Abstract:
A power supply system and method are disclosed that may incorporate a plurality of cascading power units arranged in parallel, a connection interface between the plurality of cascading power units and an electronic load, wherein the connection interface prevents current from entering one of the plurality of cascading power units from another of the plurality, and wherein each one of the plurality of cascading power units has a maximum effective output voltage greater than a next one of said plurality.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates in general to electronic systems and, more specifically, to a power supply system.  
       BACKGROUND  
       [0002]     Larger computer systems and component/cabinet-based systems are usually designed with voltage supplies that are capable of handling multiple upgrades to the chipsets, boards, input/output (I/O) subsystems, and the like. The power supplies normally remain in the system infrastructure while the componentry is replaced and/or upgraded. Typically, each subsequent component generation comes with an increased overall power requirement. Therefore, power supplies typically are only lightly-loaded, by design, during the earlier hardware versions to leave enough head-room or power capacity for the future-upgraded system.  
         [0003]     A power supply&#39;s efficiency is closely related to the load on the supply. The highest efficiency typically occurs when the power supply is loaded to approximately 85% of its maximum rated current, while the lowest efficiency is usually experienced at load levels below 60%. Some power supplies found in the early versions of the systems may only reach load-levels of 5-10%. In these low-load situations, power is wasted, and the system is much less efficient at this stage.  
       SUMMARY  
       [0004]     Representative embodiments of the power supply system are directed to a power supply system that may incorporate a plurality of cascading power units arranged in parallel, a connection interface between the plurality of cascading power units and an electronic load, wherein the connection interface prevents current from entering one of the plurality of cascading power units from another of the plurality, and wherein each one of the plurality of cascading power units has a maximum effective output voltage greater than a next one of the plurality.  
         [0005]     Additional representative embodiments of the power supply system are directed to a method for supplying power to an electronic load comprising connecting a plurality of power supplies in parallel, setting a maximum effective voltage for each of the plurality of power supplies to cascade from a highest effective voltage for a first of the plurality to a lowest effective voltage for a last of the plurality, and interfacing the plurality of power supplies with the electronic load through an isolation interface.  
         [0006]     Further representative embodiments of the power supply system are directed to a power module for supplying power to a load, the power module comprising a plurality of power supplies connected in parallel, wherein each one of the plurality is selected to have a maximum output voltage greater than a next one of the plurality, and a connection interface for connecting the power module to an isolation circuit of the load, wherein the isolation circuit prevents current from one of the plurality of power supplies to sink into another of the plurality of power supplies. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]      FIG. 1  is a block diagram illustrating a power supply module configured according to the teachings herein;  
         [0008]      FIG. 2  is a block diagram illustrating another embodiment of a power supply module configured according to the teachings herein;  
         [0009]      FIG. 3  is a block diagram illustrating another embodiment of a power supply module configured according to the teachings herein;  
         [0010]      FIG. 4  is a flow chart illustrating example steps followed in implementing one embodiment of the present cascading power system; and  
         [0011]      FIG. 5  is a flow chart illustrating example steps followed in implementing an additional embodiment of the present cascading power system.  
     
    
     DETAILED DESCRIPTION  
       [0012]      FIG. 1  is a block diagram illustrating power supply module  10  configured according to the teachings herein. Power supply module  10  incorporates individual bulk power supplies  100 - 103  arranged in parallel. Power supply module  10  supplies power to load  11  through power regulator circuit  12 . The positive terminals of bulk power supplies  100 - 103  are connected to diodes  104 - 107 , respectively, generally to prevent current from sinking into a failed one of bulk power supplies  100 - 103 , should a failure occur. For example, if bulk power supply  100  fails, diode  104  turns off as the voltage on the anode of diode  104  falls below the voltage of its cathode, thus, restricting current from bulk power supplies  101 - 103  from sinking into failed bulk power supply  100 . However, if diode  104  is off, then bulk power supply  100  does not supply any power to load  11 , leaving bulk power supplies  101 - 103  to supply the power to load  11 . If the current used by load  11  exceeds the current available from bulk power supplies  101 - 103 , then each of supplies  101 - 103  will begin to droop (i.e., the maximum output voltage begins to drop).  
