Transformer less AC to DC power supply circuit using dropping capacitor

Production of low voltage DC power supply from AC power is the most important problem faced by many electronics developers and hobbyists. The straight forward technique is the use of a step down transformer to reduce the 230 V or 110V AC to a preferred level of low voltage AC. But i-St@r comes with the most appropriate method to create a low cost power supply by avoiding the use of bulky transformer.Yes, you can construct power supply for your development without a transformer. This circuit is so simple and it uses a voltage dropping capacitor in series with the phase line. Transformer less power supply is also called as capacitor power supply. It can generate 5V, 6V, 12V 150mA from 230V or 110V AC by using appropriate zener diodes. See the design below.

Circuit diagram

Power supply circuit

Components required

  1. Resistors (470kΩ, 1W; 100Ω)
  2. Capacitors (2.2µF, 400V, X rated; 1000µF, 50V)
  3. Bridge rectifier (1N4007 diodes x 4)
  4. Zener diode (6.2V, 1W)
  5. LED (Optional)

Working of Transformer less capacitor power supply

  • This transformer less power supply circuit is also named as capacitor power supply since it uses a special type of AC capacitor in series with the main power line.
  • A common capacitor will not do the work because the mains spikes will generate holes in the dielectric and the capacitor will be cracked by passing of current from the mains through the capacitor.
  • X rated capacitor suitable for the use in AC mains is vital for reducing AC voltage.
  • A X rated dropping capacitor is intended for 250V, 400V, 600V AC. Higher voltage versions are also obtainable. The dropping capacitor is non polarized so that it can be connected any way in the circuit.
  • The 470kΩ resistor is a bleeder resistor that removes the stored current from the capacitor when the circuit is unplugged. It avoid the possibility of electric shock.
  • Reduced AC voltage is rectifiered by bridge rectifier circuit. We have already discussed about bridge rectifiers. Then the ripples are removed by the 1000µF capacitor.
  • This circuit provides 24 volts at 160 mA current at the output. This 24 volt DC can be regulated to necessary output voltage using an appropriate 1 watt or above zener diode.
  • Here we are using 6.2V zener. You can use any type of zener diode in order to get the required output voltage.


Reactance of the capacitor,
where f is the supply frequency and C is the capacitance.
If the supply frequency is 50Hz, then reactance of 2.2µF X rated capacitor is given by,

So output current,

You can design your own supply if you need high current rating other than 159mA by choosing different capacitor values.

Pin outs of Capacitor, Diode, Zener diode etc


Do not touch at any points in the circuit because some points are at mains potential. Keep away from touching the points around the dropping capacitor to prevent electric shock, even after switching off the mains. Great care should be taken to construct the circuit since there is no isolation between mains and our circuit. Adequate spacing must be given between the components.
Related Power supply circuits:

86 thoughts on “Transformer less AC to DC power supply circuit using dropping capacitor

  1. How we get 24v since the out voltage of the bridge = Vrms X 0.9 = 115 (230/2) X 0.9 = 103.5 is that related to filter capacitor how we calculate the 24v , regards

  2. how can we say that there will b 24 volts in output after rectification
    can u please briefly explain it sir…
    i’ll b very thankful to you if u will clear my concepts about the transformerless power supply circuit…

  3. I come from a lifelong background of software development, but this hardware stuff is all mostly a mystery to me. However, this looks like just what I need! I am trying to miniaturize my atmega328P device, but the power supply has been a difficulty. Now my question – Can this circuit be modified to:

    1) Take in 110vac 60hz USA standard power
    2) Output 12vdc at somewhere around 1 amp

    Thanks in advance. This is a great site and I will look around for more inspiration.

    • 1) You may use the same circuit for 110vac 60hz USA standard power for < 159 ma
      2) Using capacitor power supply for 1 ampere output is improper, use SMPS instead

  4. In the above circuit one diode 1N4007 is need to be put in output side otherwise the LED will be keep glowing if battery is charged due to reverse current. one more thing 6.2 volt diode will give very less charging current and it may also not match the all 6v battery charging voltage so i think better to put 9.1V/1watt zener.
    Tested by me and i got this reverse current problem and successfully rectified.

