Transformerless AC to DC power Supply circuits

I often make small projects. However have problems to find a small power supply is not. The problem is not to find a small transformer, However it is big and heavy. Not suitable for my project. But I see in the small appliance production in China. Do not widely used a transformer. However like to use a capacitor replace. Which it smaller and lighter than a transformer. Today I collect these circuits, so you can select to use in required. Hopefully it will be useful to you. There are 4 circuits, as follows. (see below!)

Danger! Do not touch any part of these circuits. Because you may be hit by electric shocks.

(1.)Power Supply 9VDC no transformer

This is circuiut power supply 9VDC no transformer,It easy circuit and small size.
Volt output = Volt Zenerdiode. Output Current 100mA (min).


It easy circuit and small size. Power Supply 9VDC no transformer
You may know the reason that make power supply circuit have large-sized as a result , because transformer. Way this out be must not use. We use capacitor replace as a result work also well. In Power Supply 9VDC no transformer circuit . The this base equipment have zener diode perform heal voltage be stable or 9V DC Regulator. but kind this circuit be defective that current not tall sir. The detail is other , see in the circuit sir.

(2.) DC power supply not use transformer

Work cycle is C1 and R1 acts reduced AC Current Source to rectifier current is a DC Volt by bridge diode circuit which D1-D4 acts to change AC to DC with the C2 makes the filtering power DC to smoother will a zener diode acts to reduce voltage is equal to the number of volt zener diode and C3 will DCV voltage output that is more smooth.

circuit diagram of DC-power-supply-not-use-transformer

(3.)Negative Volage Regulator 6V not use Transformer

If friends with look for Mini power supply 6V sizes. That give negative voltage. I begs for to advise this circuit. It has prominent small-sized point and light weight. Because do not use Transformer. But still can use current get 0.07Amp not exceed and when see the circuit. Think use Zener diode control voltage be stable that 6V and have transistor enlarge the trend equal to that want. And still systematically protect through the circuit or Shot Circuit Protect with Transistor as well. The detail is other , see in circuit picture has yes.

(4.) DC Regulator supply 15V non transformer

Friends at don’t like large-sized of a transformer. I begs for to advise 15VDC regulator power supply can give the trend current get low about 80mA not exceed. But enough will usable small-sized circuit has comfortablely. Think I uses Zener Diode be formed help maintain one’s position volt be stable , and use Transistor help enlarge current tallly increasingly. Make this circuit is usable well , But friends as a result must use the carefulness specially , because apply to the level voltage tall directly yes.

Today John Lam send feedback to me, It is very good content. Read below:
The use of transformerless power supply dated back at least 15-20 years ago if not earlier. It was a historic innovation at that time when transformer power supply that is heavy, bulky and cost-ineffective is the mainstream power supply in small electrical and electronic gadgets.

Transformerless power supply are normally for loads that consume a small current ranging from a few mA to a few tenths mA. In recent years, they are also designed to supply larger current like those inside a LED light bulb. Every transformerless power supply is in fact custom design specific to the current load of the application, and is put inside an insulated enclosure. The risk of electric shock is minimal. In comparison to its transformer counterpart, it is more cost-effective in manufacturing and more compact. They are not supposed to be used as a general power supply.

For anyone who are interested in this kind of circuits, treat them for educational purposes, learn how and why the circuits work. One can surely try to build one to suit a specific application, but certainly not using it as a general-purpose power supply.

Since Anand mentioned the first circuit is used for a 0.5W LED night lamp. Let’s see how the circuit works.

R2 is used as a choke to limit inrush current, or limit the current in case both the 0.33uF capacitor and R1 fail before F1 will blow off. R1 is a bleeder resistor for discharging the 0.33uF after plug off. Both R1, R2 and F1 are safety features.

The circuit can theoretically supply 22.9mA current.

The equation used is current, I = V / (Total impedance of R1, R2 and 0.33uF)

Since R1 and 0.33uF are in parallel and then in series with R2, the calculation is a
bit complicated to show here. In addition, the actual calculation also have to take into
consideration the 2 x 0.7V = 1.4V voltage drop of the bridge rectifier. For those interested, google on “how to calculate impedance of RC circuit” to learn more.

Next is the bridge rectifier that rectifies the main AC sinusoidal wave into full-wave pulsating DC. The 470uF electrolytic capacitor smooth the pulsating DC to decrease the ripple voltage. Then the ZD1 regulates the output DC
voltage to 9V.

