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Old October 17th 05, 02:23 AM
Steven Swift
 
Posts: n/a
Default Pulsing LEDs for higher efficiency

Wim Lewis writes:

On the other hand, I also found some articles on pulsed LEDs saying
the opposite --- that the percieved brightness of a pulsed source
is closer to the peak brightness than to the average brightness.
It might be worthwhile tracking down some actual experimental data,
or doing an experiment yourself...


--
Wim Lewis , Seattle, WA, USA. PGP keyID 27F772C1


HP used to have a nice app note on this. The main trick is that the eye
responds most nearly to intensity, which is close to being proportional
to the square of the brightness (analogous to power vs voltage). Just
like "pulsey" currents have higher RMS values, "pulsey" light can have
a higher intensity. The eye acts as a smoothing filter. This is a well
known trick in lots of lighting and display areas. If you really care,
you can use LEDs as "catch" diodes in switching regulator circuits to
get some pretty amazing "lumens per watt."

Steve.
--
Steven D. Swift, , http://www.novatech-instr.com
NOVATECH INSTRUMENTS, INC. P.O. Box 55997
206.301.8986, fax 206.363.4367 Seattle, Washington 98155 USA