JP6218190B2 - Abnormality detection circuit for communication surge protection element - Google Patents

Description

  The present invention relates to an abnormality detection circuit for a surge protection element for communication that is connected to various communication lines and protects communication equipment and instrumentation equipment from lightning surge current, and more specifically, detects a short-circuit failure of a surge protection element. The present invention relates to a possible abnormality detection circuit.

FIG. 2 is conventionally known as a communication surge protection circuit.
In FIG. 2, 10 is a pair of communication lines having input terminals L1, L2 and output terminals T1, T2, and R1 is a current limiting resistor (positive characteristic thermistor) connected between the input terminal L1 and the output terminal T1. , 21 is a lightning protection element such as a gas-filled discharge tube (GDT) connected between the input terminals L1 and L2 and the ground terminal E, and 31 is an avalanche breakdown connected between the output terminals T1 and T2. A surge protection element such as a diode (ABD).
Although not shown, between the output terminals T1 and T2, communication equipment and instrumentation equipment to be protected from lightning surge are connected.

  In addition to the avalanche breakdown diode (ABD), a varistor such as a metal oxide varistor (MOV) or a thyristor such as a surge protection thyristor (TSS) may be used as the surge protection element 31. Further, a current limiting resistor R2 (positive characteristic thermistor) may be connected between the input terminal L2 and the output terminal T2.

  In the surge protection circuit of FIG. 2, the lightning surge current flowing between the communication line 10 and the ground (between the terminals L 1 -E or L 2 -E) is absorbed by the lightning arrester 21, and between the communication lines 10. Since the lightning surge current flowing between the terminals L1 and L2 is mainly absorbed by the surge protection element 31, it is possible to prevent the lightning surge current from flowing into the communication device or the like.

In this type of communication surge protection circuit, for example, lightning surge current repeatedly flows in the surge protection element 31 or the characteristics deteriorate with age, so that leakage current increases and heat is generated. It may cause destruction and short circuit failure.
For this reason, various abnormality detection circuits for detecting a short-circuit failure of the surge protection element 31 have been conventionally provided.

  For example, FIG. 3A shows a first prior art in which leakage current is detected by applying a test DC voltage from the checker 40 via the diodes D5 and D6 to the surge protection element 31, and FIG. 3 is a second prior art for detecting a leakage current by applying a DC voltage to the surge protection element 31 via the diodes D5 and D6 by a series circuit of the DC power supply B and the light emitting diode LED, as shown in FIG. It is possible to detect a short circuit failure of the surge protection element 31 by the indication value of the checker 40 or the lighting of the light emitting diode LED of FIG.

On the other hand, as the third prior art, the invention shown in FIG. 2 of Patent Document 1 (patented invention by the present applicant) is already known.
In the third prior art, a semiconductor switch element such as a thyristor or a transistor is turned on by using a leakage current that flows when a DC voltage is applied to the surge protection element as a trigger, and a light emitting element connected to the semiconductor switch element is turned on. Further, the alarm is output by operating the relay by the abnormality detection current that flows when the semiconductor switch element is turned on.

FIG. 4 is a circuit diagram when the third prior art is applied to the circuit shown in FIG.
In FIG. 4, DB is a diode bridge composed of diodes D <b> 1 to D <b> 4, and a surge protection element 31 that is an abnormality detection target is connected between its output terminals. A series circuit of the DC power source B and the abnormality detection unit 50 is connected to both ends of the surge protection element 31 via diodes D5 and D6.
Here, as described above, the abnormality detection unit 50 has a function of turning on the semiconductor switch element using the leakage current flowing through the surge protection element 31 as a trigger to drive the light emitting element and the relay.

Japanese Patent No. 5697263 (Claims 1, 2, FIG. 1, FIG. 2, etc.).

  However, since most of the lightning surge current usually flows between the communication line 10 and the ground (between the terminals L1-E or between the terminals L2-E), when the lightning arrester 21 in FIG. In this case, no lightning surge current flows through the surge protection element 31 between the communication line 10 and the ground. For this reason, the short circuit failure of the surge protection element 31 is less likely to occur, and there is a problem that the abnormality detection unit 50 cannot detect the abnormality of the surge protection element 31.

  Accordingly, the problem to be solved by the present invention is that even if the lightning arrester is open-circuited due to a lightning surge current flowing between the communication line and the ground, the communication line and the ground are connected via the communication surge protection element that is an abnormality detection target. It is an object of the present invention to provide an abnormality detection circuit for a communication surge protection element that can reliably detect a short circuit failure of the surge protection element by forming a lightning surge current path.

