GB2104273A - Driving circuit of a piezo-electric buzzer - Google Patents
Driving circuit of a piezo-electric buzzer Download PDFInfo
- Publication number
- GB2104273A GB2104273A GB08217580A GB8217580A GB2104273A GB 2104273 A GB2104273 A GB 2104273A GB 08217580 A GB08217580 A GB 08217580A GB 8217580 A GB8217580 A GB 8217580A GB 2104273 A GB2104273 A GB 2104273A
- Authority
- GB
- United Kingdom
- Prior art keywords
- piezo
- signal
- electric
- circuit
- switch means
- 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.)
- Granted
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
- B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
- B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
- B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
- B06B1/0207—Driving circuits
- B06B1/0223—Driving circuits for generating signals continuous in time
-
- 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
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Apparatuses For Generation Of Mechanical Vibrations (AREA)
- Electromechanical Clocks (AREA)
- Fire-Detection Mechanisms (AREA)
- Piezo-Electric Transducers For Audible Bands (AREA)
Abstract
A driving circuit of a piezo-electric buzzer comprising: a piezo-electric element (7); a series arrangement of a coil (8) and a unilaterally conductive device (9), the series arrangement (8, 9) being connected in parallel with the piezo- electric element (7); first switch means (5) arranged to be operated by a first signal ( phi 1) so as to supply periodically current to the coil (8); and second switch (6) arranged to be operated by a second signal (???2) so as to discharge periodically a voltage which develops across the piezo-electric element (7) in response to the said current. <IMAGE>
Description
SPECIFICATION
Driving circuit of a piezo-electric buzzer
The present invention relates to a driving circuit of a piezo-electric buzzer, to methods of driving such a circuit, and to a timepiece comprising such a circuit.
As will become apparent from the description given below, preferred embodiments of the present invention enable a piezo-electric buzzer to be driven so as to produce a variety of sounds having a variety of tones and qualities. These sounds may be artificial or imitate natural sounds.
Piezo-electric buzzers are used as a source of sound in many consumer products, for example wrist watches and game devices, because of their relatively simple construction and operation.
However, the use of a piezo-electric buzzer is disadvantageous in that the sound volume it produces is relatively small unless it is driven by a high voltage. The resonance frequency is also usually relatively high and sound of low frequency are difficult to produce. As a piezo-electric buzzer requires a high voltage, the output voltage waveform formed after boosting is generally dissimilar to that of the input waveform. As a result, it is difficu It to produce a variety of sounds giving a variety of tones and qualities.
According to a first aspect of the present invention there is provided a driving circuit of a piezo-electric buzzer comprising: a piezo-electric element; a series arrangement of a coil and a unilaterally conductive device, the series arrangement being connected in parallel with the piezo-electric element; first switch means arranged to be operated by a first signal so as to periodically supply current to the coil; and second switch means arranged to be operated by a second signal so as to periodically discharge a voltage which develops across the piezo-electric element in response to the said current.
Preferably the first switch means is connected to a junction between the coil and the unilaterally conductive device and the second switch means is connected to a junction between the unilaterally conductive device and the piezo-electric element.
Preferably the first and second switch means comprise first and second switching transistors.
The driving circuit may be connected to further circuitry for supplying the first and second signals, the arrangement being such that the frequency of the first signal is higher than that of the second signal.
Alternatively, the driving circuit may be connected to further circuitry for supplying the first and second signals, the arrangement being such that the duty cycle of the first signal changes with the passage of time whilst that of the second signal remains substantially fixed, the frequencies of the first and second signals being substantially equal.
According to a second aspect of the present invention there is provided a timepiece comprising a driving circuit as recited above.
According to a third aspect of the present invention there is provided a method of driving a circuit as recited above in which a plurality of pulses are applied to the first switch means between successive pulses applied to the second switch means.
The voltage waveform developed across the piezo-electric element may have a substantially triangular shape.
According to a fourth aspect of the present invention there is provided a method of driving a circuit as recited above in which a pulse is applied to the second switch means a substantially fixed interval of time after the fall of each pulse applied to the first switch means.
The voltage waveform developed across the piezo-electric element may have a substantially rectangular shape.
