Network interface circuit and video surveillance device

Abstract

The embodiment of the application provides a network interface circuit and a video monitoring device, wherein the network interface circuit comprises a connector configured to be connected with an external device through a network cable; a network transformer comprising a first side and a second side, the first side being connected with the connector, and the second side being connected with an internal component; the network transformer being configured to isolate the external device and the internal component; the internal component referring to a component inside a device in which the network interface circuit is located; and a first protection module having one end connected with a center tap of the second side and the other end grounded, and being configured to absorb common-mode surges. Through the application, the technical problem that an abnormal current loop formed by failure of a voltage-dependent resistor burns a device and a potential fire risk exist in the related art are solved.

Description

Technical Field

[0001] This application relates to the field of electromagnetic interference protection technology, and more specifically, to a network interface circuit and a video surveillance device. Background Technology

[0002] In existing network video surveillance systems, when non-PoE devices (such as NVRs) are connected to PoE switches, if protective devices such as varistors fail, and the 48V power ground of the PoE switch is connected to the chassis, while the non-PoE device and the chassis ground of the switch are connected through the cabinet or ground wire, an abnormal current loop may be formed, causing the network cable, transformer, PCB board, etc. to burn out, resulting in equipment damage or even fire risk. Utility Model Content

[0003] This application provides a network interface circuit and a video surveillance device to at least solve the technical problems in the related art where abnormal current loops caused by varistor failure burn out equipment and pose a potential fire risk.

[0004] According to one aspect of the embodiments of this application, a network interface circuit is provided, comprising: a connector for connecting to an external device via a network cable; a network transformer including a first side and a second side, the first side being connected to the connector and the second side being connected to an internal component; the network transformer being used to isolate the external device and the internal component; the internal component referring to a component inside the device in which the network interface circuit is located; and a first protection module, one end of which is connected to the center tap of the second side and the other end of which is grounded, for absorbing common-mode surges.

[0005] According to another aspect of the embodiments of this application, a video surveillance device is also provided, comprising: a network camera for acquiring video signals; a power supply switch including a first Power over Ethernet (PoE) interface and a second PoE interface; the first PoE interface being connected to the network camera; the power supply switch being used to transmit power to the network camera through the first PoE interface, receive the video signals, and transmit the video signals to the second PoE interface; a network hard disk recorder including internal components and a network interface circuit; the internal components being connected to the network interface circuit, and the network interface circuit being connected to the second PoE interface; the internal components being used to communicate with the network camera through the network interface circuit; the network interface circuit being used to transmit the video signals to the internal components and absorb common-mode surges on the network cable; and the network hard disk recorder being used to store the video signals.

[0006] According to another aspect of the embodiments of this application, a computer-readable storage medium is also provided, wherein a computer program is stored therein, wherein the computer program is configured to perform the steps in any of the above method embodiments when executed by a processor.

[0007] According to another aspect of the embodiments of this application, a computer program product or computer program is provided, the computer program product or computer program including computer instructions stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions, causing the computer device to perform the steps in any of the method embodiments described above.

[0008] According to another aspect of the embodiments of this application, an electronic device is also provided, including a memory and a processor, wherein the memory stores a computer program, and the processor is configured to perform the steps of any of the above method embodiments through the computer program.

[0009] Through this application, the first side of the network transformer is connected to the connector, and the second side is connected to the internal components of the device where the network interface circuit is located. In the connection between non-POE devices and POE switches, if the varistor or other protective devices fail and short-circuit, the network transformer can ensure that within a certain voltage range, DC power cannot be transmitted from the first side to the second side, i.e., from the connector to the internal components, effectively blocking abnormal power supply paths and preventing the internal circuit from being directly impacted by external DC power. Secondly, one end of the first protection module is connected to the center tap of the second side of the network transformer, and the other end is grounded. On the one hand, it makes full use of the DC blocking characteristics of the transformer, so that even in the case of abnormal short circuit of the varistor of the non-POE device, it can effectively prevent POE current backflow, avoiding equipment burnout and potential fire risks. On the other hand, even if the static electricity and common-mode surge coupled to the network cable may trip to the other side through the network transformer due to the limited isolation of the network transformer, the DC blocking characteristics of the first protection module can cut off the effective current loop between the DC power supply and the internal components, thereby preventing the network cable, transformer, PCB board and other components inside the device from being damaged by overheating or overcurrent. Attached Figure Description

[0010] Figure 1 This is a structural diagram of a video surveillance device according to an embodiment of this application;

[0011] Figure 2 A simplified diagram of an ideal PoE power supply principle provided for embodiments of this application;

[0012] Figure 3A simplified diagram illustrating the connection between a practical PoE switch and a non-PoE NVR, provided for embodiments of this application;

[0013] Figure 4 A schematic diagram of an abnormal current loop connecting a PoE switch and a non-PoE NVR is provided in an embodiment of this application.

