Robust power supply design

[Gorilla Nerfball]

I'm building a small (1A) power supply for crudely done automotive
appliations, and as I understand it, the input voltage Vbatt can get
pretty messy, with spikes on the order of 200V from the nominal 9-14V.
Can anyone point me towards how I can go about filtering this to the
point that I can run it through an 7805 regulator without fear of
killing it. R-C filters? Clamping diodes?

I'm looking to make a really robust system, something where most worst
case scenarios will get filtered over and over again and everything
will keep humming along nicely.

Thanks,

Chris

 

[Tim Shoppa]

through an 7805 regulator without fear of killing it

Most regulator lines now have "HV" variants designed largely for
automotive applications. The 7805 expires at 35 or 40V in. The HV
variants are usually rated at more like 60V.

All that said, the 7805 itself is a dime. Maybe you want to worry
about protecting the load, rather than protecting the regulator?

 

[Rene Tschaggelar]

Gorilla Nerfball wrote:

I'm building a small (1A) power supply for crudely done automotive
appliations, and as I understand it, the input voltage Vbatt can get
pretty messy, with spikes on the order of 200V from the nominal 9-14V.
Can anyone point me towards how I can go about filtering this to the
point that I can run it through an 7805 regulator without fear of
killing it. R-C filters? Clamping diodes?

I'm looking to make a really robust system, something where most worst
case scenarios will get filtered over and over again and everything
will keep humming along nicely.

Apart from using the HV variant of regulators, perhaps
clamping Z diode with a series polyfuse (PTC) towards
the input.

Rene
--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net

 

[Tom Del Rosso]

"John Popelish" <jpopelish@rica.net> wrote in message
news:41F973F0.6AA2EC13@rica.net...

Start with a 1.5 amp fuse in series with a reverse prevention 3 amp
diode.

I interpret that to mean the diode is shunted in reverse.

If the input is a few volts higher than the regulator's minimum input, then
why not put that diode in series and eliminate the fuse, so you get the
reverse protection without having to replace fuses?

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