JPH1141798A - Lightning protection adapter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the erroneous operation of a digital service unit DSU due to a surge voltage between two communication lines or the open circuit due to blow-out of a resistor. SOLUTION: A bilateral two pole thyristors Z18, exhibiting no delay during high speed operation at an operation starting voltage of 155V or below, is inserted between communication lines L1 and L2. According to the arrangement, the voltage between the communication lines L1 and L2 does not exceed 155V even if a lightning surge voltage is generated due to fluctuation in the operating characteristics of a lightning protection circuit for subscriber protector ARR or digital service unit DSU thus preventing the erroneous operation of the digital service unit DSU or the open circuit due to blow-out of a resistor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightning protection adapter for protecting communication equipment from overvoltage such as lightning surge.

[0002]

2. Description of the Related Art On the subscriber side of a digital line such as an ISDN line or a digital dedicated line, a terminal having a line terminating device or a line terminating device using an AC power supply for two communication lines connected to a telephone center. An adapter or the like is connected, and a communication device such as a personal computer using an AC power supply is connected. In such a configuration, a lightning surge may enter from a communication line or a power line to cause a failure. As a lightning protection circuit, it is well known that a bypass circuit is configured between two communication lines and an AC power line. It is a fact of.

FIG. 4 shows an example of the prior art. In the figure, L1 and L2 are two communication lines connected to the telephone center, ARR is a subscriber protector, DSU is a line terminator, T
E is a communication device, AC1 and AC2 are AC power supply lines, G is a ground terminal, FG is a frame ground, and LP is a lightning protection adapter for protecting the line terminating unit DSU and the communication device TE from lightning surge. C1 and C2 denote the line termination unit DSU and the internal circuit of the communication equipment TE, respectively, R1 to R
Reference numeral 6 denotes a resistor for preventing an excessive current from flowing into the internal circuit of the line terminating device DSU, and Z1 to Z17 denote lightning arresters, which include gas-filled discharge tubes, varistors, PNPN semiconductor elements, and the like.

[0004] Most of the lightning damage received by the communication equipment TE occurs when a lightning surge induced in an outdoor communication line or a power supply line flows out of the communication line to the power supply line or flows out of the power supply line to the communication line. Occur. For this reason, usually, the lightning arresters Z1 to Z7 are mounted in the line termination device DSU, and the lightning arresters Z8 to Z13 are mounted in the communication equipment TE. These lightning arresters can be connected without connecting the lightning protection adapter LP. The elements are operated to form a lightning surge bypass path (solid arrow in FIG. 4), and the circuit is designed so as to prevent failure of the line terminating unit DSU and the internal circuits C1 and C2 of the communication equipment TE. However, in a lightning storm area or the like, even if these lightning arresters are built in, if an excessive lightning surge current flows, these lightning arresters may be destroyed. For this reason,
Further, measures are taken to connect a lightning protection adapter LP as shown in FIG. 4 and add a bypass circuit for the line terminating device DSU and the communication equipment TE.

[0005] The lightning protection adapter LP of FIG. 4 has lightning protection elements Z14 and Z15 on the communication line side and lightning protection elements Z16 and Z17 on the power supply side mounted therein. The communication device TE is designed to be able to bypass between the communication line and the power supply line with a lower voltage than the series circuit of the lightning arresters. Usually, the line termination device DS
The lightning arresters Z4 to Z7 of U have an operation start voltage of 135V to 195V in consideration of the DC power supply voltage of the communication line, and the lightning arresters Z8 to Z11 of the communication device TE have an operation start voltage of 200V to 500V. However, those having an operation start voltage of about 300 V to 2 kV are used for Z12 and Z13.

For this reason, the lightning arresters Z14 and Z15 on the communication line side of the lightning protection adapter LP have an operation start voltage of 200 V or less.
300V (<135V + 200V), the lightning arresters Z16, 17 on the power supply line side have an operation start voltage of 300V to 1kV (<
A lightning arrester having a voltage of 300 V to 2 kV is used. In this way, with respect to the lightning protection between the communication line and the power supply line, which causes the most lightning damage, the lightning protection element of the lightning protection adapter LP operates before the lightning protection element of the line termination device DSU or the communication equipment TE operates. As a result, a lightning surge current can flow toward the lightning protection adapter LP (dotted arrow in FIG. 4), and the line termination device DS
It is possible to reduce damage to the U and the communication device TE.

