Work continues on three LED
lighting reliability standards
JIANZHONG JIAO details activity in IEC, IES groups, and the Lighting Research Center ASSIST alliance
in defining LED lamp and luminaire testing standards that can enable fair comparisons by lighting
designers, specifiers, and end users.
Even though LED lighting products hould present an advantage in excep- tional reliability, either with very long
lifetime, as required in general lighting, or with
profound robustness required in automotive
lighting, developing widely-acceptable LED
lighting product-level reliability standards
has been challenging in the industry. In past
years, the focus has been at the component
level: e.g., LED source lumen maintenance test
(ANSI/IES LM-80), lumen maintenance projection (IES TM- 21), catastrophic failure rate projection (IES TM- 26), and driver robustness test
(ANSI C82.16). As for solid-state lighting (SSL)
at the lamp or luminaire level, there remains
much work to be done on reliability tests and
projection standards, although we will examine recent progress here.
There has been a long debate in the industry
regarding who should write LED lighting reliability testing standards and how. Reliability
is often referring to a long lifetime with some
assurance of performance or failure prediction. The lighting industry has many years of
product qualification testing experience; however, commonly acceptable tests and methods
are not readily known — e.g., how long should
the tests be running? How should the test
data be interpreted so the lifetime of the product can be projected? Finding a consensus for
answering these questions has not been easy.
Most reputable LED and lighting manufac-
turers have conducted internal
reliability tests voluntarily.
The design for these tests
is often based on product
development and process
experience, as well as field
quality data, so selecting parameters for these tests may be considered a
trade secret for each manufacturer conducting the tests. On the other hand, regulatory
and market-transformation organizations
such as Energy Star, DesignLights Consortium
(DLC), the California Energy Commission, etc.
all wish to have standardized approaches to
allow comparisons for LED lamp and lumi-naire-level reliability measurements, including performance measurements, such as
lumen or color maintenance and catastrophic
failure rate. And lighting designers, specifiers,
and end users further have the same desire for
fair comparison purposes.
Contentious issues
There have been several arguments in
developing reliability test standards. The
first argument involves “what” should be
tested. The LED lighting products are sub-
jected to various environmental impacts:
temperature, humidity, dust, vibration,
chemical corrosion, etc., as well as appli-
cation impacts, including where the light-
ing products are used (indoor, outdoor), and
power on and off cycles. A common denom-
inator or minimum set of tests has not been
agreed upon by all parties.
The second argument involves “who” should
write the reliability testing standards. Even
though the IES Testing Procedures Committee
(TPC) has been developing many LED-related
measurements and test standards, the question was raised whether or not product reliability testing fits within the IES TPC scope. The
concern of some committee members, coming from a manufacturer, centered on whether
LED lighting products are being over-tested if
more testing standards are written. The third
argument relates to the validity and feasibility
of the reliability tests. Questions regarding how
long the tests should be running and if there
are any mathematical approaches that can be
used to make projections of the lifetime using
the test data have arisen.
Early efforts
Along the journey in developing LED lighting reliability test standards, the first
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standards | LAMPS & LUMINAIRES
DR. JIANZHONG JIAO, an internationally recognized lighting expert, is an independent consultant
for LEDs and lighting technologies. He has been actively involved in LED and LED lighting standard
development activities, technical conferences, and industry consortia. Currently
he serves on the IESNA Testing Procedures, Roadway Lighting, Computer, and
Light Source Committees. He is also vice chair of the ANSI SSL Light Source
Working Groups, and at present works with many other technical organizations,
groups, and symposia, in addition to being a member of the Technical Panel of
Strategies in Light. He can be reached at j _ jiao@hotmail.com.
FIG. 1. Packaged LEDs such as those
shown would fall under the scope of
the IEC’s efforts to establish principal
component reliability testing that
would enable standards developers to
determine appropriate test duration
and lifetime.
