Lumileds AB20-1 Using superflux leds in automotive signal lamp Datasheet

Application Brief AB201
Using SuperFlux LEDs in
Automotive Signal Lamps
Introduction
Lumileds Lighting SuperFlux LEDs are specifically designed for automotive
signal lamp applications and are designed to operate at high DC forward
currents reliably over the automotive temperature range. Each SuperFlux
LED generates several lumens of luminous flux. In addition, SuperFlux LEDs
have a low thermal resistance package, which reduces the temperature rise
within the LED signal lamp. This allows for higher drive currents and
reduces the loss in optical flux due to selfheating. SuperFlux LEDs allow
the designer to significantly reduce the number of LEDs needed to provide
the required light output.
The colors of SuperFlux LEDs are designed to be compatible with SAE and
ECE color requirements. SuperFlux LEDs are available in an amber color
with dominant wavelengths of 592 and 594 nm. Redorange and red
SuperFlux LEDs are available in three colors with dominant wavelengths of
618, 620, and 630 nm. The redorange color is designed to match the
color of filtered incandescent bulbs.
Index
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Signal Lamp Design Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Estimating the Number of SuperFlux LEDs Needed For a Signal Lamp . . . . . . . . . . . . . . . .5
Calculating the Minimum Number of LEDs Required . . . . . . . . . . . . . . . . . . . . . . . . . . .13
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
SuperFlux LEDs are available in several different optical radi
ation patterns, which allow the designer to optimize his
secondary optics for different signal lamp designs. Currently,
SuperFlux LEDs are available with round and rectangular
radiation patterns. The round radiation patterns are ideal for
single and multiple row LED arrays (with the same pitch in x
and y dimensions). The rectangular radiation pattern is ideal
for CHMSL applications that require longer aspect ratios
than can be obtained from LEDs with round radiation
patterns. Please refer to the SuperFlux LED Data Sheet for a
current list of available viewing angle options.
SuperFlux LEDs have a lowprofile package, which is
compatible with highvolume automatic insertion equipment.
SuperFlux LEDs are categorized for luminous flux, dominant
wavelength, and forward voltage, which improves the
matching between LEDs within the signal lamp. SuperFlux
LEDs are packaged in tubes with 60 matched LEDs per tube
and shipped in bundles of 1200 matched LEDs, which
simplify the assembly of LED signal lamps.
The Application Note series 1149 has been prepared in order
to simplify the design process using SuperFlux LEDs in auto
motive signal lamps. This application note series has been
subdivided into the following application notes:
AB201
AB203
AB204
AB205
AB206
AB207
Using SuperFlux LEDs In Automotive Signal
Lamps
Electrical Design Considerations for SuperFlux
LEDs
Thermal Management Considerations for
SuperFlux LEDs
Secondary Optics Design Considerations for
SuperFlux LEDs
Reliability Considerations for SuperFlux LEDs
SuperFlux LED Categories and Labels
These application notes are available from your local
Lumileds Lighting or Agilent Technologies Field Sales
Engineer or from the following URL: www.lumileds.com
SuperFlux LEDs in Automotive Application Brief AB201 (5/04)
2
lamp using estimates for these different factors and to iterate
the optical, mechanical, thermal, and electrical designs
based on bench testing of prototype signal lamps.
Signal Lamp Design Process
The design of an LED signal lamp consists of four inde
pendent but interrelated designs: optical design, mechanical
design, thermal design, and electrical design.
A flow chart of the basic design process for an LED signal
lamp is shown in Figure 1.1 and consists of the following
steps:
The optical design is needed in order to design the secondary
optics elements, such as reflectors or lenses, which are
mounted in front of the LED emitters. In addition, the outer
pillow lens needs to be designed in order to generate the
desired output beam pattern. The optical design of an LED
signal lamp is not unlike that of an incandescent signal lamp,
except that the LED emitters have a much smaller geometry
and a different optical radiation pattern.
1. Define external operating parameters for the signal lamp.
These parameters are usually specified by the car manu
facturer or defined in various automotive specifications.
These parameters include:
• Operating and storage temperature requirements for
the signal lamp.
• Photometric test conditions of the signal lamp (i.e.,
whether testing is done at initial turnon at room
temperature, after a 30 minute warmup at room
temperature, or over some operating temperature
range).
• Design voltage (the voltage at which the photometrics
will be tested).
• Operating voltage range (i.e., 9 V to 16 V).
• Transient operating voltage range (i.e., 24 V for 1
minute).
• EMC transients applied to the signal lamp (i.e., SAE
J1113 pulses 1 through 7 and theamplitude and dura
tion of each pulse).
• Whether any additional photometric guard band is
required above the minimum photometric require
ments defined by the SAE or ECE standards.
A mechanical design is needed in order to generate the
desired mechanical drawings for the outer case, outer lens,
and possibly internal secondary optics. The mechanical
design would also include the selection of materials used for
the signal lamp assembly. The mechanical design is not
unlike the mechanical design of an incandescent signal lamp.
The purpose of the thermal design is to evaluate the heat
flow from the LED emitters to the ambient air and to reduce
the thermal resistance as much as possible. For best results,
the LED signal lamp should be designed to minimize self
heating of the LED emitters. SuperFlux LEDs are limited to a
maximum junction temperature of 125°C. In addition, all
LEDs experience a reduction in light output at elevated
temperatures. This phenomena is fully reversible, such that
the light output returns to its original value when the in the
temperature returns to its initial value. However, selfheating
causes an undesirable reduction in the luminous flux output
of the LEDs. The thermal design of an LED signal lamp
differs from that of an incandescent design. For an incandes
cent design, the design focus is to choose plastic materials
that can withstand the heat generated by the bulb. For the
LED lamp design, the focus is to protect the LEDs from high
temperatures and to optimize the optical performance.
Please refer to AB206 for a summary of environmental
strife tests that have been used to validate Super Flux
LEDs as well as suggested assembly validation tests for
automotive applications.
The purpose of the electrical design is to choose the appro
priate forward current through the LED emitters and ensure
that this current stays within an acceptable range during
worstcase operation at the extremes of ignition voltage and
temperature. Also, the electrical circuit configuration deter
mines the luminous intensity matching between the emitters
within the LED signal lamp. In addition, the electrical design
can also protect against EMC transients, and highvoltage
and lowvoltage transient conditions. In many cases, an elec
trical design is not needed for an incandescent signal lamp
since the bulb can be driven directly from the ignition voltage.
These four design processes are interrelated. For example,
the mechanical drawings used to construct the signal lamp
cannot be completed until the optical, thermal, and electrical
designs are finished. Since these different design processes
are interrelated, it is not uncommon to design the LED signal
SuperFlux LEDs in Automotive Application Brief AB201 (5/04)
3
Figure 1.1 LED Signal Lamp Design Process.
LEDs Needed For a Signal Lamp contained in this
application note.
2. Determine the SuperFlux LED luminous flux, and forward
voltage categories to be used for the signal lamp.
Category ranges for SuperFlux LEDs are discussed in
AB207. Your local LumiLeds Lighting or Agilent
Technologies Field Sales Engineer should be consulted
to determine which category ranges should be used for
a given model year design.
7. Pick the circuit topology. Circuit topology refers to the
electronic circuit schematic without the electronic
component values. The key factors of circuit topology for
an LED signal lamp include the following considerations:
• Dimensions of the LED array (i.e., number of strings
of SuperFlux LEDs and how many seriesconnected
SuperFlux LEDs per string).
• Interconnection scheme for the LED emitters within
the LED array.
• Current limiting method (i.e., resistive or active
current limiting).
• EMC transient protection circuit (if any).
• Dimming circuit (such as for a Stop/Tail signal lamp).
Please refer to AB203 for a detailed discussion of
electrical design considerations.
3. Complete the optical design of the outer lens and
secondary optics (i.e., lens or reflectors mounted over
each LED emitter). AB205 provides some useful guide
lines on the different options available for secondary
optic designs. Estimate the percentage of optical flux
coupled through the secondary optics and pillow lens
and the percentage of optical flux transmitted through the
outer lens and any other optical surfaces. For a discus
sion of optical flux losses, please see the following section
of this application note titled Estimating the Number of
SuperFlux LEDs Needed For a Signal Lamp.
8. Calculate the nominal values of circuit components [i.e.,
current limiting resistor(s)] using nominal values for the
LED forward voltage. A simple linear model for the
forward voltage of SuperFlux LEDs is given in AB203.
4. Complete the thermal design of the LED signal lamp and
estimate the overall thermal resistance, Rθja, of the
signal lamp. Some useful thermal design guidelines and
a thorough discussion of the measurement techniques
and typical ranges for Rθja are provided in AB204.
9. Estimate the effects of overvoltage and EMC transients
on maximum forward current through the SuperFlux
LEDs as desired. A discussion of EMC transient protec
tion circuits is given in AB203.
5. Estimate the maximum DC forward current per SuperFlux
LED based on the overall thermal resistance, Rθja, of the
LED signal lamp, and maximum ambient temperature,
using Figure 4 on the SuperFlux LED Data Sheet.
10. Calculate expected values of luminous flux at 25°C and
over operating temperature as desired. A discussion of
how luminous flux varies over temperature is given in
AB203 and AB204.
6. Estimate the number of SuperFlux LED emitters
needed for the signal lamp. This topic will be covered in
the section titled Estimating the Number of SuperFlux
SuperFlux LEDs in Automotive Application Brief AB201 (5/04)
4
Estimating the Number of
SuperFlux LEDs Needed For a
Signal Lamp
11. Complete the electrical design. Perform a worstcase
circuit analysis using worstcase values for the LED
forward voltage to ensure that the maximum forward
current in Step 5 is not exceeded. Worstcase forward
voltage ranges for SuperFlux LEDs are given in AB203.
Note: If the worstcase circuit analysis indicates that the
maximum allowable DC forward current calculated in
Step 5 is exceeded, then Steps 7 through 10 should be
repeated using different assumptions for circuit topology
and nominal forward current.
The number of SuperFlux LEDs needed for a signal lamp can
be easily estimated. This is done by calculating the minimum
luminous flux needed to meet the regulated photometric
minimums, dividing this by the minimum luminous flux
emitted by each SuperFlux LED, and then accounting for all
luminous flux losses in the signal lamp. This process is
summarized in a Microsoft Excel spreadsheet program that
is available from Lumileds. The general calculations that are
used within the spreadsheet are discussed in this section.
These general calculations use a numerical method called
zonal constant integration.
12. Complete the mechanical design and fabricate LED
signal lamp using prototype tooling.
13. Build working prototypes of the LED signal lamp to verify
the electrical circuit design parameters. Prototypes
should be built from different LED categories spanning
the expected forward voltage and luminous flux distribu
tions. Measure LED forward currents over the expected
range of operating voltages. Measure overall LED signal
lamp thermal resistance, Rθja, using the test procedure
outlined in AB204. Measure the photometric output of
the LED signal lamp at each angular test point in order
to verify the assumptions used in Steps 2 through 6.
Optical measurements should use datalogged LEDs
and the photometric results should be scaled to the
luminous flux bin minimums given in AB207.
