There is a limit. You will find it in the data sheet of any LED, as the
absolute maximum current rating.
And you can't get anything like a camera flash out of a regular LED.
IIRR someone published a scheme - in Review Scientific Instruments -
for getting near-UV out of a blue LED by significantly exceeding the
absolute maximum current rating for about a microsecond, but the LED
died after 10^7 flashes, which is a total on time of ten seconds.
I have heard of this scheme, and I got the LED to last much longer - by
using current around 3/4 of an amp. I have yet to blow an LED after
running them like that for minutes. I suspect half an amp for a
microsecond with duty cycle of .5% will be fairly safe.
Also, this trick for getting UV out of a blue LED by pulsing with high
current only works well with GaN ones with peak wavelength (at 20 mA) 450
nm and spectral halfwidth that is wide (60-70 nm or whatever). These
included Nichia's NLPB series and similar Panasonic ones that may have had
the older Nichia dice. I got better results with the Panasonics -
possibly the epoxy was more UV-transparent. All of these LEDs were
obsoleted by 1997-1998 since InGaN ones were established.
I describe this and a circuit in:
http://www.misty.com/~don/ledbl.html, for which I have not made time for
updating in the past few years.
- Don Klipstein (
[email protected])