CN1802781A - Telecom circuit protection apparatus - Google Patents

Abstract

A telecom circuit protection apparatus includes a housing having at least first and second temperature responsive circuit protection devices, such as a fuse and a thyristor disposed therein. A first metal lead is connected to respective first terminals of the first and second circuit protection devices and is structured and arranged such as to transfer heat freely between the second circuit protection device and the first circuit protection device. A second metal lead is connected to a second terminal of the first device and a third metal lead is connected to a second terminal of the second device. The first, second and third metal leads extend from the housing. Advantageously, the portions of the first, second and third metal leads extending from the housing have reduced cross-sections to reduce heat loss from the apparatus and are formed and made solderable for use as connection points for surface mount connection to the apparatus. To protect multiple service lines, a circuit protector is provided for each of them. In this case, the multiple circuit protectors may advantageously be collocated in a common housing having either a common or separate ground terminal(s).

Description

Telecommunications Circuit Protection Devices

Cross-references to related literature

This application claims the benefit of U.S. Provisional Application Serial No. 60/476,051, filed June 4, 2003, entitled "Linking component's thermal properties to improve telecommunications protection circuit response to lightning surges and power cross faults Telecom protection circuit responses to lightening surge and powercross faults), the entire contents of which are hereby incorporated by reference.

Background technique

The present invention relates to circuit protection devices, and more particularly to telecommunication protection devices for protecting telecommunication equipment from a variety of anomalous patterns and potentially dangerous line events such as lightning surges and power crossings, the protection is not directed at applications indicating contrary design strategies.

Regulatory agencies require most telecommunications equipment directly connected to a service provider's outside lines to use protective measures to prevent catastrophic failure or fire in the event of an anomalous line event, such as lightning surges or power flows with high voltages (power crossings) unintentional contact. A typical regulatory approach for equipment qualification (as set forth, for example, in Telcordia GR 1089) is to subject the device to a series of well-defined overloads simulating typical anomalies. These prescribed tests are divided into two intensities; those protective devices must be non-functional Damage survived and those that may fail under unusual circumstances provided there is no fire or safety hazard.

Designing protection circuits for lightning surges and power cross faults with a distinction between surviving and controllable faults by this definition requires a balance between two competing approaches. Momentary lightning is a short-term high-energy event that can cause very high electric currents in the thousands of volts. Power crossing times often include contact with AC feeds carrying 600 volts or less and can be long-term. A typical solution for protection against these various faults consists of inserting a "temporary" fuse or PTC (Positive Temperature Coefficient) device with one or two galvanic wires (commonly designated "tip" in series with the "ring terminal") and placed between the equipment side and ground of each fuse/PTC with a thyristor or other voltage clamping device, thereby providing a fast-response means of clamping overvoltages to safe levels. Various circuit arrangements exist, but the basic requirement is one or more transient fuses/PTCs in each protection scheme.

To be suitable for this application, the fuse/PTC device must be capable of conducting, without openings, the instantaneous high peak currents associated with lightning surges to the associated voltage clamping device. This means that the fuse element should have a high enough I2t (to allow energy to pass) to preclude undesired device failure when its opening is subjected to "acceptable" surge levels. However, the fuse must also respond sufficiently to open within a specific time associated with a short circuit when subjected to a government defined low level overcurrent fault. Compliance with this second requirement limits the rated allowable current of the fuse, reducing its I2t roughly proportional to the number of fuse element blocks. These conflicting requirements severely limit the design parameters of fuses.

Contents of the invention

It is an object of the present invention to advantageously utilize the heat generated by the voltage clamping components of a circuit protection device under certain fault conditions. In particular, one of the objects of the present invention is to use material properties, thermodynamic principles and arrangement geometries to significantly enhance protection performance over prior art when equipment is subjected to lightning surges that are within the suppression capabilities of their associated voltage clamping devices Better resistance to undesirable clearing by allowing the use of stronger fusing devices during surges, but beyond the adjustment limit. Due to aspects of the present invention, the fuse also maintains its open capacity within the settling time limit when subjected to low current, power cross test conditions.

