Everyone seems to agree that LED-based MR16 lamps are tough to design and manufacture given the space-constrained form factor, but there is little agreement as to the best approach for such solid-state lighting (SSL) products. Cree authored a feature article in our recently released October issue on MR16 lamp design, presenting actual reference designs. Soraa has taken issue with some of the Cree statements about gallium-nitride-on-gallium-nitride (GaN-on-GaN) LEDs and the company CTO Mike Krames has addressed the article in a blog post.
Soraa's LEDs are different in many ways from other manufacturers' products, starting with the fact that homogenous substrate and active semiconductor layers have fewer defects and thus can deliver more light output. But Soraa also uses a violet LED chemistry and a mix of more phosphor types to deliver high-CRI performance at warm CCTs.
Cree wrote that a violet emitter in an MR16 design could result in significant UV energy radiated from the lamp. Such radiation can be harmful, especially when used to illuminate valuable artwork. Soraa's Krames, however, said that less than 0.1% of the emission of its LEDs is below 400nm.
The Cree article also questioned the longevity of a design in which the LEDs can be driven at a higher power density, because related heat could cause color shift unrelated to the actual LED component. Soraa's statement that its MR16 lamps being rated for 25,000 hours in an enclosed fixture presumably addresses the issue of reliability and longevity.
The debate is likely to continue as LED makers seek to enable what could be a very lucrative market with MR16 lamps being among the most widely used in the US and abroad. Indeed, Soraa will contribute an article for a future issue of the magazine that addresses all angles of MR16 design including the LED, electronics, and optics.
