IEC TS 62504:2011

General lighting - LEDs and LED modules - Terms and definitions

IEC/TS 62504:2011 presents terms and definitions relevant for lighting with LED light sources. It provides both descriptive terms (such as "built-in LED module") and measurable terms (such as "luminance").

Eclairage général - LED et modules de LED - Termes et définitions

La CEI/TS 62504:2011 présente des termes et des définitions concernant l'éclairage avec des sources lumineuses à LED. Elle donne à la fois des termes descriptifs (comme "module de LED incorporé") et des termes mesurables (comme "luminance").

General Information

• Status: Replaced
• Publication Date: 28-Mar-2011
• ICS: 29.140.20 - Incandescent lamps
• Technical Committee: TC 34 - Lighting
• Current Stage: DELPUB - Deleted Publication
• Completion Date: 19-Jun-2014

Relations

• Replaced By: IEC 62504:2014 - General lighting - Light emitting diode (LED) products and related equipment - Terms and definitions
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC/TS 62504


®


Edition 1.0 2011-03



TECHNICAL



SPECIFICATION



SPÉCIFICATION
TECHNIQUE
General lighting – LEDs and LED modules – Terms and definitions

Eclairage général – LED et modules de LED – Termes et definitions


IEC/TS 62504:2011

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---------------------- Page: 2 ----------------------
IEC/TS 62504


®


Edition 1.0 2011-03



TECHNICAL



SPECIFICATION



SPÉCIFICATION
TECHNIQUE
General lighting – LEDs and LED modules – Terms and definitions

Eclairage général – LED et modules de LED – Termes et definitions


INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX N
ICS 29.140.20 ISBN 978-2-88912-432-9

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

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– 2 – TS 62504 © IEC:2011



CONTENTS

FOREWORD . 3


1 Scope . 5

2 Normative references . 5

3 Terms and definitions . 5


Annex A (informative) Overview of systems composed of LED modules and control
gear . 14

Bibliography . 15


Figure 1 – Schematic drawing of the chain of thermal resistors . 13

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TS 62504 © IEC:2011 – 3 –


INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________



GENERAL LIGHTING –

LEDS AND LED MODULES –

TERMS AND DEFINITIONS





FOREWORD


1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
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with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
The main task of IEC technical committees is to prepare International Standards. In

exceptional circumstances, a technical committee may propose the publication of a technical
specification when
• the required support cannot be obtained for the publication of an International Standard,
despite repeated efforts, or
• The subject is still under technical development or where, for any other reason, there is
the future but no immediate possibility of an agreement on an International Standard.
Technical specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
IEC 62504, which is a technical specification, has been prepared by subcommittee 34A:
Lamps, of IEC technical committee 34: Lamps and related equipment.

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– 4 – TS 62504 © IEC:2011


The text of this technical specification is based on the following documents:


Enquiry draft Report on voting

34A/1355/DTS 34A/1418/RVC



Full information on the voting for the approval of this technical specification can be found in
the report on voting indicated in the above table.


This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• transformed into an International standard,
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

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TS 62504 © IEC:2011 – 5 –


GENERAL LIGHTING –

LEDS AND LED MODULES –

TERMS AND DEFINITIONS








1 Scope


This Technical Specification presents terms and definitions relevant for lighting with LED light

sources. It provides both descriptive terms (such as “built-in LED module”) and measurable
terms (such as “luminance”).
NOTE Annex A gives an overview of systems composed of LED modules and control gear.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60050-845:1987, International Electrotechnical Vocabulary – Chapter 845: Lighting
IEC 60061-1, Lamp caps and holders together with gauges for the control of
interchangeability and safety – Part 1: Lamp caps
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-845 and the
following apply.
3.1
ambient temperature
t
amb
average temperature of air or another medium in the vicinity of the LED or LED module
NOTE 1 During the measurement of the ambient temperature, the measuring instrument/probe should be shielded
from draughts and radiant heating.
[IEC 60050-826:2004, definition 826-10-03, modified]

[see also CIE 127, Subclause 2.2.5]
NOTE 2 Ambient temperature is expressed in Celsius degrees.
3.2
angular subtense
α
angle subtended by an apparent source as viewed from a point in space
The angle extension is determined by the observation distance, but at no distance smaller
than the minimum distance of accommodation.
NOTE 1 The location and angular subtense of the apparent source depends on the viewing position in the beam.
NOTE 2 The angular subtense of an apparent source is only applicable in the wavelength range from 380 nm to
1 400 nm, where eye hazard exists.

