Patent Application
20240332914
A spark gap typically includes an arrangement of two conducting electrodes separated by a gap. The gap is usually filled with a gas such as air, designed to allow an electric spark to pass between the conducting electrodes. When the potential difference between the conducting electrodes exceeds the breakdown voltage of the gas within the gap, a spark forms, ionizing the gas and drastically reducing its electrical resistance. An electric current then flows until the path of ionized gas is broken (e.g., due to erosion of the conducting electrodes or widening of the gap) or the potential difference is reduced below the breakdown voltage. This usually happens when the voltage drops, but in some cases occurs when the heated gas rises, stretching out and then breaking the filament of ionized gas. Usually, the action of ionizing the gas is violent and disruptive, often leading to sound (e.g., ranging from a snap for a spark plug to thunder for a lightning discharge), light, and heat. Spark gaps were used historically in early electrical equipment, such as spark gap radio transmitters, electrostatic machines, and X-ray machines. Their most widespread use today is in spark plugs to ignite the fuel in internal combustion engines, but they are also used in lightning arresters, gas discharge tubes and other devices to protect electrical equipment from high-voltage transients.
In spark gaps used to protect electrical circuits from electrical surges, such as circuits on printed circuit boards, an input on the circuit board is typically connected via a first trace to a spark gap and via a second trace to a capacitor, where an opposite end of the capacitor is connected to an output that may in turn be connected to an electrical circuit. The capacitor may be configured to block direct current (DC) and/or to prevent surges from reaching the output and any electrical components connected thereto. The spark gap may include a first terminal connected to the input and a second terminal connected to ground, with an air gap between the first terminal and the second terminal. The terminals may be formed as metallic traces on the printed circuit board. The spark gap may allow a voltage surge to cause a spark that jumps across the gap between the terminals to be shunted to the ground to protect the capacitor and any electrical circuit connected to the output. However, in such a spark gap, if the surge that causes the spark to jump across the gap (known as the spark over voltage or dielectric breakdown voltage) is too large, then the capacitor and/or any components or electrical circuits connected to the output may be damaged.
It may be desirable to provide a spark gap for a printed circuit board that has a lower spark over voltage to better protect the capacitor and any circuit connected to the output. Additionally, these spark gaps may be deployed in high voltage/broadband RF circuits such as CATV line splitters and other products. In this case the Spark Over voltage would have to be controlled to have a low limit ensuring adequate isolation for the line voltage, e.g., 90 Vrms.
A spark gap device is configured to provide an enhanced spark over voltage. The spark gap device includes a printed circuit board, an input configured on the printed circuit board and configured to receive signals, a non-smooth textured substrate surface configured to be disposed on a surface of the printed circuit board, a spark gap configured on the printed circuit board, the spark gap comprising: a first conducting electrode connected to the input, a second conducting electrode configured to be grounded, a gap having an exposed surface of the substrate configured to be disposed between the first and second conducting electrodes, and a conductive material configured to be disposed in a non-continuous and irregular manner on the non-smooth textured substrate surface and between the first and second conducting electrodes, an output configured on the printed circuit board, a capacitor configured to connect between the input and the output, a conductive material configured in a non-continuous and irregular manner on the non-smooth textured substrate surface and between the first and second conducting electrodes, and wherein the spark gap is structurally configured to provide an enhanced spark over voltage to the spark gap device to protect the capacitor and/or an external device connected to the output.
A spark gap device is configured to provide an enhanced spark over voltage so as to protect an electronic device connected to the spark gap device. The spark gap device includes a printed circuit board, a non-smooth textured substrate surface configured to be disposed on a surface of the printed circuit board, a spark gap configured on the printed circuit board, the spark gap comprising: a first conducting electrode, a second conducting electrode, a gap having an exposed surface of the substrate configured to be disposed between the first and second conducting electrodes, and a conductive material configured to be disposed in a non-continuous and irregular manner on the non-smooth textured substrate surface and between the first and second conducting electrodes, and wherein the spark gap is structurally configured to provide an enhanced spark over voltage to the spark gap device to protect an external device connected to the spark gap device.
