Thanks for the input guys. Im still in the learning process. I am wanting to build an off road light for my truck, ten x-ml's running at 2.8-3 amps each. I'm thinking about what BLASTERMAN said about running ten buck drivers, but I cant seem to find any that fit my specs. 12v input, 3.3v 2.8A output.
"Codiak" I was thinking of that too, but like I said, Im new to this and didnt want to sound dumb. But, again, I cant seem to find a driver for these specs either. 12v input, 10v 8A output. Is there someone on CPF that could make this for me?
The reason you are having trouble finding your power supply is because that is not how power supplies (PS) are normally specified. The large majority (95%+) of PS are voltage regulated, and on each output voltage (fixed or variable) the manufacturer specifies a range of supported output current values, thus the PS is "guaranteed" to maintain the output voltage constant while the current or "load" varies in the specified range. For example, one of my bench power supplies has two adjustable outputs:
1) 0-6 volts, up to 5 Amps
2) 0-25 volts, up to 1 Amp
Now, for LED's, such as in your project, these power supplies are nearly useless to maintain the drive current level (and therefore output in lumens) that you are after. Since each and every one of those LED's (even from the same bin) will have slightly different value for vf, you really have to use a current-regulated PS, which we simply refer to here in the forums as an LED Current Driver, or just LED Driver.
In your particular case, if your voltage supply is for a car, then if you are getting power from the regulated side, you will get a fairly good 12 volts or so, but if you are getting it from the battery side, then your voltage range will be higher when the engine is running, closer to 14 volts (since the alternator needs a higher voltage for re-charging the car battery). Of course if the engine is not running, then you are back to having 12 volts or so, but being conservative in the design, the actual range that your LED drivers can see will be from something like 12 volts, to about 14 volts.
You now have two more options: do you use a buck design, or a boost design for the LED Driver. The buck design is used when the added "nominal" vf's of the LED's at the current you will drive them is less than the input voltage to the LED Driver. The boost design is needed when the added "nominal" vf's of the LED's at the current you will drive them is more than the input voltage to the LED Driver.
In your case, since you have so many LED's, you can go either way. For example:
- assume the vf for each LED at 2.8-3 Amps is about 3.65 volts.
- 3x of these LED's in series would have a voltage approximately less than the input to your power supply = 10.95 volts.
=> In this case you could use a buck LED Driver, that can take 12-14 volts in the input (nominally 12 volts) and drive your 3x LED's at your 2.8-3 amps.
You said you wanted to run 10 LED's, but with this model I would recommend driving 3x LED's per LED driver, and have 2x more additional LED drivers, each one driving 3x LED's, to give you the 9x LED's, properly driven from 3x LED drivers.
Now, lets assume that you want to run all of your LED's in series. If we again assume the vf of about 3.65 volts, and you have 10 LED's, then you need an LED driver that can take 11-14 volts on the input, and that has the ability to "boost" the output voltage in the 37-38 volt range at the output. Here you would need a boost type LED driver.
Now that you have two possible options to properly drive the LED's, you need to find out what LED drivers could do what you need.
From my own personal experience, I mostly use LED drivers from TaskLED.com. George, owner/designer, has a simple comparison table showing you some of the possible ways can drive various LED loads:
http://taskled.com/compare.html
From that table you can see that the Hyperboost "can" start with a voltage as low as 8 volts, and output a voltage as high as 50/80 volts (depending on the model), but unfortunately only with a regulated current of 1.5Amps. Not enough for your needs.
Now, if we look again at that table, you can see that the H6CC, which is a buck LED driver, "can" drive the 3x LED's in series, and could supply up to 6.7Amps - of course when you buy it from George, you just ask him to set them up for 3.0 amps, so no problem.
So in summary, for your case, I would recommend 3x H6CC LED drivers set to 3.0amps, to drive 3x LED's. Then do this 2x more times for a total of 9x LED's (or 3x more times, if you want 12 LED's). Of course, you better have "enough" of a heatsink for your LED's, given the expected ambient temperature, etc., since as the LED's heatup from 25C, their rated output drops, and their lifespan shortens quickly.
If you choose drivers from TaskLED, before you purchase the, go ahead and contact George by email, so that you both can review the particular scenario - George will give you good advice as to what is reasonable or not.
Good luck,
Will
Thanks