The present invention will now be described, merely by way of example, with reference to the accompanying drawings, in which:
Figure 1 shows a conventional driving circuit of a piezo-electric buzzer;
Figures 2 and 3 respectively show an input signal for the circuits shown in Figure 1 and the waveform developed across the piezo-electric buzzer thereof by this signal;
Figure 4 shows a further conventional driving circuit of a piezo-electric buzzer;
Figures 5 and 6 respectively show a range of input signals for the circuit shown in Figure 4 and a range of waveforms developed across the piezo-electric buzzer thereof by these signals;
Figure 7shows a driving circuit of a piezo-electric buzzer according to the present invention;;
Figures 8 and 9 respectively show two input signals which may be applied to the circuit shown in
Figure 7, and the waveform developed across the piezo-eiectric buzzer by these signals in a first method of driving the circuit shown in Figure7;
Figures 10 and 11 respectively show a range of first input signals and a second input signal which may be applied to the circuit shown in Figure 7 in a second driving method;
Figure 12 shows a range of waveforms developed across the piezo-electric buzzer by the signals shown in Figure 10 and 11;
Figure 13 shows a first input signal which may be applied to a circuit shown in Figure 7 in a third driving method;
Figure 14 and 16 show alternative forms of a second input signal which may be applied to the circuit shown in Figure 7 in the third driving method; and
Figures 15 and 17 respectively show waveforms developed across the piezo-electric buzzer of Figure 7 when the circuit is driven by the third driving method using the signals shown in Figures 14 and 16.
Figure 1 shows an example of a conventional driving circuit of a piezo-electric buzzer, in which a boosting coil 2 is connected in parallel with a piezo-electric element 1 and is connected to an output terminal of a switching transistor 3.
Figure 2 shows a waveform for an input signal + which is applied to the transistor 3, and Figure 3 shows a voltage waveform V0 which is developed across the piezo-electric element 1. The shape of the voltage waveform V0 is dependent upon the time constant of the circuit, the time constant being determined by a static capacitance C of the piezoelectric element 1 and an inductance L of the bossting coil 2. A specific sound quality is generated in accordance with the frequency spectrum obtained by frequency analysis of the output voltage waveform. Since it is difficult to control precisely the values of the static capacitance C of the piezo-electric element 1 and the inductance L of the boosting coil 2 during the manufacture of these components, there is usually a spread in the values of C and L obtained.
It is, therefore, difficult to make piezo-electric buzzers with identical frequency spectrums and identical sound qualities. The frequency of the input signal Q may be changed to compensate for the spread in C and L but as the values of Land C are fixed, the frequency spectrum cannot be substantially changed.
Figure 4 shows a further conventional driving circuit of a piezo-electric buzzer. This circuit is similar to that shown in Figure 1, but has a reverse-current preventive diode 4 connected between the output terminal of the switching transistor 3 and the boosting coil 2. The diode 4, boosting coil 2, and piezo-electric element 1 thus form a closed loop. A voltage of substantially rectangular waveform is applied across the piezo-electric element 1 by the closed loop. When signals Q as shown in Figure 5 are applied to an input terminal of the transistor 3, the voltage V0 produced from the piezo-electric element 1 is as shown in Figure 6.During the ON-period of the transistor 3, a gradually increasing current, ie, a current in accordance with the time constant curve determined by the inductance Land the resistance value R of the boosting coil 2, flows through the boosting coil 2. At the instant when the transistor 3 is switched OFF the current is Ip, and the magnetic energy accumulated in the boosting coil 2 is 1/2 LIp2.
The magnetic energy transfers from the boosting coil 2 to the piezo-electric element 1 when the transistor 3 is OFF, and the voltage V0 develops across the piezo-electric element 1. Thus, if the capacitance of the piezo-electric element 1 is C, the voltage V0 approximately satisfies the following formula 1/2 Llp2 = 1/2 CVO2 Input signals a, b, c and d shown in Figure 5 respectively correspond to output voltages a, b, c and d shown in Figure 6. By changing the duty cycle of the input signal as shown in Figure 5, the
ON-period of the transistor 3 is changed, and the output voltage V0 can be changed by the relationship indicated by the formula given above.Accordingly, by changing the input signal + in order of aobXcod, a chime sound can be generated.
However, even though the output voltage V0 may be amplified or reduced by changing the duty cycle of the input signal, the duty cycle of the output signal V0 also changes. Since a high harmonic wave component of the signal is changed by a change in the duty cycle, the chime sound produced has an unnatural sound. For example, when the duty cycle of the output voltage V0 is 1/2, a sound with a high harmonic wave component three or five times as high as the frequency of the input signal I is produced, and when the duty cycle is 1/3, a sound with a high harmonic wave component two orfour times as high as the frequency of the input signal Z is produced.
