Thermal Characteristics of LEDs: LED Fundamentals

LED Fundamentals

Thermal CharacteristicsCharacteristics of LEDs

08-16-2011

Energy Conversion

LED* Incandescent BulbLED*

20%

Visible Light

Incandescent Bulb

19%

8%

80%

Visible Light

HeatIR

73%

t light

eat

ligh

heat

l

he

T ~ 3000 KTJ ~ 50 - 100°C

LED Fundamentals | Thermal Characteristics of LEDs |

* Varies depending on LED efficacy. Source: http://www1.eere.energy.gov/buildings/ssl/comparing_lights.html

Thermal Characteristics of LEDs

LED Junction Temperature Light Output LED Junction Temperature

Forward Voltage Forward Voltage LCW CQ7P

Color Coordinates

Increasing

LED Junction Temperature

Wavelength


LED Junction Temperature

Light Outputdecreases with higher junction temperatureg j p

Effect in the DesignData Sheet LCW CQ7P.PC

800 90 lm

81 lm

s Fl

ux [l

m] 600

400Lu

min

ous

200

400

TJ = 25°C TJ = 80°C0

LCW CQ7P: 90 lm @ 350 mA


LCW CQ7P: 90 lm @ 350 mA

Forward Voltagedrops down with higher junction temperaturesp g j p

Effect in the DesignData Sheet LCW CQ7P.PC

LCW CQ7P IF = 350mA typ V = 3 2 V typ. VF = 3.2 V

TJ= 80°C: VF = -0.17 V

typ. VF (350 mA; TJ = 80°C) = 3.03 V


Chromaticity Coordinatesshifts to lower values with higher junction temperatures

Effect in the design

g j p

Data Sheet LCW CQ7P.PC

Cy

Tj = 25˚CTj = 80˚C

Cx


Cx

Dominant Wavelengthincreases with higher junction temperature

Effect in the DesignData Sheet LR CP7P

g j p

TJ= 80°C: dom = 4nm


Thermal RatingsData Sheet LCW CQ7P.PC

Operation Temperature Range

Maximum Ratings

p p g

Storage Temperature Range

Max. Junction Temperature

Ch t i ti

Thermal Resistance

Characteristics


Designing with LEDs

“Grouping Environment” Application Environment

LED Characteristics

Grouping Environment Application Environment

LED Characteristics

• Luminous Intensity• Luminous Flux• Wavelength• Color Coordinates• Forward Voltage

R li bilit Each LED is measured in the The application environment

• Reliabilityproduction with specific conditions.

LEDs are grouped into BINs

differs from the grouping environment.

The temperature dependent LEDs are grouped into BINs according to the measured characteristics.

The temperature dependent characteristics of the LED have to be taken into account in the design.


g

Disclaimer

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Thermal Characteristics of LEDs: LED Fundamentals

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