TM-21-21

Projecting Long-Term Luminous, Photon, and Radiant Flux Maintenance of LED Light Sources

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ANSI/IES TM-21-21
Document Type: Technical Memorandum (TM)

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SKU: ANSI/IES TM-21-21 Category: Tag:

Product Description

Approved American National StandardThe rated flux maintenance life of an LED is the elapsed operating time over which an LED light source maintains a given percentage of its initial light output. The flux maintenance of an LED light source is dependent upon many variables, including the operating temperature, drive current, and technology and materials used to construct the product. As such, the flux maintenance of LEDs can vary not only from manufacturer to manufacturer, but also between different LED package types produced by a single manufacturer. Further, it is important to consider the inherent limits to projected source life as extrapolated from test data. This document updates its recommended method of projecting the flux maintenance of LED light sources from the data obtained by IES LM-80 testing. The update of this document was accomplished by a dedicated TM-21 Working Group of LED industry professionals. The analyses of the IES LM-80 test data provided by major LED manufacturers are used to rationalize and support this document. Much of the IES LM-80 data came from testing that extended to 9,000 hours, and in some cases beyond.

Page count: 43 pages
Publisher: Illuminating Engineering Society (2021)
SKU: ANSI/IES TM-21-21
ISBN-13: 978-0-87995-408-6

Chapters:

  • 1.0 Introduction and Scope
    2.0 Normative References
    3.0 Definitions
    4.0 Data and Sample Size
    5.0 Flux Maintenance Life Projection
    6.0 Temperature Data Interpolation
    7.0 Current Data Interpolation
    8.0 Simultaneous Temperature and Current Interpolation
    9.0 Limits for Extrapolation
    10.0 Report

Citation Format:
Illuminating Engineering Society. ANSI/IES TM-21-21, Technical Memorandum: Projecting Long-Term Luminous, Photon, and Radiant Flux Maintenance of LED Light Sources. New York: IES; 2021.

CONTENTS

  • 1.0 Introduction and Scope
  • 1.1 Introduction
  • 1.2 Scope
  • 2.0 Normative References
  • 3.0 Definitions
  • 3.1 DUT
  • 3.2 LED light source
  • 3.3 rated flux maintenance life, Tp
  • 4.0 Data and Sample Size
  • 4.1 Data to be Used
  • 4.2 Sample Size Recommendation
  • 4.3 Flux Data Collection
  • 4.4 Sample Selection and Data Usage
  • 5.0 Flux Maintenance Life Projection
  • 5.1 Method
  • 5.2 Procedures
    5.2.1 Normalization
    5.2.2 Average
    5.2.3 Data Used for Curve-Fit
    5.2.4 Curve-Fit
    5.2.5 Adjustment of Results
    5.2.6 Notation for Projected Flux Maintenance Life
    5.2.7 Limit for Projecting Flux Maintenance
  • 6.0 Temperature Data Interpolation
  • 6.1 Select Tested Case Temperatures
  • 6.2 Convert All Temperatures to Kelvins
  • 6.3 Use the Arrhenius Equation to Calculate the Interpolated Flux Maintenance Life
  • 7.0 Current Data Interpolation
  • 7.1 Select Tested Drive Currents
  • 7.2 Interpolate Between Drive Currents
  • 8.0 Simultaneous Temperature and Current Interpolation
  • 8.1 Current Data Interpolation for the Lower In-Situ DUT Case Temperature Conditions
  • 8.2 Current Data Interpolation for the Higher In-Situ DUT Case Temperature Conditions
  • 8.3 Temperature Interpolation Between Lower and Higher Current Interpolated In-Situ Case Temperatures
  • 9.0 Limits for Extrapolation
  • 10.0 Report
  • Annex A – Rationale for the Recommended Data Extrapolation Method
  • Annex B – Sample Size Selection for Data Extrapolation
  • Annex C – Least-Squares Formula
  • Annex D – Limit for Duration of Prediction
  • Annex E – Data Test Set for Validation of Calculation – Examples
  • Annex F – Consideration of Manufacturer’s Prediction Model
  • Annex G – Analysis of Mathematical Modeling as a Method of Projecting Lumen Maintenance Life
  • Annex H – Rationale for Method of Drive Current Interpolation
  • Annex I – Analysis of Uncertainty of Calculated Values of Alpha
  • Annex J – Interpolation of Value for B
  • Informative References

ARTICLES