# How to supply 5v at higher current?

Discussion in 'General Electronics Discussion' started by adamq, Feb 21, 2016.

78
10
Dec 17, 2013
Hey folks... I'm trying to find a solution to supply 5 volts at a minimum of 50 watts--more would be better. The caveat is that it must be no taller than 1.5 inches (goes inside a pre-existing enclosure).

Suggestions welcome

2. ### dorke

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Jun 20, 2015
What is the input to the P.S ?

3. ### davennModerator

13,991
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Sep 5, 2009
and what is the load ?
current drawn is determined by the load resistance

5V x 12A = 60W

78
10
Dec 17, 2013
Ultimately, the power is coming from the mains (120v). The expected load is around 30 watts (5v @ 6A). I'd like room to grow, though, as I may add more load in the future. This is why I am looking for a 50w solution.

5. ### cjdelphi

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Oct 26, 2011
Secretive much?

6. ### dorke

2,342
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Jun 20, 2015
You will probably need a Switch-mode Power supply.
There are more details needed.
1.What is the noise level allowed on the 5V.
2.P.S regulation parameters (i.e. how stable is the 5v).
3.How is the heat from the P.S be dissipated

Will one of these do?

Edit:
Need to contact him about that.

Last edited: Feb 21, 2016
7. ### cjdelphi

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Oct 26, 2011
The space constraint don't forget

78
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Dec 17, 2013
Sorry guys I'm not trying to be insulting by being secretive. I'm working on a new idea.

Dorke, I did see those and similar units while researching. They might be a good option. My worry is voltage drop / ripple / bad power generally. Part of the load is a microcontroller that is adversely affected by bad power.

What does everyone think about using a higher voltage switch-mode PS (say 12v) and several L78S05 in parallel? Does that make sense?

Or would I be better off filtering that 5v psu, say with some substantial caps/whateve else is needed.

Last edited: Feb 21, 2016
9. ### cjdelphi

1,162
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Oct 26, 2011
You can just filter the smp with a good capacitor for 5v supply, linear regulators will waste too much energy from a 12v source..

10. ### davennModerator

13,991
2,018
Sep 5, 2009
I doubt you are going to find a full PSU with your output requirements that will fit into your size requirements
it mite me time to reconsider your project limitations

78
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Dec 17, 2013

13,991
2,018
Sep 5, 2009
great
a solution

13. ### dorke

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Jun 20, 2015
I think it is a bad solution...
VOLTAGE TOLERANCE ±8% , i.e. nearly useless in my book

14. ### davennModerator

13,991
2,018
Sep 5, 2009
well I never said it was a good solution hahaha

78
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Dec 17, 2013
OK. So maybe it's not figured out yet then. I'm certainly still open to suggestions.

Dorke: the board has its own 3.3 regulator, so 4.6v (5v @ 92%) is still sufficient there. Ripple & noise is what I'm most concerned about here.

I understand a substantial cap (bigger the better, yeah?) will filter out a lot of the ripple, but I'm less clear on how how to reduce noise.

16. ### cjdelphi

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Oct 26, 2011
Ripple is noise

78
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Dec 17, 2013
OK I didn't know that. I understood ripple and noise to be two different things. I though ripple was repeating pulses from the power supply (like when rectifying AC to DC) as part of the waveform, and that noise was like random spikes here and there caused by the way switch mode PSU's work.

I understood why rectified AC produces ripples, but I didn't understand that noise is the same thing, this is just stuff I've read and am regurgitating.

Anyway....now that I know its the same thing, do you have any capacitor type/sizing recommendations? Am I wrong in thinking bigger is better in this case?

Last edited: Feb 22, 2016
18. ### cjdelphi

1,162
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Oct 26, 2011
Lots of reasons, but anything that affects the output, be switching, inductors, hum, either way it's unwanted stray voltage...

1000uf per amp i read somewhere, but i think it's a little much

19. ### dorke

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Jun 20, 2015
Well you see,
You do need to totally specify the requirements of the P.S ,
otherwise the solution you will get to will be far from optimal in terms of cost/space/efficiency/reliability/performance etc.

So Lets start from the beginning,shall we?
.
1. What is it "driving"?
(as you now say,
the voltage is converted to 3.3V by a regulator,which one?,
any other like this?).
2. What is the min and max voltage swing allowed?
3. What is the current you need(min and max?
4 .What is the space you have for it (LxWxH).
5. What is the noise and ripple levels allowed?
6. Any safety regulations requirements?
7. Heat dissipation issues?