Developing highly reliable LED luminaires for high temperature applications using AC-direct driving LED technology

The paper is to develop highly reliable LED luminaires for high-temperature applications, which are often needed in hush or hazardous industrial environments. An improved MIL-HDBK-217F method is introduced to study the reliability and predict the lifetime of different LED driving technologies, and confirmed by accelerated life testing results in order to optimize the design towards high reliability and long lifetime. Based on the analysis results of a AC-direct driving LED driver and a switched-mode LED driver, the paper demonstrates that the AC-direct driving technology is a better driving solution for LED luminaires used in high-temperature environments due to its capability to operate at higher temperatures and longer lifetime at the same temperature compared to the traditional switched-mode driving technology. Also, the paper has some discussions on optimizing the design of the AC-direct driving circuits for long lifetime in high temperature applications. As a result, a 4000+ lumen AC-direct driving LED luminaire is developed, which has achieved 2-3 times longer lifetime at 65 °C ambient and can operate safely up to 80 °C ambient (15 °C higher) compared to its switched-mode counterpart.