Gerhard Hoffmann wrote:
On Wed, 09 Dec 2009 15:08:15 +1300, you wrote:
Another point is the LTSpice LED model isn't particularly accurate for
simulating the effects of temperature variations.
Does anyone knows of more accurate LTSpice compatible LED models?
The LED model voltage drop increases with temperature even at low
current, whilst the voltage drop across a real LED at low currents
decreases with temperature.
In practice the variation in the LED forward drop tracks the variation
in the pnp Vbe quite well.
I have used this model and also this diode:
* from OSRAM TOPLED library
*
*
.MODEL LH_T676_typ D
+ IS=5.5621E-24
+ N=1.3448
+ RS=4.3842
+ IKF=17.186E-3
Comparing the current with a BC860 PNP and a 15 Ohm emitter resistor
worked quite nicely, so I had no reason to investigate the model.
(as you wrote, too)
I also tried to operate a power LED with the base bias divider current
of all 6 distribution channels combined(70 mA tot.) to recycle the current
but it seemed that the power LED had more Ohmic resistance than
6 times LHT676. Could be just my sample, and it was close to the max. specs.
Gerhard
Gerhard
That LED model has the same problem (at least in LTSpice):
The LED forward drop increases (instead of decreasing as does the
forward voltage drop of a real LED) with temperature.
Its not a great issue as long as one is aware of the problem.
Bruce
_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
