A lightning protection circuit and a lightning protection device

Abstract

The present invention provides a lightning protection circuit, which includes an isolation end module and a local end module, and the isolation end module and the local end module are isolated from each other; the isolation end module includes an isolation end functional circuit and an isolation end signal interface connected to the isolation end functional circuit, the local end module includes a local end functional circuit and a local end signal interface connected to the local end functional circuit, and the isolation end functional circuit and the local end functional circuit transmit signals through an isolation signal transmission link; the isolation end module includes a first discharge guide rail connected to the isolation end signal interface, the local end module includes a second discharge guide rail connected to the local end signal interface, and a first insulation gap is provided between the first discharge guide rail and the second discharge guide rail. The present invention also provides a lightning protection device including the above lightning protection circuit. The above lightning protection circuit and device have good lightning protection effect and long service life.

Description

Technical Field

[0001] The present invention relates to the field of lightning protection, and particularly to a lightning protection circuit and a lightning protection device. Background Art

[0002] Lightning is a violent discharge process that generates impact pulses of high voltage and strong current and is an electromagnetic wave. When lightning occurs, the air electromagnetic field changes violently, causing a certain induced voltage to be induced on metal conductors. Due to the steep pulse edge of the lightning wave triggering secondary or multiple strong electromagnetic inductions, even if there is a building lightning rod, due to the electrostatic electric field induction, electromagnetic induction, resistance, inductance of the grounding wire, and secondary electromagnetic induction of the ground wire current in space, an impact voltage will still be formed on a long metal cable.

[0003] Lightning strikes and current are also a kind of interference signal to lines and equipment. When the voltage and current change and are transmitted through wires, there are two forms, called "common mode" and "differential mode". The power supply lines of equipment, communication lines such as telephones, and communication lines that exchange with other equipment or peripheral equipment have at least two wires, and these two wires are used as round-trip lines to transmit power or signals. But usually there is a third conductor outside these two wires, which is the "ground wire". The interference voltage and current are divided into two types: one is that the two wires are used as round-trip lines to transmit respectively; the other is that the two wires are used as the outgoing paths and the ground wire is used as the return path to transmit. The former is called "differential mode", and the latter is called "common mode".

[0004] The voltage generated simultaneously at both ends of the two wires by the lightning strike current is called "common mode voltage"; and the voltage difference generated simultaneously at both ends of the two single wires due to the imbalance of the line is called "differential mode voltage".

[0005] At the port of the equipment, the "common mode voltage" will impact the port. When the impact voltage is higher than the equipment withstand voltage, the lightning strike voltage enters the equipment from the port of the electrical equipment or communication equipment, and the instantaneous impact current causes fatal overcurrent damage or even burns the equipment.

[0006] The existing lightning protection devices are mainly based on the current "discharge type" lightning protection technology, using non-linear elements to limit the voltage difference between lines or guiding the impact current formed by the voltage at the port to the ground through the ground wire. However, when the grounding circuit for guiding the current into the ground fails to reach an ideal state, the large current to the ground will inevitably cause the ground potential to rise. Once the ground potential is higher than the port withstand voltage of the electronic device, the device will be broken down, resulting in damage or failure of the device function. At the same time, even if the current can be ideally guided and the voltage at the equipment port is limited to be lower than the equipment withstand voltage, since the transient current at the equipment port will also generate a strong induced magnetic field, a secondary induced lightning will occur inside the equipment. When the impact voltage of the induced lightning exceeds the port withstand voltage of the internal components of the equipment, it will also cause lightning damage to the inside of the equipment.

[0007] Chinese Patent CN201910985071.4 discloses a method for lightning protection using an isolation transformer, which blocks the electrical path from the outside to the inside of the power distribution cabinet through the isolation transformer and transmits power through the coil coupling of the transformer.

[0008] However, the isolation transformer also has a breakdown voltage. When the impulse voltage generated by lightning is too large, the withstand voltage between the coils of the isolation transformer without special treatment is not high, and the isolation transformer can still be broken down, causing lightning damage to the isolation transformer and other components. Therefore, the lightning protection method in the prior art still has defects in the protection ability against ultra-high impulse voltage. Summary of the Invention

[0009] To solve the above problems, the present invention provides a lightning protection circuit capable of coping with ultra-high impulse voltage.

[0010] A lightning protection circuit includes an isolation end module and a local end module, and the isolation end module and the local end module are isolated from each other;

[0011] The isolation end module includes an isolation end functional circuit and an isolation end signal interface connected to the isolation end functional circuit, the local end module includes a local end functional circuit and a local end signal interface connected to the local end functional circuit, and the isolation end functional circuit and the local end functional circuit transmit signals through an isolation signal transmission link;

[0012] The isolation end module includes a first discharge rail connected to the isolation end signal interface, the local end module includes a second discharge rail connected to the local end signal interface, and a first insulation gap is provided between the first discharge rail and the second discharge rail.

[0013] In one embodiment, the isolation end signal interface is connected to an external ground wire using a millimeter-level air gap or a high-voltage-resistant ceramic discharge tube.

[0014] In one embodiment, the lightning protection circuit further includes an isolation transformer, and the isolation transformer is connected to the isolation end functional circuit and the local end functional circuit. The isolation transformer is used to transmit electrical energy between the isolation end functional circuit and the local end functional circuit through a coupling coil, and the coupling coil is wrapped with a high-voltage-resistant insulating winding.