    • Hi Ashutosh,
      Above circuit is a Power Supply Circuit only. If you are using it as a Battery charger you have to connect the Diode as you said.

      • Dear sir,
        please tell me i have Li-ion 3.7volt 2.2Ah battery with PCB/PCM circuitry.
        now i am trying to charge this battery using your this Transformer less power supply.
        I had check power supply output is 3.3volt & 138mA is it ok for Li-ion battery or any other constant voltage circuit or protection circuit is required plz replay im waiting

    • I am repairing a 26-LED circuit to light a Ganesha’s picture using a 1kOhm resistor, one 470 microF capacitor and 4 IN 4007 diodes made in India. Mains 240V and output around 85V DC. Can somebody tell me how it should be wired. The wires broke off and I’m having problems to make it work.

  5. i have made this circuit and join two white led series and same another two string in parallel to first one

    but the problem is after a some hour of working all the led cant’t glow and burn out so what’s the matter in this

    also can i use 474k poly cap instead of 2.2

    is there need to connect in series with led string or not

    just i doesn’t wont to add the indicater led so i have removed from this so is this happen due to this or not

  6. need betweed to turn 120 ac to dc transformerless this will be used for roach killing trap. copper flats 1/8 spacing.
    know to keep 1hand in pocket when working on this type unit. thanks richard

  7. When I try this circuit, It always burnt the 100R resister, and also LED is not glowing even once. I triple checked the circuit; but nothing wrong found with soldering or components,where the things gone wrong? What should I do? Pls help.

    2.2uf 400v ceramic cap
    470k 1w
    IN4007 *4
    1000uf 35v
    6.2v 1w zener

      • dear sir
        i am looking for a reliable and trusted circuit for 24 v 150 mA dc power supply for led bulb. i liked your circuit but as you said to replace 100 ohm by 10 k ohm resister . is it a trial process or well designed. before publishing this circuit, did you tried it ? kindly publish tried and well design tested circuits.

      • hello yaseen sir ; As Iam doing my project , I need a voltage regulator , so that , I want to regulate from 24v dc to 230v dc by 230v ac input supply ; I kindly request u to give ur contact no ,….. r plzz contact me ; my contact no is … +919524303616

  8. What value of capacitor needed for 6V supply??? I want to remove Zenner diode due to place constraint.

    • My application is also for the 24 volt. So l want to 24 DC as a output so if yo finf any rating for your application please reply me so I can move further as per your 12 cold DC references..

  9. hi
    sir i m working on that circuit,and i got 213V dc after bridge rectifier.when i connect capacitor 1000uf/35v and resistor 100k so that it will warm very quickly because of that zener (6.2,1w) also got damaged.
    component i used.
    2uf 250v X-rated cap
    IN4007 *4
    1000uf 35v
    6.2v 1w zener

  10. Great Work

    i Made this circuit but unfortunately in my area i cant find out 2.2 mf 400v capacitor but i got 474K capacitor circuit works fine
    its out put voltage around 6.75 and current is 15 mA
    but i need to glow 5 mm white led with parallel connection on good brightness (around 20 mA) and this circuit deliver around 15mA Current what to do increase the current

    this whole circuit i want to fit in a wall clock

    also i have 223j 400v capacitor so is it useful in this circuit

  11. using this way of conversion is depending on power loss ; still you need the transformers to step down the voltage without power loss ; the good of the transformers that while step down the voltage the current is stepped up ;
    there is another way that act like transformer known as the buck and boast converters

  12. Hi,

    Why a 1W resistor over the 2.2µF cap, when less than 1/4W will be dissipated in it (and that’s only worst case)?

    In your calculation of output current, you need to include the 100 Ohm resistor. Max current will be <135mA (with a 24V zener and <130mA with a 6V2 zener).

