JP5966137B2 - Surge protection device for communication path - Google Patents

Description

  The present invention relates to a surge protection device for a communication path, and more particularly to a surge protection device in a high-speed data transmission path.

  A surge generated by a lightning strike or the like causes a great damage to an electronic device. For this reason, a surge protection device (SPD) for protecting electronic devices from surges has been studied. Although various configurations of SPDs have been studied, the basic function is to allow current to escape to ground when an abnormal voltage occurs.

  There are various surge intrusion paths, and communication cables are one of them. With the recent development of data transmission, various electronic devices are connected to a data transmission network. For this reason, surge countermeasures for data transmission lines composed of communication cables are becoming increasingly important (see, for example, Patent Document 1).

  Security devices such as surveillance cameras are often installed outdoors, and security devices are often connected to a router or the like via a long communication cable. Longer communication cables make surges more likely to enter. Furthermore, the surge caused by lightning includes high frequency components up to about 1 MHz. For this reason, even if an SPD is inserted into one end of a long communication cable so that it can be grounded in a direct current manner when a surge occurs, a standing wave due to a high-frequency component of a lightning surge exists at the other end. High frequency high voltage remains. For this reason, there exists a possibility that the electronic device connected to the end on the opposite side to SPD attached to the communication cable may be damaged.

JP 2001-327069 A

  Even when a long communication cable is connected to the device, it is conceivable to install SPDs at both ends of the communication cable in order to protect the device from the lightning surge by avoiding the influence of the standing wave of the lightning surge. However, when conventional SPDs are attached to both ends of a communication cable, there is a problem that high-speed data transmission becomes difficult because high-frequency characteristics are not good. In addition, since a large number of electronic devices are connected to the data network, a large number of cables are connected to a network device such as a router, and it is required to reduce the size of the SPD. Moreover, since the voltage of a lightning surge becomes high in connection with an outdoor device, high resistance is required as SPD.

  It is an object of the present invention to satisfy these conflicting requirements and to realize a small-sized and highly durable surge protection device for a communication path that can be cascaded at the far end and near end in a high-speed data transmission line. Objective.

  One aspect of a surge protection device for a communication path according to the present invention is provided on a wiring board having a signal line pair and a ground pattern surrounding the signal line pair, and at both ends of the wiring board, and is connected to each other by the signal line pair. The external connection connector and a three-pole arrester element mounted on the wiring board, and at least a part of the signal line pair is a parallel line, and the three-pole arrester element is a first terminal provided on each of the end faces. And a second terminal, and a third terminal provided between the first terminal and the second terminal, the lower end of the first terminal is connected to one of the signal line pair, and the lower end of the third terminal The part is connected to the other of the signal line pair, and the lower end of the second terminal is connected to the ground pattern and functions as a ground plane.

  According to the surge protector for a communication path according to the present invention, it is possible to realize a surge protector for a communication path that is small in size, highly resistant, and capable of high-speed data transmission.

It is a circuit diagram which shows the circuit structure of the surge protective device of this embodiment. (A) And (b) shows the wiring board of the surge protection apparatus which concerns on one Example, (a) It is a top view which shows a 1st layer, (b) is a top view which shows a 4th layer. (A) And (b) is a graph which shows the insertion loss of a surge protective device, (a) is a case where a ground plane is provided, (b) is a case where a ground plane is not provided. It is a figure which shows the insertion loss of the surge protection apparatus which concerns on one Example. It is a figure which shows the crosstalk characteristic of the surge protective device which concerns on one Example.

  The surge protection device (SPD) for a communication path according to this embodiment is provided on a wiring board having a signal line pair and a ground pattern surrounding the signal line pair, and at both ends of the wiring board, and is connected to each other by the signal line pair. And a three-pole arrester element mounted on a wiring board, and at least a part of the signal line pair is a parallel line, and the three-pole arrester element is provided on each of the end faces. A terminal and a second terminal; and a third terminal provided between the first terminal and the second terminal. The lower end of the first terminal is connected to one of the signal line pair, and the third terminal The lower end is connected to the other of the signal line pair, and the lower end of the second terminal is connected to the ground pattern and functions as a ground plane.

  In the SPD of the present embodiment, the ground pattern may be provided in parallel with the signal line pair.

  In the SPD of the present embodiment, the wiring board is a multilayer board having a ground plane layer, and the ground plane layer and the ground pattern may be connected.

  The SPD of this embodiment may further include a voltage limiting element connected between the signal line pair.