As mentioned earlier, the circuit can supply 22.9mA current, depending on the color of the LEDs used, with 9V output, it provides sufficient voltage and current for either 3 (white LED) or 5 (red LED) connected in series. That’s how the circuit works.

Power dissipated by R2 = (0.023)^2 * (20) = minimal. Any resistor rated 1/8W up is fine.

AC is 220V that translates into a peak voltage of 312V, so voltage rating of the 0.33uF capacitor should be 350V or higher.

Power dissipated by R1 is minimal (you do the math), the 1W rating specified is fine.

For the bridge rectifier, 1N4007 is rated at 700Vrms reverse voltage and 1A, and is more than sufficient for this circuit. 1n4004-1n4007 are all fine.

Since the zener diode is 9V, the rating of the 470uF electrolytic capacitor can be 15V and up.

When no load is connected, all the current will pass through the zener diode when it has the maximum power dissipation, W = V*I = (0.023) * (9) = 0.225W. The rating can be 1/4W, or 1/2W better. The reason that 1/4W will work fine is that it’s a custom circuit, the LEDs are always in the circuit as a load, current passing through the zener diode is in fact minimal.

Hope you enjoy my writings.

57 thoughts on “Transformerless AC to DC power Supply circuits”

  1. These circuits on this page are VERY dangerous to work with because of mains voltage present. You have not posted warnings to that effect to potential builders. A lot more information must be included for ALL components used in these and circuits alike. For the people begining in electronics, these circuits can be a DEATH TRAP. I would also sugest that you get someone to proof read, before you publish material on this WEB site.

  2. “DC Regulator supply 15V non transformer”

    Stop! Attention! To the diagram is drawn ground!!! Probably not (??!) – regards Piotr [ google translation ]

  3. Thank so much for all comment.
    All circuits I see in the Electronic product made in China that low price but low quality.
    I sorry if you make not works.

    I think its is simple ideal for beginner.
    Thank you @Bob Bozanic for the Good advice.
    and…sorry for my English is poor.

  4. The Circuit you are posted is dangerous
    it work but it can kill the use
    please take warning to beginer
    yes China product is not care about security
    and you will follow?

  5. I would like to add more to my first comment. After reading great many posts by readers and would be constructors, especially the questions on various subjects and your answers to those, I believe that the greatest DANGER is to those people who DO NOT KNOW THE OHMS LAW, that is, the relationship between the current (A), voltage(V) and resistance(R). That is where a mistakes are made and with these circuits presented here, it is only a metter of time. Consider this, at 220-240 Volts AC, one will get killed if ONLY 80 milliAmps flows through your body!? Do not forget that DC of 80 Volts or more will give you a nasty if not a fatal jolt.
    It is great to build things, that is how we have learned ourselves, but the basics must not be neglected. So, please, AWAYS include warrnings about danger of mains voltages.

  6. Please Be Careful!! If You Are Uncertain Of Your abilities Don’t Even Get close To Building these Transformless circuits,,I touched 120 volts as a wee lad and am VERY HAPPY to survive this scary experience,,OUCH!!! Please listen to BOB’s advice,,He sounds like he’s been around the block a couple times when it comes to safety in Electronics,,Thanks BOB…I couldn’t have said it BETTER!!!

  7. your ckts are helpfull….but your explanations are not detailed..and your english command is a little bit poor.

  8. Just don’t build ANY of these circuits EVER. They’re all stupidly dangerous for even the most experienced electrical engineer (knowing electronics does NOT make you immune to electric shock-induced cardiac arrest). Transformers are not that expensive and many of the components used in these diagrams (like a 470uF cap over rectified mains) are MUCH larger than a good trannie

  9. Circuits 3 and 4 cannot possibly work with just D1. The other half cycle needs to be bypassed or C1 will just charges up to 350V DC within a few miliseconds, then everything will stop working.

  10. The schematic layout of (1) Power Supply 9VDC no transformer. I live in USA using input of 120 Vac. Do I need to changed any other electronic components after this changed of 220 to 120 Vac? Does it provide very smooth ripples or no ripples of 9Vdc?

  11. whats is the role of transister here used in 15 v transformerless dc supply if any one have idea plzzz answer that…thank u

  12. Once again, it is very obvious by reading these questions that some of you are not taking notice! There is an AC theory that governs and explains all relationships in these and similar circuits. If you value your life, do not do it till you learn what I am talking about. For starters, ANY component used in an AC circuit must have a working voltage of twice the supply voltage. For an example, no capacitor should have less the 400V WV!if a supply is 220-240V. In countries with 110-120V domestic supplies the capacitors must have at least 250V WV. The same goes for resistors not to mention other passive and active components. SO, my advice, get the basic DC and AC theory sorted out in your heads, BEFORE you start playing with these ideas here!!!!

  13. I want to know if I can get some info on how to build a for my 75A 16.8V power supply I am trying to build! Would think there would be more info out there on this subject or you could buy a plug and play to your advantage kit! Thanks

  14. I want to know if I can get some info on how to build a voltage regulator for my 75A 16.8V power supply I am trying to build! Would think there would be more info out there on this subject or you could buy a plug and play kit! This is going to be a HF amplifier power supply and I was also wondering your thoughts about Unregulated? Thanks

  15. Hello,
    I need to create AC 230V to 3.3V DC. And I need about max 150mA. Is it possible to that in this way, without transformer?
    Maybe to gain the output with a transistor also?

  16. chayapon’s circuits are all practical and functional. If your power supply has a transformer that is connected to mains then you can kill yourself with it by doing stupid things. chayapons’s circuits are just as safe as a transformer power supply. Just because they run off the mains does not mean that they harbour mysterious leathal properties ! One must understand what one is doing when working with any electronics circuits. If you cannot properly understand these things then you should sell every electrical device that you own, (flashlights too)then buy a horse and move to the backcountry of Usaria. Where, if you are lucky, you will not be struck by lightening !

  17. Billy Marrowbone Bow Bowling:
    I have 30 years experience designing and building power supplies. That is not an easy thing to build. It will have to be a switching power supply which is even more difficult to design and make. The layout is also critical. I am sure you can find some circuits on the web. If not then email me and tell me what you have done to date and I will try and guide you along. 16.8Vx75Amps = 1260Watts. The power supply will be perhaps 85% efficient which brings the wall output to 1575 Watts, which is almost the maximum you can pull out of the 120V mains.
    What is the purpose of it? If it going to be a battery charger then the current also needs to be controlled.

  18. I don’t want to be awkward but I’ve been looking into the design of transformer-less power supplies for a while now and great care has to be taken to ensure their reliable and safe use. The use of good mathematics and circuit analysis cannot be overlooked. Also consider that the type of capacitors used should be suited to mains operation and not _JUST_ the voltage either. What about when the dielectric develops a fault. X Rated caps maybe.

    I’m still not ready to switch on my first transformer-less PSU without a chicken stick and safety goggles.

  19. Stop accusing the poster who have done nothing wrong. Instead, start providing some valuable inputs to the circuits.

    The purpose of the post is to provide four transformerless power supply circuits and start the discussion. Instead of discussing how and why the circuits work, some readers focus on the dangerous side of the circuits that involve AC. Even if you try to build a traditional DC power supply with transformer, the input is still high voltage AC, 110-220V. No matter what, caution needed to be taken in both scenarios.

    By the way, China-made products are not as bad as some people think. It’s the quality control that determines the quality. Brand name products worldwide choose to manufacture their products in China without jeopardizing sales.

  20. These circuits seem safe to use. Each has current limit protection that will blow the fuse that protects the circuit. One can use an online calculator ( for example) to figure out what the capacitve reactance of the “main” capacitor is and from that what the maximum current can normally flow through the circuit.
    For example, The second circuits main capacitor is CI. C1 limits current by its reactance at mains frequence (60Hz). Therefore in this circuit, it will have a reactance of 2652.6 ohms. This will limit current to 82ma. If this capacitor breaks down, the 250ohm resistor limits current to .88A, this will blow the fuse. This would likely happen before one could get zapped.
    Just be careful. If you are unsure, don’t build it. From a user point of viiew, you are probably using these circuts every day if you are buying stuff from China :)




    Yes, these non-isolated drivers are used in China and outside China, provided that even when the casing breaks, the unaware user can never touch the life-wires. Thats the law/CE mark/TUV/DEKRA etc etc.


  22. Can you tell me Transformerless 9v power supply what should i use capacitor volt only you have mention farad?
    Eg : 0.33farad/…V?,470farad/…v?