[0014] Figure 5 This is a schematic diagram of the structure of a network interface circuit provided in an embodiment of this application;

[0015] Figure 6 A structural diagram of another network interface circuit provided in an embodiment of this application;

[0016] Figure 7 A circuit diagram of a network interface circuit with a communication standard of 10BASE-T / 100BASE-TX provided for embodiments of this application;

[0017] Figure 8 A circuit diagram of a network interface circuit with a communication standard of 1000BASE-T provided for an embodiment of this application;

[0018] Figure 9 This is a schematic diagram illustrating the connection between a power supply switch and a network interface circuit, provided in an embodiment of this application. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0020] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0021] Video surveillance equipment such as network video recorders (NVRs) and network cameras (IPCs) all have Ethernet interfaces. Figure 1 As shown, the NVR is a non-PoE NVR, and the IPC is a PoE IPC. Multiple network cameras are powered through a PoE switch, and the video signals captured by the multiple network cameras are transmitted to the NVR for storage and preview via the power supply switch (PoE switch). Figure 1 As can be seen, the NVR's regular network port (non-POE port) is connected to the switch's POE port.

[0022] PoE (Power Over Ethernet) refers to a technology that, without modifying the existing Ethernet Cat.5 cabling infrastructure, can simultaneously transmit data signals to IP-based terminals (such as IP phones, wireless LAN access points, network cameras, etc.) and provide DC power to these devices. PoE power supply typically involves: detection → power receiving device (PD) classification → power supply → power off. The power supply equipment (Power Sourcing Equipment, PSE, such as a PoE switch) will only supply power normally if it detects that the cable termination is connected to a power receiving device that supports the IEEE 802.3af standard (such as a PoE network camera). If the cable termination is connected to a regular device (such as a regular network port NVR), it will not supply power.

[0023] Figure 2 This application provides a simplified diagram of an ideal PoE power supply principle. After the PSE controller identifies a standard powered device, it controls the MOS (Metal-Oxide Semiconductor) transistor M1 to turn on. The current path is as follows: Figure 2 As shown, the 48V power supply returns from the two twisted pairs of wires, thus powering the standard powered device (PD). Similarly, if the PSE controller does not recognize a standard powered device (such as a regular network NVR), the MOSFET M1 remains in the off state, failing to form a current loop, and therefore does not supply power to non-standard powered devices (PDs).

[0024] Figure 3This application provides a simplified diagram of a practical PoE switch and a non-PoE NVR connection. The PoE switch's 48V power supply is non-isolated, meaning the 48V power ground is connected to the chassis. The non-PoE NVR's transformer center plug is connected to a varistor (RV100, DC operating voltage 65V), resistors, capacitors, etc., for surge protection. Under normal circumstances, since the PoE switch is connected to a non-PoE device, the PoE switch will not supply power externally; that is, MOSFET M2 will not be turned on, and no abnormal current loop will be formed.

[0025] However, in practical applications, NVR network ports often become severely burnt. After on-site investigation and analysis, the cause of the NVR network port burnt was determined to be:

[0026] 1) The NVR is connected to the PoE switch, and the ground of the switch's 48V PoE power supply is connected to the chassis (non-isolated).

[0027] 2) The varistor of the NVR fails due to lightning strikes or other reasons, and usually presents a short circuit state;

[0028] 3) The NVR and the switch are located in the same server room and in the same rack. The ground (chassis) of the two devices are connected together through the rack, ground wire, etc.

[0029] Figure 4 A schematic diagram of an abnormal current loop connecting a PoE switch and a non-PoE NVR is provided as an embodiment of this application, as shown below. Figure 4 As shown, when the above conditions are met, a current loop can be formed between the PoE switch and the NVR, and the current path is as follows. Figure 4 As shown, current flows through the network port, network cable, transformer, varistor (abnormal short circuit), chassis ground, etc. If the power supply of the PoE switch is relatively large, it will burn out the network cable, transformer, PCB (Printed Circuit Board) substrate, etc.

[0030] Therefore, to solve the above problems, this application provides a network interface circuit that connects the first protection module to the center tap on the side of the network transformer near the internal components. This not only absorbs common-mode surges but also utilizes the DC blocking characteristics of the transformer (within a certain voltage range) to avoid the risk of burning out the equipment when a non-POE NVR is connected to a POE switch.

[0031] Figure 5 This is a schematic diagram of a network interface circuit provided in an embodiment of this application, such as... Figure 5 As shown, the network interface circuit includes a connector, a network transformer, and a first protection module.

