DC-DC Converter Reverse Polarity?

[digi001]

Hi I am making a PCB that has power coming into the board as 12V and 5V.

However I also need a on-board -12V power rail for some OpAmps. If I use a 12Vto12V isolated DC-DC Brick, then connect it up backwards so that output 12V is ground and output GND is 12V, would this give me the -12V that I need?

What is a better way to do this?

 

[FvM]

See the isolated converter output side as a 12V-battery, does it work?

A better way (cheaper, higher efficieny) is an inverting buck-boost converter.

 

[digi001]

See the isolated converter output side as a 12V-battery, does it work?

I see your point as a Battery. Its just a floating voltage, so Yes. Thanks.

A better way (cheaper, higher efficieny) is an inverting buck-boost converter

Thanks for this suggestion. So I would need to pick out an IC Controller and build a inverting buck-boost? This would be non-isolated, but inverting? Wouldn't this take up more real-estate than a DC-DC brick? Isn't a DC-DC brick just a compact completed solution of a buck-boost or maybe flyback if isolated?

 

[FvM]

Both solutions have their pros and cons.

 

[schmitt trigger]

How much current do you need?
If it is only a few mA, you could do it with a charge pump IC like the ICL7660

 

[dick_freebird]

Depending on how good it has to be, you might be able to
take a capacitor coupled feed off the switching node, and
two more diodes plus another cap gives you a charge pump.
You'll have those diodes' offset of course, but most op amps
don't care a whole lot about common mode offset (the effect
of asymmetric power supplies) or you might even be improving
the common mode position if your input common mode is
above ground.