Study of Light Degradation in High Power LEDs as a Function of the Feeding Waveform

Abstract

This paper presents the analysis of the lifetime of a power LED based on its power waveforms. In this work, the luminous degradation of the LED is analyzed, based on the LM-80 and TM-21 Norm, comparing it with a curve fitting of the experimental data. The device under test consists of a 1W white LED, which operates for 6500 hours at a temperature of 85° C. The compared waveforms are the direct current and a rectified half-sine wave. The continuous wave presents minimal deterioration and its useful life corresponds to more than 50,000hrs. While the LED powered with a rectified sinusoidal half-wave presents a strong deterioration reducing its useful life to less than 7000 hrs., and showing a strong deterioration in its elements (silicone mold), in addition to losing its phosphor layer and emitting bluish light. The power waveform reduces the useful life of the LED since it affects its structure and its PN junction as shown in this article.