> My goal is to be able to flash an LED string for a short duration at a
> higher brightness than its constant brightness. The idea is similar to
> a camera photo flash. The actual burst of light needs to be 1/60s
> (0.0167s), and the repeat rate won't be faster than 1/8s (0.125s).

If LEDs are being operated at about their rate value then what you
propose will significantly decrease their lifetime BUT this is likely
to be acceptable in many cases.

What brand LEDs (and part number?),
=A0What diameter. What current rating. ?

Time constant of R & C is t =3D RC.
Cap will charge to about 60% in that time then =A0to about 80% in
another time constant etc.
So 2 or 3 tcs is enough for "full" charge.

Energy in Cap is 0.5 x C x V^2.
Usual energy =3D V x I x t Joule or VI Joule per second.
So cap energy and steady energy into whole string can be compared.

Using cap on top of supply will double supply in a burst. Current peak
will rise to >> usual current so adding a new series limiting resistor
of=A0> Rexisting to >> R existing is wise.

"Ideal is to increase Vin in a steady step for as little as acceptable
for as little time as is acceptable for result.
Minimising Vin minimises I peak. Modern white LEDs do not like high I
peak and are much affected by short high I compared to lower longer
Ipulse.
As above re lifetime probably being OK.

Camera flash LEDS have very very very short lifetimes by most standards.

Sufficient unto a boost converters specifications are the performance there=
of.
this varies widely by design and can be designed as required.



=A0=A0 =A0 =A0 =A0Russell

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