[0032] Connectors are used to connect to external devices via network cables. A connector is a standard network interface connector used to establish a physical connection with external devices such as switches, routers, or other network cameras via twisted-pair (network cable) cables to enable data transmission. For example, a connector can be an RJ45 interface.

[0033] A network transformer includes a first side and a second side. The first side is connected to a connector, and the second side is connected to internal components. The network transformer is used to isolate external devices and internal components. In this embodiment, the network transformer is used for signal conversion and electrical isolation. The first side is directly connected to a connector (such as an RJ45 interface) to receive data signals and possible power (e.g., in a PoE environment) from an external network. The second side is connected to the internal components of the device where the network interface circuit is located, providing isolated signals and power to these components. The core function of the network transformer is that it can prevent DC or low-frequency signals from passing through, thereby protecting internal components from external power fluctuations, while also converting signals to match the needs of the internal components. Internal components refer to components within the device where the network interface circuit is located, such as network control chips and other auxiliary circuit modules.

[0034] Because the isolation of network transformers is limited (typically around 1KV), static electricity and common-mode surges coupled to the network cable can trip through the network transformer to the other side, damaging internal components such as network chips. Therefore, in this embodiment, the first protection module, with one end connected to the center tap of the second side and the other end grounded, is used to absorb common-mode surges. The main function of the first protection module is to absorb and protect the network interface from static electricity, common-mode surges, and other high-voltage transient impacts, ensuring that even under abnormal voltage conditions, the network transformer and its downstream network control chips and other internal components are protected from damage. For example, the first protection module can use one or more sets of varistor (Resistance Value, RV) as the main protection element. Varistors can quickly conduct when the voltage exceeds a threshold, discharging the excessive voltage to ground and protecting the downstream circuitry. For example, the first protection module can also use a TVS diode (Transient Voltage Suppressor), which can suppress voltage transients bidirectionally and respond to overvoltages in both positive and negative directions. Similar to varistors, TVS diodes can provide a fast protection path when overvoltage occurs. For example, the first protection module can also use protective devices such as semiconductor discharge tubes and gas discharge tubes. Semiconductor discharge tubes discharge rapidly under overvoltage conditions, reducing voltage peaks and protecting the circuit from impact.

[0035] In some embodiments, if the network interface circuit described above is applied to a non-PoE device (such as an NVR), as can be seen from the above description, in the connection between the non-PoE device and the PoE switch, the PoE switch may have a 48V DC power supply. If the varistor or other protective devices fail and short-circuit, an abnormal DC current loop will usually be formed in this situation. However, since the center tap of the network transformer and the first protection module both have DC blocking characteristics, even if the protective devices fail, the 48V DC power supply cannot form an effective current loop, thereby preventing damage to the internal components of the device, such as network cables, transformers, and PCB substrates, from overheating or overcurrent.

[0036] In this embodiment, the first side of the network transformer is connected to the connector, and the second side is connected to the internal components of the device where the network interface circuit is located. In the connection between a non-POE device and a POE switch, if the varistor or other protective devices fail and short-circuit, the network transformer can ensure that within a certain voltage range, DC power cannot be transmitted from the first side to the second side, i.e., from the connector to the internal components, effectively blocking abnormal power supply paths and preventing the internal circuit from being directly impacted by external DC power. Secondly, one end of the first protection module is connected to the center tap of the second side of the network transformer, and the other end is grounded. On the one hand, it makes full use of the DC blocking characteristics of the transformer, so that even if the varistor of the non-POE device is abnormally short-circuited, it can effectively prevent POE current backflow, avoiding equipment burnout and potential fire risks. On the other hand, even if the static electricity and common-mode surge coupled to the network cable may trip to the other side through the network transformer due to the limited isolation of the network transformer, the DC blocking characteristics of the first protection module can cut off the effective current loop between the DC power supply and the internal components, thereby preventing the network cable, transformer, PCB board and other components inside the device from being damaged by overheating or overcurrent.

[0037] In one exemplary embodiment, such as Figure 5 As shown, the network interface circuit also includes a second protection module, one end of which is connected to the center tap on the first side and the idle interface of the connector, and the other end is grounded. This module is used to absorb static electricity and common-mode surges coupled to the network cable. Specifically, the second protection module refers to a protection unit located in the network interface circuit, connected between the center tap on the first side of the network transformer and the idle interface of the connector (such as an RJ45), and ultimately connected to ground. Its design goal is to absorb and mitigate static electricity and common-mode surges coupled to the network cable from the outside, protecting the network circuit from damage caused by such transient voltages. The structure of the second protection module includes, but is not limited to, simple passive components such as capacitors, resistors, and inductors, or any combination thereof.

