APL Field Switch with Dynamic Power Allocation

Abstract

An APL field switch includes several ports, many of which transmit power to APL field devices connected to spurs extending from the ports. The APL power class of each port can be dynamically set by the user to allow more efficient allocation of power to the ports to meet the needs of the connected field devices.

Description

[Technical field]

[0001] This application claims the benefit of priority and the filing date of U.S. patent application Ser. No. 63 / 152,432, entitled "APL FIELD SWITCH WITH DYNAMIC POWER ALLOCATION," filed on February 23, 2021, Attorney Docket No. 14-1381-P, which priority application was pending as of the filing date of this application and is incorporated by reference as if fully set forth herein.

[0002] The present disclosure relates generally to APL field switches for use in process control networks. [Background technology]

[0003] The Ethernet Advanced Physical Layer (APL) specification is based on the industry standard (IEEE 802.3cg) for the physical layer of Ethernet-based two-wire process control networks. Ethernet-APL networks allow data rates up to 10 Megabits per second (Mbps) full duplex. Ethernet-APL networks support data transmission distances of up to 1,000 meters, power transmission over the same two wires that transmit data, multi-drop, intrinsic safety, Ethernet connectivity to field devices, and other process control needs.

[0004] The basics of Ethernet networking can be understood from a number of books, including, for example, "Ethernet Networking: A Practical Guide to Ethernet Networking," by John F.

[0005] The transmission of power and Ethernet-style data over two wires is collectively referred to herein as "Power over Data" or PoD. Power and Ethernet data can be transmitted over the same twisted wire pair because the power and data domains exist in different frequency domains. Being in different frequency domains allows power and data to travel simultaneously on the same twisted wire pair and still be separated into separate DC power and AC data components as needed.

[0006] Ethernet-APL networks utilize a trunk and spur topology. APL 2-wire trunks can transmit higher power over longer distances, up to 1,000 meters. APL 2-wire spurs carry lower power over shorter distances, up to 200 meters, from the trunk to the field device.

[0007] The APL field switch connects the APL trunks to APL spurs extending from the field switch. The field switch includes several ports for connecting the spurs to the field switch. Each port forms part of a respective channel that includes power / data wires connected to the port that transmit power received by the APL field switch to the port and transmit Ethernet data between the port and the APL trunk. Each power / data wire includes a power line segment that transmits only power and a data line segment that transmits only data. An Ethernet switch in the data line segment transmits and receives Ethernet data over the data line segment. Power and data are transmitted over a two-wire spur that connects the port and the field device.

[0008] APL field switches receive power for distribution to field switch ports either through the network trunk itself or from an external auxiliary DC power source. The auxiliary DC power source typically provides more power than is available through the network trunk. As a result, the total power available to the APL field switch for a port depends on the power source (trunk or auxiliary DC power source). The maximum power sent through a port cannot exceed the power received by the APL field switch.

[0009] APL field switches may also be "cascaded," i.e., an upstream APL field switch may supply power to a downstream APL field switch. Thus, the total power supplied to the upstream APL field switch powers the field devices attached to the upstream APL field switch, and It must be sufficient to power the field devices attached to the downstream APL field switch (and any further downstream APL field switches).

[0010] The APL standard defines multiple power classes that can be applied to each port of an APL field switch. A power class defines the maximum power available at a port that can be transmitted over a spur connected to the port. For purposes of explanation, assume that the APL standard defines four power classes: Power Class A, Power Class B, Power Class C, and Power Class D, where each power class is associated with a different maximum power output.

[0011] Each power class is associated with a power profile having predefined voltage and power parameters that define the maximum power output of the port, with some power classes allowing a greater power output than other power classes.

[0012] Each field device attached to a port via a spur has its own independent power requirements that may vary between attached field devices. A field device must be attached to a port associated with a power class sufficient to power the field device.

[0013] However, APL field switches are manufactured with a set number of ports (e.g., 8, 12, 16, or 24 ports). Thus, APL field switches must limit the number and type of power classes associated with the set number of ports in order to comply with maximum power requirements. For example, a manufacturer may offer multiple models of a 24-port APL field switch, with each model having ports with a different combination of associated power classes.

[0014] The number of APL field switch models for each set number of ports can be overwhelming, requiring manufacturers to configure and offer only a subset of the various possible combinations, and customers must compromise in their field switch selection. Additionally, customers may need to accept the manufacturer's choice of port location (left, right, etc.) for each power class.

[0015] APL field switch customers may have use cases where the number of field devices attached to the field switch varies and the power class required to provide adequate power to the various field devices attached to the ports.

