Influence of the injection current on the degradation of white high- brightness light emitting diodes

摘要

Since high-power LEDs show great potential in reducing energy consumption worldwide, a great deal of research has been performed to understand their degradation rate. As reported in many publications, temperature is of critical importance so lifetests are mainly based on the internal temperature of the junction (T_j). A common testing method is to overdrive the LED with high current in order to cause self-heating. However, by doing so, it is assumed that current does not produce self-degradation. This topic is of great importance nowadays because of the recent development of LEDs used to increase operating current. We have conducted a lifetest on LEDs to isolate the influence of current by using a thermally-controlled heatsink to keep the same T_j for different driving currents. This paper presents the experimental setup with the associated protocol used in the experiment. We also present preliminary results obtained from two high-power white LEDs. These were stressed at currents ranging from 350 mA to 1000 mA and at temperatures ranging from 75℃ to 150℃. To our knowledge, this type of measurement has not been reported in the literature. In the future, we would like to use a Weibull statistical model to study the combined effects of temperature and current on the degradation of LEDs.