A noncontact method for determining junction temperature of phosphor-converted white LEDs

Yimin Gu; Nadarajah Narendran

doi:10.1117/12.509751

26 January 2004 A noncontact method for determining junction temperature of phosphor-converted white LEDs

Yimin Gu, Nadarajah Narendran

Proceedings Volume 5187, Third International Conference on Solid State Lighting; (2004) https://doi.org/10.1117/12.509751
Event: Optical Science and Technology, SPIE's 48th Annual Meeting, 2003, San Diego, California, United States

Abstract

The goal of this study was to develop a non-contact method for determining the junction temperature of phosphor-converted white LEDs as a first step toward determining the useful life of systems using white LEDs. System manufacturers generally quote the same life values for their lighting systems that the LED manufacturers estimate for a single LED. However, the life of an LED system can be much different compared with the life of an LED tested under ideal conditions because system packaging can affect system life. Heat at the pn-junction is one of the key factors that affect the degradation rate, and thus the useful life, of GaN-based white LEDs. The non-contact method described in this manuscript, combined with LED degradation rates, can be used to predict white-LED system life without affecting the integrity of the lighting system or submitting it to long-term life tests that are time-consuming. Different types of LED packages would have different degradation mechanisms. Therefore, as a first step this study considered only the 5mm epoxy encapsulated GaN+YAG Cerium phosphor white LED. The method investigated here explored whether the spectral power distribution (SPD) of the white LED could provide the necessary information to estimate LED junction temperature. Based on past studies that have shown that heat affects the radiant energy emitted by the InGaN blue LED and the YAG Cerium phosphor differently, the authors hypothesized that the ratio of the total radiant energy (W) to the radiant energy within the blue emission (B) would be proportional to the junction temperature. Experiments conducted in this study verified this hypothesis and showed that the junction temperature can be measured non-invasively through spectral measurements.

Citation Download Citation

Yimin Gu and Nadarajah Narendran "A noncontact method for determining junction temperature of phosphor-converted white LEDs", Proc. SPIE 5187, Third International Conference on Solid State Lighting, (26 January 2004); https://doi.org/10.1117/12.509751

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