This document discusses the thermal characteristics of LEDs. It shows that as the junction temperature of an LED increases, its light output decreases, forward voltage drops, color shifts to lower wavelengths, and maximum ratings can be exceeded. The document emphasizes that LED specifications are based on standardized testing conditions, while actual applications may have different thermal environments, so temperature effects must be considered in design.

1. LED Fundamentals
Thermal
Characteristics
of LEDs
08-16-2011

2. Energy Conversion
LED* Incandescent Bulb
8%
20%
19%
Visible Light
IR
73%
80%
Heat
light
eat
light
he
l
heat
T ~ 3000 K
TJ ~ 50 - 100°C
* Varies depending on LED efficacy. Source: http://www1.eere.energy.gov/buildings/ssl/comparing_lights.html
LED Fundamentals | Thermal Characteristics of LEDs | Page 2

3. Thermal Characteristics of LEDs
LED Junction Temperature
Light Output 
Forward Voltage 
LCW CQ7P
Color Coordinates 
Wavelength 
Increasing
LED Junction Temperature
LED Fundamentals | Thermal Characteristics of LEDs | Page 3

4. Light Output
decreases with higher junction temperature
g j p
Data Sheet LCW CQ7P.PC Effect in the Design
800 90 lm
81 lm
Luminous Flux [lm]
600
400
s
200
TJ = 25°C TJ = 80°C
0
LCW CQ7P: 90 lm @ 350 mA
LED Fundamentals | Thermal Characteristics of LEDs | Page 4

5. Forward Voltage
drops down with higher junction temperatures
p g j p
Data Sheet LCW CQ7P.PC Effect in the Design
LCW CQ7P
 IF = 350mA
 typ VF = 3.2 V
typ. 32
TJ= 80°C: VF = -0.17 V
typ. VF (350 mA; TJ = 80°C) = 3.03 V
LED Fundamentals | Thermal Characteristics of LEDs | Page 5

6. Chromaticity Coordinates
shifts to lower values with higher junction temperatures
g j p
Data Sheet LCW CQ7P.PC Effect in the design
Cy
Tj = 25˚C
Tj = 80˚C
Cx
LED Fundamentals | Thermal Characteristics of LEDs | Page 6

7. Dominant Wavelength
increases with higher junction temperature
g j p
Data Sheet LR CP7P Effect in the Design
TJ= 80°C: dom = 4nm
LED Fundamentals | Thermal Characteristics of LEDs | Page 7

8. Thermal Ratings
Data Sheet LCW CQ7P.PC
Maximum Ratings
Operation Temperature Range
p p g
Storage Temperature Range
Max. Junction Temperature
Characteristics
Ch t i ti
Thermal Resistance
LED Fundamentals | Thermal Characteristics of LEDs | Page 8

9. Designing with LEDs
“Grouping Environment
Grouping Environment” Application Environment
LED Characteristics
• Luminous Intensity
• Luminous Flux
• Wavelength
• Color Coordinates
 Each LED is measured in the • Forward Voltage  The application environment
production with specific • Reliability
R li bilit differs from the grouping
conditions. environment.
 LEDs are grouped into BINs  The temperature dependent
according to the measured characteristics of the LED have
characteristics. to be taken into account in the
g
design.
LED Fundamentals | Thermal Characteristics of LEDs | Page 9

10. Disclaimer
All information contained in this document has been checked with the greatest care.
OSRAM Opto Semiconductors GmbH can however, not be made liable for any damage
that occurs in connection with the use of these contents.
OSRAM Opto Semiconductor GmbH makes no representations and warranties as to a
possible interference with third parties' intellectual property rights in view of products
originating f
i i ti from one of OSRAM Opto Semiconductor GmbH's partners, or in view of
f O t S i d t G bH' t i i f
products being a combination of an OSRAM Opto Semiconductor GmbH's product and a
product of one of OSRAM Opto Semiconductor GmbH's partners. Furthermore, OSRAM
Opto Semiconductors GmbH cannot be made liable for any damage that occurs in
p y g
connection with the use of a product of one of OSRAM Opto Semiconductor GmbH's
partners, or with the use of a combination of an OSRAM Opto Semiconductor GmbH's
product and a product of one of OSRAM Opto Semiconductor GmbH's partners.
LED Fundamentals | Thermal Characteristics of LEDs | Page 10

11. Disclaimer
This document constitutes neither an offer to sell nor a solicitation to buy or subscribe
for securities. Any such offer will be made solely on the basis of the Securities
Prospectus yet to be approved by the German Financial Supervisory Authority
(BaFin) and published thereafter. The information legally required to be provided to
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The information contained herein is not for distribution, directly or indirectly, in or
into the United States of America (including its territories and possessions of any
State of the U i d S
S f h United States of A
f America or the Di i of C l bi ) and must not b
i h District f Columbia) d be
distributed to U.S. persons (as defined in Regulation S under the U.S. Securities Act
of 1933, as amended ("Securities Act")) or publications with a general circulation in
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America doc ment securities
United States of America. The securities have not been and will not be registered under
the Securities Act and may not be offered or sold in the United States of America
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This document is not an offer of securities for sale in the United Kingdom Canada
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LED Fundamentals | Thermal Characteristics of LEDs | Page 11

12. Thank you for your attention.
LED Fundamentals | Thermal Characteristics of LEDs | Page 12