Dynamic thermal simulation of high brightness LEDs with unsteady driver power output

High Brightness Light Emit Diodes (HB LEDs) have attract much attention recently with its high efficiency. However, they are known to be prone to high temperature and high thermo-mechanical induced failure. Since 80% of their input energy is loss as heat, this will heat up the junction temperate to more than 100°C due to joule heating. Furthermore, LED is not designed for AC power input and a driver is needed for LED lamp to convert the AC power from mains to DC power. However, DC supply from the driver is known to fluctuate and this will cause the temperature of the LED to vary and this in turn induced unstable thermal stress. In this work, a simplified thermal pulse is used to mimic this situation. Three situations are simulated: (1) stable heat generation, (2) heat generation with single disturbances, (3) heat generation with multiple disturbances with different frequencies. Results show that driver current fluctuations may result in significant thermal changes and associated mechanical stresses.