A Critical Advance in MR16 LED Lamps

James R Benya, PE, FIES, FIALD

ABSTRACT

The Holy Grail of lighting is a man-made light source that has superior energy efficiency, long life, good lumen maintenance, wide temperature starting and operating range, instant starting without life degradation, full range dimming, excellent color, low- to-moderate cost, and is capable of being a "point source". All conventional lamps fail substantially in one or more of these fundamental criteria.

As it has evolved, solid-state lighting (SSL or LED) has succeeded in meeting many of these criteria. Various current products demonstrate energy efficiency, long life, good lumen maintenance, wide temperature range, instant starting, and full range dimming. Most recently, superior color has also been achieved. However, while individual LED sources are reasonably close to a point source, they have low lumen density per point, forcing current lamp engineers to use multiple point sources to create a highly directional lamp. The multiple sources create multiple shadows and in some cases colored shadows that are considered undesirable in display applications.

The recent commercialization of GaN on GaN technology is a significant breakthrough in energy density, allowing 5-10 times more lumens to be generated per unit volume. The primary benefit is smaller LED array size, which in turn reduces the size of directional lamps and results in point source-like behavior. Another important benefit is greater heat tolerance, enabling the dense lumen package to operate more readily in a compact package.

A commercial product using GaN on GaN technology has been developed as a family of MR16, 12 volt AC lamps. Depending on the version, the lamp family's performance approaches that of generic MR16 halogen lamps and is comparable to, although at present slightly less than, premium standard or IR halogen lamps . The products include integral drivers that operate well on a number of combinations of transformers and dimmers, which are delineated in product literature. Common applications include track and recessed lighting (provided that the normal glass lens is removed) and one version is specifically for enclosed luminaires such as used in landscape lighting.

Lamp color rendering is available in standard and high CRI versions. The standard version is offered at either 2700K or 3000K and 80 CRI . The high CRI version is offered at either 2700K or 3000K and 95 CRI. To achieve high color rendering with deep red (R9>90), this product employs "violet pumped" triphosphor, achieving a closer match to the blackbody than conventional two phosphor "blue pumped" LED. As a side effect, the lamps' violet emission around 410 nm reacts with optical brightening agents to have a unique whitening effect for display uses.

The resulting product appears to be a significant leap in LED technology for the huge worldwide MR marketplace, with performance that, within practical wattage and lumen limits, rivals the best LED light engines with remote drivers.