L
lists (at) lazygranch.com
Tue, Sep 18, 2012 4:39 PM
You really want to drive the LEDs with switcher designs typical in battery chargers, basically hysteretic current output. Prior to LIon batteries (which are voltage sensitive), the old nicad/NiMH chargers used the hysteretic scheme.
If you want a simpler switcher, you can take the garden variety voltage regulated switcher and hack it to be current regulated. LTC and Micrel sell chips for exactly that use.
Note that the really bright LEDs are designed for a 10 year life at those power levels. (Sadly, true for LED backlit TVs.)
I was at a trade show where CREE had a display. For "natural" lighthing, they mix some red LEDs in with the white LEDs. Uh, the dope growing LED fixtures do the same thing. ;-)
You really want to drive the LEDs with switcher designs typical in battery chargers, basically hysteretic current output. Prior to LIon batteries (which are voltage sensitive), the old nicad/NiMH chargers used the hysteretic scheme.
If you want a simpler switcher, you can take the garden variety voltage regulated switcher and hack it to be current regulated. LTC and Micrel sell chips for exactly that use.
Note that the really bright LEDs are designed for a 10 year life at those power levels. (Sadly, true for LED backlit TVs.)
I was at a trade show where CREE had a display. For "natural" lighthing, they mix some red LEDs in with the white LEDs. Uh, the dope growing LED fixtures do the same thing. ;-)
