Any simple ways of dropping voltage without disspating power.

Without dissipative losses is a big ask.

A simple circuit I've used for low power using an LM2936Z-5.0 and BC327 instead of the 7805 and BD242 is at

In my application, 13V @ 24 mA in -> 5V @35 mA out using a rather lossy miniature inductor. 56% efficient -v- 40% from series regulation.

The author says she got 65% for 24V -> 5V and 75% for 24V -> 12V.

On Sun, 19 Oct 2008 00:02:47 GMT, snipped-for-privacy@tpg.com.au (Mauried) put finger to keyboard and composed:

If it's just a one-off, then get an old cigarette lighter DC adapter for a mobile phone. Many are based on an MC34063 switching regulator. If the voltage is not quite right, then reprogram one or both of the feedback resistors. If you need one, I have lots of them. Free to a good home, just pay me for postage.

- Franc Zabkar

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Please remove one \'i\' from my address when replying by email.

Many thanks, should have thought of this myself. Got one around somewhere.

You won't get a 100% efficient solution. Around 95% is achievable using the right parts and topology though. If you really want a minimal component solution, a DC-DC converter module is probably your best bet. One with either a fixed 3V output (not common), or programmable via a resistor. That way you get a known efficiency with only a couple of parts. TI make a bunch of them as do many others.

You don't mention cost, board area, prototype or production, or any other parameters.

Dave.

90% is plenty efficient, just need to avoid linear dissapative regulators. Size isnt that important, but I was trying to avoid having to wind inductors which are usually needed in switching buck regulators. Ill try Francs idea of the cigar lighter . As I dont need much power somehing small is all that needed.

For that application, the inductor will be easy. Typically a few tens of uH on a small toroid. You can buy prewound ones, eg. Altronics.

You don't need to wind your own for apps like this unless you need something exotic, plenty of suitable off-the-shelf ones.

Smoking is bad for you.

Dave.

Swiching regulators do this with the best efficiency but tend to use quite a few parts, although for that low curent you may well get an IC that requires few external parts.

Sometimes they're sold as potted 'blocks' too.

Sci.electronics basics and sci.electronics design might being you some useful help.

Graham

Farnell do masses of suitable inductors ready wound. Trouble is the minimum order charge if you have no account !

Graham