In order to solve the above-mentioned problem, the invention according to claim 1 is characterized in that a first lightning arrester is connected between a pair of communication lines to which a communication device is connected and a ground terminal, and each input of a diode bridge is connected to the communication line. And a first surge protection element, a first diode, and a second lightning arrester are connected in series between one output terminal of the diode bridge and the ground terminal, and A communication surge protection circuit in which a second surge protection element, a second diode, and the second lightning arrester are connected in series between the other output terminal of the diode bridge and the ground terminal;
Third and fourth diodes having opposite polarities to the first surge protection element are connected to both ends of the first surge protection element, and both ends of the second surge protection element are Fifth and sixth diodes having opposite polarities to the second surge protection element are connected, and a common connection point of the third and fifth diodes and a common connection point of the fourth and sixth diodes Between the third to sixth diodes, a DC power source that is in the forward direction and an abnormality detection unit connected in series,
The abnormality detection unit detects a short-circuit failure of the first surge protection element by detecting a leakage current flowing from the DC power supply through the first surge protection element, or a second surge from the DC power supply. It has a function of detecting a short circuit failure of the second surge protection element by detecting a leakage current flowing through the protection element.
The invention according to claim 1 will be described with reference to an embodiment described later.
A lightning protection element 21 is connected between the pair of communication lines 10 to which the communication device is connected and the ground terminal E, and each input terminal of the diode bridge DB is connected to the communication line 10. A surge protection element 61, a diode D7, and a lightning protection element 22 are connected in series between the output terminal and the ground terminal E, and surge protection is provided between the other output terminal of the diode bridge DB and the ground terminal E. In the communication surge protection circuit in which the element 62, the diode D8, and the lightning protection element 22 are connected in series,
Diodes D5 and D9 having opposite polarity to the surge protection element 61 are connected to both ends of the surge protection element 61, and a diode D10 having opposite polarity to the surge protection element 62 is connected to both ends of the surge protection element 62. , D6 are connected, and a DC power supply B and an anomaly detector that are forward with respect to the diodes D5, D10, D9, D6 between the common connection point of the diodes D5, D10 and the common connection point of the diodes D9, D6 50 is an abnormality detection circuit connected in series,
The abnormality detection unit 50 detects a leakage current flowing from the DC power supply B through the surge protection element 61 to detect a short circuit failure of the surge protection element 61, or leaks from the DC power supply B through the surge protection element 62. It has a function of detecting a short circuit fault of the surge protection element 62 by detecting a current.

  According to a second aspect of the present invention, in the abnormality detection circuit for the surge protection element for communication according to the first aspect, the abnormality detection unit turns on the semiconductor switch element by the leakage current to operate the light emitting element or the relay. Thus, an alarm indicating a short circuit failure of the first surge protection element or the second surge protection element is output.

  According to the present invention, the lightning surge current path between the communication line and the ground can be provided via the first or second surge protection element and the second lightning arrester even after the first lightning arrester has failed to open. By forming, a short circuit failure of the first or second surge protection element can be reliably detected by the operation of the abnormality detection unit.

It is the circuit diagram which showed the abnormality detection circuit which concerns on embodiment of this invention with the surge protection circuit for communication. It is a block diagram of the conventional surge protection circuit. It is a circuit diagram which shows the 1st, 2nd prior art. It is a circuit diagram which shows a 3rd prior art.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, FIG. 1 is a circuit diagram showing an abnormality detection circuit according to this embodiment together with a communication surge protection circuit. In FIG. 1, parts having the same functions as those in FIG. 4 are denoted by the same reference numerals, and the following description will focus on parts different from those in FIG.

  In FIG. 1, a surge protection element 61, diodes D7 and D8, and a surge protection element 62 are connected in series with the polarity shown in the figure between output terminals of a diode bridge DB in which each input terminal is connected to the communication line 10. Yes. A diode D5, an abnormality detector 50, a DC power source B, and a diode D6 are connected in series with the polarity shown in the figure at both ends of a series circuit of the surge protection element 61, the diodes D7 and D8, and the surge protection element 62. .

The anode of the diode D7 is connected to the anode of the diode D9, and the cathode of the diode D9 is commonly connected to the cathode of the diode D6. The cathode of the diode D8 is connected to the cathode of the diode D10, and the anode of the diode D10 is commonly connected to the anode of the diode D5. Therefore, the DC power supply B, the abnormality detection unit 50, the diode D5, the surge protection element 61, and the diode D9, and the DC power supply B, the abnormality detection unit 50, the diode D10, the surge protection element 62, and the diode D6. A series circuit is configured.
Further, the cathode of the diode D7 (the anode of the diode D8) is connected to the ground terminal E via a lightning protection element 22 such as a gas-filled discharge tube (GDT) having a bipolar structure.

  Here, similarly to FIG. 4, the abnormality detection unit 50 turns on a semiconductor switch element such as a thyristor or a transistor using a leakage current flowing in the surge protection element 61 or 62 as a trigger, and a light emitting element such as a light emitting diode or a relay (whichever (Not shown) is also provided.

  In the above configuration, the surge protection elements 61 and 62 correspond to the first and second surge protection elements in the claims, respectively, and similarly, the lightning protection elements 21 and 22 correspond to the first and second lightning protection elements, Diodes D7, D8, D5, D9, D10, and D6 correspond to the first, second, third, fourth, fifth, and sixth diodes, respectively.

