JP2654172B2 - Lightning protection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention enhances lightning protection performance used in communication equipment which receives power from a commercial power supply line and is connected to a communication line and a line other than the communication line. Related to lightning protection circuits.

2. Description of the Related Art Conventionally, in a communication device which operates by receiving power supply from a commercial power line, an internal circuit of the communication device is provided by using a lightning protection circuit as shown in FIGS. 5 (a) and 5 (b). 101 was protected from lightning surge applied through the communication line 102 and the commercial power line 103.

The lightning protection circuit shown in FIG. 5 (a) is a conventional example using a lightning-resistant transformer. The lightning protection transformers 104 and 105 are inserted into the communication line 102 and the power supply line 103, respectively, to protect the internal circuit 101 of the communication device. Is what you do. The resistance to the lightning surge in this conventional example depends on the performance of the lightning transformers 104 and 105, and the internal circuit 101 is protected from the lightning surge unless the lightning transformers 104 and 105 are damaged.

The conventional example shown in FIG. 5 (b) is a lightning protection circuit excellent in size and weight. It operates when an applied voltage reaches a certain voltage, such as zinc oxide (ZnO), and flows a current to lower the applied voltage. Two surge absorbing elements 106 to be clamped are connected in series between the communication line 102 and the power supply line 103, and the connection points between the surge absorbing elements 106 and 106 between the lines are drawn out and connected in common. This conventional example is a protection circuit in which a vertical surge voltage (surge voltage between the ground and the line) caused by lightning from a communication line 102 flows to a power line 103 through each surge absorbing element 106. Vertical surge is flowing through the communication line 102 according to the same principle. Thereby, the lightning surge voltage is hardly applied to the internal circuit 101, and the internal circuit 101 can be protected.

[Problems to be Solved by the Invention] However, in the lightning protection circuit for communication equipment in the above-mentioned conventional technology, in a telephone device such as a home telephone or a business phone connected to an extension other than the communication line, the lightning protection circuit alone is not sufficient. However, there was a problem that the internal circuit was actually damaged frequently. In the case of the conventional example using the lightning-resistant transformers 104, 105, the lightning-resistant transformers 104, 105
In order to increase the resistance to lightning surges, the transformers 104 and 105 must be increased in size, and even those that can withstand lightning surges of about 10 kV must be considerably large in size and weight, and small and lightweight. This has been a major design constraint for telecommunications equipment that is becoming increasingly sophisticated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has been developed to solve the above-mentioned problems, and to solve the restrictions on size and weight and to improve the protection performance against lightning surge in a communication device to which an extension or the like is connected. It is intended to provide a circuit.

[Means for Solving the Problems] To achieve the above object, the configuration of the lightning protection circuit according to the present invention is configured to be connected to a communication line and a commercial power line and to be connected to one or more pairs of the communication line and the commercial power line. The communication line connected to the communication line and the commercial power line, and each line of the extension line that is connected to the communication device other than the communication line and the commercial power line and that does not communicate outdoors Two or more lightning surge absorbing or discharging elements are connected in series, and the connection point between the lightning surge absorbing or discharging elements between the respective lines is shared or another lightning surge is absorbed or discharged. It is characterized in that connection is made via an element.

[Operation] The present invention relates to a communication device to which a line such as an extension other than a communication line and a commercial power line is connected, and that a line other than the communication line and the commercial power line is also surged to an extension that is not communicated outdoors. Two or more absorbing elements are inserted in series between the lines, and the connection point of the surge absorbing element is connected between the connection points of the surge absorbing element similarly inserted between the communication line and the commercial power line. By connecting them in common or through a lightning arrester or the like, a voltage difference generated between a communication line or a commercial power supply line and an extension line when a lightning surge is applied is suppressed, and lightning protection performance is enhanced.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a circuit diagram showing a first embodiment of the present invention. This embodiment shows an example of lightning protection applied to a telephone which is a communication device connected to an extension bus. In the figure, 1 is an internal circuit, 2 is a communication line, 3 is a commercial power line (hereinafter abbreviated as a power line), 4 is an internal bus communication line, 5 is an internal bus control line,
Reference numeral 6 denotes a surge absorbing element such as zinc oxide. A communication line 2 is connected to the internal circuit 1 and receives power from a commercial power supply from a power supply line 3. Talk line 4 and control line 5 as extension buses
Is used, each of the lines 4 and 5 is also connected to the internal circuit 1. Communication line 2, power line
3, two surge absorbing elements 6 between the communication line 4 and the control line 5
They are connected in series, and a line is drawn out from an intermediate connection point between the two surge absorbing elements 6 between the respective lines, and all the drawn out lines are connected in common. The communication line 4 and the control line 5 connected to the extension bus in the above are, of course, extensions that do not communicate outdoors.

