JPH0210956B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an intermittent sound generation circuit.

BACKGROUND ART A wide variety of circuit systems, from simple to complex, have been devised or put into practice as devices or circuits such as so-called buzzers that issue alarms in the form of sound, depending on the type of sounding body. However, for the purpose of warning, most of them have a large volume and therefore generally require a large driving power. However, depending on the purpose and application, it is sufficient to allow a human to sense the occurrence of a certain phenomenon, and therefore an electronic sound generator with low driving power is often sufficient.

The present invention aims to provide a sound generation circuit suitable for such an electronic sound generator, which has sufficient sensitivity and has excellent functions requiring only a microwatt of driving power. The device is characterized by being devised to provide a sensitivity that can withstand practical use by accumulating supplied energy and releasing it all at once as sonic energy. Therefore, the alarm sound in the present invention is an intermittent sound, and from actual experience, there is an advantage that intermittent sounds are more easily perceived and distinguished by humans than continuous sounds.

Until now, a device has been known that utilizes the function of reducing the charging current due to capacitor charging to interrupt and restart continuous oscillation over time (Utility Model Application Publication No. 14131/1983), but this device has not been used. Since there are many elements involved, the circuit inevitably becomes complicated, and intermittent sounds cannot be generated.

The present invention suppresses discharge to the very limit that causes oscillation by utilizing the forward characteristics of diodes, that is, the resistance is large until a certain forward voltage is applied, and the resistance suddenly decreases above a predetermined value. In addition, when oscillation occurs, it can be rapidly discharged and a relatively short oscillation period can be realized, so that a high sounding effect can be provided with a small amount of power consumption.

Hereinafter, the intermittent sound generation circuit of the present invention will be explained in detail with reference to the drawings.

First, the present invention will be explained in principle. First, basic oscillation is obtained by constructing a blocking oscillation circuit using a transistor Q and a small anti-coupled transformer T. However, this is a continuous oscillation and the power consumption is relatively large. Therefore, the continuous oscillation is replaced with intermittent oscillation to operate the sounding body.

FIG. 1 shows a basic circuit example of the present invention, in which one end of the primary winding n ₁ of an anti-coupled small transformer T is connected to the collector of a transistor Q, and one end of the secondary winding n ₂ is connected to the collector of a transistor Q. It is connected to the base via a capacitor Cf, and the other ends of the primary winding n ₁ and secondary winding n ₂ and the emitter of the transistor Q are connected to a power source E, respectively. Further, a resistor R and a capacitor C are connected in series to the power supply E, and the resistor terminal of the capacitor C and the base of the transistor Q are connected via a diode D, and the secondary winding of the transformer T is connected to the base of the transistor Q. A sounding body S having a high impedance is connected between the base side of the line _n2 and the ground. This sounding body S is, for example, a crystal speaker using a piezoelectric effect.

Next, the operation of the above circuit will be qualitatively explained.

Initially, capacitor C is gradually charged by power supply E through resistor R. On the other hand, the base current of transistor Q can also flow through resistor R and diode D, but diode D exhibits a large resistance until the forward voltage applied reaches a certain value, and once that value is exceeded, the resistance decreases rapidly. Since it has non-linear resistance characteristics, if the value of resistance R is appropriately selected,
Oscillation does not occur because the base current is kept small. Moreover, in this case, the base of transistor Q
The base current is further suppressed to a low level due to the emitter-to-emitter forward characteristic, and the oscillation stopped state is maintained.

As capacitor C continues to charge and the terminal voltage of C reaches a certain value (approximately 0.5 volts), diode D
The applied forward voltage exceeds the limit, the resistance drops rapidly, and a base current sufficient to cause oscillation flows, causing the transistor to enter a blocking oscillation state. Once oscillation occurs, the charge on capacitor C rapidly decreases and the oscillation stops. Then, capacitor C starts charging again, and oscillation occurs again after a certain period of time. Thereafter, by repeating this process, oscillation occurs intermittently for a short period of time at a constant cycle. Moreover, in the oscillation state,
Since the charge of the capacitor C flows into the base of the transistor Q only through the diode D, a sufficiently large excitation occurs, and a sufficiently large magnetic energy is stored and released in the transformer T. Therefore, the sounding body S emits an alarm sound that can be sufficiently detected and identified.

Next, other embodiments of the present invention will be described.

2 and 3 are examples of practical circuits that can suitably implement the present invention. In the case of FIG. It also serves as the feedback capacitor Cf in the third
The figure uses an autotransformer as the transformer T.
A sounding body S is connected in parallel with a transistor Q.

For example, if the capacitance of the crystal speaker is about 1000 picofarads, and in the circuit shown in Figure 2, a pulse oscillation of about 2 kHz occurs for about 0.1 seconds approximately every second, and the sounding element S has a voltage of 10 volts. A higher excitation voltage is applied. Therefore, the sensitivity of the sound volume is sufficient for practical use. On the other hand, the power supplied was 16 microwatts since the average current was 20 microamps when the supply voltage was 0.8 volts.

Also, to explain the relationship between the power consumption of this circuit and the sound intensity, the current that flows into the circuit from the power supply when oscillation is stopped is only the charging current to the RC series circuit, which is less than 1 microampere when the supply voltage is 1.0 volts. It is. During oscillation, a current flows in the primary winding _n1 of the transformer T in a pulsed manner, and according to actual measurements, the pulse width is about 20 microseconds, during which the peak current reaches as much as 1 milliampere. However, since the duty factor during oscillation is about 1/10, the average current only during oscillation is about 200 microamperes. Furthermore, since it is an intermittent oscillation and the oscillation time is about one-tenth the rest time, the overall average current is extremely reduced to about 20 microamperes. In other words, the instantaneous drive current for sound generation is 1
It has a large milliampere, so the pronunciation effect is high.
What's more, the average current required is only 20 microamps.

On the other hand, the circuit in Figure 3 is even more sensitive and operates with a supply voltage of 0.6 volts, oscillating at about 2 kHz for about 50 milliseconds every 0.5 seconds, but with a supply voltage of 1.5 volts.
Even in volts, the average current is 7 microamps, so about 10 microwatts of power is plenty practical.

As described above, the sound generation circuit of the present invention consumes only about a microwatt of power, and even if this circuit is connected as a load to other electric circuits, it has almost no effect, and furthermore, due to the occurrence of a certain phenomenon, If connected to a phenomenon/electrical conversion system that generates this amount of power, there will be no need for any batteries for driving, and the occurrence or change of the phenomenon can be detected as an alarm sound without a power supply. Its applications are extremely wide, and it can be used easily and inexpensively as a sensor for various measurements.

[Brief explanation of drawings]

FIG. 1 is a basic circuit diagram showing one embodiment of the invention, and FIGS. 2 and 3 are circuit diagrams showing other embodiments of the invention, respectively. C, Cf...Capacitor, D...Diode,
E...power supply, R...resistance, S...sounding body.

Claims (1)

[Claims] 1. A blocking oscillation circuit consisting of a transistor and a transformer is connected to a high-impedance sounding body that emits a signal sound by oscillation, and a capacitor and a resistor for intermittently operating the oscillation circuit are connected in series to the power supply, and An intermittent sound generation circuit characterized in that the resistance side terminal of this capacitor and the base of a transistor are connected via a diode.