Introduction: How to Build a Simple But Powerful Flyback Driver

Picture of How to Build a Simple But Powerful Flyback Driver

Tired of little purple sparks? Want bigger hotter sparks? Then try: 

The ZVS Flyback Driver

It is probably the most powerful and efficient flyback transformer driver that was fairly recently invented by Vladmiro Mazilli. It uses resonant zero voltage switching (also know as ZVS) to drive the flyback transformer. This means the MOSFET's are designed to switch (on or off) when the voltage across them becomes zero.

Because the MOSFET's switches when there is no voltage across them, it will generate very little heat, the only source of heat is caused by the MOSFET's internal resistance. Unlike the simple 555 timer flyback drivers, The ZVS flyback drivers will allow you to run your flyback transformers for much longer periods of time before the MOSFET's overheat. If you get really good MOSFET's, it might be even possible to run your ZVS flyback driver infinitely! (Or until the circuit is interrupted)

Video of it working! 

Step 1: The Dangers of the ZVS Flyback Drivers

Picture of The Dangers of the ZVS Flyback Drivers

Not only the ZVS flyback driver is powerful, but it is very dangerous. You can easily pump several hundreds of watts into the flyback transformer and the output current would be around 50mA to 200mA (or even more), which is way above the lethal rate which is 10mA.

Do NOT attempt to do this as your first flyback transformer driver project, I recommend you to start with using simple 555 timer flyback drivers before thinking about building an ZVS driver.

And finally, you are solely responsible for any harm to others or damage or any other problems that a ZVS driver may cause. The ZVS driver should be used for educational and research purpose only.

That is the end of my health and safety rant. :-)

Step 2: Parts

Picture of Parts

ZVS drivers are fairly cheap to build, the only pricey part may be the MOSFET's. I got most of my parts from Farnell and some of it I had lying around.

• Flyback transformer
Newer flybacks are recommended as they are very robust. You can use an older flyback for higher current output, however, they are more likely to burn out due to excessive voltage.

• 2x 470Ω 2W resistors
The color code is yellow/purple/brown

• 2x 10KΩ 1/4W resistors
The color code is orange/brown/black

• 2x 12v 1/4W zener diodes

• 2x 400+ volts fast diodes
I used UF4007 diodes.

1x  inductor
The value is not critical but it should be 47uH to 200uH rated at 10A or more. You can find an inductor from a computer PSU or you can simply make your own, just wrap 20 turns of 16 gauge of enameled wire around a ferrite toroid.

• 1x 0.68uF 250v (or higher) capacitor
This capacitor must be bipolar and must be good quality, such as MKP ot MMC types. NEVER use an electrolytic capacitor, they will blow up. You can test various types of capacitors to see which one suits your ZVS driver well.

• 2x IRFP250 MOSFET's
They are a bit pricey, however, you can use other MOSFET's that has Vds 4x more than the power supply and has the Rds(on) lower than 150mΩ. Unfortunately those MOSFET's are a bit over my budget so I used the IRFP254 MOSFET's instead, not the best, but it is cheaper and it and it should give me good arc results. I also tried using the popular IRF540 MOSFET, however, it gave me very poor results.

• 2x small heatsink
They won't be necessary if you are going to run your ZVS driver lower than 12v.

• Large variable voltage power supply
Now this can cost quite a big chunk of change, you can a computer power supply unit for 12v power source. If you want a higher voltage power supply, then you might want to consider modifying a microwave oven transformer, but this is another project. As I don't have a large power supply so I used six  6v sealed lead acid batteries all in series to gain 36v to power my ZVS driver.

Then finaly the other bits and pieces you may need such as solder, thick wires, etc. 

Step 3: Schematics

Picture of Schematics

The 5 turns of wire as the primary is not critical, you can add or remove windings for different performance.The voltage input to the driver may affect the number of turns required as well.

The "47-200 µH" inductor can be customized to the desired output of the flyback transformer. In general, if you want a higher voltage, the inductor should have an higher value, if you want more current, the inductor should have an lower value. Also, an inductor is a 'must' for the ZVS driver, without it, your ZVS driver may work poorly or not work at all.

