JPH01316012A - Electromagnetic wave disturbance preventing module - Google Patents

Abstract

PURPOSE:To prevent an electromagnetic wave noise from a communication earth and a protection earth with a simple constitution by inserting a choke coil for noise current prevention in series with the communication earth in a communication electronic equipment and providing a gas tube arrester for preventing electrostatic discharge and lightning surge current in parallel with the coil. CONSTITUTION:The operation of the electromagnetic wave disturbance prevention module is illustrated by an electronic equipment 1, a noise current 2, an electromagnetic wave noise 3, a choke coil 4, a gas tube arrester 5, an electrostatic discharge noise and lightning surge current noise 6 and an electromagnetic wave prevention module 7, and the module 7 is provided in series with the communication earth or protection earth of the equipment 1. Thus, the electromagnetic wave disturbance noise from the loop antenna consisting of the earth is prevented and the noise due to an instantaneous high voltage such as electrostatic discharge or lightning surge is also prevented.

Description

[Detailed Description of the Invention] [4 Already Required] This invention relates to a means for preventing electromagnetic wave interference in communication electronic equipment, and in particular, for the purpose of preventing electromagnetic wave interference caused by noise current flowing in a grounding wire. A choke coil for preventing noise current is inserted in series, and a gas tube arrester for blocking electrostatic discharge and lightning surge current is connected in parallel to the choke coil.

[Industrial application field]

The present invention relates to means for preventing electromagnetic interference in communication electronic equipment.

BACKGROUND OF THE INVENTION With the electronicization of communication electronic equipment, particularly the line circuits of electronic exchanges, overvoltage protection circuits are being provided to protect electronic components from induced lightning, ground faults, and cross-contact. For grounding of this overvoltage protection circuit, a communications ground and a safety ground are provided at the exchange.

FIG. 3(a) shows an example of application in an exchange.

In the indoor line circuit, a high-speed, low-power arrester is constructed by connecting a varistor or diode in series with the communications ground. On the other hand, a low-speed, large-current arrester is installed on the outdoor and indoor MDF as a lightning arrester, and a safety ground (100
Ω or less) in series. A primary lightning arrester installed outdoors is configured with a gas tube arrester or the like, and a secondary lightning arrester installed in an indoor MDF is configured with a gas tube or a varistor. Although the communication ground and the safety ground are provided separately, the communication ground is used for surge absorption and is also used as a ground for interoffice communication.

An example of the configuration when used for interoffice communication is shown in FIG. 3(b). When used for inter-office communication, a communication line is used to connect other stations, and a communication ground is used to form a loop circuit to check the availability of communication lines between stations. In other words, a signal is sent out by connecting the outbound route with a communication line and the return route with ground, and if the signal is returned, it is determined that the facility is idle, and if the signal is not returned, it is determined that the facility is in use. In this case, the earth resistance between the two stations, that is, the difference in earth potential, must be 10Ω or less.

As mentioned above, two types of earths are used at exchanges: the first type, power supply earth (10Ω or less), and the second type, safety earth, power system earth (100Ω or less).
As shown in FIG. 3(c), both ground cables constitute a loop antenna, and the amount of radiation of electromagnetic noise generated from the ground wire increases. This is because there is a difference in ground potential and ground resistance, which causes a difference in noise passing through the ground wire, creating a gap between the ground lines, forming a kind of loop antenna. Because of this pseudo-loop antenna, noise is emitted into space, forming a noise-emitting antenna. Since this electromagnetic wave noise affects communication lines, it is necessary for communication equipment to prevent these transmissions.

[Conventional technology]

Conventionally, high-frequency noise from devices is absorbed by the casing and then released to the ground through a grounding wire. At this time, the high-frequency current flowing through the grounding wire radiates electromagnetic waves (radio waves) noise into the space, interfering with the operation of other devices. In order to reduce this effect, conventional methods have been to make the ground wire thicker, lower the impedance, and reduce the potential difference on the ground wire, thereby reducing the radiation noise level, but this is not perfect.

In communication equipment, conventionally, a choke coil is inserted in series in a communication ground circuit as shown in FIG. In the figure, ■ indicates electronic equipment, and 2 indicates wholesale. If 3 is a sound current, 3 is an electromagnetic noise, and 4 is a choke coil, the electromagnetic noise 3 generated by the noise current 2 is prevented by the choke coil 4. However, since the electric coil 4 also blocks noise such as electrostatic discharge and lightning surges, which can cause high voltage at 7 o'clock, there is a risk of damaging the electronic circuit within the device. Particularly in the case of switching equipment, it is essential to conduct lightning surges to the ground.

