CN109390924A

CN109390924A - Surging protection circuit and POE system

Info

Publication number: CN109390924A
Application number: CN201811056080.7A
Authority: CN
Inventors: 程为安
Original assignee: Ruijie Networks Co Ltd
Current assignee: Ruijie Networks Co Ltd
Priority date: 2018-09-11
Filing date: 2018-09-11
Publication date: 2019-02-26

Abstract

The embodiment of the present application provides a kind of surging protection circuit and POE system.Wherein, surging protection circuit includes: the first lightning protection circuit, the second lightning protection circuit, first switch circuit, gating circuit and differential mode protection circuit.Based on specific circuit structure, when negative pressure surge is applied to POE system, negative pressure surge current flows to the negative feeder ear of POE system from the earth by the second lightning protection circuit；And from the earth, by the first anti-thunder tube, most flows directly to the positive feeder ear of POE system to negative pressure surge current, it is flow to negative feeder ear by differential mode protection circuit and gating circuit by the negative pressure surge current remainder of the first anti-thunder tube, thus negative pressure surge energy of releasing.In this way; the protection circuit can not only release surge energy, realize the protection to POE power supply unit, also negative pressure surge current can be made not flow to Switching Power Supply; and then avoidable surge current leads to the Voltage Drop of Switching Power Supply, so as to reduce the probability of POE system power down.

Description

Surge protection circuit and POE system

Technical Field

The application relates to the technical field of power over Ethernet, in particular to a surge protection circuit and a POE system.

Background

With the development of internet technology, people not only may need to access the internet quickly at any time and any place, but also need to collect and receive data at a remote end in real time, which requires the realization of remote power supply for internet remote equipment. In order to meet the needs of people, Power Over Ethernet (POE) technology has come to work.

The POE technology refers to a technology that, without any change in the existing ethernet cat.5 wiring infrastructure, can provide dc power for some terminals (such as an IP telephone, a wireless lan access point, a network camera, etc.) based on an Internet Protocol (IP) while transmitting data signals. The POE technology can ensure the safety of the existing structured wiring and ensure the normal operation of the existing network, thereby reducing the cost to the maximum extent.

The POE system includes two parts, namely, a Power Sourcing Equipment (PSE) and a Powered Device (PD). The PSE device is a device for supplying power to the ethernet client device, and is also a manager of the entire POE ethernet power supply process. And the PD device is a PSE load that accepts power, i.e., a client device of the POE system. The power supply of the POE system generally employs a switching power supply.

However, the POE system generally needs to lay and connect the ethernet cable outdoors, and when external surge interference is interfered on the ethernet cable, the POE system is easily damaged due to the external surge impact. These surge disturbances include lightning strikes, car discharges, and the like. Although the existing surge protection circuit can effectively prevent the POE system from being affected by surge interference, when negative voltage surge acts on the surge protection circuit, the voltage of the switching power supply sometimes falls, and then the POE system is restarted after power failure.

Disclosure of Invention

A plurality of aspects of this application provide a surge protection circuit and POE system for switching power supply of PSE system appears falling when preventing to meet the negative pressure surge, and then can reduce the probability that POE system falls electric.

The embodiment of the application provides a surge protection circuit is applicable to the POE system, include: the lightning protection circuit comprises a first lightning protection circuit, a second lightning protection circuit, a first switch circuit, a gating circuit and a differential mode protection circuit; wherein,

the first lightning protection circuit is electrically connected between a positive phase power supply end of the POE system and the ground; the second lightning protection circuit is electrically connected between the negative phase power supply end of the POE system and the ground; the first switch circuit is electrically connected between the positive phase power supply end and the negative phase power supply end;

the gating circuit is connected between the voltage output end of the POE power supply equipment in the POE system and a grounding end; the connection point of the gating circuit and the voltage output end is directly connected with the negative phase power supply end; the connection point of the gating circuit and the grounding end is electrically connected with the negative pole of the switching power supply of the POE system;

the differential mode protection circuit is connected between the positive phase power supply end and the negative electrode of the switching power supply; and the connecting point of the differential mode protection circuit and the positive phase power supply end is directly connected with the anode of the switch power supply.

The embodiment of the present application further provides a POE system, including: POE power supply unit, POE powered device, switching power supply and above-mentioned surge protection circuit.

