JP2003018743A - Protector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protector that protects user communication equipment from a surge. SOLUTION: The signal line 13 in the protector 10 is separated by a first capacitor and the ground line 14 is separated by a second capacitor. A surge arrester 19 is provided on the separated line terminal 12 side. A high-pass filter 20 that includes the first capacitor 15 is provided on the equipment terminal 11 side. The high-pass filter 20 is formed by connecting the signal line 13 and the ground line 14 with inductance 18. Through this means, the signal line 13 and the ground line 14 on the equipment terminal 11 side have roughly the same potential in low frequencies, thereby preventing the ingress of a surge (surge voltage occurring between the two lines). Ingress from the line terminal 12 side is blocked by the first capacitor 15 and the second capacitor 16 while the surge is at the same time consumed by lightning protection 19 such as an arrester. Through this means, user communication equipment connected to the equipment terminal 11 is at least protected from a surge.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protector for protecting communication equipment from surge noise such as lightning surge. In particular, a high-pass filter is installed inside the protector to keep the signal line from the communication device side and the ground line at approximately the same potential at low frequencies, and to prevent the generation of surge voltage between both lines even when a surge enters. Protector to protect communication equipment. INDUSTRIAL APPLICABILITY The present invention can be applied to, for example, a CATV protector that enables TV reception and data communication.

[0002]

2. Description of the Related Art Conventionally, there has been a problem of destruction of domestic communication equipment due to lightning surge. As a system using a home communication device, for example, there is a CATV data communication system shown in FIG. This is a system in which the computer device 110 is connected to a CATV line to perform bidirectional data communication. The computer device 110 is 10BASE-T.
The cable 112 is connected to the cable modem 115, and the cable modem 115 is connected to the CATV line via the coaxial cable 125 and the protector 100. In this conventional system, each device has a common power supply line 130. Also, the casing of the cable modem 115 is grounded by the outer conductor of the coaxial cable 125 and the protector 100, but the casing of the computer device 110 is not grounded because the computer device 110 is arbitrarily installed by the user. Often.

When there is a lightning strike near this system, for example, a surge enters from the CATV line side. Then, the communication device may be destroyed by it. Therefore, conventionally, for example, the protector 100 is provided with an arrester 103 and an inductance 104, which are lightning arresters, between the signal line 101 on the CATV line side, that is, the input IN side and the ground line 102, as shown in FIG. It was absorbed.

However, as shown in FIG. 4, a surge caused by a lightning strike may enter from a power transmission line. For example, when there is a lightning strike on the ground wire of the power transmission line, a lightning surge (3 KV to 5 kV) is grounded and enters the power supply line 130 via the pole transformer 131. The surge that has entered flows into the housing of the computer device 110 through the power supply line 130. However, the casing of the computer device 110 is not grounded, and the casing of the cable modem 115 is grounded. As a result, a surge voltage is applied between the terminal on the cable modem 115 side of the 10BASE-T cable 112 that connects the computer device 110 and the cable modem 115 and the housing of the cable modem 115, and since this interval is narrow, insulation is provided at this portion. Destruction had occurred. Therefore, FIG.
As shown in FIG. 1, a protector 1 that connects the outer conductor of the coaxial cable 125 to the ground line 102 via the capacitor 105.
00 has been devised. That is, at low frequencies, all communication devices connected to the protector 100 are floated from the ground to prevent surge current from flowing into the ground. As a result, the induction of the surge is prevented and the cable modem 1
It protected communication equipment such as 15.

[0005]

However, when the protector 100 shown in FIG. 6 is used, the entire communication equipment is in a floating state with respect to the ground due to the capacitor 105 inserted in the protector 100. At the capacitor 105, a surge voltage is induced from the outer conductor of the coaxial cable 125 to the center conductor, which causes the cable modem 11
The surge voltage intrudes into the signal line of the RF circuit of No. 5, which causes a new problem that the dielectric breakdown of the RF circuit occurs.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide a high-pass filter at a device terminal inside a conventional protector so that a surge having a low frequency is generated in a communication device. It is to prevent passage to the signal line of. That is, by providing a high-pass filter, the signal line of the cable inside the house and the ground line are made to have approximately the same potential at low frequencies, thereby preventing the induction of surge voltage on the signal line, and at least in the house connected to the protector. Is to protect the communication equipment of.

[0007]

In order to solve the above problems, the protector according to claim 1 has a device terminal connected to a communication device and a line terminal connected to a communication line. A protector for protecting a communication device from various surges, the first capacitor separating a signal line into a device terminal side and a line terminal side, and a signal line on the device terminal side separated by the first capacitor. It is characterized in that the ground line is provided with a high-pass filter that makes the ground line have substantially the same potential at low frequencies to prevent generation of a surge voltage between both lines and passes a high-frequency signal which is a data signal. The above ground line is a ground line corresponding to a signal line through which a signal propagates, and it is not premised that this is actually grounded. That is, it is also used when the ground line is not actually grounded to the ground.

This protector is inserted between the communication device and the communication line. The first capacitor provided in the protector separates the signal line into a device terminal side and a line terminal side in the house at low frequencies. As a result, the surge of low frequency that has entered from the line is blocked. Therefore, it is possible to protect the in-home communication device from the surge generated on the line side.

On the other hand, in this state, when a lightning surge enters the ground side of the equipment terminal through the outer conductor of the coaxial cable, the high-pass filter provided on the equipment terminal side causes the outer conductor to move to the center conductor. Induction of lightning surge is prevented. That is, the lightning surge is prevented from passing through the signal line of the communication device. This high pass filter is, for example, an inductance. Since it is an inductance, the signal line and the ground line can have substantially the same potential at low frequencies.
Further, the RF signal can pass from the protector to the communication device as it is.

When a low-frequency surge enters the outer conductor of the equipment terminal from the inside of the house, the high-pass filter causes the signal line on the equipment terminal side, that is, the inside of the house and the outer conductor (ground line) to have substantially the same potential. , Surge voltage does not occur between both lines. That is, at least the home communication device connected to the device terminal of the protector of the present invention is not destroyed. That is, the protector protects the home communication device from the surge from the line, the surge from the device terminal side, and both surges. The communication device is a communication device related to data communication such as a computer device and a cable modem device,
It also includes AV equipment that receives or transmits / receives video signals and audio signals, which are one type of data signals.

Further, the protector according to claim 2 is characterized in that the ground line is provided with a second capacitor for separating the ground line into a device terminal side and a line terminal side. The second capacitor is
At low frequencies, the ground line is separated into the equipment terminal side and the line terminal side in the house, and it plays a role of preventing the surge current from flowing into the ground. This prevents the generation of the surge voltage due to the voltage drop of the ground resistance. This prevents damage to the home communication device.

Although the insertion of the second capacitor prevents the surge current from flowing into the ground,
Conversely, a surge voltage is applied between the signal line on the device terminal side and the ground line. For example, if a coaxial cable is connected to the device terminal, the coaxial cable has a capacitor component,
In the conventional case, a partial voltage (surge voltage partial voltage) corresponding thereto is generated. However, according to the present invention, the signal line of the device terminal and the ground line have substantially the same potential due to the high-pass filter, so that the voltage division of the surge voltage does not occur between both lines in this case as well. That is, although the mechanism of surge induction is different between the case where the second capacitor is not provided in the ground line and the case where it is provided, the occurrence of the surge is prevented in both cases by the installation of the high-pass filter of the present invention.

Further, in the protector according to the third aspect, the high-pass filter is an inductance provided between the signal line on the device terminal side and the ground line. This inductance prevents a low-frequency component such as lightning surge from entering the signal line from the ground line. On the other hand, the high frequency signal is prevented from leaking to the ground line due to the inductance and can propagate through the signal line without loss.

According to a fourth aspect of the present invention, in the invention of the third aspect, the high-pass filter is provided between the inductance, the connection point with the signal line and the signal line on the device terminal side. It is characterized by being configured by a T-type high-pass filter composed of three capacitors. This inductance has a high reactance with respect to a high frequency signal, and the first capacitor and the third capacitor have a low reactance with respect to a high frequency signal. Therefore, according to the above-mentioned composition, a high frequency signal can be mutually passed from a device terminal side and a line terminal side. On the other hand, the inductance has a low reactance with respect to a low frequency signal, and the first capacitor and the third capacitor have a high reactance. Therefore, by adjusting both constants, the signal line of the device terminal and the ground line can be made to have substantially the same potential with respect to a surge having a low frequency.
This makes it possible to easily reduce the surge voltage applied to the signal line and the ground line on the device terminal side. That is,
Home communication equipment can be easily protected from surge. Since it is a T type, the impedance viewed from the line terminal side to the equipment terminal side and the impedance viewed from the equipment terminal side to the line terminal side can be easily matched by selecting the circuit constant. As a result, the high frequency signal which is the data signal is not reflected. Therefore, it is possible to protect the home communication device from the surge and guarantee high-quality data communication.

According to another aspect of the protector of the present invention, the equipment terminal is an RF terminal, and the RF terminal is an insulated RF in which the outer conductor is connected to the ground line on the line terminal side by the second capacitor. It is a terminal. In this configuration, the device terminal and the second capacitor are replaced with an insulation type RF terminal. That is, the step of providing the second capacitor can be omitted. Therefore, when manufacturing the protector according to any one of claims 1 to 4, the manufacturing can be facilitated.

Further, the protector according to claim 6 is provided with a lightning arrester between the signal line on the line terminal side and the ground line separated by the first capacitor, and the ground line is grounded via the casing on the line terminal side. It is characterized by being. Here, the arrester is, for example, an inductance and / or a gas arrester. With this configuration, the surge that has entered from the line is blocked by the first capacitor and is bypassed and / or absorbed by the lightning arrester. Therefore, it is possible to reliably prevent the surge from entering the line. Therefore, the protector can surely protect the in-home communication device from the surge that has entered from the line.

Further, the protector according to claim 7 is characterized in that the communication line is a CATV communication line. CATV
In the communication line, for example, a high frequency signal of 10 MHz or more,
Video data, audio data, and character data are transmitted. This high frequency signal can be completely separated from the low frequency surge on the frequency axis. That is, claim 1
The protector according to claim 6 can protect those communication devices from a surge without affecting the CATV communication system at all. Therefore, the protector effectively acts on the CATV communication system.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to the examples below. (Embodiment) FIG. 1 shows a protector according to this embodiment. The figure is a circuit diagram. The protector of this embodiment protects the home communication device from both surges from the power supply line and the CATV line. The protector 10 of the present invention includes a device terminal 11 connected to a home communication device, a line terminal 12 connected to a CATV communication line, a signal line 13, and a ground line 1.
4, a first capacitor 15, a second capacitor 16, a third capacitor 17, an inductance 18, and a lightning arrester 19. The arrester 17 is, for example, an arrester which is a kind of discharge tube filled with argon gas or neon gas, or a PNPN semiconductor element. Both of these are elements that conduct electricity at a voltage equal to or higher than a predetermined value. In the present specification, the term ground line 14 is a line corresponding to the signal line 13, and is used regardless of whether it is actually grounded to the ground.

In the above structure, the first capacitor 15 separates the signal line 13 into a device terminal side and a line terminal side at low frequencies. The second capacitor 16 separates the ground line 14 into a device terminal side and a line terminal side at low frequencies. This is because even if a low-frequency surge that entered from the CATV line side enters, the device terminal 1
This is a configuration that blocks invasion to the first side. In addition, the lightning arrester 19 is configured to absorb a surge from the line side. As a result, the surge that has entered from the line terminal 12 does not enter the equipment terminal 11 side. That is, the home communication device can be protected against a surge from the line side.

Further, in the above structure, the first capacitor 1
5, the third capacitor 17, and the inductance 18 are
The T-type high pass filter 20 is configured. In the high pass filter 20, the inductance 18 has a high reactance with respect to a high frequency signal, and the third capacitor 1
7 has a low reactance with respect to a high frequency signal. This is because the high frequency signal is transmitted from the device terminal 11 side and the line terminal 1
The configuration is such that the two sides pass each other. Further, by making the high-pass filter a T type, the impedance constant can be easily adjusted by adjusting the circuit constant. That is, the reflection of the high frequency signal due to the insertion of the high pass filter can be reduced as much as possible. Therefore, the configuration has almost no effect on data communication.

On the other hand, the inductance 18 has a low reactance with respect to a low frequency signal, and the third capacitor 17 has a high reactance. Therefore, if both constants are adjusted, the signal line 1 on the device terminal 11 side against a surge of low frequency
3 and the ground line 14 can be set to substantially the same potential. This is a configuration in which, even if a surge enters the ground line 14 on the device terminal 11 side, the signal line 13 and the ground line 14 have substantially the same potential, thereby reducing the applied surge voltage. The reason for adopting the configuration is as follows.

For example, assume that a surge enters the ground line 14, for example, from the device terminal 11 side in the conventional state where there is no high-pass filter 20, especially the inductance 18. In this case, the second capacitor 16 prevents the surge current from flowing into the ground. However, conversely, a surge voltage is applied between the signal line 13 and the ground line 14 on the device terminal 11 side. This is because there is a capacitor component between the center conductor and the outer conductor of the coaxial cable that is connected to the device terminal 11, and accordingly a partial voltage is applied as a surge voltage between both conductors. As a result, the home communication device connected to the device terminal 11 is destroyed.

