JPS58139524A - Monostable multivibrator - Google Patents

Abstract

PURPOSE:To improve reliability to noises for a monostable multivibrator, by obtaining a long input cut-off time with a low frequency and a short input cut- off time with a high frequency respectively. CONSTITUTION:When an input trigger signal S is supplied to an input terminal IN,a monostable multivibrator FF is set to start charging of a capacitor C. In this case, a monostable multivibrator output terminal OUT is inverted to H when the output Q of the FF is inverted to H since the output of the 1st voltage comparator OP1 is set at H. When the charged voltage reaches V1, the output of the OP1 is inverted to L. At the same time, the output of the OUT is reset to L. When the charging voltage reaches V2, the output of the OP2 is set at H. Thus the FF is reset, and the capacitor C is discharged. Therefore the output voltage V2 of an output pulse integration circuit I is lowered when the repetitive frequency of the signal S is set at a high level. Thus the input cut-off time is decreased; while the input cut-off time is increased due to a high level of the V2 when said repetitive frequency of S is set at a low level.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a monostable multivibrator, the purpose of which is to improve its reliability against noise.

Some conventional monostable multi-bibreaks cut off the input trigger signal only during the output pulse width period, but this cutoff time is constant regardless of the repetition frequency of the input trigger signal, ensuring reliability against noise. It's not enough.

Therefore, the present invention is set by an input trigger signal, inverts the output, and starts charging the time constant determining capacitor and integrating the output, so that the charging voltage of the time constant determining capacitor becomes the first voltage v1. It detects that the voltage has reached the second voltage 2 of the integral value (where V2 > Vl) and stops the charging. The input cutoff time is inversely proportional to the repetition frequency of the input trigger signal, and when the frequency is low, a long input cutoff time is obtained, and when the frequency is high, the input cutoff time is inversely proportional to the repetition frequency of the input trigger signal. In order to obtain a short manual cut-off time and to protect from noise, one embodiment of the present invention will be described below with reference to FIGS. 1 to 8.

In Figure 1, (C) @) is the capacitor and resistor for determining the time constant of the monostable multivibrator, (F, F) is the bistable multivibrator set by the input trigger signal (S), and (Trl) is the bistable multivibrator. is a transistor connected in parallel to the capacitor (C), and the switching circuit 14'ff
How to make a bistable multivibrator (F, F). controlled by (R1) (R2) is the voltage dividing resistor of the power supply voltage B, (OP, ) is the first voltage comparator, and the charging voltage of the capacitor (C) is divided by the voltage dividing resistor (R,)' (R2). It is detected that the pressure rjt pressure ■1 has been reached and the output is “L”.
(G) is an AND gate that detects the logical product of the output Q of the bistable multivibrator (F, F) and the output of the first voltage comparator (OF, AND gate (G) output is connected to monostable multivibrator output terminal (outT) +c. (ca
) (Ra) are a capacitor and a resistor that constitute the output pulse integrator circuit (1) of the monostable multivibrator, and this series circuit has one end to which the power supply voltage B is applied and the other end to which the output pulse of the antagonist 1-(G) is applied. It is connected to the. (OF2) is a second voltage comparator which detects that the charging voltage of the capacitor (C) has reached the output voltage V2 of the output pulse integration circuit (1) and outputs the bistable multivibrator (F, F). ) to reset.

In the state [initial state] immediately before the input trigger signal (S) is input, the bistable multivibrator (F, F) is reset, the output Q is H, the transistor (Try) is ON, and the capacitor C) is being discharged.

Then, when the input trigger signal (S) is input to the input terminal (IN), the bistable multivibrator (F, F) is set, the output Q is inverted to L, and the transistor (Try) is inverted.
is turned off, and the capacitor (C) starts charging via the resistor (R). At this time, since the output of the first voltage comparator (OP□) [Fig. 2 (b)] is at "H", the output Q of the bistable multivibrator (F, F) [
2 (C)] is inverted to “I”, the monostable multivibrator output terminal (O
LJT) [Fig. 2(d)] is inverted to "H". Second
Figure (a) shows the charging waveform of the capacitor (C), and when the capacitor (C) is charged and the charging voltage reaches L% [voltage 1], this is detected and the first voltage comparison is performed. Vessel (o
The output of P, ) is reversed to "L" and the monostable multivibrator output terminal (OUT) returns to "L" at this time.The capacitor (C) is further maintained in a charged state even after the charging voltage reaches Vl. When the charging voltage reaches the output voltage V2 (however, V2 > Vl) of the output pulse integrator circuit Q), this is detected and the output of the second voltage comparator (OP2) is inverted to "H". The bistable multivibrator (
F, F') is reset, the transistor (Try) is turned down, and the capacitor (C) is discharged. Figure 2 (
The time T in e) is the input cutoff time in this case.

Note that when the repetition frequency of the input trigger signal (S) increases, the output voltage v2 of the output pulse integrator circuit (1) decreases and the input cutoff time T becomes short, and when the repetition frequency decreases, the output voltage va increases. Therefore, the input cutoff time T becomes longer. The repetition frequency of this manual trigger signal (S) and the monostable multivibrator output terminal (OLJT)
The relationship between T and input cutoff time T is shown in FIG. In addition,
In order to obtain such a suitable manual cutoff time T, it is necessary that the repetition frequency of the input trigger signal (S) does not change suddenly but gradually. According to the above, since the input cutoff time changes in inverse proportion to the repetition frequency of the input trigger signal, it is possible to more reliably prevent monostable multivibrator malfunctions due to noise than with conventional ones.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of an embodiment of the monostable multivibrator of the present invention, Figure 2 is a waveform diagram of the main part of Figure 1, and Figure 3 is a diagram of the relationship between input trigger signal repetition frequency and input cutoff time. It is. (S)...Manual trigger signal, (C)...Capacitor (capacitor for determining time constant), (I)...Output pulse integration circuit, (OP,)...First voltage comparator, ((
F2)...Second voltage comparator, (F,F)...Bistable multivibrator, (G)...And gate, (
OU'r)...monostable multivibrator output terminal,
('rr+)...Transistor agent Yoshihiro Morimoto

Claims (1)

[Claims] 1. Set by the input trigger signal to invert the output and start charging the time constant determining capacitor and integrating the output, and the charging voltage of the time constant determining capacitor as described in ■ has reached the first voltage v1. detecting that the charging voltage has reached the second voltage V of the integrated value (where V2 > Vl) and terminating the charging; A monostable multivibrator configured so that the time constant determining capacitor is in the initial state.