Mazilli ZVS Flyback Driver


The Mazilli ZVS flyback driver is well-known throughout the high voltage community for its simplicity and ability to deliver 20-50 kV at high currents for a flyback transformer.

I build this circuit almost a year ago on a vero board, but it kept blowing the thin traces due to high currents flowing. I eventually put the project in a box and forgot all about it.

Inspired by the point to point soldered designs Myke from the forums often uses, I tried to make something in that manner, not as pretty as his work though.


WARNING!: Working with electricity is dangerous, all information found on my site is for educational purpose and I accept no responsibility for others actions using the information found on this site.

Read this document about safety!


The MOSFETs used need a voltage rating about 4 times higher than the supply voltage and a on-resistance below 150 mΩ

5 + 5 primary windings are suitable for voltages between 10 to 40 VDC, at higher voltages additional windings will be needed. Experiment with the number of windings to improve performance. Too few windings will result in excessive heating and too many will result in reduced power output.

A MMC is made from 6 capacitors to avoid excessive heating in a single capacitor.

This driver will push as much power as it can, so be sure to use flyback transformers that can handle the abuse if you want it to live.


Voltage supply35 VDC from a rewound microwave oven transformer.
MMC0.66 uF from series string of 3x 2 275VAC MKP X2 capacitors in parallel .
Power consumption400 Watt.
Longest arc100 – 110 mm long white arcs

 Mazilli Flyback Schematic

 Construction of Mazilli Flyback Driver

15th may 2009

I have now rebuild the driver using 2.5mm² / 14AWG wire for a good current ability, larger heat sinks and a MMC to avoid as much heating as possible.

 Flyback Transformer Sparks

16th may 2009

I found 4 different flyback transformers from my collection, among these are a 1980’s Bang & Ollufsen television flyback. A small flyback from a photocopier. A  flyback from a 1990’s portable television, it is without screen and focus resistor networks. A flyback with rectifier tube from a black & white 1950’s television.

The pictures with long arcs about the size of  100 – 110 mm was made with the 1980’s Bang & Ollufsen flyback transformer.


It was well worth it to rebuild this driver. It can now handle long run times with little heating despite pushing out around 400 Watt  of power!


170 thoughts on “Mazilli ZVS Flyback Driver”

  1. Daniel Cuneo AKA wannabegeek on


    I am a physics student with some experience with electronics. I have ordered parts for the ZVS
    driver you are using.

    I have a question about the toroidal inductor. I have some ferrite toroids laying around I pulled from computer
    monitors while getting their flybacks. I don’t know how to look up their characteristics to calculate the inductance. In the past I tried using a bridge and Oscope, but that has not worked well for me.

    Is there a rule of thumb that will get me moderate enough accuracy to make a good circuit ?
    The flyback I have choosen puts out a strong arc with my 555 driver. More so than another larger looking FB.
    My MMC kinda sucks since I didn’t figure what to buy until after I spent some money, so I need to break (use) what I have first; 50, 2KV ceramic 0.01uF caps, 10 series = 1nF with a max of 5nF.

    As well, I don’t have 2W resistors but do have 1W resistor….hoping that will work enough to get started
    especially since I can only draw 5 A from my supply.

    I’d love to make my own power supply. I have tried to make a small one for practice but the loading is confusing me. I started with 35 Vpp and by the time it as rectified and had a large cap in parallel, it was down to 3 VDC. I would prefer to make it regulated. I had an electronics lab which built a Wilson mirror and a BJT voltage. Do you have a link to a good schematic or can I use yours ?

    thanks for reading all this…

  2. Hey wbg

    I would advice you to get one of those real cheap LCR meters off of Ebay, they have a good accuracy compared to their very low cost. A LCR meter in invaluable in electronics anyway, you need it!

    Salvage some MKP X2 capacitors from a pc power supply or anything else that uses them for input filtering, if you have no money to spend on these very common and cheap capacitors, your MMC is far from enough with only 1nF.

    Get a variac for a “cheap” variable supply, a variac will take any abuse up to 300% of its current rating for short runs of a few minutes, with a nice lab power supply you will risc damaging it powering up circuits like these that can have some heavily back EMF through the circuit.

    Kind regards

  3. Pingback: Video of My High Voltage ZVS Flyback Driver - Laser Pointer Forums - Discuss Lasers & Laser Pointers

  4. Hello
    I am an engineer working in the maintenance of machines for laser
    I want to know if you have a high-volt flybacks transformer, such as in the image
    it is used in 80w laeer power supply
    How much is the price
    Please reply as soon as the maximum

  5. Hi, could I substitute the IRFP250N’s for IRF540? I do not think there is too much of a difference between them but just though I would double check.



  6. Thanks.
    One more thing, is the large MMC vital? or can I use a smaller arrangement of odd value caps to make 0.68uF or perhaps even a single cap just for now?


  7. You can use anywhere between 0,1 to 1,5 and properly other values too, but depending on voltage ratings, capacitance etc they will generate a great deal of heat loss, which i why I made that arrangement.

    It will also change the resonant fequency of the circuit, so experiment with different values and see what performance you get 🙂

  8. Make your own, its cheaper and can withstand higher current.

    If you use a good ferrite core you can get away with as few turns as I, if its a yellow iron powder core from a atx psu f.ex. you need 70-100 turns I think.

  9. Thanks, So the inductor on that page is not suitable for this type of purpose?

    The problem with making my own is that I do not have an LCR meter to measure the inductance of a homemade inductor.

    I think I can get hold of an old ATX power supply from a relative who I will ask if they will let me have it sometime during the week. I can also salvage the heatsink and cooling fan from it.


  10. Alex

    You should buy one of these:

    Its a cheap hong kong LCR meter, but to the money and amateur use its accurate more than enough 🙂 I have this exact meter and it have served me well, tested up against my fluke meter there is really no difference.

    What I meant by making your own is that you learn something about inductance, tedious winding work and getting parts for free, if we wanted we could buy it all, but where is the fun (or where are all my money!) in that? 🙂

  11. I have now got the parts and have come up against something I can not find any answers for on the internet, the pin-out of the two IRFP250NPBF MOSFET’s I have purchased.

    Which pin in the gate, drain and source?



  12. Congratulations, that is a fine output you have there, not too current heavy, so might be useful for some high voltage applications that does not require a large current.
    Try to up the voltage and you will get some really fat bright arcs 🙂

  13. I just tried it on 24v. Wow! It made a big difference, much hotter, thicker and longer arcs. My chicken stick electrode sparked like a sparkler if I let it get hot enough.

    I should have a video up in the next day or so as I am going to wait until it gets dark and film some arcs with the lights off.


  14. Hi Mads, You have a really nice setup there 😀 i will try to buy some better mosfets because mines just dies IRFZ44N and other that are non suitable for this application so my question is if i can use: IRFP240 or IRFP450 or IRFP9240PBF don’t know which(IRF450 is my choice because of the price) please let me know which of them is the best for the job.
    Regards Cip

  15. Hello Ricardo

    I can understand from your parts in question that you want to run at higher voltages, it can be done but you might run into some practical problems like…

    1) If you run the circuit from a variable power supply, you will initially draw too much current at low voltage and your components might not be able to handle that.

    2) You need some voltage overhead for your MOSFETs to survive, using the IRFP250N MOSFET rated for 200 Volt, I would say that about 40 Volt is good safe limit. Thus for the IRFP460BF it would be around 100 Volt input, maybe even less.

    3) Higher voltage also means that you will be running a higher Volt/turn for your primary coil wound on the flyback transformers core, this will eventually fail if its too high, you should use 8+8 windings or more. More windings will also mean reduced power output, but your MOSFETs will survive instead.

    In the end there might not be a big difference in the output from going for high voltage as you have to take your precautions to insure its safety.

  16. Hi Mads.

    YouTube have recently gave me monetisation features which enables me to make money from adverts on my videos.

    I have enabled them on a few of my videos already but though I would get your permission first before I enable them on the video I have embedded in my comment above. Since I followed your component list in the schematic to make this circuit I feel I should ask first before I enable adverts since you came up with what components to use.

    Just let me know in the comments here, I will not be offended in any way if you do not want me to enable adverts on the video I uploaded above.



  17. Hi Alex

    Its is infact Vladimiro Mazilli that deserves all the thanks for this design, just a heads up on ads, it takes years to get a payment when you are just a private person 😉

    Kind regards

  18. Thanks for the reply. I will leave the revenue sharing for that video turned off then, or at-least until if the video ever became very popular (which I doubt it ever will).

    Oh I know that it was designed by Vladimiro Mazzilli and I have given him credit in the description. (Any idea what year he came up with it?).


