AC transformer question

[mklarich]

I need to design a cheap and dirty power supply for a VERY LARGE BANK of LEDs. I mean very large.

Currently running 12 volts DC, looking to change our LED config around to 48 volt strings of LEDs. Need to take anywhere from 90 volts AC to 125 volts ac, rectify, smooth it and make it into a consistent 48 volts DC. Approximately 375 watts.

I for the life of me can't remember all the calculations to find the right transformer off the top of my head. Anyone help me out please?

Thanks much,
Matt K

 

[ScottyUK]

Use a switchmode power supply. It will be round about the same cost as the transformer-based linear supply plus regulation you need to deal with the input voltage variation. There are any number of manufacturers. 48V DC is typically a telecoms voltage standard, so you may well find a supply out there which meets or exceeds you requirements quite easily.



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If we learn from our mistakes,
I'm getting a great education!

 

[fangas]

Hi,

If you're going to rectify to 48VDC, you're going to need a transformer that has an RMS = 48VAC peak.

Or in your case, about 34 VAC RMS.

The formulas I believe you want are;
0.707 X Peak = RMS
1.414 X RMS = Peak

However, like Scotty said, really ought to look a buying rather then building. You will get all the niceties that way, like a chassis.

If you need (want) regulation, then a switch mode is a good way to go. If you just need (want) a relativly smooth brute force supply, then it is pretty standard in the industrial controls area. Either way, there is quite a bit of cheap surplus around.

Hope that helps

Ed