AN1149-6 Lumileds Lighting, LLC, AN1149-6 Datasheet - Page 8

• Manufacturer Part Number: AN1149-6
• Description: Reliability Considerations for SuperFlux LEDs
• Manufacturer: Lumileds Lighting, LLC

Changes in Light Output During
the Operating Life of AlInGap
SuperFlux LEDs
The light output of SuperFlux LEDs will
gradually change during their lifetime. This
change is usually a gradual reduction in light
output; however it is also possible to have a
slight increase in light output during early
operation followed by a gradual reduction. This
change in light output is called light output
degradation. Typical amounts of light output
degradation for some popular automotive
applications are summarized in Table 6.3. Light
output degradation occurs most quickly during
the initial hours of operation and then slows with
time as shown in Figure 6.4. There is some
Table 6.3
Figure 6.4 Operating life test results for
HPWA-MHOO LEDs driven at 70mA, 55°C.
Lifetime Change in Light-Output for SuperFlux LEDs in Automotive Signaling Applications
Function
Stop
Turn
Tail
@ T
a
= 25°C; I
Lifetime Light Output Change
f
= 20 mA (Tail) and 60 mA (Stop and Turn)
Operating Life (h)
1,500 to 3,000
750 to 2000
200 to 700
8
variation within a batch and between batches of
SuperFlux LEDs. Figure 6.5 shows that the
amount of light output degradation is
proportional to forward current. This figure also
shows that some batches of SuperFlux LEDs get
slightly brighter before starting the typical
decline. Ambient temperature, humidity, and
sunlight have minimal effect on light output
degradation as shown in Table 6.4, Table 6.5,
and Figure 6.6. For SuperFlux LEDs, Lumileds is
careful to select AlInGaP material with an
average light output degradation of less than
35% after 1000 hours of operation at 70 mA.
Figure 6.5 Change in light-output over time
for HPWT-DHOO driven at multiple currents
at 55°C.
Typical LOP Change
30 to 5%
20 to 5%
5 to 5%