JPH01314421A - Impulsive noise suppressing circuit - Google Patents

Abstract

PURPOSE:To suppress an impulsive noise by providing a single stable multi-vibrator means, an AND gate means and a delay circuit means, suppressing a pulse signal, which is shorter than the operating time of the single stable multi-vibrator means, and outputting an output signal to an input signal which is longer than the operating time. CONSTITUTION:When a short intermittent signal is inputted to an input terminal IN and this signal is a short pulse to be erased in a time which is shorter than an operating time tau of the single stable multi-vibrator means, a short whisker-shaped pulse is outputted. Since this pulse is absorbed in a delay circuit LG, an output terminal OUT is left to be an L level and nothing is outputted. Next, when the pulse to be longer than the above mentioned tau is inputted, since the input signal of the IN goes to be H, the two inputs of the AND gate go to be H together and the OUT goes to be the H level. Then, the output signal is outputted. This output signal is outputted until there is no input signal of the IN. Accordingly, when a pulse noise suppressing circuit is used for the abnormality display lamp or warning buzzer, etc., of a supervising system, intermittence on the basis of the noise, etc., is erased.

Description

[Detailed description of the invention] [Table of contents] Overview Industrial field of application Conventional technology Problems to be solved by the invention Means for solving the problems (Fig. 1) Working examples (Figs. 2 to 7) Effects of the Invention [(Summary)] The present invention relates to a pulse noise suppression circuit, which aims to generate an output signal by determining pulses shorter than a set time in an input signal as noise, and determining longer pulses as signals, and is capable of suppressing pulse noise. In the circuit, a monostable multivibrator means, an AND gate means in which the input signal of the monostable multivibrator means and one output signal are inputted manually, and a delay circuit means connected to the output side of the AND gate means are provided. This suppresses pulsed signals shorter than the operating time of the monostable multivibrator means, and outputs output signals in response to longer input signals.

[Industrial application field]

The present invention relates to a pulse noise suppression circuit, and more specifically, for example, when used in an abnormal state monitoring system in various devices, when the abnormal state occurs intermittently within a certain period of time, it is regarded as normal. By determining that an abnormality has occurred and outputting an output signal when it occurs continuously for a certain period of time without outputting an output signal, it is possible to distinguish between signals to be monitored and noise, detect them, and issue a display or alarm. This invention relates to a pulse noise suppression circuit.

[Conventional technology]

2. Description of the Related Art Conventionally, abnormal state monitoring systems and the like have been used in electronic devices such as computer systems and communication devices.

In such an abnormal state monitoring system, when an abnormal state such as a failure occurs, it is detected and then displayed with a lamp or with a buzzer.

If an abnormal condition, such as an equipment failure, changes intermittently, it can be detected and displayed as is, or
When an alarm was issued, the indicator lamp would flash and the buzzer would sound intermittently.

[Problem to be solved by the invention]

The above-mentioned conventional devices had the following drawbacks.

In other words, as mentioned above, if the abnormal condition changes intermittently within a short period of time, the indicator lamp will blink or the buzzer will sound intermittently, making it difficult for the person monitoring the situation, and creating an unmistakable defect. there were.

Further, the fault DATA is transmitted from the monitored station to the monitoring station or the interception station.

Each station receiving the faulty DATA checks whether the DATA is correct.

At this time, if the fault DATA is ambiguous, the number of checks increases and the fault confirmation time becomes longer.

The present invention has been made in order to solve these conventional drawbacks. For example, when used in an abnormal condition monitoring system, etc., the present invention can be used to detect abnormal conditions such as the above-mentioned failure condition that change intermittently. The purpose of this is to create a circuit that has a function that considers it to be normal if it is intermittent within a certain period of time, and treats it as abnormal if it is not.

[Means to solve the problem]

In order to achieve the above object, the present invention is as follows.

FIG. 1 is a diagram showing the principle of a pulse noise suppression circuit according to the present invention, and the present invention will be described in detail below based on this diagram.

The input terminal IN is connected to an input terminal T in a monostable multivibrator MM, and also to one input terminal of a two-man power AND gate.

