Hi All,
my input voltage varies from around 12-20V, maybe dipping below 12V too sometimes.
I require 12V 50mA power supply, an efficient one, my current schematic uses a step down, which then drives a step up (as well as other circuitry)
how can i do this more efficiently?
Regards

 

A schematic would be helpful.
... "uses a step down, which then drives a step up"...

A step down transformer then a step up transformer???

That in itself is inefficient. If that is not what you mean you need to be more precise in your explanation. Or like I said a schematic would help. Can't read your mind though.

 

While it is technically possible to not use a transformer it is very unsafe to do so. For this reason a transformer must be used for a project done at AAC.

Transformers generally are very efficient parts, their conversion efficiencies can exceed 95%, though it is not a given.

A switching mode power supply (SMPS) is also very efficient, or can be. They tend to be a bit more noisy than their linear counterparts. The linear versions are much quieter, but make a lot more heat. Everything is a trade off.

Submission: Power Supply Circuits

I'm working on an article for the AAC book that is very much a work in progress. It may answer a few questions though.

 

Hi All,
my input voltage varies from around 12-20V, maybe dipping below 12V too sometimes.
I require 12V 50mA power supply, an efficient one, my current schematic uses a step down, which then drives a step up (as well as other circuitry)
how can i do this more efficiently?
Regards

You want a SEPIC converter. Google it.

 

Hi All,
my input voltage varies from around 12-20V, maybe dipping below 12V too sometimes.
I require 12V 50mA power supply, an efficient one, my current schematic uses a step down, which then drives a step up (as well as other circuitry)
how can i do this more efficiently?
Regards

If the input is both above and below the regulated output, I beieve you need to use a buck-boost switcher.

http://en.wikipedia.org/wiki/Buck%E2%80%93boost_converter

http://www.intersil.com/engineeringtools/tools/buckandboostcircuit.pdf