A good alternative is active cooling, introducing a fan into the system to generate airflow around the chassis and the heat-generating components, efficiently removing heat from the system. However, these have proved insufficient in many popular consumer electronics products-and they are also somewhat expensive. The quietest way to remove heat is with passive components such as heat sinks and heat pipes. This heat needs to be removed quietly and efficiently. What these systems all have in common, besides significantly smaller-and still decreasing-size, is that the amount of heat they must dissipate does not decrease often it increases! In the notebook PC, much of the heat is generated by the processor in the projector, most of the heat is generated by the light source. Other examples of this trend include projection systems and set-top boxes. Thin and “Lite,” notebook PCs have shrunk significantly, yet their processing power has been maintained or increased. Consequently, lots of electronic components are being shoehorned into very small form factors. The trend in electronics, particularly consumer electronics, is towards smaller products with enhanced combinations of features. This article will describe how and why this evolution has taken place and will suggest some useful approaches for the designer. However, in recent years, the technology of using these fans has evolved significantly. Compact electrical fans are cheap and have been used for cooling electronic equipment for more than half a century. Interest has been growing in integrated circuits for controlling the speed of cooling fans in personal computers and other electronic equipment. Why and How to Control Fan Speed for Cooling Electronic Equipment

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