Abstract:
A power entry module (PEM) that is used with an electronics equipment enclosure. The PEM has a housing adapted to be coupled to a shelf of the electronics equipment enclosure. The housing has at least one pair of power cable lugs accessible from an exterior of the housing for coupling the PEM to a pair of power cables associated with a power feed. The PEM also has a backplane connector for coupling the PEM to a blackplane of the electronics enclosure. A distribution network is disposed within the PEM housing and forms at least a pair of electrically isolated power distribution buses for coupling electrical power provided from the power cables to each of the power distribution branches. Each power distribution branch independently provides electrical power to at least one blade supported within the electronics equipment enclosure.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority from U.S. provisional patent application Ser. No. 61/106,290, filed Oct. 17, 2008, the entire contents of which is hereby incorporated by reference into the present application. 
    
    
     FIELD 
     The present disclosure relates to systems and methods for supplying power to electronics enclosures, and more particularly to power entry modules (PEMs) used with systems requiring electrical power to be distributed to a plurality of electronics modules within an enclosure. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     One-to-one redundant power systems are often employed in present day Advanced TCA (Telecommunications Computing Architecture) (hereinafter “ATCA”) electronics equipment enclosures. Typically such enclosures make use of a plurality of shelves that each may support a plurality of “blades” (electronic printed circuit board modules) in side-by-side fashion. ATCA compliant enclosures typically have two power sources, and therefore use separate power entry modules (“PEMs”) in the electronics enclosure for each power source. One PEM is used for each power feed. Each power feed is formed by two cables: a power feed cable and a power return cable. The power feed and power return cables of a single power feed are coupled to a power branch within the enclosure. Each power branch within the enclosure is typically formed by a pair of power buses composed of a feed bus and a return bus that provide power to a subset of the blades in a particular shelf of the enclosure. Within the enclosure, after the PEMs, each power branch stays completely isolated from all the other power branches. The power branches of one PEM are thus all fully isolated from all of the other branches of other PEMs. Typically a redundant PEM or PEMs are employed with the enclosure and are coupled to separate power feed(s) from the other power source to form a backup power feed for a given branch within the enclosure. 
     With present day ATCA compliant enclosures, a PEM is used to interface each cabled power feed with a single power branch. Each power branch distributes power to one or more blades associated with the branch. “B” power branches distribute the power to the “M” blades per power branch. Within the PEM, the power feeds are connected to the power branches such that each power branch is driven from one and only one power feed. An example of such a typical present day configuration is shown in  FIG. 1 . 
     Although not shown in  FIG. 1 , typical ATCA compliant enclosures have shelves that include redundant PEM or PEMs and another set of power branch buses that drive each of the same blades in parallel to the power system diagrammed above. The power source is typically a −48 VDC battery bank, but the present disclosure is not limited to such cases. 
     With present day systems as shown in  FIG. 1 , an enclosure with four power branches per power source can have, for example, PEMs with: 1 power feed at 100 amps, 2 power feeds at 80 amps each, or 4 power feeds at 75 amps each. Because the power branches radiating outward from the power source cannot re-converge, there can be at most one power feed per branch. Thus, the single-feed PEM fans out its one power feed to the enclosure&#39;s four branches. Alternatively, the dual-feed PEM may fan out each of its two power feeds to two of the branches, and the quad-feed PEM directly connects each feed to only one power branch. Note that each PEM variant is required to drive all the power branches in the enclosure, or else some blades would receive no power. Presently, power feeds are limited to about 100 amps per cable set because of restrictions on the diameters of the cables that may be wired to a shelf of an ATCA compliant enclosure. The above limitations thus often find the system designer using a PEM or PEMs with a greater number of power feeds than what is needed for the power requirements of a given card configuration in an enclosure. This serves to increase the overall cost of the system. However, installing a PEM with only a single power feed connection to all the cards in the shelf may result in significant and costly work to reconfigure the enclosure in the event that the configuration of blades within the enclosure is changed at a later date. 
     SUMMARY 
     In one aspect the present disclosure is directed to a power entry module (PEM). The PEM may include a housing adapted to be coupled to a backplane of an electronics equipment enclosure. At least one pair of power cable lugs may be provided that is accessible from an exterior of the housing for coupling the PEM to a pair of power cables associated with a power feed. A backplane connector may be used for electrically coupling the PEM to a blackplane of the electronics equipment enclosure. A distribution network may be disposed within the PEM housing and may form at least a pair of electrically isolated power distribution branches. The electrically isolated power distribution branches may couple electrical power provided from the power cables to each of the electrically isolated power distribution branches and provide a return path for current flowing through each electrically isolated power distribution branch. Each of the electrically isolated power distribution branches may independently provide electrical power to at least one blade associated therewith. 