The surge protection circuit that this application embodiment provided includes: the lightning protection circuit comprises a first lightning protection circuit, a second lightning protection circuit, a first switch circuit, a gating circuit and a differential mode protection circuit. Based on the surge protection circuit provided by the embodiment of the application, when negative voltage surge is applied to the POE system, the surge protection circuit can enable the negative voltage surge current to flow to a negative phase power supply end of the POE system from the ground through the second lightning protection circuit; negative-pressure surge current can directly flow to the positive-phase power supply end of the POE system from the ground through a large part of the first anti-explosion device, and the residual negative-pressure surge current flowing through the first anti-explosion device flows to the negative-phase power supply end through the differential mode protection circuit and the gating circuit. Like this, not only can discharge the surge energy, realize the protection to POE power supply unit, still can make negative pressure surge current can not flow to switching power supply, and then can avoid surge current to lead to switching power supply's voltage to fall to can reduce the probability that POE system falls electricity.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:

fig. 1 is a schematic structural diagram of a surge protection circuit according to an embodiment of the present application;

fig. 2a is a circuit structure diagram of a surge protection circuit and a current flow direction diagram of a positive voltage surge thereof according to an embodiment of the present application;

fig. 2b is a circuit structure diagram of a surge protection circuit and a current flow direction diagram of a negative voltage surge thereof according to an embodiment of the present application;

fig. 2c is a circuit structure diagram of a surge protection circuit adopting the ieee802.3bt standard according to the embodiment of the present application;

fig. 3 is a schematic structural diagram of a POE system according to an embodiment of the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be described in detail and completely with reference to the following specific embodiments of the present application and the accompanying drawings. It should be apparent that the described embodiments are only some of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

To current surge protection circuit can lead to switching power supply's voltage to fall and lead to the technical problem that POE system falls down when the negative voltage surge effect, the embodiment of the application provides a surge protection circuit, include: the lightning protection circuit comprises a first lightning protection circuit, a second lightning protection circuit, a first switch circuit, a gating circuit and a differential mode protection circuit. Based on the surge protection circuit, when positive voltage surge acts on the POE system, the positive voltage surge current flows to the ground from a positive phase power supply end of the POE system through the first lightning protection circuit; the current flows to the ground from a negative phase power supply end of the POE system through the first switch circuit and the first lightning protection circuit; thereby bleeding off the positive surge energy. When the negative voltage surge is applied to the POE system, the surge protection circuit can flow the negative voltage surge current from the ground to the negative phase power supply end of the POE system through the second lightning protection circuit; negative-pressure surge current can directly flow to the positive-phase power supply end of the POE system from the ground through a large part of the first anti-detonator, and the residual negative-pressure surge current passing through the first anti-detonator flows to the negative-phase power supply end through the differential mode protection circuit and the gating circuit, so that negative-pressure surge energy is released. Like this, this protection circuit not only can discharge the surge energy, realizes the protection to POE power supply unit, still can make negative pressure surge current can not flow to switching power supply, and then can avoid surge current to lead to switching power supply's voltage to fall to can reduce the probability that POE system falls electricity.

The technical solutions provided by the embodiments of the present application are described in detail below with reference to the accompanying drawings.

It should be noted that: like reference numerals refer to like objects in the following figures and embodiments, and thus, once an object is defined in one figure, further discussion thereof is not required in subsequent figures.

Fig. 1 is a schematic structural diagram of a surge protection circuit according to an embodiment of the present application. The surge protection circuit is suitable for a POE system. As shown in fig. 1, the surge protection circuit includes: a first lightning protection circuit 10a, a second lightning protection circuit 10b, a first switching circuit 10c, a gating circuit 10d and a differential mode protection circuit 10 e.

The first lightning protection circuit 10a is electrically connected between the positive phase power supply end P + of the POE system and the ground; the second lightning protection circuit 10b is electrically connected between the negative phase power supply end P-of the POE system and the ground; the first switch circuit 10c is electrically connected between the positive phase power supply terminal P + and the negative phase power supply terminal P-.

The gating circuit 10d is connected between a voltage output end U of a POE power supply device (PSE chip) 10f in the POE system and a ground end G; the connection point of the gating circuit 10d and the voltage output end U is directly connected with the negative phase power supply end P < - >; the connection point of the gating circuit 10d and the ground terminal G of the POE power supply device (PSE chip) 10f is electrically connected to the negative electrode E-of the switching power supply 10G of the POE system.

The differential mode protection circuit 10E is connected between the positive phase power supply end P + and the negative electrode E-of the switching power supply 10 g; and the connecting point of the differential mode protection circuit 10E and the positive phase power supply end P + is directly connected with the anode E + of the switching power supply 10 g.