  19. can is use the 2N3055 instead of IRF250at same 20vDC please reply me i am about to do this because this circuits gives good performance rather than other circuit i am waiting for your reply…….

  20. No you can not, if you look at the datasheets for the 2N3055 transistor and the IRFP250 MOSFET you will see that there are considerably differences in their specifications and they are not even the same type of transistor.

  21. Does anyone know any replacements for MKV capacitors? I can’t find them anywhere…
    I am currently using newark to purchase my parts, “”.

  22. I went through my stash of capacitors and found a 2500 volt, 1 micro-farad capacitor. Would that work just as well?

  23. Hey Usman

    1uF would work fine, but watch the temperature of the capacitor.

    Its a MKP not MKV capacitor, its short in Europe for metallized polypropylene capacitors

    Kind regards

  24. Hey Robert

    nd often means No Diode, but you should check the data sheet to be sure about differences on parts. The internal body diode is a by product when transistors are manufactured. But they can also be without.

    Kind regards

  25. Hello! I want to point out another important matter with this driver: Use a good (large) filter capacitor on the bridge rectifier. If you hear the 50/60 Hz humming, you have not enough capacitance. The transistors will have a greater power loss (and heating) when turning off while there is still some power left in it due to the mains halfwaves. I got one FET to spectacular blow up while experimenting with this ^^;

  26. Hi everybody, I not work in physics but interested in flyback circuit. I tried the circuit of Vladimiro Mazzilli. I don’t have a couple of IRFP250, so I replace with a couple of IRF640, but then they’re broken and the mosfet dead, then IRF840 Rectifier, they’re broken and dead still, fast diode I used is SUF30J, the voltage input is 12v and 5Amp. Can anyone help me…

  27. With the ZVS flyback circuit of Vladimiro Mazzilli, if I place the 47-100uH in wrong direction, does it make the circuit broken and the MOSFET dead???

  28. Hello hanghuutri

    12VDC is too little, if the MOSFETs are driven with a too low voltage you can not control them properly and they will short circuit. You need to raise your voltage to over 20VDC to get reliable operation if you use the same source for gates and power.

    The MOSFETs used need a voltage rating about 4 times higher than the supply voltage and a on-resistance below 150mΩ.

    You can not place the inductor in a wrong direction.

    Kind regards

  29. Hi Mads Barnkob, a question, I see the circuit use mosfet without rectifier, I’m going to use the IRFZ44V, it’s seem compatible with the input voltage I use, but it’s a rectifier mosfet, is it ok?

  30. I mean that I see the zener diode symbol in the IRFZ44V’s schematic diagram, is it compatible for the circuit?

  31. Hello hanghuutri

    The reason for a external diode is that the complementary diode in the MOSFET is only a by-product from manufacturing the MOSFET. The ratings of these body diodes can be inferior and thus a faster external diode is used.

    Kind regards

  32. Thanks Mads, I finished the circuit and it’s run ok.

    But when I use the circuit as the induction heater, it’s failed when I winding the primary coil in disc-shaped.

    When I put a metal disk which need to be heated too near the primary coil (in disc-shaped), the mosfet get hot quickly and burned out while the metal disk doesn’t even get warm.

    When I winding the primary coil in tube-shaped, the induction heating is ok. Does anyone know what wrong?

  33. Hey hanghuutri

    Have you tried to calculate the different resonant frequencies you get with different work coils? That could be your problem. If you have cylindric coil that works, try to match its inductance and frequency in designing the pancake coil.

    Kind regards

  34. Hi Mads, I’m sure that I used the pancake coil with the same inductance.

    By anyway putting the metal too near the primary coil may be the reason (I think so, not sure),

    because I tried with a little longer distance (about 2cm) between the metal disk and the primary

    pancake coil, it work ok, but the heating is too slow, and performance is not acceptable… cry

    whole night 😀

    I have some another questions, after searching on Google, I don’t find one.

    1. What the maximum frequency this circuit can obtain? (I don’t have an oscilloscope :p).

    2. I’m going to use this circuit to generate powerful microwave, is this possible?


  35. Hi everybody again, please help me with replacement problem:

    On the success circuit: I used two mosfest IRF640, the fast diodes I used is SUF30J ( The coil L1 I used toroid coil (take from PC power supply), with inductance is about 100uH. It’s work ok, the mosfets are even not warm.

    On the last circuit I tried, I replace IRF640 with IRFB4020PBF which has the same Vds as IRF640 (200 Volt) except that it has lower total gate charging, lower on-resistance – (

    And the fast diodes I used is schottky diode MBR10100G (Vrrm 100 Volt) instead of SUF30J (Vrrm 600 Volt) – (

    Anything else is not changed, and the last circuit failed, the mosfets were too hot. Too low total gate charging cause the circuit fail? or fast diode I replace is problem? Any idea?


  36. Oh God, sorry everybody, I find out that I picked up resistors with wrong value.. new mosfet (IRFB4020PBF) and new diode (MBR10100G) is work ok.. my mistake.. 😀

  37. Seen some questions here.

    I’ve built many of those little pesky drivers, and it’s really a versatile little thing. I’ll add some useful information.

    As Hanghuutri asked, maximum frequency… I drove this circuit into the MHz range, using two IRF520 (very low gate charge) with low gate resistors, stopping at about 15V supply voltage. It was resonating on an air core, something like 3 turns total, with a few nF worth of capacitance as Tank (Polypropilene, good quality KP caps). That circuit worked at about 1.6MHz, but the gate signals were a little curved, not a good square wave. Well, even with such fast mosfets, the RC constant between charging resitors and gate charge was perhaps less than a tenth of the total period.

    Now on further info on this circuit.

    1) Gate Resistors. Adjust them, depending on your frequency, supply voltage, and gate capacitance. Their role is to charge up the gate fast enough after the feedback diode stops conducting, and therefore ram the mosfet into a saturation state as fast as possible. Many schematics offer a value of 470 or 680 Ohms. That is good for normal operation, 12-40V and up to perhaps an hundred KHz. If you scope the gates, you’ll notice if you need a lower resistance, as they’re charging lower than expected. On the HF design, I was running 120Ohms resitors on 15V supply, made of 4x 470r 1w in parallel, per gate. That kept the rise time decently low.

    2) Feedback diodes. If you want to ram your frequency UP, they have to be fast. No need for them to handle a buckload of current, because there won’t be much. They’re just discharging a gate, as fast as possible, into the opposite drain which has gone deeply negative. Normal 1A ultrafast diodes are OK.

    3) Fets or IGBT’s. As said, keep their breakage voltage at least four times above your supply voltage. five to be sure. Meaning, if you are crazy enough to build this circuit to withstand the 230/240V mains, don’t bother with anything smaller than 1200V rated transistors. Keep their connections to the capacitors and the trasformer’s primary as short as possible, and make sure there’s room for all the current they’ll have to handle. If you want to go crazy, some additional protection might come handy. This thing is literally a grim reaper for power transistor, when misused or brought close to its limits. Mov’s, perhaps an antiparallel ultrafast diode, or even some neon glow bulbs to protect from overvotlages might come handy.

    4) Resonant capacitor. Don’t ever underestimate this thing. pick good quality capacitors, made to sustain high RMS currents. Which means, possibly polypropilene, or anything similar. Don’t go for the crappy MKT caps, they’ll overheat and die quickly. Also there, use caps rated with voltages much higer than your supply, building them into MMC’s if necessary. Keep connections short, use copper foil if needed to handle large currents between the tank cap and the primary winding.

    5) Transformer’s primary. This circuit, makes the primary of your transformer into an LC parallel resonant circuit, which means, a buckload of current flows in. Use an adeguately thick wire, and expect it to melt mercilessy when you ram up the power. If you want higher frequencies, litz wire might come really handy, due to the evil skin effect lurking around in any RF design. Also here, keep connections between the tank cap and the primary as short as possible, as it’s where all the reactive energy is pushed around.

    If you have any more quesitons, just reply here. sooner or later I’ll try to reply. I’m build a solid state tesla based on this circuit, so I’ll post somewhere when it’s done. perhaps on 4HV.


  38. Hi , I have a problem, I am using IRFP460 MOSFET’s , byv27e ultrafast diodes , 17v zener diodes , and a .68uF microwave cap, the driver runs my Flyback at 5 amps 20v and 8 amps 50v but when I connect to my sparg gap tesla coil the current jumps to 20A before tripping my fuse , it regularly burns out zener’s , is it because 17v os not high enough, or because the tank voltage rises too high ? (almost 100V) . Does anyone have suggestions?

  39. Hello Dylan

    Could you post a link to a schematic, it sounds like you have a short circuit in order for the current to rise that high.