Figure 7 shows a driving circuit according to the present invention. One terminal of a boosting coil 8 and one terminal of a reverse-current preventive diode 9 are connected to an output terminal of a first switching transistor 5. The other terminal of the diode 9 is connected with a power source line via a piezo-electric element 7, and the other terminal of the boosting coil 8 is connected directly with the power source line. One end of the piezo-electric element 7 is connected with an output terminal of a second switching transistor 6. Thus, the coil 8 and diode 9 are connected in a series arrangement and this arrangement is connected in parallel with the piezo-electric element 7. The coil 8 is connected to receive current from the first transistor 5 and the second transistor 6 is connected to discharge the voltage across the piezo-electric element 7.
Figure 8 shows an example of the input signals 81 and 2 which may be applied to transistors 5 and 6 respectively, and Figure 9 shows a voltage waveform applied to the piezo-electric element 7. The input signal pll is modulated at 3KHz and 1 KHz, while the input signal 2 is modulated at 1KHz and is of short pulse width. The transistor 5 is repeatedly switched ON and OFF by the 1 signal whilst the 2 signal is at a low level, ie, when the transistor 6 is
OFF.In a manner simiiar to that described for the conventional circuit shown in Figure 4, an energy of almost 1/2 Llp2 is stored in the piezo-electric element 7 when a peak value of the currentthroughthe boosting coil 8 is Ip. Thus, since an energy of 1/2 Llp2 is stored in the piezo-electric element 7 by one
ON-OFF operation of the transistor 6, an energy of 2 Llp2 is stored by repeating the ON-OFF operation four times. Therefore, the piezo-electric element 7 reaches a voltage of times (= two times) as high as in the conventional circuit.The transistor 6 conducts when the signal 2 is at a high level, and the electric charge stored in the piezo-electric element is discharged so that the voltage across the element drops to 0 volts. Figure 9 shows an output voltage waveform produced across the piezo-electric element 7 by use of the signals , and 2 shown in
Figure 8. By operating the circuit shown in Figure 7 in this manner a higher voltage can be applied to the piezo-electric element 7 than with a conventional circuit.
Figures 10, 11 and 12 show further signals which may be applied to the transistors 5 and 6, and voltage waveforms produced thereby across the piezo-electric element 7. The fundamental frequency of the , signals shown in Figure 10 is 4KHz and their duty cycle reduces in order of aobocHd as shown in Figure 10. The fundamental frequency of the 2 signal is also 4KHz and the signal has a short pulse width as shown in Figure 1 1. A pulse of the Ib2 signal is produced a fixed interval of time after the fall of the , signal, whereby output voltages as shown in
Figure 12 are obtained. The ON-period of the transistor 5 reduces as the duty cycle of the pl signal is reduced, and the output voltage V0 is thereby reduced.However, as shown in Figure 12, the duty cycle of the output voltage V0 does not change since the period from the time the transistor 5 is switched
OFF to the time the transistor 6 is switched ON is fixed.
By using the driving method described above, the valve of the output voltage V0 can be gradually decreased or increased without altering the duty cycle thereof. As a result, the sound voltage can be changed without changing the high harmonic wave component, ie, without changing the tone, and wave envelopes having the desired shape can therefore be generated.
Figures 13, 14 and 15 show further input signals i and 2 which may be applied to the circuit shown in
Figure 7, and voltage waveforms produced thereby.
An input signal i shown in Figure 13 is a steadystate signal of 4KHz. An input signal 2 shown in
Figure 14 is a signal of 250Hz and short pulse width.
By using the signals Idl and 2 a high output voltage of triangular shape, as shown in Figure 15, can be obtained. For example, when a boosting coil which boosts once 5V is used, four times as high voltage (=20V) is obtained with the 4KHz input signal prl.
Since the frequency ratio of the signal pr, (4KHz) to the signal 2 (250Hz) is 16:1, the boosting voltage V0 is Vm6times (= times), as high, by the formula mentioned above. In conventional driving methods, the sound voltage is lowered when a frequency of approximately 250Hz is used, but with the driving method described above, a high voltage may be obtained. An output voltage such as that shown in
Figure 17 can also be obtained by using the input signal i shown in Figure 13 and by using a signal 2 the pulse period of which is suitably changed as shown in Figure 16.
