A surge protection circuit and a surge protector

Abstract

The application relates to a surge protection circuit and a surge protector, which comprise a first protection unit, an inductive network unit, a second protection unit and a matching impedance resistor. The second protection unit comprises a diode bridge circuit and a voltage-limited current discharge circuit connected with the diode bridge circuit. The first protection unit is used for discharging main surge energy, and the second protection unit is used for clamping the voltage at both ends of a line. In view of the problem that high-frequency signals are easily affected by transient diodes of the second protection unit, the application controls the junction capacitance in the circuit within a certain range through the topological structure of the diode bridge circuit, the junction capacitance and the inductive network form an LC resonant network, and resonance is generated under the expected signal frequency band; under the high-impact current resistance, the risk that the communication quality of the expected frequency band is affected by the parasitic capacitance is reduced.

Description

Technical Field

[0001] This application relates to the field of circuit protection technology, and in particular to a surge protection circuit and surge protector. Background Technology

[0002] A surge protector is an electronic device designed to protect data communication lines, control signal lines, and their downstream sensitive electronic equipment from transient overvoltage surges caused by lightning strikes, electrical switching operations, and other factors. With the rapid development of emerging industries such as wind power, photovoltaics, and energy storage, as well as 5G communication and the Industrial Internet of Things, a large number of electronic devices are deployed outdoors or in harsh industrial environments. This not only requires signal lines to have higher transmission rates but also exposes the equipment to higher energy levels of lightning surge threats.

[0003] Currently, to meet the transmission requirements of high-frequency signals such as Gigabit Ethernet and to minimize the parasitic capacitance introduced by protection circuits, dedicated low-capacitance electrostatic discharge protection devices are typically used, or the parallel capacitance in the signal path is controlled to be less than tens of pF. This ensures that the insertion loss and return loss of the signal meet high-frequency communication standards. For applications such as wind turbine blades and photovoltaic arrays exposed to direct lightning strike risk areas, line protection with a surge current of 500A (8 / 20μS, 1.2 / 50kA) is generally required. According to "Low-voltage surge protectors Part 21 GB / T18802.21", this requirement corresponds to Class C testing. With the continuous improvement of protection requirements, the application scope of signal lightning protection zones has now expanded to feeder protection in the LPZ0 zone. According to "Low-voltage surge protectors Part 22 GB / T18802.22", in this scenario, the stringent standard of Class D testing of 0.5-2.5kA (10 / 350μS) must be met. To meet the high energy discharge requirements of signal circuits, related technologies typically use gas discharge tubes as the main discharge unit to discharge most of the current. On this basis, to achieve rapid response and release to surges, high-current transient suppression diodes are connected in parallel to improve the circuit's response speed to surge currents.

[0004] If only low-capacitance devices are used, the energy withstand capability is very limited and cannot meet the requirements of Class D testing. If high-power TVS diodes or similar devices are used, they will introduce nF-level junction capacitance, causing significant attenuation or even filtering of the signal amplitude, resulting in reduced communication quality or communication interruption. The aforementioned technologies suffer from the drawback of being incompatible between low parasitic capacitance and high surge withstand capability. Utility Model Content

[0005] In order to reduce the parasitic capacitance of the circuit to high-frequency signals without reducing the surge withstand capability, this application provides a surge protection circuit and a surge protector.

[0006] This application provides a surge protection circuit that employs the following technical solution: A surge protection circuit includes: The first port is used for connection to external circuitry; The second port is used for connection to external circuitry; An inductor network unit is connected to the first port and the second port; The second protection unit, connected to the inductor network unit, includes a diode bridge circuit and a voltage-limiting current discharge circuit. The diode bridge circuit includes a first arm, a second arm, a third arm, a fourth arm, a first node, a second node, a third node, and a fourth node. The first node is connected to the inductor network unit, and the second node is also connected to the inductor network unit. The first end of the first arm is connected to the first node, and the second end of the first arm is connected to the third node. The first end of the second arm is connected to the second node, and the second end of the second arm is connected to the third node. The first end of the third arm is connected to the fourth node. The first end of the fourth arm is connected to the fourth node. The third node is connected to the voltage-limiting current discharge circuit, and the fourth node is also connected to the voltage-limiting current discharge circuit. The third port is connected to the second end of the third bridge arm; The fourth port is connected to the second end of the fourth bridge arm.

