Abstract:
A method and system for adjusting a temperature of a bottom of a laptop computer housing depending on where the laptop computer is placed during operation. If the laptop computer is placed on a lap of a user, or alternatively on any surface that has direct contact with the bottom of the laptop computer housing, sensors on the bottom of the laptop computer housing are activated. The sensors produce a signal to initiate supplemental cooling measures to reduce the temperature of the bottom of the laptop computer housing. Cooling measures taken include decreasing an operating speed of logic circuits such as a central processing unit (CPU) or increasing cooling fan output.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates in general to the field of computers, and, in particular, to portable laptop computers. Still more particularly, the present invention relates to an improved method and system for detecting when a laptop computer housing is positioned on a user&#39;s lap, thus requiring adjustment to a heat management system of the computer to cool the bottom of the computer housing to prevent discomfort or injury to the user. 
     2. Description of the Related Art 
     Personal computers, including laptop computers, have acquired very high levels of computing power despite their relatively small size. Much of this computing power is due to the use of high density integrated circuit packages, including a central processing unit (CPU). These high density integrated circuit packages, and particularly the CPU, use a significant amount of electricity, which generates high levels of local heat within the laptop computer housing. For example, a typical CPU is rated to operate normally at temperatures up to 100° C. (212° F.) while generating over 50 watts of heat. This heat radiates throughout the computer housing, including the bottom surface of the computer housing. Under normal operating conditions, when placed on a desktop or other solid surface, the bottom of the computer housing does not get hot enough to pose a fire hazard or a serious health risk. However, despite the laptop computer&#39;s name, even under normal operating conditions the bottom of the laptop computer can get hot enough to cause discomfort or, in extreme conditions, even injury to a user who operates the laptop computer on the user&#39;s lap. 
     Thus, there is a need for a temperature control method and system for a laptop computer that is dependent on where the laptop computer is placed during operation, particularly with reference to placement of the laptop computer on the user&#39;s lap. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method and system for detecting when a laptop computer is placed on a lap of a user, thus indicating the need to keep the bottom of the laptop computer at a lower temperature to enhance the user&#39;s desired comfort level. The temperature of the bottom of the laptop computer is controlled by adjusting the amount of heat that radiates from an interior of the laptop computer housing to the bottom of the laptop computer housing. When the laptop computer is placed on the lap of the user, or alternatively another surface that has direct contact with the bottom of the laptop computer housing, sensors on the bottom of the laptop computer housing are activated. The sensors provide a signal to the laptop computer to initiate supplemental cooling measures to reduce the temperature of the bottom of the laptop computer housing. Supplemental cooling measures taken may include decreasing an operating speed of logic circuits such as a central processing unit (CPU), or increasing a cooling fan output. 
     The above, as well as additional objectives, features, and advantages of the present invention will become apparent in the following detailed written description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a block diagram of an exemplary computer system used in the present invention; 
     FIG. 2 a  depicts a cooling fan for a central processing unit (CPU) in the exemplary computer system; 
     FIG. 2 b  illustrates a thermal control circuit (TCC) for the CPU depicted in FIG. 2 a;    
     FIGS. 3 a - 3   c  depict pressure sensors and a temperature sensor on a bottom of a laptop computer housing; 
     FIGS. 4 a - 4   b  illustrate a non-contact of the pressure sensors when the laptop computer is placed on a flat tabletop, and a contact of pressure sensors when a laptop computer is placed on a lap of a user; and 
     FIG. 5 is a flow-chart of logic used in the present invention for taking cooling measures for the laptop computer based on whether the laptop computer is placed on the lap of the user. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference now to the figures and, in particular to FIG. 1, there is depicted a block diagram of a data processing system in which a preferred embodiment of the present invention may be implemented. Data processing system  10  may be, for example, one of the models of personal computers available from International Business Machines Corporation of Armonk, N.Y. Preferably, data processing system  10  is a laptop computer or a similar computer having a full-sized computer display  16 . Data processing system  10  includes a central processing unit (CPU)  12 , which is connected to a system bus  18 . In the exemplary embodiment, data processing system  10  includes a graphics adapter  14  also connected to system bus  18 , receiving user interface information for a display  16 . 
