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You are here: Home / Power Supply Circuits / 0-300V Adjustable MOSFET Transformerless Power Supply Circuit

0-300V Adjustable MOSFET Transformerless Power Supply Circuit

Last Updated on February 25, 2020 by Swagatam 145 Comments

This simple MOSFET controlled transformerless power supply circuit can be used for delivering a continuously variable 0 to 300V DC output and a current control from 100 mA to 1 Amp.

To protect against my high voltage research projects from going up in smoke permanently, I developed an easy circuit which is able to render a variable voltage supply of 0 to 330 Volt.

But please be cautioned, the circuit is not isolated from mains potential, and therefore can inflict a lethal shock.

The supply is short-circuit proof: the current is restricted to approximately 100mA.

Circuit Operation

The design does not require a transformer, rather a 100 watt bulb is introduced at the input in order to provide ultimate safety in case of a short circuit or a component failure.

The mains voltage from after passing through the lamp is rectified with bridge D1 (1Amp / 500V) and C1.

T1 is configured as a source follower: the source of T1 complies with the voltage of the wiper of R3. D2 is insured to safeguard the gate of T1.

T2 and shunt resistor R2 establish the current limiter. Whenever the output current results in being excessive, T2 quickly discharges the gate of T1.

This stops the current from increasing any further. The value of R3 was basically identified experimentally; however it actually depends  on the Hfe of T2 which means you may need to adjust the value of R2 appropriately.

Keep in mind T1 requires a large heatsink: in nastiest situation T1 would probably disperse 330V x 100mA = 33Watt!

You may try mosfets such as a BUZ 326 (400V/10.5Amp) or you may likewise use an IRF740 (400V/10Amp).

The output impedance of the power supply varies according to the beta of T1, therefore the bigger the MOSFET, the lesser the output impedance!

Circuit Diagram

UPDATE:

The above design could be much simplified as indicated in the following diagram. The bridge rectifier has been eliminated which drastically reduces the stress level on the MOSFET. However, the ripple generated due to a half wave rectification may be significantly higher. The output 10uF filter capacitor helps to reduce this to some extent. The value of this capacitor could be increased to higher levels for improving the DC quality.

The input series lamp can be added, although this may not be required due to the presence of the current control stage in the design. However, for better safety a fuse may be added in series with the input line.

Video Proof:

This power supply can be used to obtain a regulated power output, variable right from zero to 300 volts maximum. All the devices should be mounted on heatsinks.

Using a Combination of BJT and Mosfets

Circuit Operation

The next transformerless 0-300V variable power supply circuit diagram can be understood with the following points:As can be seen in the figure, a high voltage transistor BF458 is used as the main load handling device.
Its base bias is controlled by another high voltage transistor BF337 whose emitter is clamped to a stable 24 volts.An FET is used for selecting the base current of the transistor BF337 via a pot of 1M.

This setting adjusts the base current for the BF337 which in turn restricts the main transistor BF458s voltage and current flow to the output.

The input to the circuit may be derived directly from the mains AC after proper rectification and filtration using a bridge network and a 10u/400V capacitor.

The entire circuit is extremely dangerous to touch, due care should be maintained while making and testing this circuit.

WARNING: THE CIRCUIT CARRIES LETHAL MAINS VOLTAGE AND THEREFORE IS EXTREMELY DANGEROUS. IT CAN KILL ANYBODY, IF TOUCHED ANYWHERE ON THE CIRCUIT IN POWERED CONDITION. OBSERVE APPROPRIATE PRECAUTIONS TO AVOID ANY MISHAP.




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Next: Free Energy Bicycle Generator Circuit

About Swagatam

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials.
If you have any circuit related query, you may interact through comments, I'll be most happy to help!

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  1. Search Related Posts for Commenting

  2. Peter says

    Hello,
    I’m interested in 220Vac to 220Vac voltage regulator using z network source
    topology. I’m looking for a design using mosfet or Igbt using a PWM controller
    chip. Output is say good for 3kva. Please publish a detailed circuit and complete specs if you have one.
    Thanks a lot.

    Reply
    • Swagatam says

      Hello, sorry I don’t have the mentioned design at the moment with me…if it is feasible I will surely investigate the concept and try to post the requested circuit soon…

      Reply
  3. Johan Degraeve says

    Is the 100 mA a limiting factor? I would need .8 amps @150 DC

    thanks for your clear ecplanations

    Reply
    • Swagatam says

      Thank you, no it is not. Current can be increased by upgrading the T1 and R2 values

      Reply
  4. Akinwunmi Oladimeji says

    .