    Kind regards

  40. Thanks for the reply Mads, here is a link to the scematic from uzzors2k: ,
    I have modified this cuircuit a bit ( higher rated diodes and zeners for higher voltage and IRFP460’s , I dont know if the zener diodes keep blowing up because of the input voltage or the tank voltage…
    If there is a way to prevent that ( ive heard of people putting a 7812 regulator in for the gate drive ) I’d like to do it because it gets e pensive when the diodes pop and my mosfets short out…

  41. Are you sure that your flyback transformer isn’t giving out DC? SGTC’s are normally working from an AC supply, unless you run them in dc-resonant charging mode ( Also, in a normal SGTC, the transformer is shorted when the spark gap fires… meaning, you need a transformer (like a NST) capable of running short-circuit. This would be like when you draw arcs to ground with the flyback, rocketing power consumption into the high skies.

    Zeners should not blow up, perhaps are you overvolting your input? a fixed supply can be good, better 15-18V than 12 (for much quicker gate charging). Also, keep connections between the mosfets drains, resonant capacitor, feedback diodes and primary winding as short as possible, as you don’t want any possible stray inductance around that might shift your neutral potential up blasting your gates apart.

    Besides, there’s been some experiments by our fellow Tesla coilers on the italian mailing list, building a direct 4kW ZvS sstc, works quite well, almost to full line power (~200V ac, 280V dc in). Standard circuitry, 1200 or 1500/1600V Igbt’s and some crazy large mmc to hold the primary resonant currents. But, before jumping on such project, it’s rather advisable to come around the circuit and learn how to avoid it from tearing apart.

  42. Thanks for the info on DC res. Charging Andrea, I will try that, my tesla coil is indeed a DC coil, my imput voltage on the driver is far higher than 12 V ( close to 50VDC) and I am probably overvolting the input, but I will fix that with one of the 12V windings on my XFRMR so that the gate wil have about 15v DC and the tank will still have 40-50VDC supply, I think I should use 600v ultrafast diodes to keep them from shorting out when the tank voltage rises, my driver has no problem with an 8Amp draw , so im only worried about the zeners dying and killing the ‘FETs.
    Thank you for your info on the DC Tesla coil charging.

  43. Well, 50V are a heck of a lot of juice pushing into the little thing. If you kept resistors the default value, you are indeed frying your zeners rather quickly, mostly due to overheat. 470/680R are designed for 12-15V, at 50V or so you got so much current that your diode will just go boom and crack open. Then, the gate gets 50V, and well, bad fate for it.

    We did redesign this driver with a Flip-Flop / gate driver idea, if I find the schematic I’ll post it.

    I’d say it’s good to go for a separate power supply for the gates, keep in mind the RC constant (R as the charging resistor, C for gate capacitance), and that your gate will be up to 63% of supply voltage after Tau = RC, and to 86.4% after 2Tau. Keep that in mind to obtain a decent rise time on your mosfets, and switch them on quickly enough. But, as you said, I bet you’re around 20-50kHz, so plenty of room for quick gate switching.

  44. Its a lot, but it’ll handle it if you dont push it too much. I look forward to building the flip-flop 🙂
    Thanks for the info on gate charging, and I will keep that in mind because I want to build a small sstc using the driver , if I cant find a simpler way, I was thinking of using a d209l transistor wired for feedback oscillation (I think thats what its called) and run it from some high-ish voltage source to get oscillation. I dont think this is the place to discuss that further though, (it is a mazilli driver page after all)
    Your guess was pretty good, I run it at 60Khz for max power and I run it up to 160Khz for lower power operation, Thanks for the help and I look forward to a better ( and cheaper ) future for my driver !

  45. Great posts, very good feedback from a lot of experimenters. I was about to build a vandalism deterrent for my car, for the 2nd, full alarm I’d have a capacitive discharge type circuit that would give maybe 10 jolts for a second, then pause for a second or two, then repeat… and a ignition coil with high voltage output connected to car frame and a chain/link that drops down and contacts earth. Something to jolt the evil doer. This with it’s long arc ability interests me a lot. Any ideas on making a 12 volt, lower power (more primary turns) that will give a good spark but far less, non-lethal, current unit? How about using an ignition coil for the flyback transformer? It should give the high voltage but at less current. Ignition coils are not center tapped primary though, so a different version driver would need to be used, more like a Meisner oscillator, with a resonant capacitor across the primary. Any ideas… Comments… Feedback? Thanks.

  46. Hey Dan

    Do not use high voltage as a weapon or defense system, unless you buy a certified system. You will only risk putting the DIY community in a bad light if you hurt someone and tighter regulations might hit us.

    What good is a car that electrocutes people, which pisses them off and they throw a brick through the wind shield?

    Kind regards

  47. Hi Mads, Someone who is “electrocuted” is more than pissed off, that person is dead! Electrocution is always fatal. An electric shock isnt always fatal but would certainly make me unhappy! John.

  48. Hi John

    Hehe, I can see that results in a conundrum, I hope I can get away with excusing that English is my 2nd language 🙂

    Kind regards

  49. Hey Mads

    Continuing the discussion here:

    I applied five-minute epoxy to the flyback several times to avoid arcing, and eventually ended up cutting off all the unnecessary pins and covering the whole bottom in epoxy. However, the flyback only produced a tiny, barely visible spark anymore. So I figured it was friend internally, and obtained another transformer.

    This one produced a really nice arc that could be stretched to 15cm and it was hot enough to melt a steel electrode (1500°C) in ten seconds! The bottom pins did arc one time so I cut off the pins and covered the bottom in five-minute epoxy again.

    After that we got around 10 minutes of runtime. The voltage and power of the arc were decreasing all the time, and now it was just barely better than the 2N3055 circuit. We noticed that the tank capacitors were bulging noticeably.

    They were warm, but not hot to the touch; perhaps 50°C. The tank is made of three 0.22µF 275V MKP X2 caps in parallel. I measured the capacitance of the bulging caps with my cheap Chinese LCR meter and it said 0.2µF for the bank of three caps, so they are obviously fried.

    I didn’t know MKP caps could bulge. I guess they just weren’t quite up to the job? What kind of caps would you recommend?

  50. Those oscillator are hellish. What did you power the circuit off? I suppose 30V the least, giving the results. Caps are DC rated 275V, not AC. The resonant system will place about three times Vcc on the tank capacitor, which means, 30V in, you get 100v rms on the cap. A golden rule on those things, is oversize. critically oversize.

    Same circuit as yours, at 40V, I busted a 3.3µF 400V capacitor with quite a bit of RMS current capacity. Try to solve your circuit with a simulator, estimating the series resistance at a low value… you’ll get tens of amps running through your poor capacitors, which most likely aren’t rated to survive long periods of such torture.

    Go for higher voltage caps, build a small MMC, or switch directly to rail polypropilene’s intended for H-Bridge or inverter usage. That will ensure (most likely) that your circuit won’t massacre any more your capacitors. And, most importantly, while doing this, keep connecitons short, and use copper plate if you need big currents (remember skin effect depth at your resonant frequency).


  51. I’m actually powering this from a 48V 50A power supply. 🙂

    The caps I used are rated for 275V AC:

    But I guess the voltage tolerance is derated for higher frequencies. Also no mention of RMS current tolerance on that page.

    Do you have any specific capacitor models which you’ve had luck with?

    What is a typical resonant frequency for this circuit by the way?

  52. Hey ntoskrnl

    I agree with Andrea on this, the capacitors are not rated for 150VAC at properly some 100+/- kHz and the RMS current could be so high that they melt and bulge out.

    Take a look at the page about the Royer induction heater where this same circuit is described more in detail about ratings and some measurements.

    15cm sparks are also impressive and you are violently abusing a flyback transformer if you can pull some serious current from those 48VDC 🙂

    Kind regards

  53. Okay, I was considering something from the Cornell Dubilier 940C series. Their voltage ratings are plenty enough, and according to the datasheet they are capable of around 10A RMS at 100kHz. They are also used in Tesla coils.

    The question is, how many do I need in parallel? They are pretty expensive so I don’t want to go overboard. I can get

    – 0.1µF 1.2kV caps for 4.5€ each
    – 0.22µF 2kV caps for 8.3€ each
    – But then, 1µF 1kV caps for 7.6€ each.

    I wonder if a single 1µF cap would do it? It’s rated for 500VAC and 12.5A RMS at 100kHz at 70°C.

  54. Nice article! I have a question for Andrea if you’re still around the forums… I’ve went about your methods on making the zvs operate at much high frequencies for air cores and everything seems to be working fine… 260n’s, 5nf, 4+4 turns primary, and 32 awg on a 2 foot secondary, im not sure what its frequency is but its getting into the higher areas… Well anyways my main question is that its working great and staying cold, I can draw arcs from the secondary to objects grounded to me for around 4 seconds and then it starts to die out. The voltage input is 35volts and my smoothing bank is around 80000uf with full wave. Also when I crank up the voltage to 50 volts the breakout gets bigger but becomes “out of tune?” I tried replacing the smoothing bank with 50vdc caps but the 35vdc bank seems to work out better. Are the fets dieing from to much current? Is this a known behavior that you’re aware of? Any suggestions from anyone is also welcome! Thanks in advance…

  55. What resistors you use to drive the fet’s gates? A cause of failure can be the zeners being fried due to overheating, and thus getting 50v on the gates for a short time, but still destroying the oxide layer inside your mosfets.

    A zener diode typically goes short circuit when overdriven in the typical reverse bias configuration, but, before going short circuit, its reverse voltage rockets up, until it behaves for a short time as an open circuit. After a few seconds, the diode cools down, and it goes into a short circuit stage. That time that passes here, is rather enough to break your fet’s junctions.

    If you want to rocket up this driver’s supply, i’d suggest a separated rail (perhaps regulated with a 7815 or 7824) to keep a constant voltage on the resistor – zener voltage drivers on the gates.

    There has been a remake of this driver with logic (flip flops) and gate drivers to avoid cross saturation and gain a better stability on the italian high voltage mailing list, I’ll take a look through it if I can find it, I’ll post it there.

  56. Sorry Andrea I forgot to mention I have 4 1k in parallel for each gate and an external linear adjustable source supplying 15 volts capable of 20 amps for them. I went thru the period of frying my zeners to the point of knowing every resistance of every part on this driver for it to be working xD. Should I be able to just lower the gate resistance values? Are the gates modulated after this is squared away with say a 555? Thank you again!

  57. The driver a friend on the italian mailing list put together uses a flip flop to ensure correct oscillation, and most importantly, a pair of UCC37321/322 heavy duty gate drivers to pull the gates up in record time and avoid switching losses. I’m heading to work soon, will check now if I can fetch the schematic from somewhere.

  58. Hey Andrea

    Did you also see that he built a working unit from that schematic? I have tried building on myself with flip-flops and gate drivers, it worked but was very unstable and in the end it killed my MOSFETs. I scrapped it and would instead build a whole other driver topology for higher power.

    Kind regards

  59. Thank you so much Andrea. Mads I thank you for this forum too! I ended up going with wards mini sstc. It can be a monster if done right! But its just not enough!!! What is it, just cant get enough? Well i’ve decided to go full on dual resonant sstc. Thought maybe pll but why not skip and go drsstc! Never the less, the ZVS driver can accomplish loads of current in lots of different ways. Its worth seeing what all it can do. Not just center around a ferrite core. BUT we all know with a core this is the most stable way “so far” to have stable current at high voltage and very high frequency. Thanks again and to anyone else that ponders the world of hv “safely” and decides to share their discoveries!

  60. I got the 1µF 1kV cap I mentioned earlier and assembled the circuit again. It worked great for a little while until it just died. One of the FETs was shorted.

    I replaced the FET, and added a 180V TVS in parallel with the cap to absorb any overvoltage ringing of the choke with the cap when the arc breaks (I found this situation possible when I simulated the circuit).

    Now I got a bit more runtime with nice 10-15cm arcs, but the same thing happened again – a shorted FET. The flyback secondary reads around 200kΩ in both directions; I’m not sure whether that was there before or if there are shorted turns now. The flyback did arc a little bit to the core on the inside.

    Are my FETs dying due to the inherent instability of this driver, or do you think they died because the secondary arced to the primary through the core?

  61. Hi ntoskrnl

    I looked back at your previous posts and could not see which MOSFETs you use, I would say that your supply voltage is low enough to not damage a IRFP250N as it would only see around 150VDC from a 48VDC supply.

    As you supply can deliver all the current the circuit properly is able to use, the MOSFETs might simply die from die overheating due to too high RMS current? Could you measure the inverter voltage, inverter current and tank current like I did on the induction heater? ( )

    You are getting some good results with 10-15 cm arcs and when it arcs to the core you are punishing that poor little flyback way beyond its V/turn ratings 🙂

    Please upload a picture of your setup in the comment, you can do that now if its less than 2MB.

    Kind regards

  62. Great job! Mine is running on 50 VDC and a 0.68 uF tabk cap, my switches are 600v 30 A igbt’s, ive blown up many flybacks since! Works great as induction heater when you get the coil just right. Constant current draw of 10A on the DC side 🙂 mads, you have helped make a monster!

  63. Heres an image of the insides, it has 2 ups transformes wired in phase and series for +-40 AC, when rectifeid and filtered, its +-50vDC. Big ‘ ish heatsink, way overkill unless you use as an induction heater. 18v 1W Zenner diodes ( not sure of exact voltage) , and some kickasss Ultrafast diodes rated for 5A. Not sure of make or exect details either because i bought them on sale at a local electronics shop. Most important is all my cuircuit protection and a analogue Ammeter , up to 30A DC. Im thinking of using as a spark gap coil power source. I did not intend to make a very neat build as i was rushed by my exitement of blowing up flybacks 🙂

  64. Hey Dylan

    That sounds very interesting, very few people have had luck building this with MOSFETs or IGBT with a rating over 200VDC, due to differences in gate construction on higher voltage rated switches.

    Please tell which IGBTs you used and if you changed anything from the original circuit, except using iron core chokes.

    Kind regards

  65. Ive had a quick look and, they are g20n60b3d IGBT ‘s, I have not modifeid the circuit in any way, its still a standard mazilli driver, ps: those arent chokes – they are the 2 x ups power supply transformers wired in series to double voltage output to +-40VAC 🙂

  66. I am indeed using IRFP250N FETs.

    Neither the heatsinks or the transistors themselves heat up any noticeable amount, so I don’t think they are overheating. The FETs were also fine with another flyback, which died due to arcing.

    Unfortunately I don’t have an oscilloscope so I can’t take any measurements.

    Here’s a photo of my setup. The heatsink was an Intel stock heatsink which we cut in half. They are isolated from each other. The 200µH choke is pretty small physically, so I guess the core saturates at high DC currents; I’m not sure what effects that could cause.

  67. ntoskrnl, if i may suggest something – try a smaller cap to get the freq up a bit, in my experience, if you put a cap that size on a mazilli at 40+ VDC, its going to pop something, also , take a look at your zenner diodes, mine were the conventional 12v zenners untill i was fed up with continuously having to replace them ( it would literally burn the zenner in half) im using 16~18 v zenners, and, a bad zenner would cause a FET to fail
    Hope this helps, ive had lots of trail and error with this.

  68. Dylan have a good point in driving the MOSFETs harder with a higher gate voltage, but be sure to check the maximum zener clamping voltage so it does not exceed the maximum allowed gate voltage of the MOSFET. The IGBT Dylan refers to do also have a +-30V gate voltage pulse rating, compared against the IRFP250N only have a +-20V gate voltage rating. It can however be overdriven a little, to some 24V maybe.

    A lower switching frequency is better for the MOSFETs, they will spend less time in the linear region if the gate drive is a bit on the weak side.

  69. Hey Himanshu

    MUR1560 is a 15A 600V ultra-fast diode whereas the 1N4148 is a 0.2A 100V small signal ultra-fast diode. It is no good in this circuit with its low voltage and current specification.

    You should compare the continuous reverse voltage/current/recovery time when you try to find a substitute for the MUR1560.

    Kind regards

  70. Jeff Freeley

    Hello Mads,

    Thanks for all of your awesome work. Do you know if this circuit might work with a regular car ignition coil? I am looking for a way to create ozone generators and this would be a perfect option. To vary the output would you just change the voltage in?

    Thanks, I am relative newbie on this subject. : )

  71. Hi Jeff

    A car ignition coil us made with a iron core and might just saturate at the high frequency this circuit runs at with the usual component values. You would have to experiment with larger L and C values to bring the frequency down.

    You could also look at using a 2N2055 or TL494 driver instead.

    Maybe using flyback transformers instead could be a idea? They are easy to scavenge from old TV sets.

    Welcome to the high voltage hobby 🙂

    Kind regards

  72. Thanks Mads, I guess I am looking in the wrong direction for my needs. I am wanting to create a variable ozone generator circuit, so looks like ZVS is not a good way to go about it. There are a few 555 ignition coil circuits I can utilize, but also noticed some of the manufactures are using what looks to be some type of modified low output ZVS circuit because they are relatively silent.. (vs loud pulse of the 555 ignition coil drivers).. They are seem to be more efficient power wise..The potted one I have here looks to have 2 mosfets so that’s just my guess.. I don’t know enough about electronics to be able to figure it out, so my best bet is to stick with the old school 555 ignition coil driver circuits that do fit this application, or perhaps search for paid help from someone who specializes in this area of design.. : )

  73. Hi Jeff , From my experience the 555 flyback driver is the best way to go bothfor power and frequency adjustment ( for low power / high corona discharge).

