Heat dissipating circuit for hi-brightness LEDs

Hi there,

For a little art project I have to individually control a couple of CREE Q5 high-brightness LEDs with DMX. You can run them between 700-1000mA and therefore the LEDs have to be heat-sinked. If I run them at 12VDC and use a current limiting resistor it has to be a pretty big resistor Wattage wise and heat-sinked as well. New flashlights use the same LED with a step-up converter so you can run the flashlight even from a single 1.5V battery. I could just use the driver circuit from a flashlight and then DMX-control the brightness via an external DMX driver circuit. I tested this and it works flawlessly. I’ve been told, though that those step-up converters don’t really like external input from DMX drivers. As mentioned before it works but might not work for long… In order to avoid those big heatsinks that might even need a cooling fan I was wondering if there is another current limiting circuit out there that would dissipate all the heat generated without a heatsink and can handle external input from a DMX driver? Another option would be a current limiting / heat dissipating AND DMX driver combo circuit that directly accepts DMX data input. This is for a super-low budget project so price is key… Any ideas?

Thanks for your help in advance,


Look for a constant current buck converter specially for LEDs, choose one with PWM input? But that need inductor etc so may not be the cheapest.

Buck convert 12V rail down to 5V with a DC-DC converter, then use smaller series resistors and MOSFETs (or CAT4101's) for the PWM control?

Just a little update on the flashlight dimming project:

I got those 7W 300LM Mini CREE LED flashlights and I tested 2 different DMX controlled current limiting drivers from Shanghai EUChips Industrial – http://www.euchips.com PX704 – has 4 channels and you can set the current either to 350 or 700mA PX705 – has 3 channels and you can set the current to 300, 350, 500, 650 or 700mA EUChips has been extremely helpful and you can order directly with PayPal. Contact Ivy Chang at ivy@euchips.com if you need further information.