Need Help with DC Implementation of PowerLine Communication

Thread Starter

John Kelton

Joined Apr 6, 2015
Hi, I am using TDA5051A and trying to use 15V-DC instead of AC volts.

Please refer to circuit schematics on page 18 (Fig 19) at
Our main supply is DC 15V NOT " 250V (AC) " What part of this schematics or components be ignored to make it work with DC 15V? In other words, we have 15V supply which is DC but the chip schemtic shows only AC implementation of the chip.



Joined Mar 14, 2008
Remove the circuitry between the power line and pin 3 of the 78L05 (except for the 470μF filter cap and the 1mH inductor). Connect the 15V through the inductor to the capacitor and pin 3 of the 78L05.
The MOV is not needed.
You can leave the rest of the circuitry as is with the 15V connected to the top right 47nF capacitor (the cap can have a lower voltage rating if desired).


Joined Mar 14, 2008
You can remove the circuitry to the left of C3 except you do need the filters created by the 47μH inductors and 47nF capacitors. Follow the right side of the Figure 15 schematic in your first reference to see how to connect them without the transformer.

You don't need the Zero Cross(ing) Detector circuitry either.

Edit: You also need a 1 mH inductor in series with the 15V supply to avoid shorting the signal to ground through the power supply. And you can't have any other capacitors to ground on the 15V line including any other circuits connected to the 15V unless they also have a 1mH inductor in series.
Last edited:


Joined Mar 14, 2008
So, on Page 11 Fig 10, whats the difference between filter created by C9-L1 VS R1C5L2 ? Thanks
They probably do the same thing but the values are chosen to be compatible with the transformer.

You posted circuit looks fine except you need a decoupling cap after the inductor at the 5V regulator input.
Where does the 15V come from? You likely will need a 1mH inductor in series with that supply also.