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XLamp a19 RefeRence Design

trademarks of Cree, Inc. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please contact Cree Sales at sales@cree.com.

is dissipated through conduction, must have a separate path and heat sink for thermal dissipation. Hence the design

constraints that come with replacement lamps.

a great deal of interest and activity has centered on the e26/a19 form factor and there are many ways to approach the

design and production of the classic a19 bulb. This application note reviews a variety of leD choices available from cree

to achieve attractive and cost effective warm white a19 bulbs or replacement lamps. This application note is different

from other cree application notes in that it reviews a spectrum of design choices rather than focusing on a particular

implementation.

while most cree reference designs or application notes use a 6-step framework, described in the “leD luminaire Design

a19 leD replacement lamps. as such we only visit a few of the steps in the framework.

A19 Lighting RequiRements

The most common form of a19 leD replacement lamps are often referred to as “snow cones.” This moniker comes

from the hemispheric dome that covers a circuit board of leDs that sit atop a conic heat sink, which gives the visual

impression of an ice cream cone or snow cone. The benefits of this approach come from a relatively large set of suppliers,

delivering form-factor appropriate heat sinks, device drivers and molded diffusers. as such, this style of a19 bulb has

rapidly become the dominant value-priced bulb. For many lighting applications the hemispheric distribution of luminous

flux that comes along with the snow cone approach is sufficient – a very wide-angle flood lamp. But for applications that

In order to achieve an omnidirectional flux distribution, other approaches to flux geometry must be used. Noteworthy

or innovative examples of these designs include bulbs from GE, Philips and LSG, shown below.

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LED Luminaire Design Guide, Application Note AP15, www.cree.com/xlamp_app_notes/luminaire_design_guide. The guide

advocates a 6-step approach consisting of:

1.

Define lighting requirements

2.

Define lighting goals

3.

Estimate efficiencies of optical, thermal and electrical systems

4.

calculate the number of leDs needed

5.

consider all the design possibilities and choose the best

6.

Complete the final steps

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The US Environmental Protection Agency defines the omnidirectional requirements in ENERGY STAR® Program Requirements

for Integral LED Lamps, www.energystar.gov/ia/partners/product_specs/program_reqs/ILL_prog_reqs.pdf. Table 4, p3, applies to

all lamps; Table 6, p9, applies to “Non-Standard” Lamps – snow cone bulbs fall into this category, and Table 7A, p10, applies to

omnidirectional lamps.