[0015] In one embodiment, the isolation signal transmission link is at least one of an optical communication transmission link, an isolation transformer, a balanced capacitor transmission link, and a wireless channel transmission link.

[0016] In one embodiment, the first discharge guide rail surrounds or semi - surrounds the isolation - end functional circuit, the second discharge guide rail surrounds or semi - surrounds the local - end functional circuit, the first discharge guide rail and the second discharge guide rail are provided with opposite rail segments, and there is a first insulation gap between the rail segments.

[0017] In one embodiment, the opposite rail segments of the first discharge guide rail and the second discharge guide rail are arranged in parallel, and the first discharge guide rail and the second discharge guide rail are provided with opposite current - conducting protrusions on the rail segments.

[0018] In one embodiment, the first insulation gap is an air gap.

[0019] In one embodiment, a second insulation gap is further provided between the first discharge guide rail and the isolation - end functional circuit, and between the second discharge guide rail and the local - end functional circuit.

[0020] In one embodiment, a common - mode suppression circuit and / or a differential - mode suppression circuit are connected in series between the isolation - end functional circuit and the isolation - end signal interface and / or between the local - end functional circuit and the local - end signal interface.

[0021] In one embodiment, a common - mode suppression circuit and / or a differential - mode suppression circuit are connected in series between the isolation - end functional circuit and the isolation signal transmission link and / or between the local - end functional circuit and the isolation signal transmission link.

[0022] In one embodiment, when the common - mode suppression circuit and the differential - mode suppression circuit are connected in series at the same time, the common - mode suppression circuit is farther from the isolation - end functional circuit and / or the local - end functional circuit than the differential - mode suppression circuit.

[0023] In one embodiment, the common - mode capacitance of the isolation - end functional circuit is less than 100 pF.

[0024] To solve the above problems, the present invention also provides a lightning - protection device circuit capable of coping with ultra - high impact voltages.

[0025] A lightning - protection device includes the aforementioned lightning - protection circuit, and is characterized in that the lightning - protection device further includes an insulating housing for accommodating the lightning - protection circuit;

[0026] The isolation - end signal interface is used to connect to an external line, and the local - end signal interface is used to connect to a device to be protected.

[0027] After adopting the above lightning protection circuit and lightning protection device, when dealing with ultra-high impact voltages such as lightning, the first insulation gap between the first discharge guide rail and the second discharge guide rail can be preferentially broken down to release a large amount of lightning impact energy, without breaking down the isolation signal transmission link, and causing damage to the isolation end circuit, the local end circuit, and the electronic device to be protected, with better lightning protection effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of a lightning protection circuit in an embodiment of the present invention;

[0029] Figure 2 Schematic diagram of a lightning protection circuit in another embodiment of the present invention;

[0030] Figure 3 Schematic diagram of a lightning protection circuit in another embodiment of the present invention;

[0031] Figure 4 Schematic diagram of a circuit in which the isolation signal transmission link uses an isolation transformer to transmit signals in an embodiment of the present invention;

[0032] Figure 5 Schematic diagram of a circuit in which the isolation signal transmission link uses optical fiber to transmit signals in an embodiment of the present invention;

[0033] Figure 6 Schematic diagram of a circuit in which the isolation signal transmission link uses a wireless channel signal in an embodiment of the present invention;

[0034] Figure 7 Schematic diagram of a circuit in which the isolation signal transmission link uses a balanced capacitor to transmit signals in an embodiment of the present invention;

[0035] Figure 8 Schematic diagram of the shape of the discharge guide rail in an embodiment of the present invention;

[0036] Figure 9 Schematic diagram of the shape of the discharge guide rail in another embodiment of the present invention;

[0037] Figure 10 Schematic diagram of a lightning protection circuit including a common mode suppression circuit, a differential mode suppression circuit, and a power transmission link in an embodiment of the present invention;

[0038] Figure 11 Schematic diagram of a lightning protection circuit including a common mode suppression circuit, a differential mode suppression circuit, and a power transmission link, and capable of being externally connected to a power supply in an embodiment of the present invention;

[0039] Figure 12 Schematic diagram of the lightning protection effect of a lightning protection device based on the lightning protection circuit in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0041] It should be noted that if there are directional indications (such as up, down, left, right, front, back...) involved in the embodiments of the present application, the directional indications are only used to explain the relative position relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0042] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present application, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present application.

[0043] To solve the above technical problems, the present invention provides a lightning protection circuit and a lightning protection device applying the lightning protection circuit. As Figure 1 shown, the lightning protection device 10 includes an insulating housing 12 and a printed circuit board received in the insulating housing. A lightning protection circuit 20 is provided on the printed circuit board. The lightning protection circuit 20 includes an isolation end module 30 and a local end module 40. The isolation end module 30 and the local end module 40 are isolated from each other, that is, the isolation end module 30 and the local end module 40 are in an equivalent non-connected state to the lightning current impact, blocking the propagation of the lightning current between the internal functional circuits of the lightning protection device.

[0044] The lightning current impact is equivalent to a low-frequency high-voltage wave, which can cut into the functional circuit of the lightning protection device from the signal port and affect its function. The core principle of the lightning protection device is to block the lightning strike instant impact circuit conducted from the signal port line, and through a specially designed communication functional circuit or power conversion circuit, transmit the signal or electric energy to the opposite end.

