Cree has introduced the XLamp XH-G and XH-B mid-power LEDs that are packaged on a ceramic base whereas most mid-power LEDs come in a plastic package. Cree says that ceramic ensures long life in solid-state lighting (SSL) designs even when the LEDs are operated at elevated temperatures, and the new devices deliver efficacy as high as 170 lm/W at a typical 65-mA drive current.
The new XH-family LEDs come in a 3×3-mm package with a relatively shallow domed optic. In contrast, plastic mid-power LEDs have a flat emitting surface. Cree product marketing manager Paul Scheidt said the LED architecture delivers a 130° beam pattern, whereas most plastic mid-power LEDs are in the 115° range.
The broader beam pattern and the potential for more flux output will make the XH a superior choice for applications such as linear troffers, according to Scheidt. At 65-mA binning current, the XH-B outputs 24.5–26.9 lm over the 3000K–4000K CCT range, and the XH-G delivers 26.6–29.7 lm over the same range. Unlike most mid-power LEDs, the XH can be driven beyond the mid-power range with the XH-G going to 1W.
Still, the most significant advantage of the ceramic-based design may be lifetime. Scheidt said that leading plastic mid-power devices can deliver 50,000-hr lifetimes below 75°C operating temperatures, but the TM-21 projected life falls rapidly at higher temperatures. As an example, Scheidt said lifetime for plastic LEDs can be less than 20,000 hrs when operated at 95°C.
Higher-temperature operation
The temperature advantage can play out in two different ways, according to Scheidt. SSL product developers may have to add more expensive thermal management components in a design with plastic packages. Or the developer may have to use more LEDs at lower drive currents to limit the temperature. The XH offers the option of higher-drive currents and long life with less complex thermal management.
"We're excited that Cree is offering high-quality, ceramic-based mid-power LEDs designed for real-world lighting applications," said Roger Suen, supply chain management director at Light Engine. "The XH LED family gives us confidence in providing products that deliver stable lumen maintenance and good color consistency that cannot be duplicated by plastic packages."
The XH family marks Cree's second foray into the mid-power space with ceramic-based LEDs. Back in April Cree announced the XQ family that is even smaller than the XH, but higher in performance. The XQ is built on Cree's third-generation silicon-carbide technology platform that the company calls SC3. Those XQ devices are actually very-small high-power LEDs.
The XH is manufactured using a cost-optimized technology base, although Cree wouldn't discuss the differences in the device structures. Scheidt said that the more complex optics on the XQ can deliver a 140° beam pattern. Basically the XH LEDs are intended as a one-for-one replacement of plastic mid-power LEDs, while the XQ family enables designs that use fewer LEDs.
Cree created a reference design to demonstrate the capabilities of the new LEDs at the system level. The company used 64 XH-G LEDs on a 1×1-ft panel for an application such as a ceiling troffer. With 350 mA of current driving the entire panel, the design delivers 1587 lm at an efficacy of 159 lm/W. Click on the nearby table for the full system specs and options for operating the design at higher currents.