  The SPD of the present embodiment accommodates an external ground terminal connected to the ground pattern and a wiring board so as to expose the external ground terminal, and the surface opposite to the external ground terminal faces the structure side. A case for fixing may be further provided.

  The SPD of this embodiment has a circuit configuration as shown in FIG. The corresponding terminals of the two external connection connectors 21 are connected to each other by the signal line pair 13 including the signal line 11 and the signal line 12. A three-pole arrester element 15 is connected between the signal line pair 13. The first terminal T 1 of the three-pole arrester element 15 is connected to the signal line 11, the third terminal T 3 is connected to the signal line 12, and the second terminal T 2 is connected to the external ground terminal 31. A voltage limiting element 17 is connected between the signal line 11 and the signal line 12.

  The shields of the two external connection connectors 21 are connected by a shield line 22, and the shield line 22 is connected to the first terminal T 1 of the three-pole arrester element 23. The second terminals T 2 and T 3 of the three-pole arrester element 23 are connected to the external ground terminal 31. The three-pole arrester element 23 connected to the shield line 22 may be a two-pole arrester element.

  In the case of a 1000BASE-T standard data transmission line established by the Institute of Electrical and Electronics Engineers (IEEE), four signal line pairs 13 are provided, and an 8-pin modular jack (RJ-45) is used for the external connector 21. .

  The three-pole arrester elements 15 and 23 are gas discharge tubes (Gas) in which three electrodes are arranged so as to face each other in an insulating tube such as ceramics filled with an inert gas such as neon or argon. Discharge Tube: GDT). A three-pole arrester element having a surge withstand according to the required protective properties may be used. However, when there is a possibility of using it outdoors, it is preferable to use a device having a large discharge current. It is preferable to use a surge withstand of about 10 kA. In addition, as both end faces of the three-pole arrester element, those having the entire surface made of metal are used.

  Since the voltage limiting element 17 has a delay in discharging the GDT, the voltage limiting element 17 is installed to suppress a high voltage in an extremely short time interval until the discharge starts. For this reason, the surge tolerance (current tolerance) may be about several tens of A, but an element that operates at high speed is preferable. In order not to deteriorate the high frequency characteristics, it is preferable that the capacitance is small.

  When a surge of a predetermined voltage or more occurs in the signal line pair 13, the first terminal T 1 and the third terminal T 3 of the three-pole arrester element 15 are discharged and become conductive, and the surge is grounded. I can escape. In addition, the voltage limiting element 17 operates until immediately before the discharge of the three-pole arrester element 15 and the voltage increase due to the surge can be suppressed.

  According to the IEEE 1000BASE-T standard, the signal frequency band is about 80 MHz. Furthermore, in the next generation standard, the frequency band is about 250 MHz. Accordingly, simply assembling a circuit having a configuration as shown in FIG. 1 does not provide sufficient high-frequency characteristics, and high-speed data transmission cannot be performed. For this reason, it is necessary to design as a high frequency circuit.

  Since a high-speed data transmission communication line uses a balanced core, it is important to arrange the two signal lines constituting the signal line pair in the circuit so as to be parallel. For this reason, the signal line pairs are arranged on the wiring board so as to be as parallel lines as possible.

  The wiring board is provided with a ground pattern in a blank area not directly related to signal transmission. The ground pattern is preferably provided so as to surround the signal line pair so as to be parallel to the signal line pair. As a result, characteristic degradation due to parasitic oscillation or the like can be reduced. The area of the ground pattern should be large. The phrase “the ground pattern is arranged in parallel with the signal line pair” means that the sides of the ground pattern and the signal line pair that face each other are parallel to each other. However, the ground pattern need not be arranged in parallel to the signal line pair in all portions.

  The three-pole arrester element has a shape including a first terminal and a second terminal provided on each of the end faces, and a third terminal provided between the first terminal and the second terminal. The three terminals are connected to the signal line pair, and the second terminal is connected to the ground pattern. When the first terminal and the second terminal provided at both ends of the three-pole arrester element are connected to the signal line pair, the distance between the signal line pair needs to be substantially the same as the width of the three-pole arrester element. In the case of a three-pole arrester element with a surge resistance of 10 kA, the general size is about 6 mm in diameter and about 8 mm in width. For this reason, when connecting the first terminal and the second terminal to the signal line pair, it is necessary to greatly increase the interval between the signal lines constituting the signal line pair in the portion where the three-pole arrester element is connected. It becomes difficult. In particular, in a surge protection device for a high-speed data transmission path that requires mounting of four circuits, it is difficult to arrange the three-pole arrester element. However, by connecting the first terminal and the third terminal provided at the center to the signal line, the interval between the signal lines can be halved, which is advantageous for downsizing.

  In addition, the first terminal and the lower end of the third terminal of the three-pole arrester element are directly connected to the signal line pair, and the lower end of the second terminal is directly connected to the ground pattern. If each terminal of the three-pole arrester element is connected to the signal line pair and the ground pattern by a wire or the like, an unnecessary reactance component is added, which affects the high-frequency characteristics. However, an increase in reactance component can be suppressed by directly connecting each terminal to the signal line pair and the ground pattern. Further, the second terminal, which is a metal plate, is connected substantially perpendicular to the ground pattern, so that the second terminal functions as a ground plane. Thereby, generation | occurrence | production of parasitic oscillation etc. can be suppressed. In this case, it is preferable that the end surface on which the second terminal of the three-pole arrester element is formed is a second terminal whose entire surface is a metal plate.

  In the SPD of this embodiment, since the second terminal of the three-pole arrester element functions as a ground plane, there is no need to separately provide a ground plane connected to the ground pattern. However, a ground plane may be provided separately. When a ground plane is separately provided, it is preferable that a metal plate connected to the ground pattern and substantially perpendicular to the wiring board is provided on at least one side end of the wiring board. The length of the metal plate is preferably equal to or greater than the length of the wiring board. The height of the metal plate is preferably higher than the height of the three-pole arrester element mounted on the wiring board. Moreover, you may provide a metal plate in a both-ends part. Furthermore, it is good also as a structure which covers the upper part of a wiring board with a metal plate. When providing a signal line pair on each of the front and back surfaces of the wiring board, it is preferable to provide a metal plate serving as a ground plane also on the back surface side.

  In order to further improve the high frequency characteristics, it is preferable that the wiring board is a multilayer board and at least one layer is a ground plane layer connected to the ground pattern. Providing the ground plane layer increases the effect of shielding the signal line pair. Further, the ground area can be increased, and an effect of suppressing parasitic oscillation and the like can be obtained.

  In the case of the standard of 1000BASE-T, four signal line pairs are required. In order to reduce the size of the SPD, two pairs of signal lines are arranged on both the first surface (front surface) and the second surface (back surface) of the wiring board, and the first surface and the second surface A three-layer structure in which a ground plane layer is provided therebetween may be employed. Moreover, it is good also as a 4 layer structure which laminated | stacked two double-sided board | substrates. In this case, the ground plane layer may be two layers.

  The external ground terminal for connecting the SPD to the external ground is preferably provided on the same surface as the external connection connector of the wiring board. Moreover, it is preferable that the height of the external connection connector and the height of the external grounding terminal are aligned. By doing so, the thickness of the SPD can be reduced.

  It is preferable that the case accommodating the SPD can be fixed with the surface opposite to the external grounding terminal facing the structure. By fixing the external grounding terminal on the side opposite to the structure, the ground wire can be easily connected to the external grounding terminal. In many cases, a plurality of SPDs on the router side are attached to a DIN rail that is a structural material of the control panel. Also, the position of the SPD is often moved by changing the port of the router. By providing the external ground terminal on the surface opposite to the DIN rail, access to the external connection terminal is facilitated, and the SPD is facilitated.

    It is sufficient that at least one SPD of the present embodiment is attached in the middle of the data network cable. The attachment position is not particularly limited, but it is preferable to attach it as close as possible to the hub. Moreover, it is more preferable to attach SPD to both ends of the cable. By attaching SPDs to both ends of the cable, electronic devices connected to both ends of the cable can be protected against a standing wave of lightning surge that tends to occur in a long cable. Since the SPD of the present embodiment has good high frequency characteristics, even when it is inserted at both ends of the cable, high-speed data transmission of 1 gigabit / second or more can be performed. Further, it is easy to reduce the size, and the arrangement is easy even when a plurality of data cables are wired. Further, even when the size is reduced, a GDT having a surge withstand of 10 kA or more can be used, and a sufficient surge withstand can be ensured.

  Hereinafter, the SPD device according to the present invention will be described in more detail with reference to examples. In addition, arrangement | positioning etc. of the circuit board shown in a present Example and an element are examples, and do not limit invention.

  An SPD having the circuit configuration shown in FIG. 1 was realized using a four-layer wiring board. 2 (a) and 2 (b) show the first layer (front surface) and the fourth layer (back surface) of the substrate, respectively. For the sake of explanation, the pattern and connected elements are indicated by solid lines. The length of the wiring board was about 80 mm and the width was about 24 mm.

