Abstract:
A redundant power supply may obtain a rule for increasing mean time between failures (MTBF) for a first internal power supply and a second internal power supply connected to an electronic device, apply the rule to the first and second power supplies, activate the second internal power supply based on the rule to permit the second internal power supply to provide power to the electronic device, and deactivate the first internal power supply based on the rule.

Description:
RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 11/849,400, filed Sep. 4, 2007, which is incorporated herein by reference. 
    
    
     BACKGROUND 
     A redundant power supply (RPS) may supply power to a device as means for increasing overall up-time for a device, using multiple power supplies to increase reliability or supplying power when the primary power supply for the device fails or otherwise can no longer deliver sufficient power to the device. The ability of the RPS to protect the device against power failures over time may depend on the reliability of power supplies that are internal to the RPS. 
     SUMMARY 
     According to one aspect, a method may include obtaining a rule for increasing mean time between failures (MTBF) for a first internal power supply and a second internal power supply connected to an electronic device, applying the rule to the first and second power supplies, activating the second internal power supply based on the rule to permit the second internal power supply to provide power to the electronic device, and deactivating the first internal power supply based on the rule. 
     According to another aspect, a redundant power supply may include first and second parallel power supplies for providing power to an electronic device and a controller. The controller may be configured to identify, based on a rule, that the first parallel power supply is to be placed in a stand-by mode. In addition, the controller may be further configured to activate the second parallel power supply to provide the electronic device with power, and place the first parallel power supply in the stand-by mode. 
     According to yet another aspect, a redundant power supply may include means for receiving operational parameters of a first and second internal parallel power supplies, means for applying a rule for increasing mean time between failures (MTBF) to the first and the second internal power supplies, means for placing the second internal power supply in an active roster if the rule applies to the operational parameters of the first internal power supply, means for activating the second internal power supply, and means for deactivating the first internal power supply. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a portion of a redundant power supply (RPS) system for increasing mean time between failures; 
         FIG. 2  is a block diagram of an exemplary system in which concepts described herein may be implemented; 
         FIG. 3  is a block diagram of a parallel power supply of  FIG. 2 ; and 
         FIG. 4  is a flow diagram of an exemplary process for increasing mean time between failures of a parallel power supply of  FIG. 2 ; and 
         FIG. 5  shows an embodiment of the RPS system of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The following detailed description refers to the accompanying drawings. The same reference numbers in different drawings may identify the same or similar elements. 
     The term “healthy” power supply, as used herein, may refer to a power supply that is capable of delivering a specified amount of power. Conversely, as used herein, the term “unhealthy” power supply may refer to a power supply that is incapable of supplying the specified power. 
     The term “active roster,” as used herein, may refer to a list of power supplies that are either currently supplying power or are to be supplying power to power consuming devices. 
       FIG. 1  is an overview of an RPS system  100  that increases mean time between failures (MTBF) of its internal power supplies. As shown, RPS system  100  may include parallel power supplies  102 ,  104  . . . ,  106 , and a controller  108 . Parallel power supplies  102 - 106  may provide power to a power consumer (not shown). Controller  108  may continuously rotate one or more parallel power supplies  102 - 106  to supply power and replace the rotated-out power supplies with one or more other ones of parallel power supplies  102 - 106 . By rotating parallel power supplies  102 - 106 , controller  108  may prevent parallel power supplies  102 - 106  from being under stressful conditions that shorten their lifespan, and consequently, may increase the MTBF of parallel power supplies  102 - 106  within RPS system  100 . 
       FIG. 2  shows an exemplary RPS system  100  in which concepts described herein may be implemented. As shown, RPS system  100  may include power consumer  202  and RPS module  204 . In some implementations, power consumer  202  and RPS module  204  may be part of a single device (e.g., a computer). In other implementations, power consumer  202  may be external to RPS module  204 . In still other implementations, RPS system  100  may include additional power consumers, each of which may require the same or different input power. 
     Power consumer  202  may include a device and/or a component that consumes power (e.g., a motherboard of a computer, a speaker, a computer, etc.). In some implementations, power consumer  202  may include one or more devices that provide at least some of its own internal power or are attached to external power supplies. In such implementations, power consumer  202  may rely on RPS module  204  for supplemental power and/or protection against internal/external power supply failures. In other implementations, power consumer  202  may receive all of its power from RPS module  204 . 
     RPS module  204  may include a device for providing direct current (DC) power. If attached to power consumer  202 , RPS module  204  may have the ability to sustain power consumer  202  when power supplies that are internal to or externally connected to power consumer  202  fail. If power consumer  202  does not include internal power supplies, RPS module  204  may meet all of power needs of power consumer  202 . 
     As further illustrated in  FIG. 2 , RPS module  204  may include parallel power supplies  206 - 210 , a controller  212 , a power switch  214 , communication lines  216 , a controller line  218 , power buses  220 , and power switch line  222 . In other implementations, RPS module  204  may include fewer, additional or different elements or connections than those illustrated in  FIG. 2 . 
     Parallel power supplies  206 - 210  may include devices for producing power that can be delivered to power consumer  202 . In some implementations, parallel power supplies  206 - 210  may be capable of generating power in excess of the amount consumed by power consumer  202 . In such cases, only some of parallel power supplies  206 - 210  may be actively engaged in supplying power to power consumer  202 , and others may be in a stand-by mode. Any of the parallel power supplies in the stand-by mode may replace a parallel power supply that fails and therefore, may provide redundancy protection. 
     Controller  212  may include a device for monitoring and providing command signals to parallel power supplies  206 - 210  and power switch  214 . Controller  212  may monitor parallel power supplies  206 - 210  based on sensor signals that are related to operating parameters of parallel power supplies  206 - 210 , such as temperature, power levels, fan speed, etc. Furthermore, controller  212  may use the signals to determine which of parallel power supplies  206 - 210  may be rotated-out of an active roster and replaced with parallel power supplies that are in the stand-by mode. In some instances, controller  212  may rotate parallel power supplies  206 - 210  partly based on criteria/rules that are inputted by a user, such as a deficit round-robin rule. 
     While  FIG. 2  shows controller  212  as being part of RPS module  204 , in other implementations, controller  212  may be part of power consumer  202  (e.g., a processor in a computer). Furthermore, controller  212  may be implemented as hardware, software, and/or a combination of both. In some implementations, controller  212  may be implemented as part of an application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA). 
     Power switch  214  may connect or disconnect parallel power supplies  206 - 210  from power consumer  202 . If controller  212  determines that power consumer  202  is shorted, controller  212  may cause power switch  214  to disconnect power consumer  202  from parallel power supply  204 . 
     Communication lines  216  may include components for relaying signals that describe operating conditions of parallel power supplies  206 - 210  to controller  212  and for delivering commands from controller  212  to parallel power supplies  206 - 210 . The commands may indicate which of parallel power supplies  206 - 210  may actively supply power and/or which ones may be in the stand-by mode. If a parallel power supply fails, controller  212  may prevent, via communication lines  216 , the failed parallel power supply from being active in RPS system  200 . 
     Controller line  218  may provide a channel via which one or more external devices may communicate and/or interact with controller  212 . For example, controller line  218  may provide a path to a network, to which a management station may be attached (not shown). In such implementations, the management station may receive information about internal operating conditions of RPS module  204  from controller  212 , and provide commands to controller  212  via controller line  218 . 
     Power buses  220  may include a conduction path for delivering power to power consumer  202  and may provide a common voltage rail that is shared among parallel power supplies  206 - 210 . In addition, power buses  220  may include circuitry and/or electronic devices (e.g., a field effect transistor (FET), a diode, etc.) that prevent currents from flowing into a failed parallel power supply. Consequently, if one of parallel power supplies  206 - 210  fails, the failed power supply may not draw current via power buses  220 . 
     Power switch line  222  may carry commands from controller  212  to turn off/on power switch  220  to electrically couple/decouple parallel power supplies  206 - 210  from power consumer  202 . 
       FIG. 3  is a block diagram of parallel power supply  206 . As shown, parallel power supply  206  may include a DC power supply  302 , an alternating current (AC) switch  304 , a temperature sensor  306 , a fan speed sensor  308 , an AC power line  310 , a power sensing line  312 , a temperature line  314 , a fan speed line  316 , and an AC switch line  318 . Depending on implementation, parallel power supply  206  may include fewer, additional, or different components than those depicted in  FIG. 3 . 
     DC power supply  302  may include a device for converting AC to DC and for providing the DC to power consumer  202  through power buses  220 . AC switch  304  may control whether AC is sourced to DC power supply  302 , depending on a signal that is received from controller  212  via AC switch line  318 . If controller  212  determines that parallel power supply  206  is to be placed in a stand-by mode, controller  212  may cause AC switch  304  to prevent the AC from reaching DC power supply  302 . 
     Temperature sensor  306  may provide controller  212  with temperature of DC power supply  302 . Fan speed sensor  308  may provide controller  212  with the speed of a fan (not shown) that may be included in parallel power supply  206 . 
     AC power line  310  may provide a conductive path for AC to be delivered from AC switch  304  to DC power supply  302 . Power sensing line  312  may send information related to power levels at DC power supply  302  to controller  212 . Based on the information from power sensing line  312 , controller  212  may determine whether DC power supply  302  has failed. Temperature line  314  and fan speed line  316  may communicate temperature and fan speed, respectively, to controller  212 . AC switch line  318  may carry commands from controller  212  to power switch  214  and AC switch  304 . 
     Exemplary Processes for Increasing Mean Time Between Failures for Power Supplies 
     The above paragraphs describe system elements that are related to devices and/or components for increasing MTBF of parallel power supplies  206 - 210  in RPS module  204 .  FIG. 4  is a flowchart of an exemplary process  400  that is capable of being performed by one or more of these devices and/or components. 
     Process  400  may start at block  402 , where criteria/rules for rotating parallel power supplies  206 - 210  may be received (e.g., a rule to place a parallel power supply in the stand-by mode if fan speed reaches a threshold and if other active parallel power supplies can deliver sufficient power to a power consumer). In one implementation, the criteria/rules for rotating parallel power supplies may be inputted by a user at a management station or a computer and sent to controller  212  via a network. In different implementations, the criteria/rules may be programmed or hardwired in controller  212 . 
     Sensor information may be received/determined (block  404 ). For example, temperature of DC power supply  302  and/or fan speed may be received at controller  212  from temperature sensor  306  and/or fan speed sensor  308 . In another example, power levels at DC power supply  302  may be determined based on signals that are carried by power sensing line  312 . 
     Power needs of a power consumer may be determined (block  406 ). In one implementation, the power needs may be determined based on the amount of power that is delivered to the power consumer from RPS module  204 . In another implementation, the power needs may be based on information that is inputted by a user. 
     A number of parallel power supplies that are needed to supply power to the power consumer may be determined (block  408 ). The number may be determined based on the power needs of the power consumer, the amount of power each parallel power supply is capable of delivering, and/or the received criteria/rules. For example, if the power needs of the power consumer is 1000 watts, each parallel power supply is capable of delivering 300 watts, and the received criteria/rules require the parallel power supplies to be capable of delivering at least 150% of power that is being consumed at the power consumer, the total number of parallel power supplies that are needed may be computed as 1000 watts×150%/300 watts per parallel power supply=5 parallel power supplies. 
