Abstract:
In a data processing system having elements grouped into a plurality of power domains, each one of which has at least one processing element and at least two power supplies, power domains are interconnnected by sensing and switching circuitry which senses the conditions of power supply and demand in and among the domains and switches from one domain to power supplies in another domain in the event of failure in the first domain.

Description:
FIELD AND BACKGROUND OF INVENTION  
       [0001]     The requirements of data processing systems for electrical power continue to grow, both in new systems being designed and in existing systems in the field. Most of the rising requirement result from increased processor capability and increased power demand by memory. The power requirements will, on occasion, exceed the capability of power supplies associated with processing elements such as systems.  
         [0002]     In server applications, this has been handled by providing redundancies. That is, processing elements such as blades in a blade server will be grouped with power supplies into power domains. Each domain will have one or more processing elements such as blades and at least two power supplies associated with the grouped processing elements. The power supplies work together to supply the voltages and currents required by the processing elements.  
         [0003]     Systems with such N+1 or N+N power supply schemes are known. However, if one power supply shuts down, as by loss or electrical supply or failure, then the system may fail. Some newer processing elements address such problems by providing for throttling down, also sometimes known as power fold back. This is helpful in reducing the power requirement of a domain to that which can be supplied by a single supply, but takes time. There can be sufficient time if line power is lost, as most power supplies typically have a hold up interval. However, if one supply fails, there may be no holdup time available and so over current protection may be tripped in remaining power supplies.  
       SUMMARY OF THE INVENTION  
       [0004]     With the foregoing in mind, it is one purpose of this invention to provide power supply protection for a data processing system having elements grouped into a plurality of power domains, each one of which has at least one processing element and at least two power supplies. In realizing this purpose of the invention, power domains are interconnnected by sensing and switching circuitry which senses the conditions of power supply and demand in and among the domains and switches from one domain to power supplies in another domain in the event of failure in the first domain. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0005]     Some of the purposes of the invention having been stated, others will appear as the description proceeds, when taken in connection with the accompanying drawings, in which:  
         [0006]      FIG. 1  is a schematic representation of connections among a plurality of processing systems, a plurality of power supplies, and circuitry in accordance with this invention which controls sharing of power supply resources among the systems.  
         [0007]      FIG. 2  is a schematic representation of switching circuitry forming a portion of this invention.  
         [0008]      FIGS. 3, 4  and  5  are detailed views of elements of the circuitry of  FIG. 2 . 
     
    
     DETAILED DESCRIPTION OF INVENTION  
       [0009]     While the present invention will be described more fully hereinafter with reference to the accompanying drawings, in which a preferred embodiment of the present invention is shown, it is to be understood at the outset of the description which follows that persons of skill in the appropriate arts may modify the invention here described while still achieving the favorable results of the invention. Accordingly, the description which follows is to be understood as being a broad, teaching disclosure directed to persons of skill in the appropriate arts, and not as limiting upon the present invention.  
         [0010]     Referring now more particularly to the accompanying drawings,  FIG. 1  shows schematically a plurality of digital data processing elements  10 A,  10 B  10 C,  10 D. The elements  10 A through  10 D may be blades within a server blade assembly or other devices which have printed circuit boards carrying an array of semiconductor devices which handle digital data. The elements may be server computer systems or telecommunications control systems or other known digital data processing systems. While only four such elements are illustrated, it will be understood that in a normal installation there can be many more elements, and the illustration of only four has been chosen only for the purpose of simplifying the drawing.  
         [0011]     The apparatus also includes a plurality of power supplies  11 A,  11 B,  11 C,  11 D. The power supplies and processing elements are interconnected into a plurality of power domains, indicated at  12 A,  12 B,  12 C and  12 D. Again, while only a few power supplies and domains are illustrated, that limitation is solely for the purpose of clarity in simplifying the drawing and a implementations usually will include such numbers of processing elements, power supplies and power domains as are determined by system architects and designers.  
         [0012]     In accordance with important features of this invention, the domains  12 A,  12 B,  12 C,  12 D are operatively connected with sensing and switching circuitry  14  which senses the conditions of power supply from the power supplies to the processing elements and responds to a sensed outage of one of the power supplies by switching power supply for a domain in which there is a sensed outage to a domain which has capacity to support the domain with an outage. The switching circuitry is shown in greater detail in  FIGS. 2 through 5 .  
