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.
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
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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
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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