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Recognize high-power LED thermal problems

Posted: 17 Sep 2007 ?? ?Print Version ?Bookmark and Share

Keywords:high-power LED system? thermal impedance? color sensor?

Unlike incandescent tungsten light bulbs, high-power LEDs do not radiate heat. Instead, LEDs conduct heat from their PN junction to the thermal slug on the LED package. Because the heat generated by LEDs is conducted, the heat has a longer, more expensive path to the atmosphere. In an LED, the heat path includes the thermal impedances from the junction to the slug, the slug to the board, the board to the heat sink and the heat sink to the atmosphere. The heat path for a tungsten bulb is almost straight into the atmosphere, starting with the thermal resistance from the filament to the glass and ending with the thermal resistance from the glass to the atmosphere.

Longer lifetime, higher efficiency and more flexible color output make LEDs the preeminent solution in architectural and entertainment lighting applications. The color output of LEDs is programmable--that is, a system of multiple LEDs combines or mixes to create different colors. One application of color mixing with LEDs is LCD backlighting. In this application, multicolor LEDs are used to create a white light with a color temperature of 6,500K.

Designers attempting to create high-power LED systems are well served by understanding the thermal problems associated with LEDs. Smart thermal management will increase the operating temperature range, and thermal monitoring will maintain the accuracy of LED products.

Please view the PDF document for more information.

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