Based on the surge protection circuit, when a positive voltage surge acts on the POE system, as shown by a dotted arrow in fig. 1, the positive voltage surge current flows to the ground from a positive phase power supply end P + of the POE system through the first lightning protection circuit 10 a; and flows to the ground from the negative phase power supply end P-of the POE system through the first switch circuit 10a and the first lightning protection circuit 10a, so that positive voltage surge energy is discharged, and the protection of POE power supply equipment (PSE chip) 10f is realized.

When the negative surge is applied to the POE system, as shown by the solid arrow in fig. 1, the negative surge current flows from the ground through the second lightning protection circuit 10b to the negative phase power supply terminal P-of the POE system. Because the differential mode protection circuit 10e has the potential to cause a certain voltage drop, when the negative voltage surge current discharges energy from the ground through the first detonator 10a, most of the negative voltage surge current passing through the first detonator 10a directly flows to the positive phase power supply end P + of the POE system, and the rest of the negative voltage surge current flows to the negative phase power supply end P-through the differential mode protection circuit 10e and the gating circuit 10d, so that the negative voltage surge energy can be discharged, and the protection of the POE power supply equipment (PSE chip) 10f is realized.

Based on the above analysis, the surge protection circuit provided by this implementation can realize the protection of POE power supply equipment (PSE chip) when positive voltage surge and negative voltage surge act on the POE system.

For the switching power supply 10g, a feedback dynamic adjustment module is present therein to achieve stable voltage output, that is, to stabilize the output voltage of the switching power supply 10 g. When the output load of the switching power supply 10g changes, the feedback dynamic adjustment module in the switching power supply 10g needs a certain response time to complete the voltage stabilization. If an instantaneous current, such as a surge current, is applied to the switching power supply 10g at the moment, the feedback dynamic adjustment module in the switching power supply 10g cannot respond to the instantaneous current in time or the adjustment capability is insufficient, so that the voltage of the switching power supply 10g drops. In the surge protection circuit provided by this embodiment, because the second lightning protection circuit is not connected to the negative electrode E of the switching power supply 10g, and the differential mode protection circuit 10E and the gating circuit 10d act on each other, the path of the capacitance energy inside the negative voltage surge discharge and the switching power supply 10g can be blocked, so that the negative voltage surge current cannot flow to the switching power supply 10g, therefore, the problem that the surge current is instantaneously injected into the switching power supply 10g to cause voltage drop can be avoided, and the power failure probability of the POE system can be reduced.

It is worth noting that for the POE power supply device (PSE chip) 10f, the voltage output terminal U thereof is a power supply control terminal for the powered device (PD device) in the POE system. A switching device is generally connected to a voltage output end of the PSE chip, and optionally, the switching device may adopt an MOS transistor, and the PSE chip controls the power supply of the PD device by controlling the gating and closing of the MOS transistor. According to POE power supply equipment (PSE chip) 10f manufacturer's scheme difference, some PSE chips are integrated inside this chip with the MOS pipe, and some are with the MOS pipe setting in the outside of PSE chip, and the surge protection circuit that this embodiment provided all is suitable for. For the PSE chip with the MOS transistor integrated inside, the gating circuit 10d is directly connected to the ground terminal U of the POE power supply device (PSE chip) 10 f; for the PSE chip with the MOS transistor provided outside, the gate circuit 10d is connected to the ground terminal U of the POE power supply device (PSE chip) 10f through the MOS transistor.

In the embodiment of the present application, a specific circuit structure of the surge protection circuit is not limited, and any circuit structure that can implement the above functions may be used in the present application. The following describes an exemplary implementation form and operation principle of each module in fig. 1 with reference to a specific circuit structure diagram of the surge protection circuit shown in fig. 2 a.

As shown in fig. 2a, the first lightning protection circuit 10a may be a detonator RV3, wherein the detonator RV3 is electrically connected between the positive phase power supply terminal P + of the POE system and ground. Alternatively, the detonator RV3 may employ a varistor, a gas discharge tube, a bidirectional Transient suppression diode (TVS) or a semiconductor discharge Tube (TSS) or the like, but is not limited thereto.

Optionally, the second lightning protection circuit 10b comprises: a second switching circuit 10b1 and a detonator RV 2. The second switching circuit 10b1 is connected between the negative phase power supply end P-and the anti-explosion device RV 2; and one end of the detonator RV2, which is not connected with the second switch circuit 10b1, is grounded. Wherein, second switch circuit 10b1 can switch on second lightning protection circuit 10b when the negative voltage surge is used, thereby makes negative voltage surge current can flow to negative phase power supply terminal P from ground through second lightning protection circuit 10b, thereby releases surge energy, protection POE power supply equipment (PSE chip) 10 f. In addition, for the voltage output by the voltage output terminal of the POE power supply device (PSE chip) 10f, the second switching circuit 10b1 can block the voltage from flowing to the second lightning protection circuit 10b, so as to reduce the divided voltage of the output voltage of the POE power supply device (PSE chip) 10f, so as to supply power to the POE powered device (shown in fig. 2 a) as much as possible, thereby further reducing the power consumption of the surge protection circuit.