     In another aspect the present disclosure is directed to a power entry module (PEM) that may include a housing adapted to be coupled to a component of an electronics equipment enclosure. First and second pairs of power cable lugs, accessible from an exterior of the housing, may be used for coupling the PEM to two pairs of power cables associated with first and second power feeds. A backplane connector may couple the PEM to a blackplane of the electronics equipment enclosure. A distribution network disposed within the PEM housing may form at least first, second and third independent, electrically isolated power distribution branches. The distribution network may be adapted to feed electrical power from the first power feed to the first electrically isolated power distribution branch. The distribution network may be adapted to feed electrical power from the second power feed to the second and third electrically isolated power distribution branches, independently of the first electrically isolated power distribution branch. 
     In still another aspect the present disclosure is directed to a method for forming a power entry module (PEM) for use in an electronics equipment enclosure to interface at least one power feed to a plurality of blades housed in the electronics equipment enclosure. The method may include providing a PEM housing adapted to be coupled to a component of the electronics equipment enclosure. At least one pair of power cable lugs, accessible from an exterior of the housing, may be used for coupling the PEM to a pair of power cables associated with the at least one power feed. An electrical connector may be used to couple the PEM housing to the component of the electronics equipment enclosure. A power distribution network within the PEM housing may have at least a pair of electrically isolated power distribution branches for coupling electrical power supplied to the power cable lugs to each of the electrically isolated power distribution branches. Each electrically isolated power distribution branch may be configured to independently provide electrical power to at least first and second ones of the plurality of blades housed within the electronics equipment enclosure. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  is a view of a prior art, multi-feed, multi-branch power architecture arrangement where independent power feeds are interfaced to independent power branches by a conventional power entry module (PEM), and where each power feed can handle only a single power branch; 
         FIG. 2  is a schematic view of one embodiment of a PEM in accordance with the present disclosure in which a power distribution network is formed entirely within the PEM housing, and wherein a single power feed may be used to feed electrical power to more than one power branch; 
         FIG. 3  is a schematic view of another embodiment of the PEM of the present disclosure in which the PEM interfaces a pair of independent power feeds to a plurality of independent power branches, with each power feed supplying electrical power to a plurality of power branches, and with all of the power distribution being accomplished within the PEM housing; and 
         FIG. 4  is a schematic view of another embodiment of the PEM of the present disclosure in which each separate power feed feeds electrical power to a single associated power branch. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
     Referring to  FIG. 2 , there is shown a power entry module (PEM)  10  in accordance with one embodiment of the present disclosure. The PEM  10  has a housing  10   a  having standardized dimensions that enable it to be connected to a backplane  12  within an electronics equipment enclosure  14 . The housing  10   a  includes input power lugs  16   a  and  16   b  that interface the PEM  10  to an external power source  18 . For example, power lug  16   a  may be coupled to a power supply cable  20   a  while power lug  16   b  is independently coupled to a power return cable  20   b . The power cables  20   a / 20   b  may supply a desired current feed, for example 100 amp, to the PEM  10 . A circuit breaker and filter subsystem  22  is also included with the PEM. The circuit breaker and filter subsystem  22  may have a reset button  22   a  projecting through the housing  10   a  that enables a user to manually reset the circuit breaker portion of the circuit breaker and filter subsystem  22  in the event the circuit breaker has been tripped. 
     The PEM  10  includes a power distribution network  24  contained entirely within its housing  10   a . In this example the distribution network  24  fans out the current supplied from the current feed to two electrically isolated power branches  26  and  28 . Each branch  26  and  28  includes at least one, but typically more than one, blade  30  that is powered by the current received through its associated branch. The blades  30  in each branch  26  and  28  are typically located in the same shelf of the enclosure  14 . 
     It is a principal advantage of the PEM  10  that the entire distribution network  24  is housed within the housing  10   a  of the PEM  10 . Thus, simply plugging the PEM  10  into the backplane  12  of the enclosure  14  serves to make the needed connections with both of the power branches  26  and  28 . While  FIG. 2  illustrates only two power branches, it will be appreciated that the PEM  10  could be formed with an internal distribution network that is able to supply power to more than two independent power branch circuits. Thus, the PEM  10  is constructed in accordance with power branch requirements of the enclosure with which it is being used. By locating the entire power distribution network with the PEM  10 , this enables a different PEM having a slightly different power distribution configuration to be implemented without the need for changing out the backplane of the enclosure to implement a different power distribution configuration. 
     Referring to  FIG. 3 , a PEM  100  in accordance with another embodiment of the present disclosure is illustrated. The PEM  100  is similar to the PEM  10  except that the PEM  100  is capable of receiving power from at least two independent cable power feeds  102  and  104  and distributing the power to a plurality of power branches  106 ,  108 ,  110  and  112 . This is accomplished by an internal power distribution network  114  housed entirely within a housing  100   a  of the PEM  100 . Cable power feed  102  is coupled to power lugs  116   a  and  116   b  while cable power feed  104  is coupled to power lugs  118   a  and  118   b . Power lugs  116   a  and  118   a  feed current into the distribution network  114  while power lugs  116   b  and  118   b  form part of a return feed for each cable power feed  116  and  118 . Two independent circuit breaker and filter subsystems  120  and  122  are also preferably included in the PEM  100 , one for each of the power cable feeds  102  and  104 . A backplane  124  of the enclosure  14  receives the PEM  100 . 
     In the example of  FIG. 3 , the PEM  10  power distribution network is configured so that the cable power feed  102  supplies power to the two shown electrically isolated power branches  106  and  108 , while cable power feed  104  supplies power to two electrically isolated power branches  110  and  112 . Again, since all of the power distribution connections are formed within the PEM housing  100   a , no jumpers or straps are required to make the needed connections with the power branches  106 ,  108 ,  110  and  112 . Since the mapping of the power feeds  102  and  104  into the power branches  106 - 112  is done entirely within the PEM  100 , the PEM  100  can use virtually any specific power distribution mapping without physical changes being required anywhere else in the system. This characteristic of the PEM  10  or  100  allows a wide range of applications (i.e., low to high power blades) to be addressed at a minimum cost for each application. 
     It will be appreciated that PEM  100  could easily be modified so that cable power feed  102  feeds only a single power branch, while power feed  104  feeds two or more isolated power branches. Alternatively, three or more cable power feeds could be coupled to the PEM  100  provided the PEM  100  is modified to include a suitable additional number of power lugs to enable attachment of all the cable power feeds. The internal power distribution network of the PEM  100  would also be modified to accommodate the additional power branches that would be fed by each cable power feed. 
     Referring to  FIG. 4 , a PEM  200  in accordance with another embodiment of the present disclosure is shown. The PEM  200  allows four independent cable power feeds  202 ,  204 ,  206  and  208  to be interfaced to an internal distribution network  210  within a housing  200   a  of the PEM  200 . The PEM  200  includes four pairs of power lugs  212 ,  214 ,  216  and  218  that couple power to four independent power branches  220 ,  222 ,  224  and  226 , respectively. Thus, in this example each power feed supplies power to only one power branch. Each of the power lugs  212 ,  214 ,  216  and  218  has a power supply lug  212   a ,  214   a ,  216   a  and  218   a  that each supplies power to its respective power branch. Power lugs  212   b ,  214   b ,  216   b  and  218   b  form parts of power return paths for each power feed. Although not shown to avoid cluttering the figure, the PEM  200  preferably includes four independent circuit breaker and filter subsystems (such as described for PEMs  10  and  100 ), in other words one for each cable power feed  202 ,  204 ,  206  and  208 . Each power branch  220 ,  222 ,  224  and  226  feeds current to one or more blades  230 . The PEM  200  is coupled to a backplane connector  232  of the enclosure  14 . If desired, a greater or lesser number of power feed lugs, with a corresponding number power branches, could be implemented to meet the needs of a specific application. 
     The PEMs  10 ,  100  and  200  enable significantly improved flexibility to be achieved in configuring an enclosure for specific needed power requirements. For example, an enclosure with four power branches per power source can have PEMs with: 1 power feed at 100 amps, 2 power feeds at 80 amps each, or 4 power feeds at 75 amps each. Because the power branches radiating outward form the power source cannot re-converge, there can be at most one feed per branch. So, the single-feed PEM (such as PEM  10 ) fans out its one power feed to the enclosure&#39;s four branches, the dual-feed PEM (such as PEM  100 ) fans out each of its feeds to two of the branches, and the quad-feed PEM  200  directly connects each feed to a single power branch. Note that each PEM variant ( 10 ,  100  and  200 ) is required to drive all the power branches in the enclosure or else some blades would receive no power. 
     Present day restrictions in the size of power cables that can be routed to the enclosure  14  limit the current carrying capacity of a single power feed cable to about 100 amps. Thus, the single cable power feed PEM supports the lowest power per blade, and would be the lowest cost PEM. The two-feed PEM will support upwards of twice the power per blade at a slightly increased PEM cost, and the four-feed PEM, at the highest cost, will support the highest number of power blades with four cable power feeds delivering power to the enclosure  14 . The system designer picks the specific PEM configuration that is appropriate for the power level of the blades that will be installed in a specific enclosure. 
     Previously designed multiple-feed shelf power systems have used a scheme that is generally inflexible and adds cost to systems that do not need higher power currents. For example, some previous shelves have used a physically separate PEM for each power feed into a given shelf. This forces the shelf to have a PEM for each group of blades (i.e., one PEM for each power branch) regardless of whether higher power currents are needed or not. Systems that can operate from the power of a single set of cables (i.e., 100 or less amps) are required in this scheme to have multiple PEMs even though they aren&#39;t needed to receive multiple sets of power feed cables. This approach increases product cost unnecessarily. 
     Each PEM also requires components regardless of its power architecture, such as an IPMC, mechanical components for enclosing and shielding the PEM, and inserting and ejecting the PEM onto and from the backplane, etc. Thus, system level costs are reduced by minimizing the number of PEMs to only that specific minimum number that needs to be used to adequately power all the blades being used in the enclosure. 
     The PEMs  10 ,  100  and  200  are advantageous because they enable the most cost effective configuration of PEM to be implemented for a given cardage configuration. Thus, a specific PEM (e.g., PEM  200 ) may be selected for higher power shelf systems (i.e., 300 W+ per blade) where a multiple cable power feed power is needed, while a PEM having a different internal power distribution network and a single cable power feed (e.g., PEM  10 ) may be used for lower power systems. Thus, the specific configuration of PEM can be selected to avoid the cost penalty that would otherwise be associated with using a PEM having greater power supply and distribution capabilities than needed for a particular application. 
     Another advantage that the PEMs  10 ,  100  and  200  provide is the ease with which the power system configuration can be identified. Whether a shelf is configured for dual-feed power or single-feed power is immediately visible externally by counting the power lugs on the PEM  10 ,  100  or  200  being used. Because the transition from multiple-feed to/from single-feed is accomplished by merely changing the PEMs, the shelf manager can know with 100% confidence how the system is configured by reading the type of PEM installed. There is no other component or factor that determines the power system configuration, and no special cover plates or dummy PEMs that a technician or field engineer would need to consider to understand the specific power configuration of a particular enclosure. Other schemes that involve external straps between PEMs or straps mounted on the backplane cannot be identified so easily. Also, all of the PEMs  10 ,  100  and  200  install the same way on the backplane of the enclosure  14 , the only difference being how many power feed cables are attached to the PEM  10 ,  100  or  200 . 
     From a system configuration point of view, systems using one of the PEMs  10 ,  100  or  200 , or variations thereof, are essentially foolproof in their setup. For each power source, the number of power feeds into the enclosure  14  is determined by the single fact of which type PEM is installed on that side of the enclosure  14 . It does not matter electrically if the PEM for one power source is dual-feed, and the PEM for the other power source is single-feed. Since both types of PEMs are the same size, there is never a need for a special cover plate or dummy PEM. There is only one place each PEM can be inserted into the shelf (i.e., enclosure) to be coupled with the backplane, so there is no difficult in-between positioning to be done when installing the PEMs  10 ,  100  or  200 . Also, with the PEMs  10 ,  100  or  200  inserted into the system, the number of power feeds is immediately visible by one simply counting the power lugs on the PEM faces. There is no strapping installed within the enclosure  14  that would not be visible from outside the enclosure. So configuring enclosures using the PEMs  10 ,  100 ,  200 , or variations thereof, is quick and easy to accomplish. 
     While the various embodiments described herein are especially well suited for use with AdvancedTCA shelves, the PEMs  10 ,  100  and  200  can potentially be implemented with virtually any standard or non-standard electronics enclosure that requires a distributed DC power architecture. Therefore, it will be appreciated that the various embodiments described herein will not be limited in application to only AdvancedTCA systems. 
     While various embodiments have been described, those skilled in the art will recognize modifications or variations which might be made without departing from the present disclosure. The examples illustrate the various embodiments and are not intended to limit the present disclosure. Therefore, the description and claims should be interpreted liberally with only such limitation as is necessary in view of the pertinent prior art.