Published on:
February 12, 2014
Cree has announced the CXA1310, CXA1850, and
CXA2590 chip-on-board (COB) LEDs with light-emitting surface (LES)
diameters of 6, 12, and 19 mm. respectively. The products are part of
Cree's COB offering that the company terms high density and are designed
to maximize the candela (cd) per dollar for directional applications,
as opposed to the standard-density products that are focused on maximum
lumens per dollar.
Cree first announced the high-density concept back in September of 2013
with the 9-mm CXA1520 that offered double the output of the prior Cree
LEDs in the same size. The new products extend lumen output to beyond
13,500 lm at 5000K CCT and to 11,500 lm at 3000K CCT. The 6-mm CXA1310,
meanwhile, delivers flux in the 2000-lm range. Cree says that the
performance is industry best relative to the LES sizes, and a smaller
LES enables simpler, lower-cost control of the beam with smaller optical
elements such as reflectors.
The LEDs are available across the range of 2700K to 6500K CCT. Cree
offers 80-CRI products across the board, 70-CRI products at the cool end
of the spectrum, and 95-CRI products at the warm end of the spectrum.
With the new product launch, Cree also stressed a new way to consider
LED performance, and the match of LEDs to an application, called
optical control factor (OCF). Essentially the metric comes down to
performance divided by surface area of the emitter, whether the LED or
LEDs under consideration are in COB array or discrete form.
Paul Scheidt, product marketing manager for LED components at Cree,
discussed applications and LEDs relative to OCF. He said applications
such as linear troffers can benefit from mid-power LEDs that have low
OCF that is a match for the broad beam spread, diffuse light
requirements of the application. He said Cree's mainstream CXA family is
also a good match to other applications with diffuse light requirements
such as BR lamps and downlights.
The high-density COB LEDs are targeted at high OCF applications
including directional lighting ranging from PAR/MR LED replacement lamps
to tracklights to even low- and high-bay fixtures that need to focus
the beam. Primarily, the LEDs target applications that require maximum
center beam candle power and enable system performance legacy sources
can't serve.
"Never before have we been able to harness such a large amount of
light in such a small package, which can help us improve our lighting
designs and address a number of applications that we previously could
not, " said Mike Wang, vice president of lighting engineering at Edison
Price Lighting. "The beauty of these new high-density LED arrays from
Cree is that they are helping us bring products to the market that
currently don't exist."
Product prototype comparison
To illustrate the advantages of the new products, Cree has assembled
some prototype light engines to which it compared existing lighting
fixtures and lamps based on legacy sources. For example, Cree has
demonstrated a CXA1310-based engine that delivers 31,000-cd CBCP and a
9° beam at 15.4W. Scheidt compared that product to a typical track
fixture that uses a 44W Philips PAR20 ceramic metal-halide (CMH lamp)
that delivers 13,220-cd CBCP and a 10° beam.
In fairness, the Philips CMH lamp is 86 CRI and the Cree prototype is
82 CRI. But the performance advantage of the LED option is clear.
Scheidt said that a quality track fixture sells for $200 in high volume
and the lamp for around $20 with those prices doubled if bought in
individual quantity. He said that the bill of materials for the LED
light engine was in the $34 range in high volume including LED, driver,
heat sink, and optic. Of course, the track fixture includes a ballast
and that component is equivalent to the driver in the LED light engine.
But the point is that a track luminaire can easily accommodate the cost
of the LED light engine and deliver superior performance.
The comparison ignores the fact that the LED light engine would still
need to be accommodated in a fixture, but still shows the value
proposition of the higher-performing and more-efficient LEDs.
Scheidt also stressed that the LED implementation delivers
performance that is simply unavailable in legacy sources. He said that
the very best PAR20 CMH lamps top out at 2000-cd CBCP. Yet the LED
prototype offers more than 50% additional performance even though the
actual lumen output of the CMH lamp is greater.
Another prototype LED engine in Cree's portfolio is based on the
21-mm CXA1850. Scheidt compared a 3000K, 55,620-cd CBCP, 38W LED product
with a typical track fixture equipped with a Philips 74W, 50,559-cd
CBCP CMH lamp. The Cree prototype used an off-the-shelf Nata optic that
Cree had on hand to deliver a 15° beam whereas the Philips lamp
delivered a tighter 10° beam. At first glance it would appear that the
CMH product is higher performing given the narrower beam. But Scheidt
pointed out that the LED engine would have even a higher CBCP spec if
equipped with a reflector that narrows the beam. The largest CXA2590
LED, meanwhile, can deliver the equivalent CBCP of a 150W CMH source at
almost half the power.
"The high-density LED arrays from Cree are extremely impressive,"
said Kenny Eidsvold, president of Intense Lighting. "We are looking
forward to using these products in applications requiring very high
center beam candle power that previously could not be achieved with
LED-based solutions."
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