[0007]

However, even if such measures are taken, lightning arresters Z4,
Variations in operating characteristics are inevitable between Z5 and Z6, Z7, between lightning arresters Z14 and Z15, and a surge voltage may occur between the communication lines L1 and L2.
As a countermeasure against the surge voltage generated between the communication lines L1 and L2, a lightning arrester Z1 is inserted in the line terminating device DSU. When the lightning arrester Z1 operates, the lightning surge current is reduced to L1, R1, R2, L2. Will flow like
If the current is large, there is a problem that the resistors R1 and R2 are blown and a line break occurs. Further, even in the case of a low surge voltage at which the lightning arrester Z1 does not operate, there is also a problem that a surge enters the internal circuit C1 of the line termination device DSU and the circuit itself malfunctions.

[0008] The object of the present invention is to provide the line termination device DS by means of such a surge voltage between the communication lines L1 and L2.
An object of the present invention is to solve the problem that the U malfunctions or the resistance in the line terminating unit DSU is blown to break the line.

[0009]

A lightning protection adapter according to the present invention is a lightning protection adapter connected to a line termination device connected to a communication line of a digital line or a terminal adapter with a built-in line termination device. A bypass circuit of a lightning surge is formed by inserting a bidirectional bipolar thyristor, an avalanche diode, a Zener diode, or the like between the two wires.

Further, the operation start voltage of a bidirectional bipolar thyristor, an avalanche diode, a Zener diode or the like inserted between two communication lines is 155 V or less.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described in the prior art, the surge voltage between the two communication lines L1 and L2 causes the line terminating unit DSU to malfunction or break down.

The result of confirming this phenomenon by experiment is shown in FIG.
Shown in The experiment was conducted with the same configuration as in FIG.
SU, 1 × 40μs with power supplied to communication equipment TE
Is applied between the communication lines L1 and L2,
The state of the line termination device DSU was monitored together with the applied current. R1 and R2 are 15Ω resistors, and Z1 is a bidirectional two-terminal thyristor (hereinafter referred to as PNP) having an operation start voltage of 110V.
A PNPN element having an operation start voltage of 200 V was used for Z14 and Z15.

When the voltage between the communication lines L1 and L2 is 210 V or less, the lightning arrester Z1 of the line termination device DSU is in a region where the lightning arrester Z1 does not operate. Occurs. When the surge voltage between the communication lines L1 and L2 becomes 210 V or more, the lightning arrester Z1 operates and the line termination device DS
Although there is no malfunction of U, if the voltage exceeds 290 V, a problem occurs that the resistors R1 and R2 are blown by the surge current. When the voltage further increases, the lightning arresters Z14 and Z15 inserted in series between the communication lines L1 and L2 in the lightning protection adapter LP operate, so that the resistors R1 and R2 do not blow.

In this case, a lightning arrester having an operation start voltage of 200 V is used for the lightning arresters Z14 and Z15 of the lightning protection adapter LP. In the case of (1), the range in which the resistors R1 and R2 are blown further widens, and a line break fault is more likely to occur. If the operation start voltage of the lightning arresters Z14 and Z15 of the lightning protection adapter LP is reduced, it is possible to prevent malfunction of the line terminating unit DSU and fusing of the resistors R1 and R2, but on the other hand, transmission, control signals and communication. Considering the induced voltage from the power line generated in the line, the lightning arresters Z14, Z which may be directly connected to the ground
There is a problem that the operation start voltage of No. 15 cannot be made 137 V or less, and a problem that the voltage between the communication lines L1 and L2 becomes 274 V or more.

Therefore, in the present invention, as means for suppressing the surge voltage between the communication lines L1 and L2, the lightning protection adapter LP or the line terminating unit DSU may be connected between the communication lines L1 and L2 at the input portion thereof. Bidirectional PNP
An N element is inserted. The operation start voltage is set to 155 V or less.

As described above, by inserting a bidirectional PNPN element having an operation start voltage of 155 V or less between the lightning protection adapter LP or the communication lines L1 and L2 of the line terminating unit DSU, the subscriber protector ARR or the like. The line termination device DS
Due to variations in the operating characteristics of the U lightning protection circuit, the communication line L
Even if a lightning surge voltage is generated between L1 and L2, the voltage in question does not become 155 V or more, which can prevent malfunction and resistance disconnection of the line termination device DSU. Since the PNPN element operates at high speed and does not have a delay unlike a gas-filled lightning arrester, the voltage can be controlled with high reliability.

