That's one of the problems with doing it that way. Here are the sims at high and low line. Slightly over the recommended at high line and about 1/2 power at low line. Probably not to satisfying. Throw in the variation in Vf that you would need to trim out. Add a guesstimate on the temperature of the led at high line.
The method works fine for small LEDs and regulated supplies because there can be a regulated supply and only a small variation in Vf. All those problems go away with constant current.
The method works fine for small LEDs and regulated supplies because there can be a regulated supply and only a small variation in Vf. All those problems go away with constant current.
Attachments
-
176.3 KB Views: 19
-
173.9 KB Views: 18