CN110556810A

CN110556810A - Surge protection device

Info

Publication number: CN110556810A
Application number: CN201910971569.5A
Authority: CN
Inventors: 闵龙; 宋东健
Original assignee: Dongguan Littelfuse Electronic Co Ltd
Current assignee: Dongguan Littelfuse Electronic Co Ltd; Littelfuse Dongguan Manufacturing Facility
Priority date: 2019-10-12
Filing date: 2019-10-12
Publication date: 2019-12-10

Abstract

The application discloses surge protection device includes: a varistor having opposing first and second surfaces, the varistor further having a via extending through the first and second surfaces; a gas discharge tube having a first end and a second end, at least a portion of the gas discharge tube being positioned within the through-hole, wherein the second end is positioned within the through-hole; a first electrode in electrical contact with the first surface of the varistor; a common electrode in electrical contact with the second surface of the varistor and in electrical contact with the second end located within the via; a second electrode in electrical contact with the first end of the gas discharge tube. The surge protection device disclosed by the application can reduce the space occupied by a Metal Oxide Varistor (MOV) and a Gas Discharge Tube (GDT) on a circuit board, and is more beneficial to the miniaturization of the device.

Description

Surge protection device

Technical Field

The present application relates generally to surge protection devices and, in particular, to surge protection devices based on varistors, especially metal oxide varistors.

Background

Surge Protection Devices (SPDs) are a type of protective device commonly used in electronic equipment to limit transient over-voltages in circuits to a range of voltages that the equipment or system can withstand, or to bleed strong currents to ground, thereby protecting the protected electronic equipment or system from damage due to surge voltages or surge currents.

in one commonly used Surge Protection Device (SPD), a Metal Oxide Varistor (MOV) is used as its main component. In such applications, however, the MOV will inevitably suffer from follow-up current and leakage current damage. In normal use, high leakage currents will flow through the MOV, causing the MOV to degrade, shortening its useful life.

Disclosure of Invention

At least one object of the present application is to provide a surge protection device capable of reducing a space occupied by a Metal Oxide Varistor (MOV) and a Gas Discharge Tube (GDT) on a circuit board, more facilitating miniaturization of the device.

According to the present application, there is provided a surge protection device comprising:

a varistor having opposing first and second surfaces, the varistor further having a via extending through the first and second surfaces;

A gas discharge tube having a first end and a second end, at least a portion of the gas discharge tube being positioned within the through-hole, wherein the second end is positioned within the through-hole;

A first electrode in electrical contact with the first surface of the varistor;

A common electrode in electrical contact with the second surface of the varistor and in electrical contact with the second end located within the via;

A second electrode in electrical contact with the first end of the gas discharge tube.

in at least one embodiment, the surge protection device further has an insulating layer for electrically insulating the first electrode from the second electrode.

in at least one embodiment, the first electrode and/or the second electrode is comprised of a patterned electrode layer.

in at least one embodiment, a patterned electrode layer constituting the first electrode covers the first surface of the varistor and has an opening exposing the through-hole.

In at least one embodiment, the piezoresistors are metal oxide piezoresistors.

In at least one embodiment, the first end of the gas discharge tube is located outside the through-hole; the surge protection device further has an insulating layer for electrically insulating between the first electrode and the second electrode, and a sum of a thickness of the insulating layer and a thickness of the first electrode is equal to a distance between the first end portion and the first surface.

In at least one embodiment, the insulating layer at least partially covers the first electrode, and the second electrode is located on a side of the insulating layer remote from the first electrode.

In at least one embodiment, the second end is flush with the second surface.

In at least one embodiment, the common electrode is layered and covers both the second surface and the second end.

In at least one embodiment, the first surface has a first metallization layer thereon, and the first electrode is in electrical contact with the first metallization layer; and/or

The second surface has a second metallization layer thereon, and the common electrode is in electrical contact with the second metallization layer.

