The papers present a closed loop design concept for UV and non-UV devices and the resultant products that ensures success.
Monday, May 20, 2024 11:00am ,Jeff Hulett, Vektrex, presents a system and technique to characterize highly temperature sensitive UV-LEDs.
Tuesday, May 21, 2024 4:30pm Jeff Hulett, Vektrex discusses a technique to make measurements to confirm the product design.
11:00 am Monday May 20, 2024 Abstract
Navigating Temperature Sensitivity in UV-C LEDs for Enhanced Germicidal Effectiveness based on LM-92 Test Methods for Reliable Characterization
UV-C LEDs are highly temperature sensitive. A 10 C increase in operating temperature drops power output by 3 to 4%, and it shifts wavelength up, reducing germicidal efficacy. This unfortunate reality must be considered by GUV lighting designers when using and specifying LEDs, to ensure that product performance specifications will be met, and also to optimize their products to be commercially competitive.
Traditional LED test methods, based upon long test pulses that heat the LED, were adequate for general-illumination LEDs, but when used with UV-C LEDS, their measurement uncertainty can force designers to include an unacceptable design margin in order to guarantee the product will always meet specifications.
This paper discusses a new LED test method, based upon the IES LM-92 testing standard, that produces accurate measurements — correlated to temperature. A measurement system based upon this method is presented, along with example measurements that illustrate how designers can tailor measurements to produce cost-effective GUV designs.
4:30 pm Tuesday May 21, 2024 Abstract
Practical UV-LED In-Situ Temperature Measurement
Operating junction temperature is a critical parameter for UV LEDs, especially expensive UV-C LEDs. Product designers must ensure their LEDs are operating near the designed junction temperature. Otherwise the emitted power may be below or above the intended value.
Too little power and the product may not meet its specifications, too much and it is likely overdesigned and more expensive than it needs to be.
Junction temperature can be assessed using simple thermal resistance calculations, but this technique can be difficult to implement, especially in dense arrays, and the resulting temperature may be off by 10 degrees or more — enough to impact emitted power by several percent.
This paper discusses a technique for assessing junction temperature more accurately, in-situ, using the JEDEC Electrical Test Method (ETM). The equipment needed is presented, along with example calculations for a typical GUV product.