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– 6 – TS 62504 © IEC:2011


NOTE 3 The angular subtense of the source should not be confused with the beam divergence. The angular

subtense of the source cannot be larger than the divergence of the beam, but it is usually smaller than the
divergence of the beam


NOTE 4 In terms of optical radiation safety, the LED radiation source is a “middle sized source”, whose images

are projected on the retina under angles between 1,5 mrad and 100 mrad, i.e. the diameter of the retina image
extends between about 25 µm and 1 700 µm. For such sources, particularly, the hazard is strongly related to the

angular subtense on the observer’s retina.

[IEC 60825-1:2007, 3.7, modified]


NOTE 5 The angular subtense is expressed in degrees (°).


3.3

apparent source
for a given evaluation location of the retinal hazard, the real or virtual object that forms the
smallest possible retinal image (considering the accommodation range of the human eye)
NOTE 1 The accommodation range of the eye is assumed to be variable from 100 mm to infinity. The location of
the apparent source for a given viewing position in the beam is that location to which the eye accommodates to
produce the most hazardous retinal irradiance condition.
NOTE 2 This definition is used to determine, for a given evaluation position, the location of the apparent origin of
laser radiation in the wavelength range of 380 nm to 1 400 nm. In the limit of vanishing divergence, i.e. in the case
of a well collimated beam, the location of the apparent source goes to infinity.
[IEC 60825-1:2007, 3.10, modified]
3.4
beam angle
angle between two imaginary lines in a plane through the optical beam axis, such that these
lines pass through the centre of the front face of the lamp and through points at which the
luminous intensity is 50 % of the centre beam intensity
[IEC/TR 61341:2010, 2.4]
NOTE The beam angle is expressed in degrees (°).
3.5
bin
restricted range of LED performance characteristics used to delimit a subset of LEDs near a
nominal LED performance as identified by photometric performance and forward voltage
NOTE As the result of small but meaningful variations in the manufacturing process of LED wafers and
subsequent dies, the electrical and photometric characteristics of LEDs may vary from LED to LED, even when the
dies are from the same wafer. LEDs are sorted or binned in accordance with these characteristics, but there is no
existing standard for binning.

3.6
built-in LED module
LED module, generally designed to form a replaceable part built into a luminaire, a box, an
enclosure or the like and not intended to be mounted outside a luminaire, etc. without special
precautions
3.7
built-in self-ballasted LED module
self-ballasted LED module, generally designed to form a replaceable part built into a
luminaire, a box, an enclosure or the like and not intended to be mounted outside a luminaire,
etc. without special precautions
3.8
chromaticity coordinates
ratio of each of a set of three tristimulus values to their sum

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TS 62504 © IEC:2011 – 7 –


NOTE 1 As the sum of the three chromaticity coordinates equals 1, two of them are sufficient to define a

chromaticity.

NOTE 2 In the CIE standard colorimetric systems, the chromaticity coordinates are represented by the symbols x,

y, z and x , y , z .
10 10 10

[CEI 60050-845:1987, definition 845-03-33]


3.9

CIE 1974 general colour rendering index

R
a

mean of the CIE 1974 special colour rendering indices for a specified set of eight test colour

samples

[CEI 60050-845:1987, definition 845-02-63]
NOTE New definition of R for LED is under study.
a
3.10
dominant wavelength (of a colour stimulus)
λ
dom
wavelength of the monochromatic stimulus at 25 °C ambient temperature that when additively
mixed in suitable portions with the specified achromatic stimulus, matches the colour stimulus
considered
For characterising LED modules the reference achromatic stimulus should be illuminant E
which has the chromaticity coordinates x = 0,3333, y = 0,3333.
E E
NOTE 1 A value for dominant wavelength should only be stated for coloured modules. For white modules no
meaningful value for dominant wavelength can be given.
NOTE 2 Figure 12 in CIE 127 shows the relationship between colour locus C of LED and value of dominant
wavelength D. N is the locus of achromatic stimulus E.
NOTE 3 Deviating from the peak emission wavelength, the dominant wavelength determines visual impression.
[IEC 60050-845:1987, definition 845-03-44, modified]
NOTE 4 The dominant wavelength is expressed in nm.
3.11
forward direction
direction of current that results when the P-type semiconductor region connected to one
terminal is at positive potential relative to the N-type region connected to the other terminal
NOTE If temperature compensation diodes are included, these are ignored in the determination of forward
direction.

[IEC 60747-3:1985, 1.3 dans la Section 2]
3.12
forward voltage
U
F
potential difference pertaining to the forward direction, dependent on the forward current at
25 °C ambient temperature
NOTE The forward voltage is expressed in V.
3.13
illuminance (at a point of a surface)
E, E
v
quotient of the luminous flux dΦ incident on an element of the surface containing the point,
v
by the area dA of that element

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– 8 – TS 62504 © IEC:2011


Equivalent definition: Integral, taken over the hemisphere visible from the given point of the

expression L · cosΘ · dΩ, where L is the luminance at the given point in the various
v v

Ω, and Θ is the angle between
directions of the incident elementary beams of solid angle d

any of these beams and the normal to the surface at the given point.