On the other hand, in practical applications, the POE power supply device (PSE chip) 10f is generally connected to have a plurality of voltage output terminals for connecting a plurality of POE powered devices. For example, an exchange typically has multiple network interfaces for connecting to multiple IP phones, and the exchange can supply power to the IP phones while transmitting data signals. This requires surge protection of each voltage output terminal of the POE power supply device (PSE chip) 10 f. In this embodiment, because the setting of second switch circuit 10b1, then can concatenate the one end that is not connected with negative phase supply end of second switch circuit 10b1 among the surge protection circuit of each voltage output end of POE power supply equipment (PSE chip) 10f with detonator RV2 after connecting together, then can make the same detonator RV2 of surge protection circuit sharing of a plurality of voltage output ends like this, not only can practice thrift detonator RV 2's quantity, save hardware cost, can also improve the integrated level of device, save printed circuit board (PCB board) space. Correspondingly, for the second lightning protection circuit 10b, if the second switching circuit 10b1 is not provided, that is, the detonator RV2 is connected between the negative phase power supply terminal P-and the ground, if the detonator RV2 is intended to be shared by surge protection circuits of multiple voltage outlets, the connection points of the multiple voltage outlets and the negative phase power supply terminal P-need to be connected together, which may cause crosstalk between data transmission signals among multiple POE powered devices, and affect the quality of data communication.

Alternatively, the explosion prevention cap RV2 may be a piezoresistor, a gas discharge tube, a bidirectional TVS tube or a TSS tube, etc., but is not limited thereto.

Further, as shown in fig. 2a, the second switch circuit 10b1 includes a diode D2, and the cathode of the diode D2 is electrically connected to the negative phase power supply terminal P "; the anode of the diode D2 is electrically connected to the detonator RV 2.

Alternatively, the second switch circuit 10b1 may also include any other device with unidirectional conduction. Such as a unidirectional TVS transistor, MOS transistor, etc., but not limited thereto. The cathode of the unidirectional TVS tube is electrically connected with the negative phase power supply end P-while the anode thereof is connected with the ungrounded end of the anti-detonator RV 2. For the MOS tube, an N-MOS tube is taken as an example, wherein the grid electrode of the N-MOS tube is connected with the ungrounded end of the detonator RV2 after being in short circuit with the source electrode, and the drain electrode of the N-MOS tube is electrically connected with the negative phase power supply end P-.

Further, alternatively, as shown in fig. 2a, the first switching circuit 10c may include: and the diode D1, wherein the anode of the diode D1 is electrically connected with the negative phase power supply end P-of the POE system, and the cathode thereof is electrically connected with the positive phase power supply end P +.

Alternatively, the first switch circuit 10c may be any other device with a unidirectional conduction function, such as a unidirectional TVS transistor, a MOS transistor, etc., but is not limited thereto. Wherein, the anode of the unidirectional TVS tube is electrically connected with the negative phase power supply end P-and the cathode thereof is electrically connected with the positive phase power supply end P +. For the MOS transistor, take N-MOS transistor as an example, wherein the grid electrode and the source electrode of the N-MOS transistor are electrically connected with the negative phase power supply end P-after being short-circuited, and the drain electrode is electrically connected with the positive phase power supply end P +.

Alternatively, as shown in fig. 2a, the gating circuit 10D may include a diode D3, wherein a cathode of the diode D3 is electrically connected to the voltage output terminal U of the POE power supply device (PSE chip) 10f, and an anode thereof is electrically connected to the ground terminal G of the POE power supply device (PSE chip) 10 f; and the junction of diode D3 and ground G is connected to the negative E-of switching power supply 10G.

Further, optionally, the differential mode protection circuit 10e includes: an electrolytic capacitor C1 and a TVS tube D4 connected in parallel with the electrolytic capacitor C1. Wherein, the positive electrode of the electrolytic capacitor C1 and one end of the TVS tube D4 are respectively and electrically connected with the positive phase power supply end P +; the negative electrode of the electrolytic capacitor C1 and the other end of the TVS tube D4 are respectively electrically connected with the negative electrode E-of the switching power supply. Wherein, when the TVS tube D4 is a bidirectional TVS tube, the two ends thereof do not have the cathode and anode portions; when the TVS tube D4 is a unidirectional TVS tube, its cathode is electrically connected to the positive phase power supply terminal P +, and its anode is electrically connected to the negative electrode E-of the switching power supply. The differential mode protection circuit 10e can clamp the operating voltage of the POE power supply device (PSE chip) 10 f.

