JPS5929397Y2 - monostable circuit - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field This invention relates to a monostable circuit that converts an input signal into an output signal of a predetermined time width.

(B) Prior Art A conventional monostable circuit is usually constructed as shown in FIG.

That is, it consists of first and second transistors 11, 12, a capacitor 13, and resistors 14-16.

It is provided with two power supply terminals to which DC voltage is applied, an input terminal, and an output terminal.

Normally, transistor 11 is off, transistor 12 is on, and capacitor 13 is charged.

When an input signal is input, transistor 12 is turned off through capacitor 13, and as a result, transistor 11 is turned off.
is turned on.

In this state, the capacitor 13 is discharged, and after a predetermined period determined by the values of the capacitor 13 and the resistor 15, the transistor 12 is turned on and the initial state is returned again.

Therefore, since the capacitor 13 is normally charged,
If noise occurs in the power supply, it will malfunction, and furthermore, when the power is initially turned on, the transistor 11 may be on and the transistor 12 may be off, resulting in an erroneous output.

Another drawback is that it is susceptible to fluctuations in power supply voltage and changes in ambient temperature.

Furthermore, when actually using this monostable circuit, there is the inconvenience of having to cut the signal line connecting the input side equipment and the output side equipment and connect the input terminal and output terminal to each of them. be.

(c) Purpose This invention is resistant to power supply noise, eliminates problems during initial power-on, operates stably against power supply voltage fluctuations and ambient temperature changes, and also allows signal lines to be disconnected during use. The purpose is to provide a monostable circuit that is unnecessary and easy to use.

2) Construction The monostable circuit according to this invention consists of 2
an input/output terminal that serves as both an input terminal and an output terminal; a reference voltage generation circuit that is connected to the power supply terminal and generates a reference voltage from the DC voltage; and one of the two power supply terminals. An integrating circuit is connected between the input and output terminals and has a resistor and a capacitor connected in series, and its collector-emitter path becomes conductive or non-conductive depending on the difference between the integrated voltage generated at one end of this capacitor and a reference voltage. a first transistor whose collector-emitter path is connected between the input/output terminal and the other power supply terminal, and a base current is supplied through the conductive collector-emitter path of the first transistor; The collector
and a second transistor whose emitter path is conductive.

(e) Examples FIG. 2 shows a first embodiment of this invention.

In this figure, an integrating circuit formed by connecting a resistor 24 and a capacitor 23 in series is connected between a power supply terminal of power supply voltage Vcc and an input/output terminal.

The input/output terminals are used for both signal input and output.

The integrated voltage generated at one end of this capacitor 23 is applied to the base of the first transistor 21.

The emitter of this transistor 21 is connected to the power supply terminal of the power supply voltage Vcc via a resistor 25 to be supplied with a reference voltage Vs, and the collector is connected to the base of the second transistor 22.

The collector-emitter path of this transistor 22 is connected between the input/output terminal and the power supply terminal of the common voltage C.

A load 26 is connected between the input/output terminal and the power supply voltage Vcc line as shown by the dotted line.

Next, the operation will be explained with reference to FIG.

When there is no input signal, the transistor 22 is in an off state and the capacitor 23 is in an uncharged state.

At this time, the input/output terminals are at the power supply voltage ■c.

When an input signal having the same potential as the common voltage C arrives, the base voltage VBI of the transistor 21 is lowered to the common voltage C through the capacitor 23, so that it becomes lower than the emitter voltage and the transistor 21 is turned on.

Then, current flows to the base of transistor 22, so
Even if the transistor 22 is turned on and the input signal is terminated (that is, even if the input signal becomes a high potential), the output signal remains low (Lo
It remains at the w level (in this case, the common voltage C).

In this state, the capacitor 23 is charged through the resistor 24, and the base voltage VB1 of the transistor 21 increases.