         [0013]     The switching circuitry monitors several characteristics of the power supplied to the domains from the power supplies with which it is associated. Providing power from one domain to another requires careful consideration to ensure that the second domain avoids failure due to excessive demand, which could cause the loss of operability for an entire complex of systems. The domain to become a source must not be overloaded. The load imposed by the domain to be supported must be shared between or among the plurality power supplies in the newly designated source domain. The power made available to the receiving or load domain should be held to a level which just avoids overloading of any remaining active power supply in that domain, for purposes of overall protection of the complex being supported. The power made available to the receiving or load domain can be held at a full requirement until either the failing power supply has been removed or the load is safely throttled back to reduce the power demand in that domain, depending upon the design capability.  
         [0014]     As here illustrated, the switching circuitry  14  monitors the voltage being supplied in the domains (here identified as V rem ); the current being drawn from the domains (here identified as I share ); and a logic level signal which is activated when the loss of line supply is detected (here identified as EPOW for Emergency Power Off Warning). The following describes circuitry using limited power supply signaling. Signals and circuitry could be added to the power supply which could reduce component count of and/or enhance the described circuits. For V rem  and I share , there is one sensed value for each domain; for EPOW, one for each power supply. Conductors through which monitor signals pass are shown in  FIG. 1 , and are omitted for clarity in  FIG. 2 . However, the passage of those signals through the gates of the logic circuitry to be described below are indicated in  FIGS. 3, 4  and  5 .  
         [0015]     The switch logic uses signals from the domains and power supplies to determine which supplies should be interconnected. The switches themselves ( FIG. 2 ) use an array of switch circuits  15 A,  15 B,  15 C,  15 D interposed between the power supplies and the domains supported so as to direct loads to varying combinations of power supplies depending upon sensed needs. Current supplied from each domain is sensed as an analog voltage proportional to the power supply output current and provided through gates for comparison to a reference voltage (V ref ) which is set to a desired threshold indicative that a single power supply is supporting the entire load of a domain.  
         [0016]     The logic controlling the switches is shown more specifically in  FIGS. 3, 4  and  5 . The elements of the switch logic are not there shown directly interconnected. However, the signal lines are identified by letters corresponding to the description here. The switch logic of  FIG. 3  is present in each of the switches  15 A,  15 B,  15 C and  15 D of  FIG. 2 . The voltages of the domains are identified as D 1 A for domain  12 A; D 1 B for domain  12 B; D 2 A for domain  12 C; and D 2 B for domain  12 D. I share   1  and I share   2  are analog signals, used by the power supplies  11 A,  11 B,  11 C, and  11 D to allow current sharing among them. The voltage on the I share  lines is proportional to the power supply output current. I share   1  is shared by domains  12 A and  12 B; I share   2 , by domains  12 C and  12 D. V ref is a reference voltage with which to compare the I share  signals. It should be set to a desired threshold which indicates that a single power supply is unable to support the entire load of a domain. EPOW  1  through EPOW  4  are derived respectively from power supplies  11 A through  11 D and are activated when loss of input line power is sensed. Power supplies are generally required to hold output up for some milliseconds after loss of mains power and assertion of EPOW. Signals indicated simply at  1 , 2 ,  3  and  4  are logic signals indicating which switches  15 A,  15 B,  15 C,  15 D are to be turned on. SW 1  through SW 4  are the signals which turn the switches on.  
         [0017]     D 1 A, D 1 B, D 2 A and D 2 B are compared to determine when and which switches need to be turned on for power sharing. I share   1  and I share   2  are compared against V ref . If an I share  signal is greater than V ref , then a one shot circuit is triggered. The duration of the one shot pulse is determined by the time needed to throttle down the load imposed by the systems to which power is falling. The EPOW signals are or-ed together and prevent the one shot from triggering, because there is a power supply output hold up time associated with EPOW.  
         [0018]     During the time that the one shot is triggered, the transistors Q 1  and Q 2  ( FIGS. 4 and 5 ) will be turned on to raise the voltage in what will be the source domain by the ratio of R 1  to R 2 .  
         [0019]     The switches may be JFETs, two MOSFETS in series such that their body diodes oppose, or any other circuit which, when turned on, will allow current to flow in either direction.  
         [0020]     In the drawings and specifications there has been set forth a preferred embodiment of the invention and, although specific terms are used, the description thus given uses terminology in a generic and descriptive sense only and not for purposes of limitation.