Further, the maximum working voltage of the TVS tube D4 is greater than the maximum working voltage of the POE power supply device (PSE chip) 10f and less than the minimum damage voltage of the POE power supply device (PSE chip) 10f, so as to ensure that the voltage fluctuation between the positive electrode E + and the negative electrode E-of the switching power supply 10g does not exceed the working range of the POE power supply device (PSE chip) 10f when surge interference such as lightning stroke occurs, thereby further protecting the POE power supply device (PSE chip) 10 f. The minimum damage voltage of the POE power supply device (PSE chip) 10f is the minimum voltage that may damage the device, and is a factory attribute value of the POE power supply device (PSE chip) 10 f.

The operation principle of the surge protection circuit will be described with reference to the circuit configuration shown in fig. 2 a.

As shown by a dotted arrow in fig. 2a, when a positive voltage surge acts on the POE system, a positive voltage surge current of the positive phase power supply terminal P + flows from the positive phase power supply terminal P + to the ground through the detonator RV3, so that surge energy is discharged; the positive surge current of the negative phase power supply end P-flows to the ground from the negative phase power supply end P-through the diode D1 and the detonator RV3, and then the surge energy is discharged. Based on this, when the positive voltage surge acts on the POE system, the surge protection circuit provided by the embodiment can realize the protection of the POE power supply device (PSE chip) 10 f.

As shown by a dotted arrow in fig. 2b, when a negative voltage surge acts on the POE system, ideally, the negative voltage surge current flows from the ground to the positive phase power supply end P + through the surge current of the detonator shielding RV3, and the surge energy passing through the detonator shielding RV3 is discharged. However, in practical application, a certain surge residual voltage may exist on the negative-phase power supply terminal P-and the positive-phase power supply terminal P +, and when the surge residual voltage of the negative-phase power supply terminal P-is much lower than that of the positive-phase power supply terminal P +, a small part of the surge current passing through the detonator arrester RV3 flows to the negative-phase power supply terminal P-through the TVS tube D4 in the differential mode protection circuit 10e and the diode D3 in the gating circuit 10D, so that the part of the surge current does not pass through the POE power supply device (PSE chip) 10f, thereby protecting the POE power supply device (PSE chip) 10 f. When the surge residual voltage of the negative phase power supply end P-is far lower than that of the positive phase power supply end P +, the surge current passing through the detonator RV3 also flows to the electrolytic capacitor C1 in the differential mode protection circuit 10e, and the surge energy is absorbed by the electrolytic voltage C1, that is, the surge current charges the electrolytic capacitor C1. And because the negative electrode of the switching power supply 10g is not connected with the ungrounded end of the detonator RV2, when the surge residual voltage of the positive phase power supply end P + and the surge residual voltage of the negative phase power supply end P-are close or the surge residual voltage of the positive phase power supply end P + is lower than the surge residual voltage of the negative phase power supply end P-the surge residual voltage, the surge current can not flow to the negative electrode of the electrolytic capacitor C1 from the ground through the detonator RV2, the energy of the electrolytic capacitor C1 can not be pumped away, the voltage drop of the switching power supply 10g with two parallel ends caused by the energy of the electrolytic capacitor C1 being pumped away can be avoided, and the power failure of a POE system can be prevented.

Moreover, as shown by the dotted arrow in fig. 2b, when the negative voltage surge acts on the POE system, the negative voltage surge current also flows from the ground to the negative phase power supply terminal P "through the detonator RV2 and the diode D2 in the second lightning protection circuit 10b, so as to discharge the surge energy, and protect the POE power supply equipment (PSE chip) 10 f. And because the connection point FL of the anti-explosion device RV2 and the diode D2 is not connected with the negative electrode E-of the switching power supply 10g, when negative-pressure surge current flows through the anti-explosion device RV2, the surge current cannot flow to the negative electrode of the electrolytic capacitor C1 and the negative electrode E-of the switching power supply 10g, the energy of the electrolytic capacitor C1 and the energy of the switching power supply 10g cannot be pumped away, the voltage drop of the switching power supply 10g can be further avoided, and the power failure probability of the POE system can be reduced.