The operation of the embodiment configured as described above will be described. First, the reason why the internal circuit of a telephone is destroyed by the application of a lightning surge to the communication line when a telephone connected to a communication line and receiving power supply from a commercial power supply line is connected to the extension will be described with reference to FIG. I do. In FIG. 2, the communication line 2 and the power line 3
It is assumed that a lightning protection circuit is provided as shown in FIG. Here, the time to reach the maximum voltage is about 10 μs
The result of the measurement when a surge voltage is applied to the communication line 2 is shown. The telephones (internal circuit 1) are connected to the extension lines 4 and 5 and the power line 3
Is removed from the commercial power supply, the ratio of V ₂ / V ₁ becomes almost 1.
Where V ₁ is the voltage between communication line 2 and the ground, and V ₂ is the extension
Voltage between 4,5 and ground.

When the telephones (internal circuit 1) are connected to the extension lines 4 and 5 and the power supply line 3 is connected to the commercial power supply, the ratio of V ₂ / V ₁ becomes several percent smaller than 1.

Therefore, even when a surge voltage is applied only to the communication line 2 with the telephone (the internal circuit 1) connected to the extensions 4 and 5 and the power line 3 connected to the commercial power supply, the communication between the communication lines 2 and the extensions 4 and 5 is not performed. Voltage will occur between the two. The voltage difference between the communication line 2 and the extensions 4 and 5 caused by the application of the surge voltage to the communication line 2 damages the internal circuit 1 of the telephone. Therefore, in order to protect this, it is necessary to eliminate the voltage difference between the communication line 2 and the extensions 4 and 5 or to set the voltage difference to a certain value or less.

In the first embodiment, for example, when a lightning surge is applied from the communication line 2, a lightning surge is generated between the power line 3, the communication line 4, and the control line 5 by the surge absorbing element 6 between the lines. By flowing the generated voltage and the voltage generated between the lines to the power supply line 3, the voltage is suppressed below the operating voltage of the surge absorbing element 6. Thereby, the internal circuit 1 is protected. According to the same principle, both when the lightning surge is applied to the power supply line 3 and when the lightning surge is applied to the communication line 4,
Even when a lightning surge is applied to the communication line 2 or the power supply line 3, a voltage generated between the lines and a voltage generated between the lines are caused to flow through the communication line 2 or the power supply line 3 by the operation of the surge absorption element 6. As a voltage lower than the operating voltage of 6,
The internal circuit 1 can be protected.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention. This embodiment is an example in which the first embodiment is applied to a telephone connected to an extension of a star wiring. When connecting a plurality of star wires to the internal circuit 1 of the telephone, the communication line 2 and the power line 3
, Two surge absorbing elements 6 are inserted in series between the respective lines, and the communication lines 4, 4 '...
By inserting two surge absorbing elements 6 in series between the lines of 5, 5 '... And commonly connecting the lines drawn from the intermediate connection point of the surge absorbing elements 6 inserted between the respective lines, According to the same principle as that of the first embodiment, no voltage higher than the operating voltage of the surge absorbing element 6 is generated even when a lightning surge is applied to any wire, and the internal circuit 1 is protected.

