Harold M Hallikainen wrote:
>
>      I've got an application where we need to drive a high power LED.
> It's rated at 700mA at about 6.5V, but with adequate heat sinking, it's
> been run up to about 2A with 7V across it.
>         Any thoughts on using the PIC (which will also be in the circuit) for
> regulating the LED current? Since the LED can float, I could put a small
> current sense resistor between the bottom of the LED and ground and
> perhaps have an analog input on the PIC sense the current.
>         Any ideas out there? What'd be the simplest way to get a regulated 2A
> through a 7V LED from a 3.7V battery?


Hi Harold, does your PIC have a comparator?
You could set the comparator vref to the low
setting of 0.2v I think, and use a current sense
resistor of 0.1 ohms. Then a simple boost
converter consisting of one mosfet/inductor/diode
and the PIC controlling duty cycle.

Having the luxury of a PIC brain and nice square
wave output to drive the fet you should be able to
get it efficient with the minimum of parts. :o)
-Roman

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.