Ripple filter
- From: "John Doe" <xxx@xxxxxxx>
- Date: Fri, 13 Jan 2006 07:09:00 GMT
I would like to use a brushless 12v (0.07a) computer fan to vent a small
area in my RV. I tried this, but the battery charger cooked the fan after a
while due to ripple- it could not handle the peak voltage I guess. I
replaced the fan but placed a 2 ohm (5w) resistor in series with it, and a
0.1mfd cap and 15v (3w) zener in parallel with it to filter and hopefully
protect the fan- but now the 15v zener gets too hot as it "clamps off the
ripple" (I only want it to conduct for transient protection). Fan still
going ok though.
A transistor regulator would not be good as- correct me if wrong- it would
show a 0.7 Vce drop. This would cut the fan performance and wasting current
for regulation is not desirable when on battery power. Would a bigger
capacitor provide enough filtering to prevent the zener from conducting
(0.1mfd was a guess)? The resistor needs to be as smaller (ohms) if
possible for faster fan. Can anyone improve on this? I am pushing my
design abilities already. Thanks for any ideas!
.
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