USB charging, Thinking about adding 5volts Options

[worn]

I got a bunch of USB sockets and voltage regulator ICs that will trim 12v to 5v, and thought it would be nice to wire in for charging phones etc. someone suggested that the ICs would fry due to transients. So I am wondering about wiring zener diodes as shunts across the feed and wanted to know what you thought. I am especially interested in voltage and wattage for the zener and perhaps resistance to limit current. Thanks!

[Spoke]

The ready-to-go solutions noted are the easiest ways to get USB power.

If you want to design your own, the 7805 should work well. It is generally accepted in modern cars that 35-40V input voltage capability is adequate. This is partially because modern alternators have power zener diodes to limit the load dump (ISO7637-2, pulse 5) to 35V or so.

Further overvoltage protection could be accomplished not with a zener diode but a transient voltage suppressor (TVS). I use TVS's on my front LED boards to protect the blanking circuits.

You should also install a series diode to protect the 7805 against reverse battery application. The 7805 provides 70dB of attenuation of noise on +12V to provide a quiet +5V output. Filter caps near the 7805 are a good idea.

I highly doubt the USB power would be affected much by noise on +12V line. Audio units are more susceptible since they use +12V directly. The Ultra caps should only be used to provide instantaneous energy for bass and subwoofer applications.