    Dear sir,
    Having gone through some of your projects they are outstanding.i need your assistance.i need to design a variable power supply of 0v -240vdc with a current of about 50-60amps,I have a source supply of about 240vdc.but I need to vary it so I can use it can suit my purpose otherwise it will spoil what I want to use it for.and also how do i incorporate it to charge a substation battery 110vdc.with 120vdc at full and 110vdc at low voltage i.e switching and working automatically.note I have an igbt module ch400ha-24h . how do i incorporate it for the variable power supply or in to the entire system.i await your generous assistance
    Regards
    Oladimeji

    Reply
    • Swagatam says

      Thank you Oladimeji, sorry I do not have the mentioned power supply design, I guess a variac is the only suitable option for such massive specs.

      Reply
  5. Dani says

    Hi swag how to make 300ampere and 0-150 volt dc adjustable modul/circuits? Thx

    Reply
    • Swagatam says

      Hi Dani, for 300 amp current it would better to go for a variac with a bridge rectifier at the output

      Reply
      • Dani says

        Hi thanks for ur reply swag, btw do u have the schematic diagram for those variac with a bridge rectifier?

        Reply
        • Swagatam says

          Hi Dani, both the items will need to be purchased readymade. The bridge rectifier should be rated at 500 amps as shown below example:

          500 ampere bridge rectifier block

          Reply
  6. Suresh says

    How to deaign a 3000 watt, 300v and 10 amps dc power supply

    Reply
  7. Ioannis says

    Hi Swag,
    thank you for the circuits offered to people!
    I am dealing with a High Voltage Power Supply at say 10-300 (and 30-600 second version), current 10-500mA that will not be pure linear as it has too much losses.
    Tried a SCR controled rectifier to keep the voltage difference to about 10 volts from rectification capacitor to the output and while this work good to about 230 volts, the pulses of SCR closing makes noise and strong current pulses. Also current is not controlled, just limited to the max set.

    Any ideas to a more SMPS circuit?

    Reply
    • Swagatam says

      Thanks Ioannis,
      In the following circuit, if you change the secondary winding to 100 turns, then may be the output could be converted to 600 V, this can be experimented to the required specs.

      https://www.homemade-circuits.com/110v-14v-5v-smps-circuit/

      Reply
      • Ioannis says

        Thank you very much for the tip. Much appreciated.

        Reply
  8. Swagatam says

    The MOSFET is supposed to be attached with a large heatsink

    Reply
  9. Tuba says

    Very nice you did there dude, is this diagram can drawn 10w led x 10, I think it’s equal to 100w?

    Reply
    • Swagatam says

      thank you, yes you can use 10nos 10 watt leds in series, making sure that the pot adjustment is correctly matched with LEDs total fwd voltage

      Reply
  10. Mah says

    Hello Swag,
    I saw a circuit like yours(0-300vdc) which control the voltage of the motor up to 180vdc by pwm. Could it be possible?
    I mean since mosfets control voltage between drian and sourse by gate, can control the voltage by limiting voltage of gate by pwm. is such a configuration possible?

    Thanks

    Reply
    • Swagatam says

      Hello Mah, the 0-300V circuit is not a PWM circuit, it is a simple MOSFET source follower circuit.

      PWM is also possible whch I have already discussed in one of my other posts

      Reply
  11. Anas says

    Hello sir i want to make the transformerless power supply having output of 14volts and 8amp fir my dc load can you help me for this?
    Regards
    M Anas

    Reply
    • Swagatam says

      Hi Anas, I do not have this SMPS design, better to buy a ready made one according to me…

      Reply
  12. Mah says

    Hi Master,
    I made this circuit and run the dc motor successfully without any annoying noise (like i had with the paid 4kw SCR dimmer).
    But there is excessive MOSFET heat that i need your kind help.
    After 1min of running motor without any load the MOSFET heatsink got very very hot.
    Can i replace it with BTA41-600 or IRFP460 to get rid of getting hot? Or something like use couple of IRF840 with large heatsink?
    Thank you

    Reply
    • Swagatam says

      Hi Mah, the MOSFET may be getting hot since you are operating a 180 DC V motor from a 310V DC, due to the wide input/output differential. That is exactly why a PWM is recommended for such applications.
      Sorry, triac cannot be used with DC loads. You can use fan cooling for the mosfet.

      Reply
      • Mah says

        Thanks Swag,
        I prefer PWM too due to the torque. But i dont know why the pwm circuit does not work while all parts were tested and connections checked 1000 times.

