Patent Abstract:
An information handling system projector cooling fan runs for a variably defined time after its lamp is turned off in order to adequately cool the projector without running the cooling fan for an excessive cool down period. In one embodiment, the cooling fan runs after lamp shut down until one or more thermocouples detects a predetermined temperature associated with the projector. In an alternative embodiment, fan cool down time varies based on the length of time the lamp was on before shutdown. The cool down thermal gradient is selectable between a convenience mode, in which an increased cooling gradient allows quicker cooling fan shut down, and a long-life mode, in which a decreased cooling gradient preserves lamp life.

Full Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates in general to the field of information handling system projectors, and more particularly to a system and method for intelligent information handling system projector cool down. 
   2. Description of the Related Art 
   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. 
   Information handling systems often interact with a number of peripherals to communicate, print, display or otherwise process information. For instance, information handling systems often display information by using projectors. Projectors generate images with a LCD panel, illuminate the image with a bright lamp, and present the image through a lens focused against a distal screen. Projectors aid in the presentation of information from an information handling system to a group of individuals and, thus, have become a popular way to present information in business meetings. Typically, a presenter prepares information on a portable information handling system using applications such as POWERPOINT by MICROSOFT and carries the information handling system and projector to the meeting. At the meeting, the presenter connects the information handling system to the projector and illuminates images provided from the information handling system with the projector for other attendees of the meeting to see. After the presentation, the projector and information handling system are generally powered down and then taken by the presenter when the meeting is complete. In today&#39;s fast paced business environment, presenters often make repeated presentations in various locations during the course of a day so that a typical projector may be powered up and shut down repeatedly during the course of a day. 
   One difficulty associated with the use of projectors to display information is that the lamps used to illuminate the information produce substantial amounts of heat during illumination. In order to ensure proper operation of the electronic components within the projector as well as the lamp, projectors are typically equipped with cooling fans that transport heat from the projector during operation. However, when the lamp is not illuminated, the cooling fans typically turn off after a defined time period in order to reduce the noise produced incidental to the operation of the cooling fans. Generally, projector cooling fans are designed to remain on for the defined period after the illumination from the lamp is ended so that the lamp and projector components receiving cooling air to reduce their temperature. However, users sometimes interrupt post-operation cooling by unplugging the projector before the defined period is complete. For instance, users are often in a rush after completing a presentation and do not want to wait for the predefined period to end. Also, running the cooling fans after completion of a presentation often annoys users who prefer to have a post-presentation discussion in quiet without the cooling fan noise in the background. Unplugging the projector to shut down cooling fan operation before the lamp and projector components have cooled typically reduces the life of the lamp and components, often leading to premature failure. 
   SUMMARY OF THE INVENTION 
   Therefore a need has arisen for a system and method which reduces projector cool down time after lamp shut down. 
   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 projector cool down after lamp shut down. A projector cooling fan runs for variably defined cool down periods after the projector lamp shuts down, the variably defined cool down period achieving desired projector cooling without excessive cooling fan operation. 
   More specifically, a projector cooling manager interfaces with a projector lamp and a projector cooling fan and detects the lamp as in an on or off state. When lamp transitions from the on to the off state, the cooling manager determines a variably defined cool down time and runs the cooling fan until the variably defined cool down time expires. The variably defined cool down time ensures adequate cooling for the lamp and the projector image processing components while running the cooling fan little if at all after the adequate cooling is complete. In one embodiment, the variably defined cool down time is determined based upon the length of time that the lamp was in the on state, with greater lamp operating times having greater cool down times. In another embodiment, thermocouples measure the projector temperature and provide the measured temperature to the cooling manager, which runs the cooling fan until the measured temperature is a predetermined temperature. The cooling manager cools the projector by running the fan in a convenience mode at a maximal cooling gradient that cools the projector in minimal time to achieve quicker cooling fan shutdown. Alternatively, the cooling manager cools the projector by running the fan in a long-life mode at a reduced cooling gradient that cools the projector more gradually to aid in maintaining a longer lamp life. 
   The present invention provides a number of important technical advantages. One example of an important technical advantage is that projector cool down time after lamp shut down is reduced to a period of time appropriate for the heat built up in the projector. Shorter projector run times that build up less heat have a shorter cool down times, thus reducing the inconvenience to users who would otherwise have to wait longer periods of time for the cooling fan to stop after lamp shut down. The time for fan operation after lamp shut down is variably defined by measured temperature within the projector or by expected temperatures predicted based on projector run time so that adequate cooling is assured after lamp shutdown to preserve lamp and projector component useful lifespan. The convenience cool down mode ensures adequate cooling in minimal time for quick projector shut down. Alternatively, the long-life cool down mode reduces the stress put on the lamp by rapid thermal gradients and reduces projector operating cost with less frequent replacement of expensive projector bulbs. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     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. 
       FIG. 1  depicts an information handling system projector having variably defined cool down periods after lamp shut down; 
       FIG. 2  depicts a flow diagram of a process for cool down periods variably defined based upon lamp operating times; 
       FIG. 3  depicts a flow diagram of a process for cool down periods variably defined based upon measured projector temperature; and 
       FIG. 4  depicts a flow diagram of a process for selecting a convenience or a long-life cool down gradient. 
   