[0016] A customer may mistakenly specify an APL field switch while setting up an industrial control network based on an incorrect combination of port and power profile, only to realize during installation that the APL field switch selected is inappropriate and needs to be replaced (or the system needs to be redesigned to accommodate the APL field device). [Prior art documents] [Non-patent literature]

[0017] [Non-Patent Document 1] Sterling & Wissler, The Industrial Ethernet Networking Guide, 2003 (ISBN 0-7668-4210-X), published by Delmar Learning Summary of the Invention [Problem to be solved by the invention]

[0018] Therefore, what is needed is an APL field switch that can provide dynamic power allocation to ports to meet the specific needs of a customer and in response to changes in the field switch's power source and changes in the field devices attached to the APL field switch. [Means for solving the problem]

[0019] An APL field switch is disclosed that provides dynamic power allocation for each port. A customer can purchase an APL field switch with a desired number of ports, and after purchase, the user can selectively change the power class of each port to meet the needs of the industrial control network. Manufacturers can sell models of APL field switches that differ only in the number of ports offered, but users can associate ports with various combinations of power classes after purchase.

[0020] The disclosed APL field switches can be powered by either the APL network trunk or an auxiliary DC power source. The total power made available to the ports cannot exceed the power supplied to the APL field switch (minus the power required to power the APL field switch itself).

[0021] The APL field switch provides a default power class assignment for each port. The default power class assignment may depend on the power source connected to the APL field switch. The total power assigned cannot exceed the total power available to the port.

[0022] A user can selectively change the power class of a port, but the power allocated to the ports cannot, in total, exceed the total power available to the APL field switch.

[0023] APL field switches are provided with a default set of port power class assignments for each type of power source (trunk or auxiliary DC power) connected to them. The default assignments set the default power class for each port. Different ports may be assigned different default power classes.

[0024] The APL field switch software allows the user to reconfigure the APL field switch during commissioning and during run-time, within the allowable limits of the APL field switch hardware and the power supplied to the APL field switch.

[0025] Example of default configuration based on power supply type: Auxiliary DC power supply All field switch ports are configured for Class B (relatively higher) power operation and cascading operation is enabled. Power Through Trunk All field switch ports are configured for Class A (relatively lower) power operation and cascading operation is disabled.

[0026] APL field switch software allows users to override default port power class assignments via the software application. The application enforces the rule that user configurations cannot exceed the power characteristics of the APL field switch.

[0027] When powered over a trunk, the software application limits the maximum number of Class B spurs available to a user based on the available power budget defined by the trunk power source.

[0028] In this example configuration, power classes are enforced independently for each port by setting an in-line selectable current limiting device to the appropriate current limit for the port's power class. A current limiting device is a device placed in a circuit that trips when the current exceeds a predefined maximum current (amperage), thereby interrupting the circuit and stopping the current or reducing the current in the circuit to a safe level. A current limiting device limits the maximum flow of current through a port. Each port class is associated with a respective current or amperage limit.

[0029] Selectably adjustable current limiting devices that can be installed in a circuit to selectively limit the maximum amperage in the circuit are known and can be adapted for use in accordance with the present disclosure.

[0030] As a non-limiting example, the selectable current limiting device includes an electronic fuse or eFuse. An electronic fuse is an example of an all-electronic selectable current limiting fuse that trips when the current exceeds a predetermined amperage. An electronic fuse does not rely on the heat and subsequent open circuit of an in-line element to stop the current, it reacts quickly and can be easily reset. The electronic fuse is connected to a digital potentiometer with a selectable resistance value. The resistance value of the digital potentiometer sets the current limit that opens the electronic fuse. The power class of the port is then determined by the current limit that opens the electronic fuse. A user in this embodiment sets the power class of the port by setting the resistance value of the potentiometer.

[0031] Other objects and features of the present disclosure will become apparent as the description proceeds, especially when considered in conjunction with the accompanying drawings, which illustrate one or more illustrative embodiments. [Brief description of the drawings]

[0032] [Figure 1] 1 illustrates a process control network including an APL field switch according to the present disclosure. [Diagram 2] 1 illustrates an APL field switch according to the present disclosure. [Diagram 3] FIG. 3 is an expanded view of a channel of the APL field switch shown in FIG. 2. [Figure 4] FIG. 2 is a schematic diagram of a constant current limiting circuit. [Diagram 5] FIG. 2 is a schematic diagram of a foldback current limiting circuit. [Figure 6] FIG. 1 is a schematic diagram of a parallel resettable fuse configuration. [Figure 7] FIG. 4 is a schematic diagram of the power management module shown in FIG. 3 connected to a user-configurable current limiting device of a first embodiment according to the present disclosure. [Figure 8] 8 is a schematic diagram of the current limiting device shown in FIG. 7 in a first operating state associated with a first power class. [Figure 9] 9 is similar to FIG. 8, but illustrates the current limiting device in a second operating state associated with a second power class. [Figure 10] FIG. 4 is a schematic diagram of a current limiting device according to a second embodiment. [Figure 11] 3 illustrates an exemplary GUI for use with the power management module shown in FIG. 2 . [Figure 12] 2 illustrates an example wireframe of a graphical user interface of a software application intended for use with the APL process control network shown in FIG. 1; [Figure 13] 3 illustrates generally a distributed computing network for use in conjunction with the power management module illustrated in FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] FIG. 1 illustrates a process control network 10 consisting of a 10 Mbps Ethernet-APL process control network 12 and a 100 Mbps industrial Ethernet process control network 14 .

