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Cree® XLamp® Long-Term Lumen Maintenance

IP.com Disclosure Number: IPCOM000201774D
Publication Date: 2010-Nov-22

Publishing Venue

The IP.com Prior Art Database

Abstract

This application note outlines Cree’s long-term testing methodology and provides Cree’s guidance on mean L70 lifetimes for XLamp XR-E LED lamps in a wide range of operating conditions. Using this application note, LED luminaire designers can predict the expected mean L70 lifetime of XLamp XR-E LEDs in a specific LED system, based on critical parameters.

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Cree® XLamp® Long-Term Lumen Maintenance

July 2009

This application note outlines Cree's long-term testing methodology and provides Cree's guidance on mean L70

lifetimes for XLamp XR-E LED lamps in a wide range of operating conditions. Using this application note, LED luminaire designers can predict the expected mean L70 lifetime of XLamp XR-E LEDs in a specific LED system, based on critical parameters.

High-power LED lamps typically do not fail catastrophically (i.e., fail to emit light) but will slowly decrease in light output over time. To characterize this gradual light loss, Cree uses both IES LM-80 compliant and other test methods.

Many high-power LED lamps do not reach L70 even after thousands of hours of testing. Therefore, Cree uses the available data to project the L70 lifetimes for the LED lamps under those operating conditions. Furthermore, Cree uses this information to develop methods of predicting L70 lifetimes for LED lamps under a wide range of operating parameters.

Table of Contents

Definitions & Concepts..............................................................................................................................2
IES LM-80-2008 Test Methodology..............................................................................................................3
Cree LM-80 Compliant Lumen Maintenance Test Configuration........................................................................3
Additional Lumen Maintenance Test Configurations........................................................................................4
Long-Term Testing Observations.................................................................................................................4
Functional Model for XLamp XR-E White Lumen Maintenance..........................................................................5
XLamp XR-E White L70 Lifetime Predictions...................................................................................................6
XLamp XR-E White L70 Lifetime Prediction Graphs - Grouped By IF ..................................................................6
XLamp XR-E White L70 Lifetime Prediction Graphs - Grouped By TA ..................................................................8

This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com.

For warranty information, please contact Cree Sales at sales@cree.com. Subject to change without notice.

Application Note: CLD-AP28 Rev. 0

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Definitions & Concepts

Forward Current (IF): The amount of current fLowing through an LED lamp operating in forward bias, typically mea- sured in milliamps (mA).

Forward Voltage (VF): The voltage potential across an LED lamp operating in forward bias, typically measured in Vo...