Performance Characterization and Theoretical Modeling of Emitted Optical Power for High-Power White-LED Devices

In this paper, optical power of high-power white-light-emitting diode (LED) devices is evaluated and characterized. A theoretical model for optical power is proposed. The measurements reveal that optical power decreases exponentially with junction temperature and increases linearly with current. The model considers conjunct effect of current and junction temperature on emitted optical power. The proposed theoretical model of optical power will facilitate the optical and thermal performance evaluation of LED devices and will be helpful to device design. With the presented optical power model, heat power can be estimated, because they are complementary to each other. Then, junction temperature of LED device can be predicted with known heat power. In addition, the optical power model can be applied to eliminate chromaticity shift phenomenon of trichromatic-based white-LED devices, simply by monitoring junction temperature and injection current of each chip. Validity of the optical power model has been verified by experimental measurements on two types of commercial LED devices.