According to the surge protection device provided by the application, the space occupied by the piezoresistor and the Gas Discharge Tube (GDT) on the circuit board can be remarkably reduced, so that the device is more beneficial to miniaturization. Further, the surge protection device provided according to the present application can also reduce lead wires and solder joints introduced into the circuit, and thus can respond to overvoltage more quickly.

drawings

The above features, technical features, advantages and modes of realisation of the present application will be further described in the following detailed description of preferred embodiments in a clearly understandable manner, in conjunction with the accompanying drawings. The drawings are only for purposes of illustrating and explaining the present application and are not to be construed as limiting the scope of the present application. Wherein:

Fig. 1 shows a perspective view of a surge protection device according to an embodiment of the present application;

fig. 2 shows a top view of a surge protection device according to an embodiment of the present application;

Fig. 3 shows a bottom view of a surge protection device according to an embodiment of the present application;

Fig. 4 illustrates a cross-sectional view of a surge protection device according to an embodiment of the present application along the line C-C shown in fig. 2 and 3;

Fig. 5 shows a side view of the surge protection device shown in fig. 1.

Detailed Description

In order to more clearly understand the technical features, objects, and effects of the present application, embodiments of the present application will now be described with reference to the accompanying drawings.

In an improved Surge Protection Device (SPD), a Gas Discharge Tube (GDT) is added in series with the MOV. In such a surge protection device having a gas discharge tube connected in series with the MOV, the gas discharge tube will disconnect the MOV from the power supply, thereby completely eliminating the presence of leakage current and significantly extending the life of the MOV. In addition, since the GDT cuts off the power supply, there is no follow-up current after the surge process such as lightning stroke. Furthermore, the MOV is connected in series with the gas discharge tube and the total capacitance is much smaller than either of the MOV and the gas discharge tube, which will greatly reduce the impact on the high frequency circuit.

Such surge protection devices having a gas discharge tube connected in series with an MOV have been widely used. However, since the additionally added gas discharge tube needs to occupy a large space on the circuit board, which is in conflict with the miniaturization demand of electronic products, it is not suitable for space-limited applications.

according to one embodiment of the present application, a Surge Protection Device (SPD) is provided. Fig. 1 shows a perspective view of the surge protection device. Fig. 2 and 3 show top and bottom views, respectively, of a surge protection device. Fig. 4 shows a cross-sectional view along the line C-C shown in fig. 2 and 3. Fig. 5 shows a side view of the surge protection device shown in fig. 1.

As shown in fig. 1-5, a surge protection device 01 provided according to one embodiment of the present application includes a metal oxide varistor 10 and a gas discharge tube 20. Wherein the surge protection device 01 has a first surface 11 and a second surface 12 opposite. The surge protection device 01 as a whole may have, for example, a square profile and have a certain thickness. The surge protector 01 has a through hole 19 in a thickness direction perpendicular to the first surface 11 and the second surface 12, and the through hole 19 penetrates the first surface 11 and the second surface 12. As shown in fig. 4 and 5, the gas discharge tube 20 is, for example, a cylinder having opposite first and second ends 21 and 22. The gas discharge tube 20 has electrodes (not shown in the figure) at a first end 21 and a second end 22, respectively, for supplying power to the gas discharge tube 20. The gas discharge tube 20 is at least partially located within the through hole 19, in particular at least the second end 22 is located within the through hole 19. Preferably, as shown in fig. 4, most of the volume of the gas discharge tube 20 is located in the through hole 19 with the end face of the second end 22 flush with the second surface 12 of the metal oxide varistor so that the end face of the second end 22 of the gas discharge tube 20 is in the same horizontal plane as the second surface 12 of the metal oxide varistor.

By adopting such a structure in which the Gas Discharge Tube (GDT) is inserted into the Metal Oxide Varistor (MOV), the space occupied by the Surge Protection Device (SPD) on the circuit board can be significantly reduced, thereby contributing to more miniaturization of the device.

In addition, the through-opening 19 can have, for example, a circular cross-section to match a cylindrical gas discharge tube 20. The diameter of the through-hole 19 may be slightly larger than the diameter of the gas discharge vessel 20 to prevent stress between the metal oxide varistor 10 and the gas discharge vessel 20. A filling material may be provided between the inner wall of the through hole 19 and the gas discharge vessel 20 to enhance the fixation between the metal oxide varistor 10 and the gas discharge vessel 20. The filler material may be, for example, an adhesive material, preferably an electrically insulating adhesive material, such as an insulating resin or the like.