    To assure the longevity of the circuit, add a resistor of 220 Ohm (that should be 1W-2W) in the "free" leg of the mains lead (or in series with the existing cap//resistor), as the 2.2µF cap will be a dead short to the mains for a brief moment when powered up. This will lower the available output current a bit, but at least it will survive being turned on at a mains peak.

    Make sure each soldered connection is extremely well made. Shorts and opens can blow part of the circuit (and hurt the user really bad – so bad they'll never complain).

  13. You have mentioned that it provides 160 m Amp. Also mentioned that 100 Ohm should be 1 watt rated. But when 160 milli Amp flows through 100Ohm, its power dissipation will bw 0.16*.16*100=0.0256*100=2.56 watt. Hence will 1 watt rated 100Ohm work or will it get burnt at this rated current? If we are to have 1 watt rating then current will have to be limited to around 64 milli Amp.

  14. I have made the circuit with 1uF capacitor and after rectification it is giving 330v dc in no load (open circuit). I am working with 240v 50Hz AC supply. So is my capacitor damaged or in no load it should give that much??

    • Your cap. may be damaged or there may be a short …
      You can check the capacitor by first connecting its terminals to a battery for 1 or 2 seconds and then remove it and connect it to a speaker or an led (speaker will be better)
      if the speaker produces sound or the LED glows then the capacitor is okay…

  15. i generated an AC voltage of (120 -150volts) unstable that can light 3pcs 2watts LED Bulb now i am looking for a circuit that can convert it to 12-13volt DC to be used for charging 12v lithium battery…. can you help us…

  16. I need two circuits, one to power 10W 12V SMD and other for 5W 12V SMD
    I have worked with the above given guide and am of the view that for 10W I need 12uF X rated capacitor and for 5W I need 6uF X rated capacitor.
    please guide if I have calculated it correctly and whether any other change is required or not.

  17. dear sir. I have a question. The volatage after bridge rectifier is about 0.9Vrms but the capactitor 50V . it’s not damaged. why?

  18. I am wanting to quickly recharge 6x 350 Farad capacitors that are used for cranking car engine
    combined = 16V 58F

    Capacitor Cycling
    Current, Peak [1s] (A) 200
    Continuous Current (A) 20

    how could I have 2x charge settings and recharge @ stable 12v~14v range
    ( 14v being what most car alternators do) and keep them within the 20 AMP (regular charge @ 240watts = 240v 1A ) and 200 AMP max ( quick charge @ 2400watts = 240v 10A)

  19. sir,
    i want to made dc supply .this also charged a battery.when i made in pcb i saw that output is 8.2and is not goes to zero when supply is off. its means capacitor is charged .why

  20. hi sir i have done same experiment without any mistake. i got the perfect out put. but i got some doubts on this.
    1) when i touch the o/p terminals i got shock, when i put 10 LED’s they worked well, why?
    2) i left circuit with same load for a month then the brightness of LED’s has been decreased, why?
    3) isn’t there any remedy to maintain full brightness for years,?
    note: i don’t want to use a transformer to step down voltage from 230V , 50 HZ AC to 6V or 4V DC.

  21. Saulmtz99 on May 23, 2015 at 2:32 am

    I have an issue with heat. I am using US power 120vac 60hz, The R3:100ohm 1 watt resistor and the 5w zener diode is getting very hot. Cant touch!!! How can i fix this heat issue.

    The components im using are:
    c1: 2.2uF film capasitor 250v
    r1: 1w resistor
    r3: 100ohm 1 w resistor
    c2: 1000uf 50v capasitor
    zd: 24v 5w zener diode
    zd: a full wave bridge rectifier kbp202g
    r4: 2.2k resistor for the led’s

    i need a 24v output with as much current as possible to power up a sensor.

  22. i want to build transformerless circuit with the application of glowing leds in output. my concern is for leds having specification as 2v/20mA, how to bring down the current for the leds as a load?? input is 230v/50hz. output should be 40 or 60volts with 20mA current ?? must help soon plz

  23. This circuit fully wrong. zener already heated & damage. very high voltage produce this circuit. please design new circuit.