FIG. 4 is a circuit diagram showing a third embodiment of the present invention. This embodiment is an application of the first embodiment, and differs from the first embodiment in that a line drawn from an intermediate connection point of two surge absorbing elements 6 inserted between the power supply lines 3 and another line. This means that the lightning arrester 7 is connected between the two surge absorbing elements 6 inserted and a line drawn from an intermediate connection point. This is to improve the breaking performance between the power line 3 and the other lines 2, 4, and 5. Even if the surge absorbing element 6 inserted in each line is deteriorated due to aging or the like, the power line 3 is not connected to those lines. Can be prevented from affecting the lines 2, 4, and 5. In FIG. 4, the lightning arrester 7 is inserted between the power supply line 3 and the other lines 2, 4, and 5, but may be connected to any one of the lines drawn from the intermediate connection point between the surge absorbing elements 6 inserted between the lines. Alternatively, the lightning arrester 7 may be inserted in a plurality. As the lightning arrester 7, a lightning arrester such as a bipolar lightning arrester that discharges in space is suitable, but other various arresters and surge absorbing elements can be used. Also in this embodiment, similarly to the first and second embodiments, the communication line 2, the power supply line 3, and the extensions 4, 5 are drawn out from the intermediate point of the two surge absorbing elements 6 inserted between the respective lines. Since the lightning arrester 7 conducts in response to a lightning surge applied to the communication line 2, there is almost no voltage difference between the communication line 2 and the extension lines 4 and 5. The proof strength of the internal circuit 1 of the equipment can be improved, and the proof strength against the lightning surge applied to the extensions 4 and 5 can be improved. Can be improved.

In each of the embodiments described above, the lightning surge protection circuit for the extension is described. However, even when another line such as a doorphone line is connected to the internal circuit 1, two lines are connected between the lines.
Of the surge absorbing elements 6 are inserted in series, and a line drawn from an intermediate point between them is also shared with a line drawn from the intermediate point of the surge absorbing element 6 inserted between the communication line 2 and the power supply line 3. Alternatively, it may be connected via an arrester. Further, it is suitable to use two of the surge absorbing elements 6 inserted between the wires, the two having matching characteristics. However, from the connection point where three or more surge absorbing elements are inserted and at least one surge absorbing element is provided on at least both sides. The wires to be connected may be drawn. Further, the surge absorbing element 6 may be an arrester such as an arrester that suppresses a lightning surge by discharging. As described above, the present invention can be variously applied according to the gist and can take various embodiments.

[Effects of the Invention] As is clear from the above description, according to the lightning protection circuit of the present invention, a lightning surge protection circuit can be added to an extension connected to an internal circuit of a communication device that is not open to the outdoors. Therefore, even if a lightning surge is applied to any line, the internal circuit can be protected by suppressing the voltage difference generated between the communication line or the commercial power line and the extension line, and the resistance to lightning surge can be improved. Is an advantage. Further, since the lightning protection circuit of the present invention can be constituted only by a surge absorbing element and a lightning arrester, it can be applied without causing a large increase in size and weight, and is suitable for communication equipment aiming at miniaturization and weight reduction. Things. In addition, since the same configuration can be applied to the star wiring that is often used in business phones, design and manufacture are easy, and since it can be applied at a low price, there is an advantage that an economic burden is reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention, and FIG.
FIG. 3 is an explanatory view of the principle of the present invention, FIG. 3 is a circuit configuration diagram showing a second embodiment of the present invention, FIG. 4 is a circuit configuration diagram showing a third embodiment of the present invention, and FIG. 2) and 2 (b) are circuit diagrams of a conventional lightning protection circuit. 1 ... internal circuit (telephone), 2 ... communication line, 4 ... communication line (extension), 5 ... control line (extension), 6 ... surge absorbing element, 7 ... lightning arrester.

Claims (1)

(57) [Claims] 1. A communication device connected to a communication line and a commercial power line and to which one or more pairs of lines other than the communication line and the commercial power line are connected, the communication line, the commercial power line, and the communication line And two or more elements that absorb or discharge a lightning surge are connected in series between the lines connected to the communication device other than the commercial power line and not connected to the outside, A lightning protection circuit characterized in that connection points between elements that absorb or discharge lightning surge between lines are connected in common or via another element that absorbs or discharges lightning surge.