[0034] The APL-Ethernet process control network 12 conforms to the Ethernet Advanced Physical Layer (APL) specification. The APL-Ethernet network 12 uses a two-wire Trunk cable and a two-wire Spur cable for simultaneous data and power transmission over two wires. The trunks and spurs of the APL-Ethernet process control network 12 are shown as solid lines in FIG.

[0035] The illustrated industrial Ethernet process control network 14 is an Ethernet / IP (Ethernet Industrial Protocol network). The industrial Ethernet network 14 uses standard Ethernet CAT5 or higher Ethernet cables (referred to herein as "standard Ethernet cables") and associated hardware that are also commonly used in business Ethernet LAN networks. The standard Ethernet cables are shown in FIG. 1 as dashed lines.

[0036] The process control network 10 includes a backend having an engineering station 16, an operation station 18, a process controller 20, and a backend non-APL Ethernet switch 22. The backend stations, the process controller, and the Ethernet switch are connected by standard CAT5 or higher Ethernet cables for high speed Ethernet communications (100 Mbps or faster).

[0037] The industrial Ethernet network 14 includes a non-APL Ethernet switch 24 connected to a back-end Ethernet switch 22 by a standard CAT5 or better Ethernet cable. The industrial Ethernet switch 24 is powered by an auxiliary power source represented by arrow 25. The industrial Ethernet switch 24 is connected to non-APL field devices 26a and 26b by standard CAT5 or better Ethernet cables. The field devices 26a and 26b are powered by the auxiliary power source without being connected to a network. The back-end can communicate with the field devices 26a, 26b via the back-end Ethernet switch 22 and the industrial Ethernet switch 24.

[0038] APL-Ethernet network 12 includes an APL power switch 26 connected to an APL trunk 28 that extends from the APL power switch to a downstream APL field switch 30, which in turn extends downstream to an APL field switch 32. APL power switch 26 receives power from an auxiliary DC power source represented by arrow 34. APL power switch 26 injects power into the APL trunk for simultaneous transmission of power and data over the trunk.

[0039] The APL power switch 26 is connected for data transmission to the back-end Ethernet switch 22 via a standard Ethernet CAT5 or higher cable. The APL power switch 26 converts between 100 Mbps Ethernet transmitted over a standard Ethernet cable and 10 Mbps Ethernet transmitted over an APL-Ethernet 2-wire cable for data communication between the APL-Ethernet network 12 and the back-end Ethernet switch 22.

[0040] The APL field switch 30 itself is powered via the APL trunks 28. The APL field switch 30 transmits power received via the APL trunks to the field devices attached to the APL field switch 30. The APL field switch 30 as shown in FIGURE 1 is connected to field device 36a and field device 36b by respective APL spurs extending from ports on the APL field switch. The APL field switch 30 transmits both power and data to the field device 36a through the ports connected to the field devices.

[0041] The APL field switch 32 is similar to the trunk-powered APL field switch 30, but is powered only by an auxiliary power source represented by arrow 38. The APL field switch 32 is not powered by the trunks 28, but rather transmits and receives data over the APL trunks 28. The APL field switch 32 as shown in FIG. 1 is connected to APL field device 40a and APL field device 40b by respective APL spurs extending from ports of the APL field switch. The APL field switch 32 transmits both power and data to the field device 40 through the ports connected to the field devices.

[0042] The field devices 26, 36, 40 are sensors, actuators, etc. that are compatible with the network to which they are connected. The field devices are configured to output sensor data, operational status, command confirmation, diagnostics, and other outgoing network communications necessary for the operation of the process control network 10, and / or receive commands, data requests, and other incoming network communications necessary for the operation of the process control network 10.

[0043] The trunk powered APL field switch 30 and the auxiliary DC powered APL field switch 32 each provide a dynamic power allocation feature in accordance with the present disclosure. Since the two APL field switches shown in Figure 1 are identical, only APL field switch 30 will be described in detail.

[0044] 2 illustrates generally the components of an APL field switch 30 that are at least partially enclosed within an APL field switch case. The APL field switch has a trunk terminal 35 for connecting the field switch to the APL trunk 28 and an external power terminal 37 for connecting the field switch to an auxiliary power source (such as auxiliary power supply 38). The illustrated APL field switch 30 also includes one or more dedicated data terminals 39 that transmit data, rather than power, into and out of the APL field switch 30. The dedicated data terminals 37 can be implemented as Ethernet RJ45 connectors, SFP optical connectors, etc. for connection to compatible external optical or electrical data cables.

[0045] When the APL field switch is powered by an APL trunk connected to trunk terminal 35, trunk terminal 35 functions as a power terminal that allows the APL field switch to receive power and as a data terminal that transmits data between the APL trunk and the APL field switch. When the APL field switch is powered by an external power source connected to external power terminal 37, external power terminal 37 functions as a power terminal that allows the APL field switch to receive power and trunk terminal 35 functions as a data terminal that transmits data between the APL trunk and the APL field switch. Each dedicated data terminal 43 functions only as a data terminal that transmits data to and from the APL field switch 30.

[0046] Power received via the power terminals 35, 37 is received by the APL field switch 30 via a power line 46 connected to the terminals 35, 37. The power line 46 also transmits data to the APL field switch via the trunk terminal 35 and transmits data from the APL field switch via the trunk terminal 35. A data line 41a extends between the power line 46 and one end of the Ethernet switch 42. The data line 41a extracts data received via the trunk terminal 35 from the power line 46, transmits the data to the Ethernet switch 42, and injects data received from the Ethernet switch 42 onto the power line 46 for transmission via the trunk terminal 35. A data line 41b extends between each data terminal 39 and one end of the Ethernet switch 42 for transmission of data to and from the data terminal 39. The Ethernet switch 42 in turn has a data line 43 extending from the other end of the Ethernet switch for transmitting data between the Ethernet switch and the connected field devices.

[0047] The APL field switch 30 has N similar channels 48 (a single channel 48 is shown generally in more detail in FIG. 3). An isolated switching power supply 45 is disposed on a device line 46 between terminals 42, 44 and the channel 48. The transmission of power and Ethernet format data frames through the APL field switch 30 between the APL trunks 28 and the APL field switch ports is otherwise conventional, except for the ability of the APL field switch 30 to provide dynamic power allocation to ports, as described in more detail below.

[0048] Each channel 48 includes a port 50 for attaching a spur to the channel 48. In the illustrated APL field switch, each port is formed as a two-wire Ethernet compatible connector (referred to herein as a port connector). In alternative embodiments, the port connector 50 may be configured as a screw or clamp terminal, an M12 connector, or other connector compatible with the APL specification. Various styles or types of port connectors suitable for forming the ports 50 may be provided by the APL field switch manufacturer, and a port may include multiple types of port connectors provided in parallel to provide increased connection flexibility in connecting field devices to the port.

[0049] Port 50 is connected to power line 46 via a channel power line 47. N channels 48 have respective channel power lines 47 extending in parallel from power line 46 to channel port 50. Channel power lines 47 transmit power over the channel. Thus, the port class associated with port 50 is also associated with the channel 48 that contains port 50. Channel power lines 47 are capable of transmitting a maximum power. The actual power that can be transmitted by a channel power line 47 in use at a particular time is limited to the maximum power of the port class associated with the channel at that time, as will be explained in more detail below.

[0050] Channel power line 47 includes a power line segment 49 disposed between a port 50 and a connection with channel data line 43 that also transmits data between port 50 and data line 43. Channel data received from Ethernet switch 42 is injected onto channel power line 47 for transmission to port 50, and data received on channel power line 47 via port 50 is extracted from channel power line 47 for transmission to Ethernet switch 42. An APL10BaseTIL Ethernet physical layer transceiver 53 disposed on data line 42 enables communication of Ethernet format data frames between port 50 and Ethernet switch 42.

[0051] Channel 48 conceptually operates as an Ethernet switch that relays Ethernet data frames between device power / data line 46 and port 50, and as a PoD injector that injects power received from device power / data line 46 into channel power / data line 47. Depending on the design of channel power / data line 47, channel power / data line 47 may transmit power and data simultaneously on the same wire, or may transmit power and data on separate wires along at least a portion of power / data line 47. Data line segment 51 may be directly connected to device power / data line 46 and power / data line 47.

[0052] Channel 48 limits the energy transmitted through port 50. Power flowing from power line 46 through channel power line 47 to port 50 flows through intrinsically safe and other safety circuits. The intrinsically safe circuits limit the power transmission in the event of a short circuit or other electrical fault. The safety circuits can be thought of as several power protection modules operating in series and limiting the current and voltage of the power transmitted to the field device through the two-wire spur. APL field switch port designers can vary the order, number, and circuit design of the power protection modules on a port to meet their design and safety requirements.

[0053] The power flowing through the channel power line 47 first flows through a maximum current power protection module 52. The maximum current protection module 52 includes a fuse 54 which limits the absolute maximum current that can flow through the channel power line 47.

[0054] The maximum current power protection module 52 also isolates the channel power lines 47 from the power source connected to the APL field switch. A second fuse can be included in the isolated portion of the channel power lines 47.

[0055] Power flows from maximum current power protection module 52 to current limiting power protection module 56 .

[0056] The current limiting power protection module 56 sets the power class of the channel by setting the maximum current that can flow through the channel power line 47. Several power classes are defined in the APL specification (each power class is associated with a respective maximum power, although the current APL specification power class definitions are subject to change). The power class applicable to an APL field switch channel defines the maximum amount of power in watts at the maximum voltage that can be provided by the channel to the port 50. Power classes A, B, and C are intended for intrinsically safe rated channels in areas with explosive atmospheres, but can also be used on ports that are not intended for intrinsically safe use.

[0057] The current limiting power protection module 56 includes a selectively adjustable current limiting device 58, represented in FIG. 3 as a variable resistor. Possible embodiments of the user adjustable current limiting device are described below. A user can selectively set a maximum current (amperage) that will activate the current limiting device to prevent current from exceeding a set maximum current that can be transmitted through the port 50. User selection of the power class of a channel 48 by setting the maximum current setting of the current limiting device is described in more detail below.

[0058] Power flows from the current limiting power protection module 56 to a voltage power protection module 60. The power protection module 60 blocks overvoltage or surge conditions and can be realized as a crowbar circuit represented by impedance 62. The crowbar circuit operates by providing a short or low resistance path to the voltage output. The crowbar circuit may be implemented using, for example, a thyristor, triac, Trisil, or thyratron as the shorting device.

[0059] 2, the APL field switch 30 includes a power management module 64. The power management module 64 allows a user to set the power class of each channel 48. The power management module 64 includes a microprocessor or central processing unit (CPU) 66 that accesses a storage or memory 68 that holds application software 70 having executable instructions executable by the CPU 66 used to manage both the power class of each channel 48. The memory 68 may be a persistent writeable memory such as an EEROM memory or other type of memory used in embedded systems.

[0060] The power management module may, in a possible embodiment, be implemented as a system-on-chip (SoC) that may include a microcontroller along with other peripherals including a graphics processing unit (GPU), a Wi-Fi module, one or more coprocessors, etc.

[0061] The power management module 64 can determine the power available to the APL field switch. The power management module 64 is operatively connected to the APL terminals 42, 44 and can determine whether a voltage is applied to the terminals. This allows the power management module 64 to determine whether the APL field switch 30 is powered via a network trunk (APL standards limit trunk power supply) or via an external power source having a power rating appropriate for the APL field switch.

[0062] The power management module 64 functions as a controller 64 connected to each current limiting power protection module 56. The controller 64 sets the power class of each port by setting the current limit of the adjustable fuse of each module 54. To allow a user to dynamically set the power class of one or more ports, the controller 64 operating through its operating software 70 receives user input representing one or more ports and a desired power class of the one or more ports, reads the user input, and in response to the user input, sets the current limit of the fuse connected to the port to the current limit associated with the desired power class. The controller 64 can also control the ability of the APL field switch 30 to cascade power downstream through the APL trunk.

[0063] The controller 64 in embodiments of the APL field switch 30 receives user input from a touchpad display on the APL field switch itself, through an interconnecting wired or wireless communication link (such as a serial USB cable, as a non-limiting example) that communicates independently of the process control network, and / or through the process control network itself. To receive user input via the process control network, the controller 64 may be configured to appear as a field device on the process control network.

[0064] The application software 70 in the illustrated embodiment generates a graphical user interface (GUI) 72 for setting the power class of the ports that is sent back to the user. The GUI 72 can be provided, for example, via a web server provided by the application software 70 that displays the GUI on a web page. The controller 64 in the illustrated example transmits the GUI 72 to an application on the engineering workstation 16 via an interconnecting wired or wireless communication line or link 73 that allows two-way communication with the workstation 16. The controller 64 allows the engineer to communicate with the CPU 66 and associated software to change the power class of some or all of the ports 50 of the APL field switch 30. The controller 64 also allows the user to enable or disable the cascade feature of the APL field switch 30.

[0065] The CPU 66 is connected to the selectively adjustable current limiting devices 58 of each channel's current limiting power protection module 56 via an I2C network 74. The I2C network protocol is a commonly used serial communications protocol.

[0066] Selectably adjustable current limiting devices of known types that can be adapted for use in the present disclosure include: an electronic fuse (eFuse) connected to a resistor of selectable resistance; A constant current limiting circuit; a foldback current limiting circuit; A parallel resettable fuse arrangement of different amperage ratings placed in series with a relay that selects which fuse is active; Including, but not limited to:

[0067] An electronic fuse is a fully electronic, selectable, current-limiting fuse that, when activated, stops the flow of electrical current.

[0068] A constant current limiting circuit allows current to pass until a maximum current is reached. The circuit then reduces the voltage to prevent the current from exceeding the maximum current. Figure 4 illustrates an example constant current limiting circuit that can be adapted for use in the present disclosure.

[0069] A foldback current limiting circuit allows current to pass until a maximum current is reached. The circuit reduces the voltage and current to prevent the current from exceeding the maximum current. FIG. 5 illustrates an exemplary foldback current limiting circuit that can be adapted for use in the present disclosure (Image attribution: Mikiemike from English Wikipedia, CC BY-SA 3.0, https: / / commons.wikimedia.org / w / index.php?curid=70852656).

[0070] Current limiting circuits utilize a resistor to set the maximum current that can flow through the circuit. By utilizing variable resistors in the design of these circuits that allow dynamic selection of the resistance value, the maximum current that can flow through the circuit, and therefore the maximum power output of the circuit, can be selected by selecting the resistance value of the resistor.

[0071] The current limiting circuit can also be connected in series with a static switch driver, such as the LTC7003 driver available from Analog Devices, Inc., Wilmington, Massachusetts 01887, USA, which allows for the detection of relatively large voltage drops.

[0072] 6 illustrates the selectable current limiting device 58 formed as a parallel fuse arrangement including a positive temperature coefficient (PTC) resettable fuse that can automatically reopen after cooling. PTC fuses that may be adapted for use in accordance with the present disclosure may be obtained from Eaton Electronics Division, Cleveland, Ohio, USA. The fuses 69 are each connected to a controller 68 and arranged in series with a relay 71 that is controlled by the controller 68. Closing one relay and holding the other open allows the controller 64 to selectably insert a selected one of the fuses 69 into the channel power line 47.

[0073] The current limiting device 58 used with the illustrated APL field switch 30 includes an electronic fuse connected to a digital potentiometer. Electronic fuses offer many advantages for controlling current. Electronic fuses are commercially available as integrated circuit packages from Texas Instruments, Toshiba, STM Microelectronics, and other vendors. Electronic fuses should be selected based on amperage and voltage capacity, speed of response, energy efficiency, etc. Detailed information regarding electronic fuses and their operation is publicly available through product data sheets available from manufacturers (e.g., Texas Instruments Application Report SLVA862A, “Fundamentals of Electronic Fuses,” April 2018; Texas Instruments Publication SLVSDT4E, August 2019, describing the TPS2662x family of electronic fuses; and Texas Instruments Design Guide TIDA-010076, “Daisy Chaining Power and Data over Single Pair Ethernet,” June 2020).

[0074] 7 illustrates an embodiment of user power protection module 56 in which current limiting device 58 includes an electronic fuse 74 connected to a digital potentiometer 76. Electronic fuse 74 is included in channel power line segment 49. Current flowing through channel power line 47 passes through electronic fuse 74. Electronic fuse 74 allows a resistor to be connected to electronic fuse 74 that sets the current limit that opens the electronic fuse. Connecting a variable resistor to electronic fuse 74 allows the current limit to be selectively changed based on a selected resistance value of the variable resistor.

[0075] Digital potentiometer integrated circuits are available from Analog Devices, Microchip, Texas Instruments, and other suppliers.

[0076] The illustrated digital potentiometer 76 includes a resistor ladder 78 and electronic switches 80 at each stage of the ladder. During operation, one switch 80 is closed at a given time to determine the effective resistance of the digital potentiometer (similar to the operation of the wiper of a conventional analog potentiometer).

[0077] The operating state of the set of switches 80 is controlled by a digital potentiometer control unit 82 which is capable of receiving external commands to set the resistance value of the digital potentiometer. Digital potentiometers with control units compatible for connection to I2C and SPI serial networks are commercially available.

[0078] Digital potentiometer 76 allows the resistor value that sets the current limit of the electronic fuse to be selectively varied to open the electronic fuse at different maximum currents and therefore different power classes.

[0079] 8 illustrates current limiting power device 58, where digital potentiometer 76 is set to a relatively high resistance value appropriate for setting channel 48 to a lower power port class. A lower current through electronic fuse 74 causes the electronic fuse to open.

[0080] 9 illustrates a current-limited power protection module 56 in which the digital potentiometer 76 is set to a relatively low resistance value suitable for setting the channel 48 to a higher power port class. To open the electronic fuse, a higher current must flow through the electronic fuse 74 as compared to the resistance state of the digital potentiometer 76 shown in FIG.

[0081] 7, the current limiting device 58 includes a microprocessor or MCU 84 that is connected to a control unit 82 by a UART circuit 86. The MCU 84 communicates with the control unit 82, whereby the control unit 82 sets the desired resistance value of the digital potentiometer 76.

[0082] The MCU 84 is connected to the power management module CPU 66 by an I2C network 74. The application software 70 has access to data applicable to the APL field switches 30 that represents the power class available to each channel 48, the number of channels in the APL field switch, the total power capacity available to the APL field switch, the resistance value of the digital potentiometer associated with each power class, security and user authentication, etc. The CPU 66 can individually address each channel MCU 84 and instruct the MCU 84 to set the desired resistance value of the associated digital potentiometer 76, thereby establishing the power class of the channel requested by the software application 70.

[0083] 10 illustrates a switchable resistor digital potentiometer 77 that can be used in place of the ladder digital potentiometer 76. The switchable resistor digital potentiometer 77 replaces the resistor ladder 78 with several parallel resistors, each in series with a respective programmable switch. The resistors have different resistance values. Each switch can be selectively opened or closed by the control unit 82 to obtain a desired resistance value.

[0084] 11 illustrates a wireframe of an exemplary graphical user interface 72 presented by application software 70. The user interface can be implemented using any number of GUI frameworks available to general computing or embedded computer applications and can be designed according to acceptable best practices for layout, display of information and control, and user interaction.

[0085] The GUI 72, operating through application software 70, can present error messages, display help and login screens, issue events to record GUI usage for archival purposes, and modify data stored in memory 68 to reflect the state of the APL field switches 30.

[0086] The illustrated GUI 72 displays the identity of the APL field switch 30, whether cascading is enabled for the field switch, and the power source for the field switch (transformer or auxiliary power). Cascading can be enabled or disabled via UI switch 88. If the field switch is powered by a power source that does not allow cascading, the GUI will display that cascading is disabled and the UI switch 88 will be disabled as well.

[0087] The GUI 72 displays a data grid 90 with a row of data for each port 50, with each row displaying the respective port channel number and the port's current power class. The power class of a port is changed via a UI control, such as a drop box 92. When the user changes the power class via the GUI 72, the software application detects the change event. The software application 70 verifies that the power class change can be made taking into account the current state of the APL field switches 30. For example, if the power currently supplied to a port 50 uses all of the available power, the application software 70 can prevent the user from changing the power class of the port to a power class with a higher power.

[0088] Once the application software 70 determines that the requested power class change is possible, the application software 70 operating via the CPU 66 and the I2C network 74 communicates with the appropriate channel MCU 84 to change the resistance value of the port's associated digital potentiometer 76 to the resistance value associated with the requested power class. Upon verifying the change in resistance value, the application software 70 can update the GUI 72 to reflect the change in power class of the port and write the channel change to memory 68.

[0089] If the application software 70 determines that the power class cannot be changed, the GUI 72 displays an appropriate error message and the power class is not changed.

[0090] The illustrated GUI 72 also allows the user to reset all or each port 50 to an initial default power class if such resetting is permitted by the application software 70. The GUI 72 may request the controller 64 to change the power class of each port individually and wait for confirmation, or may request the controller 64 to change the power class of multiple ports in a batch operation.

[0091] FIG. 12 illustrates an exemplary wireframe of a software application graphical user interface 94 intended for use with an APL process control network. The software application GUI 94 may be displayed, for example, on an engineering workstation 16. The software application runs through the process control network 10 and requests data from each APL network field switch 30, 32 reflecting the current state of the APL field switch. The software application aggregates the data and presents it via the GUI 94. The illustrated GUI 94 displays a data grid 96 with rows of data for each APL field switch, with each row displaying the APL field switch ID, number of ports, number of active ports, and current power for each APL field switch on the network. Each row also includes an edit link 98 that, when clicked, opens the GUI 72 for the APL field switch associated with that row on the workstation.

[0092] The software application 72 may, in possible embodiments, be designed to run on a CPU that does not form part of the APL field switch.

[0093] 13 illustrates the use of a power protection module 64 forming part of a networked distributed computing system. The computing system includes a server 100 that is networked with the engineering workstations 16. The server 100 also has access to a database 102 that is local with the server. The database is located in the backend and can be hosted in the cloud or on a separate server remote from the server 100.

[0094] In this networked embodiment, server 100 executes some or all of the software functions included in software application 70 described above in order to offload some or all of the computer processing from the APL field switch to the server, some or all of which may be performed in computer hardware located remotely from the APL field switch.

[0095] The application GUI 72 is displayed on the engineering workstation 16. Upon initiation of the application, the engineering workstation 16 queries the APL field switches 30 over the process control network 10 and receives data representing the current state of the APL field switches and field switch channels. User interactions with the GUI 72 are transmitted between the workstation 16 and the server 100. The server 100 determines whether a proposed change in the power class of the channel is possible.

[0096] When the power class of a port is changed, the engineering workstation 16 sends a command to the APL field switch 30 to change the power class of the port. The APL field switch CPU 66 signals the appropriate MCU 84 over the I2C network 74 to change the resistance value of the port channel's digital potentiometer 76 to the resistance value associated with the requested power class. The APL field switch 30 confirms the power class change to the engineering workstation 16 and the GUI 72 is updated to reflect the power class change.

[0097] The server 100 can store data associated with the APL field switches and a history of changes to the APL field switch states in the database 102. The server 100 can query the database 102 for data needed to initially display the GUI 72 instead of querying the APL field switches for that data.

[0098] Other distributed computing architectures are known and can be adapted to offload the required computing power from the APL field switch 30.

[0099] A relay according to the present disclosure may be an analog relay, a transistor relay, a mechanical relay, or an equivalent.

[0100] While the disclosure includes one or more exemplary embodiments described in detail, it will be understood that one or more of the embodiments may each be modified, and the scope of the disclosure is not limited to the exact details described herein, but includes such modifications that would be apparent to one of ordinary skill in the art, including modifications in the number of APL field switch ports, the power feed of the APL field switch, the environment of use, the power limitations of the power classes, and the like, and such modifications and variations are within the scope of the appended claims, but are not limited to such modifications and variations.