     The number of parallel power supplies that may be placed in the stand-by mode may be determined (block  410 ). The number may be determined by subtracting the number of parallel power supplies that are needed to supply the power to the power consumer from the total number of parallel power supplies that are healthy. For example, assume that the total number of healthy parallel power supplies is 10, and the number of parallel power supplies that are needed to provide power to the power consumer is 5. The number of parallel power supplies that may be placed in the stand-by mode is 10−5=5. 
     A set of parallel power supplies that are to be placed in the stand-by mode may be identified by applying the received criteria/rules (block  412 ). For example, if RPS module  204  includes 10 healthy parallel power supplies, controller  212  may proceed to apply the criteria/rules to the healthy parallel power supplies and rank the healthy parallel power supplies by the extent that the healthy parallel power supplies match the criteria/rules. For example, if the criteria/rules for selecting parallel power supplies are high temperature, controller  212  may rank the parallel power supplies by their temperature. In some situations, due to constraints on power, no parallel power supplies may be placed in the stand-by mode. 
     The criteria/rules may specify different types of factors and/or information for identifying a set of parallel power supplies that may be placed in the stand-by mode. For example, in one implementation, the criteria/rules may specify an average fan speed of each parallel power supplies over a particular amount of time. In another implementation, the criteria/rules may specify a function of temperature, fan speed, and/or other types of sensor information. 
     In some implementations, the criteria/rules may simply rank the parallel power supplies based on a simple strategy, such as a round-robin scheme. In the round-robin scheme, each set of parallel power supplies that have been placed in the stand-by mode may be given a time tag, and the set of parallel power supplies that have the oldest tag may be selected for the stand-by mode. 
     In other implementations, the criteria/rules may include a deficit round-robin scheme. In the deficit round-robin scheme, the set of parallel power supplies with the oldest time tag may be provided with a score that is decremented each time the deficit round-robin is applied. If the resulting score becomes less than a particular threshold (e.g., “0”), the set of parallel power supplies with the oldest time tag may be selected to be placed in the stand-by mode. To continue the deficit round-robin, the next set of parallel power supplies with the oldest time tag may be provided with a score. 
     In still other implementations, the set of parallel power supplies that are to be placed in the stand-by mode may be selected based on a combination of different types of sensor information and/or strategies. 
     An active roster may be determined (block  414 ). The active roster may include a set of parallel power supplies that are not in the set of healthy parallel power supplies that are to be placed in the stand-by mode. 
     The parallel power supplies that are in the active roster may be activated (block  416 ). To activate a parallel power supply in the active roster, controller  212  may enable AC power line  310  in the parallel power supply by turning on AC switch  304 . If a power consumer that is electrically coupled to power bus  220  is not shorted and power switch  214  is off, controller  212  may turn on power switch  214  so that the power consumer can receive power from the activated parallel power supply. 
     The parallel power supplies that are determined to be placed in the stand-by mode may be placed in the stand-by mode (block  418 ). To place a parallel power supply in the stand-by mode, controller  212  may disable AC power line  310  connected to that power supply by turning off AC switch  304 . 
     From block  418 , process  400  may return to block  404  to repeat blocks  404 - 418 . As process  400  repeats blocks  404 - 418 , operating conditions of RPS module  204  may change (e.g., plugging in a new device to RPS module  204 , changing temperatures of parallel power supplies  206 - 210 , a failure of a parallel power supply, etc.) or power requirements of RPS module  204  may change (e.g., the power required by the power consumer may change). Consequently, the number of parallel power supplies that are needed to supply the power consumer may change, as well as the set of parallel power supplies that can be placed in the stand-by mode. 
     During the operation of RPS module  204  in accordance with process  400 , placing a number of parallel power supplies in the stand-by mode may alleviate stress that is placed on some of the parallel power supplies, and therefore, may increase the lifetime of the parallel power supplies and their MTBF. The stress may be caused by different factors, such as heat in DC power supply  302  or at a fan within RPS module  204 , excessive current from DC power supply  302 , etc. In some situations, the stress may be caused by wiring configuration of the parallel power supplies  206 - 210  with respect to power consumers. For example, in some implementations, parallel power supplies  206 - 210  may be sensitive to small differences in resistance at different points at power buses  220 . Because of the sensitivity, the parallel power supplies that are connected by shorter buses to the power consumers may be forced to provide a disproportionately large share of the power that is supplied to the power consumer. 
     In other situations, the stress may be caused by minor differences between parallel power supplies  206 - 210  in RPS module  204 . For example, each of parallel power supplies  206 - 210  may be manufactured with a slightly different internal resistance. In such cases, the differences may cause one or more of parallel power supplies  206 - 210  to produce more power than others. By placing some of the parallel power supplies in the stand-by mode and rotating parallel power supplies that are in the active roster, stress that is placed on the parallel power supplies may be reduced. Consequently, the MTBF of the parallel power supplies, as well as the reliability of RPS module  204 , may be increased. 
     Example 
     The following example illustrates the process for increasing the MTBF of parallel power supplies in a RPS module, with reference to  FIG. 5 . The example is also consistent with the exemplary process described above with reference to  FIG. 4 . 
     In the example, as illustrated in  FIG. 5 , assume that a system  500  includes a power consumer  502  that does not have an internal power supply; that power consumer  502  is connected to parallel power supplies  504  and  506 ; and that RPS module  508  includes parallel power supplies  504  and  506 , a controller  510 , and power switch  512 . Further, assume that a user has inputted a criterion/rule for rotating parallel power supplies  504  and  506  via a management station that is connected to RPS module  508 , that each parallel power supply is capable of delivering 300 watts, and that the criterion/rule is to try to place parallel power supplies that operate above 70 degrees Celsius (° C.) in the stand-by mode. 
     RPS module  508  monitors power consumer  502  and determines that power consumer  502  needs 300 watts. In addition, RPS module  508  receives temperature readings from parallel power supplies  504  and  506  as 68° C. and 72° C., respectively. Based on the temperatures of parallel power supplies  504 - 506  and the projected power consumption of power consumer  502 , controller  510  determines that only one parallel power supply needs to supply power to power consumer  502 , and that parallel power supply  506  can be placed in the stand-by mode. Parallel power supply  504  is placed on the active roster. 
     Controller  510  activates parallel power supply  504  and places parallel power supply  506  in the stand-by mode, by sending commands to AC switches and power switches that are included in parallel power supplies  504 - 506 . 
     Controller  510  continues to perform process  400  to rotate parallel power supplies. For example, when parallel power supply  506  cools down to 69° C. and parallel power supply  504  heats up to 71° C., controller  510  places parallel power supply  504  in the stand-by mode and parallel power supply  506  in the active roster. 
     CONCLUSION 
     The foregoing description of implementations provides illustration, but is not intended to be exhaustive or to limit the implementations to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the teachings. 
     For example, while a series of blocks has been described with regard to processes illustrated in  FIG. 4 , the order of the blocks may be modified in other implementations. In addition, non-dependent blocks may represent acts that can be performed in parallel to other blocks. 
     It will be apparent that aspects described herein may be implemented in many different forms of software, firmware, and hardware in the implementations illustrated in the figures. The actual software code or specialized control hardware used to implement aspects does not limit the invention. Thus, the operation and behavior of the aspects were described without reference to the specific software code—it being understood that software and control hardware can be designed to implement the aspects based on the description herein. 
     Even though particular combinations of features are recited in the claims and/or disclosed in the specification, these combinations are not intended to limit the invention. In fact, many of these features may be combined in ways not specifically recited in the claims and/or disclosed in the specification. 
     No element, act, or instruction used in the present application should be construed as critical or essential to the implementations described herein unless explicitly described as such. Also, as used herein, the article “a” is intended to include one or more items. Where one item is intended, the term “one” or similar language is used. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise.