is to ensure that the current generator is switched on when power is first applied between terminals 9 and 10. Three alternative forms of current switch are shown. 1 consists of an enhancement mode FET, which may be a VMOS device to handle substantial currents. 1A and 1 B show alternative current switches using a single high gain bipolar transistor or a Darlington pair. The presence of the zener diodes 8, 8A and 8B are to clamp the input voltage and hence determine a maximum current flowing through the respective switch. To this end the bipolar versions of the current switch require base resistors 6A and 6B to limit the base current. The advantage of using a current switch which acts as a constant current generator for large input voltages is that the value of resistor 3 gives good control of the noise output of the piezocrystal over a wide dynamic range. If resistor 3 is variable then this provides means for (a large range of) volume control and a high degree of stability is maintained especially using a VMOS device. A second embodiment of the invention is shown in Figure 2. This embodiment is essentially the same in operation as the first embodiment except that no transformer is present to step up the voltage to the crystal drive electrodes 512 and 522. This embodiment is useful if very high volume is not required, but has the same attribute as the first embodiment regarding control of the volume by means of resistor 32. Claims
1. A sound generator containing a piezoelectric crystal driven by electronic circuit means which contains a switchable current generator in association with resistor means to determine the strength of the sonic output.
2. A sound generator as claimed in 1 where the circuit means contains a transformer.
3. A sound generator as claimed in 1 or 2 where the switchable current generator contains a VMOS transistor.
4. A sound generator as claimed in 1 or 2 where the switchable current generator contains a bipolar transistor.
5. A sound generator as claimed in 1 or 2 where the switchable current generator contains a bipolar transistor pair in Darlington configuration.
6. A sound generator containing circuit means described in the accompanying drawings.
GB8028063A 1980-08-30 1980-08-30 Piezoelectric Sound Generator Withdrawn GB2084427A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8028063A GB2084427A (en) 1980-08-30 1980-08-30 Piezoelectric Sound Generator

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB8028063A GB2084427A (en) 1980-08-30 1980-08-30 Piezoelectric Sound Generator

Publications (1)

Publication Number Publication Date
GB2084427A true GB2084427A (en) 1982-04-07

Family

ID=10515739

Family Applications (1)

Application Number Title Priority Date Filing Date
GB8028063A Withdrawn GB2084427A (en) 1980-08-30 1980-08-30 Piezoelectric Sound Generator

Country Status (1)

Country Link
GB (1) GB2084427A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2355546A1 (en) * 2010-02-03 2011-08-10 Delphi Technologies, Inc. Piezo driver with sound pressure level control
CN103456289A (en) * 2013-08-05 2013-12-18 创正防爆电器有限公司 Safety type piezoelectric buzzer

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2355546A1 (en) * 2010-02-03 2011-08-10 Delphi Technologies, Inc. Piezo driver with sound pressure level control
CN103456289A (en) * 2013-08-05 2013-12-18 创正防爆电器有限公司 Safety type piezoelectric buzzer

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Legal Events

Date Code Title Description
WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)