         [0013]     Power supply module  10  takes advantage of the drooping characteristic by using bulk power supplies  100 - 103  with cascadingly decreasing voltage levels (e.g., 48.5V, 48.4V, 48.3V, 48.2V, and the like). At the earliest stages of load  11 , when the current demand is not very high, bulk power supply  100  may operate while bulk power supplies  101 - 103  are disconnected due to diodes  105 - 107  of power regulator circuit  12  also being off. However, as load  11  is modified or upgraded to increase its power requirement from bulk power supply  100  beyond bulk power supply  100 &#39;s maximum power rating, the output voltage of bulk power supply  100  will begin to droop. Using the exemplary voltage levels referred to above, when bulk power supply  100  droops from 48.5V to 48.4V, diode  105  will turn on, thus, activating bulk power supply  101 . The combined power supply will typically provide 48.4V and equally share the current load between bulk power supplies  100  and  101 . As load  11  continues to increase its power requirement, bulk power supplies  102  and  103  will cascade on as the overall voltage level droops and then stabilizes at the lowest output voltage of bulk power supplies  100 - 103 .  
         [0014]     It should be noted that power supplies may be selected to provide various voltage levels depending on the power requirements of the particular load that the system is being designed for.  
         [0015]      FIG. 2  is a block diagram illustrating another embodiment of power supply module  20  configured according to the teachings herein. Power supply module  20  includes bulk power supplies  200 - 202  each carrying a maximum output voltage of 50 V. Power supply module  20  is, therefore, homogenous. Homogenous power supply module  20  may also be used in a system in a manner as described herein by connecting to load  21  through power selector circuit  22 . Power selector circuit  22  includes voltage selecting resistors R 1 -R 6 . By selecting the values of R 1 -R 6  at the design stage, the effective voltage supplied to load  21  may be selected with bulk power supplies  200 - 202  each having the same raw maximum voltage output. When each of power supplies  200 - 202  are connected to power selector circuit  22 , R 1  generally reduces the effective voltage seen at diode  203 , R 3  generally reduces the effective voltage seen at diode  204 , and R 5  generally reduces the effective voltage seen at diode  205 . With the proper selection of R 1 , R 3 , and R 5 , the effective voltage output for power supplies  200 - 202  may be selected at or tuned to the desired cascading values, such as 48.5V, 48.4V, and 48.3V. By creating the stepped voltage supply from homogenous power supply module  20 , various embodiments of the power supply system described herein may be implemented.  
         [0016]     It should be noted that the voltage-selecting circuit shown in  FIG. 2  is only one example embodiment for creating a stepped effective voltage in power supply module  20 . Other methods for creating a voltage drop between any one of power supplies  200 - 202  and diodes  203 - 205  may be used.  
         [0017]      FIG. 3  is a block diagram illustrating another embodiment of power supply module  30  configured according to the teachings herein. Power supply module  30  includes power supplies  300 - 302 . Power selector circuit  32  includes isolation diodes  303 - 305 , selectors  306  and  308 , resistor packages  307  and  309 , and timer  310 . TIMER  310  has a RESET node connected to the RESET of selector  306  and  308 . Power supply module  30  is connected to load  31  through power selector circuit  32 . The values of R 7 -R 12  are selected to create a initial, stepped power bank of power supplies  300 - 302 . In operation, when power supply  300  is loaded to the point where its effective voltage equals or nearly equals the effective voltage from power supply  301 , power supply  301  will turn on and selector  306  disconnects R 8  from the voltage divider pair R 7 /R 8  and switches/selects R 13  to form a new voltage divider of R 7 /R 13 . The value of R 13  has been selected, such that the voltage divider formed by R 7 /R 13  holds the effective voltage level of power supply  300  to a maximum of that level for power supply  301 . Setting power supply  300  to the maximum effective voltage of power supply  301  prevents power supply  300  from trying to supply its original maximum effective output voltage when power supply  301  relieves some of the loading on power supply  300 .  
         [0018]     As the voltage or current requirements of load  31  continue to rise, combined power supply  300  and  301  may also begin to droop. If the voltage of combined power supply  300  and  301  reaches the maximum effective voltage of power supply  302 , power supply  302  will turn on and selector  306  will disconnect R 13  and select R 14  to create voltage divider R 7 /R 14 , which holds power supply  300  at the maximum effective output voltage of power supply  302 . Similarly, selector  307  disconnects R 10  and switches/selects R 15  to form voltage divider R 9 /R 15 , which also holds power supply  301  at the maximum effective output voltage of power supply  302 . Setting combined power supply  300  and  301  to the maximum effective voltage of power supply  302  prevents combined power supply  300  and  301  from trying to supply the original combined maximum effective output voltage when power supply  302  relieves some of the loading on combined power supply  300  and  301 .  
         [0019]     In systems where the power requirements of load  31  may be reduced. Timer  310  may be used to reset selectors  306  and  308  to switch to/or select the original resistors R 8  and R 10  to form original voltage dividers R 7 /R 8  and R 9 /R 10 . Timer  310  may include a periodic signal that allows the latched power supplies to attempt to return to supplying its maximum effective output voltage. In the previous example, if timer  310  signals RESET on selector  306 , power supply  300  will attempt to supply its original maximum effective output voltage. The difference in voltages between power supply  300  and power supply  301  will cause diode  304  to deactivate power supply  301  leaving power supply  300  to supply all of the power to load  31 . If the power requirements of load  31  have not changed, power supply  300  will again droop to the effective output voltage level of power supply  301  and be limited again by selector  306 . However, if the power requirements of load  31  have been reduced, when power supply  301  is unlatched, diode  304  will again deactivate power supply  301  and power supply  300  will supply the power to load  31 . If the power requirement of load  31  has been reduced enough, power supply  300  will not droop to the level that would turn power supply  301  on, and the system would return to the initial power supply configuration.  
         [0020]     It should be noted that many different methods may be implemented to hold the effective output voltage to the level of the next lowest power supply. The resistance selector system depicted in  FIG. 3  represents only one possible embodiment. Some embodiments may use a latching system or potentiometer to control the effect of the voltage drop across the isolation diodes. Moreover, the timer method used to reset the selectors in  FIG. 3  is also merely a single possible embodiment for creating an de-selecting mechanism. The methods shown in  FIG. 3  are not meant to be limited to solely those ways to implement the power supply system disclosed herein.  
         [0021]      FIG. 4  is a flow chart illustrating example steps  40  followed in implementing one embodiment of the present cascading power system. In step  400 , a plurality of power supplies are connected in parallel. In step  401 , a maximum effective voltage is set for each of the plurality of power supplies to cascade from a highest effective voltage for a first of the plurality to a lowest effective voltage for a last of the plurality. The plurality of power supplies are then interfaced with the electronic load through an isolation interface in step  402 .  
         [0022]      FIG. 5  is a flow chart illustrating example steps  50  followed in implementing an additional embodiment of the present cascading power system. In step  500 , a plurality of power supplies are connected in parallel. The plurality of power supplies are then interfaced with the electronic load through an isolation interface in step  501 . In step  502 , impedance values are selected within the isolation interface to create the maximum effective voltage for each of the plurality of power supplies to cascade from a highest effective voltage for a first of the plurality to a lowest effective voltage for a last of the plurality. In step  503 , current generated by one of the plurality of power supplies is prevented by the isolation interface from sinking into another of the plurality. In step  504 , the maximum effective voltage of one of the plurality of power supplies is limited to a value of a next one of the plurality when the electronic load causes the maximum effective voltage of the one of the plurality to decrease to the maximum effective voltage of the next one of the plurality. In step  505 , a signal may be received to deactivate the limit placed on the one of the plurality of power supplies. In response to receiving such a signal, the limiting is deactivated in step  506 .