Changing the value of the capacitor can also affect the performance depending on the flyback transformer, again, make sure you use good quality capacitor.

Step 4: Construction

Picture of Construction

Not much to say here, just get your toolbox, read the schematics and build it! :-)

Make sure you use thick wire as it will be handling currents up to 10 amps.

When winding the flyback transformer, make sure both wire go the same way.

If you are going to attach both of your MOSFET's on one heatsink, Use mica insulators! Or other types of insulators to isolate the MOSFET's tabs from each other, otherwise your ZVS driver won't work.

Step 5: Power Her Up and Set Wires on Fire!

Picture of Power Her Up and Set Wires on Fire!

When you first power on your ZVS driver, start with 12v input to make sure everything thing is working. Then you can increase the input voltage up to 36v. You can power the ZVS driver above 36v, but then you risk blowing up your driver, check step 7 for instructions for modifying your ZVS driver to handle higher input voltages.

You may hear an very high pitched squeal from your ZVS driver, don't worry, that is normal.

What ever you use as your negative terminal, it will get hot, very hot! The arc will melt any thin wire you use into little metal balls and steal will just fly everywhere, which is cool (and dangerous)! If anyone has a good explnation why the negative terminal get so hot and the positive terminal remains fairly cool, I'd like to know.. :-)

Also, in the video, just after the arc burnt a hole into a lightbulb, they was a stream of plasma 'shooting' out of the bulb, like a flame thrower. This is because when the arc got inside the bulb, the gas inside heats up, causing it to expand and escaping through the hole thus creating a "plasma thrower".

Step 6: Modify Your ZVS Driver for Higher Performance!

Picture of Modify Your ZVS Driver for Higher Performance!

I have not tried this yet, but there is a revision of the ZVS driver by Andrinerii. He added two separate 3 turns of wire on top of the existing primary, each with a series 100Ω 10W resistor. This circuit supposedly add an 35% increase in performance.

Also, make sure your 3 turn windings are the same direction as the primary, otherwise you will blow the MOSFET's!

Step 7: Going Further

Picture of Going Further

The fun does not stop there, if you are hungry for more bigger, hotter, and beastly arcs, a few changes to your ZVS driver should be made to handle higher input voltages.

For input voltages over 36v:

Change the 470Ω resistor to 1kΩ resistor.
Change the 12v zenner diode to 15v zenner diode.
Increase the number of windings on your flyback transformer.
Increase the value of the inductor.

This should work well for voltages up to 60v before the MOSFET's should be changed as well...

I heard that some people had operated their ZVS driver at voltages over 100, just imagine how massive their arcs must be!

Also, this ZVS driver circuit does not have be used just for the flyback transformer, you can replace it for use a different transformer to charge up your large capacitor banks for coilguns, railguns, etc. It might be even possible to do induction heating with this ZVS driver circuit...


aladdin_2005 (author)2017-05-21

Thank you

SnipeX_Š (author)2017-05-10

Do i need to use zeners when mosfets like irfz44n have them build in?

SimpSg1 (author)2017-04-26

would 1n4007 diodes work for this ?

vina1991 (author)SimpSg12017-05-08

you need a ultra fast (UF) diode for fast discharge

CryogenicG (author)2017-02-23

Does the wattage of teh zener matter, as i cant find any 1/4 watt ones...

lour11 (author)CryogenicG2017-04-18

As long as the zener you use has .25W or greater, it should be fine.

tkalfaoglu (author)2017-02-16

Did you really mean that the inductor should be 47uH to 200uH?

I am achieving 0.2 mH with only FOUR turns of a 1mm enameled wire, not 20.

Jee Kate (author)tkalfaoglu2017-04-15

Maybe you should use another type of magnet ring? I uses the yellow one and it works. I teared it down from a old ATX

tkalfaoglu (author)tkalfaoglu2017-03-06

GUYS: This is serious: I am not getting 47-200 uH with 20 turns; I'm getting that value with only FOUR turns of the 1mm enameled wire. I'm measuring it with a Henry-meter..
What shall I do??
Was it suppose to be 47 mH-200 mH instead? Because that would need a lot more turns than just four..

tkalfaoglu (author)tkalfaoglu2017-03-06

here it is:

Jee Kate (author)2017-04-15

It's absolutely awesome!!

tkalfaoglu (author)2017-03-10

If there are other noobs like me: 0.68 uF = 680 nF

tkalfaoglu (author)2017-03-08

This is odd, but my capacitor keeps getting warm, but nothing else.. and I get no arc... what could be wrong?

