Abstract:
A system and method for multiple power over Ethernet (PoE) power supply management. Power supply status signals indicative of an operating condition of a plurality of PoE power supplies are provided to a plurality of power sourcing equipment (PSE) controller chips. Pre-configured combination logic within each of the PSE controller chips converts an indicated operational state of the plurality of PoE power supplies into a powering decision for each of the Ethernet ports served by the PSE controller chip within one microsecond.

Description:
BACKGROUND 
     1. Field of the Invention 
     The present invention relates generally to Power over Ethernet (PoE) and, more particularly, to a system and method for multiple PoE power supply management. 
     2. Introduction 
     The IEEE 802.3af and 802.3at PoE specifications provide a framework for delivery of power from power sourcing equipment (PSE) to a powered device (PD) over Ethernet cabling. Various types of PDs exist, including voice over IP (VoIP) phones, wireless LAN access points, network cameras, computing devices, etc. 
     In the PoE process, a valid device detection is first performed. This detection process identifies whether or not it is connected to a valid device to ensure that power is not applied to non-PoE capable devices. After a valid PD is discovered, the PSE can optionally perform a power classification. In 802.3af, the power classification process can be used to classify a PD into various pre-defined power levels (i.e., 4.0 W, 7.0 W, and 15.4 W). 
     In more advanced power classification schemes, a dynamic power management process can be used to generate a power request and priority for a PD based on current or anticipated power needs. As the total PSE power budget is typically limited as compared to the total power demand of the set of PDs, the dynamic power management process would consider the competing power needs of the various PDs. 
     The goal of the PSE management task is to provide stable output power to the various PDs. In a conventional PSE design, multiple power supplies can be used. A benefit of such a multiple power supply design is the elimination of a single point of failure. What is needed, however, is a mechanism for managing the allocation of power to a plurality of PDs based on the relative status of the multiple power supplies. 
     SUMMARY 
     A system and/or method for multiple PoE power supply management, substantially as shown in and/or described in connection with at least one of the figures, as set forth more completely in the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to describe the manner in which the above-recited and other advantages and features of the invention can be obtained, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
         FIG. 1  illustrates an embodiment of a PoE system. 
         FIG. 2  illustrates an embodiment of a microcontroller that receives power supply status signals. 
         FIG. 3  illustrates an embodiment of PSE controllers that receive power supply status signals. 
         FIG. 4  illustrates a flowchart of a management process in a PoE system having multiple power supplies. 
         FIG. 5  illustrates an embodiment of a mechanism that generates power supply status signals. 
         FIG. 6  illustrates another embodiment of PSE controllers that receive power supply status signals. 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments of the invention are discussed in detail below. While specific implementations are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components and configurations may be used without parting from the spirit and scope of the invention. 
       FIG. 1  illustrates an embodiment of a power over Ethernet (PoE) system. As illustrated, the PoE system includes power sourcing equipment (PSE)  120  that transmits power to powered device (PD)  140 . Power delivered by the PSE to the PD is provided through the application of a voltage across the center taps of transformers that are coupled to a transmit (TX) pair and a receive (RX) pair of wires carried within an Ethernet cable. In general, the TX/RX pair can be found in, but not limited to structured cabling. The two TX and RX pairs enable data communication between Ethernet PHYs  110  and  130  in accordance with 10BASE-T, 100BASE-TX, 1000BASE-T, 10GBASE-T and/or any other layer 2 PHY technology. 
     As is further illustrated in  FIG. 1 , PD  140  includes PoE module  142 . PoE module  142  includes the electronics that would enable PD  140  to communicate with PSE  120  in accordance with a PoE standard such as IEEE 802.3af, 802.3at, legacy PoE transmission, or any other type of PoE transmission. PD  140  also includes pulse width modulation (PWM) DC:DC controller  144  that controls power FET  146 , which in turn provides constant power to load  150 . 
     In the example of the IEEE 802.3af standard, PSE  120  can deliver up to 15.4 W of power to a plurality of PDs (only one PD is shown in  FIG. 1  for simplicity). In the IEEE 802.at draft specification, on the other hand, a PSE may be able to deliver up to 30 W of power to a PD over 2-pairs. Other proprietary solutions can potentially deliver even higher levels of power to a PD. In general, high power solutions are often limited by the limitations of the cabling. 
