FEDEVELPlatform forum

High Current power supply

sneha.xeye , 02-15-2017, 01:13 AM
Hi,
i want to know that is that possible to get 3Amps of current in 5V or 12V dc supply?
if yes then what are the options to do that using basic components that costs less and give the satisfied results?
robertferanec , 02-15-2017, 05:32 PM
Please, could you clarify your question? Do you already have a specific 5V/12V power supply or you need to convert an input voltage to 5V/3A?
sneha.xeye , 02-15-2017, 09:21 PM
@robertferanec i want to design 2 power supply for 2 different applications (12v & 5v) if someone help me to design any one of them then i'll design the another one from that... i just want to know design a supply that will provide 3A current using bsic component..
Luca , 02-16-2017, 12:44 AM
You need to start from AC voltage (for example 230Vac) and convert in 5Vdc? If yes, you need a galvanic isolation?
Or you need to convert 12Vdc (for example from a car battery) in 5Vdc?
The 3Amps you mean continuos or peak?
And also, what do you mean with "basic components"?
Or if it's more clear, which components do you consider "basic"?
Regards, Luca
sneha.xeye , 02-16-2017, 02:53 AM
@Luca i want to convert 5v/12v from 230v Ac.. & i meant basic component is that is easily available at cheaper cost & which is generally used in power supplies or adapters..
sneha.xeye , 02-16-2017, 02:58 AM

i found this power supply if i replace 12v-2A transformer with 12v/3A transformer then will this circuit generate the output as i want (5v/3A)? Or some other modifications is possible in this circuit to get 3A output?
Luca , 02-16-2017, 04:01 AM
This is a linear regulator, 7805 can regulate the output at +5V at 1A of maximum current.
That regulator, alone, can't supply 3A.
Of course, if you want to continue in this way, you need to change the line main transformer for more power and then use different schematics for regulate the output.
You can still use 7805 like regulator and you can add a power transistor, for example, to provide more current at the output; but this is only the one way to do this power supply...
I invite you to think about the main transformer specification in that schematic, read the inpunt voltage... 230V (110V)..
It's strange because there aren't any switch selector for different windings of that transformer so... with one seconday and one primary the output current and voltage of that transformer will be only one... impossible to work well in a different input voltage.
So first of all you need to know, or decide, if you need the power supply for multiple input voltage or not...
Then i suggest to think about the efficiency of this kind of system for regulate the voltage at 3A... remember, this is a linear approach and 5V x 3A = 15W
Think, make your decision and... we are here
sneha.xeye , 02-16-2017, 04:17 AM
yeah transformer will be one only this one is downloaded image what i'm going to use is 230v-12v/3A then it can work well by replacing the transformer only am i right?
Luca , 02-16-2017, 05:03 AM
No... 7805 linear regulator can't provide 3Amps...
robertferanec , 02-16-2017, 10:45 AM
@sneha.xeye, normally we would not be designing this kind of thing, we would buy an existing adapter. Can not you do the same - use an existing adapter?

PS: Do not forget, this kind of circuit/board is not cheap and you need to pass additional tests to be able to sell your product (because of high voltage input power).
sneha.xeye , 02-17-2017, 02:26 AM
Oh.. Thanks @robertferanec
nachodizz990 , 02-24-2017, 02:13 PM
Try an LKN device and a buck converter after that but carefull because the LKN is not an isolated off line solution