    A zvs driver is very finiky and if you may not like to replace your mosfets every time you change something. Also it may be way too powerful for simple ozone generation.

    I have attempted a ion propulsion unit with both a zvs driver and a 555 flyback , and the zvs driver kept on arcing to my other terminal where the 555 kept a nice and steady corona discharge.

    An iron core tranfomer (ignition coil) runs at a low frequency(10Hz ~ 1kHz) -which is why it is so noisy- where the ozone generator you described seens like it would be ferrite core ( 20Khz +) which is why it is “quiet”.

    I would be happy to assist you any further if needed. But please note – I am no expert 🙂

  74. Thanks Jeff! That is helpful, I appreciate it. I will keep looking around to see what I can find, Cheers!

  75. I finally got back to this. I rebuilt the circuit on a piece of stripboard, and attached the MOSFETs with screw terminals so that they can be easily replaced. No MOSFETS have died so far though.

    I tried with a lower voltage this time, first 24V and then 36V, rather than the full 48V. My SMPS based power supply doesn’t sag under load, so this is probably more like the unregulated transformer/rectifier power supplies many others use. I also avoided breaking the arc as the FETs usually died when I did that.

    The circuit works very well now and can melt the tips of steel electrodes. We had several five-minute runs as well, including one where we put the electrodes in a glass jar and taped it shut. The arc produces nitrogen dioxide, and after arcing for five minutes or so and letting it sit for a while, the air inside turn distinctively orange-brown.

    After long runs, the flyback secondary gets pretty warm, I’d say about 60–70°C on the surface of the transformer. The 2.5mm^2 primary also gets warm. The tank capacitor and 0.75mm^2 input choke get slightly warm to the touch, and the MOSFETs get perhaps a few degrees above ambient.

  76. So , ive got myself interested in the ZVS driver again , and dig out my old build. I never really got decent induction heating power from it and was curious about what i could do to improve.

    It runs off of ~46 VDC and will trip a built in fuse if current rises above 10A on the DC supply. Im using IGBT’s ( which ive been told is a rare feat with the mazzilli driver ) rated at 600V 50A ( if memory serves ) .
    I have 18v Zenner diodes and i cant remember which the ultrafast diodes are.
    Tank cap is a .68 uF 1200v microwave capacitor.
    Work coil is (currently) 8 + 8 turns of 1mm magnet wire from a microwave tranformers primary.

    What could i do to improve performance and also get this thing to not destroy 50 bucks worth of IGBT when i bypass the tripswitch?
    (It can run a flyback indefinitely @ 8A with no heating to IGBT’s,and it can make a 8mm stainless rod turn orange within 18 seconds @ 9A ) Im afraid to push it harder without modification because of the instability i had experienced when building my first ZVS driver.

    I also want to remove the centre tap and add another inductor instead, for the ease of making a decent coil.

    Also , what can be done to increase output voltage of the flyback without pumping more juice into the DC side ? Ive seen folks with a driver 1/3 rd the size of mine running 150Kv arcs ( mine can currently put out 70 ~ 100Kv before it trips by tripswitch ).


  77. Hey Dylan

    If it is possible, try to use a primary coil with a larger gauge, or parallel some more magnet wire to have a lower resistance and lessen skin effect.

    Fewer primary turns will give you a bigger output, but also increase primary current and vice versa for more primary turns.

    More turns on the secondary side will also increase your voltage output.

    You could increase the capacitor size up to about 2-4 uF.

    The ZVS driver is by nature not very stable, it will suddenly explode from hardswitching large currents or overvoltage. Remember that the switches in a ZVS driver sees pi(3,14) x supply voltage.

    Kind regards

  78. Thanks mads.

    I think the main issue is my capacitor that is too small. Its a .68uF microwave cap, that gets fairly hot after a bit of running.

    I took the weekend and decided to rebuild it and totally bypassed the 10A Tripswitch.

    I wound a work coil with 7 turns 8mm copper tubing and am using high current wire on all connections , it will draw 25A now without a hitch @ 48vDC but im not able to heat anything up to the point where it starts to glow.
    The tank freq is 115kHz and tank voltage is around 100v.

    I am under the impression my input voltage is too high, but im also unsure of what freq the tank needs to be for more heating power.

    Im not sure how to measure tank current but i will do research on how.

    In flyback mode with a 5 turn primary it will draw 15A @48v and 10A @ 20v , produces thicker, hotter arcs now , but no noticeable voltage output
    ( i measure via air breakdown voltage, 10cm is the point at wich it starts to arc).

    Is lower tank freq better for induction heating ? ( i was thinking ~60kHz ).

    ^^This is a photo of my current setup

  79. Hey Dylan

    I can see that you are still using a microwave oven capacitor. You should replace that with some metallized polypropylene capacitors .

    Without water cooling of the work coil, be sure to watch that it does not get so hot that the plastic container melts 🙂

    Kind regards

  80. I modified the work coil , it worked extremely well, and then my microwave cap exploded XD.

    unfortunately it blew up my IGBT’s as well, ill be making an mmc and hopefully i can achieve decent output.

    the 50A high current cables hooked up to the cap got incinerated too,.

    Ill be using new 900v 51A igbt’s made specifically for SMPS power supplies, they should work well.

    If i destroy anything else ill post an update 😋

  81. Hi everyone,
    I have just wandered around the internet for a week.And i saw this circuit yesterday.
    I have some question about the circuit, can you please spend some time answer them.
    First, I see everyone there is blowing up a lot of mosfet.Some blow up very ramdomly.
    Is there anyway to stop them from blowing?
    I will build the circuit but i won’t use irfp250 (it’s very expensive, each mosfet die cost a lot).
    instead can i use irf640, probably yes but i think that it will handle only half the amount of
    amp the irfp250 can.
    Can you suggest a good starting voltage for the circuit?A current-limited power supply will
    be good, i think.
    Thanks in advance ,

  82. Hello Sieu

    Supply voltage lower than 9-10VDC will gives problems with MOSFETs not switching and one will latch up and a short circuit will destroy the switches.

    The supply voltage also have to be atleast 3.5 times lower than the maximum rating of the MOSFET.

    Be careful not to use a expensive current limited power supply, you do not wish to destroy it from a poorly set up experiment just to save MOSFETs for a few dollars 🙂

    Kind regards

  83. Hi Sieu, i would like to add to mads’ comment.
    The irf460 is suited , but a little lacking in current handling capability. However for a low power application it should work great ( I started out using them) . Keep in mind that the main reason my MOSFETS/IGBT’s explode is due to circuit failure or the tank coltage rising too high.

    Start off at 12~ 15v ( alarm batteries work well, or a car battery if you have one laying around).

    Your tank cap should be suited for between 40kHz and 120kHz , just keep an eye on the tank voltage.

    Good luck and happy building 🙂

  84. Hi Mads and Dylan,
    Thanks for your fast reply, i have read your reply since 22/10 but only today i have some time to buy stuff and wire it up.
    Ok so i have soldered everything on and prepare to power it using the big car battery (100AH 12V) on the right of the picture.
    I’am facing a problem: I don’t have a high voltage fast diode.All i have are 25,40,60,100,200 volt schottky diode.I have no 600v or similar diode. I’am living in a rural area in VietNam so electrical shop sell very little part, they don’t sell UF4007 or any fast diode.All they have is IN4007 and it’s higher amperage parts with similar switching speed. Do you thing i should search for broken parts (TV, PC PSU,.. ) to get the part? I will have to go to a local scrap store>?
    Near the battery is a inductor i want to use for the driver, will it work?
    The tank capacitor is 0.55uF made from 16 MKP caps to completely remove the heating.
    Other than things above there is no change from the orginal circuit.
    Please help!

  85. All seems well with what you described. Old tv’s will have usefull diodes on the board you can use.

    just make sure they are ultrafast diodes, at 12v input you will see around 4 times more volts over the tank cuircuit, 200V 2A Ultrafast diodes should work, but if you find a BYV-26 diode or similar in a tv / pc monitor it will work 😉

    Good luck and happy building

  86. Double comment,
    I heard about Dylan is building a IGBT mazilli driver.If you have already finish it please post it in youtube so everyone (include me) will believe that there’s one such driver alive and working!
    An 1200V IGBT will serve you well, maybe even giving an opportunity to power it directly from main voltage (do you have 110V mains?) by wiring the driver in series with 2 microwave transformer with their secondary shorted.It will (somewhat) limit the current flow in the driver and (hopefully) it won’t blow.And use a separate power supply for the gate, ground the negative point.
    The flyback core losses is huge with 48V input, makerj101’s video show that he just put it in oil but i think there’s must be other solution.Such as find 5 same tv, take their flybacks.Remove old primaries and secondaries, wind a new primary and secondary for each core (they must all be the same) and then wire them in series and finally put all the assembly into oil.That would reduce core heating (for 60 volt input each primary will see 12volt across it (5 flyback in series will produce some crazy voltage, if each secondary is designed so that it would output 20KV for 12V input then 20*5= roughly 100KV output). If you design the secondaries so that each secondary produce 30KV it would be around 150KV, too enough to make a huge arc! In that case i think you should need a 20+ amps power supply at 60 volt.
    That all my idea, i hope you will find some use for it.

  87. Its a plausible idea , But my flyback already puts out 100 ~ 150 kV. It runs 48V DC @20A when under full power. I dont know if ballasting with Microwave transformers will mess with the frequency, which is usually at 60kHz.

    The mains voltage here is 220V so running it off mains is not something ill be doing any time soon, although my Solid State Tesla coil runs off mains. Right now im busy rebuilding my sstc 🙂
    I can convert it into a Induction heater just by connecting a work coil to the driver, then it starts drawing 30A +

    I bought a jar today , which i will fill with oil and put my Flyback in it 😉 then i can use it for electrostatic experiments without arcing over.

    I use TO -220 style IGBT’s (the three pin type) for most of my high voltage devices- of which i have only two XD .

    Great idea though , but i wish i had the time and money to rewind five 30Kv flybacks .

  88. Hi everyone,
    I have successfully build the circuit, and it make a 1cm arc with fat (fatter than 555 timer arc!) with purple arc. The mosfet i’am using is irf640 and it is powered by an 12v 10AH car battery (the battery is pretty old,it has been taken from an truck since 2013 and not used till yesterday).
    Now the circuit is working, i’am not really happy with the current results.So i will modify an MOT for 24 volt soon. The IRFP250 is not available at this place so i will use 2 pairs of IRF640 wired in parallel so they have the same rating as a pair of IRFP250.Currently i have 3 of these mosfet but i will buy more soon.
    I think 3 pairs of IRF540 at 15v input will be funny, the amp draw should be near 30A.
    I have posted a picture about my homemade winding, i will tell how to make one as pretty as mine:
    First, find an WHITE PVC tube that fit your core, cut it so that it length fit your core, then wind 1 turn of enameled copper wire (thick wire, this is the primary) on the tube and superglue it on the tube. Process to wind 5+5 turns center-tapped, then superglue the last turn into the tube.
    Then, superglue 2 corner of a plastic sheet to the winding, the sheet must be a slight wider than the tube but not too wide.Then roll the sheet around the tube for 2 times then tape the sheet together.
    Roll 3 more times for insulate between the secondary and primary.
    Process to wind the secondary, using an thinner wire, follow the process above until your core completely fit the old core.
    Use a hair drier, or a gas cooker to liquify 100 grams of paraffin wax (candles, please use an white wax so it look good!The mass of the paraffin could be changed.)
    Put the whole assembly into the liquid paraffin, and let it there for 5 seconds, then quickly pull the assembly out of the wax!Please be fast or you will melt the plastic!Finally let the assembly to cool down and install it to the core, there you have a nice winded transformer.Heat have tighten the winding and insert paraffin between spaces of the imperfect winding for us!
    Thanks anyone for help me complete the driver.

  89. excellent sieu , glad to hear yours is working.
    If you want stronger MOSFET’s you should find some nice ones in old pc power supplies, as well as crt monitors.

    If you keep tank voltage below 200V then youre good to go. The ZVS driver typically puts out 3.14 × input voltage , so lower than 60v input should be fine – but you will probably destroy the zenner diodes or the gate of the MOSFETs 🙂

    A rewound MOT is an excellent idea and should greatly improve performance.

    Good idea to wind the primary on a former and insulating it.

  90. Hey KhaSieu and Dylan

    Good results, all you need now is a higher supply voltage or more secondary coil windings for getting longer arcs. Be careful with the old battery if it running flat, below 9VDC you risk improper MOSFET switching and they can short circuit.

    Is it not possible for you to order MOSFETs on ebay and have them sent to you? There should be little difference in me ordering from China to Denmark compared to China to India.

    Kind regards

  91. Hola amigo me gustaría saber si se puede usar 2 MOSFET diferentes uno del otro.porqué no tengo los irfp250.pero si tengo otros iguales y asta mas potentes. Solo que no los tengo en pares.gracias.

  92. Hello Mads and Dylan,
    I have modified an microwave oven transformer and got very decent result out of it, but do you notice that the primary winding got too hot to touch after 1mins of operation>?.I measured the core loss when the transformer is unloaded, the loss is calculated to be huge,around 150W in my case.Do you use active cooling for the transformer?Even with active cooling that is very lossy so I feel the need for an fully stable transformer, around 14V (for diode drops) and 10+ amps output.I have prepared the material for it.
    After all it worked, that fine but i know such transformer are an example of the “economic saving”.The core was tiny,the windings made from aluminium, and used maximum flux density.It will soon fail without oil immersion, so i recommend not to use it.

  93. Hi sieu, you could add a ballast or choke in series with the transformer, i have not yet had the oppertunity to modify one so my knowledge on microwave transformers is not good.

    If you find an old UPS , they have nice 15V transformers inside – can output up to 100A ( i measured it with a clamp meter over a dead short), so im impressed with it.

    People tend to throw them away when the battery dies, so ive gathered three already.

  94. Hey Sieu

    If you can find space in the winding windows of the transformer, add some more primary windings in series of the existing primary coil, as is its being run at about 1V/turn and as you already stated its running on the brink of major saturation. Lowering the V/turn ratio could help on that.

    Kind regards

  95. Hello Mads and Dylan.
    The core was made as small as possible, so the transformer rated for 800w is just an ordinary 300W transformer. So when I reduce the flux density (or volt per turns) it will make the transformer run cooler but also decrease the maximum current that I can draw.
    Do you notice the transformer have a different construction than normal ones? The e lamination stacks on each other and so does the I lamination, then they are welded together. And even this transformer have a magnetic stunt act like an current limiter. Adding a inductive choke in series with the current transformer just dissipated the heat equally between the choke and the transformer, that is not much different than adding 200 turns to the primary (it will run at 1.2 tesla in that case).
    So Dylan, how heavy is that transformer? The driver will never runs like a short circuit wire, it’s resistance will be more than as least 0.5 ohms plus the resistance of the mosfet.So it will need more voltage to runs at higher amperage(30amp max with 24 volt input).

  96. Hi Mads and Dylan,
    I found a cheaper ways of getting a power supply. Yesterday I bought broken Chinese power supply (pc psu) for 1.5$. I have opened it to see what is broken, by replace the input capacitor pair which is suffered from capacitor plague i am able to get it to work again. Now I have 22 amp 12 volt psu for 1.5$ plus 1$ for adding some emi filter capacitor and inductors. The psu is rated for 500w but for Chinese one I will just draw 300w at most. The arcs are 2.5 cm now and hot enough to melt wire in an second or so. Unfortunately I make a stupid mistake by pull the hv wire far apart from each other (the 2rd time I make this mistake), so far I have killed 3 mosfets. Let’s find more psu and fix them then try to put them in series to get 24 volt.

  97. Hey Sieu

    It is great to hear you have some progress, you might find that computer power supplies are not that easy to just put in series as they loose their reference points in regard to ground. You need to remove the ground connections to the power supplies so they become floating power supplies and they can be connected in series.

    Kind regards

  98. Hi Mads,
    The atx power supply have a nice features that I think it is suitable for this driver than the transformer. The internal short circuit protection seem very helpful, when a mosfet in the pair got shorted the supply immediately cut off the power so the other mosfet will be saved. As for the transformer there is no overcurrent protection so when one got fried the other also got fried.So I saved one of my mosfet, please add a overcurrent protection circuit to the driver circuit.It is very hard to get it done but if it could be implemented it can guarantee the stability of the driver and save a lot of money and effort. That can be very time consuming to design such an circuit but the effect can overcome the time put in it, a lot of DIY community member will benefit from such protection circuit.

