CA2281406A1 - Solid state protector for high frequency applications - Google Patents
Solid state protector for high frequency applications Download PDFInfo
- Publication number
- CA2281406A1 CA2281406A1 CA 2281406 CA2281406A CA2281406A1 CA 2281406 A1 CA2281406 A1 CA 2281406A1 CA 2281406 CA2281406 CA 2281406 CA 2281406 A CA2281406 A CA 2281406A CA 2281406 A1 CA2281406 A1 CA 2281406A1
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- diode
- electronic device
- solid state
- node
- tip
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Abstract
An excess voltage protector for protecting telecommunication equipment from surges on transmission lines utilizes a solid state electronic device. The electronic device conducts when it reaches a threshold voltage potential. The device is connected in a path between two ground nodes of a bridge circuit. The bridge circuit is made up of diodes. The diodes are oriented to steer excess voltage on tip and/or ring lines through the solid state device to ground. An additional diode is connected into the path between the two diodes in series with the solid state device. The additional diode brings the effective capacitance of the solid state device down, enabling the protector circuit to be utilized in higher frequency transmission lines.
Description
SOLID STATE PROTECTOR FOR HIGH FREQUENCY APPLICATIONS
Technical Field = Ttlis invention relates in general to excess voltage protectors, and particular to a solid state S circuit for protecting against excess voltage, particularly for use in high frequency applications.
Background Art Protectors are used with telephone lines to protect equipment from excess voltage occurring on the outside lines, such as from lightning strikes. The telephone company incoming lines are made up of a large number of twisted pairs of wires, one of the wires of each pair being refenred to as a tip wire and the other a ring wire. A voltage protector for each of the twisted pairs will connect to a ground wire. In the event of excess voltage between the tip and ring wires or between one of the wires and ground, the protector will conduct, creating a short to ground.
There are different types of protectors. One type in use is a gas tube type.
Electrical contacts are separated by a gap within a chamber which is evacuated of air and filed with an inert gas. While these work well, repeated voltage surges will cause sputtering on the insulator walls, causing the protectors to eventually require replacement. Also, the protection voltage level provided by gas tube is often too high to protect sensitive electronic circuits.
Another type of protector is a solid state protector such as a thyristor. When a voltage above a selected minimum is encountered, the solid state protector will conduct to ground. Solid state protectors work well for moderate current loads and moderate frequencies.
Solid state protectors are capable of conducting to ground repeatedly without damage occurring, unlike the gas tube type.
Solid state devices have also been used in bridge circuits which include diodes to steer the voltage. The diodes steer the excess voltage through the solid state device regardless of whether the excess voltage is on the tip line relative to the ring line, on the ring line relative to the tip line, or on both the tip and the ring lines relative to ground.
Telephone lines are increasingly being used for transmitting high frequency digital signals.
Frequencies of 2 to 30 megahertz are employed over telephone lines for data transmission. Solid state devices, such as thyristors and MOVs, have a fairly high capacitance, for example from 70 to 200 pf (~icofarads). This high capacitance creates a problem with very high frequency signals. It hampers impedance matching and detracts from the transmission abilities of the circuitry.
Disclosure of the Invention In this invention, a solid state electronic device such as a thyristor is utilized in a voltage protector circuit even for high frequency applications. The solid state device is connected into a rectifier bridge circuit made up of diodes. The diodes steer the excess current through the solid state device from the tip and ring lines to ground. A capacitive reduction device is connected into the path of the solid state device between two ground nodes of the rectifier bridge circuit. The capacitive reduction device is preferably a diode. It is sized to reduce the effective capacitance of the solid state device to an acceptable level.
Brief Description of the Drawings Figure 1 is an electrical schematic of a protector circuit constructed in accordance with this invention, with arrows indicating excess voltage occurring on a tip line relative to a ring line.
Figure 2 is an electrical schematic of the protector circuit of Figure 1, with arrows showing excess voltage on the ring line relative to the tip line.
Best Mode for Carryin~ Out the Invention Referring to Figure 1, protection circuit 11 is used for protecting excess voltage that may occur on a tip line 13, a ring line 15, or both the tip and ring lines 13, 15 relative to a ground line 17.
Protection circuit 11 is installed between incoming telephone lines and the equipment located at the user's facility. A first tip diode 19 has its anode connected to tip line 13 and its cathode connected to a first node 21. A second tip diode 23 has its cathode connected to tip line 13 and its anode connected to second node 25. Similarly, a first ring diode 27 has its anode connected to ring line 15 and its cathode connected to node 21. A second ring diode 29 has its anode connected to node 25 and its cathode connected to ring line 15.
