Steady 12V Supply From Car Battery

[StudentSA]

It is quite well known that a "12V" vehicle battery will fluctuate in voltage level between, roughly 11V - 14.5V, during the general running cycle. Trasient high voltage spikes are also known to occur and can damage sensitive circuits.

Im quite surprised that I cannot find a "tried and trusted" method to gain a regulated 12V constant output voltage circuit?

My requirements is 12V at low current (<1A) for simple logic circuit. A Ripple of <0.5V will be considered decent.

Can anyone recommend a low cost method of achieving this?

Regards,
StudentSA

 

[mneary]

National's WebBench designer shows the LM3478 in a suitable circuit with an estimated cost of $4.19. Their example with the LM3488 has a total BOM of $3.31.

 

[Ubergeek63]

National's WebBench designer shows the LM3478 in a suitable circuit with an estimated cost of $4.19. Their example with the LM3488 has a total BOM of $3.31.

Nice...bout time they put SEPICs into WebBench... I have been using the LM3488 as a SEPIC for a long time and did not have the benefit of WebBench.

 

[Hero999]

Does it matter if the voltage occasionally drops below 12V, as long as it doesn't exceed 12V?

How much current is needed?

If it's just a few A then you could use a low drop-out linear regulator.

https://www.electro-tech-online.com/custompdfs/2010/05/KA378R12CTU.pdf

 

[stevez]

On page 17.28 of the ARRL 2009 Handbook for Radio Amateurs is a switched mode power supply that addresses those concerns. Current handling is far in excess of your requirements but I felt it worth mentioning. You can purchase commercial equipment that does the same thing.