AN1149-3A Lumileds Lighting, LLC, AN1149-3A Datasheet - Page 3

• Manufacturer Part Number: AN1149-3A
• Description: Advanced Electrical Design Models
• Manufacturer: Lumileds Lighting, LLC

Figure 3.1A. Diode Equation Forward Voltage Model
for LED Emitter (Semi-Log Scale).
Figure 3.2A shows how the diode equation
model compares to the forward current versus
forward voltage curve shown in AB20 3,
Figure 3.8.
Figure 3.2A. Diode Equation Forward Voltage Model
for HPWA-xHOO LED Emitter Shown in Figure 3.8
(Semi-Log Scale).
Using the values of the nominal forward voltage
at the three test currents in Equations #3.3A,
#3.4A, and #3.5A would generate the typical
diode equation forward voltage model.
(I
F1
, V
(n
F1 nom
nom
, I
), (I
O nom
F2
, V
, R
F2 nom
′
S nom
), (I
)
F3
, V
F3 nom
)
⇒
3
Figure 3.3A. Worst-Case Diode Equation Forward
Voltage Models for LED Emitters. Note Graph Shows
Forward Voltage Variations for LED Emitters from a
Single Forward Voltage Category, Tested at I
mA.
Since there is little correlation between the
forward voltages at each test condition, there
are eight possible worst case permutations of
forward voltage at the three test currents. As
shown in Figure 3.3A, these eight combinations
of forward voltage can be used with Equations
#3.3A, #3.4A, and #3.5A to generate eight
different diode equation forward voltage models
(n, I
O
(I
(I
(I
(I
(I
, and R
F1
F1
F1
F1
F1
, V
, V
, V
, V
, V
(n
(n
(n
(n
(n
F1 min
F1 min
F1 min
F1 min
F1 max
LLL
LLH
LHL
LHH
HLL
′
S
, I
):
), (I
), (I
, I
), (I
, I
), (I
, I
, I
), (I
O LLL
O LLH
O LHL
O HLL
O LHH
F2
F2
F2
F2
F2
, V
, V
, V
, V
, V
, R
, R
, R
, R
, R
F2 min
F2 min
F2 max
F2 max
F2 min
′
′
′
′
S LLL
′
S LLH
S LHL
S HLL
S LHH
), (I
), (I
), (I
), (I
), (I
)
)
)
)
)
F3
F3
F3
F3
F3
, V
, V
, V
, V
, V
F3 min
F3 max
F3 min
F3 max
F3 min
) ⇒
)
)
)
)
⇒
⇒
⇒
⇒
F
= 70