Abstract:
An information handling system (“IHS”) includes a system board and a power supply unit coupled to the system board. The power supply unit includes a switching power regulator. The switching power regulator includes an inductor coupled to an output, a capacitor coupled to the inductor, a switch, coupled to the inductor, for regulating power supplied by the power supply unit in response to a duty cycle, and a control circuit, coupled to the switch, for supplying current to the inductor while the switch is closed and charging the capacitor while the switch is open.

Description:
BACKGROUND  
       [0001]     The description herein relates generally to information handling systems (“IHSs”) and more particularly to an IHS that includes a power supply unit with a switching regulator that reduces transient load release.  
         [0002]     As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option is an information handling system (“IHS”). An IHS generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes. Because technology and information handling needs and requirements may vary between different applications, IHSs may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in IHSs allow for IHSs to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, IHSs may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.  
         [0003]     An IHS typically includes a power supply unit for supplying regulated power to its various components. In one example, a power supply unit includes a switching regulator for regulating power supplied via a power converter.  
         [0004]     Such power supply unit including a switching regulator may cause various problems in an IHS. For example, in a situation whereby a load level (e.g., as demanded by a component being powered) of the power supply transitions relatively quickly from a relatively high load (e.g., close to maximum load) to a relatively low load (e.g., close to a minimum load), the IHS may be subject to a load step transient. In such situation voltage level of the switching regulator may rise rapidly because of energy stored in the regulator&#39;s output inductor. Such rise in voltage level may damage the IHS.  
         [0005]     What is needed is a method and an IHS that includes a power supply unit with a switching regulator, without the disadvantages discussed above.  
       SUMMARY  
       [0006]     Accordingly, a method of operating a power supply unit including a switching power regulator including an inductor coupled to an output, a capacitor coupled to the inductor, and a switch, coupled to the inductor, for regulating power supplied by the power supply unit in response to a duty cycle is provided. The method includes supplying current to the inductor while the switch is closed and charging the capacitor while the switch is open. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]      FIG. 1  is a block diagram of an information handling system (“IHS”) according to one embodiment.  
         [0008]      FIG. 2 . is a more detailed block diagram of the IHS of  FIG. 1 .  
         [0009]      FIG. 3  is a circuit diagram of a switching regulator, according to one embodiment. 
     
    
     DETAILED DESCRIPTION  
       [0010]     For purposes of this disclosure, an information handling system (“IHS”) may include any instrumentality or aggregate of instrumentalities operable to compute, classify, process, transmit, receive, retrieve, originate, switch, store, display, manifest, detect, record, reproduce, handle, or utilize any form of information, intelligence, or data for business, scientific, control, entertainment, or other purposes. For example, an IHS may be a personal computer, a PDA, a consumer electronic device, a network server or storage device, a switch router or other network communication device, or any other suitable device and may vary in size, shape, performance, functionality, and price. The IHS may include memory, one or more processing resources such as a central processing unit (“CPU”) or hardware or software control logic. Additional components of the IHS may include one or more storage devices, one or more communications ports for communicating with external devices as well as various input and output (I/O) devices, such as a keyboard, a mouse, and a video display. The IHS may also include one or more buses operable to transmit communications between the various hardware components.  
         [0011]      FIG. 1  is a block diagram of an IHS, indicated generally at  100  according to an illustrative embodiment. The IHS  100  includes a system board  105 . The system board  105  includes components (e.g., various devices such as memory devices)  110 . Examples of the components  110  are discussed in more detail below in connection with  FIG. 2 .  
         [0012]     The IHS  100  also includes a power supply unit  115  coupled to the system board  115 . The power supply unit  115  receives power from a power source, as depicted in  FIG. 1 , and supplies power to the various components  110  of the system board  105 . The power supply unit  115  is discussed in more detail below in connection with  FIG. 3 .  
         [0013]      FIG. 2  is a more detailed block diagram of the IHS  100 . The IHS  100  includes a processor  205  (e.g., an Intel Pentium series processor) for executing and otherwise processing instructions, input devices  210  for receiving information from a human user, a display device  215  (e.g., a cathode ray tube (“CRT”) device, a projector, a liquid crystal display (“LCD”) device, or a plasma display device) for displaying information to the user, a storage device  220  (e.g., a non-volatile storage device such as a hard disk drive or other computer readable medium or apparatus) for storing information, a memory device  225  (e.g., random access memory (“RAM”) module and read only memory (“ROM”) modules), also for storing information, and a network controller  230  for communicating between the IHS  100  and a network. Examples of the memory device  225  include single in-line memory modules (“SIMMS”) and double in-line memory modules (“DIMMS”) such as fully-buffered DIMMs (“FB-DIMMs”).  
         [0014]     Each of the input devices  210 , the display device  215 , the storage device  220 , the memory device  225 , and the network controller  230  is coupled to the processor  205 , and to one another. Also, in one example, the IHS  100  includes various other electronic circuitry for performing other operations of the IHS  100 , such as a print device (e.g., a ink-jet printer or a laser printer) for printing visual images on paper.  
         [0015]     The input devices  210  include, for example, a conventional keyboard and a pointing device (e.g., a “mouse”, a roller ball, or a light pen). A user operates the keyboard to input alphanumeric text information to the processor  205 , and the processor receives such information from the keyboard. A user also operates the pointing device to input cursor-control information to the processor  205 , and the processor  205  receives such cursor-control information from the pointing device.  
         [0016]     As discussed above, the power supply unit  115  including a switching regulator may cause problems in the IHS  100  associated with load step transient. For example, in a situation whereby a load level (e.g., as demanded by a component being powered) of the power supply transitions relatively quickly from a relatively high load (e.g., close to maximum load) to a relatively low load (e.g., close to a minimum load), the IHS is the cause of a load step transient. In such situation, voltage level of the switching regulator may rise rapidly because of energy stored in the regulator&#39;s output inductor and subsequent interaction with the output capacitance. Such rise in voltage level may damage the IHS  100  or cause it to malfunction (e.g., the various components of the IHS  100 ).  
         [0017]     In the illustrative embodiment, the power supply unit includes a switching regulator which forms a relatively large voltage discrepancy (e.g., “voltage drop”) across its output inductor. Accordingly, the output inductor of the switching regulator is capable of discharging its stored energy relatively quickly.  
         [0018]      FIG. 3  is a circuit diagram of a switching regulator, indicated generally at  300 , included in the power supply unit  115  of  FIG. 1 . The switching regulator  300  includes an input  305 , a control circuit  310 , a switch  315 , a switch  320 , a switch  325 , a resistor  330 , a switch  335 , a capacitor  390 , an output inductor  340 , an output  345 , a load  350 , and a voltage feedback line  355 . A capacitor  341  is connected to ground between inductor  340  and output  345 . In the illustrative embodiment, switches  320  and  325  must be capable of blocking voltage in both directions. Switches  315  and  335  need to be able to block voltage in one direction, e.g. MOSFETS, but can be capable of blocking voltage in both directions, e.g. JFETS.  
         [0019]     The switching regulator  300  is a DC to DC, synchronous, buck type, switching regulator. Accordingly, the input  305  is coupled to receive current from a DC power source (not shown) such as, for example, a battery or a AC/DC rectifier.  
         [0020]     In a switching operation, the control circuit repeatedly opens and closes the switches  315  and  320  according to a duty cycle to provide current to the load  350  via the output inductor  340  and the output  345 . Accordingly, the control circuit  310  is coupled to the switches  315 ,  320 ,  325  and  335 .  
         [0021]     For increasing voltage drop across the output inductor  340 , the switching regulator  300  charges the capacitor  390  during normal switching. More particularly, during periods of the duty cycle in which the control circuit  310  turns off the switch  315 , the control circuit  310  turns on the switches  320  and  325 .  
         [0022]     By comparison, during periods of the duty cycle in which the control circuit turns on the switch  315 , the control circuit  310  turns off the switches  320  and  325 . Accordingly, during such periods, the switching circuit  300  supplies current to the output  345 .  
         [0023]     The control circuit receives an indication of level of voltage at the output  345  via the voltage feedback line  355 . A rising voltage level at the output  345  potentially indicates that the load  350 &#39;s demand is becoming lower, thereby also indicating the potential for transient load release. Accordingly, in response to detecting a rise (e.g., a rise by a predetermined amount) in voltage level at the output  345 , the control circuit performs an operation to maintain the output voltage.  
         [0024]     As discussed above, the switching circuit  300  charges the capacitor  390  during normal switching operation. Thus, voltage drop across the output inductor  340  is potentially increased. Accordingly, in response to detecting a rise in voltage level at the output  345 , the control circuit  310  opens the switches  315 ,  320 , and  325 . Also in response to detecting such rise, the control circuit  310  closes the switch  335 , thereby increasing a negative voltage across the output inductor  340 . In response to the control circuit opening the switches  315 ,  320 , and  325  and closing the switch  335 , the output inductor  340  discharges its energy into the capacitor  390  thereby maintaining the output voltage.  
         [0025]     With regard to the resistor  330 , the purpose is to limit current through input  305 , switch  325 , capacitor  390  and switch  320 . Therefore, this could also be accomplished by the parasitic resistance in one or more of the above-mentioned components, by the resistor  330 , or by the variable gate drive of the switch  325 .  
         [0026]     Although illustrative embodiments have been shown and described, a wide range of modification, change and substitution is contemplated in the foregoing disclosure. Also, in some instances, some features of the embodiments may be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be constructed broadly and in manner consistent with the scope of the embodiments disclosed herein.