[0045] As Figure 1As shown, the isolation end module 30 includes an isolation end functional circuit 32 and an isolation end signal interface 34 connected to the isolation end functional circuit 32. The local end module 40 includes a local end functional circuit 42 and a local end signal interface 44 connected to the local end functional circuit 42.

[0046] The isolation end signal interface 34 is used to connect to an external line (which can be a signal transmission line or a power transmission line). The local end signal interface 44 is used to connect to the device that needs to be protected, so that the lightning protection device 10 is connected in series between the device that needs lightning protection and the external line. The isolation end functional circuit 32 and the local end functional circuit 42 are the sub-circuit modules that directly or indirectly support the communication function at the isolation end and the local end respectively, such as a power supply circuit, an encoding and decoding circuit, etc., which support the signal transmission function and the sub-circuit modules that support the isolated signal transmission link. The isolation end functional circuit 32 and the local end functional circuit 42 are respectively connected to the isolated signal transmission link 50, and signals are transmitted through the isolated signal transmission link 50.

[0047] As Figure 1 shown, the isolation end module 30 further includes a first discharge rail 36 connected to the isolation end signal interface 34, and the local end module 40 further includes a second discharge rail 46 connected to the local end signal interface 44. There is a first insulation gap 14 between the first discharge rail 36 and the second discharge rail 46. Preferably, the first discharge rail 36 is connected to the ground terminal of the isolation end signal interface; the second discharge rail 46 is connected to the ground terminal of the local end signal interface 44. Preferably, this ground terminal can be connected to the ground of the electronic device that needs to be protected.

[0048] In this embodiment, the first insulation gap 14 is preferably an air gap with low cost, and the air gap is greater than 10 mm. The first discharge rail 36 surrounds or semi-surrounds the isolation end functional circuit 32, and the second discharge rail 46 surrounds or semi-surrounds the local end functional circuit 42. The first discharge rail 36 and the second discharge rail 46 are provided with opposite rail segments, and the air gap between these rail segments is the first insulation gap 14.

[0049] Except for a single-point connection at one terminal of the isolation end circuit other than the isolation end signal interface, the first discharge rail 36 has a third insulation gap 18 with the isolation end functional circuit 32 at other positions. Correspondingly, except for a single-point connection at the local end signal interface 44 of the local end circuit 40, the second discharge rail 46 also has a second insulation gap 18 with the local end functional circuit 42 at other positions.

[0050] The single-point connection means that the discharge rail is only connected to the ground wire of the functional circuit at the signal interface position.

[0051] Preferably, when the second insulation gap is an air gap, the second insulation gap is greater than 1 mm. When directly using a printed circuit board as the second insulation gap, the second insulation gap is at least 2 mm; when the second insulation gap is filled with other insulating materials, it can be proportionally reduced according to the insulation level relative to the air gap.

[0052] That is to say, the isolated end functional circuit 32, the local end functional circuit 42, and the terminals of the isolated signal transmission link surrounded by the first discharge rail 36 and the second discharge rail 46 are respectively kept at a certain isolation distance from the first discharge rail 36 and the second discharge rail 46 through the second insulation gap, which can prevent the impact voltage from further blocking the leakage of the impact current to the circuit modules or electronic components in the functional circuits of the local end and the isolated end when the first insulation gap between the first discharge rail 36 and the second discharge rail 46 is broken down.

[0053] That is, the first discharge rail 36 and the second discharge rail 46 are respectively far away from the functional circuits and metal wires they surround.

[0054] For example, as Figure 1 shown, the first discharge rail 36 and the second discharge rail 46 are both L-shaped layouts on the circuit board, and each semi-surrounds the isolated end functional circuit 32 and the local end functional circuit 42 on the circuit board. One arm of the L-shaped first discharge rail 36 and the second discharge rail 46 is opposite, and the distance between the opposite arms of the first discharge rail 36 and the second discharge rail 46 is the shortest distance between the first discharge rail 36 and the second discharge rail 46. The air gap between the shortest distances is the first insulation gap 14.

[0055] In other embodiments, as Figure 2 and Figure 3 shown, the first discharge rail 36 and the second discharge rail 46 can also be square concave-shaped or bevel irregular-shaped, but both surround or semi-surround the isolated end functional circuit 32 or the local end functional circuit 42, and there are opposite rail segments.

[0056] In this embodiment, the isolated signal transmission link 50 can be at least one of an optical communication transmission link, an isolation transformer, a balanced capacitor transmission link, and a wireless channel transmission link.

[0057] Refer to Figure 4 shown, Figure 4An embodiment using an isolation transformer as an isolation signal transmission link 50 is shown. Specifically, the isolation terminal signal interface 34 includes signal terminals 341 and 342. After accessing the external line, there is a differential mode voltage between the signal terminals 341 and 342, and this differential mode voltage is the intensity of the signal transmitted by the external line. A high-voltage resistant insulating winding is wound around the coil of the isolation transformer 50. When lightning acts on the external line and causes a high-voltage electric field at the isolation terminal signal interface 34, this high-voltage electric field causes a very high common mode voltage of the isolation terminal signal interface 34 with respect to the ground.

