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From: "Nucharin W. Jansen"
Subject: Re: Wanted circuits to power white LED from 1 nicad/nimh cell
Date: Thu, 07 Nov 2002 04:49:08 +0700
Organization: C.S. Communications Co. Ltd.
NNTP-Posting-Date: Wed, 6 Nov 2002 21:49:12 +0000 (UTC)
To: Bob Wilson
X-Mailer: Mozilla 4.8 [en] (Windows NT 5.0; U)
You mean I can't parallel LEDs without resistor, right ?
Can I use 10 ohm for each strings/branch ?
Bob Wilson wrote:
> In article <3DC839EE.4A3F0D24@fanwap.com>, email@example.com says...
> >I using MAX757 adjust voltage to 3.5V voltage regulator.
> >I can get 22uH inductor 1/4w ( look like resistor but green color )
> >The capacitor can use electrolye and don't worry about voltage ribble.
> >The problem is white LEDs itself!
> >Their are not the same voltage drop.
> >I parallel it up to 6 LEDs. These IC support 300mA output.
> >No reason the build smallest flashlight.
> >These IC can run down to 0.7v to 3.5v
> >Hope these help.
> Unless the LEDs are forward voltage matched, paralelling them will not work,
> because they will not share the current. The one with the lowest
> forward voltage will hog most of the current. There is nothing special about
> white LEDs. They are simply ordinary Blue LEDs, with a yellow phosphor
> added. The blue light pumps the phosphor to emit yellow (the compliment of
> blue), and there is enough blue leaking out that the mixture of blue and
> yellow combune and look white to the eye.
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