METHOD AND APPARATUS FOR CHANGING POWER CLASS FOR A POWERED DEVICE

• US 20100049998A1
• Filed: 10/30/2009
• Published: 02/25/2010
• Est. Priority Date: 03/14/2006
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Thomas, Robert, Karam, Roger
• Granted Patent: US 8,171,315 B2
• Time in Patent Office: Days
• US Class Current: 713/300
• CPC Class Codes: H04L 12/10 Current supply arrangements

Abstract

A method and apparatus for changing power class for a powered device are provided. During operation, a powered device, such as an IP telephone, receives power from a power source via a PoE device. In the event that the powered device detects connection to a second powered device, such as an IP telephone module, the powered device transmits a classification signal to the power source. Based upon the classification signal, the power source performs a powered device classification procedure to reclassify the powered device, such as according to an IEEE 802.3af standard, and provide an increase amount of power to the powered device. The powered device, in turn, provides a portion of the power to the modular device. The modular powered device, therefore, receives power directly from the first powered device and does not require additional equipment in order to operate.

Claims

1. A method of applying inline power from power source equipment to powered devices via a communications medium, the method comprising:

receiving a first classification signal from a first powered device via the communications medium, the first classification signal indicating a power class of the first powered device;

allocating a first amount of power to the first powered device based on the first classification signal;

receiving a second classification signal from the first powered device via the communications medium, the second classification signal indicating a combined power class of a combination of the first powered device and a second powered device coupled to the first powered device;

allocating a second amount of power to the first powered device based on the second classification signal to reflect the power requirements of both the first powered device and the second powered device; and

supplying power from the power source equipment to the first powered device and the second powered device in accordance with the allocated second amount of power.

2. The method as recited in claim 1, wherein the step of allocating the first amount of power includes setting a maximum power threshold that the power source equipment is allowed to deliver to the first powered device, and wherein an actual amount of power supplied from the power source equipment to the first powered device is less than the maximum power threshold.

3. The method as recited in claim 2,

wherein the maximum power threshold is a first maximum power threshold,

wherein allocating the second amount of power includes setting a second maximum power threshold that the power source equipment is allowed to deliver to the first powered device for powering the first powered device and the second powered device, and

wherein an actual amount of power supplied from the power source equipment for powering the first powered device and the second powered device is less than the second maximum power threshold.

4. The method as recited in claim 3, wherein the first maximum power threshold is less than the second maximum power threshold.

5. The method as recited in claim 1, wherein the first powered device is constructed and arranged to operate as power source equipment to the second powered device.

6. The method as recited in claim 1, wherein the second classification signal is a modulated current signal, and further comprising the power source equipment decoding the modulated current signal.

7. The method as recited in claim 6, wherein the second classification signal is a modulated under-current signal comprising current pulses that pulse current drawn from the first powered device below an undercurrent threshold.

8. The method as recited in claim 1, further comprising the power source equipment continuously monitoring the first powered device for detecting the second classification signal.

9. The method as recited in claim 1, wherein the first classification signal is indicative of a plurality of power classes each prescribing a maximum current threshold, the method further comprising:

dynamically changing the allocated second amount of power responsive to the power supplied in the supplying step crossing the maximum current threshold of at least one of the plurality of power classes.

10. The method as recited in claim 9, wherein the supplying step includes monitoring the power supplied for powering the first powered device and the second powered device, and wherein the step of dynamically changing the allocated second amount of power is based on the monitored power supplied in the supplying step.

11. A powered device for an inline power network, the powered device comprising:

a first port for coupling the powered device to power source equipment;

a second port for coupling the powered device to a modular device;

a classification circuit coupled to the first port and to the second port, the classification circuit constructed and arranged (i) to output a classification signal, indicative of a power class of the powered device, to power source equipment via the first port, and (ii) to receive a connection signal, indicative of a coupling of the modular device to the powered device, from the modular device via the second port; and

user circuitry constructed and arranged for receiving input from a user, the user circuitry being operable to disable power to the powered device and to direct the classification circuit to output to the power source equipment via the first port a classification signal indicative of a combined power class of the powered device and the modular device.

12. The powered device as recited in claim 11, wherein the user circuitry comprises a user-actuable switch.

13. The powered device as recited in claim 11, further comprising a display constructed and arranged for alerting a user to provide input to the user circuitry.

14. The powered device as recited in claim 11, wherein the classification circuit is constructed and arranged to communicate with the power source equipment using an auto-negotiation mechanism.

15. A method of powering a powered device coupled to a modular device, which receive power from power source equipment in an inline power network, the method comprising:

operating a user-operable circuit disposed in one of the powered device and the modular device;

outputting, responsive to an operation of the user-operable circuit, a classification signal to the power source equipment via the inline power network, the classification signal being indicative of a combined power class of the powered device and the modular device;

receiving power, from the power source equipment through the inline power network, in accordance with the combined power class of the powered device and modular device; and

powering both the powered device and the modular device with the received power.

16. The method as recited in claim 15, wherein the user-operable circuit is a switch in the powered device, the method further comprising temporarily disabling power to the powered device from the power source equipment responsive to a user activating the switch.

17. The method as recited in claim 15, wherein the step of operating the user-operable circuit comprises actuating a switch in the modular device, the method further comprising power cycling the powered device and/or the modular device responsive to actuation of the switch.

18. The method as recited in claim 15, wherein the step of operating the user-operable circuit comprises entering a code in the modular device.

19. The method as recited in claim 15, wherein the step of outputting the classification signal comprises outputting a signal indicative of a plurality of combined power classes of the powered device and the modular device.

20. The method as recited in claim 19, further comprising the powered device dynamically signaling the power source equipment to inform the power source equipment of a prior or expected change in combined power requirements of the powered device and modular device from one power class to another.