[0058] For example, the signal terminal 342 is the signal ground wire. When there is no lightning, the voltage of the signal terminal 342 with respect to the ground is 0, and the voltage at the signal terminal 341 is Vi. The differential mode voltage between 341 and 342 is Vi; when lightning occurs, if lightning acts on the external line and causes an extremely high voltage Vt with respect to the ground at the isolation terminal signal interface 34, the voltage of the signal terminal 342 with respect to the ground becomes Vt, and the voltage at the signal terminal 341 with respect to the ground becomes Vt + Vi, but the differential mode voltage between 341 and 342 is still Vi. Therefore, as Figure 4 shown, ideally, the differential mode voltage between points A and B at both ends of the coil of the isolation transformer 50 is Vt regardless of whether lightning strikes. Through the coupling effect of the coil, it can be obtained that the differential mode voltage between points C and D at both ends of the coil of the isolation transformer is λ×Vi regardless of whether lightning strikes, where λ is the transformation coefficient, that is, the coil turn ratio. Thus, the voltage between the input terminals E and F of the local end functional circuit 42 is also λ×Vi, and the local end functional circuit 42 can transmit the signal with an intensity of λ×Vi to the electronic device to be protected through the local end signal interface 44.

[0059] It can be seen from the above analysis that even if lightning strikes, using an isolation transformer as an isolation signal transmission link can still normally transmit the signal on the external line to the electronic device to be protected without being affected by lightning. However, the premise for this isolation signal transmission link not to be broken down is that the high-voltage resistant insulating winding wound around the coil of the isolation transformer is not broken down. When the device ages and the electrical indicators of the high-voltage resistant insulating winding decline, there will be a risk of breakdown, thus injecting an impact current into the local end signal interface 44 of the local end module 40 and causing harm to the electronic device to be protected. At this time, the isolation protection function of the lightning protection circuit will fail. Similarly, even if the performance indicators of the high-voltage resistant insulating winding on the isolation transformer do not decrease, the lightning strike impact voltage may still be higher than its withstand voltage value. When lightning strikes at this time, the electronic device to be protected will also be damaged.

[0060] However, even if the lightning impulse voltage is higher than the withstand voltage value of the isolation transformer, the common-mode voltage impulse current invading from signal terminals 341 and 342 will preferentially converge at the first discharge rail. This is because a second insulation gap 18 is provided between the first discharge rail 36 and the isolation section functional circuit 32, away from the isolation section functional circuit. Relative to the inside of the functional circuit, the first discharge rail 36 is a pure metal wire with a small impedance to lightning waves and can preferentially converge the lightning impulse current.

[0061] In this embodiment, for the first discharge rail 36, the second discharge rail 46, and the first insulation gap 14 provided therebetween, the lightning current preferentially discharges here to release the lightning energy.

[0062] Same Figure 4 As shown, the first discharge rail 36 is connected to the signal terminal 342 of the isolation end signal interface 34. When lightning occurs, there is also a high voltage Vt relative to the ground on the first discharge rail 36, that is, there is a differential mode voltage Vt between the first discharge rail 36 and the second discharge rail 46. The withstand voltage of the first insulation gap can be set lower than the withstand voltage of the high-voltage insulation winding wound on the coil of the isolation transformer. When the voltage generated by lightning is too high, the first insulation gap between the first discharge rail 36 and the second discharge rail 46 will be preferentially broken down. The first insulation gap is preferably an air gap, which will not cause harm to the surrounding components, and the high-voltage insulation winding wound on the coil of the isolation transformer is thus protected from being broken down; almost all the energy is released when the lightning impulse breaks down the air gap, so that the protected electronic device is also protected.

[0063] Referring again to Figure 5 shown, Figure 5 An embodiment using an optical communication transmission link as the isolation signal transmission link is shown. In this embodiment, the optical communication transmission link includes optocoupler terminals located in the isolation end module 30 and the local end module 40 respectively and an optical fiber as the transmission link. The signal on the external line is sequentially transmitted through the isolation end signal interface 34 to the isolation end functional circuit 32, the optocoupler terminal of the optical communication transmission link in the isolation end module 30, the optical fiber, the optocoupler terminal of the optical communication transmission link in the local end module 40, the local end functional circuit 42, and the local end signal interface 44, and thus finally transmitted to the electronic device to be protected.

[0064] As can be seen from the foregoing analysis, even if the electric field of lightning acts on the external line to generate an ultra-high common-mode voltage at the signal terminals 341 and 342 of the isolation terminal signal interface 34, the differential-mode voltage between the signal terminals 341 and 342 is still the signal strength of the transmitted signal. Therefore, the circuit functions such as signal encoding and decoding of the local-end functional circuit 42 are not affected. At the same time, since the optical communication transmission link uses non-electrically connected and mutually isolated optical signal transmission, such as optical fiber transmission, and since the distance between the first discharge rail and the second discharge rail is the equivalent shortest distance between the local-end module 40 and the isolation-end module 30, this makes the distance between the functional circuits of the local-end and the isolation-end and the optocoupler terminals greater than the distance between the discharge rails of the local-end and the isolation-end. Even if lightning generates an ultra-high impact voltage, it will preferentially break down the first insulation gap between the first discharge rail 36 and the second discharge rail 46, rather than break down the optical communication transmission link between the local-end functional circuit 42 and the isolation-end functional circuit 32 to cause damage to the equipment to be protected due to the formation of a short circuit.

