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DESCRIPTION JPS5487084

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DESCRIPTION JPS5487084
Description of the Invention Piezoelectric element driving booster circuit t Piezoelectric element
driving booster circuit using back electromotive force of booster coil In the loop for charging
energy stored in the booster coil to the piezoelectric element, the energy of the booster coil And
a rectifying device is inserted such that the direction of flow to the piezoelectric device is a
forward direction.
Claims
The present invention relates to a piezoelectric element driving step-up circuit using a step-up
coil for a piezoelectric vibrator such as a piezoelectric speaker, and more specifically to a step-up
step; a piezoelectric element effectively utilizing the step-up energy generated in the coil. The
present invention relates to a driving booster circuit. Conventionally, as shown in FIG. 1, in the
piezoelectric element driving booster circuit using the booster coil, the booster coil 1 and the
piezoelectric element 2 are directly connected in parallel, and one side of the booster coil 1 is
connected to the battery. Is connected to the collector of the transistor 5. The transformer 5 is
turned on and off by the signal 1 applied to the base. When the transistor 5 is turned on, current
flows through the booster coil 1 to store energy. Next, when the transistor 5 is turned off,
electrical oscillation occurs between the booster coil 1 and the piezoelectric element 2, and the
collector of the EndPage: 1 transistor 5 outputs a voltage waveform as shown in FIG. 2 (1) K. Is
obtained. However, such a circuit has a first-order defect, in particular, when the period of the
above-mentioned electrical vibration is short compared to the period of the piezoelectric element
drive frequency. The disadvantage is that the energy charged in the piezoelectric element 2 by
the booster coil 1 flows back to the booster coil 1 K, so that the energy stored in the booster coil
1 is not converted into the output from the piezoelectric element 1 efficiently. . As seen from the
output waveform, the fundamental wave component (piezoelectric element drive frequency
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component) is very small compared to the square wave of the duty factor 50 which has the same
peak value voltage, and the boosted voltage is not effectively used. I understand that. In addition,
the output waveform contains a large amount of frequency components (frequency components
of electrical vibration due to the booster coil 1 and the piezoelectric element 2) which have
nothing to do with the driving frequency of one piezoelectric element at all. When driven, good
quality sound can not be obtained. As described above, the fact that the period of the electrical
vibration is short compared to the period of the piezoelectric element drive frequency is a
condition that occurs in many cases. As an example, consider the case where the piezoelectric
speaker used in the alarm wristwatch is driven by the circuit of FIG. Using a piezoelectric speaker
made of a small booster coil with an inductance of 22.6 * and a piezoelectric element with a
capacitance of 1,71 nlF, the frequency of the electrical vibration due to these is 25.4 KH + g. On
the other hand, the piezoelectric speaker driving frequency is normally selected from 21 Km to 4
KH mm in terms of sound quality and the eyelid sensitivity of the human ear. The output in the
case where the drive frequency is 4 KHg is as shown in FIG. 2 (?), and no acoustic output can be
obtained for the divided voltage 9 due to the above-mentioned reason.
According to the present invention, a diode is inserted between the external pressure coil and the
piezoelectric element in rounding to eliminate the above-mentioned drawbacks, and the energy
charged in the piezoelectric element by the boost coil does not flow back to the boost coil again.
It is an object of the present invention to effectively utilize the voltage boosted by the booster
coil. This will be described in detail with reference to the drawings. The first round is a zero shot.
It is an example of one implementation of the side. Reference numeral 7 denotes a boost coil, and
8 denotes a piezoelectric element constituting a piezoelectric speaker. One terminal of the
booster coil 7 and the piezoelectric element 8 is connected to the anode of the battery 10 and the
other terminal of the booster coil 7 is the collector of the transistor 5 and the other terminal of
the piezoelectric element 8 is It is connected to the collector of the transistor 6. A diode 9 is
connected between the transistor 5 and the collector of the transistor 6. Also, a rectangular wave
of the piezoelectric speaker drive frequency is input to the base of the transistors 5 and 60
through the bias resistance 21.22. Also, the emitters of the transistors 5 and 6 are connected to
the cathode of the battery 10. Next, the operation of this circuit will be described. Input terminal
1) When a rectangular wave of audio frequency to be output from the K piezoelectric speaker is
added, the transistors 5 and 6 turn on and off. The mse operation can be divided into a transistor
5.60 on-period, an on-off off-time transient state, and a subsequent off-period. First, an operation
in a state where the transistors 5 and 6 are turned on will be described. When the transistor 5 is
turned on, a voltage substantially equal to the voltage of the battery 10 is applied to the booster
coil 7. As a result, as shown in FIG. 4 (vague), a current which gradually increases with a time
constant determined by the inductance and resistance of the booster coil 7 flows through the
booster coil 7, and magnetic energy is accumulated in the coil. On the other hand, when the
transistor 60 is turned on, the potential difference between the two piezoelectric elements 80 is
fixed to a value substantially equal to the voltage of the battery 10. Next, the operation when the
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transistor 5 and transistor 6 change from on to off will be described. By turning off the
transistors 5 and 6, the series circuit of the booster coil 7, the diode 9 and the piezoelectric
element 8 is disconnected. At this time, a counter electromotive voltage is generated in the
direction in which current flows continuously in the same direction as 9:00 when the booster coil
7KFi and the transistors 5 and 6 are turned on, and the diode 9 is turned on. As a result, current
flows from the booster coil 7 through the diode 9 to the piezoelectric element 8. This state is that
the piezoelectric element 8 can be regarded as a capacitor, so that boosting; InEndPage of the
coil 7: capacitance of the piezoelectric element 8 It is considered to be free vibration due to
While the potential of the diode 9ga of the booster coil 7 is rising, the diode 9 continues to be
turned on to continue charging the piezoelectric element, and the diode of the booster coil 7!