[0007] By employing the above technical solution, the equivalent capacitance of the circuit is controlled within the range of the diode junction capacitance by connecting the diode junction capacitance and the transient transistor junction capacitance in series. This significantly reduces the parasitic capacitance of the circuit to high-frequency signals without compromising surge withstand capability.

[0008] Optionally, the first bridge arm includes a first diode D1 and a third diode D3, with the anode of the first diode D1 connected to the first node, the cathode of the first diode D1 connected to the anode of the third diode D3, and the cathode of the third diode D3 connected to the third node; the second bridge arm includes a seventh diode D7 and a fifth diode D5, with the anode of the seventh diode D7 connected to the second node, the cathode of the seventh diode D7 connected to the anode of the fifth diode D5, and the cathode of the fifth diode D5 connected to the third node; the third bridge arm includes a second diode D2 and a fourth diode D4, with the cathode of the second diode D2 connected to the first node, the anode of the second diode D2 connected to the cathode of the fourth diode D4, and the anode of the fourth diode D4 connected to the fourth node; the fourth bridge arm includes an eighth diode D8 and a sixth diode D6, with the cathode of the eighth diode D8 connected to the second node, the anode of the eighth diode D8 connected to the cathode of the sixth diode D6, and the anode of the sixth diode D6 connected to the fourth node.

[0009] By adopting the above technical solution, the equivalent capacitance of the line is further reduced by using diodes in series in each bridge arm, and the equivalent capacitance value of the entire line is controlled to be close to the junction capacitance of a single diode; and the combination of four bridge arms provides positive and negative impact discharge channels for lightning current.

[0010] Optionally, the voltage-limiting current discharge circuit includes a first transient diode TVS1, a second transient diode TV2, and a third transient diode TVS3. The first terminal of the second transient diode TVS2 is connected to the third node, and the second terminal of the second transient diode TVS2 is connected to the fourth node. The first terminal of the first transient diode TV1 is connected to the third node, and the second terminal of the first transient diode TV1 is grounded. The first terminal of the third transient diode TVS3 is connected to the fourth node, and the second terminal of the third transient diode TVS3 is grounded.

[0011] By adopting the above technical solution, the combination of the first transient diode TVS1, the second transient diode TVS2 and the third transient diode TVS3 provides fast and low residual voltage clamping protection for differential mode surge and common mode surge after bridge circuit rectification, respectively, realizing refined and efficient discharge of the two surge modes, and further reducing the residual surge voltage at the output terminal.

[0012] Optionally, the inductor network unit includes a first inductor L1 and a second inductor L2; a first end of the first inductor L1 is connected to the first port, and a first end of the second inductor L2 is connected to the second port.

[0013] By adopting the above technical solution, by setting a first inductor L1 and a second inductor L2 at the input end, a suitable inductance value is selected by calculation using a formula, and an LC resonant circuit is formed by combining the diode with the equivalent capacitance, thereby achieving zero attenuation or signal amplification in the expected frequency band.

[0014] Optionally, it also includes a first protection unit connected to the first port and the second port, including a first gas discharge tube G1 and a second gas discharge tube G2.

[0015] By adopting the above technical solution, and by adding a first protection unit composed of a first gas discharge tube G1 and a second gas discharge tube G2 as a front-end coarse protection, the surge with high energy can be discharged, effectively sharing the pressure of the subsequent fine protection circuit, and further enhancing the overall circuit's ability to cope with high-level surges.

[0016] Optionally, it also includes a first resistor R1 and a second resistor R2, wherein the first resistor R1 is disposed between the inductor network and the first node, and the second resistor R2 is disposed between the inductor network and the second node; wherein the first resistor R1 and the second resistor R2 are both non-inductive wire-wound resistors.

[0017] By employing the above technical solution, the first resistor R1 and the second resistor R2 serve a decoupling function, coordinating the actions of the upstream and downstream protection units. During a surge, the instantaneous voltage drop across the first resistor R1 and the second resistor R2 helps ensure the preferential conduction of the upstream gas discharge tube, achieving orderly coordination of protection levels and preventing damage to downstream components due to uneven energy distribution.

[0018] Optionally, a matching impedance resistor RJ1 is also included, with a first end of the matching impedance resistor RJ1 connected to the third port and a second end of the matching impedance resistor RJ1 connected to the fourth port.

[0019] By employing the above technical solution and setting the matching impedance resistor RJ1, the impedance can be adjusted according to the impedance characteristics of the downstream load or transmission line, thereby achieving impedance matching between the output and the downstream circuit. This structure effectively improves the integrity of high-speed signal transmission, reduces the risk of signal attenuation caused by adding protection circuits, and ensures the reliability of the communication system.

[0020] Optionally, the matching impedance resistor RJ1 is a non-inductive resistor.

[0021] By adopting the above technical solution, and using a non-inductive resistor as the matching impedance resistor RJ1, the impedance is controlled within a certain range, ensuring good impedance matching characteristics over a wider frequency range.

[0022] On the other hand, this application also provides a surge protector, which adopts the following technical solution: A surge protector includes the surge protection circuit.

[0023] By adopting the above technical solution, the surge protection circuit is integrated into a separate protector product, which is convenient for installation and use, and provides a reliable and high-performance surge protection solution for various electronic devices.

[0024] In summary, this application includes at least one of the following beneficial technical effects: 1. By using a diode bridge combination, the diode junction capacitance and the transient transistor junction capacitance are connected in series, and the equivalent capacitance of the circuit is controlled at the level of the diode junction capacitance, which greatly reduces the impact of the equivalent capacitance of the line on signal transmission and creates a constant capacitance value for the LC resonant circuit. 2. By setting the matching impedance resistor RJ1, the impedance can be adjusted according to the impedance characteristics of the downstream load or transmission line, thereby achieving impedance matching between the output and the downstream circuit. This structure effectively improves the integrity of high-speed signal transmission, reduces the risk of signal attenuation caused by the addition of protection circuits, and ensures the reliability of the communication system; 3. By setting the first inductor L1 and the second inductor L2 to form an LC resonant circuit with the line equivalent capacitance, resonance is formed in the expected signal frequency band, ensuring the transmission of high-frequency signals. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the surge protection circuit module in the embodiments of this application.

[0026] Figure 2 This is a circuit diagram of the surge protection circuit in the embodiments of this application.

[0027] Figure 3 yes Figure 2 The equivalent circuit schematic diagram.

[0028] Explanation of reference numerals in the attached drawings: 11, First port; 12, Second port; 20, First protection unit; 30, Inductor network unit; 40, Second protection unit; 41, First node; 42, Second node; 43, Third node; 44, Fourth node; 51, Third port; 52, Fourth port. Detailed Implementation

[0029] The following is in conjunction with the appendix Figure 1 ~Attached Figure 3 This application will be described in further detail.

[0030] This application mainly reduces the equivalent capacitance of the line by using diodes in series in each bridge arm, controlling the equivalent capacitance of the entire line to be close to the junction capacitance of a single diode, and providing positive and negative impact discharge channels for lightning current through the combination of four bridge arms.

[0031] Example 1 This application discloses a surge protection circuit.

[0032] Reference Figure 1 The surge protection circuit includes a first protection unit 20, an inductor network unit 30, a second protection unit 40, and a matching impedance resistor RJ1. The output of the first protection unit 20 is connected to the input of the inductor network unit 30, the output of the inductor network unit 30 is connected to the input of the second protection unit 40, and the output of the second protection unit 40 is connected to the input of the matching impedance resistor RJ1. This connection method allows the circuit to initially dissipate surge energy through the first protection unit 20, then adjust the signal through the inductor network unit 30, further suppress and protect against the surge through the second protection unit 40, and finally achieve impedance matching through the matching impedance resistor RJ1, ensuring stable transmission of high-frequency signals.

[0033] Reference Figure 2 The first protection unit 20 includes a first gas discharge tube G1 and a second gas discharge tube G2. The first discharge tube G1 is a three-stage gas discharge tube with high surge resistance, capable of rapidly conducting when a surge occurs, diverting the surge current to the ground. The second discharge tube G2 is a two-stage gas discharge tube, which also functions to conduct and discharge current when a surge occurs. The first electrode of the first discharge tube G1 is connected to the first port 11, the second electrode of the first discharge tube G1 is connected to the second port 12, and the third electrode of the first discharge tube G1 is grounded.

[0034] Reference Figure 2 The inductor network unit 30 includes a first inductor L1 and a second inductor L2. The first end of the first inductor L1 is connected to the first electrode of the second gas discharge tube G2, and the second end of the second inductor L2 is connected to the second electrode of the second gas discharge tube G2. By calculating and selecting appropriate inductance values, when a high-frequency signal passes through, the first inductor L1 and the second inductor L2, together with the diode bridge circuit, form an LC resonant circuit with equivalent capacitance, achieving zero attenuation or signal amplification in the expected frequency band. This reduces the signal attenuation caused by the equivalent capacitance in the circuit.

[0035] Reference Figure 2The circuit consists of a first resistor R1 and a second resistor R2. The first resistor R1 is located between the inductor network and the first node, and the second resistor R2 is located between the inductor network and the second node. Both resistors R1 and R2 are non-inductive wire-wound resistors. Resistors R1 and R2 limit and decouple differential-mode surge currents, thus attenuating surge energy.

[0036] Reference Figure 2 The second protection unit 40 includes a diode bridge circuit and a voltage-limiting current discharge circuit; wherein, the diode bridge circuit has a first node 41, a second node 42, a third node 43 and a fourth node 44, the first node 41 and the second node 42 are respectively connected to the inductor network unit 30, and the third node 43 and the fourth node 44 are respectively connected to the voltage-limiting current discharge circuit.

[0037] The diode bridge circuit includes a first bridge arm, a second bridge arm, a third bridge arm, and a fourth bridge arm. The first bridge arm includes a first diode D1 and a third diode D3. The anode of the first diode D1 is connected to a first node 41, and the cathode of the first diode D1 is connected to the anode of the third diode D3. The cathode of the third diode D3 is connected to a third node 43. The second bridge arm includes a seventh diode D7 and a fifth diode D5. The anode of the seventh diode D7 is connected to a second node 42, and the cathode of the seventh diode D7 is connected to the anode of the fifth diode D5. The cathode of the fifth diode D5 is connected to a third node 43. The third bridge arm includes a second diode D2 and a fourth diode D4. The cathode of the second diode D2 is connected to a first node 41, and the anode of the second diode D2 is connected to the cathode of the fourth diode D4. The anode of the fourth diode D4 is connected to a fourth node 44. The fourth bridge arm includes an eighth diode D8 and a sixth diode D6. The cathode of the eighth diode D8 is connected to a second node 42, and the anode of the eighth diode D8 is connected to the cathode of the sixth diode D6. The anode of the sixth diode D6 is connected to a fourth node 44.

[0038] The voltage-limiting current discharge circuit includes a first transient diode TVS1, a second transient diode TV2, and a third transient diode TVS3. The first terminal of the second transient diode TVS2 is connected to the third node 43, and the second terminal of the second transient diode TVS2 is connected to the fourth node 44. The first terminal of the first transient diode TV1 is connected to the third node 43, and the second terminal of the first transient diode TV1 is grounded. The first terminal of the third transient diode TVS3 is connected to the fourth node 44, and the second terminal of the third transient diode TVS3 is grounded.

[0039] Reference Figure 2The first terminal of the matching impedance resistor RJ1 is connected to the third port 51, and the second terminal of the matching impedance resistor RJ1 is connected to the fourth port 52. The matching impedance resistor RJ1 can be a non-inductive resistor to reduce the influence of additional inductance on high-frequency signals. The resistance value of the matching impedance resistor RJ1 can be adjusted according to the input impedance of the back-end equipment to achieve impedance matching and effective signal transmission within a set frequency band.

[0040] The signal includes a first signal component and a second signal component. Under normal operating conditions without surge intrusion, the first signal component flows in from the first port 11. Both the first gas discharge tube G1 and the second gas discharge tube G2 are cut off. The first signal component flows sequentially through the first inductor L1, the first resistor R1, and the first node 41. The first diode D1, the second diode D2, the third diode D3, the fourth diode D4, the fifth diode D5, the sixth diode D6, the seventh diode D7, and the eighth diode D8 are all cut off, and the first signal component flows out from the third port 51. The second signal component flows in from the second port 12. The second signal component flows sequentially through the second inductor L2, the second resistor R2, and the second node 42, and then flows out from the fourth port 52. Since the first diode D1, the second diode D2, the third diode D3, the fourth diode D4, the fifth diode D5, the sixth diode D6, the seventh diode D7, and the eighth diode D8 are all cut off, forming an LC oscillation amplifier circuit through the equivalent capacitance of the first inductor L1, the second inductor L2, and the diode bridge circuit, further ensuring the transmission of the high-frequency signal.

[0041] During a common-mode surge, the common-mode surge current flows in from the first port 11 and the second port 12. The first discharge transistor G1 is turned on, providing a low-impedance bypass for the common-mode surge current and dissipating the surge energy. The residual common-mode surge current is divided into two parts: the first part of the residual common-mode surge current flows through the first inductor L1 and the first resistor R1, then flows into the first bridge arm through the first node 41, and finally is discharged through the first transient diode TVS1 through the third node 43; the second part of the residual common-mode surge current flows through the second inductor L1 and the second resistor R1, then flows into the second bridge arm through the second node 42, and finally is discharged through the first transient diode TVS1 and the third transient diode TVS3 through the third node 43.

[0042] When a differential-mode surge occurs, a positive overvoltage appears at the first port 11 relative to the second port 12. The differential-mode surge current flows into the first port 11, and the second discharge diode G2 conducts, providing a low-impedance bypass for the differential-mode surge current and dissipating most of the surge energy. The remaining differential-mode surge current flows through the first inductor L1 and the first resistor R1, through the first node 41 into the second protection unit 40, and conducts forward through the first bridge arm to the third node 43. The second transient diode TVS2 conducts, and the remaining differential-mode surge current flows to the fourth node 44 and exits from the second port 12 through the fourth bridge arm. When a positive overvoltage appears at the second port 12 relative to the first port 11, the differential-mode surge current flows into the second port 12, and the second discharge diode G2 conducts, providing a low-impedance bypass for the differential-mode surge current and dissipating most of the surge energy. The residual differential-mode surge current flows through the second inductor L2 and the second resistor R2, flows into the second protection unit 40 through the first node 41, and conducts forward to the second bridge arm, reaching the third node 43. The second transient diode TVS2 is turned on, and the residual differential-mode surge current flows to the fourth node 44 and flows out from the first port 11 through the third bridge arm.

[0043] Reference Figure 3 In this embodiment, to optimize high-frequency signal transmission performance, the parameters of key components can be reasonably selected and matched according to the specific application scenario (such as the target center frequency f0): To achieve excellent high-frequency characteristics, the total equivalent capacitance C of the circuit should be as small as possible. For example, a first gas discharge tube G1 and a second gas discharge tube G2 with parasitic capacitance ≤1.5pF can be selected, and the equivalent capacitance C of the first gas discharge tube G1 and the second gas discharge tube G2 connected in parallel can be... G1 +C G2 ≤3pF.

[0044] The first diode D1, second diode D2, third diode D3, fourth diode D4, fifth diode D5, sixth diode D6, seventh diode D7, and eighth diode D8 in the second protection unit 40 can all be devices with a junction capacitance ≤7pF. In this case, the equivalent parasitic capacitance of the first diode D1, second diode D2, third diode D3, fourth diode D4, fifth diode D5, sixth diode D6, seventh diode D7, and eighth diode D8 connected in series is ≤3pF.

[0045] Parasitic capacitance C of the circuit 寄生 The total equivalent capacitance of the circuit can typically be estimated at approximately 10pF, and can be approximated by the following formula: C = C G1 +C G2 +C D1-D8 +C 寄生 Among them, C G1C represents the equivalent capacitance of the first gas discharge tube G1. G2 C represents the equivalent capacitance of the second gas discharge tube G2. D1-D8 This represents the equivalent capacitance of diodes D1, D2, D3, D4, D5, D6, D7, and D8 connected in series.

[0046] After determining the total equivalent capacitance C, the inductance values ​​of the first inductor L1 and the second inductor L2 in the inductor network unit 30 are determined based on the target center frequency f0 and the total equivalent capacitance C.

[0047] According to the formula for the resonant frequency of an LC oscillator circuit: Wherein, the center frequency f0 represents the highest signal frequency that the surge protection circuit is expected to pass (e.g., 1000MHz), L represents the total equivalent inductance value, and C represents the total equivalent capacitance value.

[0048] The above formula can be transformed into the following expression to calculate the required total inductance value L: Using the above formula, the required inductance value (such as the inductance values ​​of L1 and L2) can be calculated based on the target center frequency f0 and the total equivalent capacitance C.

[0049] Finally, to ensure the signal has sufficiently low insertion loss (e.g., attenuation no greater than -0.2dB) within the target passband (e.g., within ±30% of the center frequency f0), performance can be verified using the circuit's gain formula. The gain formula is expressed as follows: Where ω represents the signal angular frequency, A V V represents the gain. out Indicates the output voltage, V in This represents the input voltage. Through the above parameter design and verification, it can be ensured that this application provides strong protection capabilities while also possessing excellent high-frequency signal transmission performance within the specified frequency band.

[0050] The implementation principle of Embodiment 1 of this application is as follows: the surge energy is initially discharged through the first protection unit 20, the inductor network unit 30 forms a resonant network with the line equivalent capacitance, the second protection unit 40 further suppresses and protects against the surge, and finally the impedance matching resistor RJ1 achieves impedance matching. This multi-level protection and adjustment method suppresses the problem that traditional surge protection circuits cannot simultaneously address surge protection and high-frequency signal transmission performance optimization, improves the circuit's surge protection capability, and ensures stable transmission of high-frequency signals, meeting the adaptation requirements of modern electronic equipment to complex electromagnetic environments.

[0051] Example 2 This application also discloses a surge protector. The surge protector includes the surge protection device described in Embodiment 1 above.

[0052] The implementation principle of Embodiment 2 of this application is as follows: By integrating the surge protection circuit of Embodiment 1, the surge protector can effectively discharge and clamp surge energy by utilizing its internal multi-level protection architecture to work together when a surge occurs; at the same time, thanks to the optimization of parasitic parameters in the circuit, the transmission quality of high-frequency signals in the passband is ensured, thereby achieving a balance between protection performance and signal integrity.

[0053] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A surge protection circuit, characterized in that, include: The first port (11) is used to connect to an external circuit. The second port (12) is used to connect to an external circuit. An inductor network unit (30) is connected to the first port (11) and the second port (12); The second protection unit (40) is connected to the inductor network unit (30) and includes a diode bridge circuit and a voltage-limiting current discharge circuit. The diode bridge circuit includes a first bridge arm, a second bridge arm, a third bridge arm, a fourth bridge arm, a first node (41), a second node (42), a third node (43), and a fourth node (44). The first node (41) is connected to the inductor network unit (30), and the second node (42) is also connected to the inductor network unit (30). The first end of the first bridge arm is connected to the first node (41), and the second end of the first bridge arm is connected to the third node (43). The first end of the second bridge arm is connected to the second node (42), and the second end of the second bridge arm is connected to the third node (43). The first end of the third bridge arm is connected to the fourth node (44). The first end of the fourth bridge arm is connected to the fourth node (44). The third node (43) is connected to the voltage-limiting current discharge circuit, and the fourth node (44) is also connected to the voltage-limiting current discharge circuit. The third port (51) is connected to the second end of the third bridge arm; The fourth port (52) is connected to the second end of the fourth bridge arm.

2. The surge protection circuit according to claim 1, characterized in that, The first bridge arm includes a first diode D1 and a third diode D3. The anode of the first diode D1 is connected to the first node (41), the cathode of the first diode D1 is connected to the anode of the third diode D3, and the cathode of the third diode D3 is connected to the third node (43). The second bridge arm includes a seventh diode D7 and a fifth diode D5. The anode of the seventh diode D7 is connected to the second node (42), the cathode of the seventh diode D7 is connected to the anode of the fifth diode D5, and the cathode of the fifth diode D5 is connected to the third node (43). The third bridge arm includes a second diode D2 and a fourth diode D4. The cathode of the second diode D2 is connected to the first node (41), the anode of the second diode D2 is connected to the cathode of the fourth diode D4, and the anode of the fourth diode D4 is connected to the fourth node (44). The fourth bridge arm includes an eighth diode D8 and a sixth diode D6. The cathode of the eighth diode D8 is connected to the second node (42), the anode of the eighth diode D8 is connected to the cathode of the sixth diode D6, and the anode of the sixth diode D6 is connected to the fourth node (44).

3. The surge protection circuit according to claim 1, characterized in that, The voltage-limiting current discharge circuit includes a first transient diode TVS1, a second transient diode TV2, and a third transient diode TVS3. The first end of the second transient diode TVS2 is connected to the third node (43), and the second end of the second transient diode TVS2 is connected to the fourth node (44). The first end of the first transient diode TV1 is connected to the third node (43), and the second end of the first transient diode TV1 is grounded. The first end of the third transient diode TVS3 is connected to the fourth node (44), and the second end of the third transient diode TVS3 is grounded.

4. A surge protection circuit according to claim 1, characterized in that, The inductor network unit (30) includes a first inductor L1 and a second inductor L2; the first end of the first inductor L1 is connected to the first port (11), and the first end of the second inductor L2 is connected to the second port (12).

5. A surge protection circuit according to claim 1, characterized in that, It also includes a first protection unit (20), which is connected to the first port (11) and the second port (12), and includes a first gas discharge tube G1 and a second gas discharge tube G2.

6. A surge protection circuit according to claim 5, characterized in that, The first gas discharge tube G1 is a three-stage gas discharge tube, and the second gas discharge tube G2 is a two-stage gas discharge tube; wherein, the first electrode of the first gas discharge tube G1 is connected to the first port (11), the second electrode of the first gas discharge tube G1 is connected to the second port (12), and the third electrode of the first gas discharge tube G1 is grounded; the first electrode of the second gas discharge tube G2 is connected to the first electrode of the first gas discharge tube G1, and the second electrode of the second gas discharge tube G2 is connected to the second electrode of the first gas discharge tube G1.

7. A surge protection circuit according to claim 1, characterized in that, It also includes a first resistor R1 and a second resistor R2. The first resistor R1 is disposed between the inductor network and the first node (41), and the second resistor R2 is disposed between the inductor network and the second node (42). The first resistor R1 and the second resistor R2 are both non-inductive wire-wound resistors.

8. A surge protection circuit according to claim 1, characterized in that, It also includes a matching impedance resistor RJ1, the first end of which is connected to the third port (51), and the second end of which is connected to the fourth port (52).

9. A surge protection circuit according to claim 8, characterized in that, The matching impedance resistor RJ1 is a non-inductive resistor.

10. A surge protector, characterized in that, Includes the surge protection circuit as described in any one of claims 1 to 9.

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