Conditions for thermally stable color characteristics of trichromatic white light-emitting diodes

We present a method to stabilize color characteristics from a trichromatic white light-emitting diode (LED) consisting of red, green, and blue (RGB) LEDs under varying ambient temperatures. Through colorimetric analyses, it was found that the trichromatic white LED could maintain its chromaticity coordinate by adjusting the light output power (LOP) of green and red LEDs as the temperature varied. Moreover, the correlated color temperature (CCT) could be invariant to the external temperature change by controlling only the LOP of a red LED. Using the developed mathematical model and temperature-dependent spectral data of commercial RGB LED samples, we determined the power ratios between RGB LEDs needed to achieve thermally stable color coordinates or CCT as the heat sink temperature varied from 20 to 100 degrees C. When operating under thermally stable CCT conditions, the chromaticity coordinate of the trichromatic LED moved along the iso-CCT line with only a minor color deviation as the temperature increased to 100 degrees C. The presented approach requires adjusting the power of only one LED to achieve thermally stable CCT operation in a trichromatic white LED, which is expected to simplify LED control circuits significantly. (c) 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement