WO2012113216A1

WO2012113216A1 - Lightning protection circuit

Info

Publication number: WO2012113216A1
Application number: PCT/CN2011/079098
Authority: WO
Inventors: 朱跃生; 王玮峰; 戴养哩
Original assignee: 聚信科技有限公司
Priority date: 2011-02-23
Filing date: 2011-08-30
Publication date: 2012-08-30
Also published as: CN102110980B; CN102110980A

Abstract

A lightning protection circuit comprises a lightning protection device. The lightning protection device comprises a first common mode protecting device (RT2), a second common mode protecting device (RT1, RT3) and a differential mode protecting device (D1, D2). The first common mode protecting device (RT2) is connected between a first power supply output lead (+P) and a common port or between a first power supply input lead and the common port, wherein the first power supply output lead (+P) is a common supply lead connected between a first output port of a Power over Ethernet (PoE) power supply control circuit and an interface region, and the first power supply input lead is a supply lead connected between a first input port of the PoE power supply control circuit and a PoE power supply. The second common mode protecting device (RT1, RT3) is connected between a second power supply output lead (-P1, -P2) and a common port or between a second power supply input lead and the common port or between the first power supply input lead and the second power supply input lead, wherein the second power supply output lead (-P1, -P2) is a supply lead connected between a second output port of the PoE power supply control circuit and the interface region, and the second power supply input lead is a supply lead connected between the second input port of the PoE power supply control circuit and the PoE power supply. The differential mode protecting device (D1, D2) is connected between the first power supply output lead (+P) and the second power supply output lead (-P1, -P2). The lightning protection circuit reduces the number of protecting devices, saves PCB space and decreases the design cost for PoE ports. In addition, as all of the interface regions are connected to the common ports via protecting devices, a relatively large amount of surge energy can be released, achieving a high level of lightning protection.

Description

Lightning protection circuit

The present application claims priority to Chinese Patent Application No. 201110044292.5, the entire disclosure of which is incorporated herein by reference.

Technical field

The present invention relates to the field of communications technologies, and in particular, to a lightning protection circuit.

Background technique

Power over Ethernet (PoE) refers to the transmission of data signals to terminals based on protocols (IP, Internet Protocol) based on the existing Ethernet Cat 5 cabling infrastructure. It can also provide DC power for such devices. PoE technology uses a common Ethernet cable to simultaneously transmit Ethernet signals and DC power, and integrates power and data in the same cable. PoE technology can be used for each. Network terminals, such as: IP phones, wireless access points, portable device chargers, credit card machines, cameras, data acquisition devices, etc., provide reliable, centralized power supply, network terminals do not need external power supply, only one network cable is connected It works fine and it is easy to back up.

With the widespread use of PoE technology, the use environment of PSE (Power Source Equipment), such as PoE switches, is becoming more and more complex. PoE port signal lines often have bad conditions such as households and outdoor overhead lines, which are subject to lightning strikes. The possibility of surges such as surges is greatly increased, making the lightning protection of PoE ports a huge challenge.

The commonly used PoE port lightning protection circuit is shown in Figure 1. It relies entirely on the PoE circuit to the common end.

The insulation withstand voltage of (GND, Ground) realizes the common mode protection of the PoE port. When the surge overvoltage comes from the surge side, it is isolated from the network port on the device side link to the POE power supply to the ground. Both the port and the power supply are isolated by a transformer.) The inrush current does not form a loop, thus ensuring that the device is not damaged. Since PoE power, POE power control circuit, Fast Ethernet (FE, Gigabit Ethernet) interface circuit, etc., devices are connected between the PoE circuit and GND, and these The device cannot withstand the voltage due to the volume limitation. Therefore, in practical applications, the lightning protection capability of the PoE port can only reach 2kV. Although such design cost is low, such protection level cannot be very good. Protect the equipment from reliable operation in actual use.

