So I have a power supply for a specific purpose. It produces 80VDC 10A. I would like a secondary supply of 13.8V at 3A. The problem is that NONE of the DC to DC convertors produce this voltage and support over 50V input. So, basically I'd like to keep it simple and just use a transformer. Can anyone help me calculate the exact transformer I would need to produce the 13.8 3A from the 80VDC. Thanks! I know I could use a cheap meanwell as secondary PSU, but I'd rather do this compactly and elegantly.

 

that is not how it works.... transformers ONLY work with AC.

 

Yeah, that was stupid. I should know that by now.

So what would be the best option then? Maybe several voltage regulators? They have to be balanced when connected together, right?

 

It may be worth a try using a "universal" input switch mode supply, or just a 110V input one. you probably will not get full rated power out, but if it works, maybe a 110V AC to 13V8 10A supply could give you the 3A required.
Do you have a mains switch mode supply you could hookup to try?

 

A buck converter would be the typical type of circuit to deal with this problem. Unless your comfortable and have experience with using an 80V system I'd stray away from trying to tap into it. (Btw from a quick search on an electronics distributor there are tons of reasonably priced options that would get you in the ballpark of 12V 3A) I tried to to do the same for my old e-bike way back when (had it running at 48V) but it just made more sense running off some of the individual cells in the packs to get my 5V rather than hack at the high voltage with a probability to shock myself.

So, in conclusion, I suggest to separate the power supplies for your sanity and safety. (it will likely be cheaper for you in the long run too especially if you're running off 110AC)

 

Hello,

Look for a DC/DC down converter.
The LTC7801 can work upto 140 Volts input:



Change Ra and Rb to adjust to the wanted 13.8 Volts.

Bertus

PS there are more chips capable to do the job:
http://www.analog.com/en/parametric...=15|max&p5362=Buck&p5573=min|40&p5574=100|max

 

Yeah, that was stupid. I should know that by now.

So what would be the best option then? Maybe several voltage regulators? They have to be balanced when connected together, right?

https://www.aliexpress.com/item/RD-...f142-4bbc-9658-2b31e150eeb4&priceBeautifyAB=0


This is a 5amp out 80volt in buck dc to dc.