Generating a negative voltage - charge pump or switchmode?

One of my pet projects requires a power supply that gives both +48 VDC and -48VDC (from mains), no more than 3A on each rail. After a bit of a look, it seems that such power supplies are rather rare, especially here in Australia. Maybe I'm using the wrong search terms, but I can't even find a

*single* supply that puts out both +48V and -48V. However simple +48V supplies are relatively easy to get hold of. So, my idea was to tack a DC-DC inverter onto the output of the +48V supply to get the -48V.

Now, this is an area I'm not too familiar with. I've made simple capacitor-switching charge pumps before, but for ten's of mA, not 3 A. And I've never done a proper switchmode supply. My question is - for this situation, which will be easier to get working: a charge pump or a switchmode inverter? Strict regulation is not an issue - the 48V actually goes into another DC-DC converter (don't ask ...) which will hopefully fix any slight discrepancies in the -48V output.

Or, if someone has a link to a +/-48V power supply that you can buy in Oz, let me know!

--
Michael Brown
Add michael@ to emboss.co.nz ---+--- My inbox is always open
Reply to
Michael Brown
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"Michael Brown"

** Err - you need to buy two of them.

Then wire one of them with the + to common.

...... Phil

Reply to
Phil Allison

[...]

I thought this made switchmode supplies unhappy? Or is that just an old wives tale?

--
Michael Brown
Add michael@ to emboss.co.nz ---+--- My inbox is always open
Reply to
Michael Brown

** Try reversing the phase and neutral on that one - should even things up a bit.

...... Phil ;-)

Reply to
Phil Allison

Trying to run them _in series_, i.e., if he was looking for a plain 96 VDC, then it probably won't work. But with the center point grounded, each supply will have its own load, albeit a lot of the time they'll be shared, but each supply does its own regulation and doesn't have to worry about the other.

Just be sure that the supplies have an _isolated_ output!

Cheers! Rich

Reply to
Rich Grise

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