        Thank again

        Reply
        • Swagatam says

          No problem Mah, but torque can be achieved only through a a feedback, otherwise no circuit can provide toque at low speeds.
          The PWM design will work only if you test and confirm the stages separately.

          Reply
  13. Amit Chowhan says

    Sir i’m working on this circuit but in my area IRF740 is not available, so instead of this can i use IRF640 or IRF840?? can I just put the 100w bulb in the input or in the output i have to put some load or just check with the multimeter?

    Reply
    • Swagatam says

      Hi Amit, you can try IRF840, it is fine to use this MOSFET, IRF640 will not work. For testing purpose you can add a 10 watt bulb. Output load is not required for confirming the voltage control response of the circuit. Alternatively you can remove the input bulb and add it across the output terminals as shown in the video.

      Reply
  14. Mah says

    Is it possible to make a 220v to 150v transformer and use a bridge rectifier to get 180vdc?
    Kindly advice

    Reply
    • Swagatam says

      That would be an ideal approach. Using transformer will solve the issue very efficiently.

      Reply
  15. Mah says

    Hello Swag,
    How can we get fixed180VDc from the circuit?
    Is this possible to tune the pot for 180V in output then replace the pot with an equall resistor?

    Thank you in advanced
    Mah

    Reply
    • Swagatam says

      Hello Mah, yes that’s possible, you can also do it through a preset variable resistor, once the adjustment is done you can glue it permanently.

      Reply
  16. Martin says

    hi dear friend….
    could you help me?
    I need a variable power supply of 0-120v, 3amps for a hand made proyect..
    Could you give me some schematic to make or some idea how to made that power adjusted supply?
    thank you so much.
    Martin from Argentina.

    Reply
    • Swagatam says

      Martin, the only proper solution is to use a variac, there is no other easy solution for this…

      Reply
      • Martin says

        ok, thanks for your fast response..
        What about your other design…? with TL783..? Can it deliver 3 amps with additionals power transistors..?
        Can you help me to change schematic circuit to get more current with same IC..?

        Reply
        • Swagatam says

          The TL783 will become hot as the input output differential increases, this will waste a lot of power. you can try this but the mosfet will become hot

          https://www.homemade-circuits.com/wp-content/uploads/2019/11/TL783-High-voltage-Adjustable-Regulator.jpg

          Reply
          • Martin says

            Ok, thank you for your answer.
            Even adding that IRF740 transistor, how much more can I demand from the output current to the diagram you sent me?
            Finally, there is the possibility that in the diagram that you have sent me, to be able to control the output current according to what I want, I mean, have control of the desired current in the output?
            Thank you

            Reply
            • Swagatam says

              The current range can be as required by you, provided the MOSFET remains cool. For current limit you can add a BJT network around the MOSFET source exactly as indicated in the above article

          • Martin says

            did you receive my last question?

            Reply
            • Swagatam says

              Yes, and I have answered it!

  17. antony says

    Plz give me the circuit diagram of AC 0-300v/.500ma transformerless variable power supply .

    Reply
    • Swagatam says

      use a light dimmer circuit:

      https://www.homemade-circuits.com/how-to-make-simplest-triac-flasher/

      Reply
  18. pawan kumar says

    sir, the circuit which is shown in image is different then what is shown in video. As one capacitor, one transistor, one zener and two resistance is used but in video 3 zener one resistance is used. please help me i want this variable power supply from 0-150 v for gel electrophoresis purpose.

    Reply
    • Swagatam says

      Pawan, in the video 4nos of 3V zeners are used in series to make a 12V zener. And the current control stage is not used…the basic voltage control set up is the same as shown in the diagram.

      Reply
  19. Razvan says

    Good day,
    I really need to lower the mains voltage (230Vac) to 100V but i don’t want to use this power supply as it is now because it’s current is limited to 100mA and i need about 40A. If i put more transistors in parallel and of higher current ratings and remove R2 and T2 i’am sure the current will go higher, right sir?

    Reply
    • Swagatam says

      Yes that’s right, but the output will not be an AC, it will be DC

      Reply
      • Razvan says

        Good day sir,
        I tried this schematic and as i said i used two paralleled FDL100N50F mosfets and a 5W 12V zenner. This is the problem: when i connect a 2000W load such as a resistor to it, the voltage immediately rises to 187V and won’t let me adjust it from the potentiometer. What can i do to be able to adjust the voltage?

        Thank you,

        Reply
        • Swagatam says

          Good day Razvan, as you can see in the video, it works smoothly for a resistive load, so it should work for your application also, unless something is incorrect in your design.