  24. i have just make, and try to little modified, i put double 2 470ohm and 2.2uf in front to reduce voltage, and 100ohm with 1k ohm 5watt. with diode 12v. the output around 13.2v. when i energize my led 12v not very bright. what happend ? cause when i use original i the voltage became 30v

  25. No one cant explained about the x rated cap…..I got 230 volts after x rated cap ,after bridge rectifer getting 210 volts DC…….any spec or part number do u have for xrated cap……I worked on so many of x rated cap..

    Wht u mentioned on site ….pls help me r else contact @ 9247187020

  26. I am making a multi function charger which can help to charge any devices as mobile(any type),tablet ,iPods,rechargeable battery(any type DC),rechargeable lamp(any type) etc.I wanted to make a very small size and light weight device.I went through your website and got new idea to make this project.So thank you for your indirectly help me.

  27. Can i use 25v 1000uF capacitor instead of 50v….Also what is 400v X capacitor….please help me here i’m a beginner.

  28. I live in allahabad and the 2.2uF x rated capacitor is unavailable here……Can i use a 2.2uF mica capacitor in pace of that….do you think it will be safe? please reply quick…

  29. sir i have to built up a ckt of ac to dc converter with step up so what specification should i use i am using voltage doubler principal

  30. This circuit is badly designed and will cook up. You designers should stop “guessing” component values and soak test your prototypes under load for several hours. Maybe pre-book the fire department!

  31. Hi Sir,
    I have a step down transforms of 15 volt dc with 4 amps. I want to drop this 4 amps to 2 amps, how can I do this, please do me a favour.
    Thanks and regards

  32. I designed such a circuit some time ago. Failure analysis showed that this circuit presents a fire hazard and reliability problem. Please do your own failure analysis (for at least single component opens and shorts) before you rely on any power line design. I suggest a series resistor on the AC side of the bridge. This resistor should be wire wound power ceramic type. I had to have UL approval (safety) of the product so FAIR WARNING.
    Regards, William.

  33. sir,
    i am looking for a 1 A supply. i like this one but i am really concerned about the sensitivity of the circuit. if you cold give me your contact details it would be very help full.

  34. I need to make a transformerless circuit with output of 5V, 1A for battery charging purpose. Also need to make sure that in any case battery should not get harmed. Can any one help please.

  35. I have used 474j 400 v capacitor which should give 308 miliampere current, and zener diode of 4.7 v to charge a battery of 1 amph.In output I have checked it is giving 4.7 v through multimeter but a single led is not glowing across its terminal why. Is output current is too low. Please solve the problem. And please give actual formulah to calculate output current. And one thing more if I remove zener diode it is giving 50 v

  36. how do you know the capacitace value, the ones i have here, the capacitace value are not shown, i could only see the voltage rating and the power rating.

  37. Hello everyone. Can any one help me about using SMD transforme. How to use it in a circuit? Is it similar like step up or down transformer? how to connect it in a circuit?

  38. Thanks for the information, the reduction is not the problem as most step down transformers are available. To find one that converts to DC while stepping down and provides around 50 to 60 amps is the problem.

    Any suggestions would be appreciated .

    thanks again.



    Please help me on my work simply design.

    I wont to use 12 v when 230 ac v off line by buttery. but when 12v dc discharge automatically chang 230v ac. that right.

    I wont to do not use a relly And a Transformers in my design. So any idea or suggestion with only simple electronics components like itgb , mosfet , fet. use for switching and/or standby 12v dc to 230v ac.

    I have no more time to …………….

    Please don’t mind…..

    Thank you very much.

  40. Please the zener diodes available in my area are tiny ones which would likely burn, so I used 18 pieces of IN4007 diodes to get my 12V output which is somehow stressful and time consuming, so can I use L7812 for 12V DC output instead of 12V zener diode?

  41. my electrolytic capacitor become hot. Is is normal…???
    Mains- 230v AC
    C1 – 225J 400v X Rated
    C2 – 1000uF 50v (+105 Degree C)

    why C2 gets hot ???

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