S A first steering diode 31 has its cathode connected to node 21 and its anode connected to ground 17. A second steering diode 33 has its cathode to ground and its anode connected to node 25. A solid state electronic device 35 is connected in a line or path 37 between nodes 21, 25. Solid state device 35 is preferably a conventional thyristor, but it may also be a metal oxide varistor or a zener diode. Solid state device 35 is made up of various components in a chip and will break down and conduct once a selected voltage potential has been reached. Solid state device 35 has a fairly high capacitance, from 70 to 200 pf. Unless, reduced, this capacitance would be detrimental to high frequency transmission on tip and ring lines 13, 15.
The effective capacitance of solid state device 35 may be reduced by adding one or more diodes in series with solid state device 35 because a diode has a capacitance.
Two capacitive elements in series reduces the overall capacitance. This reduction will occur whether the diode is simply connected between solid state device 35 and a ground, or whether solid state device 35 is located within the steering diode circuit 11 as shown in the drawing. If solid state device 35 is simply connected to a ground, rather than in the steering diode circuit 11, the diodes may be connected in parallel with each other but oriented in opposite directions to enable solid state device 35 to be bidirectional.
In this embodiment, a diode 39, which may be the same type as diodes 19, 21, 23 and 25, is connected in path 37 in series with solid state device 35 to reduce the effective capacitance of solid state device 35. In the preferred embodiment, diode 39 is located between node 21 and solid state device 35. It has its anode connected to node 21 and its cathode connected to solid state device 35.
Because it is connected in series in path 37 with solid state device 35, the effective or overall capacitance of path 37 may be reduced xo an acceptable level. The overall or effective capacitance on path 37 is determined as follows:
Ceff= C1XC2/C1+C2 where C 1 is the capacitance of the solid state device and C2 is the capacitance of diode 39.
Consequently, the effective capacitance depends upon the capacitance of diode 39. A low capacitance for diode 39 reduces the effective capacitance more than a higher capacitance for diode 39, however, lowering the capacitance of diode 39 lowers its current carrying capabilities. Diode 39 is selected based on a balance of these two considerations. One source for diodes of the type described above is Teccor Corporation, Irving, Texas. It is possible to achieve higher bandwidths by utilizing addition diodes similar to diode 39 in series with thyristor 37.
In operation, under normal conditions voltage on tip or ring lines 13, 15 will not be enough to cause solid state device 35 to conduct. The various diodes of circuit 11 prevent any current flow to ground 17 unless solid state device 35 is conducting. Assuming an excess voltage appears on tip line 13 relative to ring line 15, arrows 41 indicate the current path. The current flows through diode 19 and is steered through diode 39 and diode 33 to ground 17. Dotted line arrows 43 indicate a 1 S similar excess potential difference, however with negative voltage. In this instance, current will flow through diode 31, diode 39, solid state device 35 and diode 23 to tip line 13. The various diodes 23, 27, 29, 31 and 33 steer the current path through diode 39 and through solid state device 35 in the same direction whether the excess voltage is negative or positive.
Similarly, if ring line 15 has excessive voltage relative to tip line 13, Figure 2 illustrates the flow paths. Arrows 45 indicates a positive voltage potential at ring line 15 that is in excess of an allowed amount relative to tip line 13. The voltage causes current to flow through diodes 27, 39, solid state device 35 and diode 33 to ground line 17. In the event of negative potential being excessive, azrows 47 indicate current flow through diodes 31, 39, solid state device 35 and diode 29 to ring line 15. If both tip and ring lines 13, 15 are at excessive voltage relative to ground line 17, then the flow paths will be the combination of Figures l and 2.
The invention has significant advantages. The addition of a capacitive element such as a diode in series with the solid state device will reduce the effective capacitance of the solid state device. The total effective capacitance of the protector circuit can thus be brought to a low enough level to allow frequency transmission up to 30 MHz.
While the invention has been shown in only one of its forms, it should be apparent to those S skilled in the art that it is not so limited but is susceptible to various changes without departing from the scope of the invention.
Technical Field = Ttlis invention relates in general to excess voltage protectors, and particular to a solid state S circuit for protecting against excess voltage, particularly for use in high frequency applications.