Also, one output η(
It always outputs a high level "H" and outputs a low level "L" when an input signal is input) is connected to the other input terminal of the AND gate.

Further, a delay circuit LG consisting of a resistor R and a capacitor C is connected to the output of the AND gate, and an output terminal OUT is connected to the terminal of the capacitor C.

[Operation] When a short intermittent signal (considered as pulse noise) is input to IN, if this signal is a short pulse that disappears within a time shorter than the operating time τ of the monostable multivibrator, the following will occur. Become.

That is, since Q is inverted to "L" with a little delay from the input signal, during that time both of the two outputs of the AND gate become "H" and a short whisker-like pulse is output.

This whisker-like short pulse is absorbed by the delay circuit LG consisting of a resistor R and a capacitor C, so the output terminal OUT is
Nothing is output as it remains at L'' level.

In addition, with such short pulses (pulses that can be considered as pulse noise shorter than τ), even if Q changes from “L” to “H” after τ time has passed after the pulse disappears, this pulse has already disappeared. When the pulse is gone, IN
becomes "L2 level", and the inputs of the AND gate become "L" and "H".

Therefore, with such a short pulse, nothing is output to OUT (remains at L'' level).

Next, when a pulse longer than τ is input, the stone goes from "Hl to 1L" and returns to "H" again after one hour.

At this time, since the IN input signal is “H”, the AN
The two outputs of the D gates are both 1H", and OUT is at the "H" level, and an output signal is output.

This output signal is output until there is no input signal at IN.

In this way, when the input signal is a short intermittent signal, the output can be suppressed, and when the input signal continues for a long time, the output signal can be sent out.

〔Example〕

Embodiments of the present invention will be described below based on the drawings. Second
The figure shows a pulse noise suppression circuit which is an embodiment of the present invention.

In Fig. 2, MM is a monostable multivibrator, and the monostable multivibrator main body M is composed of an IC.
It consists of an IC, a capacitor CI which is an external component of the MIC (connected to the Cx and Rx/Cx terminals in the MIC), a resistor R1s, a variable resistor RV, a diode D, etc.

The capacitor C, the resistor R1, and the variable resistor RV constitute a time constant circuit that determines the output pulse width of the monostable multivibrator MM.

Therefore, by varying the variable resistor RV, the width of the output pulse can be varied.

Diode D is connected to CX of MIC due to power off state and
This protects the Rx/Cx terminal from overcurrent.

A and B are input terminals of the monostable multivibrator MM, where A is grounded and B is connected to an external input terminal IN to which an input signal is applied.

Further, the input side of the reset circuit RC is connected to +■ (V), and the output side is connected to the clear terminal CL of the monostable multipipe lake MM.

This reset circuit RC is a monostable multipipe lake M
When power is turned on, M is initially set to an initial state, that is, in this example, Q is set to a low level "L" and Q is set to a high level "H".

AND is a two-manual AND gate, one input terminal of which is connected to the Q output terminal of a monostable multivibrator, and the other input terminal connected to input terminal IN.

A delay circuit LG consisting of a resistor R2 and a capacitor C2 is connected to the output terminal of the AND gate, and the terminal voltage of the capacitor C2 is taken out as an output voltage from the output terminal OUT.

FIG. 3 is an operation timing chart of the circuit shown in FIG. 2, and the operation of the circuit shown in FIG. 2 will be explained below based on this diagram.

When there is no signal at the input terminal IN, the signal is Q-“L” (low level) and Q=“H” (high level).

In this state, at time T, a short intermittent pulse signal P+(MM
Assume that a pulse shorter than the operating time τ of τ is input. At this time, the monostable multivibrator MM is triggered at the rising edge of the pulse P and starts operating.

However, since there is some time delay in reversing the output due to this operation, the output Q remains at "H".

Therefore, the AND gate at T has Q="H" and IN
Since the high-level "H" signal of the pulse P, which is the input signal from the circuit, is input, an "H" level signal is outputted.

However, after an extremely short time △T from T1, Q becomes “L”.
At this time, one input of the AND gate becomes L, and its output becomes L level.

Therefore, the output of the AND gate is “
An H'' signal is output, but since this time is extremely short, it is output as a small whisker-like pulse IPI.

This pulse IP is absorbed by the delay circuit LG consisting of the resistor R2 and the capacitor C2 and is therefore not outputted to the output terminal OUT.

Therefore, the output terminal OUT remains at the "L" level.

Next, assume that at time T2, a short intermittent pulse P2 is input again. In this case, the time Tz T+ is shorter than the operating time τ of the monostable multivibrator MM, that is, the operating time determined by the time constants of the capacitor CI, the resistor R+, and the variable resistor RV.

In this state, Q = "L" due to pulse P, so i = "L" without any change, and OUT
remains at “L”.

If such short intermittent pulses pl, Pz .-- are inputted at short intervals thereafter, Q will remain "L" forever.

In the end, the operating time τ(C
Q
remains "L" and is extended by the time period during which the pulses P3 and R2- are present.

After the pulse R2, no short pulse is input, and when a predetermined period of time has elapsed and the time T3 comes, Q=“H” and the original state is restored. ``Then, at time T4, a continuous signal PW with a long pulse width (pulse lasting longer than τ) enters, and when B reaches the ``H level, a small whisker-like pulse IP2 is ANDed in the same way as above. This pulse is output from the gate, but this pulse is also absorbed by the delay circuit, so O
UT remains at "L" level.

Note that also in the case of the pulse PW, the monostable multivibrator MM is triggered only at the rising edge of the pulse PW.

However, at time T, one hour after T4+△T (time determined by the time constant of CIXR15RV), the monostable multivibrator MM performs a reverse operation and returns to the original state with ζ=“H” level. .

At this time, since the AND gate receives an H level signal from Q and an H level signal from IN, its output becomes an H level.

Since this "H level signal" is continuously output until time T6 when the "H" level signal from IN is no longer present, the "H" level signal is output from the output terminal O.
An output signal (output pulse) Po is output to the UT at a continuous "H" level.

The "H" level signal P0 output to the output terminal OUT may be used to operate, for example, an indicator lamp or a warning buzzer of an abnormality monitoring system in various electronic devices.

This makes it possible to suppress signals that are considered to be short intermittent pulse noises, and to respond only to input signals that continue for a certain period of time or more.

FIG. 4 shows an embodiment having an automatic reset function.

The difference from the first basic circuit is that the manual path is added as is to the clear terminal (R), and the input signal wave is blunted by R1 and CI, and the clear signal is added first. .

This monostable multivibrator MM is set to L” clear.

A short pulse of P is now input to the input terminal IN. An "H" level signal enters the rear (R) terminal before the input B of the monostable multivibrator MM, and the monostable multivibrator MM becomes ready for operation.With a delay due to its P+ and C+, the monostable multivibrator MM An input signal is applied to input B of .

As a result, the monostable multivibrator MM operates and the voltage becomes L, but IP occurs due to the delayed operation of the monostable multivibrator MM with respect to the B input. But R2
, C2's delay circuit causes IP to disappear, and the output terminal O
Nothing is output to the UT.

Next, when p becomes "L" level, the monostable multivibrator MM is cleared, so one side of the AND gate becomes "H" and the other becomes "L", and no output appears. R2
The same can be said for

When pw is applied, the monostable multivibrator MM operates in the same manner as P+, and a whisker called IPff is generated, but it disappears due to R2 and C2.

Since Pw is longer than the operating time 2 of the monostable multivibrator MM, an output Po is generated at the output terminal UT.

When Pw disappears, the monostable multivibrator MM is cleared, and the input of the AND gate is “H” and the other is “L”.
” and the output will not be output.

The difference between FIG. 4 and FIG. 1 is that the monostable multivibrator MM is cleared for each input signal, and the operation accumulation time of the monostable multivibrator MM with short pulses is eliminated.
Therefore, the operation of the car stabilizing multivibrator MM becomes faster.

A third embodiment of the invention is shown in FIG.

The difference between FIG. 5 and FIG. 4 is that a buffer gate 1-BU is provided to make the logical values of the input signals uniform.

