Driving a 500W LED Panel - High voltage, constant current, buck, capable of 7A?

Meatball said:

Hey look what I found for you. I think it would work very well - it even has an adjustable current limit up to 10A!

DC DC 600W 10 60V to 12 80V Boost Converter Step Up Module Power Supply | eBay

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That is essentially perfect! Thanks!

Things said:

Hope you've got a portable swimming pool to cool that thing, those LED arrays are ungodly inefficient when it comes to LED technology 70W in the driver will be the last of your worries.

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I have heard that they effectively use technology on par with the generic LEDs that are known simply as 3W, 1W, etc. The panels just stick lots of them together.

Think you'll find it'll be around 80lm/W or so at best. Not too horrible, but not too great when you have to dissipate the rest of it

Did you buy it? Would live to see a review

Mohrenberg said:

Did you buy it? Would live to see a review

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Not yet. The comments re efficiency got me thinking about the economics (both monetary and lumenary) of going with this panel, vs a ridiculous number of XMLs.

It's actually a legitimate consideration. At the $225 price tag for that panel, I could instead cover the cost of:

- 50x XML Emitters
- Custom aluminum PCB

I would have the flexibility to configure the LEDs in parallel/series to fit my driver, instead of vice versa. The hold up (other than that I'm slower moving these days on account of having a whole lot less hobby time) is:

- Finding the hobbyist PCB fab that does aluminum PCBs. One of them does, I've come across them before, but I'm having trouble finding them again.
- Finishing all the comparison calculations to make sure this makes sense (within the limits of course, of this project not really making "sense" to being with! )

How does it not make sense? I would totally love to have a backpack powered 50k lumen light panel I could flash on when I wanted.

I think it's up there with Hemlock_mikes portable co2 laser rifle

You're right. I totally agree. What I meant to say was "It doesn't make sense to normal people"

50 (49...) xmls would be better IMO, I highly doubt the china led is even close to 100 lumens/watt

This is how I would do it:

Have a regular PCB made with 7 long holes cut out of it.
Get some copper strips to fill the holes
Tin the copper strips and pcb,
add the leds and reflow the whole thing
on the other end of the board add any driver circuitry you prefer

Something like this:



I would love to see something like this in action...

It should be possible to use a linear regulator to drive a bunch of pass transistors (2N3055's or something) like we did in the old days with large power supplies. This is the basic principle .

Here is my circuit:

(eagle brd and sch attached)

Its 25x50mm (~1x2 inch).
Vsense is 100mv, with current set by two 1206 resistors.
Depending on how many zeners you jumper it can use a Vin range of 3-30, 28-55, 53-80, or 78-105. Different voltages and currents will cause different part values to be needed. This calculator will help:
Switching Converter Power Supply Calculator
Its operating at 1mhz so Rhd you would need about 1uh inductor.

I got around the voltage limit by using zeners in front of the IC, and moving the sense resistors behind the load. I got around the switch current limit by using a small pchannel mosfet to repeat the signal and a big n-channel mosfet to handle the power (I'm about 90% sure this will work). The mosfet and diode are to-220 because they will have a lot of power going through them.

Ill test this soon. I have no idea if it will actually work as desired, so for now you should probably assume it has bugs. Usually the first try doesn't work perfectly and tweaks will have to be made.

I still need to do some small stuff on the board, like arranging component names and whatnot but the actual circuit is complete I have about all the components picked out on digikey. It should be a good general high power buck circuit. It even has soft start and easy access to the PWM pin.

I think you should go with 50 xml's over the 500W generic! My board should drive two strings of 25 from 4x 6s batteries.

I think I would use 6S lipo pack(s) (22.2V nominal) running into 10 separate buck drivers running strings of 5 series leds. I have a buck circuit that can handle the task, and isn't too expensive or hard to make / reflow.

However, aluminum PCB is non optional. Its a must.

There's a small batch PBC fab somewhere that does them, I just need to find them again.

I think you are looking for 4pcb or goldphoenix.

What are you going to do about focusing the leds? Use some small reflectors, or a bunch of lenses?

Okay - missed your circuit post when I made my reply.
Seeing that now, has me excited. I'm going to do this thing! And, I'm going to try and do it intelligently, with some thought put into cooling.

This will be my 2013 project. And let me forewarn, that it won't be fast moving So don't expect pretty build pictures for a while.

Ben, I've been really happy with these:
http://pages.ebay.com/motors/link/?nav=item.view&id=221181710013

XM-L2! :wave:

Is the XML2 available at a reasonable price (emitter only) anywhere?

Truth is, same footprint, so I'll just order the LEDs last and they'll probably be affordable by then.

Mouser has xml2