It should be noted that the surge protection circuit provided in the embodiments of the present application can be applied to a POE system. For the POE system, a network interface is generally used to connect a POE power supply device (PSE chip) and a PD device. A common network interface is an RJ45 connector. Among them, the RJ45 connector is a kind of information socket (i.e. communication outlet) connector in wiring system, and the connector is composed of plug (connector, crystal plug) and socket (module), the plug has 8 grooves and 8 contacts, and its structure is schematically shown as RJ45 in fig. 2a and 2 b.

For an RJ45 connector, the connection mode has established industry standards, namely, the IEEE802.3at/af standard and the IEEE802.3bt standard. Different standards, RJ45 connectors are different in the manner of power and PD equipment connected. For the IEEE802.3at/af standard, an RJ45 connector includes: two sets of supply line pairs and two sets of non-supply line pairs. And the RJ45 connector can adopt two line sequence power supply methods: one is that 4, 5, 7, 8 lines are pairs of power supply lines, over which current can be transmitted, and that 4, 5 are defined as positive electrodes, 7, 8 as negative electrodes; and lines 1, 2, 3 and 6 are two groups of non-power supply line pairs. Another type of power supply is a pair of power supply lines on lines 1, 2, 3 and 6, over which power can be transmitted, with any polarity. For example, 1 and 2 are positive electrodes, 3 and 6 are negative electrodes, or 1 and 2 are negative electrodes, and 3 and 6 are positive electrodes. Accordingly, lines 4, 5, 7, 8 are pairs of non-powered lines.

For the ieee802.3bt standard, an RJ45 connector includes 4 sets of power supply line pairs. The RJ45 connector is connected in different ways according to the power of the connected PD equipment. For a PD device with 60W power, 4 sets of power supply line pairs of the RJ45 connector have no specified positive and negative poles, and for example, 1 and 2 may be used as positive poles, 3 and 6 as negative poles, 4 and 5 as positive poles, and 7 and 8 as negative poles; it is also possible to use 1 and 2 as the negative electrodes, 3 and 6 as the positive electrodes, 4 and 5 as the negative electrodes, and 7 and 8 as the positive electrodes. For a power supply device with power of 90W, the RJ45 connector is wired in the following way: 1. 2 is a negative electrode, 3, 6 are positive electrodes, 4, 5 are positive electrodes, 7, 8 are negative electrodes.

The connection between an RJ45 connector and a surge protection circuit using the ieee802.3at/af standard is described in an exemplary manner with reference to the circuit configurations shown in fig. 2a and 2 b.

As shown in fig. 2a and 2b, wires 1, 2, 3, and 6 of the RJ45 connector are power supply wire pairs, and wires 1 and 2 are positive electrodes, and wires 3 and 6 are negative electrodes; 4. the lines 5, 7 and 8 are non-power supply line pairs. The center taps of the isolation transformers connected with the two power supply line pairs 1 and 2 and the 3 and 6 are respectively and electrically connected with the positive phase power supply end P + and the negative phase power supply end P-of the POE system. Based on the connection mode of the RJ45 connector shown in fig. 2a and 2b, the surge protection circuit further includes: an anti-detonator RV 1; and one end of the detonator RV1 is electrically connected with the center tap of the isolation transformer connected with the two groups of non-power supply line pairs 4 and 5 and the 7 and 8 in the RJ45 connector, and the other end of the detonator is grounded. Thus, when a positive-pressure surge acts on the POE system, as shown by a dotted arrow in FIG. 2a, the surge current flows from the non-power-supply line pair to the ground through the detonator RV1, so that the surge energy is discharged; when negative voltage surge acts on the POE system, as shown by a dotted arrow in FIG. 2b, surge current flows from the ground to a non-power supply line pair through a detonator RV1, so that surge energy is discharged.

Alternatively, the explosion prevention cap RV1 may employ a varistor, a gas discharge tube, a bidirectional TVS tube, a semiconductor discharge tube (TSS tube), or the like, but is not limited thereto.

Further, the connection between the RJ45 connector and the surge protection circuit using the ieee802.3bt standard is exemplarily described with reference to the circuit configuration shown in fig. 2 c.

