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Power Supply Design Help

Ray122

Ray122

Member
Hey All!

So I just bought this transformer on eBay A) because I thought it was an okay price, and B) because it was a 300VA 24V - 24V power transformer. What I got was a lot beefier then what I've work with in the past. I'm more use to a center tapped transformer. I've attached the manufacturer's spec sheet below (Which is pretty light).

I'm looking to build a really straightforward +/-24 volt power supply and would appreciate thoughts anyones input on the best way to implement a transformer like this.

At the moment I'm thinking of just tying two legs of the secondary winding together to create a "center tap", but I'm also not totally sure if it works that way.

So any thoughts or sketches would be greatly appreciated!

Best,
Ray

http://www.antekinc.com/content/AS-3224.pdf
 
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That is exactly what you do to create a 24 - 0 - 24 PSU front end.
Coil 1 Blue - Output to positive side of PSU.
Coil 1 Green connected to Coil 2 Blue - both connected to ground.
Coil 2 Green - Output to negative side of PSU.

Bear in mind that once you take the 24/0/24ac through a bridge rectifier you will end up with a +34/0/-34vdc PSU.
 
To arrive at 24vdc you would need a 17-0-17 . Or 34 VCT
 
I cobbled together a dual rail PS in MSPaint using your transformer and attached it. As Powertech pointed out you're going to end up with probably +/- 32vdc heavily loaded so if you're putting this on an amplifier designed to run on 24vdc rails you are going to have problems.
 

Attachments

  • Dualrail_PS.png
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If you build an unregulated supply (per mondialfan) the unloaded peak voltage will be about +34 volts dc on the positive side, and -34 volts dc on the negative side (per Powertech's post). If it is fully loaded, at 15 amps, it will draw down to about 22 to 24 volts dc with lots of big ripple on each side. Do you want to build a +24/0/-24 regulated supply? That transformer would probably support 8-10 amps at + and - 24 volts with a reasonable amount of headroom for a + and - regulator on each rail.
Note that a toroidal transformer with big filter caps will pull a HUGE current surge off the mains when you switch it on. You might consider a soft start circuit for this application.
 
The startup surge on a 300VA transformer should be too much of a problem. My power amp has a 700VA transformer with no softstart and it's fine on a 230vac supply. Of course the current would double on a 115vac supply for the same load.
Ray122 - What are you intending to use the PSU for?
 
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