Philips Lumileds has introduced the new Luxeon T series of high-power LEDs that target solid-state lighting (SSL) applications with directional-beam requirements including downlights, and MR16 and PAR retrofit lamps. The LEDs set new efficacy milestones for Lumileds achieving 140 lm/W at 350 mA of drive current. CEO Pierre Yves Lesaicherre touted the benefits of the new family, discussed Lumileds LED manufacturing technology, and commented on the development of the lime-green LED that was critical to the recent launch of the color-tunable Hue lamp by Philips lighting.
Lesaicherre emphasized that Lumileds considers the Luxeon T much more than an evolution of the Lumileds family saying, “The Luxeon T is going to be the workhorse in terms of high efficacy.” Clearly Lumileds expects Luxeon T to be the product of choice for applications in which the LED is expected to produce maximum forward light.
Lumileds claims several breakthroughs for the new series beyond efficacy, including what it says is an industry-lowest 2.7V forward voltage and 3°C/W thermal resistance. Product line director Kathleen Hartnett said that only one other LED maker has reached 2.8V and that most are at 3V or above. The lower forward voltage simplifies the thermal design – especially critical in space-constrained directional lamps such as MR16 retrofits.
Lumileds will offer the LEDs in 3-step MacAdam ellipse bins, tested at 85°C. Lesaicherre said that the company is not matching phosphor tiles with emitters the way it did in the original Rebel Lumiramic-based LEDs to reach the tight binning, but instead controlling the epitaxial (epi) process more tightly.
Indeed, better process control is behind both the binning and the lower forward voltage. Lesaicherre said, “The conversion to 6-in substrates has really helped because we have more modern equipment.” Specifically, he said they have tighter control of temperature and gas distribution in the epi process.
“We change our epi recipe every six months on average,” said Lesaicherre. The Luxeon T is made with the latest recipe. Moreover, the company developed chip-architectural and packaging enhancements to maximize light output and efficacy.
The new family utilizes a chip-in-frame package with a tightly coupled optical dome. The combination of a small 2-mm2 emitting surface and properly sized dome is critical in directional applications. For more detail on that topic, see our recent article, “Design considerations for enhancing LED efficiency.”
The LED package measures 3.7×3.7 mm. The prior Luxeon A product targeted similar applications but features a rectangular pattern. Hartnett said the package design minimizes the footprint and allows the LEDs to be packed more closely together. The company has used the same package in the multi-emitter Luxeon M family.
The new LEDs offer a minimum CRI of 80, and optionally a CRI of 95, across the full range of CCTs, including 2700K, 3000K, 3500K, 4000K, and 5000K. With the high minimum, the LEDs will primarily find use in indoor lighting. Expect a complementary product with a lower CRI for outdoor applications down the road. www.ledtubes8.com