Another existing PoE port lightning protection circuit is shown in Figure 2. Figure 2 shows only In the case of a PoE port, this solution uses a typical two-stage protection circuit. When the surge overvoltage comes in from the interface area, the common-mode protection is discharged to the ground through the first-level protection device RT2 and RT3. A protective device RT1 performs differential mode protection, and the second level protections D1, D2, and D3 are further clamped to further reduce the surge voltage. However, this technology has two shortcomings: 1. Each port must be equipped with a large number of protective devices, and these protective devices are packaged very large. When there are many ports, a large number of printed circuit boards (PCB, Printed Circuit Board) are required. Space, which contradicts the development of PSE devices in the direction of miniaturization (ports are becoming more and more dense, PCB layout is also more and more compact), which makes this solution difficult to obtain on PSE devices with high-density POE ports. Widely used; 2. The (1.2) and (3.6) lines of the network port do not add protective devices, and are protected by isolation. The (4.5) and (7.8) lines are protected by surge devices. Later, the protective devices of the (4.5) and (7.8) lines operate to lower the surge voltage, while the (1.2) and (3.6) lines are still in a high voltage state, and breakdown may occur between the high voltage and the low voltage. It also does not reach a high level of protection and does not guarantee reliable operation of the equipment in actual use.

Summary of the invention

The embodiment of the invention provides a lightning protection circuit for providing protection against lightning protection of the PoE port, saving PCB space and reducing the design cost of the PoE port.

The lightning protection circuit provided by the embodiment of the invention includes:

The lightning protection device is used for protecting the PoE port from the surge voltage. The lightning protection device comprises: a first common mode protection device, a second common mode protection device and a differential mode protection device;

The first common mode protection device is connected between the first power output line and the common terminal, or the first common mode protection device is connected between the first power input line and the common end, wherein the first power output line is a PoE power source a first power supply line connected to the interface area by the first output end of the control circuit, and the first power input line is a power supply line connected to the PoE power source by the first input end of the PoE power control circuit;

The second common mode guard device is connected between the second power output line and the common terminal, or the second common mode guard device is connected between the second power input line and the common terminal, or the second common mode guard device is connected to Between the first power input line and the second power input line, wherein the second power output line is a power supply line connected to the interface area by the second output end of the PoE power control circuit, and the second power input line is a PoE power control circuit a power supply line connected to the PoE power supply at the second input;

The differential mode protection device is connected between the first power output line and the second power output line. As can be seen from the foregoing technical solutions, a lightning protection circuit provided by an embodiment of the present invention has the following advantages: The common mode protection device is deployed on the output end of the PoE power control circuit and the shared power supply line connected to the interface area or PoE. The input end of the power control circuit and the power supply line connected to the PoE power supply minimize the number of guard devices, save PCB space and reduce the design cost of the PoE port, and at the same time, all the interface areas are connected to the common end with guard devices. It can discharge large surge energy and achieve high-standard lightning protection.

DRAWINGS

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly described below. It is obvious that the drawings in the following description are only some embodiments of the present invention. Other drawings may also be obtained from those skilled in the art from the drawings.

1 is a schematic diagram of a PoE port lightning protection circuit in the prior art;

2 is a schematic diagram of another PoE port lightning protection circuit in the prior art;

FIG. 3-a is a schematic diagram of a lightning protection circuit according to Embodiment 1 of the present invention; FIG.

FIG. 3 is a schematic diagram of another lightning protection circuit according to Embodiment 1 of the present invention; FIG.

FIG. 3 is a schematic diagram of a working principle of lightning protection when a lightning protection circuit is subjected to a surge overvoltage according to Embodiment 1 of the present invention; FIG.

FIG. 3 is a schematic diagram of a working principle of a lightning protection circuit for protecting a differential mode voltage according to Embodiment 1 of the present invention; FIG.

FIG. 4 is a schematic diagram of a lightning protection circuit according to Embodiment 2 of the present invention; FIG.

FIG. 4 is a schematic diagram of another lightning protection circuit according to Embodiment 2 of the present invention; FIG.

Figure 4-d is a schematic diagram of the working principle of a lightning protection circuit according to the second embodiment of the present invention; Figure 4-e is a schematic diagram of the working principle of a lightning protection circuit according to the second embodiment of the present invention; It is a schematic diagram of the working principle of a lightning protection circuit provided by the second embodiment of the present invention; and FIG. 4g is a schematic diagram of another lightning protection circuit provided by the second embodiment of the present invention.

detailed description

The embodiment of the invention provides a lightning protection circuit for providing protection specifications for a PoE port. High lightning protection while saving PCB space and reducing the design cost of PoE ports.