Another object of the present invention is to maximize the packing density of the necessary protection circuit components so that the device advantageously reduces the need to increase the circuit board real estate hosting the protection to the communication equipment.

Another object of the present invention is to reduce the assembly cost of communication equipment by providing equipment manufacturers with a protection solution model compatible with "surface mount" manufacturing technology and which can be set automatically in one cycle using "pick and place" devices on the circuit board.

These and other objects of the present invention are achieved by a circuit protection device comprising a housing having at least first and second temperature-responsive circuit protection devices, such as a fuse and a thyristor disposed therein, for each protection circuit service line. A first metal lead is connected to respective first terminals of the first and second circuit protection devices and is constructed and arranged to transfer heat from the second circuit protection device to the first circuit protection device. A second metal lead is connected to the second terminal of the first device; a third metal lead is connected to the second terminal of the second device, the first, second and third metal leads protrude from the shell, and the first metal lead Preconnected to the protection device, the second metal lead is preconnected to the communication line and the third metal lead is preconnected to a matching electrical ground.

Other features and advantages of the invention will become more apparent from the following description with reference to the corresponding drawings.

Description of drawings

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cutaway partial front view of one embodiment of a telecommunications circuit protector of the present invention, with portions removed for clarity, illustrating certain features of the invention.

FIG. 2 is a cutaway partial side view of the telecommunications circuit protector of FIG. 1 .

FIG. 3 is a front view of a spacer forming portion of the telecommunications circuit protector of FIGS. 1 and 2 .

4 is a side view showing a relaxed shape of a lead forming portion of the telecommunications circuit protector of FIGS. 1 and 2 .

FIG. 5 is a top view showing a terminal arrangement of the telecommunications protector of FIGS. 1 and 2 .

6 is an electrical schematic diagram of the telecommunications circuit protector of FIGS. 1 and 2 .

FIG. 7 is a top view showing the terminal arrangement of the interconnected telecommunications protector in the alternative embodiment of FIGS. 1 and 2 .

Figure 8 is an electrical schematic diagram of a telecommunications circuit protector in an alternative embodiment.

Detailed ways

All electrical components release some heat when they are in use. When using fuses or PTCs, this heat is fatal to their proper function and is the focus of this invention. When enough current is passed through a fuse link or PTC, the internally generated heat can overcome losses from its connection end and its surface to its surroundings, and its element temperature can reach its melting/high impedance point, opening the fuse or Drives the PTC into its current-limit mode.

Semiconductor devices, such as thyristors, also release heat when they are turned on. The power dissipated is the product of the voltage drop across its front and the current through it. Most of the heat generated is dissipated through the solder joints of the device, with a small amount maintained on its surface. Unlike fuses, excessive temperature rise can impair the proper function of semiconductors. The temperature of the equipment joints must be maintained below its factory specified maximum. In accordance with the present invention, the thermal properties of these two electrically connected devices are combined to affect symbiosis through physical location and thermodynamics, resulting in a device with significantly improved protection characteristics over the prior art.

1-4 illustrate a typical embodiment of a telecommunications circuit protection device to illustrate certain features of the present invention. This embodiment shows a protection device for two wires fed to a service line of a telecommunication device, comprising a surge fuse (F) and a voltage clamping device, such as a thyristor (T), as a temperature for each wire Response to circuit protection devices. It should however be realized that if only one wire of the service line needs to be protected, an embodiment using only one fuse and one thyristor may be used. Conversely, when more than one service line needs to be protected, more than two fuses and two thyristors may be used. In this case, the protectors for several lines may be connected to a common earth terminal, or installed at separate earth terminals.

Each anti-surge fuse (F) is placed vertically so that its lower cover is connected to the main circuit board (B) of the protection device via a lead wire (LL) of small cross-section to reduce heat loss. This helps the internal heat generated in the event of a fault to move by convection to the upper part of the fuse and create a favorable temperature gradient. The upper part of each fuse is closely connected to a thyristor (T) in the vertical direction, by welding between its upper end and the upper top of the fuse, and relying on an insulating and heat-conducting adjustment (S) spacer, its beneficial thickness ( best shown in Figure 3) on which is printed a solderable conductive pad (K) positioned between its lower end and the wall of the fuse (F).