  99. Hey Sieu

    There are much better circuits to build if you want over current protection, f.ex. adding it to the TL494 driver. The ZVS driver is just inherently unstable when pushed in either too low or too high conditions and there is no reason to build safety features unto something that is broken instead of moving to a better design 🙂

    Kind regards

  100. Hi Mads Barnkob,
    I understand the point and won’t waste my (and anyone) time. Overall the zvs worked very well in low voltage regimes (12-60 volt) and that OK, the efficiency is very good (expect for the 12v power supply).
    And there’s a small trick: if you use PC PSU (Chinese type that use TL494) then connect the red wire of the audio jack to pin 1, white (or black) wire to gnd and plug it in a audio source 🙂
    Here the perfboard version of the zvs.

  101. Hi Mads Andrea, I’m new to this circuit but made one (several actually) using the standard components given – ie IRFP250s etc tried with several different flybacks, both recent and vintage, and 12 volts from lead acid battery. However my arcs are tiny if at all and it is only when I strike the arc by touching the wires and then move the wires apart that I can get it to extend to 1 cm if lucky. Current draw is less than 1 amp when no arc; goes up to 4 amps with arc after touching HV wires. What am I doing wrong? Should I increase the primary capacitor – currently at 0.68 – or is the voltage too low. Primary turns are 4+4 solid PVC covered or litz. Maybe environment is too damp – done in shed in London in winter!

  102. Hi andrew , It would appear either input voltage is too low or you res freq is too high, If you can measure what the frequency is, (over the capacitor) and its over 100Khz you might need to increase the capacitor size , dont go over 1uF though.

    If you cant measure frequency its not an issue, just try feeding it more power, eg car battery or even a car battery charger, If you can, push for 15v , the supply needs to be able to provide around 10A , and if that does not improve output , try adding more turns to the primary, anywhere between 4+4 to 10+10 would be suitable.

    If you here a whining noise (25Khz or lower frequency) you should reduce the number of turns on the primary slightly, or make the capacitor smaller, but smaller capacitor means that it wont be as powerfull or put the MOSFETS under more strain.

    Hope my info helps !

  103. Hi Andrew

    Did you check the battery voltage when you are drawing arcs? It could be that it is a weak battery or needs charging. 12 Volt is about as low as you can go with this circuit, below 10 Volt it will not switch efficient at all and therefore the thin sparks could be caused by that.
    I do not think your environment is the problem.

    Kind regards

  104. Hi Mads, Dylan,
    Many thanks for your advice and recommendations.
    Frequency meter indicates 22kHz for 2 of my units, over 45kHz for another – all without arc. Once an arc appears, after bringing the secondary wires close enough, frequencies shoot up to over 150 kHz in 2 of them and over 800kHz in the other (perhaps due to feedback from the arc to my frequency meter?) One of the 22kHz units is a ready made chinese unit with standard components (ebay for about £6). The only difference with the 3rd unit I made (the one giving high frequencies ) is that the gate resistors are 43o Ohm, the cap is 2 x.33uF mylar in parallel , the mosfets IRF540N and the flyback is quite small (unknown provenance). All primary turns are 4+4 pvc covered single strand copper house wire – about 16SWG. and in the other units IRFP250s and 0.68uF polypropylene caps.
    Increasing power to 24volts makes a big difference in activity, though still not great, and the measured frequencies across the primary all double! I have checked and rechecked the circuitry of the unit giving the anomalously high frequencies but cant find anything out of the ordinary – maybe this flyback is made to run at higher frequencies?
    Any comments and suggestions more than welcome.

  105. Hi again,
    Formerly to obtain HV with an ex vintage TV flyback, I used the well -known simple self-resonating circuit with 2-3 turn feedback windings on the thicker 4+4 t primary windings, with a 10 or 8-1 voltage splitter on the center tapped feedback windings cross connected to the bases of 2x 2N3055s or similar – transistors with no caps or anything else. Worked very well with good arcs, but subject to quickly overheating and needing pretty hefty heatsinks for prolonged operation. I was looking for a more stable and efficient system in the Mazilli setup.

  106. Andrew , good to hear that voltage increase improved performance. And now i think that it might help to add some windings , because as soon as an arc is started the res frequency should (from what ive worked with) not exceed the resonant state of the flyback, however all flybacks have different resonant frequencies, however 800Khz seems quite high for a flyback which is usually between 27Khz ~ 200Khz.

    Adding more turns will drop the frequency slightly (only add 1+1 turn at a time to check for changes , it is painstaking but it will prevent a blowout in most cases).

    Adding a higher voltage should effect the frequency , because it will be charging the tank cap faster than the lower voltage would.

    I also started out with the 2N3055 driver , which was quite a terrible thing conpared to a mazzili driver, but hey… gotta start somewhere.

    Also keep an eye on the current draw while you’re testing for what amount of turns to use. A high current draw with no arcs or a whining noise indicates an issue. Although i did make a flyback designed to resonate at 18KHz once ,No flyback should whine due to its design to operate above the human hearing range.

    Best of luck , and im more than happy to help !

  107. Follow up, Andrew could you tell me what voltage your zenner diodes are ? I doubt they are the cause but im just checking possible issues. In a mazzili driver you will get great efficiency and it will be quite reliable ( if you dont feed it too much / too little power).

    The mazzili driver loves to blow up zenners and lock up causing the mosfets to blow, but only when driven overboard. I’ve never had one fail for any other reason than me giving it too much power , and due to a blown zenner diode.

  108. Hi Dylan,
    Many thanks for your comments . I will see what an extra turn does and check the amperage (currently this was very low with no arc, but shot up with arcing – once an arc was pulled, wire tips burned and melted the plastic insulation in a few seconds).
    My zeners are all 12 volt – I’m using 5 watt or 1 watt depending upon the unit).
    The kind of arc is quite different between the 2N3055 inverter and the Mazilli ones.

  109. Hi again,
    I have tried to convert a couple of my old flyback resonant units (using 3055s) to mazilli but with little to zero success. Arc length, even at 24 volts, is reduced to a fraction of what it was (at 12 volts) in one unit and in the other there is just no oscillation at all – zero output (I am using the ready made Chinese unit as a Mazilli driver in both cases. In both cases the flyback cores are from vintage tellies, probably black and white, and it may be that the ferrite used is quite different, maybe only working at much lower frequencies, from what it is today, so just doesn’t work at the component settings of the current mazilli circuits. Perhaps increasing the primary turns and/or increasing the value of the capacitor to 1 or more uF would be the way to go?

  110. While a 2N3055 *might* work , it is a completely different kind of transistor than what is needed in a mazzili driver, (MOSFET/IGBT’s are the best choice for a mazzili).

    The only other thing i can think of is that the current your power source can supply is limited, however with 22vdc you should see a 6A + draw (depending on primary coil and operating frequency) . There is no safe way to test the max output current of your power source other than a specialised load tester that battery centres use.

    At this point i would suggest increasing tank capacitance , but dont increase primary turns yet. Try 1uF , then 1.5uF as a start, i wouldnt go over 2.2uF yet. This is just so you dont accidentally destroy the driver (It doesnt like drastic changes to components- i once switched the primary without adapting the cap for impendance and it popped my IGBT’s 🙂

    Best MOSFET to use in my opinion would be irfp250 or irfp460 (though 460 is overkill unless youre going over 40V input voltage).

    Could you post some images of your flybacks and/or driver + connections ?

    Make sure to have thick wire for the primary coil .The “house wire” you mentioned earlier, was it twinflex or the solid core stuff used in wiring for mains (generally 10A rated)? I have seen that twinflex cables (for 220V /110V recycled from broken appliances) can have an unusually high resistance, probably due to age.

    When i ran my IGBT ZVS on 50VDC i had to have more than 15 primary turns to stop it from drawing over 30A (Over 40A @ 60Khz means my IGBT’s explode ).

    A note for you in future, if you up the supply voltage past 30V make sure to have 16V zenners rated at 2W + , unless you have very beefy 12v zenners.

    Best of luck !

  111. Hi Andrew and Dylan

    Dylan covered about everything. He is faster than me 🙂

    There is a huge difference between transistors and MOSFETs/IGBTs (that to some degree is interchangeable). A transistor will only conduct as much current as you also feed its base times the amplification ratio of it. This is why it might oscillate, but not conduct any current worth mentioning.

    Kind regards

  112. Hi Dylan and Mads,
    Thank you for your responses. A bit of confusion here – I was not attempting to substitute the 3055 transistor with a MOSFET, just that I wanted to change a 3055 transistor – based inverter to a Mazilli , the latter being a more efficient and reliable circuit. However I am having a problem using the old style ferrite core of the TV flyback, as it refused to oscillate with the Mazilli, so I was wondering how this might be adapted to run the inverter – thinking that increasing the primary turns and/or the capacitor value might help, given that it needs to run at a lower frequency.

