power distribution

[Ram44]

Hi,

I am new to this form and i have been assigned to design a power distribution board that distributes 12V and 5Vdc to about 10 other boards. i am not sure how to proceed with this. i know that its not as easy as connecting the voltage lines. any guidance on how to go about with this shall be appreciated.

thank you

 

[buzzp]

Power requirements for each DC bus (loads)?
Regulation requirements (accuracy)?
Distance to other boards using this power?
Any filtering on the boards that need power or is all filtering expecting to be done on main power board?

Answer these questions and you will have a decent start.

 

[Warpspeed]

The biggest problem you will face is with the common grounding system. Start thinking about voltage drops, noise, and potential differences between the common 0v point on each circuit board.

A few tens of millivolt drop on the "hot" side is usually no problem, but on the common side it can be. So start at the individual loads and plan your power distribution system accordingly.

 

[Ram44]

Power regulation is being done locally on each of the 10 boards. Worst case full load scenario is about 150mA on one board.
Each board does the same function and work alike.
The distance to which the power has to be distributed is about 2 feet maximum where the 10 boards would be located on either side of the board.
Each board is around 4-6 inches apart.

IS there any tutorial or any link I could follow to have a better understanding about power distribution boards and guidelines to design them. I looked around for tutorials and could not find many.

Thank you

 

[VEBill]

150mA per board ? On board regulators ? 2 feet ? This is hard up against the fairly easy and low risk end of the difficulty spectrum.

Power distribution get tricky when you're dealing with 100+ amps per board of centrally-regulated 5 Vdc (the 'good old days').

Is there something particular that has you worried?

 

[buzzp]

If regulation is done on each board, then you have an easy design. (judging by your comments this appears to be the case). Check out some application notes on regulators, such as at national semiconductor

http://www.national.com/apnotes/Analog-Regulators.html

Typical regulator part numbers might be LM7805, LM340, etc.
These app notes will help you.

 

[Warpspeed]

It sounds as if your problems are going to be negligible with those design requirements.

A very good book on grounding, noise and EMC principles that covers power distribution problems and theory, is "Noise Reduction Techniques In Electronic Systems" by Henry W. Ott ISBN 0-471-85068-3