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    This 12 Volts transformerless power supply take advantage of the fact that a Zener diode is also a normal diode that conducts current in the forward direction. During one half wave, the current flows via D1 through the load and back via D4, while during the other half wave it flows via D3 and D2. Bear in mind that with this circuit (and with the bridge rectifier version), the zero voltage reference of the DC voltage is not directly connected to the neutral line of the 230-V circuit.

    Transformerless Supply Circuit Schematic

    12 volts transformerless power supply diagram

    This means that it is usually not possible to use this sort of supply to drive a triac, which normally needs such a connection. However, circuits that employ relays can benefit from full-wave rectification. The value of the supply voltage depends on the specifications of the Zener diodes that are used, which can be freely chosen. C2 must be able to handle at least this voltage.

    The amount of current that can be delivered depends on the capacitance of C1. With the given value of 220nF, the current is approximately 15mA. A final warning: this sort of circuit is directly connected to mains voltage, which can be lethal. You must never come in contact with this circuit! It is essential to house this circuit safely in a suitable enclosure.

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    7 Responses to "12 Volts Transformerless Power Supply"

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    1. Pentaconto says: on August 23, 2010 at 1:31 pm

      In the Circuit Diagram are not labeled the parts (C1, C2, D1, D2, D3, D4), the explanation of how work the circuit is not good because this problem. Please correct this in the circuit diagram.

      Greetings from Barcelona (Spain)

    2. dear sir

      can i use this circuit for your Automatic Gate Lamp circuit

      thank you…

    3. I am not sure how this circuit might benefit the relatively inexperienced readers seen here.
      The output current is minute, barely capable of driving a bright LED, & that requires further voltage reduction, details of which are not shown.
      Nor do you suggest an appropriate fuse size, or include an MOV. Surely bearing in mind your warnings these are almost mandatory, that is if you wish to be part of the solution not the problem.

    4. O.C.Bessong says: on July 18, 2012 at 6:24 pm

      Pls sir, i need a complete writeup about this circuit. Thank you!

    5. thank you i need a complete writeup about this circuit…..

    6. pls send me simple circuit to produce 12v dc without using transformer

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