Background Art Protectors are used with telephone lines to protect equipment from excess voltage occurring on the outside lines, such as from lightning strikes. The telephone company incoming lines are made up of a large number of twisted pairs of wires, one of the wires of each pair being refenred to as a tip wire and the other a ring wire. A voltage protector for each of the twisted pairs will connect to a ground wire. In the event of excess voltage between the tip and ring wires or between one of the wires and ground, the protector will conduct, creating a short to ground.
There are different types of protectors. One type in use is a gas tube type.
Electrical contacts are separated by a gap within a chamber which is evacuated of air and filed with an inert gas. While these work well, repeated voltage surges will cause sputtering on the insulator walls, causing the protectors to eventually require replacement. Also, the protection voltage level provided by gas tube is often too high to protect sensitive electronic circuits.
Another type of protector is a solid state protector such as a thyristor. When a voltage above a selected minimum is encountered, the solid state protector will conduct to ground. Solid state protectors work well for moderate current loads and moderate frequencies.
Solid state protectors are capable of conducting to ground repeatedly without damage occurring, unlike the gas tube type.
Solid state devices have also been used in bridge circuits which include diodes to steer the voltage. The diodes steer the excess voltage through the solid state device regardless of whether the excess voltage is on the tip line relative to the ring line, on the ring line relative to the tip line, or on both the tip and the ring lines relative to ground.
Telephone lines are increasingly being used for transmitting high frequency digital signals.
Frequencies of 2 to 30 megahertz are employed over telephone lines for data transmission. Solid state devices, such as thyristors and MOVs, have a fairly high capacitance, for example from 70 to 200 pf (~icofarads). This high capacitance creates a problem with very high frequency signals. It hampers impedance matching and detracts from the transmission abilities of the circuitry.
Disclosure of the Invention In this invention, a solid state electronic device such as a thyristor is utilized in a voltage protector circuit even for high frequency applications. The solid state device is connected into a rectifier bridge circuit made up of diodes. The diodes steer the excess current through the solid state device from the tip and ring lines to ground. A capacitive reduction device is connected into the path of the solid state device between two ground nodes of the rectifier bridge circuit. The capacitive reduction device is preferably a diode. It is sized to reduce the effective capacitance of the solid state device to an acceptable level.
Brief Description of the Drawings Figure 1 is an electrical schematic of a protector circuit constructed in accordance with this invention, with arrows indicating excess voltage occurring on a tip line relative to a ring line.
Figure 2 is an electrical schematic of the protector circuit of Figure 1, with arrows showing excess voltage on the ring line relative to the tip line.
Best Mode for Carryin~ Out the Invention Referring to Figure 1, protection circuit 11 is used for protecting excess voltage that may occur on a tip line 13, a ring line 15, or both the tip and ring lines 13, 15 relative to a ground line 17.
Protection circuit 11 is installed between incoming telephone lines and the equipment located at the user's facility. A first tip diode 19 has its anode connected to tip line 13 and its cathode connected to a first node 21. A second tip diode 23 has its cathode connected to tip line 13 and its anode connected to second node 25. Similarly, a first ring diode 27 has its anode connected to ring line 15 and its cathode connected to node 21. A second ring diode 29 has its anode connected to node 25 and its cathode connected to ring line 15.
S A first steering diode 31 has its cathode connected to node 21 and its anode connected to ground 17. A second steering diode 33 has its cathode to ground and its anode connected to node 25. A solid state electronic device 35 is connected in a line or path 37 between nodes 21, 25. Solid state device 35 is preferably a conventional thyristor, but it may also be a metal oxide varistor or a zener diode. Solid state device 35 is made up of various components in a chip and will break down and conduct once a selected voltage potential has been reached. Solid state device 35 has a fairly high capacitance, from 70 to 200 pf. Unless, reduced, this capacitance would be detrimental to high frequency transmission on tip and ring lines 13, 15.
The effective capacitance of solid state device 35 may be reduced by adding one or more diodes in series with solid state device 35 because a diode has a capacitance.
Two capacitive elements in series reduces the overall capacitance. This reduction will occur whether the diode is simply connected between solid state device 35 and a ground, or whether solid state device 35 is located within the steering diode circuit 11 as shown in the drawing. If solid state device 35 is simply connected to a ground, rather than in the steering diode circuit 11, the diodes may be connected in parallel with each other but oriented in opposite directions to enable solid state device 35 to be bidirectional.