In order to make the object, the features and the advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. The described embodiments are only a part of the embodiments of the invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of the present invention. Embodiment 1

A lightning protection circuit provided by the embodiment of the present invention specifically includes: a lightning protection device for protecting a PoE port from surge and overvoltage. The lightning protection device includes: a first common mode protection device, and a second total a mode guard device and a differential mode guard device, the first common mode guard device is connected between the first power output line and the common terminal, or the first common mode guard device is connected between the first power input line and the common end, wherein The first power output line is a common power supply line connected to the interface area by the first output end of the PoE power control circuit, and the first power input line is a power supply line connected to the PoE power source by the first input end of the PoE power control circuit; The second common mode protection device is connected between the second power output line and the common end, wherein the second power output line is a power supply line connected to the interface area by the second output end of the PoE power control circuit; the differential mode protection device is connected to the Between a power output line and a second power output line.

Please refer to FIG. 3-a, which is a practical application of a lightning protection circuit according to the present invention. The lightning protection circuit includes two interface areas 1#, 2# as an example, but in practical applications, It is not limited to two interface areas, and may also include two or more interface areas, which are not limited herein. As shown in Figure 3-a, the first output of the PoE power control circuit is connected to the interface area 1# and the interface area 2#. The first power output line + P is shared, and there is a common point A. In practical applications, The other output terminals of the PoE power control circuit are connected to the interface area 1#, and the power output lines of the interface area 2# - PI , - P2 may also be shared. For example, the PoE power control circuit's return terminal (RTN, return) or -48V, as for RTN or -48V, is common, depending on the MOSFET (Metal-Oxide-Semiconductor) that controls the POE power output. On which power supply line, the most common is that the MOS tube is at -48V, then the RTN is shared. Only one common mode protection device can be deployed on the shared power supply line, that is, only one common mode protection device is deployed on the shared power supply line of multiple interface areas, thereby reducing the protection of the device.

It should be noted that, in FIG. 3-a, RT2 is the first common mode protection device in the embodiment of the present invention. The RT2 is connected between the first power output line and the common end, and the RT1 and the RT3 are the second common mode protection device in the embodiment of the present invention. The first common mode protection device RT2 can also be connected to the first power input line and the common end. Between, as shown in Figure 3-b. In practical applications, the first common mode protection device and the second common mode protection device may specifically be varistor, gas discharge tube, thyristor (TSS, thyristor), transient suppression diode (TVS, Transient Voltage Suppressor) or commonly used The protective device, the combination thereof and the like are not limited herein. Dl, D2 is a differential mode protection device in the embodiment of the present invention. In practical applications, the differential mode protection device may specifically be a transient suppression diode, or a common protection device such as a thyristor, a varistor, a gas discharge tube, and the like. The combination thereof is not limited herein.

In practical applications, in order to prevent electromagnetic interference, a filter component such as a common mode inductor, a magnetic bead, or the like may be connected between the first power output line and the second power output line, as shown in FIG. 3-a. The filter element is added as an example for illustration. As shown in Figure 3-c, a schematic diagram of adding a filter component to the lightning protection circuit is given. To improve reliability, an overcurrent protection device can be connected to the first power output line and/or the second power output line. The overcurrent protection device includes: a fuse, a thermistor.

The working principle of the lightning protection when the lightning protection circuit in the embodiment of the present invention is subjected to a surge overvoltage is described below with reference to the lightning protection circuit shown in FIG. 3-a:

When the surge input voltage senses the surge overvoltage, the overvoltage is vented to ground through the common mode protection devices RT1 and RT2, which protects the subsequent stage circuit, as shown in Figure 3-d. Surge is generally a common mode voltage, but if there is an imbalance on the line, a certain differential mode voltage is generated. In the embodiment of the invention, the differential mode protection devices D1 and D2 ensure that the device is more reliable in operation and realizes Differential mode protection, as shown in Figure 3-e.

In the embodiment of the present invention, the common mode protection device is deployed in the output end of the PoE power control circuit and the power supply line shared by the interface area or the input end of the PoE power control circuit and the power supply line of the PoE power supply, in multiple interface areas. Only one common mode protection device is deployed on a common power supply line. Compared with the prior art, the number of protection devices can be reduced, the PCB space is saved, and the design cost of the PoE port is reduced. At the same time, since all the interface areas are common to each other. They are connected with protective devices, which can discharge large surge energy and achieve high-standard lightning protection.

It should be noted that, in the first embodiment, other layout situations not illustrated by the second common mode protection device will be described in the second embodiment. Please refer to the second embodiment. A lightning protection circuit provided by an embodiment of the present invention specifically includes: a lightning protection device for protecting a port from a surge voltage; the lightning protection device includes: a first common mode protection device, and a second a mode guard device and a differential mode guard device, wherein the first common mode guard device is connected between the first power input line and the common terminal, or the first common mode guard device is connected between the first power output line and the common end The first power input line is a power supply line connected to the first input end of the power control circuit and the power supply line, and the first power output line is a common power supply line connected to the interface area by the first output end of the power control circuit; The second common mode protection device is connected between the second power input line and the common terminal, or the second common mode protection device is connected between the first power input line and the second power input line, and the second power input line is a power supply a second input end of the control circuit is connected to the power supply line of the ΡοΕ power supply; the differential mode protection device is connected between the first power output line and the second power output line, the second power A second output line is connected to the output terminal of the power supply line of the interface region ΡοΕ power supply control circuit.

Please refer to FIG. 4-a, which is a practical application of a lightning protection circuit in the present invention. The lightning protection circuit includes an interface area 1#, 2#... N# as an example, but in practical applications. Medium does not limit the number of interface areas. As shown in Figure 4-a, the output of the PoE power supply is + P and - P. After the POE power control circuit, it is divided into N channels, where + PI ~ + PN and + P are straight-through, and the PoE power control circuit is the first. The input end is connected to the PoE power + P port through the first power input line, the second input end of the PoE power control circuit is connected to the PoE power supply - P port through the second power input line, and the first power output of the PoE power control circuit The line is the first output end + P1 and the interface area 1#, the first output end + P2 and the interface area 2#, the first output end + PN and the interface area N# share a power supply line, in practical applications, The other output of the PoE power control circuit to the interface area 1#, 2#... N# power output line - Pl, - P2... - PN can also be shared. For example, the RTN of the PoE power control circuit or -48V, as for the RTN or -48V, is shared, depending on which power supply line the MOS tube that controls the P0E power output is, the most common is the MOS tube at -48V, then the RTN It is shared. All the power supply input lines and the power supply output lines of the PoE power control circuit share two common mode protection devices, which greatly reduces the number of common mode protection devices. In Figure 4-a, there are only two common mode protection devices, which are in the embodiment of the present invention. The first common mode guard device is RT1, and the second common mode guard device in the embodiment of the present invention is RT2. It should be noted that, in practical applications, the first common mode guard device RT1 can also be connected to the first power source. The output line and the common end are shown in Figure 4-b on the basis of Figure 4-a. The second common mode protection device RT2 can also be connected between the first power input line and the second power input line, in Figure 4-a The basis is given in Figure 4-c.

In a practical application, the first common mode protection device and the second common mode protection device may be varistor, gas discharge tube, thyristor, TVS tube or common protective device, and the like, and are not limited herein. Dl, D2...DN is the differential mode protection device in the embodiment of the present invention. In practical applications, the differential mode protection device may specifically be a TVS tube, or a common protection such as a thyristor, a varistor, a gas discharge tube, and the like. The device and its combination are not limited herein.

In practical applications, in order to prevent electromagnetic interference, a filter component such as a common mode inductor, a magnetic bead, or the like may be connected between the first power output line and the second power output line. For details, refer to Figure 3-c. A schematic diagram of the addition of filter components in the lightning protection circuit is shown. In order to improve reliability, an overcurrent protection device may be connected to the first power input line and/or the second power input line, and the overcurrent protection device includes: a fuse, a thermistor.

The working principle of the lightning protection when the lightning protection circuit in the embodiment of the present invention is subjected to a surge overvoltage is described below with reference to the lightning protection circuit shown in FIG. 4-a:

When using POE power supply, the MOS tube on -48V ( +P ) is in the closed state. When the external cable senses a forward surge, the surge energy reaches the RT1 and RT2 of the latter stage and is discharged to the ground. To positive surge protection, as shown in Figure 4-d. When the POE power supply is not used, when the MOS transistor on the -48V is disconnected, if the external cable senses the forward surge voltage at this time, the surge energy on the -PI ~ - PN can pass through the D1 respectively. Go to the DN to + PI ~ + PN, and finally vent to the ground through RT1, as shown in Figure 4-e.

When the POE power supply is not used, the MOS tube on the -48V can be in the off state. When the external cable senses the negative surge pulse, the surge energy can be channeled through the body diode on the MOS tube to protect the MOS tube. effect. When using POE power supply, the MOS transistor on -48V is in the closed state, when the surge energy is discharged through the MOS tube, as shown in Figure 4-f. Due to the imbalance between the pairs, +P1 and -PI, + P2 and - P2, and - differential mode voltages may be generated between the pairs between PN and + PN, which can also be protected by D 1 - DN. .

