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! 

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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!
Sparkly arc.jpeg
Plasma thrower.jpeg
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...

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_Totoro_ made it!11 months ago

Great driver and 'ible! barely gets warm at 12v coming out of a PC PSU and really nice arcs, modifying a Microwave Transformer soon for 24v for longer arcs. Fiddling with the capacitor value helps a lot to get the best out of your flyback. I ended up with an arrangement of 6 caps (1µf 275v), 3 pairs in parallel then those 3 pairs in series to achieve 0.66µf capacitance that has a rating of 825v which meant less capacitor heat and easier to modify the frequency with different arrangements, this the is the calculator i used for the capacitor arrangements http://kaizerpowerelectronics.dk/calculators/mmc-calculator/


How does your PC PSU not have current protection?

bypass the optocoupler, simply solder a diode in the optotransistor side (the input side).

Optotransistor? Also, my driver outputs 20 volts AC between the centre wire and surrounding wire at the end of the circuit but when I connect the flyback transformer primary coils, it registers as 0 voltage on the output and 6 volts AC on the input. This is when i bought a power supply that provides 12 volts, 12.5 amps.

It's relatively easy. Computer PSU internal circuit usually divided into two section, input and output. The optocoupler is the bridge between them. Just solder the two optocoupler's pins inside the input section together and you'll get full power written on the PSU case (give or take 10%).


Thanks :D


What is the voltage of this thing roughly?

Vp=Pi*Vin or 3.14*12=37.68Vp


mkjunior2 years ago

built this circuit and when i first plugged in a 9v battery, i could hear the high pitch from the flyback.. consequently though I didnt see any arcs and the high pitch tone changed when i tried touching the ground output from the flyback to the positive output. Randomly though the circuit suddenly worked and i saw some nice arcs, but a bit later the circuit was doing the same thing as before. does someone know whats happening?
you don't have enough current from a 9v to turn the driver on, you need at least 10 Ampere to satisfy the driver. hope this helps.

PSU power supplies should do the trick but modfiying them to shut of current protection is a pain.

Dude, that's easy, just look at the optocoupler, solder a diode in parallel with the output of the optocoupler and voilá, no more current limits.

Try a rechargeable drill battery, if tou don't want to buy lead acids
TK1756721 year ago

Thinking of building this and i wanted to use a computer PSU but i wanted to ask: if i just connect it won't it try to draw the map amps the PSU can give and and possible damage the PSU or will it be fine? would i have to limit it in some way?

I tried using a PSU, it provides approximately the current required but I think there is something wrong with my circuit.

Nope current limiting is the problem, the PSU shuts down when too much current is drawn from it.

I was fortunate to get an X-box power supply that was fried. blown trace on the input and some blown caps and some soda residue... fixed it up. 17A at 12v (can be pushed to over 25A before overcurrent blows but it starts to warm up. upgraded to copper heat sinks and better fan.) makes a nice ham radio power supply. (20 or so amp at less than %50 duty cycle.)

for flyback driving i get the best arc at 1+1 turn :P need to mess with induction heating.

mcrenno218 months ago
Do the math to find your output voltage,
Output amps= .02-.7 amps
1:135 flyback ratio base on internal winding
turns 5+5 turns
input voltage ??? Depends on you,
my zvs
input 28v
output 63000v
I2 26mA
turns 6+6
20141110_190028.mp4(240x320) 10 KB

What did you use to power it?

For some reason, my PSU triggers the short circuit protection when I connect it to the circuit, how do i disable that?

AhmadM111 month ago

Finally I made it!

But something just feels not right.. The stream from flyback transformer always try to breach anything to find ground.. And mostly it did it in one way or another, every time I move the cathode away.. Once the stream lost, it's like going wild.. Sometimes I can see sparks outside the fuse case of the DC PSU..

I drive it from a 10A 36VDC PSU.. I doubled the 2W resistors value and increase the zener to 24V also two 270nf/400V caps in parallel as the final caps..

I've been questioning what could be wrong with the circuit.. Or is it just because the voltage too high for my entire circuit/case design? Because it still can reach my hand through my 50cm PVC chicken-stick.. I can feel it and I can clearly see a slight stream strike back to the PVC.. Kinda strange for me because a PVC should be a good insulator..

move the power supply away from the driver and the driver away from the transformer (increase the length of the wires) that would work also try using insulating tape on your chicken stick.

shigeno212 months ago

is it possible for a hog stunner? how could i increase the current ?

Why would you want to stun a hog.....

it is my project for a backyard slaughter house i think a minimum amp to stun a hog is 1.25 amp can i use a microwave transformer rather than a flyback transformer of tv? can you help me thanks in advance.

1.25 amps, how many volts, what is the power in watts?

hmm around 220-250V so i think it will have a 275-320W from a minimum of 1.25A

Mains current unless you are hunting then lithium batteries connected to an inverter, this is hundreds of thousands of volts.

dillonxti10 months ago
I need a version where you don't need zener diodes and you can use the wall voltage to power it
I meant I may need a version where you don't need zener diodes and you can power it straight from the wall voltage

Dude,i''ll give you a hint, if you just want to power up your flyback you can modify a power supply, just fking remove the original transformer, find the primary winding using a multimeter, and weld the old pcb to your transformer. Weld a simple diode (IN4007 or other) in parallel with the output of the optocoupler to assure that the driver will work in maximum charge, and voilá.

It took me 20 minutes to weld the whole thing and make the new turns on the primary of the flyback. **i used 100 turns.

I actually made it work without the diodes and transformer my autospell kept putting need instead of made so yeah it did that to me twice

Could you send us a schematic?

the circuit on the left is my schematic the one on the right is the original -video of it driving a Tesla coil: https://youtu.be/s_HP_is5m_E

Thanks, got the instructable circuit to work though, the flyback transformer is

Nice instruct able but I am facing some issues, my mosfets and inductor just heat up and it does nothing else, is there something wrong with the circuit or the mosfets or the inductor or the flyback transformer? Any valid help would be of great use :D

My flyback transformer is spoilt, its still outputing 18-19 volts AC

Yeah that was the only problem.

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