From Figure 3, HPWT-MH00 Data Sheet:
Luminous Flux Category
F
G
H
J
L
Minimum Luminous Flux
Desired “relative luminous flux”
Design Current, from Figure 3
3.0 lm
0.54
33.6 mA
3.5 lm
0.46
29 mA
4.0 lm
0.41
25 mA
5.0 lm
0.32
19 mA
6.0 lm
0.27
15 mA
Note: Due to the variations in forward voltage at
low currents, there is a practical limit to the use
of higher and higher luminous flux categories at
correspondingly lower dc drive currents. For the
series string circuit shown in Figure 3.1a, at
drive currents less than 20 mA, the “worst-
case” ratio of forward currents between two
strings of LED emitters can vary by over 2:1. As
shown by this example, in order to achieve the
same light output for all CHMSL arrays, designs
using HPWT-MH00 emitters from luminous flux
categories J and L would require drive currents
less than 20 mA. Thus, the designer needs to
establish whether it is better to limit the forward
current to 20 mA and allow the light output to
increase for these brighter luminous flux
categories, or to accept possible visible light
output mismatch within the array.
7. Determine values of R for expected luminous
flux and forward voltage categories:
Values of R can be determined (using Equation
#3.2) for each SuperFlux LED emitter forward
voltage category and luminous flux category at
the appropriate design current as calculated in
Step 6.
Note: Since the design current of the HPWT-
MH00 LED array is less than 32 mA for designs
using luminous flux bins G through K, a “low
current” linear forward voltage model (8 mA £ IF
£?32 mA) was used. This model is shown below:
HPWT-
MHOO
Voltage
Category 2
Voltage
Category 3
Voltage
Category 4
Voltage
Category 5
Voltage
Category 6
VO
RS
=
=
1.80 V
10.4 ohm
1.83 V
11.7 ohm
1.85 V
13.2 ohm
1.88 V
14.3 ohm
1.94 V
15.1 ohm
NOM
NOM
For VIN DES = 12.8 V, VD = 0.8 V, IF DES from Step 6, VO NOM, RS NOM, x = 1, y = 4:
HPWT-
MHOO
Design
Current
Voltage
Category 2
Voltage
Category 3
Voltage
Voltage
Voltage
Category 4 Category 5 Category 6
Flux, F
Flux, G
Flux, H
Flux, J
Flux, K
33.6 mA
29 mA
102 ohm
124 ohm
151 ohm
212 ohm
279 ohm
93 ohm
115 ohm
140 ohm
199 ohm
265 ohm
84 ohm
106 ohm
131 ohm
189 ohm
253 ohm
77 ohm
97 ohm
122 ohm
179 ohm
242 ohm
66 ohm
86 ohm
109 ohm
162 ohm
222 ohm
25 mA
19 mA[1]
15 mA[1]
Note 1: Operation at dc drive currents below 20 mA can cause noticeable light output differences within
the LED array.
26
LUMILEDS [ LUMILEDS LIGHTING COMPANY ]
