Abstract:
A power manager of an information handling system selectively commands a first or second source voltage from an AC-to-DC adapter based upon power consumption of the information handling system. A lower direct current voltage is provided during reduced power consumption so that DC-to-DC conversion in a power supply is more efficient. A higher direct current voltage is provided during increased power consumption so that the current required to provide the increased power remains below a threshold current, thus allowing the power system to have components that operate at lower current levels under high power consumption operations yet with increased efficiency during low power consumption operations.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates in general to the field of information handling system power management, and more particularly to a system and method for information handling system power management by variable direct current input. 
         [0003]    2. Description of the Related Art 
         [0004]    As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems 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 information handling systems allow for information handling systems 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, information handling systems 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. 
         [0005]    Information handling systems perform a wide variety of functions that consume different amounts of power. For example, simple web browsing or e-mail functions typically consume relatively little power while more computationally intensive functions tend to consume more power, such as running math applications or playing games. Power consumption also increases with the use of peripheral devices, such as playing movies in an optical drive. Generally, information handling systems have power supplies that are capable of providing power to operate components at their highest power consumption levels. Power supplies generally accept power from an external alternating current source, convert the power to a set direct current voltage level and then supply power to components through power rails that carry power direct current voltage adapted to components of the power rail. As an example, an AC-to-DC power adapter converts 120 VAC provided at an outlet to 12 VDC and then a power supply converts the 12 VDC to 5, 3 or 1.5 VDC that are used by components, such as CPUs or chipsets. Desktop information handling systems typically include the AC-to-DC converter in the housing that holds other electronic components while portable information handling systems typically use an external AC-to-DC converter that connects to the housing with a cable that provides a DC Voltage. 
         [0006]    Over time, information handling system components have developed improved processing capabilities, however, these greater processing capabilities have often meant increased power consumption. For a number of reasons, increased power consumption has had the greatest impact on portable information handling systems. One reason for this is that portable information handling systems are designed to run on internal batteries so that greater power consumption means reduced battery charge life. Another reason is that portable information handling systems operate on external power with a DC voltage cable coupled to the system housing. In systems that have relatively low power consumption, the external AC-to-DC adapter operates at 12 or 14.5 VDC, however, in systems with greater power consumption, such as power consumption of 90 Watts or greater, the external AC-to-DC adapter typically operates at a higher voltage in order to reduce the current needed for a given power consumption, such as at 19.5 VDC. For example, operating at 19.5 VDC instead of 12 VDC allows current of 4.6 A instead of 7.5 A. The lower current used with higher voltage levels allows for a smaller diameter cable between the AC-to-DC adapter as well as smaller DC connectors and parts with reduced current ratings at the power input loop of the power supply within the information handling system. A disadvantage to the use of a higher DC Voltage input is that DC-to-DC converters of the information handling system tend to operate less efficiently at the higher Voltage levels. 
       SUMMARY OF THE INVENTION 
       [0007]    Therefore a need has arisen for a system and method which manages information handling system power consumption with variable direct current voltage inputs. 
         [0008]    In accordance with the present invention, a system and method are provided which substantially reduce the disadvantages and problems associated with previous methods and systems for managing information handling system power consumption. Voltage output from an AC-to-DC adapter is adjusted based on the power consumption of an information handling system to maintain current below a desired threshold yet conserve power with reduced voltage outputs when power consumption allows. 
         [0009]    More specifically, an information handling system has plural electronic components that consume direct current power. A power manager of the information handling system monitors power consumption by the electronic components and adjusts the direct current source voltage provided from the adapter. If power consumption exceeds a threshold, such as a current threshold, then the power manager commands the adapter to output an increase direct current voltage. If power consumption falls below a threshold, such as a current threshold, then the power manager commands the adapter to output a decreased direct current voltage. The decrease direct current voltage level allows for improved efficiency of DC-to-DC converters that convert the source voltage provided from the adapter to destination voltages for use by the electronic components. 