   DETAILED DESCRIPTION 
   Variably defined cool down periods for information handling system projectors reduce the time a cooling fan runs after lamp shutdown for a selected cool down mode. 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. 
   Referring now to  FIG. 1 , a functional block diagram depicts an information handling system projector having variably defined cool down periods after lamp shut down. An information handling system  10  generates information, such as graphical images  14 , for display by a projector  12 . Image processing components  16  accept the information from information handling system  10  to formulate the image at an LCD  18 . A lamp  20 , such as a halogen light, illuminates LCD  18  aligned with lens  22  to project the image  14  distal to projector  12 . Power to generate and illuminate image  14  comes from a power supply  24  that connects at an external power source  26 , such as an AC socket. During operation of projector  12 , a cooling fan  28  runs to provide cooling airflow through the housing  30  that contains the projector components. The primary source of heat within housing  30  is lamp  20 . 
   A cooling manager  32  interfaces with lamp  20  and cooling fan  28  to manage operation of cooling fan  28  after shutdown of lamp  20  so that projector  12  receives cooling from fan  28  for a variably defined cool down period. In one embodiment, cooling manager  32  interfaces with one or more thermocouples  34  that determine the temperature of projector  12 . When cooling manager  32  detects a transition of lamp  20  from an on state to an off state, cooling manager  32  monitors the temperature of projector  12  and runs cooling fan  28  until the temperature drops to a predetermined level, such as a level that allows safe packaging of projector  12 . By using the measured temperature of projector  12 , cooling manager  32  ensures that cooling fan  28  operates long enough to achieve a cooled down state without additional unnecessary operation of cooling fan  28 . In an alternative embodiment, cooling manager  32  has a timer  36  and a cool down table  38 . Timer  36  tracks lamp  20  and cooling fan  28  operating time. Upon transition of lamp  20  from an on state to an off state, cooling manager  32  determines the lamp operating time from timer  36  and looks up a cool down time to run cooling fan  28  from a cool down table  38 . Cooling manager  32  runs cooling fan  28  for the cool down time associated with the detected lamp operating time and then shuts down cooling fan  28 . Cooling manager  32  runs on firmware in projector  12  and has timer  36  periodically read and stored timed values for use in the event of a power loss, such as disconnection from external power  26 . 
   The variably defined time is determined to minimize projector cooling fan  28  cool down running time while meeting projector operating goals. The amount of cool down time increases as lamp operating time increases and is determinable by experimentation of projector operating times compared with adequate cool down times for the operating times. A typical projector takes as long as fifty minutes to heat to a fully operational temperature, so lamp operating times of less than fifty minutes generally result in proportionally less operational temperatures and, thus, need proportionally less cool down times. However, lamp life is affected by the cooling gradient, or rate of cooling, used to cool the lamp. Rapid or high cooling gradients tend to reduce lamp life as internal metal parts contract. Thus, cooling manager  32  allows selection of convenience or long-life cool down modes. The convenience mode provides a high cooling gradient, such as cooling fan  28  operating at maximum speed, for the quickest cool down time and more rapid cooling fan shut down. The long-life mode provides a reduced cooling gradient, such as cooling fan  28  operating at a reduced speed, for a longer cool down time that places reduced thermal stress on lamp  20  for longer lamp life. Based on a user selection, cooling manager  32  looks up convenience or long-life cool down times from cool down table  38  and runs cooling fan  28  at the selected of a convenience or long-life speed for the time provided by cool down table  38 . Alternatively, cooling manager  32  tracks the temperature provided by thermocouple  34  and uses the measured temperature to vary the speed of cooling fan  28  to achieve a desired cool down rate. 
   Referring now to  FIG. 2 , a flow diagram depicts a process for cool down periods variably defined based upon lamp operating times. The process begins at step  40  when the projector turns on and continues at step  42  with an up-counter started to count projector operating time until, at step  44  the projector is turned off. At step  46  a determination is made of whether the counter reading is less than or equal to a first time period, such as 15 minutes, and, if yes, at step  48  the cooling fan is run for a first cool down time, such as 30 seconds. If the determination at step  46  is no, the process continues to step  50  for a determination of whether the counter reading is greater than or equal to a second time period, such as 30 minutes. If the determination at step  50  is yes, the process continues to step  52  for the cooling fan to run for a second cool down time, such as 90 seconds. If the determination at step  50  is no, the process continues to step  54  for the cooling fan to run for a third cooling down time, such as 60 seconds. In various embodiments, the projector operating time and associated fan operating time may vary depending on the rate at which the projector heats and cools. 
   Referring now to  FIG. 3 , a flow diagram depicts a process for cool down periods variably defined based upon measured projector temperature. The process begins at step  56  with a thermocouple or network of thermocouples measuring the temperature within the projector. At step  58 , the projector is powered off and, at step  60  a determination is made of whether the thermocouple-measured temperature is less than a predetermined cool down temperature. If not, the process continues to step  64  to run the cooling fan and periodically returns to step  60  to recheck the temperature. Once the temperature is less than the predetermined cool down temperature, the process continues to step  62  at which the cooling fan and projector are turned off. 
   Referring now to  FIG. 4 , a flow diagram depicts a process for selecting a convenience or a long-life cool down gradient. At step  66  a determination is made of whether a convenience or long-life cool down mode is selected. If a long-life cool down mode is selected the process continues to step  68  to run the cooling fan at a reduced speed associated with a cooling gradient that places reduced thermal stress on the projector lamp, such as with a temperature change over time within predetermined limitations. The reduced cooling fan speed and slower cool down rate results in increased cool down time for the projector and longer usable life for the lamp. If at step  66  the convenience cool down mode is selected, the process continues to step  70  to run the cooling fan at a maximal speed to achieve a rapid projector cool down for greater user convenience. The maximal speed is at the maximum effective fan speed, which may or may not be the maximum speed of the fan, in order to remove heat from the projector in a rapid manner. Once the cool down is complete at both steps  68  and  70 , the process continues to step  72  to detect the shut down temperature and to step  74  to shut down the cooling fan. 
   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.

Technology Classification (CPC): 5