When the potential on the side reaches the maximum and starts to fall, the diode 9 is turned off
and charging of the piezoelectric element is stopped. At this time point, ignoring the losses of the
boost coil 7, the diode 9 and the piezoelectric element 8, all the energy stored in the boost filter
at the moment when the transistors 5 and 6 turn off is transferred to the piezoelectric element 8
in a good state. is there. By such operation, in the piezoelectric element 8, a boosted voltage is
obtained according to the energy stored in the booster coil 7 during the ON period of the
transistors 5 and 60. Therefore, assuming that the boosted voltage through which the inductance
of the inductor 7 flows through the booster coil 7 at the moment when the L1 transistors 5 and 6
are turned off and the capacitance of the 11P1 piezoelectric element S is 01 is V. The following
equation (1) can be obtained by modifying the equation (1). ?????????????
??????????? ?? Substituting -IL5 ?, Vs = 41 и 8 v и и и и approximately agrees with
the experimental boosted voltage 40.5 v. The relationship between 1A and V и is shown in FIG.
The straight line color indicates the equation (2), and l1 uls is obtained by experiment. From
these data, it is confirmed that the equation (1) holds. Next, the operation of the subsequent off
period of the transistors 5 and 6 will be described. During this period, the transistors 5 and 6 are
turned off) and the diode 9 is also turned off, so that the piezoelectric element 8 is completely
separated. Although the voltage of the piezoelectric element 80 changes slightly due to the
shadow ILK of the vibration of the piezoelectric element B, the voltage within the piezoelectric
element 8 keeps the boosted voltage. . By the operation as described above, a rectangular wave
output waveform as shown in FIG. 4 (?) is obtained at the collector of the transistor 6. FIG. 5 is
another circuit example according to the present invention. This circuit is completely the same as
the circuit of FIG. 5 except that the voltage applied to the booster coil 12 when the transistor 11
is turned on is smaller than that of the circuit of FIG. 3 by the forward voltage drop of the diode
14. Do the same. ???? Even if the piezoelectric element 8 is connected in parallel between
the collector and the emitter of the transistor 6 in FIG. 5 and the piezoelectric element 13 is
connected between the collector and the insulator of the transistor 11 in FIG. A square wave
output can be obtained with a duty equal to the duty of the input signal.
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Furthermore, as shown in FIG. 6, if the element inserted between the boosting and the
piezoelectric element has diode characteristics such as between the base and the emitter of the
transistor or between the pace and the collector, the same operation is performed. It can be
carried out. Although all the bipolar transistors are used as the switching elements in the circuit
shown in the figure, the same operation can be carried out using other switching elements (ym,
etc.). As described above, in the circuit according to the present invention, the output waveform
can be made into a rectangular wave, and the duty can be easily changed. Therefore, by setting
the duty to approximately 50-K, it is possible to obtain the maximum output for the same
boosted voltage, and to minimize the power consumption for obtaining the same output.
Therefore, the booster circuit according to the present invention can be The effect of using it as a
step-up circuit such as a piezoelectric speaker for alarm of a wristwatch which requires low
power consumption is great.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram of a voltage boosting circuit for
driving a piezoelectric element according to a conventional example, and the second factors (1)
and (1) are diagrams showing input voltage waveforms and output voltage waveforms of the
circuit of FIG. The voltage-voltage drive circuit according to the present invention, FIG. 4 (1)% (1),
reconnaissance is the input voltage waveform of the circuit shown in FIG. 115, the current
waveform flowing through boost poil EndPage: 37, the output waveform FIG. 5, FIG. 5, and FIG. 6
are circuit diagrams showing other embodiments according to the present invention, and FIG. 7
is a boosting characteristic diagram of the circuit of FIG. 1, 7, 12, 16 и и и и и и и и и и Boosting coil 2.8,
15. 17. и и и и и и и и и и Piezoelectric element 5.5, 4.11.18.19-и и и иии Transistors 4, 10, 15, 20 ииииииии
Battery и 2.14 и и и и и и и и и и и и и и и и и и и и и и и и и и It is a bias resistance. Above, ...)). ?j ? ? ? ? ? ?
? ? 1 1 1 ? 1 3 3 3 4 5 5 r 5! UEndPage: 4 7 7 towns ^ ^ Procedure amendment
(spontaneous) 1959 7 ++ ": 13 'Patent Office Director Yoshiya Kumagai 1 display case Showa
Patent No. 154,676 Patent No. 2 invention title 2 invention Name of Piezoelectric element drive
booster circuit 3 correction 4 old agent contact point 563-2111 extension 223-6 charge for
Hakuya 7, correction contents as shown in the attached sheet.
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