When the base voltage VB1 becomes higher than the base-emitter voltage of the F transistor 21, the transistor 21 is turned off, and therefore the transistor 22 is also turned off. The output signal is H (High
h level (in this case, power supply voltage Vcc).

After the transistors 21 and 22 are turned off, the charge that has been charged in the capacitor 23 until then is reduced to the power supply voltage Vcc.
is discharged through a load 26 and a resistor 24 connected between the line and the input/output terminal.

The time width T of the output signal is given by the following formula.

T=R4・C3・1n・■cc/(■ee-■R)R4
; resistance value C3 of the resistor 24; capacitance value of the capacitor 23. Therefore, the time width T of the output signal can be arbitrarily set by changing the threshold voltage ■□.

Therefore, instead of connecting the emitter of the transistor 21 to the power supply voltage Vcc terminal via the resistor 25 to provide the power supply voltage Vcc as the reference voltage Vs, a reference voltage generation circuit such as a resistor voltage divider circuit is connected to the power supply terminal ( For example, the reference voltage Vs may be changed (as in the second and third embodiments described later).

In this case, the time width T can be shortened as indicated by the dotted line in FIG. 3 depending on the value of the reference voltage Vs.

Next, a second embodiment will be described with reference to FIG.

In this actual case, two transistors 41 and 42, and an integrating circuit consisting of a capacitor 43 and a resistor 44 are provided as in the first embodiment.

Furthermore, a diode 48 is connected in parallel to the resistor 44, and a voltage divider circuit consisting of resistors 45 and 46 is connected between the power supply terminal of the power supply voltage Vcc and the collector (input/output terminal) of the transistor 42, and the emitter of the transistor 41 is connected as a reference. Voltage Vs
A resistor 47 is connected between the base and emitter of the transistor 42.

Diode 48 forms a discharge circuit for capacitor 43 when transistor 42 is turned off, causing rapid discharge.

The resistor 47 is for stabilizing the operation of the transistor 42.

In this second embodiment, the reference voltage Vs applied to the emitter of transistor 41 (when transistor 42 is on) is: Vs=Vcc-R6/(R5+R6) R5, R6; with the resistance value of resistor 45.46. Therefore, the threshold voltage VFL is VB = Vcc-R6/(R5+R6)VBEIVBE
t; Becomes the voltage between the base and emitter of the transistor 41, so select the value of the resistor 4546 appropriately! An arbitrary time width T can be obtained.

If it is necessary to separate the input terminal and output terminal, a differentiating circuit 49 is used as shown by the dotted line in FIG.

FIG. 5 shows a third embodiment.

In this embodiment, as in the previous embodiment, two transistors 51 and 52, an integrating circuit consisting of a capacitor 53 and a resistor 54, a voltage dividing circuit consisting of resistors 55 and 56, an operation stabilizing resistor 57, and a discharge A diode 58 is provided.

The emitter of the transistor 51 is connected to an integrating circuit, and the base is connected to a voltage dividing circuit, and a reference voltage Vs is applied to the base from the voltage dividing circuit.

Further, an emitter-collector path of a transistor 52 is inserted between the integrating circuit and the power supply terminal of the power supply voltage Vcc.

The switch 59 is for inputting an input signal.

Next, regarding the operation of the embodiment shown in FIG. 5, FIG.
This will be explained with reference to B.

FIG. 6A shows the case where the on time of the switch 59 is shorter than the output time of the monostable circuit, and FIG. 6 B shows the case where the on time of the switch 59 is longer than the output time of the monostable circuit. be.

When the switch 59 is turned on, the reference voltage Vs is applied to the base of the transistor 51 from a voltage dividing circuit made up of resistors 55 and 56.
is given, and since the capacitor 53 is not charged at this time, the emitter voltage of the transistor 51 is low, and as a result, current flows from the base to the emitter, and the transistor 51
turns on.

When the transistor 51 is turned on, a collector current flows, so a base current flows to the transistor 52, and the transistor 52 is turned on.

