Building a driver for absurdly high power LEDs

A few years ago, the highest power LEDs you could buy capped out around three watts. Now, LED manufacturers are taking things to ridiculous power ratings with 30, 40, and even 90 watt LEDs. Getting these high-power LEDs are no longer a problem, but powering them certainly is. [Thomas] built a LED driver capable of powering these gigantic LEDs and creating a light show that is probably bright enough to cause bit of eye damage.

[Thomas]‘ LED driver is based on Linear Technology’s LT3518 LED driver. This driver is part of a project to build a huge WiFi controlled RGB LED, so the driver has outputs for three separate LEDs capable of sourcing 700 mA each.

Because [Thomas] is dealing with crazy amounts of heat and power required to light up these huge LEDs, the driver board features a temperature sensor next to each LED driver. When the board gets too hot, the driver automatically shuts down, preventing bad things from happening.

You can check out a few pictures of [Thomas]‘ LED driver over on the build page for his WiFi LED project. A truly awesome amount of lighting power here, that also makes it impossible to get a good picture of the board in operation.

Comments

  1. hackcasual says:

    700ma, that’s cute.

    Been meaning to write this up: http://www.youtube.com/watch?v=kMKH_kqDPoI

    That’s 1.4A per channel

    • Please do write it up, I’d love to see a cheapish yet safe way to drive high-output RGB LEDs.

      • nes says:

        KIS-3R33S modules are available absurdly cheap from ebay sellers.

        They handle 3A and are happy being PWMed by their enable pins. They are strictly constant voltage rather than constant power and tend to smoke if you try to modify them at all, so you have to waste a little power in a ballast resistor. They’re still the simplest solution and better than a linear reg.

      • Chris C. says:

        @Nes: You can avoid the power-wasting ballast resistor. I’ve figured out how to easily turn these modules into constant-current LED drivers.

        Set the voltage to just above the maximum voltage you’ll need. Put a low-side sense resistor between the LED and ground. Use one of the four comparators from a LM339 to output active low when the voltage across that resistor rises above your desired threshold. Connect that output to the MP2307’s soft-start pin (or the external capacitor connected to it) through a 10k resistor. And you’re done.

        The soft-start voltage acts as a multiplier for the final output voltage. It rises linearly via the chip’s internal 6uA constant current source, up to a maximum of 0.985V. But if the current exceeds the threshold, the comparator adjusts the soft-start voltage (and thus the final output voltage) down, until the overcurrent condition no longer exists.

        I wouldn’t consider this a precision current source, as the actual current may oscillate a bit; but not enough to affect LED output or reliability. If for some other reason this oscillation is undesirable, it can be reduced by increasing the value of the 10k resistor, taking care to ensure the comparator can still pull the voltage low enough to maintain regulation.

        As a bonus, the remaining three comparators can be used for three more channels. ;)

  2. Polymath says:

    Does this mean we can finally stop paying $300 for projector bulbs?

  3. High Voltage mA! says:

    Hahahaha… “crazy amounts of heat and power”… “LEDs capable of sourcing 700 mA each.”

    Woah!

  4. calipsoii says:
  5. Faelenor says:

    I don’t get it. It’s a design for a not so powerful driver, obviously not able to power a 30-90W LED. With only 700 mA, it’ll be able to light strings of 3W LEDs, no more.

  6. ino says:

    “[Thomas] built a LED driver capable of powering these gigantic LEDs ”
    So we’re talking about less than 5W in power …. gigantic .. really?

  7. MaBl says:

    I’ve constantly been looking for an array of several of these high power LEDs in an industrial IP66 casing.

    I.e. like those Raytec lights:
    http://www.rayteccctv.com/products/category/raylux-white-light/0

    I just have the feeling this could be improved even more. Can anybody recommend industrial high power LEDs *in as casing*?

  8. Kyrk says:

    About a year ago I was part of a team building a 7kW array of LED heater for a vacuum chamber. Blue 300W LEDs with water cooling where used to heat some silicium(silicone) wafer. Infra is going trough silicium so the physic told us to use blue LED instead. Other machines where 10kW and above with special heating lamps. So it was realy a thing where energy could be spared.

    I was responsible for the SW which was implementing a PID controller and driver stages for the LED. Each LED could be controlled separately to compensate heat differences. Also some failsafes where implemented. Each LED water cooling temperature was measured and check if it is not too hot.

    We could measure the voltage and current of each LED array. First we tried to turn on each LED a little bit, then a bit more, and more. Then all LED togethet a little bit. Always checking how much of the LEDs got damaged in the array. Yes, some LEDs got damaged (ESD, or was already shipped damaged) but not the whole array. Finally after some week of redesigning we have got the permission to turn to full power. Playing with so much LEDs isnt cheap, so noboody wanted to do irreparable damages and extra work.
    So for the first time I removed the power limit from the SW and we pushed up the slide for maximum power. Then we reached 6,8kW, it was unbelivable. No explosion, no overheating just everything was blue. Temperatures where stable.

    Turning on so much LED was really funny, because everything was painted with blue. We had some glasses to check if the LEDs are OK, but I do not need to say that it was so hot like the sun in summer.

    On the silicium(silicon) 412 Celsius degree where measured. Full success.

    http://kyrk.villamvadasz.hu/tsmc/champer.jpg

  9. Galane says:

    I want to see some DIY for LED car headlight and projector / rear projection TV bulb replacement.

    I have a nice digital LCD projector and am dreading when the bulb dies. I know it’s possible to hack the thing to not need to detect the bulb lighting.

    Eliminating the high voltage to the bulb makes a projector use much less power.

  10. James Feeney says:

    I wonder what would happen if you took one of these super high power LEDs, and pulsed it with 100A for 1nS? Would it hold up? Could you use this LED flash lamp to pump a laser medium? Most of these hogh power LEDs take 700mA contimuiously. Now take that LED and hit it with 100A for 1 nS, what would the the light output flux on that? I bet it would be like a nuclear blast going off. Definitely wear eye protection.

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