Project Lighting - April 2008 - (Page 14)

FeAtURe reduce spreading resistance. When high power LED packages are mounted on metal-core (MC) or ceramic PCBs, a specially designed luminaire is need to facilitate heat dissipation. Integral heat sinks (see Figure 1) improve heat dissipation, and fans can be added if needed. FIg 1 leDS are mounteD on a fiXture With an integral, finneD heat Sink. The value of this approach can best be illustrated using an example. Consider a spotlight used for down-lighting, with white HBLEDs mounted on an MCPCB consisting of a thermally conductive, laminated board with an aluminum base (see Figure 2). The PCB is mounted on a radial heat sink using a thermally conductive, doublesided adhesive tape. This spotlight application features four 1-W LEDs, each with a junction-to-case thermal resistance of 15 K/W. On the rear of each LED, an aluminum heat slug is used to conduct heat from the junction to the external world. The slug is connected to the board using a thermally conductive compound, in this case thermal glue whose thermal resistance is specified as 4.3 K/W. For successful cooling, the thermal resistance of the PCB Contents Viewpoint Selecting HBLED Drivers for Lighting Apps Simulation Technique for Optimizing White-LED Design An Analytical Approach to Cooling HBLEDs Lighting News Alternatively, flexible thermal circuits provide heat-spreading properties for mounted HBLEDs. Flex circuits can be installed on curved surfaces, such as along hand rails or walkways, where FR4, MCPCBs, and other rigid materials can’t be used. an anaLyticaL approach Home Page Product Training Module Online Ordering Suppliers Catalog FIg 2 for the leD-BaSeD SPotlight at left, an ir image (right) ShoWS thermal ProPertieS. Developing a thermalmanagement design for high power LEDs is more effective if three steps are taken: 1. Integral analysis 2. Computational analysis 3. Experimental verification 14 | Project lighting | aPr 08 http://digikey.com/ http://ad.doubleclick.net/clk;198717884;26055153;t http://ad.doubleclick.net/clk;198717989;26055167;e http://ad.doubleclick.net/clk;198717988;26055168;e http://ad.doubleclick.net/clk;198717986;26055170;v http://ad.doubleclick.net/clk;198717985;26055171;v

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Project Lighting - April 2008 Contents Viewpoint About Project Lighting Sponsor Simulation Technique for Optimizing White-LED Design An Analytical Approach to Cooling HBLEDs LED Lighting Needs Smarts to be Competitive Lighting News Enter to Win an iPhone Refernce Materials Lighting Quick Links

Project Lighting - April 2008

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