The buffer gate (non-inverter) BU determines "H" and "L" levels for chatter noise, and the circuit operation is stabilized by having the rubber sofa gate (BUI) judge. (In Figure 4, for the input signal,
There are three input terminals, and noise may be output depending on the dark value of each terminal. ) The operation of the embodiment of FIG. 5 is similar to that of the embodiment of FIG.

FIG. 6 shows a pulse noise suppression circuit according to a fourth embodiment of the present invention, and the same reference numerals as in FIG. 2 refer to the same parts.

In this embodiment, a buffer gate B is provided on the input side of the monostable multivibrator MM, a delay circuit TL consisting of a resistor R3 and a capacitor C3 is provided at its output, and an inverter 11 NV and a resistor R4 are provided at the clear terminal CL. ,
The difference from the one shown in FIG. 2 is that an automatic reset signal generating circuit R3ET consisting of a capacitor C1 and a NAND gate is added.

By providing such a circuit, in the embodiment circuit shown in FIG. 2 above, when a continuous short intermittent signal, that is, a short pulse is input, the operating time of the monostable multivibrator is equal to the number of input pulses. However, in this embodiment, the monostable multivibrator is reset for each input pulse (however, the condition of C:l R3>C4Ra is required).

Therefore, after a series of short intermittent signals (pulses),
Even if a continuous long pulse is input, the time is only one pulse, and the response time becomes faster by that much.

Also, a delay circuit T consisting of a resistor R3 and a capacitor C5
L is a monostable multivibrator MM than the reset signal output from the automatic reset signal generation circuit R3ET.
This is for delaying the input signal applied to input terminal B of.

FIG. 7 is an operation timing chart of the circuit shown in FIG. 6, and the following description will be made based on this diagram.

When a short first intermittent pulse P+ enters the input terminal IN at time T, this pulse P is delayed by the delay circuit TL and enters the input B of the monostable multivibrator MM.

Further, the above pulse P+ is the automatic reset signal generating circuit R3.
It is also input to ET. In this circuit, the pulses P, are N
While inputting to one side (g) of AND, inverter IN
After being inverted by V, it is delayed by a delay circuit consisting of resistor R4 and capacitor C4, and is input to the other NAND (f).

And the output of NAND is monostable multivibrator M
It is input to the clear terminal (CL) of M.

At this time T, the signal of B is low level "L", and f
The signal is at high level "H".

Therefore, the NAND inputs f and g are “Hl” and “H”
Therefore, its output becomes a low level "Lo" and is applied to the clear terminal CL.

Thereafter, at T,1, an extremely short time has elapsed since T, the signal of f becomes "L". Therefore, the output of NAND becomes "H", so CL receives a short pulse CPI.
(The "L" signal generated between TI and T,' is input.

By this pulse CP1, the monostable multivibrator M
Since M is cleared (MM is assumed to be cleared at "L'"), Q remains at "H".

When the B signal becomes "H" at time TI# immediately after TI' (select the time constant as CzRx>C4R4), the monostable multivibrator MM is triggered and starts operating, with a slight delay. Then, the output Q is inverted to "L".

Note that until Q is reversed from H" to "Lo" as described above, the two outputs of the AND gate are both "H", so the output of the AND gate has a short whisker-like pulse.
However, for the same reason as in the case of FIG. 2, nothing is output to the output terminal OUT (OUT remains "Lo").

Next, the operating time τ(CI,
Assume that a second short intermittent pulse P2 is subsequently input within a time period determined by a time constant consisting of R+ and RV.

At this time, as in the above case, a short pulse CP2 is applied to the clear terminal CL, so that the monostable multivibrator is cleared. For this reason, even if pulse noise such as short intermittent pulses PR2, R3-, etc. continuously enters, the operating time τ of the monostable multivibrator does not change.

In other words, after clearing the monostable multivibrator MM when each pulse P2, R2. do not have.

Therefore, at time T3, one hour after the stone becomes "L" immediately after T2'', the stone returns to "H" and recovers.

After T3, the stone becomes "H", but at this time there is no signal at IN and it is "Lo", so the output of the AND gate becomes "Lo" and OU
T is @L” and nothing is output.

It is assumed that after that, at time T4, a long pulse PW (this PW is a pulse longer than the time τ determined by CI, R and RV) is input.

At this time, do T4'' in the same way as when Pl and P2 are entered.
Immediately after, Q becomes "L'", and after r time, at T, Q becomes "
H”.

At this T, since the pulse PW is input to IN, the two inputs of the AND gate both become "H", and the output thereof becomes "H".

Since this "H" output pulse PW continues until time T, when it disappears, the output terminal OUT is T, and then T, and so on.
A pulse P0 of "H" level of 1M is output.

By making an indicator lamp or a buzzer sound in response to this pulse P0, it becomes possible to issue a continuous display or alarm.

In addition, in the above embodiment, a case was explained in which a "L" level signal is applied to the clear terminal of the monostable multivibrator to clear it, but this is determined by the circuit configuration of the monostable multivibrator. ,
“For example, if it is cleared with an H° level signal,
Just connect an inverter to the output of NAND, and
The input of may also be connected not only to Q but also to the Q output via an inverter.

Moreover, the application is not limited to display or alarm circuits of abnormal condition monitoring systems, but can be applied to any type of equipment.

Furthermore, since the operating time τ changes by adjusting the variable resistor RV of the monostable multivibrator, it is also possible to adjust the time width of short pulses that are considered to be pulse noise to be suppressed.

〔Effect of the invention〕

As explained above, the present invention has the following effects.

(1) It is possible to suppress short pulses that are considered pulse noise and prevent them from being output, so for example, when used as an abnormality indicator lamp or alarm buzzer in a monitoring system,
Based on the above-mentioned noise, etc. (intermittent, etc. are eliminated, and the nuisance is eliminated. Also, when transmitting data from the monitored station to the monitoring station or the interception station, ambiguous data transmission is eliminated by suppressing pulse noise. , leading to faster data communication.

(2) It is easy to use because the time width of the short pulse to be suppressed can be easily adjusted.

(3) Both single pulse noise and continuous pulse noise can be effectively suppressed.

(4) In the embodiments shown in Figures 4 to 6, the monostable multivibrator is cleared every time a pulse is input, so the operation time τ is not multiplied by the number of input pulses, and therefore the response time becomes faster.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the principle of the present invention, Fig. 2 is a configuration diagram of an embodiment of the invention, Fig. 3 is an explanatory diagram of the operation of Fig. 2, and Fig. 4 (A) is a second embodiment of the invention. Configuration diagram, Figure 4 (B
) is an explanatory diagram of the operation, FIG. 5 is a configuration diagram of a third embodiment of the present invention, FIG. 6 is a configuration diagram of a fourth embodiment of the invention, and FIG. 7 is an explanatory diagram of the operation of FIG. 6. IN-...Input terminal (signal input terminal) T-Input terminal (input terminal in monostable multivibrator) MM--Monostable multivibrator 0UT-m-Output terminal A N D-A N D gate R--Resistance c - Capacitor RC... - Reset circuit CL - - Clear terminal M I C, - Monostable multivibrator body (I
C) C+, C2, C3, C4-・-': 17 capacitor R
8, R2, R3, R4--Resistor RV---Variable resistance D--Diode LG, TL--Delay circuit I N I--Inverter R3ET--Automatic reset signal generation circuit N A N
D-NAND Gate BU-Buffer Gate

Claims (2)

[Claims] (1) In the pulse noise suppression circuit, a monostable multivibrator means (MM), an AND gate means (AND) inputting an input signal of this monostable multivibrator means (MM) and one output signal, and this Delay circuit means (LG) connected to the output side of the AND gate means (AND) is provided to suppress pulsed signals shorter than the operating time of the monostable multivibrator means and output signals for long input signals. A pulse noise suppression circuit characterized in that: (2) In the pulse noise suppression circuit according to claim (1), delay circuit means (TL) for delaying an input signal is connected to an input terminal in the monostable multivibrator means (MM), and The monostable multivibrator means (M) is connected to the clear terminal of the multivibrator means (MM).
Pulse noise characterized in that an automatic reset signal generating means (RSET) operated by the input signal of M) is connected, and the monostable multivibrator means (MM) is cleared every time an input signal pulse enters. suppression circuit.