can Zetex CCR drive Luxeon III @ 700ma properly?

[gpk]

Hello all, a few questions for you geniues out there:
Can Zetex CCR1/2 drive a Luxeon III @ 700ma properly?
What would I need/have to look out for?
Better inductor ? Better transistor than the 617?
Will I run into problem if I make RSense too small?
Or am I betetr off w/ a step down cicruit entirely...

Thanks in advance, gpk
EDIT:
P.S. Can the Zetex 5179 be used as a good replacement for the 617 ?
http://www.zetex.com/3.0/pdf/fmmt5179.pdf

http://www.zetex.com/3.0/pdf/fmmt617.pdf

 

[pbarrette]

Hi gpk,

In my opinion, the ZXSC300 circuit is a good one for driving a Lux-I with ~1.5-3.0V input in situations requiring a small circuit size.

Personally, I think if you want to push 700mA to a Lux-III, then you should start looking at other options.

Before you decide on a circuit or go starting to hunt one down, though, you need to make a few more decisions. One of the first is what power source you will be using. While the Zetex IC can be used to build a step-down convertor as well, there are other IC's that are better for this operation since they were designed with that purpose in mind.

The other decision you need to make is the physical host of the light. If you are putting the Lux in a 2-3D Mag, for example, then you have plenty of room for the circuit and don't need to worry as much about size constraints. If you are working in an Infinity Ultra, or an ArcAA, then circuit size becomes extremely important.

Andrewwynn (sp?), for example, is building a Peak-AAA mod that uses a AAA sized Li-Ion cell and a simple yet efficient step-down circuit to power a Lux-III. His mod is designed to underdrive the Lux for safety, but in experimentation I believe that he has pushed >1A in that tiny package.

So you should probably first decide what you are going to use to power the light and what "package" the light will be in. Then you can start looking for the best driver circuit for your needs.

pb

 

[gpk]

I was afraid you were gonnna say that /ubbthreads/images/graemlins/smile.gif
I have un unnatural fascination w/ the zetex CCR and 2 cell step up circuits in general (Mind you I'll have nightmares about those 617 transistors till i die!)
I'm using it in a 2D Mag for now so you're right I have a bit for room for larger circuits; I have some LM317s lying around and some low dropout 5V regulators. I've been using a 4AA battery pack for now for my simple tests/circuits. But 4AA NIMHs V -Lux VF > than the LM317 dropout; the LDO regulator seems to stabilize the ouput @ 4.85 which I've been using with a simple resistor for now. Been thinking of buying (or bulding) D to 3 xAA holders.
As always, thanks for your help /ubbthreads/images/graemlins/smile.gif

gpk

Back to scouring the forums for a good step down circuit...

 

[evan9162]

gpk

You can look into building a LDO linear regulator based of an LM334, an opamp, or the two-transistor one designed by Mr. Al. All 3 of those types have a dropout of about 0.1V or less, meaning they will regulate down to Vf + 0.1V

 

[andrewwynn]

The FET i use in the nano mods is rated like 4.2A... it's a heck of a chip.. 0.045ohm.. it's effectively a piece of wire when it's full-on. typically the 'max' current it will regulate is in the 600-700 mA range with the .1 Rsense, but i've built models with two parallel Rsense to get .05.. that basically gives me a .1ohm total ckt resistance.. means voltage drop of 70mV for 700mA current. It'd would be basically impossible to have a simpler ckt if you have the right battery/lux combination.

Efficiency in the setup i'm using averages right about 93-95%.. the 'underdriving' is the battery limitation.. the exact ckt used with an R123 i can crank up to 1100mA no problemo.. (well it won't stay in regulation long).. so.. i set it to about 830mA so i get a true 3W output.. i posted pics on http://rouse.com/flash (click on the CNC123 link)... i've been trying to get up to 2A in parallel but my battery will only output about 1600-1800 into the luxs i have.... Vf limitations.. the battery can output 7+A.... in other words.. i can output 700+mA into TWO parallel lux 3s with the LDO from a single LiON bat.

From a single LiON battery.. (or dual parallel)... you'd be hard pressed to find a more efficient solution than the 'mr al' ldo with the tweak i came up with.. 4 total components... each about the size of a gnat... it's a little tricky to wire the dual NPN but its worth it.

pictures of the driver are here: http://rouse.com/nano

-awr

 

[gpk]

Food for thought thx, and Happy B-Day Andrew!