Raspberry pi linear Power supply

معتز سالم

Joined Sep 30, 2017
2
Hello all,

Target: linear Power supply 5v 5a 25w

Components that I bought:
R-core transformer 30va 2*9-0 AC
Regulated power supply board that acts as a rectifier bridge as well, the board has a potentiometer to control the output DC voltage.

The 2 9-0 will be connected together in parallel to have the maximum currently at the same voltage.
Then it will go to the rectifier board
9*1.414 = 12.726 VDC

Question 1: what will be the current maximum value at this stage?

Then, using the potentiometer I will lower the voltage to 5VDC.

Question 2: what will be the current maximum value at this stage?

Basically, it is the same question, only different stages.

Thanks for the support!

Joined Feb 20, 2016
3,564
In a linear power supply, the max available current is the same at any output voltage.
So, as the transformer is a 30VA, the max current will be 30W/9V = 3.3Amps.
I am calling VA watts, as it actually will be a bit lower, and am ignoring losses.

If you went to a switch mode supply you will be able to get just about the max 30VA at the 5V output.
30W/5V =6Amps.
Actually it will be less as mentioned above, I'm ignoring losses.

A RasPi will run very well on a switch mode supply. No need for a linear. Going linear will just waste quite a bit of power.