A wide metal strip as a lead (L) is mounted on top of each fuse (F) and connected to the top, the upper lead of the thyristor (T) is soldered to the fuse (F) and a high temperature weld is created. Each lead (L) is bent down approximately 80 degrees and is formed in such a way that it leans against the thin top of the thyristor at a point (J) just beyond the semiconductor junction when its bottom is offset inward. When loaded each lead (L) made of conductive elastically deformable metal acting as a leaf spring, is preloaded by pressure at the exit point (W), thus creating a tight thermal connection at (J) . Figure 4 shows the lead (L) in its relaxed configuration. Although the thermal connections shown are mechanical in nature, it should be noted that a highly thermally conductive facilitator, such as a composite heat sink, may be applied at (J) to provide a connection between the junction of the thyristor and the top of the fuse. More efficient heat path. The thermal build-up of the wide strip (L) allows it to function as a temporary heat sink for the thyristor junction, thus favorably extending the time needed to drive the junction temperature of the small device beyond its allowable maximum in a fault condition. The bottom of each lead (L) is made of small cross-section and formed in such a way that it acts as an electrical connection, reducing heat conduction thereto, while at the same time connecting the upper top of the fuse (F) connected to it and the thyristor ( The connector between T) is connected to the equipment side wiring of the main circuit board (B). This formation may be "gull wing", "J-lead", or some other shape that facilitates connecting the device to the circuit board (B).

The lower lead of the thyristor (T) is connected with high temperature solder to a conductive printed board (K) on the insulating spacer (S), i.e., in this order, electrically connected via a lower lead (G) of small cross-section to the Ground point on main circuit board (B). In this way, both thyristors are connected to ground even though the printed board (K) has only one lead through it. A shell (C) with a flat top surface surrounding the entire structure to reduce heat transfer to the surrounding environment and to provide an advantageous means for automatically "pick and place" the protection device in one placement cycle.

Naturally, leads (L), (LL) and (G) terminate at terminals 1, 3, 4, 6 and 5 respectively, as shown in FIG. 5 . Intuitively, terminals 3 and 4 may represent the input and output terminals of the telecommunication protection device by "TIP", and terminals 1 and 6 may represent the input and output terminals by "RING".

As shown in FIG. 6, the fuse, the thyristor and the leads are electrically connected to each other. Under normal operating conditions, the signal current flowing through the fuse is well below its capacity and the associated thyristor remains non-conductive when no overvoltage occurs. The heat generated in the fuse in this condition will be easily dissipated through the leads connecting the device to the main circuit board.

Where an electrically isolated grounding point for each wire is required, it is desirable to provide a separate grounding connection where the circuit protector is used, which may be affected by thyristors being electrically isolated one from the other, by separating them advantageously on spacers (S) The printed board (K) also provides individual lower leads (G) for the thyristors. Figure 7 shows the physical location of the terminals of this embodiment and Figure 8 is its electrical schematic.

At low current, power cross-wire failure (eg 2.2 amps), the temperature of the fuse element climbs over time (as previously described) until cleared. Five mechanical devices are provided to accelerate this temperature rise compared to common, similar electrical protection circuits composed of discrete components.

The first mechanism is an increase in thermal insulation, obtained by connecting leads with small cross-sectional areas, rather than by soldering individual surface mount components to correspondingly sized pads on which a main circuit board or special circuit layer The resulting heat buildup is obtained.

The second mechanism metallically completes the main heat dissipation path from the junction of the thyristor (T) via its internal connecting lead connection structure, to the top of its associated fuse (F) and thus unimpeded to its connection ( F) Top of internal components. This full metal path ensures that heat transfer is maximized.

The third type of mechanism injects the additional heat occurring on the top surface of the thyristor (T) case by approximating it with a wide metal strip in the upper part of the connected fuse (F) and carries a strong pressure on the top of the case against the thyristor (T) , and solder to the top bonding block of the fuse (F) and the upper lead of the thyristor (T). This thermally conductive connection spacer (S) performs a secondary function by simultaneously transferring the heat occurring at the lower terminal of the thyristor (T) directly to the upper part of the body of the connected fuse (F).

