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Electronics => Projects, Designs, and Technical Stuff => Topic started by: Dragon88 on May 13, 2015, 01:44:04 am

Title: Cleaning up vehicle power
Post by: Dragon88 on May 13, 2015, 01:44:04 am

I asked a question about RF chokes a week or two ago. I ended up making a little RF amplifier board and it works extremely well. I'm now thinking about one or two more designs I'd like to make.

One in particular will be for use on vehicle power. I have everything worked out except for power. What should I do to clean up vehicle power and remove the noise? Current draw will be very low, about 60mA, and I'll be connecting at the cigarette lighter adapter. So far I have:

- Linear regulator to 10V (stay away from dropout when vehicle is off, avoid excessive dissipation when vehicle is on. I don't care if it drops out at crank)
- Schottky for reverse polarity protection
- Big parallel electrolytics on input and output of the regulator, plus decoupling caps

What else should I add? I did find this article:

http://linuxcar.sone.jp/reg.en.html (http://linuxcar.sone.jp/reg.en.html)

A series inductor on the input sounds like a fine idea. What about the "DC line filter" and surge suppressor diode? Anything else?


Thanks.

Title: Re: Cleaning up vehicle power
Post by: JimRemington on May 13, 2015, 04:21:28 pm

This document explains the requirement for the surge suppressor diode and offers some solutions: http://www.digikey.com/Web%20Export/Supplier%20Content/Tyco_8004/PDF/Tyco_AutoNetwork.pdf (http://www.digikey.com/Web%20Export/Supplier%20Content/Tyco_8004/PDF/Tyco_AutoNetwork.pdf)

Title: Re: Cleaning up vehicle power
Post by: Dragon88 on May 13, 2015, 05:50:12 pm

Thanks. I also found this lengthy article/catalog on TVS diodes by Littlefuse:

http://www.newark.com/pdfs/techarticles/littelfuse/TVS_Diodes.pdf (http://www.newark.com/pdfs/techarticles/littelfuse/TVS_Diodes.pdf)

Looks like the only issue I'll have is the inductor for the input filtering. I was hoping to stay all surface mount, but I'll need quite a large value. I guess I'll just roll my own toroid for it.

Title: Re: Cleaning up vehicle power
Post by: DanielS on May 13, 2015, 11:40:54 pm

Here's TI's take on how to protect a DC-DC converter from the transients that may occur in an automotive environment...
http://www.ti.com/lit/an/slva464e/slva464e.pdf (http://www.ti.com/lit/an/slva464e/slva464e.pdf)

See p.4.