A spark gap is structurally configured to provide an enhanced spark over voltage. The spark gap includes a non-smooth textured substrate surface, a first conducting electrode, a second conducting electrode, a gap configured to be disposed between the first and second conducting electrodes, and a conductive material configured to be disposed in a non-continuous and irregular manner on the non-smooth textured substrate surface and in the gap between the first and second conducting electrodes, wherein the spark gap is structurally configured to provide an enhanced spark over voltage to protect any device connected to the spark gap.
It will be appreciated that this summary is intended merely to introduce some aspects of the present methods, systems, and media, which are more fully described and/or claimed below. Accordingly, this summary is not intended to be limiting.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present teachings and together with the description, serve to explain the principles of the present teachings.
A spark gap device for a printed circuit board and other applications is described herein. In one embodiment, the spark gap may be used to protect a capacitor and/or circuits connected to the output, such as cable television (CATV) circuits or other elements, multimedia over coax alliance (MoCA) circuits, Ethernet circuits or a combination thereof. However, as will be appreciated, the spark gap for a printed circuit board may be used to protect other types of circuits as well. The spark gap(s) in the circuit may be constructed of specific materials and to specific dimensions as described herein such that they can effectively enhance performance of the spark gap device, as further described herein.
The spark gap device 100 may also include an input 104 that is connected to the circuit board 102. The input 104 may be configured to be connected to a cable or a device. In some embodiments, the input 104 may be configured to be connected to a CATV headend, although any other types of signals may be used. In some embodiments, the input 104 may be configured to receive CATV signals (e.g., from the CATV headend).
The spark gap device 100 may also include a spark gap 103 that is connected to the circuit board 102 and to the input 104. The spark gap 103 may be configured to prevent electrical surges from passing from the input 104 to an output 116, or vice versa. The spark gap 103 may include a first electrode 108 and a second electrode 110 separated by a gap 105. The electrodes 108, 110 may be made from a conductive material such as metal. The electrodes 108, 110 may extend in a direction that is substantially perpendicular to the circuit board 102. The electrodes 108, 110 may be formed at an end of traces 106 formed on the circuit board 102. The gap 105 may consist of the exposed surface of the substrate upon which the electrodes (terminals) are bonded. The substrate may have a material such as FR4 (a glass-reinforced epoxy resin laminate used on printed circuit boards), a ceramic material or another similar material on an outer surface thereof. In some embodiments, the material on the substrate may be any material with a non-smooth textured surface.
A ground 112 may be connected to terminal 110. A capacitor 114 may be connected to the input 104. The output 116 may be connected to the opposite end of the capacitor 114 from the input 104. The output 116 may be connected to other circuits, which in some embodiments may be formed on the printed circuit board 102. Alternatively, the other circuits that the output is connected to may not be on the circuit board 102.
The spark gap device 200 is configured to protect circuits from transient voltages and surges while protecting 1) The capacitor 114 and any output circuit (Upper Limit e.g., 2 KV) connected to the output 116 as well as 2) The system operating voltages at the input from shorting to ground e.g., 90 Vrms Line Passives/Amps or 48 Vdc Power over ethernet, etc. (Lower Limit e.g., 500V).
The conductive particles of the conductive material 214 may be formed from various conductive materials. For example, in some embodiments, the conductive material 214 may be graphite, although other conductive materials may be used, such as aluminum, zinc, etc. The particles of the conductive material 214 may be applied to the non-smooth textured surface 211 in various ways, such as spray coating. In some embodiments where the conductive particles of the conductive material are graphite, the graphite particles may be applied by rubbing a pencil, such as a #2 pencil over the non-smooth textured surface 211. In some embodiments, the conductive particles may be graphite particles applied from pencil grade graphite of 4B to 4H grade (nominal).