The present application also discloses an electrode structure of a surge protection device having such a structure that a Gas Discharge Tube (GDT) is inserted into a Metal Oxide Varistor (MOV). As shown in fig. 1-5, the surge protection device 01 has a first electrode 31 located on the first surface 11 of the metal oxide varistor 10. The first electrode 31 is in electrical contact with the first surface 11 to enable power supply to the metal oxide varistor 10. The surge protection device 01 also has a second electrode 32 in electrical contact with the first end 21 of the gas discharge tube 20 to effect power supply to the gas discharge tube 20. In addition, as shown in fig. 3-5, the surge protection device 01 also has a common electrode 40. The common electrode 40 is an electrode common to the metal oxide varistor 10 and the gas discharge tube 20, and is electrically connected to the metal oxide varistor 10 and the gas discharge tube 20 to electrically connect the two.

as can be deduced from the above-described structure, in the surge protection device provided by the present application, the current path is the first electrode 31-the first surface 11 of the metal oxide varistor 10-the second surface 12 of the metal oxide varistor 10-the common electrode 40-the second end 22 of the gas discharge tube 20-the first end 21 of the gas discharge tube 20-the second electrode 32. It can be seen that in the surge protection device provided by the present application, the metal oxide varistor 10 is connected in series with the gas discharge tube 20. Therefore, under the prerequisite that the surge protection device that this application provided does not influence the device miniaturization, realized the series connection of metal oxide piezo-resistor and gas discharge tube, eliminated the existence of electric leakage current, showing and prolonged MOV's life, can not have follow current after surge processes such as thunderbolt, total electric capacity is reduced, greatly reduced is to high frequency circuit's influence. Further, the surge protection device provided according to the present application can also reduce lead wires and solder joints introduced into the circuit, and thus can respond to overvoltage more quickly.

The first electrode 31 and/or the second electrode 32 may be respectively composed of a patterned electrode layer.

as shown in fig. 1-2, the patterned electrode layer constituting the first electrode 31 at least partially covers the first surface 11 of the metal oxide varistor 01 and has a square opening exposing the through-hole 19 of the metal oxide varistor 01. The first electrode 31 includes a covering portion 311 covering the first surface 11 of the metal oxide varistor 01 and an extending portion 312 extending out of the first surface 11 of the metal oxide varistor 01. Wherein the extension 312 is used to enable electrical connection of the surge protection device 01 to an external circuit.

The patterned electrode layer constituting the second electrode 32 at least partially covers the first end portion 21 of the gas discharge vessel 20. The second electrode 32 comprises a cover 321 covering the first end portion 21 of the gas discharge vessel 20 and an extension 322 extending beyond the first surface 11 of the metal oxide varistor 01. Wherein the extension 322 is used to make the electrical connection of the surge protection device 01 to an external circuit.

The extension 312 of the first electrode 31 and the extension 322 of the second electrode 32 may be located on the same side of the surge protection device 01, i.e. the region extending from the same side to the outside of the metal oxide varistor 01, thereby constituting a radial lead. The extension 312 of the first electrode 31 and the extension 322 of the second electrode 32 may be parallel to each other.

the patterned electrode layer constituting the first electrode 31 and/or the second electrode 32 may be formed of, for example, a metal foil.

As shown in fig. 1-2 and 4-5, a surge protection device 01 provided according to an embodiment of the present application further includes an insulating layer 33, the insulating layer 33 serving to electrically insulate between the first electrode 31 and the second electrode 32. The insulating layer 33 may be located between the first electrode 31 and the second electrode 32 in height. The insulating layer 33 at least partially covers the first electrode 31, and the second electrode 32 is located above the insulating layer 33. The insulating layer 33 may ensure that the first electrode 31 and the second electrode 32 do not contact each other, and ensure that there is a sufficient gap between the first electrode 31 and the second electrode 32 when a discharge process occurs. The insulating layer 33 may be an insulating coating applied on the metal oxide varistor 10, or may also be a layered insulator attached to the metal oxide varistor 10 by an adhesive.