[0038] In this embodiment, the second protection module is selectively connected to the center tap and the idle interface of the connector on the first side of the network transformer, rather than directly to the network chip or power line pair. This location selection makes full use of the isolation characteristics of the network transformer, effectively blocking the loop path of abnormal current. Especially when non-POE devices are mistakenly connected to the POE power supply network, it avoids the problem of internal network cables, transformers, and PCB boards being burned due to the failure of varistor when non-POE devices are connected to POE switches, thus reducing equipment damage and potential fire risks.

[0039] In one exemplary embodiment, such as Figure 5 As shown, the network transformer includes multiple transformers, wherein the first side of the network transformer includes the first side coils of multiple transformers, the second side includes the second side coils of multiple transformers, one end of the first protection module is connected to the center tap of the second side coil of each transformer; the second side coil of each of the multiple transformers is connected to two ports of the internal component.

[0040] like Figure 5 As shown, the network interface circuit also includes multiple third protection modules, each corresponding to a transformer. Each third protection module is connected in parallel across the two ends of the second-side coil of its corresponding transformer. Each transformer is equipped with one corresponding third protection module, ensuring that each data channel receives independent and timely protection against sudden differential-mode surges, thus guaranteeing the robustness and reliability of the network interface. The third protection module is a newly added protection unit in the network interface circuit, used for differential-mode surge protection to ensure the integrity of data signals and circuit safety. Each third protection module corresponds to one of the second-side coils of the network transformer; specifically, it is connected in parallel across the two ends of the transformer's second-side coil and directly connected to the data signal port of the internal components. The introduction of the third protection module fills the gap in traditional protection strategies for handling differential-mode interference. Through its internal protective elements (such as TVS diodes and diodes), it quickly responds to and absorbs differential-mode surges, preventing transient voltages on signal lines from damaging the network chip and data circuits. For example, the third protection module can include a parallel structure of TVS diodes, resistors, and other basic protective elements, or it can include a self-resetting fuse.

[0041] In this embodiment, the network transformer consists of multiple independent transformers, with the first and second coils of each transformer designed separately, increasing the protection level of the network interface. By connecting the first protection module to the center tap of the second coil of each transformer, and connecting the third protection module in parallel across the second coil of each transformer, a dual protection system is formed. This effectively avoids damage to the equipment from non-isolated PoE power supplies under abnormal conditions. Even if the varistor fails, it will not cause the network cable, transformer, or PCB board to burn out, thereby reducing equipment failure and maintenance costs, and lowering the risk of fire. The third protection module is directly connected in parallel with the second coil of the transformer and is specifically designed to protect against differential-mode surges. Each transformer is equipped with a corresponding third protection module, ensuring the integrity of the data signal. Even in complex electromagnetic environments, each data channel can obtain independent and timely differential-mode surge protection, preventing high-energy differential-mode surges from damaging the network chip, ensuring the continuity of data transmission and the long-term operation of the equipment.

[0042] In one exemplary embodiment, such as Figure 5 As shown, the connector includes an indicator light module, which is connected to an internal component and is used to display the status of the network interface circuit according to the control of the internal component.

[0043] like Figure 5 As shown, the network interface circuit also includes a fourth protection module. This fourth protection module is connected at one end to the indicator light module and grounded at the other end, providing electrostatic discharge (ESD) protection for the indicator light module. Specifically, the fourth protection module acts as an ESD protection unit for the indicator light module within the network interface circuit. One end is directly connected to the indicator light module, and the other end is connected to system ground. The function of the fourth protection module is to quickly dissipate electrostatic energy when the indicator light module is subjected to an ESD impact, protecting the indicator light and other related circuits from damage. For example, the fourth protection module may include an ESD protection diode array or an ESD protection capacitor. For instance, the indicator light module may include two indicator lights, one displaying green and the other yellow. Different colors represent different states of the network interface circuit. These two indicator lights are controlled by internal components. Correspondingly, the fourth protection module may use two capacitors, one end of which is connected to the positive terminal of each indicator light, and the other end of each capacitor is grounded, thereby quickly dissipating electrostatic energy when the indicator light module is subjected to an ESD impact.

[0044] In this embodiment, the indicator light module, as an important component of the network interface circuit, is used to intuitively display the device status. The electrostatic discharge protection function of the fourth protection module ensures that the indicator light can still function normally in a high electrostatic environment and is not damaged by accidental electrostatic shocks.

