This question implies two assumptions:
- The frequency of a switched LED driver is high enough that average power, not instantaneous power, should be used to determine maximum drive current.
- The limiting factor which determines maximum current at any duty cycle is average power dissipation.
After these assumptions, it is obvious that the current through an LED at maximum power dissipation is inversely related to the duty cycle.
Is the apparent brightness (not necessarily the luminosity) increased, decreased, or not affected by pulsing an LED at higher current and lower duty cycle?
I do not have any particular LEDs or driver topologies in mind, but would welcome references to real parts, datasheets, or appnotes. I would also be interested in knowing if this varies between low-power (say, 20mA) indicator LEDs and high-power, high-brightness lighting LEDs.