          I would recommend testing it with a 220V bulb using a single MOSFET, to check if there’s anything wrong in the configuration

          Reply
    • Arun Goyal says

      Sir please suggest me a circuit for 0-50v 0-1amp regulated variable power supply

      Reply
      • Swagatam says

        Hi Arun, you can try this circuit:

        https://www.homemade-circuits.com/0-60v-lm317-variable-power-supply/

        Reply
        • Cornelio Enriquez says

          Good day sir, Can I use these curcuit to supply plate voltage of 250vdc at 150mA? If I parallel two output regulator will it be able to supply plate voltage for my vacuum tube project? Thanks

          Reply
          • Swagatam says

            Hi Cornelio, Yes surely you can do it, but the MOSFET will not need any change. You can either do it by modifying the R2 value, or by replacing the lamp with a 3uF/400V capacitor. Then you can remove T2 and R2 entirely

            Reply
  20. sam says

    Hi Sir,
    SMPS circuit is design with high frequency transformer and KA5M0***R fet for spindle motor drives but the problem is there so much power dissipation across FET so what step should be taken to resolve that problem.
    best regards

    Reply
    • Swagatam says

      H Sam, a power device will start getting too hot if the load exceeds its optimal ratings. Make sure to use an FET whose current and voltage ratings are twice that of the load or the motor rating

      Reply
  21. Hmoud says

    Dear
    I HAVE A UNIVERSAL MOTOR VACUUM CLEANER MOTOR 2000 WAT I WANT TO OPERATE IT ON DC VOLTAGE IS THIS CIRCUIT ABLE TO OPERATE IT
    PLEASE ADVICE ME

    Reply
    • Swagatam says

      Hello, if the motor is a DC motor then it will work with this circuit, but if it’s an AC motor then it won’t.

      Reply
  22. Danny says

    Hello Eng. Swagatam,
    Find below the manner I calculated the wattage:
    Given:
    Number of Batteries in a pack: 16 pieces of Battery
    Ampere of each Battery: 1300mAh
    Voltage of each Battery: 1.2 volts
    Then:
    Voltage of battery pack (total voltage used by the cordless saw): 19.2v=16 pieces of Battery x 1.2 volts (Voltage of each Battery)

    Amperage of the tool (total):20.800 = Ampere of each Battery: 1300mAh x 16 (Number of Batteries in a pack)

    Wattage of the tool (total): 399.36 = total voltage: 19.2v x 20.800amps (Amperage of the tool (total))

    My Summary:
    Voltage: 19.2
    Amperage: 20.800amps
    Wattage: 399.36watts

    Eng. as a matter of fact I am amateur in electronics. I started it as a hobby so please I stand to be corrected on the above presentation.

    In case it is correct, kindly modify the suggested circuit to output at least 400watts/20v power. If there are any mistakes please tutor me on it.

    Now concerning the winding of the transformer, is it possible to recommend already made one for me to purchase. Getting the items required for the transformer to DIY is posing a challenge. Many thanks. Danny

    Reply
    • Swagatam says

      Thanks Danny,

      When supply sources are joined in series, their voltages will add up, but current specs won’t.

      So in your case the total voltage will be 19.2V but the current will be only 1300mAh.

      You cannot draw more than 1.3 amps (max) from this series battery set up for your saw machine.

      And therefore a 1 amp current would be more than enough to charge this battery series, without issues.

      Reply
      • Swagatam says

        …yes you can easily buy one from any online store, or more simply you can do it with a transformer based design, as shown in this article:

        https://www.homemade-circuits.com/how-to-make-current-controlled-12-volt/

        Reply
        • Izul says

          Dear Mr. Swagatam,

          I need a trnsformerless power supply with dual ouput. The first output is to drive leds (50-250/300V, 5-20mA), and the second output is for supply the controller circuit (microcontroller/arduino) (5V stable, 7805).

          Please give me the schematic circuit or link that meets to its need.

          Thanks

          Reply
          • Swagatam says

            Hi Izul,

            you can try this

            https://www.homemade-circuits.com/wp-content/uploads/2019/10/two-output-transformerless-power-supply-circuit.jpg

            remember it is not isolated from mains and can be fatal to touch when powered.

            Reply
            • Izul says

              Thank you Sir.

            • Izul says

              What about following link / circuit, is it able to be implemented for my needs ?

              https://homemade-circuits.com/wp-content/uploads/2015/02/surge2Bfree2Btransformerless2Bpower2Bsupply.png

            • Swagatam says

              It will also work, just replace the TIP with IRF730

            • Izul says

              Alright sir.
              Thank you very much.

            • Swagatam says

              No problem!

  23. Danny says

    Hi Eng. Swagatam,
    Thanks for the numerous circuits and electronic designs you have freely placed at the public domain for our viewing and experimenting with.
    I need a 19v to 19.2v transformerless DC power supply to operate a cordless circular saw whose battery packs are very dead. I hope you can help with a circuit design. Many thanks

    Reply
    • Swagatam says

      Thanks Danny, could you please tell me the current requirement for the load, in amps.

      Reply
      • Danny says

        Glad to receive a fast response from you.
        Unfortunately the cordless saw does not carry any of the requested information on neither the device itself nor the accessories like the battery pack nor the charger set. I saw nothing too in the manual.
        Here are links to the manuals: https://www.alltradetools.com/pdfs/new/archive/Kawasaki-19.2V-3-to-5-Hr-Battery_840638_eng.pdf
        https://usermanual.wiki/Kawasaki/Kawasaki691191UsersManual219633.2052279797/view

        However I want to open one of the two battery packs to see the voltage and amps of each battery as well the number of batteries in each pack. I welcome any advice from you sir. Many thanks. Danny

        Reply
        • Swagatam says

          Surprisingly the linked articles also do not have any reference to the current requirement of the unit. However I assume it to be no less than 10 amps or even higher. Your battery specs might help us to get the required information.

          Reply
          • Danny says

            Yes, I from what I saw in the battery pack embossed on each battery may be of help.

            Kindly peruse these information:
            Number of Batteries in a pack: 16 pieces of Battery
            Ampere of each Battery: 1300mAh
            Voltage of each Battery: 1.2 volts
            Voltage of battery pack (total voltage used by the cordless saw): 19.2v

            Eng. I hope these current information may churn out something good.
            Many thanks for your time and patience. Danny

            Reply
            • Swagatam says

              OK, it means a 1 amp smps would be enough, although i find it strange how a 20 watt supply can power a powerful saw unit?? You can try the second design from this article:

              https://www.homemade-circuits.com/how-to-make-simple-12-v-1-amp-switch/

              to get 19V you can modify the output winding to 20 turns, and change the zener diode to 20V zener.

            • Danny says

              Yes Eng. but my issue is not a charger problem. The power tool came with 2 battery packs but are all dead. They are very expensive to replace so I have decided to convert it from a cordless to a corded tool. That is I want to use an AC – DC power supply instead of a battery pack. So what I need is a circuit that can provide the 19.2v (20v) and the accompanying respective wattage which I guess is about 400w. Many thanks

            • Swagatam says

              Sorry Danny, I got lost, I mistakenly imagined that the batteries needed to be charged. I do not have a 20amp SMPS circuit , and even if I had I wouldn’t have recommended it due to its complexity. The easiest option is to get a 14V 20 amp iron core transformer, and rectify its output using 50 amp bridge rectifier and a 2200uF/50V filter capacitor. This would perfectly take care of your 400 watt saw and drive it smoothly without any issues, although the size of this trafo could be too large.

            • Danny says

              Many thanks Eng. Swagatam for your help and advice.

            • Swagatam says

              You are welcome Danny!

  24. ralph says

    hello sir may i ask if u have a circuit to control the speed of a dc motor 180vdc input 1.5 hp. thanks

    Reply
    • Swag says

      Hi Ralph, you can adapt the following concept and easily use it for your specific application

      https://www.homemade-circuits.com/make-this-pwm-based-dc-motor-speed/

      Reply
  25. Armand says

    Thanks a lot for this circuit? Mr swagatam, i can apply this in my led strip wit 72 leds, each 3 led will light in 12 volts, in total series of led will consume of 208 volts. i ask one more question is this safe for my back light led tv as a subtitute in broaken inverter? thanks a lot for your reply, GOD bless!

    Reply
    • Swag says

      Thank you Armand, I am sorry since this design is not mine I cannot suggest anything with confidence. Although others have built it successfully I still wouldn’t want to risk anything by suggesting on assumptions.

      Reply
      • Kevin says

        Hi Swag, I been looking at your work and find it amusing.
        I need your help, I want to build a transformerless power supply will you be able to provide me with a circuit please.
        Input: 220VAC. 50Hz
        Output: 0-200VDC. 8A Max continues. 12A Peak.
        Thanks and Regards
        Kevin

        Reply
        • Swagatam says

          Hi Kevin, I am sorry, I do not have this SMPS design with at this moment, I think a variac should be the recommended candidate for handling such massive input ranges

          Reply
  26. Edward Martin says

    Can we modify it to have adjustable current too. Where do i need to put a current limit potentiometer. Using direct potentiometer isn’t suitable as i require 3 to 5 amps power.