[0045] In one exemplary embodiment, Figure 6 A structural diagram of another network interface circuit provided in an embodiment of this application is shown below. Figure 6 As shown, the first protection module includes a first surge protector, one end of which is connected to the center tap on the second side, and the other end is grounded, for absorbing common-mode surges. The first surge protector, as a key protective component in the first protection module of the network interface circuit, has one end connected to the center tap on the second side of the network transformer and the other end connected to system ground. Its main function is to absorb and discharge common-mode surges on the network lines, protecting downstream circuits from surge damage. For example, the first surge protector may include any one of a varistor, a TVS diode, a semiconductor discharge tube, or a gas discharge tube.

[0046] In one exemplary embodiment, such as Figure 6 As shown, the first protection module also includes a first common-mode suppression capacitor, connected in parallel across the surge protector, used to suppress electromagnetic radiation conduction. Specifically, the first common-mode suppression capacitor, in the first protection module of the network interface circuit, is a capacitor used to suppress common-mode signals. It is typically connected in parallel across the first surge protector to reduce electromagnetic interference caused by common-mode signals (such as EMC radiation), ensuring the clarity and integrity of data transmission. For example, the first common-mode suppression capacitor can employ a high-frequency suppression capacitor, a high-voltage withstand capacitor, or other similar structures.

[0047] In this embodiment, the first surge protector directs the common-mode surge current to ground, effectively preventing damage to downstream circuits, especially data transmission circuits, and ensuring data transmission stability. The first common-mode suppression capacitor suppresses common-mode signals, reducing conducted interference from EMC radiation to the network interface circuit, maintaining data transmission quality, and preventing signal distortion and increased bit error rate. The first common-mode suppression capacitor works in conjunction with the first surge protector, not only absorbing surges but also suppressing common-mode interference that may be generated during surges, further enhancing the protection capability of the network interface circuit.

[0048] In one exemplary embodiment, such as Figure 6 As shown, the second protection module includes: a second surge protector and a second common-mode suppression capacitor; wherein, one end of the second surge protector is connected to the center tap and the idle interface of the connector on the first side respectively, and the other end is grounded through the second common-mode suppression capacitor, which is used to absorb static electricity and common-mode surges coupled to the network cable; the second common-mode suppression capacitor is used to suppress electromagnetic radiation conduction.

[0049] In the second protection module of the network interface circuit, the second surge protector serves as a critical protective component. One end of it is connected to the center tap on the first side of the network transformer and the idle interface of the connector, while the other end is grounded through the second common-mode suppression capacitor. Its main function is to absorb static electricity and common-mode surges coupled to the network cable, protecting the circuit from overvoltage impacts. The second common-mode suppression capacitor, in the second protection module, is connected in series with the second surge protector and grounded. Its main function is to further suppress electromagnetic radiation conduction, reduce common-mode signal interference to the circuit, and enhance system electromagnetic compatibility. For example, the second surge protector can be a varistor, TVS diode, semiconductor, or gas discharge tube, etc. The second common-mode suppression capacitor should be a capacitor type with good high-frequency performance, such as X7R or multilayer ceramic capacitor (MLCC).

[0050] In this embodiment, the second surge protector absorbs static electricity and common-mode surges coupled to the network cable, preventing surges from directly impacting the network chip and ensuring the stability and security of data transmission and reception. The second common-mode suppression capacitor effectively suppresses EMC conducted noise, especially common-mode radiated noise. In abnormal situations where non-PoE devices are connected to PoE switches, the combined use of the second surge protector and the second common-mode suppression capacitor prevents non-isolated PoE power current from flowing back through the network interface, reducing the risk of device burnout.

[0051] In one exemplary embodiment, such as Figure 6 As shown, each third protection module includes: a transient voltage suppression device connected in parallel across the two ends of the second-side coil of the corresponding transformer to absorb differential-mode surges coupled to the network cable; a first protection component, one end of which is connected to one end of the second-side coil of the corresponding transformer and the other end of which is connected to one port of the internal component to limit the current entering the internal component; and a second protection component, one end of which is connected to the other end of the second-side coil of the corresponding transformer and the other end of which is connected to another port of the internal component to limit the current entering the internal component.

[0052] In the third protection module of the network interface circuit, the transient voltage suppression device is a protective element connected in parallel across the second winding of the transformer. It is used to quickly absorb and dissipate differential-mode surges coupled to the network cable, protecting downstream circuits from instantaneous high voltage or current spikes. For example, transient voltage suppression devices typically use TVS diodes. TVS diodes have low clamping voltage and fast response characteristics, effectively limiting surge voltage and guiding surge current to ground.

[0053] The first protection component is connected at one end to one end of the second coil of the corresponding transformer and at the other end to a data port of an internal component. Its main function is to limit any abnormal current from entering the internal component, preventing damage caused by overload or short circuit. The second protection component is similar to the first protection component, but it is connected to the other end of the second coil of the transformer and another data port of the internal component, together forming a two-port current limit for the internal component, ensuring the safety of the data transmission circuit. For example, the first and second protection components can be current-limiting resistors to limit the current flowing into the internal component, preventing excessive current from damaging the internal circuit. Under high power or high frequency conditions, low-resistance, high-power rated resistors may be used to withstand greater current. For example, the first and second protection components may also include a fuse and a thermistor, respectively. The fuse melts when the current exceeds a predetermined threshold, cutting off the circuit; the thermistor increases its resistance as the temperature rises, thereby limiting the current. Both effectively prevent overload or thermal runaway.

[0054] In this embodiment, the application of transient voltage suppression devices (such as TVS diodes) in the third protection module effectively absorbs differential-mode surges, prevents surge current from damaging the data channel, and ensures the continuity and integrity of data transmission. The presence of the first and second protection components limits the current flowing into the internal components under abnormal conditions, avoiding equipment failures and safety hazards caused by overload, and providing a reliable protective barrier for the internal electronic components. Through the synergistic effect of multiple protection mechanisms, the network interface circuit can better cope with complex network environments and sudden electrical events, reducing the probability of equipment damage and extending the service life of the equipment.

[0055] In one exemplary embodiment, Figure 7 A circuit diagram of a network interface circuit with a communication standard of 10BASE-T / 100BASE-TX is provided for embodiments of this application, as shown below. Figure 7 As shown, the first surge protector includes a varistor RV1, and the first common-mode suppression capacitor includes a first capacitor C1 and a second capacitor C2. One end of the varistor RV1 is connected to the center tap on the second side, and the other end of the varistor RV1 is grounded. The first capacitor C1 and the second capacitor C2 are connected in parallel and then in parallel across the varistor RV1. The varistor RV1 can absorb static electricity and common-mode surges; the first capacitor C1 and the second capacitor C2 can suppress EMC radiation and conduction, etc.

[0056] In this embodiment, the varistor RV1 is connected to the center plug of the transformer near the network chip, which not only absorbs common-mode surges but also utilizes the DC blocking characteristic of the transformer (within a certain voltage range) to avoid the risk of equipment burnout when a non-POE NVR is connected to a POE switch. The first protection module uses a parallel connection of the first capacitor C1 and the second capacitor C2, which are then connected in parallel across the varistor RV1. This structure increases the circuit's ability to suppress EMC radiation and conduction, and improves the electromagnetic compatibility of the entire system.

[0057] In one exemplary embodiment, such as Figure 7 As shown, the second common-mode suppression capacitor includes a first resistor R1; the second surge protector includes a third capacitor C3; one end of the first resistor R1 is connected to the center tap on the first side and the unused pin of the connector, and the other end of the first resistor R1 is grounded through the third capacitor C3. Specifically, the left center plug of transformer T1 (near the RJ45 interface) and the unused pin of the RJ45 interface are connected to the first resistor R1. The first resistor R1 can absorb static electricity and common-mode surges coupled to the network cable; the third capacitor C3 has a withstand voltage higher than 2KV and can suppress EMC radiation and conduction, etc.

[0058] In this embodiment, the introduction of a first resistor R1 provides a safe path to absorb common-mode surges and electrostatic discharge coupled in through the network interface. Even when non-PoE devices are connected to a PoE switch, abnormal current generated by the non-isolated PoE power supply can be effectively absorbed, preventing damage to the network port, network transformer, and PCB board. The third capacitor C3 effectively suppresses EMC conducted noise, especially common-mode noise. By grounding it and connecting it in parallel with the first resistor R1, a highly efficient EMC protection network is formed, reducing the impact of external electromagnetic interference on the internal circuitry and ensuring the accuracy of data transmission. The combination of the first resistor R1 and the third capacitor C3, utilizing the high-frequency characteristics of C3 and the impedance characteristics of R1, avoids the formation of a continuous current loop. Even if the varistor fails, the PoE power supply current will not flow directly back to the device, reducing the risk of damage to the device due to current loops.

[0059] In one exemplary embodiment, such as Figure 7 As shown, the transient voltage suppression device includes a transient voltage suppression diode D1; the first protection component includes a second resistor R2; the second protection component includes a third resistor R3; the transient voltage suppression diode D1 is connected in parallel across the two ends of the second coil of the corresponding transformer; one end of the second resistor R2 is connected to one end of the second coil of the corresponding transformer, and the other end of the second resistor R2 is connected to one port of the internal component; one end of the third resistor R3 is connected to the other end of the second coil of the corresponding transformer, and the other end of the third resistor R3 is connected to another port of the internal component.