[0065] Refer again to Figure 6 as shown Figure 6 An embodiment is shown in which a wireless channel transmission link is used as the isolation signal transmission module 50. In this embodiment, the wireless channel transmission link includes wireless transmission terminals located at the isolation-end module 30 and the local-end module 40 respectively. The wireless transmission terminals can transmit signals to each other using wifi, Bluetooth, Zigbee, licensed or unlicensed wireless communication channels in the 2.4G frequency band, licensed or unlicensed wireless communication channels in the 5G frequency band, or other wireless communication channels, and are not limited to a specific wireless transmission method.

[0066] The signal on the external line is sequentially transmitted to the isolation-end functional circuit 32, the wireless transmission terminal of the wireless channel transmission link at the isolation-end module 30, the wireless communication channel, the wireless transmission terminal of the wireless channel transmission link at the local-end module 40, the local-end functional circuit 42, and the local-end signal interface 44 through the isolation-end signal interface 34, and thus is finally transmitted to the electronic device to be protected.

[0067] As can be seen from the foregoing analysis, even if the electric field of lightning acts on the external line and generates an ultra-high common-mode voltage at the signal terminals 341 and 342 of the isolation terminal signal interface 34, the differential-mode voltage between the signal terminals 341 and 342 is still the signal strength of the transmitted signal. Therefore, the circuit functions such as signal encoding and decoding of the local-end functional circuit 42 are not affected. At the same time, since the wireless channel transmission link uses non-electrically connected and mutually isolated electromagnetic wave transmission, and the distance between the first discharge guide rail and the second discharge guide rail is the equivalent shortest distance between the local-end module 40 and the isolation-end module 30, this makes the distance between the functional circuits of the local end and the isolation end and the wireless transmission terminals greater than the distance between the discharge guide rails of the local end and the isolation end. Even if lightning generates an ultra-high impact voltage, it will preferentially break down the first insulation gap between the first discharge guide rail 36 and the second discharge guide rail 46, rather than break down the wireless channel transmission link between the local-end functional circuit 42 and the isolation-end functional circuit 32 and cause damage to the equipment that needs to be protected due to the same path.

[0068] Refer again to Figure 7 as shown, Figure 7 An embodiment of using a balanced capacitor transmission link as the isolation signal transmission module 50 is shown. In this embodiment, the balanced capacitor transmission link itself is in a non-connected state and is in an isolated state for the common-mode voltage. High-frequency signals are transmitted between the local-end functional circuit 42 and the isolation-end functional circuit 32, and the transmission characteristics of the capacitor, which passes high-frequency signals and blocks low-frequency signals, are used to suppress the lightning wave impact current with low-frequency characteristics.

[0069] It should be noted that the isolation signal transmission link 50 between the isolation-end functional circuit 32 and the local-end functional circuit 42 is not limited to a specific signal transmission form, as long as it is isolated transmission. Preferably, the common-mode capacitance of the isolation-end functional circuit 32 is less than 100 pF. As mentioned above, the instantaneous common-mode voltage will charge the isolation-end functional circuit 32. If the common-mode capacitance of the isolation-end functional circuit 32 is too large, a large common-mode voltage charging current will be generated, which will cause harm to the equipment. Setting it to less than 100 pF can effectively reduce the common-mode voltage charging current, thereby protecting the isolation-end functional circuit 32 from being damaged due to excessive common-mode voltage charging current.

[0070] In addition, the first insulation gap is preferably an air gap, and the air gap is greater than 10 mm. The upper limit of the distance depends on the withstand voltage performance between the isolation terminal functional circuit 32 and the local terminal functional circuit 42. When a coupling circuit transmission module is used as the isolation signal transmission module, the gap withstand voltage performance is required to be lower than the withstand voltage of the high-voltage insulation winding of the coupling circuit. Using a space gap, first, the cost is low and the circuit structure is simple; second, when adjusting the size of the space gap according to the required breakdown voltage, the adjustment is convenient, and only the distance between the local terminal module 40 and the isolation terminal module 30 needs to be controlled; third, it has an infinite breakdown life.

[0071] In this embodiment, further, the opposite rail segments of the first discharge rail 36 and the second discharge rail 46 are arranged substantially parallel, and the first discharge rail 36 and the second discharge rail 46 are provided with opposite current-conducting protrusions on the parallel rail segments.

[0072] Reference Figure 8 As shown, one arm of the L-shaped first discharge rail 36 faces one arm of the L-shaped second discharge rail 46, and one arm of the first discharge rail 36 is parallel to one arm of the second discharge rail 46. A small first current-conducting protrusion 361 extending toward the second discharge rail 46 is provided at the intersection of the two arms of the L-shaped first discharge rail 36. Similarly, a small second current-conducting protrusion 461 extending toward the first discharge rail 36 is provided at the intersection of the two arms of the L-shaped second discharge rail 46. The functions of the first current-conducting protrusion 361 and the second current-conducting protrusion 461 are to conduct electricity when the first insulation gap is broken down, so that the position of the electric spark or arc during breakdown can be controlled, and a small amount of heat energy generated will not harm the local terminal circuit 40 and the isolation terminal circuit 30.

