Electrical and Thermal Effects of Tunable LED Systems on Lighting and Non-Visual Biological Characteristics

The color, electrical, optical and thermal properties of light-emitting diode (LED) systems are highly dependent on one another. This paper proposes an analysis model that links the optical power, correlated color temperature (CCT), and circadian action factor (CAF) together with the electrical and thermal effects of phosphor-converted LEDs. The proposed model applies to tunable white LED systems with various color temperatures of LEDs whose spectral power distribution (SPD) can be individually controlled. The total optical power is due to the combined emitted optical power of both LEDs, the overall CCT is built upon a non-linear empirical LED model, and the overall CAF is quantified based on an extended Gaussian SPD model. The proposed prediction model consists a series of optical and chromatic evaluation, with which it is simple for LED system designers to comply. In model verification, the bi-color white LED source made up of a warm color LED (2700 K) and a cool color LED (7600 K) is adopted, with good agreement between the calculated and experimental results.