LED's luminous flux lifetime prediction using a hybrid numerical approach

Light-emitting diodes (LEDs) have several advantages over traditional incandescent bulbs and compact fluorescent lamps, such as superior energy efficiency, environmental friendliness, and particularly long lifetime (between 25,000 to 100,000 hours). However, this long lifetime of LED proves inconvenient to manufacturers for conducting reliability tests which require the same amount of time to conclude. To overcome such inconvenience, this paper presents a hybrid numerical approach that combines numerical modeling with analytical analysis to predict the lifetime of LEDs. In this paper, a 60W-equivalent 10W phosphor-converted white LED bulb is studied by two numerical approaches. A one-dimensional (1-D) thermal-resistance circuit analysis and a three-dimensional (3-D) hybrid finite element analysis (FEA) are employed to estimate the LEDs' junction temperature in accord to the data obtained through the experiment. The numerical results showed that both 1-D thermal-resistance circuit and the hybrid FEA model are in agreement with the experiment data, thus invaluable to manufacturers who need to carry out reliability testing. Then the estimated junction temperature is used to determine the LED luminaire's lifetime according to the known LM-80 database and TM-21 method.