Claims

1. 1. An APL field switch for an industrial control network that enables user-selectable dynamic power allocation to connected field devices, comprising: a power terminal and a data terminal, each configured to allow the APL field switch to receive power, the data terminal being further configured to transmit data to the APL field switch at some times and to receive data from the APL field switch at other times; a plurality of channels, each comprising a port and a channel power / data line connecting the port to the power terminal and the data terminal, each port of the plurality of channels configured to be connected to a two-wire APL spur, the APL spur connecting the port to an APL field device, the port being associated with a default power class of a plurality of power classes, the channel power / data line of each channel configured to transmit power from the power terminal to the port and to transmit data between the port and the data terminal, the channel power / data line comprising a power line segment connected to the port and configured to transmit power received from the power terminal to the port; an intrinsic safety circuit and an adjustable power limiting device disposed in series with the power line segment of each channel, the intrinsic safety circuit of each channel limits a maximum power transmission over the power line segment of the channel, the power limiting device of each channel being selectively operable in each of a plurality of operating states, wherein when the power limiting device is in one of the plurality of operating states, each maximum transmission of power through the power limiting device activates the power limiting device, thereby limiting, reducing or stopping the transmission of power over the power line segment, each operating state being associated with a different power class; a controller connected to the power limiting device of each channel of the plurality of channels, the controller comprising controller software embodied in an executable non-transitory computer readable medium for operating the controller, the controller configured to receive user input requesting the controller to set a power class of a selected port of the plurality of channels to a desired power class, and in response to the user input, issue a control signal via a connection to the power limiting device connected to the selected port that sets an operational state of the power limiting device to an operational state associated with the desired power class, thereby allowing a user to selectively change the power class of each port to meet the needs of the industrial control network; and An APL field switch comprising:

2. 2. The APL field switch of claim 1, wherein the APL field switch is capable of making a total maximum power available to the ports of the field device, and the controller is configured not to change the power class of the selected port in response to the user input if changing the power class would cause the maximum power that can be transmitted to the port to exceed the total maximum power available to the APL field switch.

3. the user input is provided from a computer-implemented user interface that is externally accessible to the APL field switch; the user interface is operatively connectable to a database stored on a server remote from the APL field switch, the user interface being configured to store data in and retrieve data from the database required by the user interface to enable a user to selectively allocate power classes among the ports of the plurality of channels; 2. The APL field switch of claim 1, wherein the user interface is configured to display data to a user representing a current power class assigned to the ports of the APL field switch, and to query the APL field switch about the data displayed to the user.

4. the user interface is a graphical user interface (GUI) that lists each port of the plurality of channels and a current power class of each port of the plurality of channels and allows a user to set the desired power class of a selected port of the plurality of channels to generate the user input to the controller; 4. The APL field switch of claim 3, wherein the GUI is generated by the controller software, or the GUI is generated by software stored on an executable non-transitory computer readable medium separate from the controller software.

5. the controller is configured to receive user input requesting the controller to set a power class of each port of the plurality of channels to the default power class of the port, and in response to the user input, issue control signals to the power limiting devices connected to the port that set an operational state of each power limiting device to an operational state associated with the default power class of the port attached to the power limiting device; 4. The APL field switch of claim 3, wherein the user interface is operably connectable to a database, the user interface configured to store data in and retrieve data from the database required by the user interface to enable a user to request the controller to set each port of the plurality of channels to the default power class of the port.

6. the APL field switch includes a first default set of port power class assignments when the APL field switch is powered via the data terminals, and a second default set of port power class assignments different from the first default set when the APL field switch is powered via the power terminals; 6. The APL field switch of claim 5, wherein the controller is configured to set the power classes of the ports of the plurality of channels according to the first default set of port power classes when the APL field switch is powered via the data terminals, and if the controller receives the user input requesting the controller to set the power class of each port to the default power class of the port, set the power classes of the ports of the plurality of channels according to the second default set of port power classes when the APL field switch is powered via the power terminals.

7. 2. The APL field switch of claim 1, wherein the APL field switch is capable of cascading power to another APL field switch, and the controller is configured to receive a user input selectively allowing the APL field switch to cascade power or not allowing the APL field switch to cascade power.

8. 2. The APL field switch of claim 1, wherein each power limiting device of said plurality of channels is a current limiting device.

9. At least one current limiting device of the plurality of channels (a) an electronic fuse; (b) a plurality of PTC fuses arranged in parallel, each PTC fuse being connected to the controller and in series with a relay controlled by the controller; (c) a constant current limiting circuit; and (d) Foldback current limiting circuit and the intrinsically safe circuit of each channel includes a maximum current power protection module that limits a maximum current that can flow through the power line of the channel; 9. The APL field switch of claim 8, wherein the at least one current limiting device comprises the electronic fuse connected to a variable resistor having a resistance value selectable from a plurality of resistance values, the variable resistor being a digital potentiometer, and further wherein the digital potentiometer is either a ladder type digital potentiometer or a relay type digital potentiometer.

10. The controller: (a) setting the power class of each port of the plurality of channels to a respective default power class; and / or (b) receiving an input signal via at least one of: (aa) a wired or wireless connection independent of said data terminal; and (bb) a connection that transmits said input signal through said data terminal of said APL field switch.

2. The APL field switch of claim 1, configured as follows:

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