Arroyo Instruments has completed a National Institute of Standards and Technology (NIST) Phase 1 Small Business Innovation Research program for the development of a pulse/DC characterization system for LEDs. The goal of this project, successfully met by the completion of a prototype device, was to develop a commercially viable solution to determine and maintain accurate LED junction temperature during characterization.

Development of LEDs for various applications, such as vehicle lighting, signage, and commercial and residential solid state lighting is progressing at a rapid pace. Various methods exist to measure the performance of LEDs, but variations in test configurations, thermal management, test and measurement equipment, and operator experience lead to significant variations in measured performance.

In particular, thermal management of the LED has a significant impact on LED performance. Various methods exist which attempt to minimize the impact of temperature change during characterization, including costly pulse measurement systems, which also suffer from low signal-to-noise ratios, or elaborate heat sinking solutions to minimize the junction-to-case temperature delta.

A new solution was proposed that allows for accurate junction temperature determination while still allowing the LED to operate in a continuous power (CW) mode, and can be used with virtually any mounting system. The subject is well defined by Yuqin Zong and Yoshi Ohno in "New Practical Method for Measurement of High Power LEDs." In their paper, the proposed method significantly eliminates errors caused by thermal management variations by choosing a characteristic of the LED performance, the forward voltage, as a key indicator of junction temperature at a given current.

The commercial potential of this process is significant, as it could ultimately reach into every LED R&D, test, and manufacturing facility. Because it eliminates variations in LED temperature, a critical metric in LED performance, this method has the potential to significantly change the way LED specifications are developed. In addition, a peer-reviewed, integrated system will significantly speed the adoption of this test method.

With the delivery of the Phase 1 prototype to NIST for evaluation and feedback, Arroyo Instruments is looking forward to the prospect of commercializing the prototype through a Phase 2 proposal that has since been submitted to the NIST SBIR program. NIST, as part of the U.S. Department of Commerce, promotes technology innovation through these SBIR programs, and Arroyo Instruments welcomes its opportunity to be a part of it.