As shown in fig. 2c, the RJ45 connector uses 1 and 2 as positive, 3 and 6 as negative, 4 and 5 as positive, and 7 and 8 as negative. The center taps of the isolation transformers connected to the power supply line pairs 1 and 2 and the power supply lines 3 and 6 are respectively electrically connected with the positive phase power supply end P + and the negative phase power supply end P-of the POE system, and the center taps of the isolation transformers connected to the power supply line pairs 4 and 5 and the power supply line pairs 7 and 8 are also respectively electrically connected with the positive phase power supply end P + and the negative phase power supply end P-of the POE system. For the surge protection circuit shown in fig. 2c, the diode D5 functions the same as diode D1 for the surge protection circuit to which the supply line pair 4, 5 and 7, 8 are connected; the function of the diode D6 is the same as that of the diode D2, and the function of the diode D7 is the same as that of the diode D3, so reference may be made to the related descriptions in the above embodiments, and further description is omitted here. And the surge protection circuit that the power supply line pair 1, 2 lines and 3, 6 lines are connected and the PSE chip in the surge protection circuit that the power supply line pair 4, 5 lines and 7, 8 is connected can be same PSE chip, and two surge protection circuits can share explosion protection ware RV2, explosion protection ware RV3 and electrolytic capacitor C1 and TVS pipe D4 in the differential mode protection circuit, wherein, two surge protection circuits share explosion protection ware RV2 through connecting FL department shown in figure 2C together, and then not only can practice thrift the hardware cost, still can improve the integrated level of surge protection circuit, practice thrift PCB board space.

It should be noted that the surge protection circuit provided by the embodiment of the present application is applicable to different standards. The voltage of the switching power supply 10g is different for different standards. For example, for the ieee802.3at standard, the voltage of the switching power supply 10g may be 50V to 57V; for the ieee802.3af standard, the voltage of the switching power supply 10g may be 44V-57V. Alternatively, the voltage of the switching power supply 10g may be 50V to 57V for both the ieee802.3at standard and the ieee802.3af standard, and a switching power supply having a voltage of 54V may be selected.

It is worth also saying that the surge protection circuit provided by the embodiment of the present application can select different circuit device parameters according to the POE system application environment and the level of lightning surge energy resistance, and can realize the protection of the POE power supply port with lower cost, for example, an RJ45 connector. Meanwhile, due to the fact that appropriate device parameters are selected, PSE equipment with different anti-interference capabilities can be effectively protected. The RJ45 connector is suitable for use with an 8-wire model connector, but is not limited thereto.

Based on the surge protection circuit of above-mentioned embodiment, when the surge waveform is 10/700 mus, impedance is 40 omega and voltage amplitude is the surge of 8kV and is used in the POE system, the surge protection circuit that this application embodiment provided can carry out the surge protection to the POE system, and can make the POE system not fall the power.

Fig. 3 is a schematic structural diagram of a POE system according to an embodiment of the present application. As shown in fig. 3, the POE system includes: POE power supply device 30a (PSE device 30a), POE powered device 30b (PD device 30b), switching power supply 30c, and surge protection circuit 30 d. As shown in the dashed box in fig. 3, the surge protection circuit 30d includes: a first lightning protection circuit 10a, a second lightning protection circuit 10b, a first switching circuit 10c, a gating circuit 10d and a differential mode protection circuit 10 e.

The gating circuit 10d is connected between the voltage output terminal U of the PSE device 30a in the POE system and the ground terminal G; wherein, the voltage output end U of the PSE equipment 30a is directly connected with the negative phase power supply end P-directly; the ground G of the PSE device 30a is electrically connected to the negative pole E-of the switching power supply 30c of the POE system.

The differential mode protection circuit 10E is connected between the positive phase power supply end P + and the negative electrode E-of the switch power supply 30 c; and the positive electrode E + of the switching power supply 10g is directly connected with the positive phase power supply end P +.

The PD device 30b is connected between the positive phase power supply terminal P + and the negative phase power supply terminal P-.

Based on the POE system shown in fig. 3, the voltage output terminal U of the PSE device 30a performs power supply control on the PD device 30 b.

The following is an example of a POE system in which the PSE device 30a and the PD device 30b are connected by an RJ45 connector and are connected by the ieee802.3af standard, and the specific operation of the POE system is described. The work engineering is roughly as follows: firstly, the PSE device 30a outputs a small voltage at the voltage output terminal U until it detects that the connection of the cable terminal is a power receiving terminal device supporting the ieee802.3af standard; secondly, after the PSE device 30a detects the PD device 30b, the PSE device 30a classifies the PD device 30b and evaluates the power consumption required by this PD device 30 b; then, during a start-up period of a configurable time (typically less than 15 μ s), the PSE device 30a starts to supply power from a low voltage to the PD device 30b until a voltage value equal to the switching power supply 30c is reached; then, the PSE device 30a provides stable and reliable dc power to the PD device 30b, and the voltage value of the dc power is the maximum voltage of the switching power supply 30c, which satisfies that the PD device 30b does not exceed the power consumption of 15.4W, where the maximum power consumption of the PD device 30b is specified by the relevant standard, that is, the ieee802.3af standard specifies that the maximum power consumption of the PD device of the POE system is 15.4W; finally, if the PD device 30b is disconnected from the network, the PSE device 30a will quickly (typically within 300-400 ms) stop supplying power to the PD device 30b, and repeat the detection process to detect whether the terminal of the cable is connected to the PD device.

