luxeon regulator circuit

turbodog · May 17, 2004

Are there any circuits that will regulate a luxeon in constant current mode. Here's the catch, I'm looking for something that will go in series with the batteries and led.

Variable input/etc gets extra points.

My dream part would be constant current of about .6 amps, input variable from 2 cells to about 6 cells.

gwbaltzell · May 17, 2004

While I think this can be done, I think the minimum would be 3 cells and efficiency will go in the /ubbthreads/images/graemlins/smoker5.gif with more than 4 cells.
It might be possible to make a buck regulator to wire in series, but again a 3 cell minimum. I don't see any way to do a boost circuit without having a third connection! Even with 3 cells you'd have to have a low Vf Luxeon and tolerate not fully dischaging the cells (as would be typical of incandescant flashlights).

Doug Owen · May 17, 2004

As GWB just said, for what you want the battery has to be higher than Vf. There are a few two terminal circuits that will do this, but you'll need nearly a full volt more than Vf for any I know of.

Doug Owen

turbodog · May 17, 2004

ok, so much for that idea

Neg2LED · May 18, 2004

maybe a Boost/Down circuit like the Wizard?it can be wired in series, just as long as the barrel of the lite isnt negative terminal!

gwbaltzell · May 18, 2004

[ QUOTE ]
Neg2LED said:
maybe a Boost/Down circuit like the Wizard?it can be wired in series, just as long as the barrel of the lite isnt negative terminal!

[/ QUOTE ]
Does not meet the request! This is 4 terminals! Request was for something to be wired in series with a Luxeon and the battery only. No full connection to the battery.

The circuit I had in mind works to about 0.13 V above Vf but not at 600 mA. The output transistor is only a 2N3906 (rated 200 mA max.) It might be possible to use a transistor that could handle a higher current but the minimum voltage will likely also increase. The circuit comes from Bob Pease the designer of the LM317 and uses the LM334, the 2N3906 and a 1.6 ohm resistor (for 40 mA).

edit:
Oops sorry, just realized that wired as a two terminal this circuit would require 1.4 V above Vf to regulate! Still better than a LM317 at 3.4 V above.