     Also connected to system bus  18  are a system memory  20  and an input/output (I/O) bus bridge  22 . I/O bus bridge  22  couples an I/O bus  24  to system bus  18 , relaying and/or transforming data transactions from one bus to the other. Peripheral devices such as nonvolatile storage  26 , which may be a hard disk drive, and input device  28 , which may include a conventional mouse, a trackball, or the like, is connected to I/O bus  24 . Also connected to I/O bus  24  is a BIOS ROM  21 , which contains a startup Power On Self-Test (POST) program. Contents of BIOS ROM  21  are located in a special region of CPU  12 &#39;s memory address space that CPU  12  accesses automatically upon start-up. 
     The exemplary embodiment shown in FIG. 1 is provided solely for the purposes of explaining the invention and those skilled in the art will recognize that numerous variations are possible, both in form and function. For instance, data processing system  10  might also include a compact disk read-only memory (CD-ROM) or digital video disk (DVD) drive, a sound card and audio speakers, and numerous other optional components. All such variations are believed to be within the spirit and scope of the present invention. 
     The CPU  12  described in FIG. 1 is preferably a microprocessor such as the Mobile Intel® Pentium® 4 processor or the Power PC™ manufactured by International Business Machines, Inc. of Armonk, N.Y. With reference now to FIG. 2 a , such an exemplary microprocessor is depicted as CPU  12 , which is mounted in a socket  38 , which is connected to a printed circuit board  40  for connection to other components in data processing system  10  depicted in FIG.  1 . Preferably, socket  38  includes a processor and fan heatsink (not shown) that facilitates conductive dissipation of heat away from CPU  12 . 
     In FIG. 2 a , mechanical cooling of CPU  12  is depicted in an exemplary form using a fan  32 . Fan  32  is mounted in a fan housing  30 , which is supported above CPU  12  by a fan housing support bracket  34 . Mechanical cooling of CPU  12  is accomplished by fan  32  forcing cooling air across CPU  12  and a plurality of cooling vanes  42  abutting CPU  12 . Cooling vanes  42  provide additional surface area to improve heat transfer away from CPU  12 , both passively and with the aid of forced air from fan  32 . As readily understood by those skilled in the art, other types of heat dissipation may be used with the present invention, including, but not limited to, heat pipes and/or remote heat exchangers (not shown). 
     With reference now to FIG. 2 b , there is depicted a CPU thermocouple  44 , preferably a factory tuned, precision on-die thermal sensor, which is exemplarily mounted on an interior surface of a top of CPU  12 . CPU thermocouple  44  provides a signal that is representative of a surface temperature of CPU  12 . The signal from CPU thermocouple  44  is processed either with hardware or software to provide a required level of cooling to CPU  12 . For example, CPU thermocouple  44  can provide a signal, typically analog in nature, to hardware that, when a threshold signal level is reached indicative of a upper limit temperature, switches on fan  32  or increases the rotational speed of fan  32 . Alternatively, CPU thermocouple  44  can provide an analog signal that is processed into a digital signal, which is then interpreted and processed by software in CPU  12  or other logic circuitry to turn on or speed up fan  32  when the surface temperature of CPU  12  reaches a threshold limit. 
     In a preferred embodiment, the analog signal generated by CPU thermocouple  44  is converted into a digital signal by thermal control circuit (TCC)  45 , which controls a temperature of CPU  12  by modulating (starting and stopping) a processor core clock  47  shown in FIG. 2 b . Preferably, processor core clock  47  can be modulated only when TCC  45  is activated. CPU  12  has two modes that activate TCC  45 : automatic mode and on-demand mode. In a preferred embodiment, TCC  45  can be implemented either physically in a circuit (not shown), as code in a dedicated processor (not shown), or virtually as power management code in CPU  12  itself. TCC  45  is illustrated as a discrete function in this application for purposes of clarity. 
     Automatic mode is required for CPU  12  to operate within pre-determined specifications, and must first be enabled by instructions from the BIOS ROM  21  shown in FIG.  1 . Once automatic mode is enabled, TCC  45  will activate only when a temperature within CPU  12 , as measured by CPU thermocouple  44 , reaches a pre-determined level. This pre-determined temperature level within CPU  12  is the temperature that will result in an upper allowable temperature level at the bottom of a laptop housing. That is, since CPU  12  accounts for the majority of heat generated within a laptop data processing system  10 , controlling the temperature of CPU  12  will have the primary control of the temperature of data processing system  10 , including a computer housing surrounding data processing system  10 . In particular, when data processing system  10  is a laptop computer, controlling the temperature of CPU  12  will result in controlling the temperature of the bottom of the laptop computer housing. 
     In the automatic mode, processor core clock  47  is modulated by alternately turning off and on at a duty cycle specific to CPU  12 . Cycle times are processor speed dependent and decrease linearly as processor core frequencies increase. Once the temperature of CPU  12  returns below the pre-determined threshold, modulation ceases and TCC  45  goes inactive. A small amount of hysterisis is preferably included to prevent rapid active/inactive transitions of TCC  45  when the temperature of CPU  12  is near the threshold. 
     TCC  45  may also be activated via on-demand mode, wherein the duty cycle of the clock modulation is programmable. In automatic mode, the duty cycle is fixed, while in on-demand mode, the duty cycle can be programmed to different on/off ratios. 
     Referring now to FIG. 3 a , there is depicted a bottom surface  49  of a laptop computer housing  48 , which houses the data processing system  10  illustrated in FIG.  1 . Mounted on bottom surface  49  are pressure sensors  50 . Pressure sensors  50  may be two sensors, as depicted, or alternatively may be a larger number of sensors or may be a single sensor. As seen in FIG. 3 b , pressure sensors  50  are mounted such that support legs  52  extend farther away from bottom surface  49  than pressure sensors  50 . Thus, when data laptop computer housing  48  is placed on a flat surface such as a desktop, pressure sensors  50  are not contacted. However, when laptop computer housing  48  is placed on a moldable surface such as a lap of a user, pressure sensors  50  are contacted and generate a signal indicating that the laptop computer housing  48  is on the user&#39;s lap. Pressure sensors  50  may be micro switches, strain gauges, membrane switches or any other pressure sensing switch device known in the art of pressure sensing. 
     When pressure sensors  50  are activated by pressure, pressure sensors  50  send a signal to TCC  45  to adjust the temperature of CPU  12  to a level that will not result in bottom surface  49  becoming too hot. Preferably, this temperature adjustment is accomplished with the use of CPU thermocouple  44  as described above. 
     In an alternate preferred embodiment, CPU  12 &#39;s temperature is controlled by pressure sensors  50  and casing thermal sensor  54 . Using analog or digital circuitry (not shown), pressure sensors  50  send a signal to thermal sensor  54 , thus activating thermal sensor  54 . When the activated thermal sensor  54 , which is mounted against either the interior or exterior of bottom surface  49 , detects a temperature above a pre-determined safe and/or comfortable level, thermal sensor  54  sends a signal to TCC  45 , located within laptop computer housing  48 . That is, if pressure is applied to pressure sensors  50  from the user&#39;s lap, then a temperature signal is sent from thermal sensor  54  to TCC  45 . If the temperature detected by thermal sensor  54  is higher than comfortable for the user, then thermal sensor  54  activates TCC  45  in a manner analogous to that described above using CPU thermocouple  44 . That is, upon a signal from thermal sensor  54  that the bottom surface  49  is too hot and is resting on the user&#39;s lap (as detected by pressure sensors  50 ), TCC  45  slows down the speed of CPU  12  by slowing down processor core clock  47 , thus allowing CPU  12  to cool down. When bottom surface  49  cools down to a predetermined temperature, CPU  12  is accelerated, after a hysterisis delay, back up to a higher clock speed. 
     In another preferred embodiment, cooling of laptop computer housing  48  and bottom surface  49  is accomplished by increasing the operation of fan  32  described in FIG. 2 a  and/or other fans (not shown) within laptop computer housing  48 . The increased usage of fans may be in conjunction with slowing the speed and thus heat output of CPU  12  as described above, or increased usage of fans may be utilized instead of slowing down CPU  12 . 
     Increased usage of a fan, including fan  32 , within laptop computer housing  48 , is a function of fan speed controller (FSC)  60 , as depicted in FIG. 3 c . When pressure is detected by pressure sensors  50 , indicating that laptop computer housing  48  is resting on the lap of the user, thermal sensor  54  is enabled. If the temperature of bottom surface  49  is too high, FSC  60  increases the output of a fan such as fan  32  for CPU  12 , or any other cooling fan within laptop computer housing  48 . The increased output is caused by either turning on the fan, or by increasing the speed of the fan if already running. The output of the fan is maintained at the higher level until thermal sensor  54  indicates a lower comfortable temperature at bottom surface  49 . Alternatively, FSC  60  increases the use and/or speed of fan  32  upon a signal generated by a high temperature detected by CPU thermocouple  44 . 
     With reference now to FIGS. 4 a  and  4   b , there is depicted the present invention while placed on a flat table top  75  (FIG. 4 a ) or a user&#39;s lap (FIG. 4 b ). As seen in FIG. 4 a , when placed on flat table  75 , laptop computer housing  48  is supported by support legs  52 , thus avoiding any pressure against pressure sensors  50 . Without pressure being detected against pressure sensors  50 , TCC  45  does not alter its normal settings and operation to further reduce the temperature of a computer bottom surface  49 , nor is the operation of fan  32  increased. However, when the laptop computer housing  48  is placed on a user&#39;s lap, as depicted in FIG. 4 b , computer bottom surface  49  is now supported, along with laptop computer housing  48 , by the lap (legs) of the user. The user&#39;s legs press against pressure sensors  50 , causing TCC  45  to adjust CPU clock speed as described above, resulting in computer bottom surface  49  having a lower temperature to avoid burning the lap of the user. Alternatively, pressure on pressure sensors  50  results in additional fan usage as described above. Note that when placed on the lap of the user, the CPU clock speed and/or the fan usage are adjusted to control the temperature of computer bottom surface  49 . That is, the CPU clock speed may be adjusted, the fan usage may be adjusted, or both the CPU clock speed and fan usage may be adjusted to control the temperature of the computer bottom surface  49 . 
     With reference now to FIG. 5, there is depicted a flow chart of a preferred embodiment of the present invention. Starting at query block  80 , an inquiry is made as to whether pressure is detected on the bottom of the laptop computer. If not, then no further steps are taken, as it is assumed that the laptop is sitting on a desktop, and not on the lap of the user. If the computer is positioned on the user&#39;s lap, a query, as shown in block  82 , is made as to whether the temperature on the bottom of the computer is above an acceptable level that is safe and comfortable for the user. The temperature on the bottom of the computer can be determined by a direct measurement of the temperature using thermal sensor  54  on the bottom of the computer, as described in FIGS. 3 a - 3   c , or the temperature of the bottom of the computer may be determined indirectly based on the temperature of CPU  12  or some other component of the laptop computer, as described in FIG. 2 b.    
     If the temperature on the bottom of the laptop computer is too high, a query, as shown in block  84 , is made as to whether the program(s) currently running on the laptop computer can operate at a lower CPU speed. If so, the CPU speed is decreased as described above. If the CPU is running at a lowest acceptable speed, then the output of the cooling fan is increased, as shown in block  88 , either by turning on the cooling fan or by speeding up the cooling fan. 
     It should further be appreciated that the method described above can be embodied in a computer program product in a variety of forms, and that the present invention applies equally regardless of the particular type of signal bearing media utilized to actually carry out the method described in the invention. Examples of signal bearing media include, without limitation, recordable type media such as floppy disks or compact disk read only memories (CD ROMS), and transmission type media such as analog or digital communication links. 
     While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.