E = dΦ /dA = (L × cosΘ × dΩ)
V v v
∫

2Πsr

[IEC 60050-845:1987, definition 845-01-38]

-2

NOTE Illuminance is expressed in lm × m .

3.14
independent LED module
LED module, so designed that it can be mounted or placed separately from a luminaire, an
additional box or enclosure or the like
The independent LED module provides all the necessary protection with regard to safety
according to its classification and marking.
NOTE The control gear must not necessarily be integrated in the module.
3.15
independent self-ballasted LED module
self-ballasted LED module, so designed that it can be mounted or placed separately from a
luminaire, an additional box or enclosure or the like
The independent LED module provides all the necessary protection with regard to safety
according to its classification and marking.
NOTE The control gear may be integrated in the module.
3.16
integral LED module
LED module, generally designed to form a non-replaceable part of a luminaire
3.17
integral self-ballasted LED module
self-ballasted LED module, generally designed to form a non-replaceable part of a luminaire
3.18
LED module
unit supplied as a light source. In addition to one or more LEDs it may contain further

components, e.g. optical, mechanical, electrical, and electronic, but excluding the control gear
3.19
life time of the LED related to junction temperature
t
nLED
time period at 25 °C ambient temperature and rated forward current, determined by a
minimum level of n % of the measured initial photometric parameter
The corresponding junction temperature has to be indicated. The use of forced cooling to
achieve the specified junction temperature must be stated.
NOTE The life time of the LED is expressed in hours.
3.20

life time of LED module related to t
C
t
nLED module
length of time during which n% (t ) of the measured initial luminous flux value are
nLED module
provided, as a function of t
C

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TS 62504 © IEC:2011 – 9 –


The use of forced cooling to achieve the specified junction temperature must be stated.


NOTE The life time of the LED module is expressed in hours.


3.21

light colour designation

three digit number, the first digit representing the first digit of the general colour rendering
index R [IEV 60050-845:1987, 845-02-63], and the second and third digit representing the

a
first two digits (thousands and hundreds) of the CCT of the light source


NOTE 1 The first digit of the light colour designation covers also the closest R value decreased by 3. Its highest
a
value is 9.

NOTE 2 The second and the third digit of the light colour designation cover also CCT values 49 K higher and 50 K
below. This method works only for CCT below 9.999 K.
3.22
light emitting diode
LED
solid state device embodying a p-n junction, emitting optical radiation when excited by an
electric current
[IEC 60050-845:1987, definition 845-04-40]
NOTE This definition is independent from the existence of enclosure(s) and of terminals.
3.23
luminance (in a given direction, at a given point of a real or imaginary surface)
L , L
V
quantity defined by the formula
L = dΦ /(dA × cosΘ × dΩ)
V V
where dΦ is the luminous flux transmitted by an elementary beam passing through the given
V
point and propagating in the solid angle dΩ containing the given direction; dA is the area of a
section of that beam containing the given point; Θ is the angle between the normal to that
section and the direction of the beam
[IEC 60050-845:1987, definition 845-01-35]

-2 -2 -1
NOTE The luminance is expressed in cd × m = lm × m × sr .
3.24
luminous efficacy of a source
η ,η
V

quotient of the luminous flux emitted by the electric power consumed by the source
[IEC 60050-845:1987, definition 845-01-55 modified]
-1
NOTE The luminous efficacy is expressed in lm × W .
3.25
luminous flux
Φ , Φ
V
quantity derived from radiant flux Φ by evaluating the radiation according to its action upon
e
the CIE standard photometric observer
For photopic vision
830
Φ = K (dΦ (λ)/dλ) × V(λ)dλ
V m e
∫
360

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– 10 – TS 62504 © IEC:2011


where dΦ (λ)/dλ) is the spectral distribution of the radiant flux and V(λ) is the spectral
e

luminous efficiency.


NOTE 1 For the values of K (photopic vision) and K’ (scotopic vision), see IEV 845-01-56.
m m

[IEC 60050-845:1987, definition 845-01-25, modified]


NOTE 2 The luminous flux of a LED is usually expressed in groups into which they are sorted.


NOTE 3 The luminous flux is expressed in lm.

