Measuring cable resistance in system for providing power over communication cable
AssigneeLinear Technology Corporation
InventorsJeffrey Lynn Heath, John Arthur Stineman, Jr., Steve Robbins
Life of this patent
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Abstract
A system for providing power to a powered device over a communication cable has a cable resistance measuring mechanism that determines values of response signals detected in response to supplying each of at least three reference signals over the communication cable, and determines the resistance of a pair of wires in the cable based on these values. The cable resistance measuring mechanism may be configured for determining resistance of an Ethernet cable that delivers power to the powered device in a Power over Ethernet system.
Claims23
A system for providing power to a powered device over a communication cable, the system comprising a cable resistance measuring mechanism configured for:
- determining a value of a first response signal detected in response to a first reference signal supplied over the communication cable,
- determining a value of a second response signal detected in response to a second reference signal supplied over the communication cable,
- determining a value of a third response signal detected in response to a third reference signal supplied over the communication cable, where the first, second and third reference signals differ with respect to each other, and
- determining resistance of a pair of wires in the cable based on values of the first second and third response signals and values of the first, second and third reference signals,
- the resistance being determined without measurement operations performed on a powered device side of the communication cable.
A method of determining resistance of a communications cable in a system for supplying power to a powered device over the communications cable, the method comprising the steps of:
- determining values of response signals detected in response to supplying a number of reference signals over the communication cable, and
- determining resistance of the cable based on the determined values of the response signals,
- wherein the number of the reference signals is selected to account for changes in the response signals caused by circuit elements on a powered device side of the cable, and
- the resistance is determined without measurement operations performed on the powered device side of the communication cable.
A Power over Ethernet system for delivering power from a power sourcing equipment (PSE) to a powered device (PD) over a cable having first and second pairs of wires configured for supplying the power to the powered device, and at least one spare pair of wires, the system comprising:
- a power supply configured for supplying the power over the first and second pairs,
- a reference signal source configured for injecting at least three reference signals onto the spare pair, the reference signals differ with respect to each other, and
- a response signal detector configured for detecting a response to each of the three reference signals to determine resistance of the cable,
- the resistance being determined without measurement operations performed on a powered device side of the communication cable.
A local area network comprising:
- at least a pair of network nodes,
- a network hub, and
- a communication cable for connecting the network nodes to the network hub to provide data communications, the communication cable having power pairs of wires and a spare pair of wires,
- the network hub having a power supply device for providing power to a load over the power pairs of wires, the network including a measurement mechanism for determining resistance of the cable, the measurement mechanism comprising:
- a reference signal source configured for injecting a number of reference signals onto the spare pair, the reference signals differ with respect to each other, and
- a response signal detector configured for detecting a response at the spare pair to each of the reference signals to determine resistance of the cable,
- the resistance being determined without measurement operations performed on a load side of the communication cable.
Dependencies are inferred from the claim text.