    Reply
    • Swag says

      you can modify the R2 section with a rotary selector switch and attach the desired number of resistors with it, and then you can select one of those for achieving the required current control limit

      Reply
  27. sham says

    Hello sir ,
    I need to make a circuit which switchover automatically between 11.1v 8800mah li ion battery and smps 12v 2amp circuit.At the load side I have used stepper motor ,TFT graphic lcd and wifi unit which is powered by smps supply. Is it possible to charge a battery with this smps supply and make switching to battery supply in the absense of smps supply.Charger circuit is also required.I am new to electronics please help me to find out charger circuit+auto switch circuit.

    Reply
    • Swag says

      Hello Sham, you can try the second circuit from the following article

      https://homemade-circuits.com/2013/04/automatic-micro-ups-circuit.html

      please adjust the opamp preset through proper understanding and thinking, otherwise you will keep struggling with it.

      The idea is simple.

      pin#3 of the opamp is the battery voltage sensor.

      when the voltage on this pin#3 goes higher than the pin#2, pin#6 switches to the supply level and vice versa, since pin#2 is fixed at 4.7V implies that as soon as pin#3 voltage becomes higher than 4.7V, pin#6 instantly becomes high, switching OFF the PNP transistor

      Reply
  28. elmar says

    sir can i ask a favor ? could you make for me a circuit intended for testing a led strip for led tv back lights? i made this circuit above i used a 1:1 ratio transformer it works well even in a single beads with out damaging it but my fear is the electric shock.

    Reply
    • Swagatam says

      elmar, if you are using a 1:1 trafo then shock is already controlled to a great extent, make sure the current rating of the secondary is less the 10ma, and use a large filter capacitor after the bridge,

      Reply
      • elmar says

        thank you very much sir for your kindness.

        Reply
        • Swagatam says

          you are welcome!

          Reply
  29. elmar says

    hi sir swagatam is this circuit could be use in testing led strip?
    or how to modify this circuit for the purpose of testing led back lights strip without shock

    Reply
    • Swagatam says

      Hi Elmar, shock cannot be avoided in this design, it’s better to use an SMPS based power supply instead of this one if shock is a concern

      Reply
  30. The Rocking Time says

    Hi Sir ..Your circuit ideas are awesome.

    I am designing a variable dual power supply circuit with high current output .. I have a 300 W transformer. I was initially thinking of making the circuit with LM317 and LM337.. but it is very difficult to get LM337 in our place. So I have designed the circuit with 7805 and 7905 Ics. By putting them in dual mode with the ground as common I got +5V 0 -5V dual power.. By connecting 2 pots between the Battery ground and the Ground pins of 7805 ( pin#2 ) and 7905 ( pin#1 ) I could tweek the output voltage from 5V to the full 15V range which was exactly my requirement.. The circuit is successfull in delivering the voltage range.. But the real problem happens next I am not able to take enough current from the output. I cant run high current loads with it. To compensate that I have used 2 to 4 no.s of TIP3055 Ics after 7805 regulator and there was improvement in the current. But not completely.. Now I need the help of you to design the current amplifier section at the output of the negative voltage regulator Ic ( 7905 ). I have several 2N3055 NPN transistors and MJE2955 PNP Transistors with me.. please help in this problem.. I have sent you an email comprising the designed circuit

    Reply
    • Swagatam says

      Hi RT,

      Your 2N3055 connections are correct and they should be able to deliver high current, but make sure to add a low value (may be a 22 ohm2 watt) resistor with the base of each transistor, otherwise they may get damaged if the load is bigger.

      Reply
  31. Faith Jumbo says

    Please the 12v is it as a result of 12v zener diode please how come the 12v and why not use 330v which is the required output voltage

    Reply
    • Swagatam says

      yes it is, but the main reason is that by grounding 12V level the mosfet will be completely shut off…

      Reply
  32. Faith Jumbo says

    Please sir can u elaborate more on how to calculate the value of R2 because if i multiple the value of R2 being 3E3 by 100mA is not giving me the 330v. And in one of the comments i read u said for 300mA R2 will be 2ohms u get by dividing 0.6/0.3 i want to know the 0.6 please can u give me steps on how 2ohms is gotten
    Thanks and best Regards

    Reply
    • Swagatam says

      Faith, use the following formula for setting up the resistor

      R2= 12/current Limit

      for 100mA, this becomes

      R2 = 12/100 = 0.12 ohms

      Reply
    • Swagatam says

      correction:

      R2 = 12/0.1 = 120 ohms

      Reply
  33. Vic Natoli says

    Thanks. I'll give it a go.