  23. Dear Mr Tyrell,
    I can not agree with your very first sentence, I’m afraid. You have looked at circuit number two, calculated reactance of C1 and found the current to be to be around 80mAmps! And if you measure the resistance of your body (easily done) you will find that 80mA is just enough to kill you! Ask you Medical Practitioner, if you do not believe me. You can not be serious saying these circuits are safe to use. No bloody way. Take a look again at the circuit number four as a prime example. Or just for the hell of it, BUILD IT, and when you plug it in, touch the ground pin marked GND. I would like to be there and look at your face when you do this, or any other person foolish enough to go ahead with this. My point all along was this: these circuits are used where very little current is needed, ALWAYS isolated in ABS enclosures and such, should never be worked on when powered because of the AC component present on a NEUTRAL line for half a cycle regardless where you live ( USA with 115V supply, Europe with 220V or 240V elsewhere) And lastly, take a look at questions some readers are asking. One wants to build a supply for HF, he said, 12.8V @ 60A, WITHOUT A TRANSFORMER!! Where do you begin, with explanation? The size of capacitor, for the required current woul be enormous, don’t you agree?
    You would assume this guy knows something about the subject, but I very much doubt it.

  24. will this 9v circuit surely work as it should ?? and I also want to know what is this f1 and In4007 x 4 0ls help me by replying thankz in advance :)

  25. Sir,
    I want to make 0V TO 24 Volts DC supply without transformer..and I want to use LED indication on 6V, 9, 12V , 15V 18V,24 Volts




  26. Hello,

    who ever is thinking about safety , that means you knows the circuit well, then suggest safety in the circuit. he has started the work, lets finished by putting safety.


  27. hello,

    first one circuit is using by a brand company in their 0.5W night lamp led bulb. what you will say about this.

    give constructive comment


  28. Hi ujjval,

    I think you have connected the zener diode in the reverse direction that becomes forward biased and gives you only 0.7V.

    On the zener didoe, there is normally a black ring marked on one side that is the cathode. Connect this side to the positive side in parallel with the 470uF electrolytic capacitor. That means the ring side of zener to positive terminal of capacitor, and the no-ring side of zener to the negative terminal of the capacitor. You will then get an output voltage of 9V.

  29. Some readers want more details on this kind of circuits. Where is my other comment that was sent a few hours before the reply to ujjval?

  30. Would it be possible to make a high current (15 amp), 55 VDC output battery charger using 110 VAC input without a transformer? Maybe with just one large amp diode that delivers just the positive 55 volt pulse from the 110 VAC current? Would that work?

  31. Dear sir/madam!
    I’m Phalla Meak, an Electronics Engineerings student of the 4th Year at Preah Kossomak Poly-technical Institute( PPI) in Cambodia. Now, I’d like to have/know on the schematic/diagram circuit of regulator/auto-voltage (input: 100V t
    o 270V, output: 35V) used without transformers. So, excuse-me, if you don’t mind, could you help to send/show me this schematic/diagram circuit I requested, please? And if I’d like to reduce/drop the output voltage (from 35V to 30V, 25V, 10V, …etc to 0V) to any Electronics devices (such as: mobile-phone charger, radios, etc.), how must/should I use any devices+their values(i.e. variable resistors, etc) to reduce/drop this output voltage? Tell me, please? Thank you ahead for your help to my requesting! Best regard, Phalla Meak.

  32. The circuit of auto-voltages that I’m firstly interested is the kind of transformerless AC to DC power supply circuit, either (1) or (4)

  33. What is value of R1 & R2 in the 6v to 220v ac the circuit diagram and I want to know one more think what is the F1 & S1 because I don’t know what mean by F & S in circuit diagram since I’m not a electronic student.

    Please reply back on my mail address as soon as possible because I’m interested to making a 6v to 220v ac inverter to charge my mobile during cutting Ac supply by our electricity department.

  34. If you are operating such circuits from old type designed inverters which does not produce pure sign-waves, these transformer less circuits wont give desired result.
    Similar supply section in my Frontier make digital timer relay (tr90-48vdc-sc-a4) busted with a burnt capacitor when ac power switched to inverter due to a power outage from electric power supply corporation in my town.

  35. Hi,
    Can I use low capacity ,high voltage electrolyte type cap instead of primary cap in your circuit since its cheaper and more attainable?

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