In general, the minimum luminous flux emitted by any LED
can be estimated from the onaxis luminous intensity cate
gory and the viewing angle. For the SuperFlux LED family,
the luminous flux is 100% tested and the LEDs are sorted
into welldefined luminous flux categories. These categories
are defined in AB207.
It is also important to consider luminous flux losses within the
LED signal lamp. From experience, these luminous flux
losses are quite large—although not as large as those for an
incandescent signal lamp. The net effect of these luminous
flux losses is that a total of 4 to 10 times more luminous flux
is needed from the SuperFlux LED array than would be
required if the optical system were completely lossless.
Based on the measurements of the prototypes, the
electrical design may need to be further optimized.
A thorough discussion of the effects of different circuit
designs is provided in AB203.
The zonal constant integration technique can be used to
calculate the minimum luminous flux emitted for a given type
of signal lamp. The zonal constant integration technique is a
numerical method where the total luminous flux emitted by
the signal lamp is calculated by summing the amounts of
incremental luminous flux emitted by the signal lamp at
discrete angular positions at all angles where the luminous
intensities are greater than zero. The amount of luminous flux
emitted by each incremental angular position is equal to the
average luminous intensity of each incremental emitting area
multiplied by the solid angle subtended between the speci
fied incremental emitting area and the adjacent emitting
areas, such as shown in Figure 1.2.
Based on the measurements of the prototypes, the
thermal resistance of the signal lamp may need to be
further optimized. A thorough discussion of the thermal
design factors is provided in AB204.
Based on the measurements of the prototypes, the
optical design may need to be further optimized. A thor
ough discussion of the optical design of the LED signal
lamps is provided in AB205.
Note: If measurements of the prototype LED signal
lamps indicate that the assumptions for LED forward
voltage, Rθja, and luminous flux utilization are wrong,
then Steps 2 through 12 should be repeated using
measured values or new assumptions based on revised
electrical, thermal, or optical designs.
For sake of convenience, the radiation pattern of the signal
lamp can be considered to consist of a number of horizontal
bands (i.e., H, 5U, 5D, 10U, 10D, etc.).
Then the amount of luminous flux emitted by the signal lamp
into each horizontal band is equal to the summation of the
nonzero luminous intensities of all points in the horizontal
band multiplied by a constant, CZ, called the zonal constant.
The total luminous flux emitted by the signal lamp is equal to
the summation of the amounts of luminous flux emitted by all
of the horizontal bands. Written mathematically, the luminous
flux is equal to:
14. Build additional LED signal lamps using the final elec
trical, thermal, and optical design. Perform additional
testing to verify the expected ranges for forward current,
thermal resistance, and photometric output. Validate reli
ability of final design using automotive reliability tests
such as those given in SAE J575, SAE J1889, corre
sponding ECE or other regulations, or AB206.
SuperFlux LEDs in Automotive Application Brief AB201 (5/04)
5
⎡
φv ≅ ∑ ⎢Cz(δ )
all δ horizontal ⎣
bands with IV > 0
C z ( δ) ≅
As an example of the zonal constant integration technique,
consider the total luminous flux emitted by an automotive
amber rear turn signal (a similar example for an automotive
rear brake lamp is given in Stringfellow, HBLED, pp
246—247). The U.S. requirements for the rear amber turn
signal are contained in SAE J588 titled Turn Signal Lamps
For Use On Motor Vehicles Less Than 2032 mm In Overall
Width. The minimum photometric design guidelines are
shown in Table 1.1. Note that the minimum luminous intensi
ties are specified over a range of 10 degrees up and down
and 20 degrees left and right.
⎤
∑ IV(θ,δ )⎥
⎦
all θ within
m/2
n
horizontal band
4 π2
cos (δ )
nm
Where:
Φv
= total luminous flux emitted by the light source
Iv(θ,δ) = luminous intensity emitted at angular position θ
degrees left/right and δ degrees up/down.
n
= number of horizontal divisions that an imaginary
sphere surrounding the signal lamp is subdivided
into. For example, for 5° increments, n =
360°/5° = 72.
m
= number of vertical divisions that an imaginary
sphere surrounding the signal lamp is subdivided
into. For example, for 5° increments, m =
360°/5° = 72.
δ
= vertical angle of midpoint of horizontal band.
For example, for 5° horizontal bands (i.e., m = 72),
the midpoint of the horizontal band covering
angles from –2.5° to 2.5° would have a value
of δ = 0° and the midpoint of the horizontal band
covering angles from 2.5° to 7.5° would have a
value of δ = 5°.
Since most photometric specifications are specified
in horizontal and vertical increments of 5°, the zonal
constant is equal to:
4 π2
cos ( δ , in increments of 5 ° )
722
= 0.007615 cos ( δ )
Cz ( δ ) =
Tip: Since most automotive signal lamps are only specified
over a narrow range of up and down angles, typically 15U to
15D, in increments of 5 degrees left and right, then the zonal
constant, CZ (δ), is approximately equal to 0.0076.
For a detailed derivation of the zonal constant
integration technique, please see G. B. Stringfellow and
M. George Craford, High Brightness Light Emitting Diodes,
pp. 233—246.1
Figure 1.2 Zonal Constant Integration.