Circuitry for producing the signals i and 2 referred to above, is weil known in the art, and will not, therefore, be described.
It will be appreciated that by using a second switching transistor such as transistor 6 shown in
Figure 7, and by suitably selecting the signals applied to the first and second transistors, the driving circuit described above has the following advantages:
1. A high boosting voltage is obtained since electric energy can be successively stored in the boosting coil.
2. Miniaturization of the boosting coil is possible since the energy stored per boost may be reduced.
3. Rectangular and triangular output waveforms can be produced by a suitable selection of the input signals.
A high boosting voltage is obtained with a low frequency, and a high harmonic wave drive is made with a low cycle wave. A piezo-electric buzzer with high resonance point of several KHz can be driven by a circuit such as that described above. Sounds with a low frequency spectrum for imitating sounds such as that of a car engine or of foot-steps, may also be produced with the circuit described above. The signal shown in Figure 15 is used to imitate the sound ofan engine.
Since electric energy may be successively stored in the boosting coil, a voltage equivalent to that produced in a conventional driving circuit can be obtained even if the boosting capacity per boost is reduced. The amount of energy stored in the boosting coil is determined by its volume and that of any magnetic material used therein, and even if the size of the coil is reduced, or a coil with a low Q-value is used, a high voltage can be obtained.
Furthermore, an output of rectangular waveform in which only the voltage level is changed, as shown in Figure 12, or outputs such as those shown in
Figures 15 and 17 can be obtained by a suitable selection of input signals, and a piezo-electric buzzer which can generate sounds of high quality and sounds with a variety of tones can be produced.
Claims (13)
1. A driving circuit of a piezo-electric buzzer comprising: a piezo-electric element; a series arrangement of a coil and a unilaterally conductive device, the series arrangement being connected in parallel with the piezo-electric element; first switch means arranged to be operated by a first signal so as to supply periodically current to the coil; and second switch means arranged to be operated by a second signal so as to discharge periodically a voltage which develops across the piezo-electric element in response to the said current.
2. A circuit as claimed in claim 1 in which the first switch means is connected to a junction between the coil and the unilaterally conductive device, and the second switch means is connected to a junction between the unilaterally conductive device and the piezo-electric element.
3. A circuit as claimed in claim 1 or 2 in which the first and second switch means comprise first and second switching transistors.
4. A circuit as claimed in any preceding claim connected to further circuitry for supplying the first and second signals, the arrangement being such that the frequency of the first signal is higher than that of the second signal.
5. A circuit as claimed in any of claims 1 to 3 connected to further circuitry for supplying the first and second signals, the arrangement being such that the duty cycle of the first signal changes with the passage of time whilst that of the second signal remains substantially fixed, the frequencies of the first and second signals being substantially equal.
6. A driving circuit of a piezo-electric element substantially as hereinbefore described with reference to and as shown in Figures 7 to 17 of the accompanying drawings.
7. A timepiece comprising a driving circuit as claimed in any preceding claim.
8. A method of driving a circuit as claimed in claim 1 in which a plurality of pulses are applied to the first switch means between successive pulses applied to the second switch means.
9. A method as claimed in claim 8 in which a voltage waveform developed across the piezoelectric element has a substantially triangular shape.
10. A method of driving a circuit as claimed in claim 1 in which a pulse is applied to the second switch means a substantially fixed interval of time after the fall of each pulse applied to the first switch means.
11. A method as claimed in claim 10 in which a voltage waveform developed across the piezoelectric element has a substantially rectangular shape.
12. A method substantially as hereinbefore de scribed with reference to Figures 7 to 17 of the accompanying drawings.
13. In a piezo-electric buzzer comprising at least:a first switching transistor; a closed loop made-up of a boosting coil, a reverse-current peventive diode and a piezo-electric element connected with an
output terminal of said first switching transistor; and
a second switching transistor, a driving method for
said piezo-electric buzzer comprising the steps of:
applying a signal to the first transistor of different
shape from a signal applied to the second transistor;
flowing or stopping the current through the boosting
coil by the first transistor to accumulate electric
charges in the piezo-electric element and to obtain a
high boosting voltage; and operating the second
transistor to discharge the electric charges accumu
lated in the piezo-electric element by its conduct
ance.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP56096137A JPS57210396A (en) | 1981-06-22 | 1981-06-22 | Piezo-electric buzzer driving system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2104273A true GB2104273A (en) | 1983-03-02 |
| GB2104273B GB2104273B (en) | 1984-10-24 |
Family
ID=14156996
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08217580A Expired GB2104273B (en) | 1981-06-22 | 1982-06-17 | Driving circuit of a piezo-electric buzzer |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS57210396A (en) |
| CH (1) | CH653849GA3 (en) |
| GB (1) | GB2104273B (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3328907A1 (en) * | 1983-08-10 | 1985-02-28 | Siemens AG, 1000 Berlin und 8000 München | PIEZOELECTRIC SOUND SWITCHING |
| EP1050860A1 (en) * | 1994-07-29 | 2000-11-08 | Kubota Corporation | Radio wave receiving signaling device |
| GB2388994A (en) * | 2002-05-23 | 2003-11-26 | Gent Ltd | Piezoelectric sounder and drive circuit arranged to reproduce an alarm tone and a voice message |
| EP2362379A1 (en) * | 2010-01-29 | 2011-08-31 | Nohmi Bosai Ltd. | Audible alarm device and fire alarm system including the same |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP6219087B2 (en) * | 2013-07-31 | 2017-10-25 | セイコーインスツル株式会社 | Electronic device, portable device, and control method of electronic device |
-
1981
- 1981-06-22 JP JP56096137A patent/JPS57210396A/en active Pending
-
1982
- 1982-06-17 GB GB08217580A patent/GB2104273B/en not_active Expired
- 1982-06-22 CH CH382582A patent/CH653849GA3/fr unknown
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3328907A1 (en) * | 1983-08-10 | 1985-02-28 | Siemens AG, 1000 Berlin und 8000 München | PIEZOELECTRIC SOUND SWITCHING |
| US4736192A (en) * | 1983-08-10 | 1988-04-05 | Siemens Aktiengesellschaft | Excitation circuit for piezo-electric sound generators |
| EP1050860A1 (en) * | 1994-07-29 | 2000-11-08 | Kubota Corporation | Radio wave receiving signaling device |
| GB2388994A (en) * | 2002-05-23 | 2003-11-26 | Gent Ltd | Piezoelectric sounder and drive circuit arranged to reproduce an alarm tone and a voice message |
| GB2388994B (en) * | 2002-05-23 | 2004-06-30 | Gent Ltd | Improvements in and relating to sound emitting devices |
| EP2362379A1 (en) * | 2010-01-29 | 2011-08-31 | Nohmi Bosai Ltd. | Audible alarm device and fire alarm system including the same |
Also Published As
| Publication number | Publication date |
|---|---|
| CH653849GA3 (en) | 1986-01-31 |
| JPS57210396A (en) | 1982-12-23 |
| GB2104273B (en) | 1984-10-24 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5866969A (en) | Actuating circuit of piezoelectric transformer and actuating method thereof | |
| US6759766B2 (en) | Power supply apparatus and image forming apparatus using the same | |
| US7505600B2 (en) | Processor control of an audio transducer | |
| EP0605752B1 (en) | Switching power supply | |
| US4736130A (en) | Multiparameter generator for ultrasonic transducers | |
| US5566064A (en) | High efficiency supply for electroluminescent panels | |
| KR870011315A (en) | Drive signal generator | |
| JP2707465B2 (en) | Inverter device | |
| US4001816A (en) | Electronic chime | |
| US4996495A (en) | Method and apparatus for generating pulsed RF power | |
| GB2104273A (en) | Driving circuit of a piezo-electric buzzer | |
| US4535458A (en) | Laser apparatus | |
| DE2201156A1 (en) | Electrical signal generator, in particular measuring transmitter | |
| US4567806A (en) | Sound generator | |
| CA2116410C (en) | Electronic bell tone generator | |
| US3873937A (en) | Tone burst generator | |
| JPS6122606Y2 (en) | ||
| KR900006072Y1 (en) | Supersonic vibrator's operation control circuit | |
| JPS5912681Y2 (en) | Waveform memory semiconductor integrated circuit device | |
| SU1310966A1 (en) | High-voltage variable d.c.voltage source | |
| JPH01136193A (en) | Heavy sound driving for piezo-electric buzzer | |
| RU1823112C (en) | Method of control over three-phase valve converter | |
| JPH06153537A (en) | Piezoelectric element driving circuit | |
| SU1220074A1 (en) | Controlled voltage converter | |
| JP2001309651A (en) | Piezoelectric element driving circuit |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |