Abstract:
A method to manage the power consumption of a display unit is provided. The method determines if a graphics-intensive event is occurring, uses a first refresh rate if the graphics-intensive event is occurring, and uses a second refresh rate different than the first refresh rate if the graphics-intensive event is not occurring. An apparatus for performing the method, and an article including a machine-accessible medium that provides instructions that, if executed by a processor, will cause the processor to perform the method are also provided.

Description:
TECHNICAL FIELD  
         [0001]    Methods, apparatuses, and articles for power management are disclosed. More specifically, methods, apparatuses and articles for power management of a display unit for use with a computing device are disclosed.  
         BACKGROUND  
         [0002]    Originally, computers were rather elaborate constructions, the earliest of which took several rooms to house. Over time, the size of the computer was reduced dramatically, such that a computer capable of being placed on a desktop became commonplace.  
           [0003]    Additional developments led to further reductions in the size of the computer, leading to computing devices having greater mobility and portability. In particular, a new type of portable computing device, commonly referred to as a laptop, was developed, together with a host of other portable computing devices, such as the Personal Digital Assistant (PDA), the mobile telephone and the like.  
           [0004]    However, mobility and portability comes at a cost. Lacking a connection to an external power source, portable computing devices require an on-board power source, typically in form of one or more batteries. While such batteries are usually rechargeable, there is a finite limit on the amount of time that a portable computing device may be used between charging events.  
           [0005]    As a consequence, power consumption is a very important consideration in the design of portable computing devices. Power consumption is also an important operational consideration, and the use of power management utilities and screensavers has become commonplace in laptop computers. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    The disclosed methods, apparatuses and articles are illustrated more or less diagrammatically in the accompanying drawings wherein:  
         [0007]    [0007]FIG. 1 is a block diagram of a portable computing device;  
         [0008]    [0008]FIG. 2 is a flow chart illustrating a first method of managing power consumption of a display unit; and  
         [0009]    [0009]FIG. 3 is a flow chart illustrating a second method of managing power consumption of a display unit. 
     
    
     DETAILED DESCRIPTION  
       [0010]    [0010]FIG. 1 shows an embodiment of a portable computing device  100 . In particular, the portable computing device  100  shown in FIG. 1 may be a laptop computer. However, this is merely by way of illustration and not by way of limitation, for the portable computing device  100  may also be a personal digital assistant (PDA), mobile phone, Linux machine, or any other computing device.  
         [0011]    The portable computing device  100  may include a processor  101 . The processor  101  may be operatively coupled via a CPU bus  110  to a bridge/memory controller  111 . The bridge/memory controller  111  may, in turn, be operatively coupled to a memory/data storage medium  113 .  
         [0012]    Furthermore, the bridge/memory controller  111  may be operatively coupled to a bus  120 . Via the bus  120 , the bridge/memory controller  111  may be operatively coupled to a network controller  121 , a display unit controller  122 , and a bus bridge  123 . As shown, the display unit controller  122 , which may include a processor, may be operatively coupled to a display unit  124 .  
         [0013]    The display unit  124  may be an LCD panel display, as is typically used for portable computing devices such as laptop computers, although this reference is not made by way of limitation, for other types of display units may be used as well, for example, cathode ray tubes (CRT). The display unit  124  may have at least two refresh rates. For example, the display unit  124  may have a first refresh rate of 50 Hz and a second refresh rate of 60 Hz. At the first refresh rate, the images generated on the display unit  124  may appear to flicker if there is movement within the image. On the other hand, at the second refresh rate, motion in images generated on the display unit  124  may tend to mimic the flow of normal motion, and there may be less image flicker occurring.  
         [0014]    The bus bridge  123  may be operatively coupled, via a bus  130 , to additional elements. For example, as shown in FIG. 1, the bus bridge  123  may be operatively coupled to a data storage medium  131 , a data storage medium interface  132  (e.g., a magnetic disk drive, a compact disk (CD) drive or a digital versatile disk drive (DVD) drive) and associated data storage medium  133  (e.g., a magnetic disk, a CD or a DVD), a keyboard interface  134  and an audio controller  135 .  
         [0015]    One or more sets of instructions may operate within the processor  101 . For example, an operating system (OS) may be operating within the processor  101 . According to the present embodiment, a set of instructions may also operate within the processor  101  to carry out a power management method. Alternatively, it will be recognized that a set of instructions may operate within the processor of the display unit controller  122 , for example, to carry out a power management method.  
         [0016]    In general terms, the power management method of the present embodiment may operate to vary the refresh rate of the display unit  124  according to the presence or absence of a graphics-intensive activity. As noted above, moving images generated on the display unit  124  operating at a slower refresh rate may experience more image flicker than when the display unit  124  is operating at a faster refresh rate. The power management method according to the present embodiment may cause the display unit  124  to use a slower refresh rate when there is a limited amount of motion in the images being generated, such as when a cursor is moving in response to the movement of a mouse or the entering of a character on a keyboard. On the other hand, the power management method may cause the faster refresh rate to be used when there is considerable motion in the images being generated by the display unit  124 , such as when a video is being shown or during the playing of a three-dimensional video game.  
         [0017]    Moreover, it will be recognized that while the power management method may described with reference to changes in the display unit refresh rate between a first refresh rate and a second refresh rate, the disclosed power management method is not limited to the use of only two refresh rates. For example, a series of refresh rates may be used, each for a different level of graphics-intensive activity. In such an instance, a highest level of activity may be defined as when a video or a three-dimensional video game is being displayed. An intermediate level, in turn, may be defined as when there is some level of activity, such as when the images displayed are responding to a series of keystrokes or mouse clicks, or movement of the pointer across the screen. A lowest level of activity may be defined as the circumstance where a static image is being displayed for viewing, as when a user is contemplating the information displayed on the display unit  122 . In such circumstances, a first refresh rate (e.g., 60 Hz) may be used at the highest level of activity, a second refresh rate (e.g., 50 Hz) may be used in the intermediate level, and a third refresh rate (e.g., 30 Hz) may be used at the lowest level. It will be further recognized that it is not necessary to define certain discrete levels of activity corresponding to specific refresh rates, but a continuum of activity may be defined corresponding to different rates within a range of refresh rates.  
         [0018]    [0018]FIGS. 2 and 3 are flow charts of different examples of the power management method. In FIG. 2, the method may monitor processor and operating system activity to make a determination about power management. In FIG. 3, the power management method may monitor the display unit controller activity to make determinations about power management.  
         [0019]    As shown in FIG. 2, a power management method  200  for use with a display unit, such as the display unit  124 , may start at block  202 . At the block  202 , the refresh rate of the display unit  124  may be set to a default rate which may limit image flicker and provide continuity of movement of images displayed by the display unit  124 . For purposes of illustration, the default rate may be 60 Hz for an LCD display unit. At block  204 , the power management method  200  may initiate monitoring of the processor  101 .  
         [0020]    At block  206 , the power management method  200  may determine if a graphics-intensive event is occurring. In particular, at block  206 , the power management method  200  may determine if the processor  101  is at an idle (e.g., C 3 ) state. If the processor  101  is at an idle state, then the power management method  200  may pass to block  208 , wherein the refresh rate of the display unit  124  may be changed to a second, slower refresh rate. That is, if the graphics-intensive event is not occurring, a second refresh rate which is slower than the first refresh rate may be used. For example, for an LCD display unit, the second refresh rate may be 50 Hz.  
         [0021]    Alternatively, if the power management method  200  detects that the processor  101  is not in the idle state or has recently changed from the idle state to a state other than the idle state (e.g., an active state), then the method may pass to block  210 . At block  210 , the refresh rate of the display unit  124  either may remain or may be changed to the first refresh rate. According to the example provided above, the default rate in this instance is 60 Hz. That is, if the graphics-intensive event is occurring, the first refresh rate which is faster than the second refresh rate may be used.  
         [0022]    It will be recognized that variations of the power management method  200  described above may be possible which remain within the scope of the present embodiment. As just one such example, for aggressive power management, the first refresh rate may be the slower of the two refresh rates. Using the numbers provided above for an LCD display unit, the first refresh rate may be 50 Hz. The method may then detect if the processor is not in the idle state, and change to a second, higher refresh rate (e.g., 60 Hz) if the processor is not in the idle state. If the processor remains at or changes to the idle state, the first, slower refresh rate may be used.  
