From: "Da Man"
Subject: Re: Driving an LED from 9v battery
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Date: Thu, 21 Nov 2002 01:08:07 GMT
NNTP-Posting-Date: Wed, 20 Nov 2002 21:08:07 AST
Zetex has a fairly new high efficiency switchmode LED driver that should do
this, but I think it only handles about 8V max. It's in a small SMT package
and needs a inductor, resistor, and a transistor. It will also run down to
If that is acceptable and you have trouble finding it, let me know and I'll
look it up.
"Walter Harley" wrote in message
> I really appreciate all the help you folks have provided for me lately.
> Here's another question: I'd like to drive from one to four LED's, from a
> source with voltage as high as 12v and as low as 6v (basically, a 9v
> battery, occasionally supplemented by a poorly regulated wall-wart). I
> constant brightness (= constant current) over the whole voltage range, and
> want maximum possible efficiency, to preserve battery life. Need to keep
> the cost and parts count under control, need to keep the circuit
> small, and I need to keep audio-band noise low. The circuit will be
> incorporated into a variety of small battery-powered audio processors.
> I'm thinking that one of the many small switching converters or charge
> would be right. But hunting around on the web sites I can't seem to find
> which one: most seem to be oriented to stepping up from small voltages,
> rather than stepping down, and I'm not sure I'm searching with the right
> terminology. Can someone point me in the right direction? Or, perhaps
> there's a better solution to my problem?