Evaluation Model for LED Lighting Device Service Life in Terms of System Operating Conditions

This paper presents the concept of a multi-level model for service life predicting of lighting devices based on semiconductor light sources, with respect to systemic operational factors and the degradation of the associated components. Unlike standard assessment methods limited to analyzing the reduction the light-emitting diode luminous flux, the proposed approach also considers shifts in chromaticity coordinates, light emission flicker levels, and the failure resistance of the power supply unit. The model is grounded in physically justified laws and includes the degradation evaluation in the crystal structure, photoluminescent materials, optical elements, and life-limiting components of the power unit. Transition from accelerated testing to actual operating conditions using reference time, calculated on thermal, electrical, humidity, and ultraviolet exposure level basis is the key element. The integral reliability function is generated by considering partial failure criteria, allowing statistical dependencies between degradation mechanisms to be taken into account. The model is validated by experimental data obtained from various stress conditions runoff. Numerical modeling results, confirming the validity of the methodology for aligning degradation patterns and acceleration factors, are provided. The proposed approach ensures both result reproducibility for serial quality control purposes and applicability in estimating expected warranty-related costs. The developed modeling concept can be integrated into quality management practices in lighting device manufacturing to enhance service life prediction accuracy and identify structurally vulnerable components at the design stage.