LED Current and Driver Adjustment

Thread Starter


Joined Jan 20, 2014
Hello everyone, I am working on a project and wanted some input before proceeding further. These LED's I use are pricey, ordered from China, so waiting a month to get them in. I want to make sure I do it correctly, because I can't exactly run down to Radio Shack and buy more if I make a mistake.

Using this 100 watt LED: http://www.ebay.com/itm/100W-100Wat...825?pt=LH_DefaultDomain_0&hash=item257b74f2b1

Power Consumption:100w
  • Power Input: DC:30-34V
  • Color Temperature: Green(Wavelength 520-525nm)
  • Color Rendering Index: 45-65Ra
  • Luminous Flux: 7000-7500lm
  • FWD Voltage 3,500 mA

Using this 100 watt LED driver/converter: http://www.ebay.com/itm/271455842760?_trksid=p2060778.m1438.l2649&ssPageName=STRK:MEBIDX:IT

My power source is 12 volt lead acid, automotive battery. As this is a 12 volt application. A DC converter is a must.

QUESTION: The LED has an operating range of 30-34 volts, this achieves optimal light output. The driver has CC (Constant Current) and CV (Constant Voltage) adjustable potentiometer. When I set the voltage to 32 volts, to achieve highest luminous output the CC is thus increased to around 4,500 mA. By reaching the optimal voltage setting for the LED to perform, the current adjusts along with it. To keep the driver cool, I'm having to adjust the CC to 3.25 amps and this adjusts the voltage to 28 volts. Now it operates at a lower luminous intensity by 2-4 volts. I want to achieve 30-34 volt range, without overdriving the LED and driver.

Is this a problem? Am I overdriving the LED? The driver gets incredibly HOT to the touch when running like this for a while and the shell temperature increases close to threshold. I want to drive the LED, but I don't want to burn out the chip or the driver/converter.

Any input would be appreciated!


Joined Feb 12, 2009
All I can say is that nothing should be getting too hot. If anything is too hot to touch then you have problems. Try operating your DC-DC converter into a power resistor first and fully test before connecting your LED. A 10ohm 100W resistor would be ideal. Something like this. Fix it to a big aluminium plate for cooling.

The LED especially should have a large heatsink and should run fairly cool. 30 - 40 deg C maximum or the LED will have a short life.

I assume you know that the LED is a current - driven device. The power supply must control the current, not the voltage.


Joined Nov 12, 2008
Yes, you are over driving it. You want to limit the current to 3500 ma. Don't worry about the voltage as long as it is just high enough to get the 3500 ma..
The driver is running at it's maximum, so bolt it to some metal to keep it cool. Or use a small fan.

Thread Starter


Joined Jan 20, 2014
Thanks JDT and ronv...I adjusted the CC to 3,500 mA with load, and the CV , peaks at around 28 volts. It's not as bright as it could be. Certainly when I adjust the pots up to 32 volt...but it will most likely burn out or shorten the life of the LED.

Maybe I should go to a 150 watt or 200 watt LED chip. If I can find a DC driver/converter! :-o