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Transformerless Power Supply Circuit

By on April 30, 2013

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If you intend to build a low voltage power supply without having to use a transformer then I believe the below circuit can be a good help to you:




  1. GIRISh

    April 3, 2014 at 9:14 pm

    Thank you for circuit.
    sir, What is FR 100R?

    • Jestine Yong

      April 5, 2014 at 5:01 pm

      Fuse resistor (FR).


  2. Abhinav Chaitanya

    April 24, 2014 at 1:23 pm


    I had an occasion to use this circuit for my electronic mosquito repellent with tweeter. I noticed that when line and neutral is reversed at the source, I get shock on the tweeter.

    Can you explain why this happens and how this can be corrected ?

    I do not know if you have noticed. In this circuit when line and neutral is reversed

    • Jestine Yong

      April 24, 2014 at 8:38 pm

      HI Abhinav,

      I did not notice it and have not build such circuit before. Have you tried adding the ground?


      • Abhinav Chaitanya

        April 28, 2014 at 8:45 pm

        Thanks Jestin.

        No, I have not added ground as part of the circuit.

        However, I have included ground with a LED circuit to indicate whenever there is reversal of Line and Neutral. This LED lights up to warn the reversal.

        The Mosquito repellent circuit is as shown at the following site:

        Else where when I was studying it, it was named Mosquito repellent circuit.

        The purpose of using transformerless power (tlp) supply was to keep the weight of the project minimum and easy to carry while travelling. Although, I have made provision to supply power externally from a power adapter in case the tlp supply fails.

  3. Robert

    April 25, 2014 at 6:07 am

    Hi Mr. Yong,
    Personally, I think they are too dangerous. Transformers are not that expensive, and I think the isolation is worth it.

    • Jestine Yong

      April 25, 2014 at 11:05 am

      Hi Robert,

      You are right.


  4. Denis

    June 27, 2014 at 11:27 pm

    I am sure this piece of writing has touched all the internet visitors,
    its really really pleasant post on building up new website.

  5. Alonso

    September 25, 2014 at 3:01 am

    So far are you telling a tank circuit (a condenser and resistor in parallel) will change voltage from 127 volts to 12 volts ?


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