Uncertainty analysis in lifetime measurement for white light emitting diodes

Abstract

Lifetime is one of the most important characteristics of white LEDs for the solid state lighting industry and end users. The measurement uncertainties should be controlled well to ensure consistent measurement results. This paper gives uncertainty analysis in the measurement for the L50 lifetime of white LEDs. The exponential model is assumed for LEDs’ light output degradation, and an Eyring model is used for accelerated life test. The influences of photometric measurement instruments, measurement duration and interval, junction temperature, input current, current accelerating index and activation energy are analysed. The analysis method introduced in this paper can be referenced for other related analysis, and the results are important to the practices in LED lifetime measurement.