Need Help with DC Implementation of PowerLine Communication

Discussion in 'The Projects Forum' started by John Kelton, Apr 6, 2015.

  1. John Kelton

    Thread Starter New Member

    Apr 6, 2015
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    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 http://www.nxp.com/documents/data_sheet/TDA5051A.pdf
    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.

    Thanks
     
  2. crutschow

    Expert

    Mar 14, 2008
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    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).
     
  3. John Kelton

    Thread Starter New Member

    Apr 6, 2015
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    Thanks a lot for taking time to respond to my question. I have development boards in hand for the chip and the correct circuit schematics is on Page 11 Fig 10. Sorry for the different ref before!
    http://www.nxp.com/documents/user_manual/UM10422.pdf

    I personally think, I should remove all the circuitry to the left of C3!
     
  4. crutschow

    Expert

    Mar 14, 2008
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    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: Apr 6, 2015
  5. John Kelton

    Thread Starter New Member

    Apr 6, 2015
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    Ok thanks, let me draw the schematic and get back :)
     
  6. John Kelton

    Thread Starter New Member

    Apr 6, 2015
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    So, on Page 11 Fig 10, whats the difference between filter created by C9-L1 VS R1C5L2 ? Thanks
     
  7. John Kelton

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    Apr 6, 2015
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  8. crutschow

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    Mar 14, 2008
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    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.
     
  9. John Kelton

    Thread Starter New Member

    Apr 6, 2015
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  10. John Kelton

    Thread Starter New Member

    Apr 6, 2015
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  11. crutschow

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    Mar 14, 2008
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  12. John Kelton

    Thread Starter New Member

    Apr 6, 2015
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    I am also thinking to add the NPN transistor amplification stage shown in Fig-19 Page 18 of http://www.nxp.com/documents/data_sheet/TDA5051A.pdf
    This way I will have a better signal which I guess will amplify the damped signal because of the long length of the supply lines.

    Your thoughts!
     
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