Input to Output, isolated or not?

[TxMan]

Please excuse my ignorance and my first question on the forum in a very long time.

What is the advantage in a SMPS DC to DC converter in having isolation between the input and output?

Thank you.

David

 

[nigelwright]

There is less chance of mains getting on your output if a fault occurs.

 

[wally7856]

If you have a non isolated smps even if it has a 5vdc output you will have a direct path to 240vac from the 5volt output to ground. So if you touched the 5vdc output you could get electrocuted if another part of your body was touching ground.

 

[TxMan]

Thank you gentlemen.

One further question if I may.

I am in the early stages of researching the best way of creating a 12V input, 48V output DC to DC converter with a relatively high output current in the region of 2kW+.

I have come across a couple of commercial units that from the outside look rather different and I wonder if any members of the brain trust here could enlighten me as to my options.

AFAIK neither of these commercial offerings offer isolated outputs but I can cross this bridge later.

1. http://www.chargingchargers.com/sec-america-converters/model-6948.html & http://www.secamerica.com/pdf/Product Specifications/DC-DC Converters/6948 Spec.pdf

2. http://www.zahninc.com/su14.html

Your thoughts appreciated.

David

 

[TxMan]

Further to the above I have just come across this unit which I find hard to believe could achieve 1.2kW:

http://www.ebay.com/itm/DC-DC-60V-2...lated-Power-Supply-Module-Digit-/180970836951

Shortened URL: http://tinyurl.com/bqhnm9h

Maybe I'm wrong!

David

 

[wally7856]

Here is a schematic i had found that is a 12vdc 2500W inverter. The 12vdc side is just what you need. The output is for 220vac, you would just erase that part and design the transformer for 48vdc output.

It may look simple, but because of the low voltages and the high currents this is a very difficult project. 2000W / 12vdc = 167A, and you are doing this on a PCB. This is almost a research project in itself. This would be very difficult even for people that have made smps before.

 

[TxMan]

Good morning Wally,

Thank you for that schematic.

Yes, 167A is high and probably mandatory to have busbars running on the DC input side to comfortably handle the current.

Can I ask why VR1 is circled?

I wonder if you or anyone on the board can recommend a specialist transformer supplier that has experience of these kind of power supply requirements?

Any further info much appreciated.

David

 

[wally7856]

I do not know why VR1 was circled.