Managing heat in power LED systems for optimal performance

April 27, 2009
When designing a solid-state solution with power LEDs, one cannot underestimate the importance of the thermal system design, as encapsulated in the phrase “Think Thermal First”. Rudi Hechfellner explains.
To understand the role of thermal design in LEDs, it’s important to review how system and electronic drive conditions influence light output performance and long term behavior of high-power LEDs. The parameters are all influenced by the junction temperature of the LEDs, demonstrating the importance of this subject.

Temperature has a direct impact on optical and electrical performance as well as on the overall quality and reliability of an LED-based product. Therefore, it is critical that engineering teams understand the system’s thermal parameters, and focus on thermodynamic competencies.

These parameters are all interconnected. For example, a higher drive current should increase the light output of the LED. However, the higher current increases the dissipated power, causing heating within the LED, which has a negative impact on light output. Also, conversely, a higher junction temperature (caused for example by a higher ambient temperature) causes a reduction in the LED’s forward voltage, reducing the dissipated power for a constant-current source.


This article was published in the April 2009 issue of LEDs Magazine.

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