A Technique for Improving the Precision of the Direct Measurement of Junction Temperature in Power Light-Emitting Diodes.

Demetrio Iero,Giovanni Pangallo,Francesco G Della Corte,Gheorghe Brezeanu,Riccardo Carotenuto,Sandro Rao,Massimo Merenda

doi:10.3390/s21093113

Abstract

Extending the lifetime of power light-emitting diodes (LEDs) is achievable if proper control methods are implemented to reduce the side effects of an excessive junction temperature, TJ. The accuracy of state-of-the-art LED junction temperature monitoring techniques is negatively affected by several factors, such as the use of external sensors, calibration procedures, devices aging, and technological diversity among samples with the same part number. Here, a novel method is proposed, indeed based on the well-known technique consisting in tracking the LED forward voltage drop when a fixed forward current is imposed but exploiting the voltage variation with respect to room temperature. This method, which limits the effects of sample heterogeneity, is applied to a set of ten commercial devices. The method led to an effective reduction of the measurement error, which was below 1 °C.

Highlights

IntroductionDespite the efficiency and the long-term durability claimed by light-emitting diodes (LEDs) manufacturers, high power LEDs still suffer from excessive heating, which affects their luminous flux and operating lifetime [6,7,8,9]
Light-emitting diodes (LEDs) represent a highly efficient solid-state light source and in the last years, their use has been widespread over many market sectors, such as automotive, street lighting, architectural, and industrial, as well as commercial and residential lighting, and biomedical devices [1,2,3,4,5].Despite the efficiency and the long-term durability claimed by light-emitting diodes (LEDs) manufacturers, high power LEDs still suffer from excessive heating, which affects their luminous flux and operating lifetime [6,7,8,9]
The accuracy of state-of-the-art LED junction temperature monitoring techniques is negatively affected by several factors, such as the use of external sensors, calibration procedures, devices aging, and technological diversity among samples with the same part number

Summary

Introduction

Despite the efficiency and the long-term durability claimed by LED manufacturers, high power LEDs still suffer from excessive heating, which affects their luminous flux and operating lifetime [6,7,8,9]. In order to avoid unnecessary oversizing of dissipation systems, and keeping costs low while preserving the lamps’ health over time, it is essential to track the exact junction temperature (TJ) of LEDs. In order to avoid unnecessary oversizing of dissipation systems, and keeping costs low while preserving the lamps’ health over time, it is essential to track the exact junction temperature (TJ) of LEDs Coping with this problem, which is common to many high power density solid-state devices, would benefit from the deployment of device-integrated sensors, resulting in improved robustness and enriched functionality. Indirect measurement through a separate external sensor could lead to offsets, or substantial differences, in the tracked temperature values

Methods

Results

Discussion

Conclusion