Step-down regulator?

[Tweel]

Hello,

I'd like to run two Luxeons in series from a fluctuating source that peaks at over 20 volts. Any ideas for an efficient step-down regulator?

--Paul

 

[georges80]

LM2674 is a decent switcher for 2 luxeons in series. That's what I use in my down converter board. It can run from up to 30V and down to about 8V with 2 Luxeons in series. It'll run down to about 4V to a single Luxeon (1W devices of course). To run 5W units you could use the pin compatible LM2675 - though the minimum input voltage would need to be 2xVf+1V Both are reasonable inexpensive - for a few prototypes you can get samples from National online. Digikey sells them online.
www.geocities.com/george_tlc/led.html for some pictures of what my finished board looks like.
cheers,
george.

 

[Tweel]

Thanks, George :-)

--Paul

 

[Rothrandir]

holy crap! that is some crazy stuff on your site goerge.

 

[georges80]

Originally posted by Rothrandir:
holy crap! that is some crazy stuff on your site goerge.

<font size="2" face="Verdana, Arial">Yeah, not just a LED nerd - also a 4wd nerd too, throw in a welder and other boy toys and I can do some serious damage

Hmm, just got a minilathe - another thought - a couple of Luxeons on stalks to light the workpiece - ahhh another project....

Of course getting a kitchen pass is sometimes a little tough - my wife's typical response ->

cheers,
george.

 

[radellaf]

I had been looking at the MAX1627 but doing a search I found your posts...and what looks like a much better circuit. Perfect for the 4D/3 watt LED torch I'm thinking about, maybe from the rubber Sears one...though it would be so much easier to tack it on to something like a 4D mag & Inretech mod since I'd like to minimize mechanical/heatsink hassles.

Think that board could really run 1A with the 5W chip, or would one need a board per 1W LED? A 5W LED and 4 cells would need another circuit entirely.

 

[Rothrandir]

let me know about those stalks...i just got a mini-lathe also.

actually, it shipped out on the 28, and wants 12 business days to deliver! thats a lot...