  113. Further to Dylan’s comments – the primary is 2×4 turns single core new house wiring, must be about 16SWG, or thicker. The current source is sufficient – an old lead acid golf cart battery still giving 12.5 volts at 5 amps drain ( but I will now try my 24volt mains power pack which has a 12 amp rating) Mosfets are IRPF250s, zeners 12 volt, 5 or 1 watt – I have 2 units. I shall upload some pictures soon. IMO Mazilli’s seem to be much more tricky to set up satisfactorily than I had anticipated – the circuit values published seem to refer exclusively for use with the most recent kinds of flyback cores, older ones just don’t seem to work right.

  114. Hi Andrew

    I see, you were changing the entire driver and not trying to make some hybrid of the two 🙂

    From my experience I have seen no difference in using a 2n3055 driver, zvs or tl494 on any of the flyback transformers I have, they all worked fine, so I am not sure what kind of problem you are facing.

    I can only think of either drive frequency is too high or is there a large air gap in the core?

    Kind regards

  115. Hi Mads,
    Thanks again for yours and Dylans advice.
    I believe my problem had been a short in the secondary winding – there seems no way one can test for this easily – I would have thought that this would have given rise to excessive current draw but this did not happen with the Mazilli although it did with the 2N3055 driver set up – although I have found that the latter always heats up and needs large heatsinks even under normal working conditions.
    I have tried to use alternative mosfets to IRPF 250s and 450s in Mazilli inverters – but these have not worked as well and have quickly heated up or blown.

    One query – when working for more than a very short time , should one allow the secondary to open circuit or should it always be striking an arc – ie consume some power? I have heard that under open circuit this puts too much strain on the secondary insulation which can break down. Perhaps a multi megaohm resistor across the HV output is the safest option.

    Kind regards,

  116. I leave mine Open circuit sometimes , but then i get arcs coming off the core to my primary , most times my IGBT’s survive but i have had them short out due to this. There is a possibility that the isolation could fail due to corona buildup in the secondary, especially in older transformers.

    It might be better to try out your mazzili driver on a newer flyback, you can buy one from a tv repair store or salvage one from an old CRT computer screen ,bigger the better 🙂

    Keep in mind that if your driver is resonating too far above the flyback’s resonant frequency, then the mosfets will get hot and you will not get output.

    a good way to see whats going on is to measure the AC voltage across your tank cap , as well as the frequency when you power it on (use low power for this to make sure everything is working before you crank it up ).

    measurements should be done with output open circuit.

    – the tank voltage should be about 3 times input voltage ( altgough anything from input voltage to 4 times input voltage can happen)

    – The frequency should be anywhere between 25Khz to 250Khz (depending on transformer)

    Note that if your tank voltage is low and current draw is high, you either need more primary turns (its basically short circuiting) or smaller tank cap (between 1uF and 0.2 uF should be a good starting range).

    If your tank voltage is high but you have no current draw, then the tank cap is too small or your primary has too many winds, its easy to check which is the coulprit.
    Measure the frequency, if its high then your tank cap is too small and if the freq is low then you need less primary turns.

    Hope your mazilli lives up to the effort you put into it , it is the most robust driver i can think of for its simplicity.

  117. Hi Andrew,
    I left the output of the transformer open circuit once, and it didn’t blow up the mosfet. However I chose to draw the output further and around 5 cm far from ground wire, the mosfet blown. It must be the voltage in such an open loop is too high for the mosfet to survive. You can pull it as far as you don’t go over the maximum rating of the mosfet, I suggest leaving the gap as most as 1.5 times the maximum arc lenght, although the mosfet can still blown below this level.
    Especially when you power up the circuit you will want to be sure that the gap is small enough so it is arcing before pulling the wire apart.
    Best luck,

  118. Hi saattvik

    With a low voltage it would be better to use IRFP250N or similar. With this ZVS circuit you do not really control how much current it draws, if your supply can only deliver 10A, there is a great risk it will overburden the power supply, pull the voltage down and your MOSFETs explode due to not switching properly at the low voltage.

    Kind regards

  119. Harsh Dwivedi

    Hi Mads,
    I m from India,
    I replicated ur ZVS circuit but i have some issues with it,
    its specs r-
    {18-0-18 transformer , 3 amp diodes ,2200uF 50v polarized capacitor }-for a DC power supply
    IRFP250N, 200uH non toroidal inductor, and the rest everything is same.

    everytime i switch the power on the inductor and the first 470ohm 2W resistor start to heat up and even the 18-0-18 transformer gets hot.
    the dc supply works great unless connected to the zvs.
    Can u help me with it.
    and if u cant here plz gimme ur contact details.

  120. Hi Harsh

    It sounds like you have a short circuit, revise your circuit vs. the schematics again. It could also be defective MOSFETs.

    Kind regards

  121. Harsh Dwivedi

    Hi Mads
    I did revise the circuits and i found out that the inductor was faulty.
    now i replaced it
    connecting the rectifier makes no short-circuit until the flyback is connected to the driver
    connecting the flyback makes the same problems, heating the 18-0-18 trans. and the inductor
    in think there just a bit more of problem, i just cant figure it out


  122. Just letting you guys know an important fact about ZVS drivers. They do not like it when the power supply slowly increases from zero to its rated output voltage, which is typically what happens when a DC power supply is turned on. That could cause a condition in which both FETs are conducting at the same time. It is preferable to leave the voltage source disconnected from the ZVS driver while turning on the power supply, and then after a second or so, connect the power supply to the ZVS. The fast risetime voltage will ensure that one of the FETs will conduct before the other one does, and oscillation will then start.

  123. Hi everyone. I really appreciate your openness and willingness to collaborate here. The information has been extremely helpful for me!


  124. Hi LeoD

    I would not omit the zener diodes, there can still be switching spikes which are voltage transients that are high enough voltage and have enough energy to damage the gate of the MOSFET.

    Kind regards

  125. Pingback: Power Circuit Driver | Voltage Electricity

  126. Hi lahor

    It can properly run down to some 5-10 kHz, not that I have tested it, but its an assumption based on time needed to switch state. I would however not build something that switches below 20 kHz, as it gets in the audio range of what we can hear. 10 kHz high current switching is not something you want to listen to.

    Kind regards

  127. Hi everyone I managed to get double the output from my circuits with 2 flybacks hooked up in parallel to the zvs and the flybacks output in series. It’s down right scary.

  128. Hi Mads Barnkob,
    I read in one of your replies that supplying 12vdc or less it’s not enough and it will result in shorted mosfets. Do you think that a 4s/3s li-ion battery pack ( Sony vtc6, 3000mah, 30amp in series) its not enough? And if not could you recommend me an alternative setup that can be used with this batteries?

  129. Hi Petr

    The most important thing about the power supply for this self-oscillating induction heater is that the voltage never drops so low that the MOSFET is not switch completely on/off. So you just have to add enough batteries in series to obtain at least 12-15VDC.

    Kind regards

  130. Hey Mads, just a quick question, what do you think of irfp4668pbf? can it be used instead of irfp250n? If yes do I have to change the gate resistor for faster charge?

  131. Hey Petr,

    the original schematic is now a few years old, and the mosfets were what was easily available at the time.

    The IRFP4668PBF can be used, but seems to me a not-optimal choice. Besides the very low Rds(ON), it has a low-ish V(ds) at 200V which restricts you to work up to 40V supply safely (tank voltage goes PI*Vin) and most importantly a huge gate capacitance of 10,7nF (compared to 2.3nF of he IRFP250) that will make more difficult to achieve a good square wave on the gates. In this condition, either you keep the frequency low, or you go to much smaller gate resistors to be able to pull them up in a reasonable time (like 150-220 ohm or even less). Keep in mind that smaller resistors do require zeners to be sized accordingly to avoid blow-ups due to overheating.

    If you have them for free, try building one. If you need to buy them… search for something with an higher V(ds) and most importantly a low gate charge. Low R(ds)ON is not crucial, even a 0.2 Ohm device is fine for most applications.

  132. Thank you for your advices, I actually have both them but I thought that the irfp4668 can handle more power. Anyways what would be your 2020 approach of a similar oscillator? Would you use a microcontroller to drive the mosfet?

  133. I feel there is no need to use a micro-controller on a circuit like this. It thrives on its simplicity, and I wouldn’t add unnecessary things or external systems controlling it.

    Check this post for a different version of the driver >>

    this is the driver rebuilt by Diego Barone using a 4023 and a couple gate drivers, it allows easy powering up of both the gate drive logic and power section from two different rails eliminating zener blowup issues that can occur at higher supply voltages.

  134. For the scientific part of this device one should mention that the ZVS drive works in two modes, current mode and voltage mode. In translation : more capacity means more output current and less capacity more output voltage. So for a induction heater you will need some beefy capacitance and for a HV driver you just need some zecimal values like 0.1uF or less. Hope this helps and keep sparking!

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