5

XLamp CXa2520 LED

6-inCh DownLight

REfEREnCE DEsign

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.

Characteristic

Requirements

Noise requirements: directional

and non-directional luminaires

All ballasts & drivers used within the luminaire shall have a Class A sound rating.

Ballasts and drivers are recommended to be installed in the luminaire in such a way that in operation, the

luminaire will not emit sound exceeding a measured level of 24 Ba.

table 4: EnERgy stAR luminaire requirements

2.

DEfInE DEsIgn goALs

Typical 42-w cFl downlights use a lamp that produces about 3100 lm, but luminaire light output is only about 2000 lm,

giving a fixture efficiency of about 65%. We chose the design goals for this project, shown in Table 5, to better this

performance using less energy over a longer lifetime. We chose a 50° cutoff angle as a good balance between maximizing

direct illumination and minimizing glare. As shown in Figure 1, the cutoff angle is measured from the vertical axis of the

luminaire outward to the point at which the brightness of the light source is no longer visible.

figure 1: Cutoff angle

Characteristic

unit

minimum goal

target goal

light output

lm

2000

> 2000

Luminaire efficacy

lm/w

75

> 75

cutoff angle

degrees

50

50

lifetime

hours

35,000

50,000

ccT

K

3000

3000

crI

100-point scale

80

> 80

power

w

26

< 26

power factor

0.9

> 0.9

table 5: Design goals

3.

ESTImATE EffIcIENcIES Of ThE OpTIcAL, ThERmAL & ELEcTRIcAL SYSTEmS

We used Cree’s Product Characterization Tool (PCT) tool, shown in Figure 2, to determine the drive current for the

For the 2000‑lumen target, we estimated 90% optical efficiency and 87% driver efficiency. We also estimated a solder

point temperature (T

4

pcT is available at: pct.cree.com

light source

cutoff angle