Fail-safe inline power in a wired data telecommunications network

• US 20060262713A1
• Filed: 05/18/2005
• Published: 11/23/2006
• Est. Priority Date: 05/18/2005
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Karam, Roger A.
• Granted Patent: US 8,149,683 B2
• Time in Patent Office: Days
• US Class Current: 370/200
• CPC Class Codes: H04L 12/10 Current supply arrangements

Abstract

A dynamic fuse element is provided in an inline power circuit to provide an electrical current protection level that varies in accordance with allocated current levels and that can respond to current spikes that are not expected. The dynamic fuse element comprises a processor aware of allocated current levels and an inline switch controlled by the processor to turn OFF in the event of a fault. In another aspect ferrite fuses may be provided for relatively low-current applications. In yet another aspect test fuses may be placed on the circuit board to verify that fuses used in manufacture operate at a certain current level.

Claims

1. A monitoring circuit for inline power supply circuitry, the circuit comprising:

a current monitor measuring current supplied to the inline power supply circuitry;

a processor associated with the inline power supply circuitry, the processor tracking inline power allocated to the inline power supply control circuitry and coupled to receive current measurements from said current monitor;

a current control device coupling the inline power supply circuitry to a power supply, the current control device regulating current flow from the power supply to the inline power supply circuitry, the current control device controlled by said processor;

the processor configured to reduce current flow through the current control device in response to detecting a current condition in the current drawn by the inline power supply circuitry.

2. The monitoring circuit of claim 1, wherein the current condition is that the current drawn by the inline power supply circuitry exceeds a total allocated current level associated with the inline power supply circuitry.

3. The monitoring circuit of claim 1, wherein the current condition is that a change in current drawn per unit time by the inline power supply circuitry exceeds a predetermined threshold current level.

4. The monitoring circuit of claim 1, further comprising a notification transmitter responsive to the current condition to transmit a notification to a recipient.

5. The monitoring circuit of claim 2, further comprising a notification transmitter responsive to the current condition to store system status to memory and transmit a notification to a recipient.

6. The monitoring circuit of claim 3, further comprising a notification transmitter responsive to the current condition to transmit a notification to a recipient.

7. The monitoring circuit of claim 1, wherein the current control device is a switch.

8. The monitoring circuit of claim 1, wherein the current control device is a transistor.

10. The monitoring circuit of claim 1, further comprising:

one or more ferrite devices selected to have a combined maximum current rating approximately that of a desired current limit of the inline power supply circuitry, the ferrite device(s) disposed between the power supply and the inline power supply circuitry.

9. A circuit for providing inline power from a power supply to inline power supply circuitry powering a port of a wired data telecommunications device, the circuit comprising:

one or more ferrite devices selected to have a combined maximum current rating approximately that of a desired current limit of the inline power supply circuitry, the ferrite device(s) disposed between the power supply and the inline power supply circuitry.

11. A circuit board for a wired data telecommunications device comprising:

a plurality of inline power circuits coupled to a corresponding plurality of ports, each inline power circuit including at least one fuse having a predetermined current rating; and

a test location disposed on the circuit board, the test location having at least one same fuse disposed thereat for verification of fuse current rating during a test procedure.

12. A method for monitoring current provided to inline power supply circuitry from a power supply having a total maximum current supply capacity, the method comprising:

allocating certain maximum current values to individual inline power supply circuits supplied by the power supply;

accumulating a total allocated maximum current value by summing the maximum current values allocated to the individual power supply circuits;

measuring a total current supplied to the individual inline power supply circuits;

comparing the accumulated total maximum current value with the measured total current;

regulating current flow from the power supply to the inline power supply circuits in response to said comparing step determining that the measured total current exceeds the accumulated total maximum current value by a predetermined threshold.

13. The method of claim 12, wherein the predetermined threshold is zero.

14. The method of claim 12, wherein the predetermined threshold includes an offset to account for current used by the inline power supply circuitry itself.

15. The method of claim 12, further comprising:

transmitting a notification to a recipient in response to said regulating.

16. The method of claim 12, further comprising:

using one or more ferrite devices selected to have a combined maximum current rating approximately that of a desired current limit of an individual inline power supply circuit to limit current to said individual inline power supply circuit.

17. The method of claim 16, wherein said one or more ferrite devices are disposed between the power supply and the individual inline power supply circuit.

18. A method for providing inline power from a power supply to an individual inline power supply circuit powering a port of a wired data telecommunications device, the method comprising:

providing between the power supply and the individual inline power supply circuit one or more ferrite devices selected to have a combined maximum current rating approximately that of a desired current limit of the individual inline power supply circuit.

19. A method for verifying the current rating of fuses disposed on a manufactured printed circuit board comprising a plurality of inline power circuits, each of the inline power circuits including a fuse having a specified current rating, the method comprising:

providing a test location on the printed circuit board, the test location having pads to which a fuse may be mounted and test contacts in respective electrical contact with the pads;

mounting a fuse to the test location;

applying a current through the test contacts to the fuse;

monitoring current flow through the fuse; and

ramping the current applied to the fuse to determine a current level at which the fuse stops conducting.

20. The method of claim 19, further comprising:

determining if the current level at which the fuse stops conducting corresponds to the specified current rating.

21. An apparatus for monitoring current provided to inline power supply circuitry from a power supply having a total maximum current supply capacity, the apparatus comprising:

means for allocating certain maximum current values to individual inline power supply circuits supplied by the power supply;

means for accumulating a total allocated maximum current value by summing the maximum current values allocated to the individual inline power supply circuits;

means for measuring a total current supplied to the individual inline power supply circuits;

means for comparing the accumulated total maximum current value with the measured total current;

means for regulating current flow from the power supply to the inline power supply circuits in response to a determination by said means for comparing that the measured total current exceeds the accumulated total maximum current value by a predetermined threshold.

22. An apparatus for providing inline power from a power supply, comprising:

means for routing power from the power supply to a node and from the node to an individual inline power supply circuit powering a port of a wired data telecommunications device, the apparatus comprising;

means disposed at the node for limiting current flow from the power supply to the inline power supply circuit, said means for limiting implemented by providing at the node one or more ferrite devices selected to have a combined maximum current rating approximately that of a desired current limit of the individual inline power supply circuit.

23. An apparatus for verifying the current rating of fuses disposed on a manufactured printed circuit board comprising a plurality of inline power circuits, each of the inline power circuits including a fuse having a specified current rating, the apparatus comprising:

means for providing a test location on the printed circuit board, the test location having pads to which a fuse may be mounted and test contacts in respective electrical contact with the pads;

means for mounting a fuse to the test location;

means for applying a current through the test contacts to the fuse;

means for monitoring current flow through the fuse; and

means for ramping the current applied to the fuse to determine a current level at which the fuse stops conducting.