Electronic Circuits and Diagrams-Electronic Projects and Design
In Power Supplies

Transformerless Power Supply Circuit

Transformerless power supply Circuit

Description

Here is a low cost and simple circuit that can be used to power up small electronics devices. The power is directly tapped from the mains via resistor R1. D1 rectifies the voltage and C1 and C2 are used to filter the output. The zener diode D2 will regulate the filtered DC and will keepthe voltage steady at 5V.

You may also like: Transformerless Switch Mode Power Supply

Transformerless Power Supply Circuit Diagram with Parts List

Transformerless Power Supply Circuit
Transformerless Power Supply Circuit Diagram

ComponentSpecification
Neon Lamp
R112K
R2100K
D11N4007
Zener Diode, D25.2V, 250mWatts`
C1220uF
C20.1uF

Notes

  • This circuit can deliver only up to 2omA, there fore not suitable for serious circuits.
  • You can use this power supply for small LED circuits etc .
  • Remember you are playing with mains. Always be careful. The transformerless power supply can be made more safe by placing a 1Amp fuse and thus avoid damages due to short circuit. A Metal Oxide Varistor (MOV) can also be included to avoid severe voltage spikes. 

Pros of Using This Circuit

  • The overall weight of the circuit will be much less than  that of a transformer used power supply.
  • Cost can be manages as a transformer itself will cost you almost the same as the building cost of a transformerless power supply.

Cons

  • Not providing options for isolation can bring a lot of safety problems.

We have more Power Supply Circuits that you may like to take a look:

1. 9 Volt Regulator

2. High and Low Voltage Cut Off Circuit

3. Mains Failure Alarm Circuit

4. Voltage Booster Circuit

5. Regulated Power Expander
Author

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16 Comments

  1. roseville roldan

    hi!
    how can i make a 5 volts, 1 amps power supply?

  2. navneet

    i want to control a 6v RELAY.. will this circuit be useful to me.

  3. Ram

    Hello Seetharaman,

    Thanks for the wonderful circuit. Can this circuit be used to sense AC cureent. (whether bulb is on or off) I would like to feed 5v as input to microcontroller to sense whether the bulb is on or off.

    with regards
    Raghav

  4. Seetharaman

    Hi Virender the above circuit can supply around 19 to 20mA where as the circuit for which you are using requires around 70 to 100mA, hence this is not suitable.
    Hi Jimmy The circuit shown above is just designed for 5volt 20mA for which the component values calculaed and used values are more than sufficient. The components which are suggested by you may not work

  5. Jimmy

    Hello sir,

    In the above circuit can i just remove the lamp, use 4148 instead of 4007, use a zener diode with 10v Vbr instead of a 5.2v one, use a 1000uf cap instead of 220uf and use a LM7806 across 0.1uf……….will the circuit work??..any safety concerns??

    thank you.

  7. Layanal

    I want to curcuit for hum free fan curcuit diagram. Any body can help me?
    Tks/Rgds
    Layanal

  8. seetharaman

    Hi Ramakrishna 12 volt 1amp is 12VA. The loss in the capacitor power supply around 15 watts with a shunt regulator not really worth, as the capacitor required will be 15uf 350volt AC will be costlier than the transformer. efficient way will be good switched mode power supply. convert 230VAC to DC and chop it use a PWM and covert to high frequency oscillation use a ferrite pot core transformer rectify and covert to low voltage high current power supply. losses will be the least ( the efficiency approaches 85 to 90%) Capacitance type power supplies are suitable for low current requirement only.

  9. rama krishna

    hi,
    im rama krishna i need a ckt that provides 12 volts with 1 amp D.C output without using transformer

  10. John

    I’m actually converting 24vac to 5vdc (100mA needed for circuit) and found this circuit while searching for least expensive parts. This circuit is going outside in the Arizona sun (120F) so effiecincy and temps are a concern. I’ll probably go with something like the LM2574 (DC to DC Converter and Switching Regulator Chip) which seems overkill. 🙂 Thanks.

  11. seetharaman

    Hi John R1 can give you a maximum of 20mA only. You have to reduce R1 to 2.2K 25watts with 7805 regulator and a protective zener of 9volt 1watt before the regulator chip. i dont know whether it is a proposal worth. For high current better to switch to capacitor type.

  12. John

    How can I get enough 5vdc mA to power a 100mA relay? More Zener diodes in parallel? Or bigger zener?

  13. Sohail

    I built this circuit and enclosed it in old Energy Saver Bulb. Mounted two White LEDs on top of the enclosure. That works fine for night light.