    Reply
  34. Vic Natoli says

    Hi
    I'm looking to make a 430V 150ma supply for a tube amplifier. If I use a 350V transformer to supply the input voltage, increase the voltage on C1 to 600V and use a higher rated MOSFET, should the above layout work? What would you recommend as a suitable MOSFET? Any issues that you can see in an audio application?

    Reply
    • Swagatam says

      Hi, yes according to me it should work….

      Reply
  35. Ali says

    Hi dear Swagatam
    i need a transformless power supply for my leds which change 230 v ac to 0-35 v or more
    but please simple and without transformer
    regards,

    Reply
    • Swagatam says

      Ali, you did not mention the current requirement….?

      Reply
    • Ali says

      2-5 amps
      but please simple

      Reply
    • Swagatam says

      that's very high, you will have to opt for an SMPS version, capacitive type may not be recommended.

      Reply
    • Ali says

      Thankss swagatam
      Ok,below 1 amp i can choose?

      Reply
    • Swagatam says

      Ali, you can try the following concept

      https://homemade-circuits.com/2016/07/scr-shunt-for-protecting-capacitive-led.html

      but make sure the SCR is rated above 2 amps

      and change the zener diode with a 35V, 1 watt

      Reply
  36. ronald says

    Hi Mr. Majumdar,
    Is this able to used for electron tube amplifier, without any hum?.
    Thanks so much.

    Reply
    • Swagatam says

      Hi Ronald, hum will depend on the filter capacitor value, if it is properly optimized then the hum can be controlled to the desired limits.

      Reply
  37. Jideofor Igwe says

    Please sir, what modifications can i make in the circuit above in order to get a regulated 12v, 300mA at the output? And i don't need the light bulb at the input.

    Reply
    • Swagatam says

      Jideofor, I cannot suggest much regarding this circuit because it is not designed by me and it can be dangerous if anything goes wrong, especially because it is not isolated from the mains in any manner…

      it's better to go for a capacitive power supply

      Reply
  38. Swagatam says

    if you have excluded the current limiting stage then initially try a resistive load with relatively high resistance such as a 40 watt bulb at the load side or a 25 watt soldering iron etc.

    In this situation the input 100 watt bulb can be eliminated.

    Reply
  39. Kenneth Wermuth says

    Hello, and thanks for the diagram. Have tested it and the setup continues to burn the irf740 as soon as I come over about 250DC primary. Has cooling, and tested with bulb at about ½ wattage. Have tried with less zener, but even 10v burns it. What could be the reason?

    Reply
    • Swagatam says

      Hello, the circuit won't activate until a load is connected at the output, if it's burning without a load then something could be seriously wrong with connections or the device, make sure that the fet "source" is towards the load.

      and remove C1 initially and check the response without it

      also you can try connecting the zener across the gate and bridge (-) of the supply.

      Reply
  40. Swagatam says

    you can do it by altering the R2 value.

    R2 = 0.6/.3 = 2 ohms, is a good value for getting 300mA

    Reply
  41. ainsworth lynch says

    ok then so you haven't desinged any circuit like that +70 -70 & Gnd

    Reply
    • Swagatam says

      sorry, I think I gave you the wrong link, here's the one I wanted you to see:

      https://homemade-circuits.com/2014/07/0-to-50v-0-to10amp-variable-dual-power.html

      but it will require a transformer.

      Reply
  42. ainsworth lynch says

    I would need something to provide -70, +70 and ground

    with this circuit i was wondering if I use the ground from the supply along with each output if that would work.

    Reply
    • Swagatam says

      I don't think that would work

      Reply
  43. ainsworth lynch says

    Can i get a circuit like this that can produce dual polarity voltages for various amplifiers from probably 0-100v at about 3 or more amps, the supply in my country is 110v

    Reply
    • Swagatam says

      you can try the following circuit:

      https://homemade-circuits.com/2013/06/0-300v-variable-voltage-current.html#uds-search-results

      use TIP35/TIP36 instead of 2N3055/2955 in the diagram for getting a 0-100V range

      Reply
    • Swagatam says

      …I do not have a trasformerless design at the moment…

      Reply
  44. bhanu prasad Mishra says

    Thanks sir let me try………but I have an diagram how can I send it to you in which e-mail id…