[0073] In another embodiment, the opposite rail segments of the first discharge rail 36 and the second discharge rail 46 can be arranged obliquely.

[0074] Reference Figure 9 As shown, one arm of the L-shaped first discharge rail 36 faces one arm of the L-shaped second discharge rail 46, and one arm of the first discharge rail 36 is inclined relative to one arm of the second discharge rail 46. The inclination causes the intersection of the two arms of the L-shaped first discharge rail 36 and the intersection of the two arms of the L-shaped second discharge rail 46 to form a current-conducting tip, which can conduct electricity when the first insulation gap is broken down, so that the position of the electric spark or arc during breakdown can be controlled, and a small amount of heat energy generated will not harm the local terminal circuit 40 and the isolation terminal circuit 30.

[0075] Preferably, as Figure 1As shown, the isolation end module 30 is also provided with a ground connection 31. A virtual ground connection is adopted between the ground connection 31 and the first discharge guide rail 36. There are two schemes for the virtual ground connection. One is to use an insulating gap 16 of millimeter level, and the other is to connect a high-voltage-resistant ceramic discharge tube in series between the isolation end signal interface and the ground wire. The virtual ground connection is a recommended scheme and has low requirements for the ground resistance. When a lightning voltage impulse occurs at the port, the virtual ground connection can limit the port voltage to ensure that the first isolation gap is not broken down.

[0076] When using an insulating gap for virtual ground connection, the breakdown voltage of an insulating gap of several millimeters is between several thousand volts and more than 10 thousand volts, which can ensure that the first insulating gap 14 is never broken down. When the ground connection is not ideal, through the virtual ground connection, the insulating gap 16 is first broken down. Even considering the effect of the ground resistance on raising the ground potential, the superimposed input port voltage is difficult to exceed the breakdown voltage of the first insulating gap 14. Even after the virtual ground connection is broken down and the port voltage exceeds the breakdown voltage of the first insulating gap 14, the lightning protection device fails, but most of the remaining energy is released when the first insulating gap 14 is broken down by the lightning current. Therefore, when there is a virtual ground connection, first limit the voltage and divert the current through the virtual ground connection, and then release the energy when the first insulating gap 14 is broken down, which can well protect the functional circuit from being broken down. Unless in extreme cases where the lightning strike is extremely strong, after breaking down the virtual ground connection 16 and the first insulating gap 14, the remaining port voltage is still higher than the port withstand voltage of the functional circuit, which will damage the lightning protection device functional circuit and cause irreversible damage. This situation is extremely special and rare.

[0077] Similarly, when using a high-voltage-resistant discharge tube, the discharge tube does not work in the normal state. When a lightning strike occurs, the discharge tube conducts, and the lightning current will achieve current diversion through the discharge conduit, which will also first play a role in limiting the port voltage to ensure that the first insulating gap 14 is not broken down.

[0078] In this embodiment, as Figure 10 shown, the lightning protection circuit 20 further includes an isolation transformer 60. The isolation transformer 60 is connected to the isolation end functional circuit 32 and the local end functional circuit 42. The isolation transformer 60 is used to transmit electric energy between the isolation end functional circuit 32 and the local end functional circuit 42 through a coupling coil. The coupling coil is wrapped with a high-voltage-resistant insulating winding, and the breakdown voltage of the high-voltage-resistant insulating winding wrapped on the coupling coil of the isolation transformer 60 is higher than the breakdown voltage of the first insulating gap 14.

[0079] In this embodiment, referring to Figure 10 shown, the isolation transformer 60 is connected to the isolation end functional circuit 32 and the local end functional circuit 44. The isolation end functional circuit 32 and the local end functional circuit 44 can obtain power from an external line or the signal port of the electronic device to be protected and transmit electric energy to the other functional circuit, so that the functional circuit at the other end can also supply electric energy to the isolation signal transmission link.

[0080] In another embodiment, as Figure 11 shown, the isolation terminal circuit 30 and the local terminal module 40 can each be provided with an isolation terminal power interface 38 and a local terminal power interface 48, and either the isolation terminal power interface 38 or the local terminal power interface 48 can be externally connected to an independent power supply. When the isolation terminal power interface 38 is externally connected to an independent power supply, the electrical energy of the isolation terminal power interface 38 supplies power to the isolation terminal functional circuit 32. At the same time, the isolation terminal functional circuit 32 also transmits electrical energy to the local terminal functional circuit 42 through the isolation transformer 60 for power supply.

[0081] Preferably, in order to prevent damage caused by the high-speed jump of the common-mode impact voltage generated by lightning at the isolation terminal signal interface 34, a common-mode suppression circuit and / or a differential-mode suppression circuit are connected in series between the isolation terminal functional circuit 32 and the isolation terminal signal interface 34 and / or between the local terminal functional circuit 42 and the local terminal signal interface 44.

[0082] As Figure 10 and 11 shown, in one embodiment, a common-mode suppression circuit 321 and a differential-mode suppression circuit 322 are connected in series between the signal terminals 341 and 342 of the isolation terminal functional circuit 32 and the isolation terminal signal interface 34, and a common-mode suppression circuit 421 and a differential-mode suppression circuit 422 are connected in series between the signal terminals 441 and 442 of the local terminal functional circuit 42 and the local terminal signal interface 44. The common-mode suppression circuit can be based on an inductive element, and the differential-mode suppression circuit can be a voltage-limiting element, such as a high-voltage-resistant varistor or a ceramic discharge tube, etc.

[0083] After lightning acts on the external line, an instantaneous high voltage Vt is generated on the signal terminals 341 and 342 of the isolation terminal signal interface 34, and a common-mode voltage for instantaneously charging the isolation terminal functional circuit 32 is generated. After connecting the common-mode suppression circuit 321 (a circuit based on an inductive element) in series, the intensity of the instantaneous charging current can be greatly reduced, thereby preventing damage to the internal components of the isolation terminal functional circuit 32 when the instantaneous charging current is too large.

[0084] The function of setting the differential-mode suppression circuit is that when the lengths of the lines between the signal terminals 341 and 342 of the isolation terminal functional circuit 32 and the isolation terminal signal interface 34 are different or aging occurs, the attenuation of the common-mode voltage on the signal terminals 341 and 342 is inconsistent when transmitted to the isolation terminal functional circuit 32, resulting in a possible differential-mode overvoltage between the terminals. When the common-mode voltage generated by lightning is an ultra-high voltage, even a slight attenuation difference still generates a relatively high differential-mode voltage, and an impact current is generated in the internal loop of each terminal, which is likely to damage the components in the isolation terminal functional circuit 32. After setting the differential-mode suppression circuit, the possible relatively high differential-mode voltage is clamped and eliminated in advance, thereby limiting the intensity of the impact current and playing a protective role.

[0085] Preferably, referring to Figure 10 and 11 As shown, a common-mode rejection circuit and / or a differential-mode rejection circuit are connected in series between the isolation terminal function circuit 32 and the isolation signal transmission link 50 and / or between the local terminal function circuit 42 and the isolation signal transmission link 50. For the same reason as described above, connecting a common-mode rejection circuit and / or a differential-mode rejection circuit in series between the local terminal and / or the isolation terminal and each interface can effectively prevent the common-mode voltage that may be generated on each interface terminal, thereby protecting the function circuit.

[0086] Furthermore, when both a common-mode rejection circuit and a differential-mode rejection circuit are connected in series, the common-mode rejection circuit is farther from the isolation terminal function circuit and / or the local terminal function circuit than the differential-mode rejection circuit. That is to say, referring to Figure 10 and 11 As shown, the common-mode rejection circuit is closer to the interface and terminal where lightning high voltage is likely to be generated, and the differential-mode rejection circuit is closer to the function circuit. This is because the differential-mode voltage that the differential-mode rejection circuit needs to suppress is generated due to the imbalance of the common-mode voltage in the line. Therefore, first attenuate the common-mode voltage generated by lightning through the common-mode rejection circuit, and then suppress the differential-mode voltage generated by the residual common-mode voltage when the line is unbalanced by the differential-mode rejection circuit, which can improve the reliability of the system.

[0087] Specifically, taking the lightning protection of a network surveillance camera as an example, as Figure 12 shown, the network surveillance camera is an electronic device that needs to be protected and is connected to a communication network through a long network cable, and the long network cable is the external line of the network surveillance camera. In this application scenario, the lightning protection device 10 can be connected in series on the long network cable of the network surveillance camera.

[0088] The lightning protection device 10 has a box-shaped insulating housing 12. On one end of two opposite end faces at the far end, an isolation terminal signal interface 34 and an isolation terminal power interface 38 are provided, and on the other end, a local terminal signal interface 44 and a local terminal power interface 48 are provided. In other embodiments, the insulating housing 12 can also be a cylindrical insulating housing or an insulating housing with other shapes, but preferably there are two end faces far away from each other, and the signal interfaces or power interfaces of the local terminal and the isolation terminal are preferably set at the farthest distance.

[0089] The network monitoring camera is connected to the local end signal interface 44 of the lightning protection device 10 through a short network cable, and the long network cable of the external line is connected to the isolation end signal interface 34 of the lightning protection device 10, thus realizing series connection. Preferably, a power line can be led out from the power supply of the network monitoring camera and connected to the local end power supply interface 48 of the local end signal interface to supply power to the lightning protection device 10. As mentioned above, after receiving the electric energy from the local end power supply interface 48, the local end functional circuit 42 can also transmit the electric energy to the isolation end functional circuit 32 through the isolation transformer 60, so as to support the operation of the entire lightning protection device 10.

[0090] When the electrostatic field of lightning acts on the long network cable and generates a high-voltage common-mode voltage at the isolation end signal interface 34, since the local end circuit 40 and the isolation end circuit 30 are in an isolated state and can only transmit the differential-mode signal between the isolation end signal interfaces 34, the lightning protection device 10 can still normally transmit the communication signal on the long network cable. When the common-mode voltage generated by lightning is too large, it first breaks down the insulation gap 16 and is guided into the grounding 31 of the isolation end circuit for drainage. Even if the insulation gap 16 and the grounding 31 age and cause a change in the withstand voltage parameter, when the common-mode voltage generated by lightning is too large, it still first breaks down the first insulation gap and will not break down the isolation signal transmission link 50 and the isolation transformer 60, and most of the energy is released during the breakdown of the first insulation gap, thus reducing the harm to the network monitoring camera.