The first end 21 of the gas discharge tube 20 may not be located in the through hole 19 of the metal oxide varistor 10, but may protrude from the through hole 19 a distance d above the first surface 11. For example, the height of the gas discharge vessel 20 may be greater than the thickness of the metal oxide varistor 10 by a difference d. The thickness of the insulating layer 33 is preferably set to: the sum of the thicknesses of the insulating layer 33 and the first electrode 31 is equal to the distance d. In this way, the top surface of the insulating layer 33 and the top surface of the first end portion 21 of the gas discharge tube 20 will be in the same horizontal plane, which allows the second electrode 32, which covers both the insulating layer 33 and the first end portion 21 of the gas discharge tube 20, to be at the same height, thereby preventing the second electrode 32 from being bent.

As shown in fig. 3-5, the common electrode 40 may be layered, for example, may have a circular profile. Preferably, the second end 22 of the gas discharge vessel 20 is aligned with the second surface 12 of the metal oxide varistor 10. The common electrode 40 on the second surface 12 of the metal oxide varistor 10 also covers the second end 22 of the gas discharge vessel 20. According to the surge protection device provided by the present application, the metal oxide varistor 10 and the gas discharge tube 20 have the common electrode 40 in common, which reduces the number of lead wires and solder joints introduced into the circuit, and thus can respond to overvoltage more quickly.

Furthermore, it should be noted that, although not shown in the drawings, the metal oxide varistor 10 may have a metallization layer on the first surface 11 and/or the second surface 12. The first electrode 31 and the common electrode 40 are electrically contacted to the metallization layers of the first surface 11 and/or the second surface 12 to enable a high quality electrical connection between the first electrode 31 and the common electrode 40 and the metal oxide varistor 10.

the first electrode 31 may be electrically connected to the first surface 11 of the metal oxide varistor 10 by soldering, for example to a metallised layer (if any) of the first surface 11 of the metal oxide varistor 10. The second electrode 32 may be electrically connected to the electrode on the first end 21 of the gas discharge tube 20 by welding. The common electrode 40 may be electrically connected to the second surface 12 of the metal oxide varistor 10 by soldering, for example to a metallised layer (if any) on the second surface 12 of the metal oxide varistor 10, whilst the common electrode 40 is also electrically connected to an electrode on the second end 22 of the gas discharge vessel 20 by soldering, for example. The welding process may be, for example, low temperature soldering. In the embodiment of low-temperature soldering, if an undesirable heat generation phenomenon occurs during discharge, the first electrode 31, the second electrode 32, and the common electrode 40 are detached, thereby forming thermal protection.

it should be understood that although the present description has been described in terms of various embodiments, not every embodiment includes only a single embodiment, and such description is for clarity purposes only, and those skilled in the art will recognize that the embodiments described herein may be combined as suitable to form other embodiments, as will be appreciated by those skilled in the art.

The above description is only illustrative of the present invention and is not intended to limit the scope of the present invention. Any equivalent alterations, modifications and combinations that may be made by those skilled in the art without departing from the spirit and principles of this application shall fall within the scope of this application.

Claims

1. A surge protection device comprising:

a first electrode in electrical contact with the first surface of the varistor;

2. The surge protection device of claim 1 further comprising an insulating layer for electrically insulating the first electrode from the second electrode.

3. The surge protection device of claim 1 wherein the first and/or second electrode is comprised of a patterned electrode layer.

4. The surge protection device of claim 3 wherein a patterned electrode layer comprising the first electrode covers the first surface of the varistor and has an opening exposing the through-hole.

5. The surge protection device of claim 1 wherein the piezoresistors are metal oxide piezoresistors.

6. The surge protection device of claim 1,

The first end of the gas discharge tube is located outside the through-hole;

The surge protection device further has an insulating layer for electrically insulating between the first electrode and the second electrode, and a sum of a thickness of the insulating layer and a thickness of the first electrode is equal to a distance between the first end portion and the first surface.

7. The surge protection device of claim 2 or 6 wherein the insulating layer at least partially covers the first electrode, the second electrode being located on a side of the insulating layer remote from the first electrode.

8. The surge protection device of claim 1 wherein the second end is flush with the second surface.

9. The surge protection device of claim 1 wherein the common electrode is layered and covers both the second surface and the second end.

10. The surge protection device of claim 1 wherein the first surface has a first metallization thereon, the first electrode being in electrical contact with the first metallization;

And/or