A fourth mechanism enables mounting of the fuse (F) on a vertical plane so that heat convection within the body of the fuse (F) and high heat build-up occurring at the top of the fuse (F) promote internal heat generation towards the fuse (F ) upper part of the movement. In use the device on the protector should be oriented vertically so as to orient the fuse horizontally, the aforementioned heat convection effect will be ineffective but the beneficial temperature gradient is created by the metal soldered to the top of the fuse (F) The concentrating heat block provided will continue to absorb heat even if the fuse (F) is on a horizontal surface.

Finally, the presence of the shell (C) provides more heat retention by blocking airflow through either thermal circuit. Additionally, the housing is sized such that the height of the circuit protector is minimized, and this area, commonly referred to as the "solid state", will fill the printed circuit board. The housing is dimensioned such that when the device is integrated in the housing, its lower edge bends each lead (L) inwardly relative to its associated thyristor (T), thereby ensuring a tight thermal connection.

Collectively, these thermal management mechanisms are shown to reduce typical fuse clear times by up to 70% at low overcurrent levels. This accelerated clearing under minimum power crossing test conditions allows the use of more properly ratioed fuses with higher I2t energy and letthrough capacity. This, in turn, provides survivability beyond prior art when the protection device is subjected to high current/sustained short circuits, such as pulses from lightning surges, resulting in a protection solution with response characteristics that exceed those used for the two rigorous test levels Adjusted minimum demand value in case of failure.

In the event of a sustained short circuit, high peak current fault condition, the additional heat buildup provided by the wide bottom lead draws heat away from the thyristor (T) junction during transient events, and then through its narrowed bottom connection and main circuit board. its release. Additionally, the body of the fuse (F) in this case acts as a thermal buffer, allowing it to cooperate with the metal lower lead and the spacer (S) to attenuate the temperature rise in the associated thyristor (T), whose Individual heat build-up is low. In this form of fault, a significant portion of the impulse energy injected into the circuit input is dissipated on the thyristor (T). Should the connection overheat due to improper heat dissipation, a failure may occur, rendering the protective device either inoperable or vulnerable to concurrent lightning. The present invention gathers most of the heat from the individual protection circuits and makes them fit together so that they react in unison to suppress the semiconductor peak temperature during this "fast transient" event.

Prior art designs typically limit protection circuit solutions to include discrete, serial placement of components on the main printed circuit board of the device, or require circuit pins similarly placed on small, "standard size" circuit cards or layers , devices designed as SIP (Single Inline Package) require hand insertion, "Through the Hole" type installation. As a comparison, the telecommunications protection device described here, in accordance with certain features of the present invention, is most easily configured as a DIP (dual inline package), making it easy to integrate with standard, "surface mount", "pick and place" and "infrared Reflow” soldering technique compatible. This compatibility allows installation of SMT (Surface Mount Technology) protection circuits requiring minimal board space, and individual placement periods result in significant loss compensation and board "real state" compensation.

Although the invention has been described with reference to particular embodiments thereof, other changes and modifications, and other applications, will be apparent to those skilled in the art. For example, different forms of voltage clamping elements can be used, and PTCs can be used in place of fuses. Other physical configurations can also be used to arrange the protective circuit components to achieve the desired beneficial thermal interaction, which results in an improved protective circuit response over the prior art. Further, as noted, multiple line circuit protectors can be deployed within a common enclosure. In this case, multiple circuit protectors may share a common ground terminal, or each may have its own ground terminal, by extending the connection spacers across them. It is therefore preferred that the invention not be limited by its precise disclosure but only by the appended claims.

