power supply

spuffock · Feb 25, 2009

I need a power supply to give 12 to 15 volts @ 25A from a 48v rail. I have nearly always taken the advice that " you don't build switchers, you buy 'em. " But I can't seem to find anything suitable, the websites I've tried seem to be designed to teach you all about the company, the directors names, and the colour of the washroom walls before eventually admitting that they don't make what you want. Anyone out there able to help me find one?

ericgibbs · Feb 25, 2009

spuffock said:
I need a power supply to give 12 to 15 volts @ 25A from a 48v rail. I have nearly always taken the advice that " you don't build switchers, you buy 'em. " But I can't seem to find anything suitable, the websites I've tried seem to be designed to teach you all about the company, the directors names, and the colour of the washroom walls before eventually admitting that they don't make what you want. Anyone out there able to help me find one?

hi,
Have you tried Farnell

Power Supply | Farnell United Kingdom

frieden · Feb 25, 2009

hai its very useful for the students

frieden · Feb 25, 2009

it the best site for the vollege students who have the hobby of doing simple projects

Mikebits · Feb 25, 2009

colin55 said:
Why don't you use a mini 3-terminal regulator. It looks like a transistor and costs less than $1.00 plus a few other components.

That would have to be one beefy 3 terminal device to handle all that power. 48vin 12vout @25A.

colin55 · Feb 25, 2009

I thought it was 25mA.

For 25A you need a huge power resistor before the regulator to dissipate most of the heat and then a 3-terminal regulator with a pass transistor. In all, it is a very big request.

Diver300 · Feb 25, 2009

Buck switcher are the easiest to make, but I'll admit that I've never built one above a couple of amps.

I think that you want several in parallel. You need to make sure that they all give the same current.

You need to consider timing. In a PC, there are several buck regulators in parallel and they are all switched at different times to reduce input and output ripple, and I think that is the best approach. An IC like the LM25576 has a synchronisation input to facilitate that.

crutschow · Feb 25, 2009

Building a power supply that can output 25A @ 12-15V is not for wimps. It would be, shall we say, a learning experience.

There doesn't seem to be a lot of standard devices out there with that voltage and current rating, but I did find this which appears to be close to your requirements (can do 29A @ 12V out and 23A @ 15V out) https://www.electro-tech-online.com/custompdfs/2009/02/ag-350d-ds.pdf.

carmusic · Feb 25, 2009

there a model here
**broken link removed**
and there is a lot of similar model from other brands, just search for a 350w dc dc converter

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