         [0010]    The present invention provides a number of important technical advantages. One example of an important technical advantage is that direct current voltage input to an information handling system power supply has a lower voltage level for low power consumption levels that improves system efficiency and a higher voltage level for high power consumption levels that maintains input current below a desired threshold. With lower direct current voltage inputs, DC-to-DC power conversion has improved efficiency compared to higher direct current voltage inputs. When system power consumption increases, a higher direct current voltage input allows supply of increased power while maintaining a reduced current level so that power subsystem components designed for reduced current levels will operate at higher power consumption levels. In various embodiments and at various power consumptions, information handling systems that reduce voltage from an adapter to 14 VDC from 19.5 VDC save as much as approximately 30% of power consumption. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The present invention may be better understood, and its numerous objects, features and advantages made apparent to those skilled in the art by referencing the accompanying drawings. The use of the same reference number throughout the several figures designates a like or similar element. 
           [0012]      FIG. 1  depicts a block diagram of an information handling system having a power manager that manages power consumption by varying direct current voltage provided to an information handling system; 
           [0013]      FIG. 2  depicts a circuit diagram of system that coordinates variations in direct current voltage provided to an information handling system to manage power consumption by electronic components of the information handling system; and 
           [0014]      FIG. 3  depicts a flow diagram of a process for managing direct current source voltage provided to an information handling system for conversion to destination voltages used by electronic components of the information handling system. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Managing direct current source voltage provided to an information handling system aids in efficient conversion to destination voltages used by electronic components with reduced power consumption operation while maintaining current within a desired threshold during high power consumption operation. For purposes of this disclosure, an information handling system 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, or other purposes. For example, an information handling system may be a personal computer, a network storage device, or any other suitable device and may vary in size, shape, performance, functionality, and price. The information handling system may include random access memory (RAM), one or more processing resources such as a central processing unit (CPU) or hardware or software control logic, ROM, and/or other types of nonvolatile memory. Additional components of the information handling system may include one or more disk drives, one or more network 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 information handling system may also include one or more buses operable to transmit communications between the various hardware components. 
         [0016]    Referring now to  FIG. 1 , a block diagram depicts an information handling system  10  having a power manager  12  that manages power consumption by varying direct current voltage provided to information handling system  10 . Information handling system  10  has a plurality of electronic components that cooperate to process information, such as a CPU  14 , RAM  16 , a hard disk drive  18 , a chipset  20  and an embedded controller  22 , also sometimes referred to as a keyboard controller. The electronic components operate with power provided from a power supply  24  through power rails  26 . Power supply  24  accepts power from an AC-to-DC adapter  28  through a power cable  30  at a source direct current voltage and converts the source direct current voltage to one or more destination direct current voltages with DC-to-DC converters  32 . The destination direct current voltages provided through power rails  26  are typically between 5 and 1.5 VDC required by the electronic components. As depicted by  FIG. 1 , the electronic components are disposed in a housing  34  along with a display  36  in a portable information handling system configuration that has AC-to-DC adapter  28  separate from housing  34  and connected by to power supply  24  with an external power cable  30 . In desktop or other non-portable information handling system configurations, AC-to-DC adapter  28  may be integrated within the same housing  34  as the electronic components. 
         [0017]    In operation, power manager  12  manages power consumption of information handling system  10  by managing the source direct current voltage provided from AC-to-DC adapter  28  to power supply  24 . During operations with reduced power consumption, such as approximately 60 Watts or less, power manager  12  commands AC-to-DC adapter  28  to output a reduced direct current voltage, such as 14 VDC, so that DC-to-DC converters  32  operate with greater efficiency than is available at higher source direct current voltages. For example, power manager  12  is firmware running on embedded controller  22  that communicates through power cable  30  with an adapter manager  38 . During operations at information handling system  10  that consume approximately 60 Watts or less, power manager  12  sends a signal to adapter manager  38  through power cable  30  to output a reduced source voltage from converter circuits  40 , such as 14 VDC. As power consumption increases at information handling system  10  to approximately 60 Watts or greater, power manager  12  commands an increased source voltage, such as 19.5 VDC. Although the increased source voltage causes DC-to-DC converters  40  to operate with less efficiency, the higher source voltage allows greater power with a decreased current so that power components may have less robust features than would be required for the same amount of power provided at the reduced source voltage and resulting increased current. For example, power manager  12  maintains the reduced source voltage of approximately 14 VDC until current through cable  30  reaches a 4.3 Amp threshold. Once the current threshold is met, power manager  12  commands the higher source voltage, such as 19.5 VDC, which has a decreased current. If current across cable  30  decreases below another current threshold during operation at the higher source voltage, such as approximately 4 Amps, then power manager  12  commands a decrease in source voltage to take advantage of power savings available from efficiencies in DC-to-DC conversion from the lower source voltage to the destination voltages. During changes in the source voltage, power supply  24  continues to provide the destination voltage to the electronic components so that the components continue to operate normally. 
         [0018]    Referring now to  FIG. 2 , a circuit diagram depicts a system that coordinates variations in direct current voltage provided to an information handling system  10  to manage power consumption by electronic components of the information handling system. AC-to-DC adapter  28  has a power manager  38  that monitors a PSID line  42  to determine the amount of direct current voltage to output. If PSID line  42  has a low value, then the output at V_DC equals (1+R 2 /R 1 )*2.5 and the value at V_DC is set at 13.5 VDC. If PSID line  42  has a high value, then the output at V_DC equals (1+R 2 /(R 1 /R 3 ))*2.5 and is set at 19.5 VDC. The signal sent across PSID  42  to set V_DC is determined by power manager  12  based on the current that passes through V_DC. V_ACIN is set at (1+R 4 /R 5 )*2.048 sets a threshold of 16.8V to set PSID high. V_ACIN is set at (1+R 4 /(r 5 /R 4 ))*2.048 sets a threshold of 12V to set PSID low. In summary, if power consumption increases above a set threshold while V_DC is 13.5 VDC, then PSId  42  signals high to increase the voltage output by adapter  20  to 19.5 VDC. If power consumption decreases below a set threshold while V_DC is set at 19.5 VDC, then PSID  42  signals low to decrease the voltage output by adapter  20  to 13.5 VDC. 
         [0019]    Referring now to  FIG. 3 , a flow diagram depicts a process for managing direct current source voltage provided to an information handling system for conversion to destination voltages used by electronic components of the information handling system. The process begins at step  44  when an AC-to-DC adapter is detected connected to the information handling system. A counter is zeroed at step  46  and at step  48  a determination is made of whether a count is less than 25. If the count is less than 25, the process continues to step  50  to set the GPIO PSID pin to a high impedance and to step  52  to issue a warning that the adapter is not a correct adapter for the information handling system. If the count is less than 25 at step  48 , the process continues to step  54  to set the GPIO PSID pin to a low value a short time, such as ten microseconds. At step  56 , the GPIO PSID pin is changed to an input and at step  58  data is read from the PSID line to determine the identification of the adapter. If at step  60  the adapter is not a correct adapter for the information handling system, the process continues to step  62  to increment the counter and returns to step  48  to attempt to read PSID data again. If the adapter is a correct adapter for the information handling system, the process continues to step  64 . This process of identification of the adapter is performed in a conventional manner. 
         [0020]    Once the adapter is identified as correct for the information handling system and capable of outputting varying direct current source voltages, the process continues to step  64  to compare the current provided from the adapter with a current threshold, such as 4.3 Amps. If the current is greater than or equal to 4.3 Amps, the process continues to step  68  to step the GPIO PSID pin to high always so that the adapter outputs a high source voltage, such as 19.5 VDC. If the current is less than 4.3 Amps, the process continues to step  66  to set the GPIO PSID pin to low always so that the adapter outputs a low source voltage, such as 13.5 VDC. The process iterates back to step  64  to periodically compare the current provided from the adapter and to adjust the output source voltage so that the current does not exceed a predetermined threshold. 
         [0021]    Although the present invention has been described in detail, it should be understood that various changes, substitutions and alterations can be made hereto without departing from the spirit and scope of the invention as defined by the appended claims.