LED lighting products offer many benefits compared to conventional lighting products, including increased energy savings, longer lifetimes, and a greater ability to adjust the spectral output. Spectral adjustment is desirable in settings where multiple lighting spectra are required, such as hospitals, offices, nursing homes, classrooms, and greenhouses. Although LED light sources with fixed spectral output can work well in some of these settings, greater control over the spectral content is often gained by using multi-source LED products. However, the reliability of multi-source LED products is not well understood. Since there are complex architectures found in these products (see figure below), there are greater challenges to assess reliability.
To provide information and analysis to the lighting industry, the U.S. Department of Energy released a new report – Accelerated Stress Testing of Multi-Source LED Products: Round 2 – which focuses on determining the mechanisms of optical change in multi-source LED products that use different types of mid-power LEDs integrated into the same LED module. The report focuses on a white-tunable lighting product that underwent accelerated stress testing for up to 20,000 hours, and two horticultural lamps that underwent accelerated stress testing for up to 8,000 hours. The testing data provide detailed information about the products and the materials used in the products, which greatly extends the impacts of the research.
The first report (Round 1) in this series provided initial results of accelerated stress testing (which was conducted at either high temperature or high temperature and humidity) for the products studied in this current report. Future reports will benchmark advancements from other devices.
The new findings show that the aging properties of multi-source LED lighting products can vary widely depending on their architecture, and that these differences can have significant impacts on the quality of light, including changes in the luminous flux levels, chromaticity, and tuning range. Consequently, careful consideration must be given to potential aging differences in the LED primaries and their long-term impacts on all components of a solid-state lighting device. The impacts of using multiple LED sources must be approached at the system level. The three main system components (i.e., LED packages; device optics, including secondary lenses, reflectors, and housings; and device electronics and controls) impact the long-term performance and reliability of the multi-source LED device to varying degrees.
Understanding these impacts is critical to developing multi-source LED products with the lifetime and reliability needed to meet future lighting application needs.
Download the full report.