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From: Winfield Hill
Subject: Re: 12V computer fans run from 27 to 38V, speeding up at high temperature
Date: 22 Oct 2002 19:03:48 -0700
Organization: Rowland Institute
X-Newsreader: Direct Read News 2.98
> You could use a low-current 5V or 12V regulator for the temperature
> control IC, and use the PWM output to control a switching voltage
> regulator. Or you could use the PWM signal to directly chop the 3
> fans in series. Some fans do not work well when the voltage is
Thanks, that's right - I'm planning on a BFC to insure any fan will
work. BTW, I find it appealing to use standard uP heat-sink/fans.
WRT a 5 or 12V regulator, why add additional regulators if one can
do the job with one IC (along the lines of my circuit example)? I'm
looking for the most viable modest parts-count solution. Right now
I'm leaning towards an NSC LM2674 260kHz switcher IC with a say 220uH
inductor and a small thermistor-resistor network plus a zener diode.
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