SuperFlux LEDs in Automotive Application Brief AB201 (5/04)
6
luminous flux values for each horizontal band. For example,
referring to the 10U row of Table 1.2, the luminous flux
emitted within the horizontal band (from 7.5° to 12.5°) is
equal to:
Note that not all luminous intensity points in Table 1.1 are
specified. Therefore, the first step in calculating the minimum
luminous flux is to estimate the luminous intensity values for
the unspecified coordinates (e.g., 5L, 5U and 15L, 10U). A
reasonable assumption is that the luminous intensities of the
unspecified points are equal to the average values of the
luminous intensities of the four adjacent points. Using these
assumptions, the minimum luminous intensities of all of the
unspecified points are shown in Table 1.2. Next the zonal
constant integration is calculated by adding the luminous
intensity values in each horizontal band (e.g., 10U, 5U, etc.)
and multiplying by the zonal constant. Finally, the total lumi
nous flux of the signal lamp is simply equal to the sum of the
ΦV ≅ (1 + 10 + 17 + 24 + 26 + 42 + 26 + 24
⎛ 4 π2 ⎞
+ 17 + 10 + 1) ⎜ 2 ⎟ cos (10 °)
⎝ 72 ⎠
ΦV ≅ (1 + 10 + 17 + 24 + 26 + 42 + 26 + 24
+ 17 + 10 + 1) (0.00750)
ΦV ≅ (198) (0.00750) ≅ 1.48lm
Table 1.1 Minimum photometric design guidelines for a single compartment amber rear turn signal. All values in the
table are in candela (cd). Note: Maximum luminous intensity at any point is 750 cd.
20 L
10U
5U
H
5D
10D
10 L
5L
V
5R
26
15
50
65
15
10R
20R
50
15
26
110
130
130
50
130
65
110
50
26
15
26
Table 1.2 Zonal constant integration of minimum photometric design guidelines for a single compartment amber
rear turn signal. Note: Parentheses indicate estimated minimum luminous intensity of unspecified points.
10 L
5L
V
5R
10R
Sum
Zonal
Constant
Flux
lm
20
7.36e3
0.15
(10)
(1)
198
7.50e3
1.48
(30)
15
(1)
460
7.59e3
3.49
(39)
(20)
(2)
642
7.62e3
4.89
20 L
(1)
(2)
(2)
(3)
(4)
(3)
(2)
(2)
(1)
10U
(1)
(10)
(17)
(24)
26
(42)
26
(24)
(17)
5U
(1)
15
(30)
50
(79)
110
(79)
50
H
(2)
(20)
(39)
65
130
130
130
65
15U
15 L
25R
25 L
15R
20R
5D
(1)
15
(30)
50
(79)
110
(79)
50
(30)
15
(1)
460
7.59e3
3.49
10D
(1)
(10)
(17)
(24)
26
(42)
26
(24)
(17)
(10)
(1)
198
7.50e3
1.48
(1)
(2)
(2)
(3)
(4)
(3)
(2)
(2)
(1)
15D
SAE J222
SAE J585
7.36e3
0.15
Total, lm
15.13
Parking Lamps (Front Position Lamps)
Tail Lamps (Rear Position Lamps) For Use
on Motor Vehicles Less Than 2032 mm in
Overall Width
SAE J586 Stop Lamps for Use on Motor Vehicles Less
Than 2032 mm in Overall Width
SAE J588 Turn Signal Lamps for Use on Motor Vehicles
Less Than 2032 mm in Overall Width
SAE J592 Clearance, Side Marker, and Identification Lamps
SAE J914 Side Turn Signal Lamps for Vehicles Less Than
12 m in Length
SAE J1319 Fog Tail Lamp (Rear Fog Light) Systems
SAE J1957 Center High Mounted Stop Lamp Standard for
Vehicles Less Than 2032 mm in Overall Width
SAE J2087 Daytime Running Lamps For Use on Motor
Vehicles
Using a similar approach, zonal constant integrations for
most commonly used automotive signal lamps were calcu
lated and are shown in Tables 1.3 and 1.4. The minimum
luminous flux requirements for U.S. signal lamps are shown
in Table 1.3. The minimum luminous flux requirements for
European signal lamps are shown in Table 1.4. The values
shown are based on the minimum photometric guidelines for
single compartment lamps.
The specifications for U.S. motor vehicle signal lamps are
written by the Society of Automotive Engineers (SAE). These
publications are published in SAE publication HS34 titled
SAE Ground Vehicle Lighting Standards Manual, which is
updated annually. The primary signal lamp specifications for
passenger cars are as follows:
SuperFlux LEDs in Automotive Application Brief AB201 (5/04)
20
7
Table 1.3 Minimum luminous flux requirements based on the zonal constant integration of different single compart ment U.S. automotive signal lamps.
Function
Signal
U.S. Spec
Color
Lit Area
(cm2)
Front
Turn/Park
Lamp
Turn
SAE J588
Amber
≥ 22
Side Turn
Lamp
Rear
Combination
Max IV
[H, V]
(cd)
Min IV
[H, V]
(cd)
Min Φv
(lm)
—
200
23.3
Note 1, 2
300
33.7
Note 1, 2
400
44.2
Note 1, 2
500
54.7
Note 1, 2
Notes
Position
Not defined
Park
SAE J222
White, Amber
—
—
4
0.40
Note 2
Turn
SAE J914
Amber
—
200
0.6
0.21
Note 3
Park
Not defined
Turn
SAE J588
Red
≥ 37.5
300
80
9.5
Amber
≥ 37.5
750
130
15.1
Stop
SAE J586
Red
≥ 37.5
300
80
9.4
Note 4
Position
SAE J585
Red
—
18
2
0.28
Note 4
Reverse
SAE J593
White
—
500
80
15.2
Rear Fog
SAE J1319
Red
—
300
80
9.0
Park
Not defined
CHMSL
Stop
SAE J1957
Red
≥ 29
130
25
3.1
Daytime
Running
Lamp
Day
SAE J2087
White, Sel
Yellow, Amber
≥ 40
7000
500
39.3
Side Marker
Lamp
Front
SAE J592
Amber
—
—
0.62
0.47
Rear
SAE J592
Red
—
18
0.25
0.19
Front
SAE J592
Amber
—
—
0.62
0.47
Rear
SAE J592
Red
—
18
0.25
0.19
End Outline
Marker Lamp
Note 5
Note 1: Minimum luminous intensity requirement is increased if the Front Turn signal (FTS) is mounted in close proximity to Low Beam headlamp
(LB). If spacing from center of the FTS is less than 100 mm from the lit edge of the low beam headlamp, increase minimum IV as follows:
Spacing Between FTS and LB Headlamp
75 mm ≤ spacing < 100 mm
60 mm ≤ spacing < 75 mm
Spacing < 60 mm
Multiplier
1.5
2.0
2.5
Note 2: If the Park signal is combined with the Front Turn signal, at (H, V) the luminous intensity of the Front Turn should be ≥ 5x luminous inten
sity of the Park signal.