[0091] In one embodiment, the parameter indicators of this lightning protection device can be set as follows: The first insulation gap uses an air gap with a width set to 30 mm; the isolation signal transmission link can adopt various communication interfaces such as RS232 / 485, coaxial cable, optical fiber, wireless, RJ45, etc.

[0092] Under these parameters, the non-breakdown voltage between the first discharge rail and the second discharge rail can be guaranteed to be greater than 30 kV, the breakdown withstand voltage can be greater than 50 kV, the breakdown withstand current can be greater than 5 kA, and the impact resistance rate of the isolation front-end system can be greater than 40 kV / 1uS. Isolated transmission DC / AC voltage: 3 - 48 VDC, customizable; Isolated transmission power supply power: The maximum of the small transformer > 80 W, high power can be customized. When this lightning protection device breaks down, only the air gap between the first discharge rail and the second discharge rail breaks down. After the breakdown releases the lightning energy, the device can self-recover.

[0093] When the isolated terminal signal interface adopts a virtual ground connection, an insulating gap of several millimeters or a high-voltage-resistant ceramic discharge tube can reduce the input voltage below 10 kV. Inside, a first air insulation gap greater than 10 mm is used, with a breakdown voltage greater than 10 kV, and the internal isolated signal transmission link has a high voltage resistance greater than dozens of kV. During a lightning strike, the instantaneous voltage at the signal port will be suppressed through the virtual ground and be less than the internal isolation breakdown voltage of the lightning arrester. Even if the instantaneous voltage diversion is not timely, the first air insulation gap will be preferentially broken down, and it will not damage the internal functional circuit of the lightning arrester, but only cause a temporary failure.

[0094] Therefore, when the virtual ground is used in good cooperation, this lightning arrester will have nearly ultra-high lightning protection performance indicators.

[0095] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other.

[0096] The above are only the embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. A lightning protection circuit, characterized in that, It includes an isolated end module and a local end module, and the isolated end module and the local end module are isolated from each other; The isolated end module includes an isolated end functional circuit and an isolated end signal interface connected to the isolated end functional circuit, the local end module includes a local end functional circuit and a local end signal interface connected to the local end functional circuit, and the isolated end functional circuit and the local end functional circuit transmit signals through an isolated signal transmission link; The isolated end module includes a first discharge rail connected to the isolated end signal interface, the local end module includes a second discharge rail connected to the local end signal interface, and a first insulation gap is provided between the first discharge rail and the second discharge rail.

2. The lightning protection circuit according to claim 1, characterized in that, The isolated end signal interface is connected to an external ground wire by a millimeter-level air gap or a high-voltage-resistant ceramic discharge tube.

3. The lightning protection circuit according to claim 1, characterized in that, The lightning protection circuit further includes an isolation transformer, the isolation transformer is connected to the isolated end functional circuit and the local end functional circuit, and the isolation transformer is used to transmit electrical energy between the isolated end functional circuit and the local end functional circuit through a coupling coil, and the coupling coil is wrapped with a high-voltage-resistant insulating winding.

4. The lightning protection circuit according to claim 1, characterized in that, The isolated signal transmission link is at least one of an optical communication transmission link, an isolation transformer, a balanced capacitor transmission link, and a wireless channel transmission link.

5. The lightning protection circuit according to claim 1, characterized in that, The first discharge rail surrounds or semi-surrounds the isolated end functional circuit, the second discharge rail surrounds or semi-surrounds the local end functional circuit, the first discharge rail and the second discharge rail have opposite rail segments, and the first insulation gap is between the rail segments.

6. The lightning protection circuit according to claim 5, characterized in that, The opposite rail segments of the first discharge rail and the second discharge rail are arranged in parallel, and the first discharge rail and the second discharge rail are provided with opposite current-carrying protrusions on the rail segments.

7. The lightning protection circuit according to claim 1, characterized in that, The first insulation gap is an air gap.

8. The lightning protection circuit according to claim 1, characterized in that, A second insulation gap is further provided between the first discharge rail and the isolated end functional circuit, and between the second discharge rail and the local end functional circuit.

9. The lightning protection circuit according to claim 1, characterized in that, A common-mode suppression circuit and / or a differential-mode suppression circuit is / are connected in series between the isolated end functional circuit and the isolated end signal interface and / or between the local end functional circuit and the local end signal interface.

10. The lightning protection circuit according to claim 1, characterized in that, A common-mode suppression circuit and / or a differential-mode suppression circuit is / are connected in series between the isolated end functional circuit and the isolated signal transmission link and / or between the local end functional circuit and the isolated signal transmission link.

11. The lightning protection circuit according to claim 9 or 10, characterized in that, When the common-mode suppression circuit and the differential-mode suppression circuit are connected in series at the same time, the common-mode suppression circuit is farther from the isolated end functional circuit and / or the local end functional circuit than the differential-mode suppression circuit.

12. The lightning protection circuit according to claim 1, characterized in that, The common-mode capacitance of the isolated end functional circuit is less than 100 pF.

13. A lightning protection device, comprising the lightning protection circuit according to any one of claims 1 to 12, characterized in that, The lightning protection device further includes an insulating housing for accommodating the lightning protection circuit; The isolated end signal interface is used to connect an external line, and the local end signal interface is used to connect a device to be protected.

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