     In one embodiment, multiple power supplies PS 0 , PS 1 , PS 2 , . . . PSN can be used to provide power to the PoE system. In one implementation, this set of power supplies is connected to all of the PSEs. In another implementation, each PSE is connected to an identifiable subset of the power supplies. Consider, for example, a PoE system that supports  48  ports using 12 quad controller PSEs. In this example, PSE 1  can be coupled to power supplies PS 0 , PS 1 , PS 2 , PSE 2  can be coupled to power supplies PS 0 , PS 3 , PS 4 , and PSE 3  can be coupled to power supplies PS 4 , PS 5 , PS 6 . In general, any combination of power supplies to a given PSE can be used. 
     One of the responsibilities of the PSEs is to manage the power that is supplied to the various supported PDs based on the status of the multiple connected power supplies. In the example of  FIG. 1 , PSE  120  is shown as being coupled to three power supplies PS 0 , PS 1 , PS 2 . If PS 0 , PS 1 , and PS 2  are all up, then the maximum amount of power is available to PSE  120 . Assume at that point, that PSE  120  has enough power for four PDs (PD 1 , PD 2 , PD 3 , PD 4 ) at respective power levels PL 1 , PL 2 , PL 3 , PL 4 . If power supply PS 1  fails, an adjustment of the power allocation amongst PD 1 , PD 2 , PD 3 , and PD 4  may be required. This process would consider the power priorities for PD 1 , PD 2 , PD 3 , and PD 4  along with the power priorities for any other PDs that are supported by a PSE coupled to power supply PS 1 . For example, if only a second PSE (supporting PD 5 , PD 6 , PD 7 , and PD 8  at power levels PL 5 , PL 6 , PL 7 , and PL 8 ) is coupled to PS 1 , then the power management process would consider the power priorities of PD 1 -PD 8 . The lowest priority PDs having a total power level equivalent to the reduction in power would then be cut off from receiving any more power. 
       FIG. 2  illustrates an embodiment of a PoE system that enables management of multiple power supplies. As illustrated, the PoE system includes PSE controllers  1 -N. Each PSE controller supports a set of PDs. In this configuration, PSE controllers  1 -N are each coupled to bus  210  (e.g., I2C), which is coupled to microcontroller  220 . Here, microcontroller can operate as a master device, while PSE controllers  1 -N can operate as slave devices. Microcontroller  220  is coupled to a host device through opto  230 , which provides an isolation boundary. 
     As illustrated, microcontroller  220  receives power supply status signals PSS 0 , PSS 1 , PSS 2 , which each provide power supply status information for a given power supply. In this example, it is assumed that only three power supplies PS 0 , PS 1 , PS 2  are used for the PoE system. In various examples, the power supply signals can represent power supply outputs, “power good” signals, or the like. 
     When power supply status signals PSS 0 , PSS 1 , PSS 2  indicate that power supplies PS 0 , PS 1 , PS 2  are up and running, PSE controllers  1 -N can be configured to provide power to a first set of PDs. If power supply PS 1  fails, an indication of such a failure would be reflected by power supply signal PSS 1 . At that point, a reallocation of power amongst the plurality of supported PDs would occur. Implementation of this determined reallocation would then be implemented by microcontroller  220  in the reprogramming of various PSE controllers to account for the new power budget. A disadvantage of such a technique is the significant time required for the reprogramming of the PSE controllers. During such a reconfiguration time, disruption in PoE service can occur. 
       FIG. 3  illustrates an embodiment of the present invention that enables disconnection of ports without reprogramming of the PSE controllers. In this embodiment, each of PSE controllers  1 -N have an integrated microcontroller, thereby obviating the need for an external microcontroller. As such, one of the PSE controllers (e.g., PSE controller  1 ) can operate as a master device, while the remaining PSE controllers ( 2 -N) can operate as slave devices. Communication between PSE controllers  1 -N is facilitated by bus  310 . 
     In the configuration of  FIG. 3 , each of PSE controllers  1 -N is designed to receive power supply status signals PSS 0 , PSS 1 , PSS 2 , which relate to the status of power supplies PS 0 , PS 1 , PS 2 . In operation, power supply status signals PSS 0 , PSS 1 , PSS 2  function as an enable signal for internal pre-configured registers (or software function), which when configured as unmasked will disconnect the specified port(s) for the active combination. In one embodiment applied to quad PSE controllers, each PSS 0 , PSS 1 , PSS 2  combination would be associated with a 4-bit mask, wherein each bit is associated with an individual PD port. Each PSE controller would have its own 4-bit mask that would apply for the four associated ports. 
     In the current example, the power supply status signals have the following combinations where a “0” indicates that a power supply is down and a “1” indicates that a power supply is up. 
     
       
         
               
               
               
             
           
               
                   
               
               
                 PSS0 
                 PSS1 
                 PSS2 
               
               
                   
               
             
             
               
                 0 
                 0 
                 1 
               
               
                 0 
                 1 
                 0 
               
               
                 0 
                 1 
                 1 
               
               
                 1 
                 0 
                 0 
               
               
                 1 
                 0 
                 1 
               
               
                 1 
                 1 
                 0 
               
               
                 1 
                 1 
                 1 
               
               
                   
               
             
          
         
       
     
     Each of these PSS 0 , PSS 1 , PSS 2  combinations trigger pre-configured registers in each PSE controller that take into account port priorities (e.g.,  0 - 3 ). In general, higher priority ports are powered up first to use up an available power budget and lower priority ports are disconnected first to accommodate an oversubscribed power budget. In the configuration process, the bit masks for each PSS 0 , PSS 1 , PSS 2  combination are created by identifying the ports that should be powered for a given power PSE budget as dictated by the available power supplies. 
     In one embodiment, the ports are examined for the highest priority level (e.g., 3) from the lowest to the highest numbered port (e.g., port  0  to port  47 ). This examination would then continue at the next highest priority level (e.g., 2) from the lowest to the highest numbered port. The process would continue until the lowest priority level is reached and all ports are examined. In this process, the sequentially identified ports from highest to lowest priority are identified until the power budget dictated by the combination of available power supplies is reached. At that power supply combination, each identified port that can be powered is associated with a masked bit for the serving PSE controller, while each remaining ports that cannot be powered is associated with an unmasked bit for the serving PSE controller. The end result at that power supply combination is a bit mask for each PSE controller that identifies which ports are powered and which ports are not powered. The configuration process would be repeated for each power supply combination to produce bit masks for each PSE controller at every power supply combination. 
     In the current example, the configuration process is based on priority levels. As would be appreciated, the configuration process can be based on any priority or other derating information that would be applicable to the power management process. 
     The end result of the configuration process is a set of pre-configured bit masks for each PSE controller that would be individually selectable based on the power supply combination indicated by the power supply status signals. In one embodiment, these pre-configured bit masks can be implemented as pre-configured registers (or software function) for use by the PSE controllers. To illustrate the use of such bit masks, a brief description of the transition between example combinations is provided below. 
     Combination ( 111 ) indicates that all three power supplies PS 0 , PS 1 , PS 2  are up and running and PSE controllers  1 -N allocate power according to the bit masks associated with combination ( 111 ). If PS 2  fails, then combination ( 111 ) goes to combination ( 110 ). The global power management modules within the PSE controllers would then access the bit masks associated with combination ( 110 ) and power down the additional ports having an unmasked bit. In one embodiment, the global power management modules are implemented in firmware within the PSE controllers. 
     For example, assume that PSE controller  1  has a 4-bit mask for combination ( 111 ) of  1110  and a 4-bit mask for combination ( 110 ) of  1010 . Here, a “1” is a masked bit, and a “0” is an unmasked bit. The 4-bit mask  1110  for combination ( 111 ) would indicate that when power supplies PS 0 , PS 1 , PS 2  are all up, ports  0 - 2  would be powered and port  3  would not be powered. The 4-bit mask  1010  for combination ( 110 ), on the other hand, would indicate that when power supply PS 2  fails, ports  0  and  2  would be powered and ports  1  and  3  would not be powered. In the transition from combinations ( 111 ) to combination ( 110 ), the global power management module in PSE controller  1  would determine that port  1  in addition to port  3  would not be powered. 
     As noted, combination ( 110 ) indicates that power supplies  0  and  1  are up and running. If power supply  0  fails, then combination ( 110 ) would transition to combination ( 010 ). Assume that PSE controller  1  has a 4-bit mask of  1010  for combination ( 010 ). In this example, the global power management modules within PSE controller  1  would then access the bit mask associated with combination ( 010 ). In this example, the 4-bit mask for combination ( 110 ) is the same as the 4-bit mask for combination ( 010 ). The global power management module in PSE controller  1  would therefore know that no changes to the powering of the ports served by PSE controller  1  would be required. As such, the impact of the transition between combination ( 110 ) to combination ( 010 ) would be felt by ports served by one or more of the remaining PSE controllers. 
     For example, assume that PSE controller  2  has a 4-bit mask of 1xxx for combination ( 110 ) and a 4-bit mask of 0xxx for combination ( 010 ). In the transition from combination ( 110 ) to combination ( 010 ), the impact would be felt by port  0  of PSE controller  2 . Here, port  0  would be powered down based on an identification of an unmasked bit at the first position of the 4-bit mask 0xxx for combination ( 010 ). 
     If at some point, PS 0  comes back on line, then combination ( 010 ) goes back to combination ( 110 ). In the above example, the global power management module within PSE controller  2  would then access the 4-bit mask associated with combination ( 110 ) and power up port  0  based on an identification of a masked bit at the first position of the 4-bit mask 1xxx. 
     As this example illustrates, the changes in combination based on the change in status of the power supplies can lead to rapid connection/disconnection of ports for each of the PSE controllers. This rapid connection/disconnection of ports is facilitated by the receipt of power supply status signals directly by each PSE controller. Upon detection of changes in state of a power supply, the individual PSE controllers can then connect/disconnect ports through the guidance of pre-configured combination logic within the PSE controllers. Response time to changes in power supply state is therefore improved as reprogramming of the PSE controllers would not be required. With the principles of the present invention, response time to changes in power supply status can occur in approximately 1 μs. 
     To further illustrate the power supply management process of the present invention reference is now made to the flowchart of  FIG. 4 . As illustrated, the process begins at step  402  where power supply status signals are received at a PSE controller. As noted above, the power supply status signals are received directly by each PSE controller. This is in contrast to conventional systems that receive the power supply status signals at a single external microcontroller. 
     Based on the receipt of a set of power supply status signals, the PSE controller would then access a bit mask associated with the combination indicated by the power supply status signals. At step  404 , the PSE controller would then configure the ports (i.e., powered or not powered) based on the logic presented by the pre-configured bit mask that is accessed. 
     The process then proceeds to step  406 , where it is determined whether a change has occurred in the combination reflected by the received power supply status signals. If it is determined at step  406 , that a change in combination has occurred, then the pre-configured bit mask associated with the new combination is accessed. At step  408 , the ports are then configured in accordance with the new bit mask. Here, it should be noted that the new bit mask may be identical to the bit mask of the previous combination. In this case, the combination logic would not produce any changes in the powered/non-powered configuration of the ports. If, on the other hand, the new bit mask is different than the bit mask of the previous combination, then the PSE controller would change the powered/non-powered status of at least one of the ports. In general, the process of  FIG. 4  would continue through the detection of various combination changes as indicated by the power supply status signals. Throughout this process, reprogramming of the PSE controllers would not be required. 
     In the example embodiments described above, the power supply status signals are associated with a single power supply. For example PSS 1  can be associated with the status of PS 1 . In one embodiment, the power supply status signals are not associated directly with the status of a particular power supply.  FIG. 5  illustrates an example of such an embodiment that is applied to a system having eight power supplies PS 1 -PS 8 . In the illustrated example, the status of the eight power supplies PS 0 -PS 7  are provided as inputs to logic block  510 . In various embodiments, logic block  510  can be embodied as a complex programmable logic device (CPLD), field programmable gate array (FPGA), or the like. In general, logic block  510  is operable to convert the status indications of power supplies PS 0 -PS 7  into power supply status signals PSS 0 , PSS 1 , PSS 2 . Power supply status signals PSS 0 , PSS 1 , PSS 2  would then be provided as inputs to each of PSE controllers  1 -N. In one example, logic block  510  would be designed to indicate how many of the eight power supplies PS 0 -PS 7  are available through the logic level of the three power supply status signals PSS 0 , PSS 1 , PSS 2 . For example, power supply status signals PSS 0 , PSS 1 , PSS 2  can have values 0, 1, 1, respectively, indicating that three out of eight power supplies are operational. 
     In one embodiment, the various PSE controllers need not receive the same set of power supply status signals.  FIG. 6  illustrates such an example embodiment. As illustrated, PSE controller  1  receives power supply status signals PSS 0 , PSS 1 , PSS 2 , PSE controller  2  receives power supply status signals PSS 0 , PSS 3 , PSS 4 , and PSE controller  3  receives power supply status signals PSS 0 , PSS 5 , PSS 6 . In this configuration, the port configurations for PSE controller  1  would be dependent on power supplies PS 0 , PS 1 , PS 2 , the port configurations for PSE controller  2  would be dependent on power supplies PS 0 , PS 3 , PS 4 , and the port configuration for PSE controllers  2  would be dependent on power supplies PS 0 , PS 5 , PS 6 . In general, each PSE controller can have ports whose powered/non-powered status is dependent on the status of a particular set of power supplies. Example of such customization include the sharing of a particular power supply by ports on different PSE controllers, the exclusive use of a particular power supply by ports on a particular PSE controller, the use of redundant power supplies by ports on one or more PSE controllers, etc. 
     It should be noted that the use of multiple power supply management can achieve the powering down of lower priority ports in less than  1  microsecond, which therefore saves the PoE system from shutting down due to increased port current or dropping voltage levels. 
     These and other aspects of the present invention will become apparent to those skilled in the art by a review of the preceding detailed description. Although a number of salient features of the present invention have been described above, the invention is capable of other embodiments and of being practiced and carried out in various ways that would be apparent to one of ordinary skill in the art after reading the disclosed invention, therefore the above description should not be considered to be exclusive of these other embodiments. Also, it is to be understood that the phraseology and terminology employed herein are for the purposes of description and should not be regarded as limiting.