Method and system for managing power delivery for power over Ethernet systems

A method for managing the delivery of power for a plurality of devices includes allocating a power limit for each of the plurality of devices and providing power to at least one of the plurality of devices. The method also includes, in response to the providing of power, measuring the amount of power utilized by each of at least one of the at least one of the plurality of devices and determining that the amount of power exceeds the power limit for the device.

TECHNICAL FIELD OF THE INVENTION

This invention relates generally to power supply systems and more particularly to a method and system for managing the delivery of power for power over Ethernet (PoE) systems.

BACKGROUND

Power over Ethernet systems are seeing increasing use in today's society. Power over Ethernet, sometimes abbreviated PoE, refers to providing power to Ethernet devices over an Ethernet line that is also used to communicate data. Thus, power over Ethernet devices do not require separate power supply lines. In some instances, the power may be supplied by a power supply contained within an Ethernet switch. Because the power supply does not generally have the power capability to supply maximum power to every port, there is a limit on the number of power over Ethernet devices that can be connected to a given power supply. A port may be denied power, if it will result in oversubscription of the power supply. Example power over Ethernet devices that can benefit from receiving power over the Ethernet communication lines include an internet protocol telephone, a badge reader, a wireless access point, a video camera, and others.

Traditionally, when a power over Ethernet device is connected to a power supply, the power over Ethernet device is allocated a maximum power class according to IEEE standard 802.3af denoted as class 0 thru 4. These maximum values correspond to the maximum amount of power that will be supplied by the power supply to the power over Ethernet device. IEEE standard 802.3af provides for three levels of 15.4 watts, 7.5 watts, and 4.0 watts for these power over Ethernet devices. In certain circumstances, such allocation prevents the power supply from being utilized to its full capability due to the coarse granularity in class.

A software program referred to as Cisco Discovery Protocol allows for more granular specification of the limit for the power over Ethernet powered devices other than the above-described IEEE levels. However, the power supply still may have unutilized capacity.

SUMMARY OF THE INVENTION

A method for managing the power provided for a plurality of devices includes allocating a power limit for each of the plurality of devices and providing power to at least one of the plurality of devices. The method also includes, in response to the providing of power, determining the amount of power utilized by each of at least one of the at least one of the plurality of devices and determining that the amount of power exceeds the power limit for the device.

Embodiments of the invention provide numerous technical advantages. Some, none, or all of the embodiments may benefit from the following advantages. According to one embodiment of the invention, powered devices in a power over Ethernet system may be oversubscribed because a user specified power limit for the device may be utilized in combination with monitoring of the power utilized by that device and adjustment of its limit. Thus, where the power supply is not being utilized to its full capacity, the power limit for a particular device may be increased to allow for additional power requirements of that device. This allows greater use of the full capability of a power supply. According to another embodiment, greater usage of a power supply may be achieved by oversubscribing a power supply in conjunction with measurement of the overall usage of the power supplied by the power supply. If the overall usage exceeds a specified level, power may be terminated to one or more of the power devices until acceptable usage levels are met.

Other advantages may be readily apparent to those skilled in the art.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Embodiments of the invention are best understood by referring toFIGS. 1 through 5Bof the drawings, like numerals being used for like and corresponding parts of the various drawings.

FIG. 1is a block diagram of a system10associated with the provision of power to a plurality of power over Ethernet devices. System10includes power over Ethernet power source equipment12, which provides power to a plurality of power over Ethernet powered devices22. Associated with power over Ethernet power source equipment12is a control system14. Control system14manages the provisioning of power by power over Ethernet power source equipment12to powered devices22. Power over Ethernet power source equipment12includes a power supply16associated with a plurality of ports18. In this embodiment, each port18has an associated programmable power monitor20that monitors the power supplied over that port to the respective power device22. Control system14may increase the user specified power limit for each device in response to a determination that the particular device is utilizing more power than its specified limit. Control system14also compares the sums of the power supplied to the plurality of powered devices22against the capacity of the power supply16, to determine if there exists additional capacity to provide more power to powered devices22or if the system limit is exceeded. This allows oversubscription of power supply16. Also illustrated inFIG. 1is a user interface15.

User interface15allows a user to specify a power limit for each power over Ethernet powered device22. This power limit specifies the maximum amount of power that power over Ethernet powered device22should receive. However, it may be the case that any given power over Ethernet powered device22may actually require more power than its user defined maximum limit. User interface15may be implemented in software or hardware and allows a user to enter power limits for powered devices22. This allows a user to specify the expected power use of a particular powered device22which may or may not fall near conventional IEEE levels. By allowing user specification of the expected power usage of each of the plurality of powered devices, oversubscription for power supply16may occur. This advantage allows for the maximum utilization of power supply16. In some embodiments, power over Ethernet power source equipment12may include an overall power monitor that measures the overall power supplied by power supply16at any given time to powered devices22.

Control system14may be implemented in software or hardware. One example of a software embodiment is described in greater detail in conjunction withFIG. 2. Control system14allows the configuring of power limits for each device by a user, in conjunction with user interface15. This configured value may differ from the conventional IEEE values of 15.4 watts, 7.5 watts, or 4.0 watts. This provides one advantage of allowing more granular control of the power limits for particular devices, particularly devices whose maximum power requirements do not fall near one of the three IEEE levels.

Power supply16provides power for the plurality of ports18and then to the plurality of power over Ethernet powered devices22. Although any suitable power supply may be used, one example is a370watt,50V, isolated power supply manufactured by Delta Electronics. Although illustrated as a single power supply, power over Ethernet power supply equipment may incorporate multiple power supplies16.

Ports18correspond in a one-to-one fashion to the respective ones of the plurality of power over Ethernet powered devices22. One example of ports18is conventionally known in the industry and is therefore not described here in greater detail. However, it should be emphasized that unconventional ports18may also be utilized without departing from the scope of the present invention.

Programmable power monitors20measure the amount of power being utilized and supplied to respective ones of power over Ethernet powered devices22. Programmable power monitors20may be implemented by hardware or software but in one particular embodiment utilities hardware. Programmable power monitors20may store the power limit associated with the respective powered device22; however, the limit may be stored in other locations, including within control system14. The measurement portion of programmable power monitor20, according to one example, may be formed according to conventional techniques, which are well known and is not described here for simplicity of description. However, it is noted that programmable power monitor may measure power utilized by the associated powered device22by making both current and voltage measurements, or by making current measurements only and assuming a known power supply16output voltage. Unconventional power measurement techniques may also be used to the power measurement portion of programmable power monitor20.

Powered devices22may be any power over Ethernet device that requires power. Examples include an internet protocol phone, a wireless access point, a video camera, and a badge reader.

In operation, power supply16provides power through ports18to one or more of power devices22. Programmable power monitors20measure the amount of power supplied to the respective ones of power over Ethernet powered devices22. If it is determined that a particular one of the power over Ethernet devices22exceeds its specified power limit, programmable power monitor communicates with control system14over lines21informing control system14that a particular power over Ethernet device is exceeding its power limit. Control system14also receives the amount of power being drawn by each power device from programmable power monitors20. In response to the determination that a particular power over Ethernet device22is exceeding its power limit, control system14determines whether power supply16is exceeding its maximum power limit or whether additional power capability exists. If additional power capability exists, then control system14may modify the power limit associated with a particular power over Ethernet powered device22, allowing that device to receive additional power without creating a fault condition. Control system14may make this determination that power supply16is operating within its overall power limit by adding the power usage of each of the power over Ethernet devices22, or alternatively, through use of an overall power monitor, as described above. In one embodiment, in response to control system14determining that the capacity of the power supply is exceeded, control system14removes power from at least one of at least one of the power over Ethernet powered devices22. The determination of which ones to remove power from is according to the configuration of control system14, which may be modified by user interface15.