Claims (23)

1. A telecommunication circuit protection device, comprising: a shell; at least one first temperature-responsive circuit protection device disposed within the housing; at least one second temperature-responsive circuit protection device disposed within said housing; a first metal lead connected to respective first terminals of the first and second circuit protection devices and constructed and arranged such that the first metal lead transfers heat from one circuit protection device to the other circuit protection device; a second metal lead connected to the second terminal of the first device; and A third metal lead connected to the second terminal of the second device, the first, second and third metal leads extending from the housing. 2. The telecommunications circuit protection device of claim 1, wherein the first circuit protection device is a fuse. 3. The telecommunications circuit protection device of claim 2, wherein the fuse is a surge fuse. 4. The telecommunications circuit protection device of claim 1, wherein the first circuit protection device is a positive temperature coefficient protector. 5. The telecommunications circuit protection device of claim 1, wherein the second circuit protection device is a voltage clamping device. 6. The telecommunications circuit protection device of claim 5, wherein the voltage clamping device is a thyristor. 7. The telecommunications circuit protection device of claim 1, wherein a first lead is placed over the first and second means and is connected to respective upper terminals of the first and second means, the first lead being arranged so that it abuts the The first device is attached to form a highly thermally conductive connection. 8. The telecommunications circuit protection device of claim 7, wherein the first lead is made of a thermally conductive elastically deformable material, and is folded downwardly toward the portion formed by the second device by approximately 80 degrees such that the first lead A spring loaded force is applied to the top of the second device to form a mechanically maintained tight thermal connection. 9. The telecommunications circuit protection device of claim 1, wherein the first, second and third metal lead portions extending from the housing have reduced cross-sectional areas and are formed and made solderable to Used as a connection point for surface mount devices to an external circuit. 10. A telecommunication circuit protection device, comprising a shell; at least first, second, third and fourth temperature-responsive circuit protection devices disposed within said housing; a first metal lead connected to respective first terminals of the first and second circuit protection devices, and the first metal lead is constructed and arranged to transfer heat between the second circuit protection device and the first circuit protection device; a second metal lead connected to respective first terminals of the third and fourth circuit protection devices, and the second metal lead is constructed and arranged to transfer heat between the fourth circuit protection device and the third circuit protection device; third and fourth metal leads connected to respective second terminals of the first and third circuit protection devices; a fifth metal lead connected to respective second terminals of the second and fourth circuit protection devices; First, second, third, fourth and fifth metal leads extend from the housing. 11. The telecommunications circuit protection device of claim 10, wherein the first and third circuit protection devices are fuses. 12. The telecommunications circuit protection device of claim 11, wherein the fuse is a surge fuse. 13. The telecommunications circuit protection device of claim 10, wherein the first and third circuit protection devices are positive temperature coefficient protectors. 14. The telecommunications circuit protection device of claim 10, wherein the second and fourth circuit protection devices are voltage clamping devices. 15. The telecommunications circuit protection device of claim 14, wherein the voltage clamping device is a thyristor. 16. The telecommunications circuit protection device of claim 10, wherein a first lead is placed over the first and second means and connected to respective upper terminals of the first and second means, the first lead being arranged to abut against The second device is to form a mechanically maintained tight thermal connection, and wherein the second lead is placed above the third and fourth devices and connected to the respective upper terminals of the third and fourth devices, the second lead is arranged against A fourth means to form a mechanically maintained tight thermal connection. 17. The telecommunications circuit protection device of claim 16, wherein the first lead is folded downwardly about 80 degrees with its downward portion so that it is assembled against the second device to form a mechanically maintained tight thermal connected, and the second lead is folded down about 80 degrees with its vertical portion so that it is assembled against the fourth device to form a mechanically maintained tight thermal connection. 18. The telecommunications circuit protection device of claim 10, wherein the first, second, third, fourth, and fifth metal leads extending from the housing have reduced cross-sectional areas, and the metal leads extending from the housing First, second, third, fourth and fifth metal leads are formed and made solderable for use as connection points of the surface mount device to an external circuit. 