[0017]

FIG. 1 shows an embodiment of the present invention. This embodiment is an embodiment of a lightning protection adapter connected to a line terminator connected to a digital line such as an ISDN line or a digital dedicated line. Lightning protection elements Z14, Z15 of lightning protection adapter LP
The operation start voltage 125V-
A 155 V bidirectional PNPN semiconductor element Z18 is inserted. As the lightning arrester Z18, a bidirectional PNPN semiconductor element which operates at high speed and maintains the voltage after the operation at almost 0 V is most suitable. If a varistor is used as the lightning arrester Z18, the varistor will have a reduced suppression voltage depending on the magnitude of the current, so that there is a high possibility that the line termination device DUS will malfunction. Further, if a gas-filled discharge tube is used for the lightning arrester Z18, the surge voltage cannot be completely controlled due to operation delay, and a protective effect against malfunction or resistance disconnection of the line termination device DSU cannot be obtained. The other configuration is the same as that of FIG.

In the same experimental system as FIG. 4, a lightning protection adapter LP
PNP with an operation start voltage of 150 V as a lightning arrester Z18
An N element was inserted and a surge voltage of 2 kV was applied between the communication lines L1 and L2 with a voltage waveform of 1 × 40 s.
The voltage between 1 and L2 did not exceed 150 V, and no malfunction or resistance disconnection of the line termination device DSU occurred.

FIG. 2 shows another embodiment of the present invention. This embodiment is an embodiment of a lightning protection adapter connected to a terminal adapter with a built-in line termination device connected to a digital line. DSU-TE is a terminal adapter with a built-in line termination device. It is.

Further, in the present invention, the lightning protection element Z is used in order to use the lightning protection adapter even with an analog communication line.
The lower limit value of the operation start voltage of 14, Z15 is set to 125 V or more, which does not cause a problem even with the dial signal of the analog communication line. That is, in an analog line, a voltage of 75 ± 8 V (effective value) = 117 V (peak value) is applied by a dial signal for calling a telephone.

In each of the above-described embodiments, a bidirectional two-pole thyristor is used for the configuration of the bypass circuit. However, an equivalent bypass circuit may be configured by using a combination of two avalanche diodes and two Zener diodes. Can be.

[0022]

As described above, in the present invention, since the same protection circuit as that of the related art is configured between the communication line and the power supply line where lightning damage is most frequent, the basic lightning protection is provided. In addition to the above, there is no problem with the transmission line induced voltage.
In addition, since a bidirectional two-pole thyristor avalanche diode and a zener diode for surge voltage control are inserted between the two communication lines, malfunction of the line termination device or the terminal adapter with a built-in line termination device is prevented. Thus, the effect of preventing the resistance of the line termination device from being blown can be obtained. Since the operation start voltage of the bidirectional two-pole thyristor, avalanche diode, zener diode and the like is 155 V or less, erroneous operation of the line termination device or the terminal adapter with built-in line termination device can be completely prevented. Further, if an element having an operation start voltage of 125 V or more is used for the bidirectional bipolar thyristor or the like, it does not affect the dial signal, so that the lightning protection adapter according to the present invention can be applied to an analog line. .

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of an embodiment of a lightning protection adapter of the present invention.

FIG. 2 is a circuit diagram showing a configuration of another embodiment of the lightning protection adapter of the present invention.

FIG. 3 is a diagram showing a result of confirming a problem in a conventional device by an experiment.

FIG. 4 is a circuit diagram showing a configuration of an example of a conventional lightning protection adapter.

[Explanation of symbols]

 L1, L2 Communication line TE communication equipment LP Lightning protection adapter R1 to R6 Resistance ARR Subscriber protector AC1, AC2 AC power supply line C1 Internal circuit of DU Z1 to Z17 Lightning arrester DSU Line termination device DSU-TE Terminal with built-in line termination device Adapter G Ground C2 TE Internal Circuit Z18 Bidirectional Bipolar Thyristor According to the Invention

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Takahiro Hayashi Nippon Telegraph and Telephone Corporation 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo

Claims (2)

[Claims] 1. A lightning protection adapter connected to a line terminator connected to a communication line of a digital line or a terminal adapter with a built-in line termination device, wherein a bidirectional two-pole thyristor or an avalanche diode is provided between the two communication lines. A lightning protection adapter characterized in that a lightning surge bypass circuit is configured by inserting a Zener diode. 2. The lightning protection adapter according to claim 1, wherein an operation start voltage of a bidirectional bipolar thyristor, an avalanche diode, a Zener diode or the like inserted between the two communication lines is 155 V or less.