Emc protection circuit of ethercat master station

Abstract

This utility model discloses an EMC protection circuit for an EtherCAT master station; belonging to the field of EMC protection circuit design technology; its key technical features include multiple modules connected sequentially along the current direction: a primary overcurrent protection module, used to cut off the circuit when the input current exceeds a threshold; a surge energy discharge module, electrically connected to the output terminal of the primary overcurrent protection module, used to absorb high-voltage transient energy; a common-mode noise suppression module, electrically connected to the output terminal of the surge energy discharge module, used to attenuate common-mode interference signals; and a graded voltage clamping module, electrically connected to the output terminal of the common-mode noise suppression module, used to reduce the residual voltage to a safe level in a stepwise manner; this utility model aims to provide an EMC protection circuit for an EtherCAT master station; by improving the power filter design, the EMC protection level of the EtherCAT master station meets the immunity requirements in industrial environments.

Description

Technical Field

[0001] This utility model relates to the field of EMC protection circuit design technology, and more specifically, to an EMC protection circuit for an EtherCAT master station. Background Technology

[0002] EtherCAT is an open-architecture Ethernet-based fieldbus system designed specifically for industrial automation. It has the following characteristics:

[0003] High performance and real-time performance: EtherCAT employs "Processing on the Fly" technology to achieve low latency and high bandwidth utilization. Each node receives and transmits data in less than 1 microsecond, making EtherCAT a high-performance distributed I / O system.

[0004] Flexibility: EtherCAT supports various network topologies, such as bus, tree, and star, to adapt to different industrial automation needs.

[0005] Wide applicability: Any control unit with a standard Ethernet controller can serve as an EtherCAT master, from small 16-bit processors to high-performance PC systems.

[0006] Compliant with Ethernet standards: EtherCAT can coexist on the same bus with other Ethernet devices and protocols, utilizing standard Ethernet switches and other structural components.

[0007] The Importance of EMC Protection:

[0008] In industrial environments, electromagnetic interference (EMI) is a major challenge for EtherCAT master circuits. Electromagnetic waves generated by high-frequency equipment, motors, frequency converters, and other devices can interfere with network transmission, leading to data packet loss and system instability. EMC protection design aims to ensure that equipment operates normally in electromagnetic environments without interfering with other devices. Its importance is reflected in the following aspects:

[0009] Improve product reliability: EMC design and testing can ensure the stability and reliability of products and avoid failures and damage caused by electromagnetic interference.

[0010] Compliance with regulations: Many countries have established relevant regulations and standards that require equipment to meet specific EMC requirements before it can be sold.

[0011] Market access: Products that comply with EMC standards are more likely to pass relevant certifications and obtain market access qualifications.

[0012] Existing EtherCAT master circuit EMC protection technology:

[0013] Currently, the EMC protection design of EtherCAT master circuits mainly adopts the following technologies:

[0014] Grounding design: Use appropriate grounding techniques, such as shielded grounding, separate grounding, star grounding, etc., to reduce the propagation and reception of electromagnetic interference.

[0015] Shielding design: Use metal shielding covers, shielding boxes, shielding sleeves, etc. to surround the interfaces of the EtherCAT master station to reduce the entry of external electromagnetic interference and the leakage of electromagnetic radiation generated by the equipment.

[0016] Filtering design: Add appropriate filters to power and signal lines, such as power filters, signal line filters, common-mode filters, etc., to suppress high-frequency noise and electromagnetic interference.

[0017] Interface design: Differential signal transmission is adopted to improve anti-interference capability; appropriate signal level and signal rate are used to reduce radiation and sensitivity.

[0018] Existing EtherCAT master circuit EMC protection technologies suffer from several drawbacks, including a lack of energy coordination mechanisms in the power supply filtering architecture, structural defects in the power supply filtering design leading to insufficient residual voltage suppression and device coordination failures; a lack of dynamic response capability resulting in common-mode inductor saturation due to power-on surges and TVS clamping timing mismatches; and protection levels that fail to meet industrial standards. Utility Model Content

[0019] The purpose of this invention is to address the shortcomings of the prior art by providing an EMC protection circuit for an EtherCAT master station. By improving the power filter design, the EMC protection level of the EtherCAT master station meets the immunity requirements in industrial environments.

[0020] To achieve this objective, the present invention adopts the following technical solution: an EMC protection circuit for an EtherCAT master station, comprising multiple modules connected sequentially along the current direction:

[0021] The primary overcurrent protection module is used to cut off the circuit when the input current exceeds the threshold.

[0022] The surge energy discharge module is electrically connected to the output terminal of the primary overcurrent protection module and is used to absorb high voltage transient energy.

[0023] The common-mode noise suppression module is electrically connected to the output terminal of the surge energy discharge module and is used to attenuate common-mode interference signals;

[0024] The graded voltage clamping module is electrically connected to the output of the common-mode noise suppression module and is used to reduce the residual voltage to a safe level in a stepwise manner.

[0025] Preferably, the surge energy discharge module includes a nonlinear voltage-sensitive device and a gas discharge device connected in series, wherein the nonlinear voltage-sensitive device is a varistor and the gas discharge device is a gas discharge tube.

[0026] Preferably, the threshold voltage of the varistor is lower than the breakdown voltage of the gas discharge tube.

[0027] Preferably, the graded voltage clamping module includes a first-stage TVS diode, which is a 70V bidirectional TVS diode.

[0028] Preferably, the graded voltage clamping module further includes a secondary TVS diode, which is a 30V bidirectional TVS diode.

[0029] Preferably, the current limiting module is connected between the output terminal of the surge energy discharge module and the input terminal of the common mode noise suppression module to suppress transient current peaks and power-on surges.

[0030] Preferably, the current limiting module is a thermistor.

[0031] Preferably, the primary overcurrent protection module is a fusible fuse.

[0032] Preferably, the common-mode noise suppression module is a common-mode inductor.

[0033] One of the above technical solutions has the following advantages or beneficial effects: This utility model uses a multi-level module design for protection, achieving gradual energy attenuation. Compared with traditional single-level protection solutions, the residual voltage is reduced by 60% in industrial surge tests, from 200V to ≤50V, solving the core problem of insufficient immunity in industrial environments. By improving the power filter design, the EtherCAT master station's EMC protection level meets the immunity requirements in industrial environments. Attached Figure Description

[0034] Figure 1 This is a circuit connection diagram of one embodiment of the present invention;

[0035] Figure 2 This is a schematic diagram of the circuit structure of one embodiment of the present invention;

[0036] Figure 3 This is a schematic diagram of the test waveform of voltage clamping using a 70V bidirectional TVS diode according to this utility model.

[0037] Figure 4 This is a schematic diagram of the test waveform of the present invention using a 30V bidirectional TVS diode for voltage clamping.

[0038] In the diagram: 1. Primary overcurrent protection module; 2. Surge energy discharge module; 3. Common mode noise suppression module; 4. Graded voltage clamping module; 5. Current limiting module. Detailed Implementation

[0039] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0040] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0041] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0042] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0043] like Figures 1-4 As shown below, in conjunction with Figures 1 to 4 As shown, an EMC protection circuit for an EtherCAT master station according to an embodiment of the present invention includes multiple modules connected sequentially along the current direction:

[0044] Primary overcurrent protection module 1 is used to cut off the circuit when the input current exceeds the threshold.

[0045] Surge energy discharge module 2 is electrically connected to the output terminal of the primary overcurrent protection module 1 and is used to absorb high voltage transient energy;

[0046] The common-mode noise suppression module 3 is electrically connected to the output terminal of the surge energy discharge module 2 and is used to attenuate the common-mode interference signal.

[0047] The graded voltage clamping module 4 is electrically connected to the output terminal of the common-mode noise suppression module 3, and is used to reduce the residual voltage to a safe level in a stepwise manner.

[0048] This invention employs a multi-level module design for protection, achieving progressive energy attenuation. Compared to traditional single-level protection schemes, residual voltage is reduced by 60% in industrial-grade surge tests, from 200V to ≤50V, solving the core problem of insufficient immunity in industrial environments. Through improved power filter design, the EtherCAT master station's EMC protection level meets the immunity requirements of industrial environments.

[0049] Preferably, the surge energy discharge module 2 includes a nonlinear voltage-sensitive device and a gas discharge device connected in series. The nonlinear voltage-sensitive device is a varistor RD1; the gas discharge device is a gas discharge tube D28.

[0050] The function and advantages of connecting a varistor in series with a gas discharge tube:

[0051] 1. In power supply filtering design, using a varistor and a gas discharge tube in series can combine the advantages of both. The gas discharge tube can absorb large transient overvoltages, while the varistor can clamp the voltage to a safe level and absorb residual energy. This combination can provide more comprehensive overvoltage protection.

[0052] 2. Varistors absorb a large current during overvoltage events, which causes physical and chemical changes in their internal materials, accelerating aging. In some cases, an aged varistor may short-circuit, posing a fire hazard. Connecting a gas discharge tube in series can prevent an aged varistor from short-circuiting the downstream circuitry of the second line of defense.

[0053] 3. Gas discharge tubes have the disadvantage of high freewheeling voltage. A conducting gas discharge tube may not be able to turn off on its own and thus burn out. A series varistor can solve this problem.

[0054] 4. The gas discharge tube will conduct light during an overpressure event, making it easy to visually observe whether the second line of defense has played a protective role during an overpressure event.

[0055] The varistor RD1 and the gas discharge tube D28 are connected in series to form a synergistic protection: the varistor quickly clamps overvoltage with a response time in the nanosecond range, preventing the downstream circuit from being subjected to high voltage impact; the gas discharge tube carries a large current, such as 20kA under an 8 / 20μs waveform, to prevent the varistor from aging and short-circuiting due to excessive energy absorption.

[0056] Meanwhile, the threshold voltage of the varistor is lower than the breakdown voltage of the gas discharge tube.

[0057] By setting the voltage of the varistor to be less than the voltage of the gas discharge tube breakdown, the varistor is ensured to operate preferentially during overvoltage events, thus preventing the gas discharge tube from frequently conducting. The gas discharge tube only starts during extremely high surges, solving its "follow-current burnout" problem.

[0058] Preferably, the graded voltage clamping module 4 includes a first-stage TVS diode, which is a 70V bidirectional TVS diode D27.

[0059] A TVS diode is a device used to protect circuits from transient overvoltage damage. When the voltage across the TVS diode exceeds its breakdown voltage, the TVS diode quickly conducts, clamping the voltage to a predetermined level, thereby protecting subsequent circuitry. After the overvoltage signal passes through the preceding modules, the residual voltage is still around 200V; after passing through a TVS diode, the residual voltage is less than 105V.

[0060] The 70V bidirectional TVS diode D27 acts as the first-stage clamp, reducing the residual voltage after the common-mode inductor from approximately 200V to ≤105V, thus protecting the subsequent 100V DC-DC chip from breakdown.

[0061] Meanwhile, the graded voltage clamping module 4 also includes a secondary TVS diode, which is a 30V bidirectional TVS diode D21.

[0062] Since the EtherCAT master station is powered by 24V, the rated voltage of the electronic components after the power filter is less than 50V. Therefore, a second-stage TVS diode is used to clamp the overvoltage signal to around 50V. A 30V bidirectional TVS diode D21 is added to form a second-stage clamp, further reducing the residual voltage to ≤50V. This value is lower than the maximum withstand voltage of the subsequent circuit (50V), ensuring the safe operation of the 24V-powered EtherCAT master station IC.

[0063] Preferably, the current limiting module 5 is connected between the output terminal of the surge energy discharge module 2 and the input terminal of the common mode noise suppression module 3, and is used to suppress transient current peaks and power-on surges.

[0064] A current limiting module 5 is inserted between the surge discharge module and the common mode suppression module to suppress transient current spikes when the gas discharge tube is turned on, and protect the insulation of the common mode inductor L5 coil; it also limits the capacitor charging surge at the moment of power-on, and prevents the varistor from deteriorating due to multiple surge impacts.

[0065] The current limiting module 5 is a thermistor RT17, and the thermistor RT17 has a room temperature resistance value of 10Ω to 100Ω.

[0066] The purpose of providing an overvoltage signal path for current limiting module 5 is as follows:

[0067] The second line of defense surge energy discharge module 2 has a strong pressure discharge capability, but its response speed is lower than that of the subsequent line of defense. When lightning surges, the current limiting module 5 first limits the current spike, and then the varistor absorbs the residual energy to avoid damage to the common mode inductor due to overcurrent.

[0068] It also serves to suppress inrush current during startup.

[0069] Thermistors have a relatively high resistance at room temperature, ranging from 10Ω to 100Ω. When a device is powered on, they effectively limit the capacitor charging current, preventing large current surges to the varistor and common-mode inductor. For example, with a 220V AC input, without an NTC, the initial surge current might exceed 10A, while a series NTC can limit the current to a safe range of 2A to 5A.

[0070] The NTC thermistor RT17 with a resistance of 10-100Ω at room temperature is selected. Its negative temperature characteristic can automatically increase the resistance value during surge events to enhance the current limiting effect; and the resistance decreases during steady-state operation to reduce power loss.

[0071] Specifically, the primary overcurrent protection module is a fuse FUSE1 with a rated current of 3.15A.

[0072] Fuses primarily function as overcurrent protection in circuits. They melt and break the circuit when the current exceeds the rated value, thus protecting other components from damage. They also disconnect the circuit in case of a short circuit in a varistor; the rated value matches the maximum load current of an industrial 24V power supply to prevent false triggering.

[0073] The common-mode noise suppression module 3 is a common-mode inductor L5.

[0074] The purpose of setting a common-mode inductor:

[0075] Suppress common-mode noise:

[0076] Principle: A common-mode inductor consists of two coils wound in opposite directions with the same number of turns wound on the same magnetic core. When noise currents with the same common-mode current flow through it, the magnetic fields in the core are superimposed, and the inductor exhibits high impedance, reflecting or absorbing noise energy; normal signals with opposite differential-mode current flow through it with almost no attenuation because the magnetic fields cancel each other out.

[0077] Within the target frequency band, such as 30MHz to 300MHz, the insertion loss can reach over 40dB, significantly attenuating common-mode interference.

[0078] Enhance anti-interference capabilities:

[0079] By suppressing common-mode noise on power lines and signal lines, the impact of electromagnetic interference (EMI) on the circuit is reduced, while the external radiated interference of the equipment is also reduced, thus meeting EMC standards.

[0080] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0081] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.

Claims

1. An EMC protection circuit for an EtherCAT master station, characterized by comprising multiple modules sequentially connected along the current direction: Primary overcurrent protection module (1) is used to cut off the circuit when the input current exceeds the threshold. The surge energy discharge module (2) is electrically connected to the output terminal of the primary overcurrent protection module (1) and is used to absorb high voltage transient energy. The common-mode noise suppression module (3) is electrically connected to the output terminal of the surge energy discharge module (2) and is used to attenuate the common-mode interference signal; The graded voltage clamping module (4) is electrically connected to the output terminal of the common-mode noise suppression module (3) and is used to reduce the residual voltage to a safe level in a stepwise manner.

2. The EMC protection circuit of an EtherCAT master station according to claim 1, characterized in that, The surge energy discharge module (2) includes a nonlinear voltage-sensitive device and a gas discharge device connected in series. The nonlinear voltage-sensitive device is a varistor RD1; the gas discharge device is a gas discharge tube D28.

3. The EMC protection circuit of an EtherCAT master station according to claim 2, characterized in that, The threshold voltage of the varistor is lower than the breakdown voltage of the gas discharge tube.

4. The EMC protection circuit of an EtherCAT master station according to claim 2, characterized in that, The graded voltage clamping module (4) includes a first-stage TVS diode, which is a 70V bidirectional TVS diode (D27).

5. The EMC protection circuit of an EtherCAT master station according to claim 4, characterized in that, The graded voltage clamping module (4) also includes a secondary TVS tube, which is a 30V bidirectional TVS tube (D21).

6. The EMC protection circuit of an EtherCAT master station according to claim 1, characterized in that, The current limiting module (5) is connected between the output terminal of the surge energy discharge module (2) and the input terminal of the common mode noise suppression module (3) to suppress transient current peaks and power-on surges.

7. The EMC protection circuit of an EtherCAT master station according to claim 6, characterized in that, The current limiting module (5) is a thermistor (RT17).

8. The EMC protection circuit of an EtherCAT master station according to claim 1, characterized in that, The primary overcurrent protection module is a fusible fuse (FUSE1).

9. The EMC protection circuit for an EtherCAT master station according to claim 1, characterized in that, The common-mode noise suppression module (3) is a common-mode inductor (L5).

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