Note 3: Supplemental to Front Turn signal.
Note 4: If the Rear Position signal is combined with the Stop or Turn signal, at (H, V) the luminous intensity of the Stop/Turn signal should be ≥
5x luminous intensity of the Rear Position signal.
Note 5: Installation allows either one Rear Fog lamp on the vehicle centerline or to the left of centerline or two lamps symmetrically placed on
either side of centerline.
SuperFlux LEDs in Automotive Application Brief AB201 (5/04)
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ECE Regulation 48 Uniform Provisions Concerning the
Approval of Vehicles with Regard to the
Installation of Lighting and LightSignaling
Devices
The specifications for European motor vehicle signal lamps
are written by the Economic Commission of Europe (ECE).
Within these regulations, the different signal lamps are further
subdivided into different categories. The primary specifica
tions and categories for passenger cars are as follows:
ECE Regulation 77Uniform Provisions Concerning the
Approval of Parking Lamps for Power
Driven Vehicles
ECE Regulation 6 Uniform Provisions Concerning the
Approval of Direction Indicators for Motor
Vehicles and Their Trailers
ECE Regulation 87 Uniform Provisions Concerning the
Approval of Daytime Running Lamps for
PowerDriven Vehicles
Cat 1: Front Turn signal mounted greater than 40
mm from the headlamp.
ECE Regulation 91 Uniform Provisions Concerning the
Approval of SideMarker Lamps for
Motor Vehicles and Their Trailers
Cat 1a: Front Turn signal mounted greater than 20
mm but less than 40 mm from the head
lamp.
Cat 1b: Front Turn signal mounted less than 20
mm from the headlamp.
Cat 2a: Rear Turn signal with single level of inten
sity.
Cat 2b: Rear Turn signal with two levels of intensity
(day and night operation).
Cat 3: Side Turn signal for vehicles without Front
and Rear Turn signals.
Cat 4: Front/Side Turn signal that replaces Front
Turn and is supplemental to the Rear Turn
signal.
Cat 5/6: Supplementary Side Turn signal for vehi
cles that also have Front and Rear Turn
signals.
ECE Regulation 7 Uniform Provisions Concerning the
Approval of Front and Rear Position (Side)
Lamps, StopLamps and EndOutline
Marker Lamps for Motor Vehicles (Except
Motor Cycles) and Their Trailers
Cat S1: Stop lamp with one level of intensity.
Cat S2: Stop lamp with two levels of intensity (day
and night operation).
Cat S3: Center High Mount Stop lamp
ECE Regulation 23 Uniform Provisions Concerning the
Approval of Reversing Lamps for Power
Driven Vehicles and Their Trailers
ECE Regulation 38 Uniform Provisions Concerning the
Approval of Rear Fog Lights for Power
Driven Vehicles and Their Trailers
SuperFlux LEDs in Automotive Application Brief AB201 (5/04)
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Table 1.4 Minimum luminous flux requirements based on the zonal constant integration of different single compart ment ECE. automotive signal lamps..
Max IV
[H, V]
(cd)
Min IV
[H, V]
(cd)
Min Φv
(lm)
Function
Signal
ECE Spec
Color
Lit Area
(cm2)
Front
Turn/Park
Lamp
Turn
Reg 6, Cat 1
Reg 6, Cat 1a
Reg 6, Cat 1b
Amber
Amber
Amber
—
—
—
700
600
860
175
250
400
15.9
22.6
36.3
Position
Reg 7
White
—
60
4
0.41
Park
Reg 77
White
—
60
2
0.13
Amber
Amber
Amber
Amber
Amber
Amber
—
—
—
—
—
—
700 (front)
200 (rear)
700 (front)
200 (rear)
200
200
175 (front)
50 (rear)
175 (front)
0.6 (rear)
0.6
50
13.3
3.9
14.4
0.39
0.39
10.3
Side Turn/Park
Lamp
Rear
Combination
Lamp
CHMSL
Turn
End Outline
Marker Lamp
6,
6,
6,
6,
6,
6,
Cat
Cat
Cat
Cat
Cat
Cat
3
3
4
4
5
6
Park
Reg 77
Amber
—
—
60 (front)
30 (rear)
2
2
0.13
0.13
Turn
Reg 6, Cat 2a
Reg 6, Cat 2b
Amber
Amber
—
—
350
700 (day)
50
175 (day)
4.7
15.9 (day)
Stop
Reg 7, Cat S1
Reg 7, Cat S2
Red
Red
—
—
185
520 (day)
60
130 (day)
5.5
11.8 (day)
Position
Reg 7
Red
—
12
4
0.41
Reverse
Reg 23
White
—
300 (up),
600 (down)
80
15.2
Rear Fog
Reg 38
Red
≤ 140 cm2
300
150
12.4
Park
Reg 77
Red
—
30
2
0.13
Stop
Reg 7, Cat S3
Red
—
80
25
3.1
Reg 87
White
≥ 40 cm2
800
400
37.8
Front
Reg 91, Cat SM1
Reg 91, Cat SM2
Amber
Amber
—
—
25
25
4
0.6
0.54
0.32
Rear
Reg 91, Cat SM1
Reg 91, Cat SM2
Red, Amber
Red, Amber
—
—
25
25
4
0.6
0.54
0.32
Front
Reg 7
White
—
60
4
0.41
Rear
Reg 7
Red
—
12
4
0.41
Daytime
Running
Lamp
Side Marker
Lamp
Reg
Reg
Reg
Reg
Reg
Reg
Notes
Note 1
Note 1
Note 1
Note 2
Note 2
Note 2
Note 3
Note 2
Note 4
Note 4
Note 1: Minimum luminous intensity requirement is increased if the Front Turn signal (FTS) is mounted in close proximity to Low Beam headlamp (LB).
ECE Reg 6 Front Direction Indicator
Category 1
Category 1a
Category 1b
Spacing Between FTS and LB Headlamp
spacing ≥ 40 mm
20 mm < spacing < 40 mm
spacing ≤ 20 mm
Note 2: Vehicles should either have two Front Parking lamps and two Rear Parking lamps or one Side Parking lamp on either side. The Front
Park is normally white. The Rear Park is normally red. However, Parking Lamps can be amber if reciprocally combined with the Side Turn
lamps or Side Marker lamps.
Note 3: In the case where a Rear Position lamp is reciprocally combined with a Category S1 Stop lamp, the ratio of luminous intensities (both ON
divided by Rear ON only) should be greater than 5:1. In the case where Rear Position lamp is reciprocally combined with a Category S2
Stop lamp, the ratio of luminous intensities (nighttime S2 Stop ON plus Rear ON, divided by Rear ON only) should be greater than 5:1.
Note 4: The rear Side Markers should emit amber light. However, it can emit red light if reciprocally combined with the Rear Position lamp, End
Outline lamp, Rear Fog lamp or Stop lamp. Rear Side Markers should be amber if they flash with the Rear Turn lamp.
SuperFlux LEDs in Automotive Application Brief AB201 (5/04)
10
In order to estimate the number of SuperFlux LED emitters
needed to realize an LED signal lamp, it is important to
account for wasted luminous flux. In addition, the useful
amount of luminous flux emitted by each SuperFlux LED may
be somewhat lower than the luminous flux categories would
indicate. As previously described, these losses may require
the LED array to generate substantially more luminous flux
than indicated by the values in Tables 1.3 and 1.4. For
simplicity, it is possible to create two equations that estimate
the overall flux utilization. The first equation accounts for
luminous flux losses in the outer lens, exterior surfaces (i.e., a
behindtheglass CHMSL), and inaccuracies in the output
radiation pattern. The second equation adjusts the amount
of luminous flux emitted by the SuperFlux LEDs. This equa
tion accounts for selfheating within the LED array and
luminous flux collection and transmission losses in the
secondary optics.
(
Tsignal = (Tfiller ) Tglass
pattern
= total luminous flux transmission losses
associated with the output radiation
pattern and outer lens surfaces.
Note: 0 ≤ Tsignal ≤ 1
Tfiller
= optical transmission of the plastic outer
lens.
Tglass
= optical transmission of the glass window
for behindtheglass CHMSL.
Lpattern
= luminous flux losses due to radiation
pattern inaccuracy.
(
)
⎛ ∆Φ ⎞
TLED + optics = ⎜
⎟ ⎡⎣Φ (If , θ ja )⎤⎦ (Φ collected ) Toptics
⎝ ∆T a ⎠
(
)
∆Φ
− k Ta − 25 °C )
= e (
∆Ta
Where:
ΦLED
= useful luminous flux emitted by the
SuperFlux LED.
Φcat
= minimum luminous flux emitted per
SuperFlux LED emitter luminous flux cate
gory
TLED + optics = total luminous flux transmission losses
associated with the emitter as well as
collection and transmission losses for the
secondary optics.
Note: 0 ≤ TLED + optics ≤ 1
)
Where:
Φv realistic = realistic luminous flux requirement.
Φv spec
Tsignal
Φ LED = (Φ cat ) TLED +optics
⎞
⎟⎟ Fguard
⎠
)(1 − L
= optional photometric guardband.
Note: Fguard ≥ 1
The amount of useful luminous flux available from SuperFlux
LEDs may be less than that indicated by the luminous flux
categories. This is because the actual drive current may be
less than the test current used to initially categorize the
LEDs, and the system thermal resistance may also be higher
than the test conditions. SuperFlux LEDs are tested at 70
mA with a system thermal resistance, Rθja, of 200 ºC/W.
With a higher thermal resistance, some luminous flux will be
lost due to selfheating. Furthermore, most applications
cannot be driven at 70 mA due to the requirements for oper
ation over a range of ignition voltages and at elevated
ambient temperatures. In addition, the secondary optics may
not collect all of the luminous flux generated by the
SuperFlux LEDs. The secondary optics can have transmis
sion losses as well as limitations on collecting luminous flux
at wider offaxis angles. The following equations can be used
to estimate how much useful luminous flux will be emitted by
the SuperFlux LEDs and collected by the secondary optics
as compared to the published luminous flux category limits:
There are several causes for wasted luminous flux associated
with the outer lens. For example, the radiation pattern
achieved may exceed the minimum luminous intensity values
at some of the points. Or perhaps, the luminous intensity is
greater than zero at points outside the specified range of
angles. Furthermore, the luminous flux values given in Tables
1.3 and 1.4 do not include transmission losses of the outer
lens and transmission losses of the glass window (for a
behindtheglass CHMSL). The optical transmission through
a glass window can be as high as 93%. However, if the rake
angle of the rear window is small, then the Fresnel losses
can be significantly higher. For example, for a rake angle of
20°, the overall transmission through the rear window is
about 65%. Additional transmission losses would occur for a
tinted window. The combined effect of these losses could
result in the minimum lumious flux requirement of a behind
theglass CHMSL being twice the luminous flux requirement
of an exteriormounted CHMSL. In addition, the car manu
facturer may require a guardband of the minimum luminous
intensity values at each angular test point beyond that which
is required to meet the government specification. For these
reasons, the luminous flux needed from the light source is
somewhat higher than the values given in Tables 1.3 and
1.4. The following equations can be used to estimate more
realistic minimum luminous flux values:
⎛Φ
Φ V realistic = ⎜ V spec
⎜ T
⎝ signal
Fguard
= minimum luminous flux requirement per
Tables 1.3 or 1.4
SuperFlux LEDs in Automotive Application Brief AB201 (5/04)
11
∆Φ/ ∆Ta
= reduction in luminous flux if specification
must be met at elevated temperature.
Φ(If , θja)
= normalized luminous flux versus forward
current and thermal resistance per Figure
3 of the SuperFlux LED Data Sheet.
Φcollected = percentage of luminous flux collected by
secondary optics based on maximum
collection angle of the secondary optics
and Figure 6 of the SuperFlux LED Data
Sheet.
Toptics
= optical transmission of secondary optics.
k
= temperature coefficient: k = 0.00952
for HPWxxH00 SuperFlux LEDs and
0.0111 for HPWAxL00 SuperFlux LEDs.
See AB203 and AB204 for more infor
mation.
Thus, the number of LEDs, N, needed to generate sufficient
luminous flux required to meet the required photometric
lighting specification is equal to:
⎛ Φ v realistic
N=⎜
⎝ ΦLED
⎞ ⎛ Φ v spec
⎟=⎜
⎠ ⎝ Φ cat
F guard
⎞⎛
⎟⎜
⎠ ⎜⎝ T signal T LED + optics
(
)(
⎞
⎟
⎟
⎠
)
The approximate numbers of SuperFlux LEDs needed to
meet the SAE and ECE signal lamp requirements are shown
in Tables 1.5 and 1.6. These tables are based on the factor
shown below:
⎛
⎞
Fguard
4≤⎜
≤8
⎜ (Tsignal )(TLED + optics ) ⎟⎟
⎝
⎠
Note that for the assumptions used to estimate the number
of SuperFlux LEDs requires that the designer first complete
Steps 1 through 5 of the design process outlined in the
section Signal Lamp Design Process of this application note.
The calculation for the minimum number of SuperFlux LEDs
shown in the sidebar example titled Calculating the Minimum
Number of LEDs Required is Step 6 of this design process.
Once the minimum number of SuperFlux LEDs has been
established, it is possible to complete Step 7 of the design
process—evaluating the circuit topology of the LED signal
lamp.
SuperFlux LEDs in Automotive Application Brief AB201 (5/04)
12
collected. Finally, let’s assume that the optical transmission of
the secondary optics is 80%. Then the equations for
TLED+optics and (ΦLED/Φcat) are equal to:
Calculating the Minimum Number
of LEDs Required
Suppose that an LED Rear Stop/Turn signal lamp will be
constructed with 3.0 lumen (Category F) HPWTMH00 and
1.5 lumen (Category C) HPWTML00 SuperFlux LEDs. What
is the minimum number of LED emitters needed?
TLED+optics = (∆Φ/ ∆Ta)[Φ(If , θja)](Φcollected)(Toptics)
= (1.00)(0.56)(0.75)(0.80) = 0.34
The minimum luminous flux requirements shown in Table 1.3
are 9.4 lumens for the red Stop lamp and 15.1 lumens for
the amber Rear Turn Signal. Let’s suppose that the signal
lamp needs to operate at 55 ºC and has a system thermal
resistance of 500 ºC/W. Then, for the assumptions listed
below Tsignal and ( Φv realistic / Φv spec) are equal to:
Tfiller
= 0.9 (red)
Tfiller
= 0.8 (amber)
Tglass
= 1.00 (this application is not a behindthe
glass CHMSL).
Lpattern
= 0.3
Fguard
= 1.25
Tsignal
= (Tfiller) (Tglass) (1 Lpattern)
= (0.9 for red, 0.8 for amber)(1.00)(1 0.3)
Tsignal
= 0.63 for red, 0.56 for amber
Φ V realistic
ΦV
spec
⎛ Fguard
=⎜
⎜ Tsignal
⎝
ΦLED
= (TLED +optics ) = 0.34
Φ CAL
Thus, the minimum number of LED emitters needed for the
Stop lamp is equal to:
⎛ Φ V realistic
N=⎜
⎝ ΦLED
⎛ Φ V spec
=⎜
⎝ Φ cat
Fguard
⎞ ⎛ Φ V spec ⎞ ⎛
⎟⎜
⎟=⎜
⎠ ⎝ Φ cat ⎠ ⎜⎝ Tsignal TLED + optics
(
)(
⎞
⎟
⎟
⎠
)
⎞ ⎛ 2.0 ⎞
⎟⎜
⎟
⎠ ⎝ 0.34 ⎠
⎛ 9.4 ⎞
N=⎜
⎟ (5.9) = 19
⎝ 3.0 ⎠
Thus, the minimum number of LED emitters needed for the
amber Rear Turn signal is equal to:
⎛ Φ V realistic
N=⎜
⎝ ΦLED
⎞
⎟⎟
⎠
⎛ Φ V spec ⎞ ⎛ 2.2 ⎞
=⎜
⎟⎜
⎟
⎝ Φ cat ⎠ ⎝ 0.34 ⎠
⎛
⎞
1.25
=⎜
⎟
⎝ 0.63 for red, 0.56 for amber ⎠
⎛ 15.1⎞
N=⎜
⎟ (6.5) = 65
⎝ 1.5 ⎠
= 2.0 for red, 2.2 for amber
According to Figure 4b of the SuperFlux LED Data Sheet, the
maximum DC forward current at 55°C, 500°C/W is 50 mA.
Thus, Φ(If , θja) from Figure 3 of the SuperFlux LED Data
Sheet is equal to 0.56. Further, suppose that the signal lamp
needs to meet the SAE J1889 requirement for a 30minute
warmup prior to taking photometric values. Since Figure 3
of the SuperFlux LED Data Sheet represents the luminous
flux after thermal equilibrium, the 30minute warmup effects
are included in the 0.56 factor. If the signal lamp does not
need to meet photometrics at an elevated temperature, then
∆Φ/ ∆Ta is equal to 1.00. Finally, suppose the maximum off
axis angle collected by the secondary optics is 40º. Then,
from Figure 6a of the SuperFlux LED Data Sheet, 75% of the
total luminous flux emitted by the HPWTMH00 will be
SuperFlux LEDs in Automotive Application Brief AB201 (5/04)
Fguard
⎞ ⎛ Φ V spec ⎞ ⎛
⎟⎜
⎟=⎜
⎠ ⎝ Φ cat ⎠ ⎜⎝ Tsignal TLED + optics
13
(
)(
⎞
⎟
⎟
⎠
)
Table 1.5 Approximate number of SuperFlux LEDs for several SAE automotive signal lamps using assumptions
from this example.
LED P/N
Φcat, lm
Signal
SAE Amber
Front Turn
Φspec = 23.3 lm
Signal
SAE Amber
Rear Turn
Φspec = 15.1 lm
Signal
SAE Red
Rear Turn
Φspec = 9.5 lm
Signal
Signal
SAE Stop
Φspec = 9.4 lm
SAE CHMSL
Φspec = 3.1 lm
HLMPC100
≈ 0.375
100 to 200
100 to 200
36 to 72
HPWAM/DH
C, 1.5
26 to 52
26 to 52
9 to 18
D, 2.0
20 to 40
20 to 40
7 to 14
E, 2.5
16 to 32
16 to 32
5 to 10
F, 3.0
14 to 26
14 to 26
4 to 8
G, 3.5
12 to 24
12 to 24
4 to 8
H, 4.0
10 to 20
10 to 20
3 to 6
J, 5.0
8 to 16
8 to 16
3 to 6
HPWTM/DH
HLMPDL00
≈ 0.375
248 to 504
160 to 320
HPWAM/DL
A, 0.62
152 to 304
98 to 196
B, 1.0
96 to 192
60 to 120
C, 1.5
64 to 128
40 to 80
D, 2.0
48 to 96
30 to 60
E, 2.5
40 to 76
24 to 48
F, 3.0
32 to 64
20 to 40
HPWTM/DL
SuperFlux LEDs in Automotive Application Brief AB201 (5/04)
14
Table 1.6 Approximate number of SuperFlux LEDs for several SAE automotive signal lamps using assumptions
from this example.
LED P/N
Φcat, lm
Signal
ECE Cat 1
Front Turn
Φspec = 15.9 lm
Signal
ECE Cat 2a
Rear Turn
Φspec = 4.7 lm
Signal
ECE Cat S1
Stop
Φspec = 5.5 lm
Signal
ECE Rear
Fog
Φspec = 12.4 lm
Signal
ECE Cat S3
CHMSL
Φspec = 3.1 lm
HLMPC100
≈ 0.375
60 to 120
132 to 264
36 to 72
HPWAM/DH
C, 1.5
15 to 30
33 to 66
9 to 18
D, 2.0
12 to 24
25 to 50
7 to 14
E, 2.5
9 to 18
20 to 40
5 to 10
F, 3.0
8 to 16
17 to 34
4 to 8
G, 3.5
7 to 14
14 to 28
4 to 8
H, 4.0
6 to 12
13 to 26
3 to 6
J, 5.0
5 to 10
10 to 20
3 to 6
HPWTM/DH
HLMPDL00
≈ 0.375
170 to 340
50 to 100
HPWAM/DL
A, 0.62
104 to 208
30 to 60
B, 1.0
64 to 128
20 to 40
C, 1.5
42 to 84
14 to 28
D, 2.0
32 to 64
10 to 20
E, 2.5
26 to 52
8 to 16
F, 3.0
22 to 44
7 to 14
HPWTM/DL
References
G.B. Stringfellow and M. George Craford, High Brightness Light Emitting Diodes, Semiconductors and Semimetals, Volume 48,
(San Diego, CA: Academic Press, 1997).
SuperFlux LEDs in Automotive Application Brief AB201 (5/04)
15
Company Information
Lumileds is a worldclass supplier of Light Emitting Diodes (LEDs)
producing billions of LEDs annually. Lumileds is a fully integrated
supplier, producing core LED material in all three base colors (Red,
Green, Blue) and White. Lumileds has R&D development centers in
San Jose, California and Best, The Netherlands. Production capabili
ties in San Jose, California and Malaysia.
Lumileds may make process or materials
changes affecting the performance or
other characteristics of our products.
These products supplied after such
changes will continue to meet published
specifications, but may not be identical
to products supplied as samples or
under prior orders.
Lumileds is pioneering the highflux LED technology and bridging the
gap between solid state LED technology and the lighting world.
Lumileds is absolutely dedicated to bringing the best and brightest
LED technology to enable new applications and markets in the
lighting world.
www.luxeon.com
www.lumileds.com
For technical assistance or
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subject to change without notice.
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