Accelerated Degradation Test Investigation for Life-Time Performance Analysis of LED Luminaires

Abstract

LED luminaires are a common lighting source used in general lighting application as they are energy-efficient and long-lasting. However, the reliability of an LED luminaire is not well established, and no standard method for estimating the performance of an LED luminaire is developed. This article presents an investigation to understand the performance of LED luminaires at the accelerated degradation test (ADT) condition and analyzes the reliability of LED luminaires. An LED luminaire has two subsystems, an LED light engine and the LED constant current driver that are subjected to ADT, and the light engine factors, lumen output, and Duv changes are analyzed. Similarly, the driver output stage electrolytic capacitor capacitance and equivalent series resistance (ESR) are estimated. The study of continuous operation in time and study when subjected to switching cycles to quantify reliability in terms of operating cycles is performed. All four key parameters-lumen maintenance, Duv, capacitance, and ESR-are estimated up to their specified threshold and reliability is analyzed. The LED light engine lumen output is found to degrade very quickly compared with other factors. LED luminaire failure at ADT is mainly due to lumen depreciation followed by color shift and, after significant intervals of time and cycles, the driver capacitor ESR follows as reason for the failure of the LED luminaire. A scanning electron microscope (SEM) energy dispersive spectroscopy (EDS) analysis is performed on the LED package, and results show that LED silver (Ag) mirror tarnish is the main reason for a significant reduction in light output.