White lighting from tunable LEDs can deliver “human-centric lighting” by illuminating our environment in such a way as to match the human circadian rhythm that evolved to adapt to the changes in the natural outdoor lighting cycle from sunrise to sunset. The correlated color temperature (CCT) metric measured in degrees Kelvin is generally used to describe the properties of artificial lamps based on our natural experiences of lighting. During sunrise and sunset, the CCT is below 2000 Kelvin and then it rises to between 3500-4500 Kelvin mid mornings and afternoons. Around noon, the CCT is generally between 5500K-6500K, which is referred to as daylight CCT. Various studies funded by the US Department of Energy (DOE) have shown that not only significant energy cost savings (>50%) can be achieved with variable CCT lighting from tunable LEDs but people tend to generally be healthier and perform better at homes, office buildings, and in schools when exposed to lighting with variable color temperature.
Unfortunately, traditional tunable LEDs are generally expensive. However, with the latest PhosphorTech innovation, they can now be achieved with proprietary down-converting structures without using expensive and complex electronic drivers, as typically is the case with most commercial products that employ multiple LED sources. Without multiple LEDs, a light source that can deliver color tuning between daylight and sunset/sunrise has always been considered not possible but novel phosphor-converted LED structures now enable a paradigm shift in variable high CRI white lighting over a wide range of color temperatures (CCTs). A single LED type combined with a spatially-variable phosphor system can deliver high CRI tunable LEDs over a wide range of color temperature without the need for complex drivers and multiple LED systems. Some examples are shown below.
High CRI Tunable White pcLED Source by Phosphor Down-conversion from a Single Near-UV LED
High CRI Tunable between Daylight to Warm White with NIR by Phosphor Down-conversion from a Single Near-UV LED