MihaG3 (author)2017-02-24

I used it before in simple flyback driver and i dont know but sparks were getting shorter and shorter every day and that is why i want to make zvs for SGTC

MihaG3 (author)2017-02-24

I have a halogen transformer which gives out 12.5 v and 6 A and power of 70 W will it work the same as 12 v power suply

aclark17 made it! (author)2016-12-09

Kind of hard to see but nice long arcs even at ~12v and goes easily up to 35v+, but it starts getting kind of dicey in the safety department that high. I have mine powered by a variable AC transformer (Variac) through a full bridge rectifier for DC. Initially I tried using a modified PC PSU, but like someone else said it's circuit protection shorts it out almost immediately. With the variac I once made a mistake by turning the dial the wrong way (derp) and it was up to about 60v for a brief moment and still functioned properly haha, excellent build!

MihaG3 (author)aclark172017-02-24

how did you made power supply

tkalfaoglu (author)2017-02-16

The flyback transformer part is not well explained: What do we do with it?

I am assuming that we buy/find a TV transformer, and wrap 5x2 coils onto it, and use its output as our high voltage lead?

jjmcdsc made it! (author)2017-01-14

Not the prettiest of heaters but I did make it. Only issue is I keep blowing mosfets but I believe it's because they are really low Z4A and not irf250's but that's what I have on hand. Thanks for the instructable :)

jjmcdsc made it! (author)jjmcdsc2017-01-25

Decided to re-do the driver with some changes and like how it worked out :) A little cleaner looking. Mosfets stay cool but the capacitor heats up and will blow from energy storage I believe, so I'm going to add another capacitor in parallel and see if that helps. Liking this so far. :)

jjmcdsc (author)jjmcdsc2017-01-25

I used IRF640 mosfets for this project as well

Wolf6774 (author)2016-05-21

Hey guys, i made a zvs driver, and i cannot get it to work properly. I first made the zvs driver, and my computer power supply kept shutting down when i attached the inputs to the circuit. I know how to make the signal work to get the 12v output. But i changed a few things, and it made one transistor hot, out of the two i had. I tried to change it to work again, but now its back to the beginning. I'm not sure if it's my crappy circuitry construction skills, or just the PCU. PLEASE HELP.

Joe3502 (author)Wolf67742016-05-25

Do you have the optocoupler bypassed in the computer PSU?

Wolf6774 (author)Joe35022017-01-22

How would i bypass the optocoupler, i have heard of soldering together two of the pins, but i cannot find out which ones to solder.

draquuis (author)2016-05-10

hi, I'm having a lot of trouble finding the 10KΩ 1/4W resistors, does a half ohm resistor work too?

jjmcdsc (author)draquuis2017-01-08

I know this is late but maybe because the colour code is actually br-bl-bl-gold for 10 ohms. the colour code or-br-bl-gold is 31 ohms, going by calculator and is a non standard e24 series.. Hope this helps

wzdl (author)draquuis2016-06-22

0.5ohm will not.

0.5W.,10ohm wii

Joe3502 (author)draquuis2016-05-25

No. Amazon has them pretty cheap. recommend them to anyone who wants to build this. If anyone wants a parts list to see where I bought everything, just comment above and I'll get back asap.

jjmcdsc (author)2017-01-08

Hello, i'm having an issue with my mosfets. I have a bunch of
IRF650b mosfets that seem to all be staying open. I test them completely
and they wont discharge and close. I am testing them with 5 and 12v.
When I test my FQA9N90C Mosfets, They work just fine. Is ther something
different about the 650's that need to discharge or are they all no
good? Thanks for any help.

