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Which is the most efficient way to get 5v

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limbo:
Hello community.

I need your help in the following project:
I need to create a high efficiency power 5v supply circuit, or better DC to DC converted. The problem is that i'm going to use as source a 12V Lead Acid battery and I want to have the maximum possible efficiency in order not to loose energy.
So using simple solutions such 7805 regulators is out of question!
The output current needed is up to 1000 mA (1A) which is not so much.

Any ideas?

Hideki:
If you intend to build to circuit yourself, use a simple switching regulator like the LM2675 or one of the many alternatives.
http://www.national.com/pf/LM/LM2675.html#Overview

Try the webench tools to find something suitable.

Psi:
yeah, there are plenty of switchmode ICs available.

Maxim sell some super high efficiency ones if you need that.

The key things to be aware of when making a switchmode supply are.


* Use low ESR caps.
* When selecting an inductor make sure its value was tested at near the frequency you will be running it at.
eg, if you need a 100uH inductor for your 200khz switchmode circuit you want to check that it is 100uH @ ~200khz. Some inductors for sale will be intended for other uses and may only be 100uH at 1khz etc..
* The diode needs to be a fast schottky type. The correct diodes will normally say in their datasheet that they are intended for switch mode power supplies. And the datasheet for your switchmode IC will often give recommendations of diodes that will work.
* PCB/wiring layout needs to be what's called 'star ground', basically it means that all ground tracks should come from one central point (the input capacitor). This means each area of your circuit which needs a connection to ground gets its own dedicated path.
If components shared a single ground track and one area of the circuit used lots of current (which happens in dcdc) then there would be a temporary voltage drop across that pcb track. This is bad if anything else is using that same ground track since it sees the voltage drop too. It's important that the feedback system doesn't see voltage drops generated from switching currents.

KJ6EAD:
Dave has done a tutorial on the design of a switch mode converter. I'd give you the link but it's too hard to find in the video blogs episode list.

johnboxall:

--- Quote from: KJ6EAD on October 03, 2011, 03:55:10 am ---Dave has done a tutorial on the design of a switch mode converter. I'd give you the link but it's too hard to find in the video blogs episode list.

--- End quote ---

http://www.eevblog.com/episodes/

http://www.eevblog.com/2010/09/10/eevblog-110-lets-design-a-dc-to-dc-switchmode-converter/

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