For the surge protection circuit 30d shown in fig. 3, the operation principle and the corresponding circuit structure thereof can refer to the description of fig. 1, fig. 2a and fig. 2b related to the above embodiments, and are not described again here.

The POE system that this embodiment provided not only can realize the power supply control to PD equipment, can carry out the surge protection to POE system moreover. When positive voltage surge acts on the POE system, positive voltage surge current flows to the ground from a positive phase power supply end of the POE system through the first lightning protection circuit; the current flows to the ground from a negative phase power supply end of the POE system through the first switch circuit and the first lightning protection circuit; thereby bleeding off the positive surge energy. When the negative voltage surge is applied to the POE system, the surge protection circuit can flow the negative voltage surge current from the ground to the negative phase power supply end of the POE system through the second lightning protection circuit; negative-pressure surge current can directly flow to the positive-phase power supply end of the POE system from the ground through a large part of the first anti-detonator, and the residual negative-pressure surge current passing through the first anti-detonator flows to the negative-phase power supply end through the differential mode protection circuit and the gating circuit, so that negative-pressure surge energy is released. Like this, this protection circuit not only can discharge the surge energy, realizes the protection to POE power supply unit, still can make negative pressure surge current can not flow to switching power supply, and then can avoid surge current to lead to switching power supply's voltage to fall to can reduce the probability that POE system falls electricity.

It should be noted that, the descriptions of "first", "second", etc. in this document are used for distinguishing different messages, devices, modules, devices, etc., and do not represent a sequential order, nor limit the types of "first" and "second" to be different.

It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.

The above description is only an example of the present application and is not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. The utility model provides a surge protection circuit, is applicable to ethernet power over Ethernet POE system, a serial communication port, include: the lightning protection circuit comprises a first lightning protection circuit, a second lightning protection circuit, a first switch circuit, a gating circuit and a differential mode protection circuit; wherein,

2. The surge protection circuit of claim 1, wherein the first lightning protection circuit is a detonator RV 3.

3. The surge protection circuit of claim 2, wherein the detonator RV3 is a varistor, a gas discharge tube, a bidirectional transient suppression diode TVS, or a semiconductor discharge tube TSS.

4. The surge protection circuit of claim 1, wherein the second lightning protection circuit comprises: a second switching circuit and a detonator RV 2; the second switching circuit is connected between the negative phase power supply end and the anti-detonator RV 2; and one end of the detonator RV2, which is not connected with the second switching circuit, is grounded.

5. The surge protection circuit of claim 4, wherein the second switching circuit comprises: a diode D2; the cathode of the diode D2 is electrically connected with the negative phase power supply end; the anode of the diode D2 is electrically connected with the anti-detonator RV 2.

6. The surge protection circuit of claim 4, wherein the detonator RV2 is a piezoresistor, a gas discharge tube, a bidirectional TVS tube or a TSS tube.

7. The surge protection circuit of claim 1, wherein the first switching circuit comprises: a diode D1; the anode of the diode D1 is electrically connected with the negative phase power supply end; the cathode of the diode D2 is electrically connected with the positive phase power supply end.

8. The surge protection circuit of claim 1, wherein the gating circuit comprises: a diode D3; the cathode of the diode D3 is electrically connected with the voltage output end; the anode of the diode D3 is electrically connected to the ground terminal.

9. The surge protection circuit of claim 1, wherein the differential mode protection circuit comprises: an electrolytic capacitor C1 and a TVS tube D4 connected in parallel with the electrolytic capacitor C1; the positive electrode of the electrolytic capacitor C1 and one end of the TVS tube D4 are respectively and electrically connected with the positive phase power supply end; the negative electrode of the electrolytic capacitor C1 and the other end of the TVS tube D4 are respectively electrically connected with the negative electrode of the switching power supply.

10. The surge protection circuit according to any of claims 1-9, further comprising: an anti-detonator RV 1; one end of the detonator RV1 is electrically connected with a center tap of an isolation transformer connected with two groups of non-power supply wire pairs in the RJ45 connector, and the other end of the detonator RV1 is grounded; the center taps of the isolation transformer connected by the two groups of power supply wire pairs in the RJ45 connector are respectively connected to the positive phase power supply end and the negative phase power supply end.

11. A POE system, comprising: POE power sourcing equipment, POE powered device, switching power supply and the surge protection circuit of any of claims 1-10.