In the above configuration, the avalanche breakdown diode (ABD) is used for the surge protection elements 61 and 62, but a Zener diode may be used, and a varistor such as a metal oxide varistor (MOV) or a surge protection thyristor (TSS). A thyristor such as may be used.
The lightning protection element 22 uses a gas discharge tube (GDT), but a varistor such as a metal oxide varistor (MOV), a thyristor such as a surge protection thyristor (TSS), an avalanche breakdown diode (ABD) or a zener. A diode may be used.
2 and 4, a current limiting resistor R2 (positive characteristic thermistor) may be connected between the input terminal L2 and the output terminal T2.

Next, the operation of this embodiment will be described.
When the lightning surge current generated between the communication line 10 and the ground is positive after the lightning arrester 21 is broken due to the lightning surge current, the lightning surge current is input terminal L1 → resistance R1 → diode D2 → surge. The protection element 61 → the diode D7 → the lightning protection element 22 → the ground terminal E, or the input terminal L2 → (resistor R2) → the diode D4 → the surge protection element 61 → the diode D7 → the lightning protection element 22 → the grounding terminal E.

  In addition, when the lightning surge current generated between the communication line 10 and the ground is negative, the lightning surge current is input terminal L1 → resistance R1 → diode D1 → surge protection element 62 → diode D8 → lightning protection element 22 → It flows through the path of the ground terminal E or the input terminal L2 → (resistor R2) → diode D3 → surge protection element 62 → diode D8 → lightning arrester 22 → ground terminal E.

As a result, when the surge protection element 61 or 62 is short-circuited, the voltage of the DC power supply B is changed to the abnormality detection unit 50 → diode D5 → surge protection element 61 → diode D9 → DC power supply B path and abnormality detection. By applying to the surge protection elements 61 and 62 through the path of the part 50 → the diode D10 → the surge protection element 62 → the diode D6 → the DC power supply B, a leakage current flows through these surge protection elements 61 or 62.
Therefore, by using the above leakage current as a trigger and turning on the semiconductor switch element in the abnormality detection unit 50, the light emitting element can be turned on or the relay can be operated to output an alarm, and the surge protection element 61 or An abnormality caused by 62 short-circuit failure can be detected and notified.

With the above operation, it is possible to easily detect an abnormality when the surge protection element 61 or 62 is short-circuited due to a lightning surge current generated between the communication line 10 and the ground after the lightning arrester 21 is broken open. is there.
Note that the configuration of the abnormality detection unit 50 is not limited to that described in Patent Document 1, and as shown in FIG. 3A, a series circuit of a surge protection element that is an abnormality detection target and diodes D5 and D6. A checker 40 may be connected to both ends, or a DC power supply B and a light emitting element such as a light emitting diode LED may be connected in series as shown in FIG. In any case, any means can be used as long as it can confirm that a leakage current caused by a short-circuit failure flows when a DC voltage is applied to a surge protection element that is an abnormality detection target.

10: communication lines 21, 22: lightning protection elements 31, 61, 62: surge protection element 40: checker 50: anomaly detection unit L1, L2: input terminals T1, T2: output terminal E: ground terminal DB: diode bridges D1 to D10 : Diode B: DC power supply LED: Light emitting diode R1, R2: Resistance

Claims (2)

A first lightning arrester is connected between a pair of communication lines to which a communication device is connected and a ground terminal, and each input terminal of the diode bridge is connected to the communication line, and one output of the diode bridge A first surge protection element, a first diode, and a second lightning arrester are connected in series between the terminal and the ground terminal, and the other output terminal of the diode bridge and the ground terminal In the communication surge protection circuit in which the second surge protection element, the second diode, and the second lightning arrester are connected in series,
Third and fourth diodes having opposite polarities to the first surge protection element are connected to both ends of the first surge protection element, and both ends of the second surge protection element are Fifth and sixth diodes having opposite polarities to the second surge protection element are connected,
DC power supply and anomaly detection in a forward direction with respect to the third to sixth diodes between a common connection point of the third and fifth diodes and a common connection point of the fourth and sixth diodes An anomaly detection circuit connected in series with
The abnormality detection unit detects a short-circuit failure of the first surge protection element by detecting a leakage current flowing from the DC power supply through the first surge protection element, or a second surge from the DC power supply. An abnormality detection circuit for a communication surge protection element, having a function of detecting a short-circuit failure of the second surge protection element by detecting a leakage current flowing through the protection element. In the abnormality detection circuit of the surge protection element for communication according to claim 1,
The abnormality detection unit outputs a warning indicating a short circuit failure of the first surge protection element or the second surge protection element by turning on a semiconductor switch element by the leakage current and operating a light emitting element or a relay. An abnormality detection circuit for a surge protection element for communication, characterized by:

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