Is there a LED driver that would work with USB port?

Hi Guys,

I have a portable battery pack 5v 4800ma with a USB port output.

I wanted to use it as a battery for a LED lantern/light.

I was thinking of a 1 to 3W LED 100 to 250 lumens.

I was considering a buckbuck, but its lowest input voltage is 5v so when the battery discharges It would stop working.

Do I even need a driver in such a configuration maybe a resistor would be sufficient?

If anyone knows a suiting driver please post.

Thank you.

Yeah, lots of options.

7135 based drivers will work, although less efficient at 5v. Keep it at max 7135*3, which will result in 1050mA, which will be the max for most external usb packs. There sure will be some buck driver options, try to find the type that switches over to direct drive when Vout is higher than Vin. They will take lower input voltages. If you want to be able to use this light on regular usb ports, then you are limited to 500mA input max.

pentiger said:

. . . .. . Do I even need a driver in such a configuration maybe a resistor would be sufficient? . . . .

Click to expand...

In this case you will have 3.5 v across the LED and 1.5 volt across the resistor - 30% of the power lost as heat.

The buckpuck works just fine, peak efficiency at 95% at 5V too.
I've been operating a 3021-D-N-700 off USB for awhile now, there has been no problems...but then again I'm running it off a 5V 700ma supply.

With a CREE XPG,
(Output)(Qty) = (Efficiency)(Input)
(3.1)(0.7)(1) = (0.95)(5)(Iin), Iin = 0.4568A, or approximately 460ma.
USB current maxes out at 500ma, so assuming there are no peripherals on your computer it is likely it will operate on it with no problems. an R5 bin cool white XPg gives off about 140 lumens at 350ma, the efficacy gain at 700ma is about 185%, or an output [bulb lumens] of approximately 260 lumens.

One of these: http://www.ledsupply.com/03021-d-n-700.php
(Wired version): http://www.ledsupply.com/03023-d-n-700.php
driving one of these: http://www.ledsupply.com/creexpg-w139.php
and its happy hour.

Note: if you want a dimming option, get a 3021 [or 3023] D-E-700 driver