In some embodiments, the conductive material 214 may be applied to the non-smooth textured surface 211 between the electrodes 208, 210 with light to moderate surface pressure and back-and-forth strokes. In some embodiments, the non-smooth textured surface 214 may be an undoped FR4 surface (with gaps between graphite partials). The graphite particle coverage must not have undoped regions ≥4 mil wide and a length greater than the length of the conductors. Excess graphite powder may be removed with cloth or swab.
The irregularly disposed particles of the conductive material 214 in the gap 205 are used in various embodiments to enhance the performance of the spark gap device 200. In various embodiments, the spark gap device 200 provides an enhanced spark over voltage, as well as other enhanced performance, as further discussed herein.
Various objectives and benefits achieved by the spark gap device 200 include:
The spark gap devices were tested IAW the following:
Spark gap devices without doping of the conductive material with 0.005″ gaps resulted in a very high spark over (breakdown) voltage range with undesirably high spark over voltages of 2500V+/−1000V with circuits with 2 KV or lower rated blocking capacitors failing surge testing. In contrast, spark gap devices with doping of the conductive material with 0.020″ to 0.025″ gaps resulted in spark over voltages of 1000V+/−500V such that circuits with 2 KV rated blocking capacitors are protected during surge testing using 6 KV/500 Amp testing with 96 spark overs. Additionally, high voltage or 90 Vrms have adequate isolation from ground.
Table 1 illustrates measured breakdown voltage for doped and undoped spark gaps with various gap widths. The high breakdown voltages of the undoped spark gaps result in damage to the capacitor and/or any circuits connected to the output.
The following shows dielectric breakdown for parallel plate conductors of a spark gap 900 with conductors 902 and 904 and dielectric 906 as illustrated in
Observations from Vb equations and the Spark Gap data in table 1:
Observations for capacitance calculations:
The spark gaps doped with graphite have a greater effect on the reduction of the dielectric breakdown voltage than the increase in shunt capacitance (|C|<<|Vb|). Thus, doped spark gaps more effectively protect the circuit from transient voltages (surges) without degrading the broadband RF performance. The reduced dielectric strength Eds of the spark gaps doped with graphite provides a more reliable dielectric breakdown voltage Vb in the presence of excess soldering flux or contaminates. The adhesion of the graphite while exposed to brushing with solvents is very robust and continues to ensure circuit protection (image 3). Graphite may be applied to the printed circuit substrate very easily with minimal manufacturing controls e.g. there is a broad range of graphite doping from minimal to high moderate for which all improve circuit protection while minimizing impact on broadband performance.
In a particular design configuration, the spark gap 1000 may be used on an FR4 substrate with copper clad conductors 1002, 1004 with conductive plating of Either; HASL, LFHASL, ENIG, IAg, ISn, or ENEPIG. The dimensions of the spark gap 1000 may be as set forth in the following table 3 and produce breakdown voltage and surge withstand as noted herein.
In a particular design configuration, the spark gap 1100 may be used on an FR4 substrate with copper clad conductors 1002, 1004 with conductive plating of Either; HASL, LFHASL, ENIG, IAg, ISn, or ENEPIG. The dimensions of the spark gap 1100 may be as set forth in the following table 4 and produce breakdown voltage and surge withstand as noted herein.
The spark gap 1310 has conductors 1312 separated by gap 1313, which may have the irregularly disposed conductive material in the gap. The conductors 1312 may have conductive wire 1316, 1318 attached thereto via through holes formed in the conductors 1312 to increase the effective mass of each conductor so that the spark gap can provide the surge withstand capacity of 96 events for higher surges.
In some embodiments, the spark gaps may be used with high voltage devices such as 90 VAC line taps. In this instance, the width of the spark gap may be increased to about 32.5 mils to increase the lower limit of the spark over voltage to above 200 volts.
It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to embodiments containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.” In addition, where features or aspects of the disclosure are described in terms of Markush groups, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subgroup of members of the Markush group.
This application claims the benefit of U.S. Provisional Patent Application No. 63/456,408, filed Mar. 31, 2023, the contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63456408 | Mar 2023 | US |
