Power distribution to nodes in a distributed system

[0002] 1. Field of Invention

[0003] The present invention pertains to the field of distributed systems. More particularly, this invention relates to power distribution to nodes in a distributed system.

[0004] 2. Art Background

[0005] Distributed systems such as distributed control systems are commonly arranged as a collection of nodes which are interconnected via one or more network communication links. The network communication links may be arranged using one or more intervening communication devices such as repeaters, switching hubs, or gateways. Nodes that are interconnected via network communication links may be referred to as remote nodes.

[0006] One prior method for providing electrical power to remote nodes is to route dedicated power lines throughout the distributed system to the remote nodes. Unfortunately, the routing of dedicated power lines usually increases the cost installing and maintaining a distributed system.

[0007] Another method for providing power to remote nodes is to provide each remote node with its own power supply such as a battery or a power supply driven by an AC power source. Unfortunately, providing each remote node with its own power supply usually increases the cost of each remote node and increases the overall cost of a distributed control system.

[0008] Another method for providing power to remote nodes is to superimpose the signaling required for communication with the remote nodes onto the conductors that supply power to the remote nodes. Unfortunately, such a method usually increases the cost of the remote nodes. In addition, such a method usually increases the complexity of the communication circuitry in the remote nodes and may limit performance.

[0009] A system is disclosed in which remote nodes are supplied with electrical power using existing network communication links. A communication device in a system according to the present techniques routes electrical power to a remote node via a set of unused lines of a network communication link used for communication with the remote node. The electrical power distributed to the remote nodes may be AC or DC power. The system routes electrical power to remote nodes via a set of lines in the same cable bundle as communication signal lines. This saves wiring costs and installation costs.

[0010] Other features and advantages of the present invention will be apparent from the detailed description that follows.

[0011] The present invention is described with respect to particular exemplary embodiments thereof and reference is accordingly made to the drawings in which:

[0012] FIG. 1 shows a distributed system in which electrical power is routed to a remote node via previously unused lines of a network communication link which is also used for communication to the remote node;

[0013] FIG. 2 illustrates one embodiment of a communication device which distributes power via communication links;

[0014] FIG. 3 illustrates another embodiment of a communication device which distributes power via communication links;

[0015] FIG. 4 illustrates yet another embodiment of a communication device which distributes power via communication links using a switching circuit;

[0016] FIG. 5 shows one embodiment of a remote node which obtains a voltage potential V_nvia unused lines of a network communication link.

[0017] FIG. 1 shows a distributed system 100 in which electrical power is routed to a remote node 20 via previously unused lines of a network communication link 30 which is also used for communication to the remote node 20. The distributed system 100 includes a communication device 12 that enables communication to the remote node 20 via the network communication link 30 and that includes mechanisms for distributing electrical power to the remote node 20.

[0018] The network communication link 30 conforms to a particular standard that includes a set of transmit data lines 40, a set of receive data lines 42, and a set of unused lines 44. The transmit data lines 40 and the receive data lines 42 are used for communication between the communication device 12 and the remote node 20. The communication device 12 uses lines 44 which are unused according to the particular standard to route power to the remote node 20.

[0019] The network communication link 30 may be any type of communication path that has unused signal lines which may be defined by an industry standard.

[0020] The lines 44 may be selected to replace a portion of the communication capability of the communication link 30. For example, the replaced capability may be full duplex transmission. This nevertheless yields the ability to power remote nodes while retaining substantially all of the communication capability of the communication link 30. For example, the capability of half duplex transmission may be retained. As another example, a 100 megahertz Ethernet line may be use to provide power as well as 10Base-T operation.

[0021] In one embodiment, the network communication link 30 is an Ethernet 10Base-T link in which lines 4,5 and 7,8 are normally unused lines according to the 10Base-T standard and are used as the lines 44 to supply power to the remote node 20. In another embodiment, the network communication link 30 is an Ethernet 10Base-T link in which two of its normally unused lines 4,5 and 7,8 are the lines 44 that are used to supply power to the remote node 20.

[0022] The use of all four of the lines 4,5 and 7,8 as the lines 44 may be preferable in that this would increase the current carrying capacity of the lines 44 and reduce the voltage drop of the lines 44 for long lengths of the network communication link 30.

[0023] For example, the lines 4,5 may be a common line while the lines 7,8 provide a voltage potential V_nto the remote node 20. Similar alternative arrangements of the lines 4,5 and 7,8 may be used.

[0024] For embodiments in which the remote node 20 requires multiple supply voltages the lines 4,5 and 7,8 may be subdivided to carry multiple supply voltages. For example, lines 4,5 may be a common line while the line 7 carries a voltage potential V_n1and the line 8 carries a voltage potential V_n2to the remote node 20. Alternatively, the lines 4,5 and 7,8 may be used to carry a single voltage potential V_nto the remote node 20 and circuitry may be provided in the remote node 20 for converting the voltage potential V_ninto the voltage levels V_n1and V_n2and possibly other levels depending on the needs of the remote node 20.

[0025] In one embodiment, the lines 44 are used to route DC power to the remote node 20. In another embodiment, the lines 44 are used to route AC power to the remote node 20.

[0026] The communication device 12 is powered by a voltage source V_s. In one embodiment, the voltage source V_sis a DC voltage source. In another embodiment, the voltage source V_sis an AC voltage source.

[0027] The remote node 20 may be any type of remote node in a distributed system. For example, the remote node 20 may be a sensor remote node or an actuator remote node or an application controller remote node or a remote node that is a combination of any of these in the distributed system 100. In addition, the remote node 20 may be a computer system such as a personal computer.

[0028] The communication device 12 may be any device capable of communication on the network communication link 30. The communication device 12 in one embodiment is a repeater which includes circuitry for receiving communication packets via the network communication link 30 and for retransmitting the communication packets via additional network communication links (not shown). In other embodiments, the communication device 12 may include circuitry for gateway functions or router or switching hub or similar functions. The communication device 12 may be a PC network card or a remote sensor or actuator or application controller remote node of the distributed system 100.

[0029] FIG. 2 illustrates one embodiment of the communication device 12. In this embodiment, the communication device 12 is a switching hub that provides communication among the network communication link 30 and a set of additional network communication links 32-34 and also distributes power to the remote nodes connected to the network communication links 30-34.

[0030] The communication device 12 is powered by a voltage source V_s. The voltage source V_smay generate a DC voltage which is distributed as the voltage potential V_ndirectly via the network communication links 30-34. A voltage regulator 14 uses the voltage source V_sto provide a supply voltage V_ccfor application specific circuitry (not shown) in the communication device 12.

[0031] Alternatively, the voltage source V_smay generate an AC voltage which is distributed directly via the network communication links 30-34 as the voltage potential V_n. In this alternative embodiment, the voltage regulator 14 is replaced by a power supply that transforms, rectifies, and filters the voltage source V_sto provide the supply voltage V_cc.

[0032] FIG. 3 illustrates another embodiment of the communication device 12 which is a switching hub that provides communication among the network communication links 30-34 and also distributes power to the remote nodes connected to the network communication links 30-34. In this embodiment, the voltage source V_sgenerates an AC voltage which is transformed, rectified, and filtered by a power supply 16 to provide the supply voltage V_ccfor the circuitry in the communication device 12 and the voltage potential V_nfor distribution via the network communication links 30-34.

[0033] FIG. 4 illustrates yet another embodiment of the communication device 12 which includes a switching circuit 18 that distributes the voltage potential V_nto the remote nodes connected to the network communication links 30-34. The switching circuit 18 may include current limiting circuitry that prevents short circuits in the network communication links 30-34 or the remote nodes connected thereto from affecting the voltage potential V_n.

[0034] The switching circuit 18 may include circuitry for sensing short circuits on a set of power lines 50-54 that are connected to the unused lines of the network communication links 30-34. The communication device 12 includes a microprocessor 22 that obtains information regarding short circuits via a signal path 24. The microprocessor 22 may light LEDs (not shown) to indicate short circuits on the power lines 50-54. The microprocessor 22 may send a message via a communication path 26 to notify other elements of a system of the occurrence of short circuits on the power lines 50-54.

[0035] FIG. 5 shows one embodiment of the remote node 20 which obtains the voltage potential V_nvia the lines 44 of the network communication link 30. In an embodiment in which the voltage potential V_nis DC, a voltage regulator 60 uses the voltage potential V_nto provide a supply voltage V for application specific circuitry (not shown) in the remote node 20. In an embodiment in which the voltage potential V_nis AC, the voltage regulator 60 is replaced by a power supply that transforms, rectifies, and filters the voltage potential V_nto provide the supply voltage V.

[0036] In order to minimize to occurrence of ground loops between the communication device 12 and the remote node 20 via the lines 44 and an earth ground, it is preferable to maintain a high degree of isolation, such as 1500 V, between the common junctions in the communication device 12 and the remote node 20 and the earth ground. For example, a ground 62 for the circuitry in the remote node 20 is electrically isolated from the earth ground. The circuitry of the communication device 12 may be connected to earth ground to provide single point grounding of the system. If there is more than one communication device in the system then one may be connected to earth ground while the others may maintain a high degree of isolation from earth ground. If the earth ground is connected to the ground 62 then an isolating power supply having a transformer could be used in the remote node 20 to prevent ground loop currents.

[0037] The network communication link 30 may be embodied in a cable that contains as a set of electrical conductors that provide the lines 40-44. The electrical conductors may be surrounded by a shield layer which is connected to the earth ground. The shield layer may have an outer insulating layer with distinctive markings such as a particular color or colors that indicate that the cable carries electrical power as well as communication signals. The ends of the cables may have special connectors which are keyed to special receptacles on the communication device 12 and the remote node 20. This may be used to prevent, for example, conventional 10base-T remote nodes from being connected to powered 10base-T cables.

[0038] The foregoing detailed description of the present invention is provided for the purposes of illustration and is not intended to be exhaustive or to limit the invention to the precise embodiment disclosed. Accordingly, the scope of the present invention is defined by the appended claims.