After watching someone build a fairly wasteful project, I wondered if there was a better way. The LEDs are cheap chinese variety, with a forward voltage of around 34-36V @3A, and they throw off about 10,000 lumens. They used a SMPS, putting out 24V, and a cheap boost converter to get upto 36V. For each of 10 LEDs. I thought that was a pretty crappy way to drive 10 of these, an expensive at that.
The way I would do it, is with one large SMPS at a common and cheap voltage, like 24V, and step up the voltage to 360V and control the leds with current. Is this a practical approach? I see a lot of chips to control LEDs at 350mA, but not a lot for 3A. Are there design limitations I'm not considering? I've done some HV stuff, but it was just a plasma speaker.
Best Answer
So you want to make a 24V->360V controlled current SMPS that can supply more than 1kW? I don't think that's a very easy project to start with. At 24V you're going to be dealing with almost 50A of current. If it was an off-line switcher the currents would be lower, but a 1kW supply is still going to be a challenge.
You don't mention the topology you have in mind for the step-up, but I doubt a simple boost converter will be practical- you'll probably need a transformer-based forward converter or other high power topology. In which case you might as well do an off-line switcher.
If you really want to run the LEDs at 360V, there will be a serious lethal shock hazard- probably more than 400VDC at substantial current if the circuit is broken.
It might be practical to fool an off-the-shelf 100W 36V (nominal) supply into supplying constant current by diddling the trim input with an op-amp, but you'd need 10 of them. On the plus side, a single supply or LED failure won't take out the whole lot.
Or a fixed (say) 48V supply and 10 individual buck converters (which would only require inductors).
However this is done, to get constant current to 10 different LEDs with a total of more than 1kW power is not going to be really cheap or simple if its done properly.