JPS60174022A - Lightning protecting circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a lightning protection circuit that can protect communication equipment from being destroyed by lightning or protect the user's body, and particularly relates to a lightning protection circuit that is small in size and capable of protecting the body of a user.
The present invention relates to a lightning protection circuit that enables cost reduction.

[Background of the invention]

FIG. 1 shows an example of a configuration in which conventional lightning protection measures are applied to general digital communication equipment that is supplied with power from a commercial power source. In the figure, 1.2 is a communication line, 3
is a protector, 5 is a grounding wire, 6 is earth, 7 is a line termination device, 8 is a common line for the line termination device, 9A is a Tsushin equipment, 1
1 is a common line for the communication device; 12 and 13 are commercial power lines.

The protector 3 is provided with a detonator 4, the line termination device 7 is provided with a line termination circuit 20, and the communication device 9A is provided with a transformer IO9 communication processing circuit 22. A noise filter 25 is provided.

In addition, 14, 16. '18.30 is resistance, 17,19,
21, 23, 28, and 29 indicate voltage limiting elements.

As mentioned above? In the conventional technology configured, when a vertical surge enters the ground from the communication line 1 or 2, the detonator 4 in the protector 3 discharges, and the surge current is transferred to the ground line 5.
It has the function of discharging water to the earth 6 via the grounding resistor 14.

However, if the rise of the vertical surge is sudden, the potential on the 1, for example, 2 communication line l side rises before the detonator 4 discharges, and the potential on the side of the communication line 1 rises to 500 V, which is the normal discharge starting voltage of the detonator 4.
If a voltage exceeding
It will join the 7. In order to prevent this, the common line 8 for the line termination device and the grounding line 5 of the protector 3 are connected at points A and B in the figure, and the resistor 16. Voltage limiting element 17. The vertical surge is made to flow to the ground 6 via points B and A.

As a result, the sum of the voltage drop across the resistor 16 and the clamp voltage at the voltage limiting element 17 is applied to the lightning arrester 4, and the lightning arrester 4 soon starts discharging. If a vertical surge is applied to the communication line 2 side, the resistance 18° voltage limiting element 19
The above-mentioned vertical surge flows to the ground 6 through the ground, resulting in exactly the same result.

The problem here is that, as mentioned above, even if the detonator 4 discharges and the vertical surge flows to the ground 6, the grounding resistor 14 exists, so the potential at the upper point 12A increases due to the voltage drop caused by this resistor. It remains as it is. On the other hand, power line 1
One of 2 and 13 is usually grounded via a grounding resistance in a pole transformer (not shown), and the value of the grounding resistance may be lower than the grounding resistance 14 of the communication line. many. In such a case, a high voltage will be applied between the point A and the power line 12 or 13, and there is a possibility that the line termination device 7 or Tsushin w9A will be destroyed.

To deal with this, the common line 8 for the line termination device in which a voltage limiting element 21 having an operating voltage slightly lower than the withstand voltage of the line termination circuit 20 in the line termination device 7 is inserted,
By bypassing the surge voltage, destruction of the line termination circuit 20 is prevented.

Similarly, the communication processing circuit 22 is destroyed by the communication device common line 11 in which the voltage limiting element 23 having an operating voltage slightly lower than the higher withstand voltage of either the communication processing circuit 22 or the transformer 10 is inserted. is prevented.

Further, when the communication device 9A has a metal casing, the casing a is grounded to the earth 6 through a grounding wire 24 for human body protection. On the other hand, a capacitor 26 in a noise filter 25 for blocking noise entering from a commercial power source
．． Connect the midpoint of 27 to the housing. The case has a ground wire 2
4 is grounded to the ground 6, so the capacitor 26.
27 is grounded at its midpoint. Therefore, unless the surge withstand voltage of the capacitors 26 and 27 is made sufficiently large, the high potential at the point A will cause the common line 11 for the communication device to reach the common line 11 for the line termination device. Capacitor 26 or 27 via commercial power supply side voltage limiting element 2B or 29
This will lead to Earth 6.

In this case, there is no problem if the grounding resistance 30 of the casing of the communication device 9 is sufficiently small, but in general, it is difficult to ground indoors, so even if it is grounded, the resistance value is often high. It is conceivable that the potential of the grounding wire 24 of the casing, that is, the potential of the casing, will rise, creating a dangerous situation if the user touches the casing. In addition, the above capacitor 2
If there is a leakage current, the commercial power supply voltage will be divided by the capacitors 26 and 27, and if you touch the housing, you may get an electric shock. Furthermore, in the above configuration, there is a problem that the device becomes expensive because 10 voltage limiting elements are used.

FIG. 2 shows an example of a configuration in which a lightning protection measure according to the prior art is applied to a communication device, such as a public telephone, which has a built-in line termination circuit. Symbols 1 to 6 and 10 to 30 indicate the same components as shown in FIG. 1, 9B indicates a communication device, and 31.32 indicates a wiring section, respectively.

The operation of this configuration is almost the same as that of the configuration shown in FIG. Since there is a possibility that surge current may flow through the connection parts 31 and 32, it is necessary to mount it in a way that does not induce it to other parts or cause sparks, etc., which causes another problem of increasing the size of the device. It had a

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its purpose is to provide a lightning protection circuit that solves the above-mentioned problems in conventional lightning protection circuits and can be made smaller and lower in price. It is in.