In this embodiment, a diode 39, which may be the same type as diodes 19, 21, 23 and 25, is connected in path 37 in series with solid state device 35 to reduce the effective capacitance of solid state device 35. In the preferred embodiment, diode 39 is located between node 21 and solid state device 35. It has its anode connected to node 21 and its cathode connected to solid state device 35.
Because it is connected in series in path 37 with solid state device 35, the effective or overall capacitance of path 37 may be reduced xo an acceptable level. The overall or effective capacitance on path 37 is determined as follows:
Ceff= C1XC2/C1+C2 where C 1 is the capacitance of the solid state device and C2 is the capacitance of diode 39.
Consequently, the effective capacitance depends upon the capacitance of diode 39. A low capacitance for diode 39 reduces the effective capacitance more than a higher capacitance for diode 39, however, lowering the capacitance of diode 39 lowers its current carrying capabilities. Diode 39 is selected based on a balance of these two considerations. One source for diodes of the type described above is Teccor Corporation, Irving, Texas. It is possible to achieve higher bandwidths by utilizing addition diodes similar to diode 39 in series with thyristor 37.
In operation, under normal conditions voltage on tip or ring lines 13, 15 will not be enough to cause solid state device 35 to conduct. The various diodes of circuit 11 prevent any current flow to ground 17 unless solid state device 35 is conducting. Assuming an excess voltage appears on tip line 13 relative to ring line 15, arrows 41 indicate the current path. The current flows through diode 19 and is steered through diode 39 and diode 33 to ground 17. Dotted line arrows 43 indicate a 1 S similar excess potential difference, however with negative voltage. In this instance, current will flow through diode 31, diode 39, solid state device 35 and diode 23 to tip line 13. The various diodes 23, 27, 29, 31 and 33 steer the current path through diode 39 and through solid state device 35 in the same direction whether the excess voltage is negative or positive.
Similarly, if ring line 15 has excessive voltage relative to tip line 13, Figure 2 illustrates the flow paths. Arrows 45 indicates a positive voltage potential at ring line 15 that is in excess of an allowed amount relative to tip line 13. The voltage causes current to flow through diodes 27, 39, solid state device 35 and diode 33 to ground line 17. In the event of negative potential being excessive, azrows 47 indicate current flow through diodes 31, 39, solid state device 35 and diode 29 to ring line 15. If both tip and ring lines 13, 15 are at excessive voltage relative to ground line 17, then the flow paths will be the combination of Figures l and 2.
The invention has significant advantages. The addition of a capacitive element such as a diode in series with the solid state device will reduce the effective capacitance of the solid state device. The total effective capacitance of the protector circuit can thus be brought to a low enough level to allow frequency transmission up to 30 MHz.
While the invention has been shown in only one of its forms, it should be apparent to those S skilled in the art that it is not so limited but is susceptible to various changes without departing from the scope of the invention.
Claims (10)
1. An excess voltage protector for protecting equipment connected to first and second lines of a telecommunication system, comprising in combination:
a plurality of bridge diodes connected into a rectifier bridge circuit having two input nodes adapted to be connected to the first and second lines and two ground nodes;
a pair of steering diodes, each connected to one of the ground nodes and adapted to be connected to an electrical ground, the steering diodes being reversed in polarity;
a solid state electronic device which conducts when substantially at a selected voltage potential and which does not conduct below said voltage potential, the electronic device being connected in a path between the two ground nodes so that voltage of either polarity in excess of the selected voltage potential will pass through the electronic device and to the ground; and a capacitive reduction device connected into the path with the electronic device for reducing the effective capacitance of the electronic device.
a plurality of bridge diodes connected into a rectifier bridge circuit having two input nodes adapted to be connected to the first and second lines and two ground nodes;
a pair of steering diodes, each connected to one of the ground nodes and adapted to be connected to an electrical ground, the steering diodes being reversed in polarity;
a solid state electronic device which conducts when substantially at a selected voltage potential and which does not conduct below said voltage potential, the electronic device being connected in a path between the two ground nodes so that voltage of either polarity in excess of the selected voltage potential will pass through the electronic device and to the ground; and a capacitive reduction device connected into the path with the electronic device for reducing the effective capacitance of the electronic device.
2. The voltage protector according to claim 1, wherein the electronic device comprises a thyristor.
3. The voltage protector according to claim 1, wherein the electronic device comprises a metal oxide varistor.
4. The voltage protector according to claim 1, wherein the capacitive reduction device comprises a diode.
5. The voltage protector according to claim 1, wherein the capacitive reduction device comprises a diode connected in series with the electronic device.
