I know a guy who just built an LED light fixture. It consists of nothing more than a single off the shelf adjustable current/voltage supply and three strings of LEDs connected in parallel.
He turned it on and it seems to work, but I would have thought the voltage drop in the individual strings might vary enough that one string would take the bulk of the current. And if one LED should open, the current in the remaining strings would go up 50% until the whole thing went dark.
Is that an acceptable practice for driving LEDs? Or is he likely to have problems in the long run? (They're all on a single large heatsink)