[Summary of the invention]

The gist of the present invention is that, in a communication device in which a line termination circuit is mounted in the communication device, the line termination circuit and the communication processing circuit are directly connected, and a plurality of voltages between the communication lines connected to the line termination circuit are connected. It is located at a point where the midpoint of the limiting element and the midpoint of the plurality of voltage limiting elements between the commercial power lines are connected via the voltage limiting element.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings.

Figure 1 is a circuit diagram showing an example in which lightning protection measures, which are an embodiment of the present invention, are applied to digital communication equipment that is supplied with power from a commercial power source. In the figure, symbol 9 is a communication device;
33 to 36 are voltage limiting elements, 37 is a common line, and 42
．． 43 indicates a resistor, and other symbols indicate the same components as previously shown in FIGS. 1 and 2.

In this embodiment, the 1-line termination circuit 20 and the communication processing circuit 22 are directly connected, and the resistors 42 and 43 and the voltage limiting element 3 are used to ensure the operation of the detonator 4 in the protector 3.
3.34 is installed in the protector 3.

Voltage limiting elements 35 and 36 for vertical and lateral surge protection are provided on the communication line side of the communication device 9.
6 and the midpoints of the voltage limiting elements 28 and 29 on the commercial power supply side are connected by a common line 37 via the voltage limiting element 23.

When implementing the circuit of this embodiment, it is possible to mount the communication line inlet and the commercial power outlet in close proximity, as shown in FIG. It has the advantage of being able to eliminate such problems. Another advantage is that the number of voltage limiting elements can be reduced to seven. Furthermore, there is no need to draw the grounding wire 5 of the protector 3 into the communication device 9, and only the grounding wire 24 for human body protection is required, so there is an advantage that noises etc. caused by the grounding can be easily handled. be.

FIG. 5 shows a second embodiment of the present invention, in which a resistor 42.
43 is mounted in the communication device 9, and the voltage limiting elements 34 and 35 and 33 in the embodiment shown in FIG.
and 36 are also used and mounted in the communication device 9. In this case, in order to operate the detonator 4 stably, wiring between point A and point B is required. In the case of this embodiment as well, as shown in FIG. 4, it is possible to eliminate the influence of the surge current flowing through the common line 37 on other circuits.

This embodiment has the advantage that the number of voltage limiting elements is only five. Note that the sixth voltage limiting element 44 is configured so that surge current caused by lightning is absorbed by the capacitor 26 of the noise filter 25.
Alternatively, the current flows through the casing of the communication device 9 through 27 and from the casing to the ground wire 24 to prevent the user from receiving an electric shock even if he or she touches the casing. Because it flows, commercial electricity 1. Channel the noise from the source to the housing,
This has the effect of eliminating problems such as guidance.

In addition, in the above explanation, the case where there are two connections 38 and 39 between the line termination device [7 and the communication device i9 has been explained, but normally two speaking lines and two receiving lines are used. There are 4 pieces in total. In this case, the prior art configuration shown in FIG. 1 requires 14 voltage limiting elements, whereas the configuration shown in FIG.
The configuration of the embodiment shown in FIG. 5 has the advantage that even if the number of connections increases, the number of voltage limiting elements may be seven or five, respectively.

Furthermore, in the configuration of the embodiment shown in FIGS. 3 and 5,
The operating voltage of the voltage limiting element 23 is made slightly lower than the withstand voltage of the communication device 9 to minimize the exchange of surges between the communication stapler and the commercial power meter. Furthermore, by increasing the operating voltage of the voltage limiting elements 28 and 29, it is also possible to serve the role of the voltage limiting element 23 and omit the voltage limiting element 23. in this case,
To protect against lateral surges from the commercial power meter, it is necessary to separately insert a voltage limiting element between the commercial power lines 12 and 13.

(Effects of the Invention) As described above, according to the present invention, in a communication device in which a line termination circuit is mounted in the communication device, the line termination circuit and the communication processing circuit are directly connected, and the line termination circuit is connected to the communication processing circuit. The midpoints of the multiple voltage limiting elements between the communication lines and the midpoints of the multiple voltage limiting elements between the commercial power lines are connected via the voltage limiting element, making it possible to In comparison, the number of voltage limiting elements is small, the common line is short, and it can be implemented without the influence of induction on other circuits, making it possible to realize a lightning protection circuit that is smaller and cheaper. This has a remarkable effect.

[Brief explanation of the drawing]

1 and 2 are diagrams showing a configuration example of a conventional lightning protection circuit, FIG. 3 is a configuration diagram showing a first embodiment of the present invention, and FIG.
The figure is a perspective view showing the state of implementation of the main parts, Fifth Town 1 Invention 0
Configuration diagram 1 showing 2nd implementation example 12. ■, 2: communication line, 3: protector, 4: detonator, 5: grounding line, 9: communication device, 12, 13: commercial power line, 23゜28
．． 29, 33, 34, 35, 36. /14: Voltage limiting element, 20: Line termination circuit, 22: Communication processing circuit, 25
:Noise filter.

Claims (1)

[Claims] (1) Lightning protection circuit for communication equipment that includes a built-in line termination circuit into which a pair of communication lines from the station are connected via a protector, and is supplied with commercial power via at least 1 pair of power lines. The line termination circuit and the communication processing circuit of the communication device are directly connected, and a plurality of voltage limiting elements are connected in series between the power supply lines and between the communication lines, and the plurality of voltage limiting elements are connected in series. A lightning protection circuit characterized in that the midpoints of the two are connected together.