6 6. An excess voltage protector for protecting equipment connected to tip and ring lines of a telecommunication system, comprising in combination:
a first tip diode having an anode adapted to be connected to a tip line and a cathode connected to a first node;
a second tip diode having a cathode adapted to be connected to the tip line and an anode connected to a second node;
a first ring diode having an anode adapted to be connected to a ring line and a cathode connected to the first node;
a second ring diode having a cathode adapted to be connected to the ring line and an anode connected to the second node;
a first steering diode having a cathode connected to the first node and an anode adapted to be connected to a ground;
a second steering diode having an anode connected to the second node and a cathode adapted to be connected to the ground;
a solid state electronic device which conducts when substantially at a selected voltage potential and which does not conduct below said voltage potential, the electronic device being connected in a path between the first and second nodes; and a capacitive reduction diode connected into the path for reducing the effective capacitance of the solid state electronic device.
a first tip diode having an anode adapted to be connected to a tip line and a cathode connected to a first node;
a second tip diode having a cathode adapted to be connected to the tip line and an anode connected to a second node;
a first ring diode having an anode adapted to be connected to a ring line and a cathode connected to the first node;
a second ring diode having a cathode adapted to be connected to the ring line and an anode connected to the second node;
a first steering diode having a cathode connected to the first node and an anode adapted to be connected to a ground;
a second steering diode having an anode connected to the second node and a cathode adapted to be connected to the ground;
a solid state electronic device which conducts when substantially at a selected voltage potential and which does not conduct below said voltage potential, the electronic device being connected in a path between the first and second nodes; and a capacitive reduction diode connected into the path for reducing the effective capacitance of the solid state electronic device.
7. The voltage protector according to claim 6, wherein the electronic device comprises a thyristor.
8. The voltage protector according to claim 6, wherein the electronic device comprises a metal oxide varistor.
9. The voltage protector according to claim 1, wherein the capacitive reduction diode is connected in series with the electronic device.
10. An excess voltage protector for protecting equipment connected to tip and ring lines of a telecommunication system, comprising in combination:
a first tip diode having an anode adapted to be connected to a tip line and a cathode connected to a first node;
a second tip diode having a cathode adapted to be connected to the tip line and an anode connected to a second node;
a first ring diode having an anode adapted to be connected to a ring line and a cathode connected to the first node;
a second ring diode having a cathode adapted to be connected to the ring line and an anode connected to the second node;
a first steering diode having a cathode connected to the first node and an anode adapted to be connected to a ground;
a second steering diode having an anode connected to the second node and a cathode adapted to be connected to the ground;
a solid state electronic device comprising a thyristor or metal oxide varister, the electronic device being connected in a path between the first and second nodes; and a capacitive reduction diode connected into the path in series with the electronic device for reducing the effective capacitance of the electronic device.
a first tip diode having an anode adapted to be connected to a tip line and a cathode connected to a first node;
a second tip diode having a cathode adapted to be connected to the tip line and an anode connected to a second node;
a first ring diode having an anode adapted to be connected to a ring line and a cathode connected to the first node;
a second ring diode having a cathode adapted to be connected to the ring line and an anode connected to the second node;
a first steering diode having a cathode connected to the first node and an anode adapted to be connected to a ground;
a second steering diode having an anode connected to the second node and a cathode adapted to be connected to the ground;
a solid state electronic device comprising a thyristor or metal oxide varister, the electronic device being connected in a path between the first and second nodes; and a capacitive reduction diode connected into the path in series with the electronic device for reducing the effective capacitance of the electronic device.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US14690698A | 1998-09-04 | 1998-09-04 | |
| US09/146,906 | 1998-09-04 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2281406A1 true CA2281406A1 (en) | 2000-03-04 |
Family
ID=22519518
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2281406 Abandoned CA2281406A1 (en) | 1998-09-04 | 1999-09-02 | Solid state protector for high frequency applications |
Country Status (2)
| Country | Link |
|---|---|
| BR (1) | BR9905323A (en) |
| CA (1) | CA2281406A1 (en) |
-
1999
- 1999-09-02 CA CA 2281406 patent/CA2281406A1/en not_active Abandoned
- 1999-09-02 BR BR9905323-3A patent/BR9905323A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| BR9905323A (en) | 2000-09-12 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |