An electronic switching device and an ethernet-based network

Abstract

An electronic switching device (3) configured for intrinsically safe transmission of electric power and data to a load (4), such as a field device in a hazardous environment, via an Ethernet-based connection (7) is provided. It comprises: a first terminal (5) electrically connected to a power source (1), a second terminal (6) electrically connected to the load (4) via the Ethernet-based connection (7), and a power line (8) extending from the first terminal to the second terminal, a current sensing circuit (9) configured to sense a current flowing within the power line, a disconnecting component (10) configured to electrically disconnect the second terminal from the first terminal in response to the sensed current being above a threshold level, and a short-circuit protection device (11) configured to slow down a current rise within the power line resulting from a short-circuit downstream of the disconnecting component.

Description

[0001] AN ELECTRONIC SWITCHING DEVICE AND AN ETHERNET-BASED NETWORK

[0002] TECHNICAL FIELD

[0003] The technology disclosed herein relates generally to electric power transfer over Ethernet, and in particular to an electronic switching device configured for intrinsically safe transmission of electric power and data to a load via an Ethernetbased connection. It further relates to an Ethernet-based network.

[0004] BACKGROUND

[0005] Intrinsically safe systems are commonly used in hazardous environments (Ex-zones) to ensure that electrical circuits do not release sufficient energy to ignite flammable gases or dust.

[0006] The standard approach for enabling intrinsically safe power transfer in Ethernetbased systems, such as Power over Ethernet (PoE), involves the use of series resistors in the protection circuit to limit the maximum current. This conventional solution is widely adopted to comply with intrinsic safety standards. However, such passive current-limiting barriers, as described in the standard IEEE 802.3cg-20i9, introduce significant limitations. The reliance on series resistors results in substantial power and heat losses, necessitating larger physical components to manage thermal dissipation effectively. Additionally, these barriers restrict the available output power to approximately one-quarter of the maximum power, significantly constraining the functionality of devices operating in Ex-zones.

[0007] The inefficiencies and design constraints of the traditional passive current -limiting solutions hinder their viability for many applications in hazardous environments. Accordingly, there is a need for improved systems and methods that enable the intrinsically safe transmission of electric power and data over Ethernet while overcoming the drawbacks of existing solutions.

[0008] SUMMARY

[0009] A primary objective of embodiments disclosed herein is to provide improved solutions for intrinsically safe transmission of power and data via an Ethernet -basedconnection. In particular, it is an objective to minimize power and heat losses within the protection circuit, thereby enabling increased power throughput to loads located in hazardous environments. More specifically, it is an objective to provide such a solution that is compliant with the standard IEC 60079-11. The standard IEC 60079-11 specifies the construction and testing of intrinsically safe apparatus intended for use in explosive atmospheres, and for associated apparatus which is intended for connection to intrinsically safe circuits which enter such atmospheres.

[0010] According to a first aspect, at least the primary objective is accomplished by an electronic switching device according to claim 1. The switching device is configured for intrinsically safe transmission of electric power and data to a load via an Ethernetbased connection. It comprises:

[0011] at least one first terminal configured to be electrically connected to a power source,

[0012] at least one second terminal configured to be electrically connected to the load via the Ethernet-based connection, and a power line extending from the first terminal to the second terminal,

[0013] a current sensing circuit configured to sense a current flowing within the power line,

[0014] a disconnecting component configured to electrically disconnect the second terminal from the first terminal in response to the sensed current being above a threshold level, and

[0015] a short-circuit protection device configured to slow down a current rise within the power line resulting from a short-circuit downstream of the disconnecting component.

[0016] The proposed switching device hence comprises an active current limiting barrier, in contrast to passive current limiting barriers comprising series resistors. The active current limiting barrier enables a larger power throughput than a passive resistorbased barrier, and it may further reduce heat losses within the barrier during steadystate operation. The short-circuit protection device enables fast reaction to a fault occurring in the Ethernet-based connection or in the load downstream of the disconnecting component. By slowing down the current rise resulting from a short-circuit, sufficient response time for the disconnecting component to break the power line maybe ensured, thereby staying within limits as defined in the IEC 60079-11standard. Hence, the current sensing circuit, the disconnecting component and the short-circuit protection device together form a short-circuit safe current cut-off circuit that disconnects and latches off when the threshold level is exceeded. In the event of a short-circuit, the short-circuit buys time for the circuit to disconnect.

[0017] Optionally, the short-circuit protection device comprises an inductor arranged in the power line between the first terminal and the disconnecting component. By including an inductor, the switching device may reduce the rate of current increase during short-circuits, improving system stability and buying time to disconnect. Several inductors may be provided, optionally in combination with one or more small resistor, such as within the milliohm (mil) range.

[0018] Optionally, the disconnecting component comprises a semiconductor device and / or an electromechanical component. Semiconductor devices and electromechanical components maybe used to efficiently break the circuit in case of excessive current.

[0019] Optionally, the disconnecting component comprises a transistor. By using a transistor, the switching device enables precise and efficient current control, reducing power loss during normal operation.

[0020] Optionally, the transistor has a control terminal electrically connected to the current sensing circuit. By connecting the control terminal to the current sensing circuit, the switching device enables automatic response to overcurrent conditions, enhancing protection and reliability.

[0021] Optionally, the switching device further comprises a latch component or latching circuit preventing the disconnecting component from opening the power line after an overcurrent event. Such a latch component or latching circuit, e.g., a thyristor, serves to protect the switching device from being turned on again unless a full circuit power reset is performed.

[0022] Optionally, the current sensing circuit is configured to generate a signal indicative of the sensed current and transmit the signal to the disconnecting component. By generating and transmitting the signal, the switching device enables real-time current monitoring and dynamic current management, improving safety and efficiency.Optionally, the current sensing circuit comprises a resistor arranged in the power line and a comparator arranged to sense a voltage drop across the resistor. Such a configuration enables accurate current measurement with simple and cost-effective components.

[0023] Optionally, the current sensing circuit comprises a Hall effect sensor. The Hall effect sensor offers non-intrusive current sensing, providing electrical isolation and reducing wear on components.

[0024] Optionally, the switching device further comprises an Ethernet switching circuit configured to be communicatively connected to an Ethernet network and to transmit data between the Ethernet network and the second terminal. By integrating the Ethernet switching circuit, the switching device ensures seamless communication and data transfer, supporting Ethernet-based system requirements.

[0025] Optionally, the Ethernet switching circuit comprises an Ethernet switch and at least one Ethernet transceiver, such as at least two Ethernet transceivers. By including these components, the switching device enables high-speed data transmission to several loads, such as field devices, and compatibility with Ethernet network protocols.

[0026] The electronic switching device may comprise coupling circuitry configured to couple data transmitting signals transmitted via the Ethernet network and power transmitting signals transmitted via the power line. The coupling circuitry may comprise a combination of inductors and capacitors. When the short-circuit protection device comprises an inductor, it may form part of the coupling circuitry.

[0027] Optionally, the second terminal is configured to be connected to a twisted-pair cable. By supporting twisted-pair cables, the switching device ensures compatibility with standard Ethernet wiring, simplifying installation and reducing costs.

[0028] Optionally, the switching device is an APL switch. Hence, the switching device supports the Advanced Physical Layer, APL, standard, enabling efficient and safe communication in hazardous environments. In some embodiments, the switching device may be an APL field switch.Optionally, the load comprises a field device located in a hazardous environment. By a hazardous environment is herein to be understood an Ex-zone as defined in the IEC 60079-11 standard. The switching device ensures safe and reliable operation under strict safety standards.

[0029] According to a second aspect, at least the primary objective is accomplished by an Ethernet-based network comprising the switching device of the first aspect, and at least one load in the form of a field device connected to the second terminal via an Ethernet-based connection. Advantages and advantageous features and embodiments of the Ethernet-based network of the second aspect appear from the above description of embodiments of the first aspect.

[0030] Optionally, the field device is located in a hazardous environment. The Ethernetbased network ensures intrinsically safe operation and compliance with safety standards, reducing risks in hazardous environments, such as in explosive environments.

[0031] Optionally, the Ethernet-based connection comprises a twisted-pair cable extending between the second terminal of the switching device and a port of the field device. By using a twisted-pair cable, the network ensures compatibility with standard Ethernet wiring, enabling efficient data and power transmission over reliable and widely adopted cabling.

[0032] Other objectives, features and advantages of the enclosed embodiments will be apparent from the following detailed disclosure, from the attached dependent claims as well as from the drawings.

[0033] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the element, apparatus, component, means, module, action, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, module, action, etc., unless explicitly stated otherwise.

[0034] BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The inventive concept is now described, by way of example, with reference to the accompanying drawings, in which:Fig. 1 is a schematic diagram illustrating an electronic switching device according to an embodiment;

[0036] Fig. 2 is a schematic diagram illustrating an active current limiting circuit of an electronic switching device according to an example embodiment;

[0037] Fig. 3 is another schematic diagram illustrating an electronic switching device according to an example embodiment; and

[0038] Fig. 4 schematically illustrates power and data transmission to several loads via an electronic switching device according to an example embodiment.

[0039] The drawings are schematic and not drawn to scale.

[0040] DETAILED DESCRIPTION

[0041] The inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the inventive concept are shown. This inventive concept may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Like numbers refer to like elements throughout the description.

[0042] Fig. i schematically illustrates an Ethernet-based network 100 comprising an electronic switching device 3, hereinafter referred to as a switching device 3, configured for intrinsically safe transmission of electric power and data to a load 4 via an Ethernet-based connection 7. The switching device 3 may typically be implemented as part of a printed circuit board, and not as a stand-alone module. It is therefore indicated by a dashed line in Fig. 1.

[0043] The switching device 3 comprises a first terminal 5 configured to be electrically connected to a power source 1, such as a power grid, a generator, a battery, or any other type of power source configured to provide electric power. The power source 1 may be configured to provide voltage-limited power. A second terminal 6 of the switching device 3 is configured to be electrically connected to the load 4 via the Ethernet-based connection 7. A power line 8 extends from the first terminal 5 to thesecond terminal 6, and a current sensing circuit 9 is configured to sense a current flowing within the power line 8. A disconnecting component 10 is configured to electrically disconnect the second terminal 6 from the first terminal 5 in response to the sensed current, sensed by the current sensing circuit 9, being above a threshold level. A short-circuit protection device 11 is further provided, which is configured to delay a current rise within the power line 8 resulting from a short-circuit downstream of the disconnecting component 10. The current sensing circuit 9, the disconnecting component 10, and the short-circuit protection device 11 together form an active current limiting circuit 15.

[0044] The switching device 3 illustrated in Fig. 1 further comprises an Ethernet switching circuit 20 configured to be communicatively connected to an Ethernet network 2, and to transmit data between the Ethernet network 2 and the second terminal 6 via the disconnecting component 10. Coupling components, not illustrated in Fig. 1, maybe provided for coupling data signals transmitted via the Ethernet switching circuit 20 and power signals sent via the power line 8. Power may usually be transmitted via Direct Current (DC) signals whereas data may be transmitted via Alternating Current (AC) signals.

[0045] The Ethernet-based connection 7 is configured to transfer power and data. It may, by way of example, comprise a twisted-pair cable extending between the second terminal 6 of the switching device 3 and a port 30 of the load 4. The twisted-pair cable may be a single-pair Ethernet cable, such as an APL (Advanced Physical Layer) spur, or a multi-pair cable, etc. In other examples, the Ethernet-based connection 7 may comprise a coaxial cable, a multi-conductor cable, or similar.

[0046] The switching device 3 may in some examples be an APL switch, although it may alternatively be another type of device, such as an industrial Ethernet switch designed for hazardous environments (Ex-zones). The switching device 3 should preferably comply with the standard IEC 60079-11 relating to intrinsic safety in explosive areas.

[0047] The current sensing circuit 9 may be configured to generate a signal indicative of the sensed current and transmit the signal to the disconnecting component 10. An example of a current sensing circuit 9 that may be used in the active current limiting circuit 15 is illustrated in Fig. 2. In this example, the current sensing circuit 9 comprises a resistor 12 arranged in the power line 8, and a comparator 13 arranged tosense a voltage drop across the resistor 12. In other examples, the current sensing circuit 9 may comprise a Hall effect sensor, a magnetic field sensor, or any other conceivable current measuring circuit. Instead of a comparator, another monitoring component maybe used, such as an operational amplifier, an analogue-to-digital converter, etc. In some examples, an integrated current sensing circuit may be used.

[0048] In the example illustrated in Fig. 2, the disconnecting component 10 comprises a transistor 14, and the short-circuit protection device 11 comprises an inductor arranged in the power line 8 between the first terminal 5 and the disconnecting component 10. The transistor 14 has a control terminal electrically connected to the current sensing circuit 9, i.e., to the comparator 13, such that it may receive a signal therefrom indicative of the sensed current. In the illustrated example, the transistor 14 is a Metal-Oxide-Semiconductor Field- Effect Transistor (MOSFET), although in other examples the transistor 14 maybe a bipolar junction transistor (BJT) such as a an NPN transistor or a PNP transistor, a Junction Field-Effect Transistor (JFET), an insulated-gate bipolar transistor (IGBT), or any other type of transistor that may be used to disconnect the power line 8 based on a signal from the current sensing circuit 9. In other examples, the disconnecting component 10 maybe any other semiconductor or electro-mechanical component which can disconnect the power line 8 based on a signal from the current sensing circuit 9, including a solid-state relay (SSR), a semiconductor switch, an electromechanical relay or switch, etc.

[0049] The active current limiting circuit 15 may further comprise a latch component, such as a thyristor 25 as illustrated in Fig. 2, which prevents the disconnecting component 10 from opening the power line 8 after an overcurrent event. Hence, a full circuit power reset is required to switch open the power line 8 again after an overcurrent event. As an alternative to a thyristor, any other known latch component or latching circuit maybe used. For example, a comparator comprising an integrated latch function may be used.

[0050] Although the short-circuit protection device 11 in Figs. 1 and 2 is illustrated as being located between the current sensing circuit 9 and the disconnecting component 10, it may in other examples be positioned in another position upstream of the disconnecting component 10, such as between the first terminal 5 and the current sensing circuit 9.The active current limiting circuit 15 is on one hand configured to disconnect the power transfer from the first terminal 5 to the second terminal 6 when the current sensing circuit 9 senses an overcurrent. On the other hand, it is configured to slow down the rapid power increase resulting from a short-circuit downstream of the disconnecting component 10, such as in the load 4 or in the Ethernet-based connection 7. With the short-circuit protection device 11, the time it takes for the current to breach the threshold level maybe increased from picoseconds to microseconds. Hereby, sufficient response time for the disconnecting component 10 to break the power line 8 may be ensured, thereby staying within limits as defined in the IEC 60079-11 standard.

[0051] The first terminal 5 and the Ethernet switching circuit 20 are not necessarily in the form of external terminals, but maybe connected to other devices or components within the switching device 3, in turn connected to the power source 1 and the Ethernet network 2.

[0052] Fig. 3 illustrates data and power transmission via an electronic switching device 3 according to an embodiment in further detail. The current sensing circuit herein comprises a current sensing resistor 12 and a comparator 13, wherein the comparator 13 is configured to send a signal indicative of the sensed current to a first disconnecting component 10a and a second disconnecting component 10b. Voltage limited input power, from a positive DC power supply, is fed to the electronic switching device 3 via a first terminal 5a and further via a first power line 8a, in which the current sensing circuit is arranged as well as a first short-circuit protection device 11 in the form of a first inductor.

[0053] The first disconnecting component 10a is electrically connected to a first potential second terminal 6a. With positive DC power being fed to the first terminal 5a, the first potential second terminal 6a is a positive terminal. The second disconnecting component 10b is electrically connected to a second potential second terminal 6b, which in the illustrated embodiment is at a lower potential than the first potential second terminal 6a. A load 4, such as a field device, can be connected between the first potential and second potential second terminals 6a, 6b, whereby a closed circuit is formed between the first terminal 5a and a return terminal 5b, herein illustrated as ground. The first and second potential second terminals 6a, 6b may be medium-dependent interfaces (MDI) configured to receive and transmit data as well as to transmit power to the load 4. The second potential second terminal 6b is connected to the return terminal 5b via a second power line 8b in which the second disconnecting component 10b and a second short-circuit protection device 16 in the form of a second inductor are arranged. Hence, both the first power line 8a and the second power line 8b may be disconnected to cut the DC power supply to the load 4 in case an overcurrent is sensed by the current sensing resistor 12. The first potential and second potential second terminals 6a, 6b may also be referred to as a positive second terminal and a negative second terminal, respectively.

[0054] The first and second short-circuit protection devices 11, 16 in the form of the first and second inductors both act as AC / DC coupling inductors. The AC / DC coupling inductors pass power transmitting DC-signals and block data transmitting AC-signals in the power lines 8a, 8b. A set of capacitors 17 are further provided, blocking the power transmitting DC-signals and passing the data transmitting AC-signals in communication lines 18 communicatively connected to an Ethernet transceiver 23, also referred to as a physical layer (PHY) of an Ethernet stack. Combined data and power transmitting signals are hence transmitted to / received from the first and second potential second terminals 6a, 6b via conductors 19a, 19b, respectively, indicated by double lines in Fig. 3.