  As shown in FIGS. 2A and 2B, two pairs of signal lines 13 are arranged on the first layer 111 and the fourth layer 114, respectively. The first layer 111 connects the signal line pair 13 including the signal line 11 that connects the terminals J1 of the RJ-45 standard external connector 21 and the signal line 12 that connects the terminals J2 and the terminal J3. The signal line pair 13 including the signal line 11 and the signal line 12 connecting the terminals J6 is provided. The fourth layer 114 is connected to the signal line pair 13 including the signal line 11 that connects the terminals J4 and the signal line 12 that connects the terminals J5, and the signal line 11 and the terminals J8 that connect the terminals J7 to each other. A signal line pair 13 including the signal line 12 is provided.

  Each signal line pair 13 is a parallel line in which two signal lines 11 and 12 are parallel in a portion of 90% or more of the total length. Further, each signal line pair 13 is arranged so as to be surrounded by the ground pattern 121. In the first layer 111 and the fourth layer 114, the ground pattern 121 is arranged so as to be parallel to each signal line pair 13, and the area thereof is arranged to be 50% or more of the total area of the first layer 111. The second and third layers were ground plane layers and connected to the ground patterns 121 of the first layer 111 and the fourth layer 114 by through-hole wiring. The external connection connector 21 and the external ground terminal 31 are provided on the first layer 111. The case of the external connector 21 and the external ground terminal 31 are not directly connected to the ground plane layer.

  For the three-pole arrester elements 15 and 23, a commercially available GDT (Epcos Corporation: T30-A230XMSD) having a diameter of about 6 mm, a width of 8 mm, and a surge withstand of 10 kA was used. As the voltage limiting element 17, a commercially available surge clamper (Origin Electric Co., Ltd .: SCL510) having a peak reverse voltage of 5 V, a surge withstand capability of 50 A, and a small capacitance was used.

  3A and 3B show the results of confirming the effect of providing a ground plane. FIG. 3A shows the result of measuring the transmission characteristics when a ground plane is provided using a spectrum analyzer (manufactured by Advantest: R3361C). FIG. 3B shows the case where no ground plane is provided. Shows the results. When no ground plane is provided, it is clear that the insertion loss changes greatly and parasitic oscillation occurs. Thus, by providing the ground plane, the high frequency characteristics can be greatly improved.

  FIG. 4 shows transmission characteristics measured with a cable analyzer (DTX-1800, manufactured by FLUKE) with the SPD of this embodiment connected to both ends of an IEEE category 5e standard cable having a length of 100 m. As shown in FIG. 4, it was confirmed that the SPD of this example has a sufficiently small insertion loss. In addition, as shown in FIG. 5, it was confirmed that the crosstalk characteristics have a margin with respect to the standard even when connected to both ends of a long cable.

The surge protection device of the present invention is small, highly durable, and capable of high-speed data communication, and is particularly useful as a surge protection device for high-speed data transmission paths.

DESCRIPTION OF SYMBOLS 11 Signal line 12 Signal line 13 Signal line pair 15 3 pole arrester element 17 Voltage limiting element 21 External connection connector 22 Shield line 23 3 pole arrester element 31 External ground terminal 111 1st layer 114 4th layer 121 Ground pattern

Claims (4)

A wiring board having a signal line pair and a ground pattern surrounding the signal line pair;
External connection connectors provided at both ends of the wiring board and connected to each other by the signal line pair;
A three-pole arrester element mounted on the wiring board;
In the signal line pair, two signal lines constituting the same are provided on the same surface of the wiring board, and at least a part is a parallel line,
The three-pole arrester element has a first terminal and a second terminal provided on each of the end faces, and a third terminal provided between the first terminal and the second terminal,
The first terminal has a lower end portion directly connected to one of the signal line pairs,
The third terminal has a lower end connected directly to the other of the signal line pair,
The communication terminal surge protection device , wherein the second terminal is directly connected to the ground pattern at a lower end portion of an end face whose entire surface is a metal plate and functions as a ground plane.   The surge protection device for a communication path according to claim 1, wherein the ground pattern is arranged in parallel with the signal line pair. The wiring board is a multilayer board having a ground plane layer,
The surge protection device for a communication path according to claim 1 or 2, wherein the ground plane layer and the ground pattern are connected. An external grounding terminal connected to the ground pattern;
The case further comprising: a case for housing the wiring board so as to expose the external ground terminal, and fixing the surface to the structure with a surface opposite to the external ground terminal facing the structure. The surge protection device for a communication path according to any one of 1 to 3.

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