[Robotgroup] [OT] Regulator for White LED

[Paul Atkinson]

Hi Doug,

Hadn't thought about budget since this is a prototype. I'm looking at a
Linear and a Maxim part. Both are ~10-pin surface mount parts with a few
discretes around them. I hadn't considered PWM since I don't have a
microprocessor in the circuit. Is there a way to do this without a micro?
OTOH a micro may be smaller that the 10-pin boost/buck current regulator...

The application is a battery powered LED light/magnifier. The problem is the
'cheap' resistor regulator burns/damages the LED with fresh batteries and
fades with voltage. Just trying to get more consistent light output with
less LED damage. It's part of a low-vision gadget for my dad.

Paul

On 4/20/07, Doug Evans <douglasee at worldnet.att.net> wrote:
>
> how about using PWM and an appropriate sized capacitor?
>
> what is the budget?
>
> -----Original Message-----
> From: robotgroup-bounces at puremagic.com
> [mailto:robotgroup-bounces at puremagic.com]On Behalf Of Paul Atkinson
> Sent: Wednesday, April 18, 2007 12:54 PM
> To: The Robot Group Mailing List
> Subject: [Robotgroup] [OT] Regulator for White LED
>
>
> I'm looking for ideas for regulating the current for some White LEDS.
> Seems
> like I've seen chips from Maxim that do this in the past, but I came up
> empty with a recent search.
>
> I'd like to use 3 AA batteries and be able to run down to 0.9V which
> should
> be do-able with a buck/boost design.
>
> Sorry if this is too technical, but any ideas are appreciated.
>
> Paul
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