         [0023]    By contrast, as shown in FIG. 3, a power consumption method  300  may monitor the operation of the display unit controller  122  as opposed to the processor  101 . For example, the display unit controller  122  may be programmed to provide data quantifying the work being performed by the display unit controller  122 , for example, the number of writes being made to the frame buffer, i.e., the frame buffer update. The determination as to whether a graphics-intensive event has occurred may then be made on either an absolute basis or a relative basis. For example, the change in a level of activity, such as the frame buffer update, may be viewed as to the absolute value of the activity, or whether the level of activity exceeds or drops below a threshold (e.g., a frame buffer update threshold). As an alternative, the determination as to whether a graphics-intensive event is occurring may depend on whether the display unit controller  122  is idle or whether the display unit controller  122  is active.  
         [0024]    Referring now to FIG. 3 in detail, the power management method  300  may begin at a block  302 , wherein the refresh rate of the display unit  124  is set to a default refresh rate, for example, 60 Hz for an LCD display unit. Monitoring of the display unit controller  122  may be initiated at block  304 . At block  306 , the power management method  300  may monitor the display unit controller  122  to determine whether a graphics-intensive event is occurring. If the graphics-intensive event has not occurred, the refresh rate of the display unit  124  may be set to the second lower level at block  308 , for example, 50 Hz for an LCD display unit. Alternatively, at block  310 , if the graphics-intensive event is occurring, then the refresh rate of the display unit  124  may remain at or may be changed to, for example, 60 Hz for an LCD display unit.  
         [0025]    It will be recognized that, as was explained above relative to FIG. 2, the power management method  300  described above may be altered or varied and yet remain within the scope of this embodiment. For example, the default refresh rate of the display unit  124  may be, for example, set to 50 Hz for an LCD display unit. In such a case, the program may determine whether a graphics-intensive event is occurring, in which case the refresh rate is changed from 50 Hz to 60 Hz. In the alternative, the refresh rate would remain at or be changed to 50 Hz.  
         [0026]    It will also be recognized that a set of instructions for implementing the power management method  200 ,  300  may be stored on a machine-accessible medium. A machine-accessible medium includes any mechanism that provides (i.e., stores and/or transmits) information in a form accessible by a machine (e.g., a computer, network device, personal digital assistant, manufacturing tool, any device with a set of one or more processors, etc.). For example, a machine-accessible medium includes recordable/non-recordable magnetic, optical and solid-state media (e.g., read only memory (ROM), programmable read only memory (PROM), erasable programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), random access memory (RAM), magnetic disk storage media, optical storage media, flash memory devices, etc.), as well as electrical, optical, acoustical or other form of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.), etc. According to the present embodiment, the machine-accessible medium may include the memory/data storage medium  113 , the data storage medium  131 , and/or the data storage medium  133 .  
         [0027]    The change of the refresh rate according to the power management method described above may have a consequential impact on the power consumption of the portable computing device  100 . The power consumption (P) of the portable computing device  100  because of the operation of the display unit  124  at a particular refresh rate may be calculated as follows: 
           P=F*C*V   swing   *V   supply   (eqn. 1) 
         [0028]    where  
         [0029]    F=line frequency=refresh rate * number of horizontal scan lines;  
         [0030]    C=capitance;  
         [0031]    V swing =V signal ; and  
         [0032]    V supply =power supply voltage  
         [0033]    With all other variables being constant, a measure of the change in the power consumption of the display unit  124  as a consequence of change in refresh rate may be reflected in a ratio of the power equations (eqn. 1) at the slower and faster refresh rates: 
         % change=100%−(refresh rate slower /refresh rate faster )*100%  (eqn. 2) 
         [0034]    With reference to this equation then, it will be recognized that the greater the difference between the slower and faster refresh rates used, the greater the change in the power consumption may be. Additionally, while these equations show the effect of change in refresh rate on power consumption of the display unit, the power consumption of other units, such as the memory controller and the display unit controller, will be impacted by the power management method.  
         [0035]    As mentioned previously, the use of such a power management method is not limited to portable computers, such as laptops.; Any computing device with a display unit, such as personal digital assistants (PDAs), mobile phones, and Linux machines, for example, may benefit from the above-mentioned power management method. In the example of a mobile phone, a first, slower refresh rate may be used with text messages, while a second, faster refresh rate may be used with streaming video.  
         [0036]    Furthermore, the disclosed structures and methods have been described with reference to foregoing examples. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of this disclosure. The above specification and figures accordingly are to be regarded as illustrative rather than restrictive. Particular materials selected herein can be easily substituted for other materials that would be apparent to those skilled in the art and would nevertheless remain equivalent to the disclosed devices and methods.