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Figure 8: Measured (dots) and simulated (full line) IVcharacteristic
of blue light emitting LED at different light levels
of ambient light.
of the emitted light. Therefore we could take approximate
values for the minimum energy gap EG for the
simulation. Results are given in figure 7 showing the
correct behavior. Only in the low IV region differences
between measured and simulated curves are
observed. More detailed temperature analysis will be
possible with manufacturer data on the material composition
of the LED’s.
C. Ambient light influence
LED’s are often utilized in environment with ambient
light. The pn junction of the LED with applied
voltage such that the LED emits light will also be
sensitive to ambient light. This means that the ambient
light produces some photocurrent in the pn junction of
the LED and the LED detects the ambient light [5].
This will influence the IV-characteristic in the region
of low IV values strongly. In figure 8 we show measured
and simulated data of the IV characteristic of the
blue light emitting diode under increasing ambient
light level. For the simulation of the generated photocurrent,
we introduced a current source in the circuit
(figure 9). The curves clearly show that our model still
holds for LED’s working under ambient light illumination.
V. SUMMARY
In the present work we have developed a general
model for high-power LED’s based on elementary
ideal electronic circuit elements. We have shown that
the model
• can be applied to LED’s of different type with
only minor model modifications,
• describes well the temperature behavior,
• is also suitable to characterize the LED under
ambient illumination.
ACKNOWLEDGEMENT
The authors thank the MPC group Baden – Württemberg
for financial support.
16
DC FORWARD MODEL OF HIGH-POWER LED’S
Figure 9: Electric circuit for simulation of LED with ambient
illumination.
REFERENCES
[1] E.F. Schubert, “Light-Emitting Diodes”, Cambridge University
Press, 2010.
[2] G. Massobrio and P. Antognetti, “Semiconductor Device
Modeling with Spice”, McGraw-Hill, 1998.
[3] S.M. Sze, “Physics of Semiconductor Devices”, John Wiley
& Sons, 1981.
[4] F. Sischka, “Diode Modeling”, Agilent Technologies, 2003.
[5] V. Lange, F. Lima and D. Kühlke, „Multicolor LED in Luminescence
Sensing Application”, Sensors and Actuators A
169, 2011, pp. 43-48.
Volker Lange received his diploma degree in
physics and his Ph.D. from the University of
Freiburg. Since 1991, he is a scientific
assistant at Furtwangen University, faculty
Computer and Electrical Engineering. His
scientific interests are semiconductor measurement
technology and optical sensor and
measurement technology.
Brenton Sherston studied Electrical and
Electronic Engineering at Murdoch University
in Perth. He majored in Electrical
Power and Industrial Computer Systems
Engineering. He performed his Bachelor of
Engineering Thesis at Furtwangen University
in Germany in 2012. He currently works
for First Quantum Minerals as an Electrical
Engineer in Zambia, where he is responsible
for the mining operations electrical power
grid.
Robert Hönl received his diploma degree in
Electrical Engineering and his Dr. Ing. from
University of Berlin. Until 1993 he was
product development manager at Krone
AG. Now, he is a professor at Furtwangen
University, faculty Computer and Electrical
Engineering. His scientific interests are
measurement-, sensor-, control engineering
and project management.