Through the above analysis of the working principle of the lightning protection circuit subjected to the surge overvoltage, it can be well protected whether the positive or negative common mode or differential mode surge is sensed on the cable. It should be noted that the breakdown voltage requirement of the differential mode protection device D1-DN is greater than the maximum output voltage of the POE power supply, to avoid breakdown during normal operation, and the clamp voltage should be as low as possible. It should be noted that the lightning protection circuit in the embodiment of the present invention may further include a PoE power control circuit, as shown in FIG. 4-a or FIG. 4-b or FIG. 4-c, in order to further improve the protection performance, The MOS tube in the PoE power control circuit is connected with a protective device at both ends, such as a Schottky diode or a TVS tube, a thyristor, a gas discharge tube, a varistor or a commonly used protection device in the industry, and the like, as shown in Figure 4-g. As shown, the unidirectional protection devices D11 - DNN are connected in parallel at both ends of the MOS transistor.

In the embodiment of the present invention, the common mode protection device is deployed on the input end of the PoE power control circuit and the power supply line connected to the PoE power supply or on the power supply line shared by the output end of the PoE power control circuit and the interface area, due to the entire defense. The lightning protection circuit only deploys a common mode protection device at the two input ends of the PoE power control circuit, which greatly reduces the number of protection devices compared with the prior art, saves PCB space and reduces the design cost of the PoE port. At the same time, because all the interface areas are connected with protective devices on the common end, it can discharge large surge energy and achieve high-standard lightning protection.

A person skilled in the art may understand that all or part of the various steps of the foregoing embodiments may be completed by a program instructing related hardware. The program may be stored in a computer readable storage medium, and the storage medium may include: ROM, RAM, disk or CD, etc.

The lightning protection circuit provided by the embodiment of the present invention is described in detail above. The principle and the embodiment of the present invention are described in the following. The description of the above embodiment is only used to help understand the method of the present invention. And the core idea of the present invention; at the same time, those skilled in the art, according to the idea of the present invention, there will be changes in the specific embodiments and application scope. In summary, the content of the present specification should not be construed as the present invention. limits.

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Claims

Rights request

A lightning protection circuit, comprising: lightning protection device for protecting an Ethernet power supply PoE port is not damaged by a surge voltage;

The lightning protection device comprises: a first common mode protection device, a second common mode protection device and a differential mode protection device;

The first common mode guard device is connected between the first power output line and the common end, or the first common mode guard device is connected between the first power input line and the common end, wherein the first The power output line is a common power supply line connected to the interface area by the first output end of the PoE power control circuit, and the first power input line is a power supply line connected to the PoE power source by the first input end of the PoE power control circuit; The second common mode guard device is connected between the second power output line and the common end, or the second common mode guard device is connected between the second power input line and the common end, or the second common mode The protection device is connected between the first power input line and the second power input line, wherein the second power output line is a power supply line connected to the interface area by the second output end of the PoE power control circuit. The second power input line is a power supply line connected to the PoE power source at a second input end of the PoE power control circuit; the differential mode guard device is connected to the first power output line and the second power output line Room.

2. The lightning protection circuit according to claim 1, wherein a filter member is connected between the first power output line and the second power output line.

3. The lightning protection circuit according to claim 1, wherein an overcurrent protection device is connected to the first power output line and/or the second power output line.

The lightning protection circuit according to claim 1, wherein the first common mode protection device comprises: a varistor, a gas discharge tube, a thyristor, a transient suppression diode TVS;

The second common mode protection device comprises: a varistor, a gas discharge tube, a thyristor, a TVS.

The lightning protection circuit according to claim 1, wherein the differential mode protection device comprises: a transient suppression diode TVS, a thyristor, a varistor, and a gas discharge tube.

The lightning protection circuit according to claim 2, wherein the filter device comprises: a common mode inductor and a magnetic bead.

7. The lightning protection circuit according to claim 3, wherein the overcurrent protection device comprises: a fuse, a thermistor.

8. The lightning protection circuit of claim 1, further comprising: a PoE power source control circuit.

9. The lightning protection circuit according to claim 8, wherein a protective device is connected in parallel at both ends of the insulating field effect transistor in the PoE power supply control circuit.

10. The lightning protection circuit according to claim 9, wherein the protection device comprises: a Schottky diode, a transient suppression diode TVS, a thyristor, a gas discharge tube, and a varistor.