In this manner, system10can be configured with nominal values for each of the plurality of power over Ethernet devices but adjustments may be made that represent the actual use. In this manner such a system can be safely oversubscribed.

FIG. 2is a block diagram of one example of control system14. In this example control system14is implemented through use of a software program. In this example, control system14includes a processor24, memory26, and storage28. Memory26may store a control application30as well as power limits32. The operation of control application30is described in greater detail below in conjunction withFIG. 3; however, it should be emphasized that, although the method ofFIG. 3is described in the context of control application30, such a method could be implemented by other means such as through hardware. Storage28provides additional storage that may be utilized by processor24in executing control application30. Processor24may take any suitable form including custom processors or off-the-shelf processors. It is also emphasized that the entire control system14also may be implemented in hardware, such as through an application-specific integrated circuit.

FIG. 3is a flowchart illustrating example steps associated with providing power to a plurality of Ethernet devices according to the teachings of the invention. In one example, unless the context indicates otherwise, these steps may be performed by control system14; however, they may also be performed by suitable hardware or software such as by programmable power monitors20having suitable logic for implementing these described steps. The method50begins at step52. At step54a power limit is allocated for each power over Ethernet powered device22. This may be performed automatically by control system14, by a user through user interface15, or through other suitable methods. According to the teachings of the invention, the allocated power limit for each device may include values other than those specified by IEEE, which are 15.4 watts, 7.5 watts, and 4.0 watts; however, these power limits may also be utilized.

After allocation of a power limit for each device, power is provided to any device requiring power at step56. The power limit allocated for each device may be stored in control system14or may also be stored in programmable power monitors20, or in other suitable locations. At step58, power usage for each device is measured. In the example ofFIG. 1, such power usage is measured by programmable powered monitors20.

At step60a determination is made of whether the power usage for any powered Ethernet device exceeds the limit for that device. If not, processing continues at step58in which power usage is continually monitored for each of the power over Ethernet devices. However, if at step60it is determined that the power usage for any particular device is exceeded, then it is determined whether the overall power limit for power supply16is exceeded at step64. This determination may be based upon an overall power usage determination that occurs independently of this method or may involve specifically determining the power usage for this purpose, as indicated at step62. Such determination of an overall power usage may involve measuring the overall power usage or measuring power usage for each power over Ethernet device22and summing that usage.

If the overall usage is exceeded, then power may be terminated to the device22that exceeds its particular limit, as noted at step66. In that event, control system14may remove a fault condition that resulted from the power over Ethernet device22exceeding its power limit. Additionally, a user may be informed that power has been discontinued to the power over Ethernet device22. To allow the particular power over Ethernet device22to resume operation, its power limit may be reconfigured before power is supplied to that device again.

The result of step64indicates that the overall limit for the power supply16is not exceeded, then the power limit for the particular power over Ethernet device22may be increased, allowing that device to receive more power than it was originally allocated. As an alternative, control system14may be configured to not allow a preset power limit to be increased in which case processing would proceed as described above with respect to step66. However, if the power limit is increased at step68, the power limit may be increased to any suitable amount including those specified by the IEEE 802.3af standard or other values. Processing continues after step66and step68at step58in which power usage for each device is continually monitored.

FIG. 4is a block diagram illustrating an alternative embodiment of a system110for providing power for a plurality of power over Ethernet devices. System110is similar to system10with like components having analogous reference numerals. However, power over Ethernet power supply equipment112includes an overall power monitor117that measures the overall amount of power supplied by power supply116to the plurality of power over Ethernet devices122. Power monitor117may utilize any appropriate method of measuring power delivered by power supply116. This method may include both a current and a voltage measurement or a current measurement only, with an known power supply116output voltage. Power supply equipment112does not necessarily measure the power usage for each individual powered device. In addition, control system114may execute different procedures than those described above with respect toFIGS. 1 through 3in controlling the power supply to a particular power over Ethernet device122.

Control system114may still receive user specified power limits for each of the plurality of power Ethernet devices122through user interface115or through other suitable system. However, in this example, the power limit associated with any particular power device122is not modifiable in response to a real-time measurement of the amount of power utilized by a particular power over Ethernet device. Rather, in response to a determination that the overall power usage by power over Ethernet devices122exceeds the limit for power supply116, then appropriate steps are taken to lower this power usage. Example steps associated with controlling power to power over Ethernet devices122are described in conjunction withFIGS. 5A and 5B.

FIG. 5Ais a flowchart illustrating example steps associated with managing power supplied to a plurality of power over Ethernet devices. The method150begins at step152. At step154a power limit is allocated for each of a plurality of Ethernet devices. These power limits may differ from the three values currently available under IEEE standard, which are 15.4 watts, 7.5 watts, and 4.0 watts; however, the IEEE values may be used. At step156power is provided to any of the plurality over Ethernet devices122that require power. At step158the collective amount of power utilized by the power over Ethernet devices122is determined. In one example, this determination is made by a power monitor, such as power monitor117.

At step168a determination is made of whether an overall power usage limit is exceeded. If not, processing loops back to step158in which the amount of power being utilized is continually monitored. If the overall usage limit is exceeded, processing continues at step162in which an attempt is made to identify a particular power over Ethernet device that is causing the overall power limit to be exceeded. The approach utilized to determine the particular power over Ethernet device that is causing the problem may vary. One example is described below in conjunction withFIG. 5B.

As an alternative to step162of identifying a particular power over Ethernet device that is causing the overall power usage to be exceeded, power to particular devices may be terminated based upon a device priority. This priority may specify which power over Ethernet devices would receive priority over others in the case where the power supply cannot supply power to all of the devices. This priority may be set through use of an interface such as user interface115, or through other techniques. As another alternative, power may be terminated to power over Ethernet devices without attempting to identify the cause of the over-usage problem until the overall power limit is not exceeded, without attention to any priority allocation.

In the embodiment in which the particular power over Ethernet device causing the power over-usage problem is identified, processing continues at step164in which power is terminated to the identified device. Processing then returns to step158in which the overall power usage is continually monitored.

FIG. 5Bis a flowchart illustrating one example of steps associated with step162ofFIG. 5Aof identifying a problem device. In general, method162involves stepping through each port, terminating power to that port, and observing the effect on the overall power usage. If the overall effect is a significant decrease in the power usage, this may indicate the particular port chosen corresponds to the power over Ethernet device causing the power usage to be exceeded. In such a case, power is terminated to that device.

More specifically, the method begins at step170. Each port is stepped through with the below-described steps until the port corresponding to the power over Ethernet device causing the over-usage problem is identified. At step174it is determined whether the port is allocated a default value, corresponding to one of the IEEE values, or whether the port is allocated a user-specified value. If the port has a default value corresponding to one of the IEEE values then it is not likely the cause of an over-usage problem, which indicated a step176, and processing returns at step174for the next port. However, if the port is not allocated a default value, or all remaining ports are allocated default values, then this indicates the port is potentially associated with the over-usage problem and power is temporarily removed from that port, as indicated at step178. At step180a determination is made whether there is a significant change in the overall power usage. If so, this indicates that the power over Ethernet device associated with that port is likely the problem and power is temporarily terminated to that device, as indicated at step182. However, if at step178no significant change in the overall usage is measured, this indicates that this port is not likely the problem and processing continues at the next port back at step172. It is noted that when referring to a significant change, it is meant to refer to a change in overall power usage greater than the allocated power limit for that particular device. Step184may also involve returning power to the Ethernet device for which power was temporarily terminated; however, in one example, power remains terminated until the port causing the problem is identified. The method concludes at step186.