    Reply
    • Swagatam says

      you can upload it to any free image hosting site online and provide the link to me here, i'll check it out

      Reply
  45. bhanu prasad Mishra says

    Hi sir I want to make a variable power supply for 1Amp load.
    My purpose is to test relays and adjusting 555based, Opamp based circuit….
    Please sir help me…

    Reply
    • Swagatam says

      bhanu, you can use a LM317 circuit as shown in the first diagram here:

      https://homemade-circuits.com/2011/12/how-to-build-simplest-variable-power.html

      use 10k instead of 5k for the pot

      input can be anything from 5V to 30V

      Reply
  46. Arapan Bhadra says

    Thanks Sir.Sir please suggest me a book where I can found the datasheet of different ICs

    Reply
    • Swagatam says

      Arapan, the internet is the best source for learning the datasheets, you can try googling them online.

      Reply
    • Muhamad baidhowi says

      hi Swagatam 🙂
      I want to ask.
      1. if the input should be given 100watt bulb
      2. if the circuit is safe to touch the output.
      3. and for how many watts the resistor wear.

      Reply
    • Swagatam says

      Hi Muhamad,

      1) yes 100 watt is required for safeguarding the mosfet
      2) No the circuit is extremely dangerous to touch
      3)R2 is 2 watt rest all are 1/4 watt

      Reply
  47. Josep Yoga says

    Hello sir swagatam please tell me how make Stabiliser AC

    Reply
    • Swagatam says

      hello joseph, you can try the following circuit:

      https://homemade-circuits.com/2011/12/how-to-make-small-homemade-automatic.html

      more example links can be found at the bottom of the article

      Reply
    • Josep Yoga says

      thank you sir swagatam, i will try

      Reply
  48. Arapan Bhadra says

    Dear Sir please tell me how can I know about the functions of different IC's….

    Reply
    • Swagatam says

      Dear Arpan,
      check their datasheets.

      Reply
  49. nitin gondliya says

    sir plz give modification for high amp like 50amp at 60v thankx in advance.

    Reply
    • Swagatam says

      Nitin, connect more mosfets in parallel with the existing one, and calculate R2 accordingly…

      Reply
  50. Francisco says

    Hi!

    Thanks for sharing. I'm actually designing a similar circuit but with SCRs to improve efficiency, did you think about doing one like that?

    Kind regards,
    Francisco

    Reply
    • Swagatam says

      Hi, yes I have a SCR design using a zero crossing detector stage, but I am not very sure if it would be entirely safe.
      The above design looks more convincing to me.

      Reply
  51. sisir roy says

    Thank you Mr. Majumder for publishing this ckt. However I require a perfect ckt. for charging my 2X1.5 V chargeable batteries i.e. a 3V charger directy from 220V AC main supply, those are generally supplied with chinese make re-chargeable torches (easily available in the local market). My two sets has been damaged & I am unable to use them.

    Reply
    • Swagatam says

      You can use your cell phone charger for charging the 3V batteries by adding 4nos diodes in series with the positive line. The diodes can be 1N4007 type.

      Reply
      • MUDASSIR says

        Hello sir please help me!!!
        I have 220v to 400v 2A stepup transformer, actually according to various condition I want 0v DC to 400v DC using microcontroller’s PWM technique not by any potentiometer resistor, I am expert in programming only but not in power electronics. I need your help….my mobile no. is 8983378973.

        Reply
        • Swagatam says

          Hello Mudassir,

          what help do you exactly need in power electronics, please specify? With 400V PWM the peak will be always 400V which can be dangerous for many appliances.

          Reply
          • MUDASSIR says

            Actually according to various conditions I need DC voltages like 25V DC, 50V DC, 75V DC, 100V DC……………375V DC and 400V DC. I know that , at various T-ON and T-OFF timings of the PWM we can generate various output voltages, but i dont have any MOSFET circuit to do so.
            I request you please provide me a circuit diagram with suitable MOSFET rating so that i directly give output of PWM to the circuit to generate the voltages. As i have said that i already have stepup transformer (220v to 400v)

            Reply
            • Swagatam says

              You can use the set up explained in the following article:

              https://www.homemade-circuits.com/arduino-full-bridge-h-bridge-sinewave-inverter-circuit/

              Repace the Arduino with your PWM input, and make sure to connect the MOSFet drain/source to the 400V DC supply.

              The PNP MOSFET will need to be replaced with a 400V PNP MPSFeTs,and the n mosfets can be FDD6N50TM-F085

              The PNP mosfet may get significantly hot so make sure to mount them on proper heatsinks



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