19. A telecommunications circuit protection device, comprising: a shell; at least first, second, third and fourth temperature-responsive circuit protection devices disposed within the housing; a first metal lead connected to respective first terminals of the first and second circuit protection devices and constructed and arranged to transfer heat between the second circuit protection device and the first circuit protection device; a second metal lead connected to the respective first terminals of the third and fourth circuit protection devices and constructed and arranged to transfer heat between the fourth circuit protection device and the third circuit protection device; third and fourth metal leads connected to respective second terminals of the first and third circuit protection devices; a fifth metal lead connected to the second terminal of the second circuit protection device; a sixth metal lead connected to the second terminal of the fourth circuit protection device; First, second, third, fourth, fifth and sixth metal leads extending from the housing. 20. A telecommunications circuit protection device, comprising: a shell; a first fuse disposed within said housing shell and a first temperature-responsive voltage clamp connected to the first fuse; A first lead is placed on the first fuse and the first temperature-responsive voltage clamping device, and is connected to the respective upper terminals of the fuse and the first temperature-responsive voltage clamping device, and the first lead is along the first temperature-responsive voltage clamp. an edge of the clamp extends downwardly against an edge of the first temperature-responsive voltage clamp to form a mechanically maintained tight thermal connection; a second lead connected to the second terminal of the first fuse; a second fuse disposed within said housing shell and a second temperature responsive temperature clamp connected to the second fuse; A third lead is placed on the second fuse and the second temperature-responsive voltage clamping device, and is connected to the respective upper terminals of the second fuse and the second temperature-responsive voltage clamping device, and the third lead is along the second temperature-responsive voltage clamping device. one side of the voltage clamp extends downwardly against one side of the second temperature responsive voltage clamp to form a mechanically maintained tight thermal connection; An insulating thermally conductive spacer having a thermally conductive printed board thereon is placed between a low terminal of the first temperature responsive voltage clamp and a low terminal of the second temperature responsive voltage clamp such that the spacer One end is connected to one of the lower terminals, and the spacer is connected to the other lower terminal with the other end of the spacer; a fourth lead connected to a second terminal of the second fuse; and A fifth lead is connected to the printed board on the insulating spacer, and the first, second, third, fourth and fifth metal leads have tips extending from the housing. 21. The telecommunications circuit protection device of claim 20, wherein the first, second, third, fourth and fifth metal lead portions extending from the housing have reduced cross-sectional areas and are formed and made Solderable for use as a connection point for surface mount devices to an external circuit. 22. A telecommunications circuit protection device, comprising: a shell; a first fuse disposed within said housing and a first temperature-responsive voltage clamp connected to the first fuse; a first lead, which is placed on the first fuse and the first temperature-responsive voltage clamping device and connected to the respective upper terminals of the fuse and the first temperature-responsive voltage clamping device, the first lead along the first temperature-responsive voltage clamping device; an edge of the voltage clamp extends downwardly against an edge of the first temperature responsive voltage clamp to form a mechanically maintained tight thermal connection; a second lead connected to the second terminal of the first fuse; a second fuse disposed within said housing and a second temperature responsive temperature clamp connected to the second fuse; a third lead, which is placed on the second fuse and the second temperature-responsive voltage clamping device and connected to the respective upper terminals of the second fuse and the second temperature-responsive voltage clamping device, the third lead along the second temperature-responsive voltage clamping device; the responsive voltage clamp extends downwardly against one side of the second temperature responsive voltage clamp to form a mechanically maintained tight thermal connection; An insulating thermally conductive spacer having first and second electrically insulating thermally conductive printed boards thereon is positioned between the first and second temperature responsive voltage clamping means such that the first thermally conductive plate is electrically connected to the first temperature responsive voltage clamp a low terminal of the device, and the second thermally conductive plate is electrically connected to a low terminal of the second temperature-responsive voltage clamp device; a fourth lead connected to a second terminal of the second fuse; a fifth lead is connected to the first thermally conductive plate on the insulating spacer and A sixth lead is connected to the second thermally conductive plate on the insulating spacer, and the first, second, third, fourth and fifth metal leads have tips extending from the housing. 23. The telecommunications circuit protection device of claim 22, wherein the first, second, third, fourth, fifth and sixth metal lead portions extending from the housing have reduced cross-sectional areas, And formed and made solderable for use as a surface mount device connection point to an external circuit.

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