[0055] Fig. 4 schematically illustrates the use of an electronic switching device 3 according to an embodiment of the disclosure for transfer of power and data to a plurality of loads 4 in the form of field devices located in a hazardous environment 50, e.g., a zone classified as an Ex-ia zone, an Ex-ib zone, or an Ex-ic zone. The electronic switching device 3 may be located between a safe environment, in which a power source 1 is located, and the hazardous environment. Power from the power source 1 is fed via a galvanically isolating component 24 to a plurality of active current limiting circuits 15 as described with reference to Figs. 1-3. The input power from the power source 1 may be voltage limited to comply with Ex-i requirements. Data signals from an Ethernet network 2, that may also be located in the safe environment, are further transmitted via an Ethernet switching circuit 20 comprising a primary Ethernet transceiver 22 and an Ethernet switch 21 comprising several ports. The primary Ethernet transceiver 22 is connected to an input port of the Ethernet switch 21. The Ethernet switching circuit 20 further comprises several secondary Ethernettransceivers 23, each secondary Ethernet transceiver 23 being connected to one of several output ports of the Ethernet switch 21. Data signals from each secondary Ethernet transceiver 23 are coupled to power signals as described above with reference to Fig. 3, and combined power and data transmitting signals are fed to each load 4 via each active current limiting circuit 15, respectively.

[0056] The active current limiting circuits 15 limit the steady-state current supplied to the loads 4 by disconnecting the circuits in case of overcurrent. The active current limiting circuits 15 further protect the loads 4 from damages occurring due to short-circuits in the loads 4, or at any other position of the circuits within the hazardous environment 50, by slowing down the current rise occurring as a result of the short-circuit.

[0057] The inventive concept has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended patent claims.

Claims

CLAIMS1. An electronic switching device (3) configured for intrinsically safe transmission of electric power and data to a load (4) via an Ethernet -based connection (7), the switching device (3) comprising:at least one first terminal (5) configured to be electrically connected to a power source (1), at least one second terminal (6) configured to be electrically connected to the load (4) via the Ethernet-based connection (7), and a power line (8) extending from the first terminal (5) to the second terminal (6),a current sensing circuit (9) configured to sense a current flowing within the power line (8),a disconnecting component (10) configured to electrically disconnect the second terminal (6) from the first terminal (5) in response to the sensed current being above a threshold level, anda short-circuit protection device (11) configured to slow down a current rise within the power line (8) resulting from a short-circuit downstream of the disconnecting component (10).

2. The switching device of claim 1, wherein the short-circuit protection device (11) comprises an inductor arranged in the power line (8) between the first terminal (5) and the disconnecting component (10).

3. The switching device of claim 1 or 2, wherein the disconnecting component (10) comprises a semiconductor device and / or an electromechanical component.

4. The switching device of any one of the preceding claims, wherein the disconnecting component comprises a transistor (14).

5. The switching device of claim 4, wherein the transistor (14) has a control terminal electrically connected to the current sensing circuit (9).

6. The switching device of any one of the preceding claims, wherein the current sensing circuit (9) is configured to generate a signal indicative of the sensed current and transmit the signal to the disconnecting component (10).

7. The switching device of any one of the preceding claims, wherein the current sensing circuit (9) comprises a resistor (12) arranged in the power line (8), and a comparator (13) arranged to sense a voltage drop across the resistor (12).

8. The switching device of any one of claims 1-6, wherein the current sensing circuit (9) comprises a Hall effect sensor.

9. The switching device of any one of the preceding claims, further comprising an Ethernet switching circuit (20) configured to be communicatively connected to an Ethernet network (2), and to transmit data between the Ethernet network (2) and the second terminal (6).

10. The switching device of claim 9, wherein the Ethernet switching circuit (20) comprises an Ethernet switch (21) and at least one Ethernet transceiver (22, 23).

11. The switching device of any one of the preceding claims, wherein the second terminal (6) is configured to be connected to a twisted-pair cable.

12. The switching device of any one of the preceding claims, wherein the switching device is an APL switch.

13. The switching device of any one of the preceding claims, wherein the load (4) comprises a field device located in a hazardous environment (50).

14. An Ethernet-based network (100) comprising the switching device (3) of any one of the preceding claims, and at least one load (4) in the form of a field device connected to the second terminal (6) via an Ethernet-based connection (7).

15. The Ethernet-based network of claim 14, wherein the Ethernet-based connection (7) comprises a twisted-pair cable extending between the second terminal (6) of the switching device (3) and a port (30) of the field device.

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