In this embodiment, as described above, the signal line 13
Since the high-pass filter 20, especially the inductance 18, is provided between the signal line 13 and the ground line 14, the signal line 13 and the ground line 14 have substantially the same potential, and the surge voltage applied between both lines is reduced. Further, since the first capacitor 15 and the second capacitor 16 are provided, passage of surge current is also blocked. In other words, both the signal line 13 and the ground line 14 on the device terminal 11 side largely fluctuate with respect to the ground when the surge enters, but the potential difference between them is maintained at a predetermined value. Thereby, at least the home communication device connected to the device terminal 11 of the protector of the present invention is not destroyed. That is, the protector of the present invention can protect the connected home communication device against the surge from the line terminal side, the surge from the device terminal side, and both surges.

(Modification) Although one embodiment showing the present invention has been described above, various modifications are possible. For example, in the above embodiment, the third capacitor 17 is provided and the high pass filter 20 is of the T type.
If the reflection at 0 is not large, it may be omitted as shown in FIG. 2 in some cases. That is, the inductance 18 may be directly provided on the center conductor and the outer conductor at the entrance of the device terminal 11 of the conventional protector. Further, in the above embodiment, the arrester 1 is provided for the surge from the line terminal 12.
Although it is configured to absorb only by 9, inductance 1
It may be provided with 9a to bypass it. The surge can be reduced more reliably.

In the above embodiment, the equipment terminal 11 is described as an RF terminal composed of a center conductor and an outer conductor.
It may be an insulation type RF terminal 30 as shown in FIG.
In other words, the device terminal 11 and the second capacitor 16 are isolated RF
The terminal 30 may be substituted. In that case, as shown in FIG. 3A, the other end of the inductance 18 is connected to the outer conductor of the insulated RF terminal 30. Even with this configuration, it is possible to obtain the same effect as that of the above embodiment.
This can be further modified as shown in FIG. That is, a high-pass filter (first capacitor 15,
When the reflection due to the third capacitor 17 and the inductance 18) is small, the third capacitor 17 may be omitted and the insulated RF terminal 30 may be used. In that case, the inductance 18 is directly connected between the center conductor and the outer conductor. It can also be configured in this way.

Further, in the above-mentioned embodiment and modification, the ground line 14 is used.
Although the example in which the second capacitor 16 is provided is described above, it may be removed in some cases. When the second capacitor 16 is removed, the potential of the ground line 14 fluctuates due to a surge current flowing into the ground (due to the voltage drop due to the ground resistance), but as described above, the inductance 18 causes the signal line 13 on the device terminal 11 side. Since the ground line 14 and the ground line 14 have substantially the same potential, no surge voltage is induced in the signal line 13. The present invention is also effective for the conventional protector having such a structure.

In the above embodiment, the communication line is a CATV.
Although a line is used, another communication line may be used. For example, a LAN system in which a central device and a plurality of terminal devices are connected by a coaxial cable may be used. That is, it may be a protector for protecting the LAN system.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a protector according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a protector according to a modification of the present invention.

FIG. 3 is a circuit diagram of a protector including an insulation type RF terminal according to a modification of the present invention.

FIG. 4 is an explanatory diagram of a surge intrusion route according to a conventional example.

FIG. 5 is a circuit diagram showing a conventional protector.

FIG. 6 is a circuit diagram of a protector using a conventional insulated RF terminal.

[Explanation of symbols]

10 ... Protector 11 ... Device terminal 12 ... Line terminal 13 ... Signal line 14 ... Ground track 15 ... First capacitor 16 ... Second capacitor 17 ... Third capacitor 18 ... Inductance 19 ... Lightning arrester 19a ... Inductance

Claims (7)

[Claims] 1. A protector having a device terminal connected to a communication device and a line terminal connected to a communication line for protecting the communication device from various surges, wherein a signal line is connected to the device terminal side. The first capacitor separated to the line terminal side and the device terminal side separated by the first capacitor have the signal line and the ground line at substantially the same potential at a low frequency to prevent the induction of surge voltage, thereby preventing a data signal. A protective device having a high-pass filter that passes the high-frequency signal. 2. The protector according to claim 1, wherein the ground line is provided with a second capacitor that separates the ground line into the device terminal side and the line terminal side. 3. The high-pass filter comprises an inductance provided between the signal line on the device terminal side and the ground line.
The protector described in. 4. The high-pass filter is a T-type high-pass filter including the inductance, a third capacitor provided between a connection point with the signal line and a signal line on the device terminal side, and the first capacitor. The protector according to claim 3, wherein 5. The device terminal is an RF terminal, and the RF terminal is an insulated RF terminal in which an outer conductor is connected to the ground line by the second capacitor. The protector according to any one of 4 above. 6. A lightning arrester is provided between the signal line on the side of the line terminal and the ground line separated by the first capacitor, and the ground line is grounded via a casing on the side of the line terminal. The protector according to any one of claims 1 to 5. 7. The protector according to claim 1, wherein the communication line is a CATV communication line.