high power driver?

does anyone have a good 4 to 5 amp, 12 to 24 volt DC step down driver circuit?
i don't find many for this much power. would it be better to run multiple lower power drivers?
is it ok to run a driver at it's max rated output current?
thanks

Try Taskled.com

i want to run 2 strings with up to 2A to each string. also need up to 40v input. didn't see anything but the boost circuit that was close and it was only 3200mA. maybe i don't know enough to recognize one that would work?

Oh, you said 12-24V. H6CC or h6Flex would have handled that. at 40V input, only the HyperBuck would handle the voltage, and it's only 3.2A. You could use two of them.

The 40V input is going to be a challenge.

found several 3A similar to the pam2861 i'm using. i'd like to stay with these simple low parts count circuits.
might try this one at 3A first to see if it's bright enough.
allegro 6211
if it's not bright enough, guess i'll run 2 pam2863.
the TI LM3409 looks like what i need but all the calculations are way over my head. i tried to use the webench but couldn't get it to work.
for the white LEDs, i need more guidance. i'm thinking about cree XP-G3. they're supposed to produce up to 190lumen/watt. are these my best choice or should i look at some of the larger 5x5 or 7x7 LEDs?
thanks