[0060] The transient voltage suppression diode D1 is directly connected in parallel across the second winding of the network transformer, enabling it to quickly respond to and absorb differential-mode surge voltages, protecting internal components (such as the network control chip) from instantaneous high voltage impacts. One end of each of the second resistor R2 and the third resistor R3 is connected to one end of the second winding of the transformer, while the other end is directly connected to the receive and transmit ports of the internal components (such as the network control chip). This design limits the inflow of abnormal current, preventing damage to the internal circuitry caused by overload or short circuit. Through the combined use of transient voltage suppression devices and current-limiting resistors, a multi-layered protection system covering voltage suppression and current limiting is constructed, effectively resisting complex electrical interference and ensuring the stability and reliability of the network interface circuit.

[0061] In one exemplary embodiment, such as Figure 7 As shown, the fourth protection module includes a fourth capacitor C4 and a fifth capacitor C5. The indicator module includes two indicator lights, one of which displays green and the other displays yellow. Different colors represent different states of the network interface circuit. These two indicator lights are controlled by internal components. Correspondingly, one end of the fourth capacitor C4 and the fifth capacitor C5 are connected to the positive terminals of the two indicator lights, and the other end is grounded, so as to quickly discharge electrostatic energy when the indicator module is subjected to electrostatic discharge impact.

[0062] In one exemplary embodiment, such as Figure 7 As shown, the network transformer includes two transformers, and correspondingly, the network interface circuit also includes two third protection modules. Figure 8 A circuit diagram of a network interface circuit with a communication standard of 1000BASE-T provided for embodiments of this application is shown below. Figure 8 As shown, the network transformer includes four transformers, and correspondingly, the network interface circuit also includes four third protection modules. Figure 8 The working principle of the network interface circuit is the same as that of the 10BASE-T / 100BASE-TX network interface circuit, and will not be repeated here. Figure 9 This application provides a schematic diagram of the connection between a power supply switch and a network interface circuit, as shown in the embodiment. Figure 9 The circuit shown is a simplified version. Figure 9 The third and fourth protection modules are not shown. Since the third capacitor C3 has the characteristic of blocking 48V DC, and the network transformer T1 also has the characteristic of blocking 48V DC, even if the varistor RV1 is abnormally short-circuited, a return path cannot be formed, which can avoid the network cable, transformer, and PCB board being burned, resulting in the equipment being unrepairable and scrapped, and the possible fire.

[0063] In this embodiment, the parallel configuration of transient voltage suppression diode D1 enables it to have an extremely fast response speed, dissipating differential-mode surge voltage within nanoseconds and ensuring that the internal circuitry is protected from high-voltage damage. The second resistor R2 and the third resistor R3 are directly connected to the ports of the internal components, enabling them to immediately function in the instant of a current surge, limiting current flow and preventing damage to the internal components due to overcurrent, while also protecting the integrity of the back-end circuitry.

[0064] According to another aspect of this application, this application also provides a video surveillance device, such as... Figure 1 As shown, the video surveillance equipment includes:

[0065] A webcam is used to capture video signals.

[0066] The power supply switch includes a first Power over Ethernet (PoE) interface and a second PoE interface; the first PoE interface is connected to the network camera; the power supply switch is used to transmit power to the network camera through the first PoE interface, receive video signals, and transmit the video signals to the second PoE interface.

[0067] A network video recorder includes internal components and a network interface circuit; the internal components are connected to the network interface circuit, which is connected to a second Ethernet power supply interface; the internal components are used to communicate with network cameras through the network interface circuit; the network interface circuit is used to transmit video signals to the internal components and absorb common-mode surges on the network cable; the network video recorder is used to store video signals.

[0068] Among them, such as Figure 1 As shown, the first Ethernet power supply interface of the power supply switch is the PoE port in the power supply switch that connects to the network camera, and the first Ethernet power supply interface of the power supply switch is the PoE port in the power supply switch that connects to the network video recorder. The network interface circuit adopts the network interface circuit in the above embodiment, and will not be described again here.

[0069] In this embodiment, the network interface circuit of the network hard disk recorder incorporates multi-layered protection measures (such as common-mode surge suppression, differential-mode surge absorption, and current limiting), which significantly enhances the device's resistance to electromagnetic interference and abnormal currents, ensuring stable operation of the device in various environments.

[0070] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the principles of this application should be included within the protection scope of this application.

Claims

1. A network interface circuit, characterized in that, include: Connectors are used to connect to external devices via network cables; A network transformer includes a first side and a second side, the first side being connected to the connector and the second side being connected to an internal component; the network transformer is used to isolate the external device and the internal component; the internal component refers to the component inside the device where the network interface circuit is located; The first protection module has one end connected to the center tap on the second side and the other end grounded, and is used to absorb common-mode surges.

2. The network interface circuit according to claim 1, characterized in that, The network interface circuit also includes: The second protection module has one end connected to the center tap on the first side and the idle interface of the connector, and the other end grounded, for absorbing static electricity and common-mode surges coupled to the network cable.

3. The network interface circuit according to claim 1, characterized in that, The network transformer includes multiple transformers, and the network interface circuit also includes multiple third protection modules, each corresponding one-to-one with one of the multiple transformers. The first side includes the first side coils of the plurality of transformers; the second side includes the second side coils of the plurality of transformers; the second side coils of each of the plurality of transformers are respectively connected to two ports of the internal component; one end of the first protection module is respectively connected to the center tap of the second side coil of each transformer; Each of the plurality of third protection modules is connected in parallel to both ends of the second side coil of the corresponding transformer.

4. The network interface circuit according to claim 1, characterized in that, The connector includes an indicator light module, and the network interface circuit further includes a fourth protection module, wherein... The indicator light module is connected to the internal component and is used to display the status of the network interface circuit according to the control of the internal component; The fourth protection module is connected to the indicator light module at one end and grounded at the other end, and is used to provide electrostatic discharge protection for the indicator light module.

5. The network interface circuit according to claim 1, characterized in that, The first protection module includes: The first surge protector has one end connected to the center tap on the second side and the other end grounded, and is used to absorb common-mode surges.

6. The network interface circuit according to claim 5, characterized in that, The first protection module also includes: The first common-mode suppression capacitor is connected in parallel across the surge protector to suppress electromagnetic radiation conduction.

7. The network interface circuit according to claim 2, characterized in that, The second protection module includes: a second surge protector and a second common-mode suppression capacitor; wherein, The second surge protector has one end connected to the center tap on the first side and the idle interface of the connector, and the other end grounded through the second common-mode suppression capacitor, for absorbing static electricity and common-mode surges coupled to the network cable; The second common-mode suppression capacitor is used to suppress electromagnetic radiation conduction.

8. The network interface circuit according to claim 3, characterized in that, Each of the third protection modules includes: a transient voltage suppression device; The transient voltage suppression device is connected in parallel across the two ends of the second coil of the corresponding transformer to absorb differential mode surges coupled to the network cable.

9. The network interface circuit according to claim 8, characterized in that, Each of the third protection modules also includes: The first protection component has one end connected to one end of the second side coil of the corresponding transformer, and the other end connected to a port of the internal component, for limiting the current entering the internal component; The second protection component has one end connected to the other end of the second side coil of the corresponding transformer, and the other end connected to another port of the internal component, for limiting the current entering the internal component.

10. The network interface circuit according to claim 6, characterized in that, The first surge protector includes a varistor RV1, and the first common-mode suppression capacitor includes a first capacitor C1 and a second capacitor C2; One end of the varistor RV1 is connected to the center tap on the second side, and the other end of the varistor RV1 is grounded; the first capacitor C1 and the second capacitor C2 are connected in parallel and then in parallel across the two ends of the varistor RV1.

11. The network interface circuit according to claim 7, characterized in that, The second common-mode suppression capacitor includes a first resistor R1; the second surge protector includes a third capacitor C3; One end of the first resistor R1 is connected to the center tap on the first side and the free interface of the connector, respectively, and the other end of the first resistor R1 is grounded through the third capacitor C3.

12. The network interface circuit according to claim 9, characterized in that, The transient voltage suppression device includes a transient voltage suppression diode D1; the first protection component includes a second resistor R2; the second protection component includes a third resistor R3; The transient voltage suppression diode D1 is connected in parallel across the two ends of the second coil of the corresponding transformer; one end of the second resistor R2 is connected to one end of the second coil of the corresponding transformer, and the other end of the second resistor R2 is connected to one port of the internal component; one end of the third resistor R3 is connected to the other end of the second coil of the corresponding transformer, and the other end of the third resistor R3 is connected to another port of the internal component.

13. A video surveillance device, characterized in that, include: Network cameras are used to capture video signals; A power supply switch, including a first Power over Ethernet interface and a second Power over Ethernet interface; The first Power over Ethernet (PoE) interface is connected to the network camera; the power switch is used to transmit power to the network camera through the first PoE interface, receive the video signal, and transmit the video signal to the second PoE interface; A network hard disk video recorder includes internal components and a network interface circuit; the internal components are connected to the network interface circuit, and the network interface circuit is connected to a second Power over Ethernet interface; the internal components are used to communicate with the network camera through the network interface circuit. The network interface circuit is used to transmit the video signal to the internal components and absorb common-mode surges on the network cable; the network hard disk recorder is used to store the video signal. The network interface circuit includes the network interface circuit according to any one of claims 1 to 12.

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