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JPS5779899

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DESCRIPTION JPS5779899
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top view and a schematic sectional view
showing the configuration of the piezoelectric buzzer, FIG. 2 is a circuit diagram of a piezoelectric
buzzer oscillation circuit in the prior art, and FIG. 3 is an admittance of the piezoelectric buzzer
The figure which shows a characteristic, FIG. 4 is a circuit diagram which shows one Example of
the piezoelectric buzzer oscillation circuit based on this invention. 1 иии Diaphragm, 2 иии First
electrode, 3 ииииии Second electrode, 4 иииииии Piezoelectric ceramic plate, 8 ииииии Transistor, 9 и и и и и и
Piezoelectric buzzer, 10 и и и и и и и и и и.
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the improvement
of a self-oscillation type piezoelectric buzzer oscillation circuit. The piezoelectric buzzer is shown
in Fig. 1 (1), 1 is a thin metal plate etc.-c-c, and the diaphragm 7 is. . Diaphragm, thin
piezoelectric ceramic plates with electrodes facing each other in the thickness direction. 2-4 are
bonded together and comprised. One of the electrodes 8 (not shown) of the piezoelectric ceramic
plate 4 is connected to the diaphragm 1 electrically and in an SW manner, and the other
electrode is divided into the first electrode 2 and the second electrode 3 and provided. There is.
FIG. 2 shows an example of a conventional oscillation circuit using such a piezoelectric buzzer, in
which the emitter, collector and base of the transistor 8 are combined with the diaphragm 1 of
the piezoelectric buzzer 9. First electrode 2. The second electrode 3 is electrically connected to
each other, and the base is appropriately biased by the base resistor 7 and oscillated by
supplying power from the power source 5 between the collector and the emitter through the
collector resistor 6. The operating principle of this oscillation circuit is that, first, since the
transistor 8 is in the ON state by the base resistor 7, the current flows through the transistor 8 at
the same time with the collector and the emitter of the transistor 8 at the first electrode 2 of the
piezoelectric buzzer 9 It takes the same voltage as the voltage. Then, the 1 electric buzzer 9
moves electrically to the input because it moves in, and the second electrode 3 generates a
voltage with a phase difference different from that of the electrode 2 and the 180 ░ I, which is
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the base of In order to swing the potential 3 / -7, the transistor 8 is turned on and off at a
frequency according to the resonance frequency of the piezoelectric buzzer 9 to start oscillation.
Here, in the case of actual oscillation, the piezoelectric buzzer is used by being supported so as to
easily cause resonance by an appropriate means. However, the resonance characteristics of the
second and third harmonics depending on the dispersion of the support or the support means
Will have FIG. 3 shows the resonance characteristics of a typical piezoelectric buzzer, in which
11 is the fundamental resonance frequency, and f2 and 13 are the second and third harmonic
resonance cycle numbers. Since the piezoelectric buzzer has such resonance characteristics, in
the oscillation circuit shown in FIG. When the pull-in of f3 is strong, the oscillation # 1 wave
number may be f2 or f3, and it is difficult to set the oscillation frequency to 11. In particular, the
piezoelectric buzzer is used in the audible range, and when the fundamental frequency f1 is 4
Kkis, it becomes f2-7 about 20 KHz, and it becomes an ultrasonic oscillation, and it can be heard
that the shoulders (0 or fl, f2 и f When the strength is low, for example, it has the problem that it
may occur when it makes noise 4 or not as a phenomenon.
The present invention has been devised to eliminate such conventional problems, and it is an
object of the present invention to provide a piezoelectric buzzer oscillation circuit capable of
causing more stable oscillation. Hereinafter, an embodiment of the present invention will be
described with reference to FIG. As shown in FIG. 4, a capacitor 1 o is inserted between the
second electrode 3 of the piezoelectric buzzer 9 and the diaphragm 1. Assuming that the capacity
of the capacitor 10 is C1, the value 01 is practically heavier than the capacity between the
second electrode 3 and the diaphragm 1, and the car is about ten times as heavy as the car. With
this configuration, among the signals generated from the second electrode of the piezoelectric
buzzer, the frequency of the fundamental wave is lower than the frequency of the harmonics, so
high noise is cut and it becomes easy to stably oscillate at the fundamental frequency. .
Therefore, according to the present invention, by providing a stable piezoelectric buzzer
oscillation 11 path with a simple configuration, the oscillation is -'5.-, and the practicability is
great. .
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