3.26

luminous intensity (of a source, in a given direction)

I ; I
V
quotient of the luminous flux dΦ leaving the source and propagated in the element of solid
V
angle dΩ containing the given direction, by the element of solid angle
I = dΦ /dΩ
V V
[IEC 60050-845:1987, definition 845-01-31]
NOTE 1 The luminous intensity of LEDs is expressed according to CIE 127:2007 measurement procedure.
-1
NOTE 2 The luminous intensity is expressed in cd = lm × sr .
3.27
maximum permissible forward current

I
F,max
continuous maximum permissible current in forward direction
NOTE The maximum permissible forward current is expressed in mA.
3.28
maximum permissible power consumption
P
tot
maximum permissible input power
NOTE The maximum permissible power consumption is expressed in W.
3.29
maximum permissible reverse voltage
U
R
maximum permissible potential difference pertaining to the reverse direction
NOTE The maximum permissible reverse voltage is expressed in V.

3.30
rated maximum temperature
t
C
highest permissible temperature which may occur on the outer surface of the LED module (at
the indicated position, if marked) under normal operating conditions and at the rated
voltage/current/power or the maximum of the rated voltage/current/power range
[IEC 61347-1:2007, definition 3.16, modified]
NOTE The rated maximum temperature is expressed in degrees Celsius.
3.31
maximum permissible temperature of solder point
t
S
maximum permissible temperature at the solder point of the LED on the module during
declared life

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TS 62504 © IEC:2011 – 11 –


NOTE 1 Not to be confused with the temperature during the soldering procedure.

NOTE 2 The maximum permissible temperature of solder point is expressed in degrees Celsius.

3.32

non-ballasted single-capped LED lamp

single-capped LED lamp configured in a form in which the control gear and the LED lamp are

separated from each other


3.33

operating temperature range

t
op

ambient temperature range within which the LED or LED module with regard to the
specification can be operated
NOTE The operating temperature range is expressed in degrees Celsius.
3.34
peak emission wavelength
λ
p
wavelength at the maximum of the spectral distribution
[CIE 127, modified]
NOTE The peak emission wavelength is expressed in nm.
3.35
rated current
I
rated
value of the current for specified operating conditions
The value and the conditions are specified in the relevant standard or by the manufacturer or
responsible vendor.
NOTE The rated current is expressed in mA.
3.36
rated power
P
rated
value of the power for specified operating conditions
The value and the conditions are specified in the relevant standard or by the manufacturer or
responsible vendor.
NOTE The rated power is expressed in degrees W.

3.37
rated voltage
value of the voltage for specified operating conditions
The value and the conditions are specified in the relevant standard or by the manufacturer or
responsible vendor.
NOTE The rated voltage is expressed in V.
3.38
reverse direction
direction of current that results when the N-type semiconductor region connected to one
terminal is at a positive potential relative to the P-type region connected to the other terminal
NOTE If temperature compensation diodes are included, these are ignored in the determination of reverse
direction.

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– 12 – TS 62504 © IEC:2011


[IEC 60747-3:1985, 1.4 in Section 2]


3.39

self-ballasted LED lamp

unit which cannot be dismantled without being permanently damaged, provided with a lamp

cap conforming with IEC 60061-1 and incorporating a LED light source and any additional

elements necessary for stable operation of the light source


3.40

self-ballasted LED module

LED module, including control gear, designed for connection to the supply voltage

NOTE If the LED module which includes the control gear is equipped with a lamp cap, it is regarded to be a self-
ballasted lamp.
3.41
storage temperature range
t
stg
ambient temperature range within which a non-operated LED or LED module can be stored,
when the claims of the specification are maintained
NOTE The storage temperature range is expressed in degrees Celsius.
3.42
temperature coefficient of the dominant wavelength

tc
λdom
change in dominant wavelength at a fixed forward current as a function of the ambient
temperature
NOTE 1 The definition applies for independent LED modules without control gear.
NOTE 2 The definition applies to LED components, not to LED modules.
-1
NOTE 3 The temperature coefficient of the dominant wavelength is expressed in nm × K .
3.43
temperature coefficient of the forward voltage
tc
V
change in forward voltage at a fixed current as a function of the ambient temperature
-1
NOTE The temperature coefficient of the forward voltage is expressed in mV × K .
3.44
temperature coefficient of the photometric parameter

tc
Φ
change in photometric parameter at a fixed forward current as a function of the ambient
temperature
NOTE 1 The definition applies for independent LED modules without control gear.
-1 -1
NOTE 2 The temperature coefficient of the photometric parameter is expressed in lm × K , cd × K or
2 -1
cd × (m۬ K) .
3.45
thermal resistance of a LED module
R
Θ
the ratio of temperature difference to the corresponding power dissipation
NOTE 1 Measurement points should be at the junction, slug, board or ambient, the
...