[Problem to be solved by the invention]

Therefore, the present invention prevents the radiation of electromagnetic noise generated from a loop antenna composed of a communication ground and a safety ground in communication equipment, and also prevents the radiation of electromagnetic noise caused by instantaneous high voltages such as those caused by electrostatic discharge or lightning surges. The purpose of the present invention is to provide an electromagnetic interference prevention module that also prevents such noise.

[Means to solve the problem]

FIG. 1 shows a basic configuration diagram of the present invention. In the figure, ■ is electronic equipment, 2 is noise current, 3 is electromagnetic wave noise, 4 is choke coil, 5 is gas tube Aresfu, 6 is electrostatic discharge noise, lightning surge current noise, 7 is electromagnetic wave prevention that constitutes the present invention Indicates a module. The electromagnetic wave prevention module 7 is installed in series with the communication ground or security ground of the electronic device j, and prevents electromagnetic interference noise generated from the loop antenna composed of the communication ground and the security ground, and also prevents electrostatic discharge and lightning. It also prevents noise such as surges that cause high voltage instantaneously.

[Effect]

In FIG. 1, an electromagnetic wave interference module 7 according to the present invention is shown.
For example, it is composed of a choke coil 4 and a gas tube Aresfu 5. The noise current 2 generated by the electronic device 1 is prevented from flowing to the ground by the choke coil 4. Therefore, the electromagnetic noise 3 is not radiated into the air, and no electromagnetic interference occurs.

On the other hand, the electrostatic discharge/lightning surge current 6 is caused by the choke coil 4
When it generates a high voltage with respect to the earth, it tries to flow through the earth cable. Therefore, a high voltage is applied to the gas tube arrester 5, causing discharge. In other words, high voltage leaks to the ground,
To prevent destruction or malfunction of the electronic device 1.

〔Example] An embodiment of the present invention applied to communication equipment is shown in FIG.

In the figure, 11 is a communication line, 12 is a line circuit, and 13 is a communication line.
14 is a communication ground, 15 is a security ground, 7 is an electromagnetic interference prevention module connected to the communication ground 14, 4 is a choke coil, and 5 is a gas tube arrester.

The electromagnetic interference prevention module 7 of the present invention has a line circuit 12
installed near the exit of the device and grounded with a communications ground cable. The choke coil 4 has a resistance value of 0Ω in terms of direct current, but has a resistance value of several Ω against high frequencies of several Mllz, and has the function of preventing high frequency noise, and uses a general choke coil structure in which the coil is wound around a ferrite core. can. In addition, the gas tube arrester 5 is a discharge tube for leak absorption.
It is possible to use a general gas tube arrester structure in which a ceramic tube is filled with gas and discharges when the voltage between the electrodes exceeds a specified voltage.

In the case of an exchange, this electromagnetic wave interference module 7 is installed at the communication ground 14 where a large amount of noise is detected.

Noise induced to the safety ground 15 is connected to the communication ground 1.
Generally, the level is lower than the noise induced in the communication ground 14, and since it is common mode noise, it is canceled and the difference becomes noise and is often radiated from the communication ground 14. Therefore, the electromagnetic interference prevention module 7 installed on the communication ground 14
Therefore, high frequency noise induced into the line circuit 12 can be absorbed.

In addition, the instantaneous high voltage flowing to the communication ground 14 flows to the ground due to the discharge of the gas tube arrester 5, and
The line circuit 12 can be prevented from being destroyed by the high voltage induced by the voltage.

〔Effect of the invention〕

A simple module that combines commonly used parts, such as a choke coil and a gas tube arrester, can protect against electrostatic discharge and lightning surges, and can also protect against electromagnetic noise emitted by communication ground and safety ground. It can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a basic configuration diagram of the present invention, Fig. 2 is a circuit configuration diagram of an embodiment of the present invention, Fig. 3 is a configuration example of a communication ground and a safety ground, and Fig. 4 is a circuit configuration diagram of a conventional example. shows. In the figure, ■ is an electronic device, 2 is a noise current, 3 is an electromagnetic wave noise, 4 is a choke coil, 5 is a gas tube arrester, 6 is an electrostatic discharge noise/thunder current, 7 is an electromagnetic interference prevention module, and 11 is a Communication line, 12 is line circuit,
13 is an MDF, ]4 is a communications ground, and 15 is a security ground. 'bit, 1

Claims (1)

[Claims] In a means for preventing electromagnetic interference in communication electronic equipment, a choke coil (4) for noise current prevention is inserted in series with the communication ground, and an electrostatic discharge is connected in parallel to the choke coil (4). and a gas tube arrester (5) for blocking lightning surge current.