Free kill (author)2016-10-12

I power my own deliver at 156v and yes the ark are very big :)

ha duyT1 (author)2016-09-21

I've used this circuit to control FBT. I can run indefinitely but mosfet still not hot. but when I used to control the pulse transformer and the output connected to a 60w incandescent bulb, it becomes hot very fast though I have used a large radiator! I used source 12 VDC, 2 mosfet IRF3205, i not use diode zenner
please tell me the cause!
Thanks you!

EdmG (author)2016-08-22

Can i use irfp 260n on same schematics? I cant find ifrp250

Wolf6774 (author)2016-06-17

Is there a way that I could possibly connect two computer PSUs so I could get a 24v output at the same amperage of the original one or higher? Maybe connecting them in parallel, or one -12 to a +12 rail of the other? Someone please help me on this. Thanks in advance!

Mike99561. (author)Wolf67742016-08-08

I would not use computer ATX suppplies, as the GND is mostly common to earth wire, so serial connection will short the supply

rah187 (author)2016-06-01

Funny story, I made this one time before on a breadboard, and it worked the first time! However, the size of the sparks quickly died down and I relized something was wrong. Right now I am trying to replace the MOSFETs with IRFP260N's and I may have to buy parts so I can build a power supply (the first time I ran this I had to use batteries because they was all I had around, and the performace was far from ideal).

DavidX5 made it! (author)2016-05-30

I made it, it works, but is it running ok if at 13.8v it only draws a few hundred mA, and only produces a 1/4" thin purple arc on my flyback secondary? Nothing gets hot on the board... I just want to be sure it's all acting normally before I hit it with 30+ volts from a supply capable of serving 30+ Amps.

Joe3502 (author)2016-05-03

I've made it. It WORKED great for a while. The the next day, I fired it up, and nothing. It stopped working and still can't figure out what's wrong with it. I'm using a 12v 10A power supply. maybe not enough current? Idk.but I do recommend this to others looking to build this.

BenderSanchez (author)2015-08-14

For some reason I get both DC and Ac at the output also DC and AC in the input and I tried using a toroidal transformer since I didn't have any flyback transformers and it just heats up and the circuit only takes in 6 volts 5 amps even though my supply can give 20 volts 12.5 amps.

mroylance (author)BenderSanchez2015-08-17

I had the same issue;

I found putting a nice big capacitor in paralell with the power supply did the trick, i'm pretty sure the issue is a large voltage drop when you initially power the circuit, preventing the FET's from being switched properly, the capacitor provides a little stability at the start, as the capacitor resists the rapid change in voltage.

Hope this helps

Joe3502 (author)mroylance2016-04-22

Thank you!!! This helped so much!!!!

mroylance (author)mroylance2015-08-17

Alternatively use a more stable powersupply such as a computer PSU

My toroidal transformer just heats up and no voltage/current is registered at the output.

Joe3502 (author)2016-04-22

I have a concern. One of my MOSFETs are heating up and the other is not. Is this normal?

SaurabhP31 (author)2016-04-20

Hello.. I am trying to make wireless charger using flyback driver. Can you please tell me the input I should give to driver for efficient transmission

Joe3502 (author)2016-04-10

I have another question. What is the midget pinout from schematic to the real thing? I know there is drain, source, and gate, but which pin in which? Could someone do the same thing as I did but instead of the question marks place the locations of the drain, source, and gate? Thanks!!!

Proto G (author)Joe35022016-04-10

You should be able to tell which is which without them being labeled. You should take the author's advice and not attempt this if you are a beginner. You can get killed if you don't know what you are doing.

Joe3502 (author)Proto G2016-04-10

Thank you for answering so quickly!!! I'm not a beginner though. I'm not just that good at reading schematics that well. So the pins that go towards the left side of the schematic is he middle pin (gate)? And the other two are the ones on the side (drain and source)?

Joe3502 (author)Joe35022016-04-13

Or do I just use the labeling that Proto G include but just switch the drain and source?

MartinN55 (author)Joe35022016-04-19

Try google datasheet of your mosfet :-) (pin 1 is the left one)

Joe3502 (author)MartinN552016-04-19

So then I should follow the picture on this page:

About This Instructable




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