The voltage of the output signal is increased by turning on the switch 59.

At this time, the capacitor 53 is connected to the switch 5 which is on.
9 and the transistor 52, and is then charged by the current that passes through the resistor 54.

As the capacitor 53 is charged, the emitter voltage and base voltage of the transistor 51 rise accordingly (the base voltage is higher than the emitter voltage by the base-emitter voltage of the transistor 51).

The operations up to this point are the same in both FIGS. 6A and 6H.

In FIG. 6A, switch 59 is turned off shortly thereafter, but since transistor 52 is on, capacitor 53 is similarly charged through transistor 52, and the emitter voltage and base voltage of transistor 51 are also the same. It continues to rise.

When the increased base voltage reaches the reference voltage Vs, the base voltage no longer increases, and a reverse voltage is generated between the emitter and the base, turning off the transistor 51 and causing no collector current to flow through the transistor 52.
loses base current and turns off.

Therefore, the voltage of the output signal becomes low from this point on.

In the case of FIG. 6B, the transistors 51 and 52 are turned off through the same process as above, but since the switch 59 is still on when the transistor 52 is turned off, the voltage of the output signal is the same as that of the transistor 52. The capacitor 53 is connected to the power supply voltage Vc through the switch 59.
Continues to be charged until c.

Therefore, as the charging voltage of capacitor 53 becomes higher, the emitter voltage of transistor 51 becomes higher.

The base voltage of the transistor 51 remains at the reference voltage Vs, and a reverse voltage is applied between the emitter and base of the transistor 51.

When the switch 59 is turned off in this state, the voltage of the output signal immediately becomes low because the transistor 52 is already turned off.

In the second and third embodiments (FIGS. 4 and 5), the time width T of the output signal is determined in the same manner as in the first embodiment (FIG. 2).

(f) Effect In the monostable circuit according to this invention, the capacitor of the integrating circuit is in an uncharged state until the input signal arrives, and starts charging when the input signal arrives, so it is resistant to power supply noise. It is stable and does not generate erroneous outputs when the power is initially turned on or when a power outage is recovered, so other equipment can be prevented from malfunctioning.

Furthermore, it operates by comparing the charged voltage of the capacitor of the integrating circuit with the reference voltage, but since the voltage applied to the integrating circuit and the voltage used to create the reference voltage are a common power supply voltage, fluctuations in the power supply voltage Operation stability can be ensured against changes in temperature and ambient temperature.

In addition, since the input and output terminals are combined into one, the wiring effort of cutting the signal line and connecting the input and output terminals can be omitted, making it extremely convenient in actual use. It has become.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a conventional monostable circuit, Fig. 2 is a circuit diagram showing a first embodiment of this invention, Fig. 3 is a time chart showing the operation of Fig. 2, Figs. Figure 5 is the second
The circuit diagrams of the third embodiment and FIGS. 6A and 6B are time charts for explaining the operation of the circuit of FIG. 5. 11.12, 21.22, 41, 42, 51. 52...Transistor, 13,23,43.5
3...Capacitor, 14-16 24 25
44t S t~47,
54-57...Resistance, 48.58...
Diode, 49... Differential circuit, 59...
...Switch, Vcc...Power supply voltage, Vs...
...Reference voltage, C...Common voltage, VBl.
...Base voltage of transistor 2141.

Claims (1)

[Scope of utility model registration request] two power supply terminals to which a DC voltage is applied; an input/output terminal that serves as both an input terminal and an output terminal; a reference voltage generation circuit connected to the power supply terminal and generating a reference voltage from the DC voltage; An integrating circuit is connected between one of the power supply terminals and the input/output terminal, and has a resistor and a capacitor connected in series. a first transistor whose collector is conductive or non-conductive;
An emitter path is connected between the input/output terminal and the other power supply terminal, and when a base current is supplied through the collector-emitter path of the first transistor, the collector-emitter path becomes conductive. A monostable circuit comprising two transistors.