JPS5824510Y2 - monostable multivibrator - Google Patents

Description

[Detailed description of the invention] This invention relates to a retriggerable monostable multivibrator, which simplifies the configuration to make it cheaper and smaller, and also quickly discharges the charge in the capacitor using a discharging diode to trigger the retrigger. Shorten the time it takes to perform <
Furthermore, the present invention aims to provide a monostable multivibrator that operates even with a very small trigger signal.

Next, this invention will be explained with reference to drawings showing one embodiment thereof.

As shown in the drawing, the base of a PNP switching transistor 20 is connected to the trigger signal input terminal 1 through which a negative voltage pulse trigger signal is input via a 0.001 μF coupling capacitor 9. The input terminal of an inverter 3 made of a TTL integrated circuit 1 having a model number 5N7404 is connected to the collector, and a resistor 7 of 2200 for collector load is provided between the collector of the transistor 2 and the ground point.

Further, the emitter of the transistor 2 is connected to the DC power supply terminal 8, and a base bias resistor 6 of 270Ω is connected between the base of the transistor 20 and the DC power supply terminal 8.
is provided.

And before the trigger signal is input, transistor 2
5■ positive power supply voltage + of terminal 8 via resistor 6 to the base of
Vcc is applied, the voltage at the base of the transistor 20 is held at a high level "H", the transistor 2 is held non-conductive, the collector of the transistor is held at the ground level, that is, the low level "at L", and the voltage of the inverter 3 is held at a low level "at L". The output signal voltage output from the output terminal is at a high level °°H”
is maintained.

Further, a resistor 5 for a time constant of Ω is connected to the base 18 of the transistor 2, and a capacitor 4 for a time constant of 47 μF is provided between the output terminal of the inverter 3 and the resistor 5. 5 and the connection point of capacitor 4,
between trigger signal input terminal 1 and trigger signal input terminal 1.
A discharging diode 10, model number 181588, whose cathode is connected to is provided, and before the trigger signal is input, the high level °°H" output from the output terminal of the inverter 3 is connected to one end of the capacitor 4. At the same time as the signal voltage is applied, the positive power supply voltage +Vccz of the terminal 8, that is, the high level "H" voltage is applied to the other end of the capacitor 4 via a series circuit of resistors 5 and 6.

Next, when a trigger signal of a negative voltage pulse is input to the trigger signal input terminal 1, the voltage at the base of the transistor 20 decreases, and the trigger signal triggers the transistor 2 to conduct. Then, a current flows from the terminal 8 to the resistor 7 via the emitter and collector of the transistor 2, and the voltage at the collector of the transistor 2 becomes lower than the threshold voltage of the inverter 3. The output signal voltage of the inverter 3 changes from the high level "H" to the low level "L".

Note that the threshold voltage of inverter 3 is 1.2V.
It is set to ~1.4■.

When the output signal of the inverter 3 becomes low level "L", current flows from the terminal 8 to the capacitor 4 via the emitter and base of the transistor 2 and the resistor 5, and the capacitor 4 starts to be charged. Although the voltage starts to rise gradually, it does not rise to the voltage at which transistor 2 becomes conductive, so transistor 2 continues to conduct.

Furthermore, charging of capacitor 4 progresses, and transistor 2
The voltage at the base of transistor 2 increases, and the voltage at the emitter of transistor 2,
At the moment when the current flowing through the resistor T through the collector decreases and the voltage at the collector of transistor 2 drops below the threshold voltage of inverter 3, the output signal voltage of inverter 3 changes from low level ``L'' to high level. t1H'', the voltage at the base of transistor 20 rises to a voltage that makes transistor 2 non-conductive, and transistor 2 flips from conducting to non-conducting.

Then, during the conduction period of the transistor 2, a low level "L" rectangular wave pulse is output from the output terminal of the inverter 3,
Since the conduction period of the transistor 2 is mainly set by the capacitance of the capacitor 4 and the resistance value of the resistor 5, the pulse width of the rectangular wave pulse is determined by the capacitance of the capacitor 4 and the resistance value of the resistor 5.

Furthermore, when the trigger signal is input again after the transistor 2 is inverted to non-conducting, the diode 10 becomes conductive due to the negative voltage trigger signal, and the charge in the capacitor 4 is
It is quickly discharged through the discharge path of the diode 10, and the voltage at the base of the transistor 2 drops again, causing the transistor 2 to switch from non-conducting to conducting again, allowing for quick re-triggering and the same operation as described above. , while the voltage at the collector of the transistor 2 is higher than the threshold voltage of the inverter 3, an output signal voltage of a low level "L" is output from the output terminal of the inverter 3, and then, by charging the capacitor 4, the voltage of the transistor 2 increases. The voltage at the collector drops below the threshold voltage of the inverter 3, and the transistor 2 is reversed from conductive to non-conductive.

From then on, by the same operation, every time a trigger signal is input, transistor 2 conducts for a predetermined period of time, and a rectangular wave pulse of low level "L" is output from the output terminal of inverter 3. Works as a multi-vibrator.

Note that since the trigger signal is input to the base of the transistor 2 without passing through the diode 10, the transistor 2 can be accurately triggered to conduct and operate even when the trigger signal is very small.

As described above, the monostable multivibrator of this invention can provide a retriggerable monostable multivibrator with a simple circuit configuration, and can be applied to, for example, chattering prevention circuits and timers for key manual operation. In some cases, it can be made inexpensive and compact, and the discharge diode can quickly discharge the charge in the capacitor, shortening the time until retriggering can be performed, and furthermore, the trigger signal can be It is possible to provide a monostable multivibrator that can be operated by accurately triggering conduction of a transistor even when the amount is small, and has excellent practical effects.

[Brief explanation of drawings]

The drawing is a wiring diagram of one embodiment of the monostable multivibrator of this invention. 1...Trigger signal input terminal, 2...Transistor, 3...Inverter, 4...
・Capacitor for time constant, 5... Resistor for time constant, 10... Diode for discharge.

Claims (1)

[Scope of utility model registration request] a PNP transistor whose base is input with a trigger signal from a trigger signal input terminal to trigger conduction; an inverter whose input terminal is connected to the collector of the transistor; and a time constant resistor connected to the base; a time constant capacitor provided between the resistor and the output terminal of the inverter and charged with a current through the resistor due to conduction of the transistor to cause the transistor to conduct for a predetermined period; and a connection point between the resistor and the capacitor. and a discharge diode that is provided between the trigger signal input terminal and the trigger signal input terminal and forms a discharge path for the capacitor when the trigger signal is input.