How to Build a Simple But Powerful Flyback Driver

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About: ––––––––––––––––––––––– "Energy cannot be created nor destroy...

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

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

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

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

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!

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!

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

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...

11 People Made This Project!

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395 Discussions

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ahmedfebri13

7 weeks ago

hello ! anybody can help me why my project can't working !? i use power supply 12 DC - IRFP260n , just only heated at resistor 470ohm 2W .... please help!

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Juan262ahmedfebri13

Reply 23 days ago

Have you checked all conection. If all your conections are correct check the mosfets gate drain source and make sure they are properly placed. Make sure your zener diodes and uf diodes are correctly alligned. Also make sure your flyback windings are correct

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ahmedfebri13Juan262

Reply 5 days ago

i have got succes on it (it can running but with small arc) now it cannot running again i got fell heat on mosfet ( just one) i fell it warm (if for long time it become heat) and nothing charge on capacitor? what i must i do?

DSC_0236.JPGDSC_0235.JPGDSC_0230.JPG
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Juan262ahmedfebri13

Reply 23 days ago

You should also make sure your flyback is operational. And use a proper power supply

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Juan262ahmedfebri13

Reply 23 days ago

If it still doesnt work check the inductor or the capacitors for any damages or misoldering any of your solder joints

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AhmadM11

4 years ago on Introduction

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..

4 replies
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IC5AhmadM11

Reply 3 years ago on Introduction

At high voltages dielectric breakdown occurs where electrons find their way across an insulator due to ionization. PVC dielectric breakdown voltage is around 40 Mv/m. If your design is definitive, you could also seal the entire thing with wax or submerge it in mineral oil

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CristinaV22IC5

Reply 20 days ago

Bring your zener back to 10-15 volts. This will bring your gate voltage to a safer level and reduce transition time which is where most of transistor heating comes from.

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AhmadM11IC5

Reply 3 years ago on Introduction

OK.. Problem solved.. My chicken stick is a grey PVC pipe that made of pipe contains grey dye.. Even in a small measure, it's still more conductive compared to a white PVC pipe which contains no dye. It has been proven.

Anyway, the wax that seals the flyback still can't resist the spark leap from the HV pin. I want to choose the mineral oil, but the overall size would be too large. I just leave it as is until I find another solution..

And thank you very much for your advice..

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BenderSanchezAhmadM11

Reply 4 years ago on Introduction

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.

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CristinaV22RedstoneM

Reply 20 days ago

Zeners have a defined breakdown at a reversed polarity, anything from 2.5 to 100volts (rarely more), and are used to either regulate voltage, or in this case protect the gate from over voltage, these transistors have destructive breakdown of gate insulation at over 30 volts.. In some applications they help speed switching time by limiting the charge on the gate.

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MihaG3

2 years ago

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

1 reply
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CristinaV22MihaG3

Reply 20 days ago

Rectified? Halogen xformers don't always output DC, and fast acting diodes are usually needed because these generally operate above 25 kHz.

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Safe_Volts

1 year ago

I had built my ZVS driver. My only problem is with the 2 inductors. They get hot when I draw 6 amps at 24 volts from power supply. My ZVS driver deisgn is the one with no center-tap required. what could be the problem? Inductor core is 22mm X 14mm X 8mm, yellow-white colour

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CristinaV22Safe_Volts

Reply 20 days ago

The hot inductors are normal and are the limiting factor for power and run time. The answer is to use winding wire sized for the current 12 gauge wire will generally handle 15 to 20 amps in this application but overlapping windings and ventilation at major factors as well as the frequency of operation, (resonant circuits can have unusually high circulating currents even more than the input).
About the cores, I don't have a color code list, but there are several types. One to avoid is metal powder (not ferrite) which is used for noise suppression only, if you file some paint off and the inside is shinny metal don't use for this application.

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NajminN

4 months ago

How to drive a flyback with 320 vdc input?

1 reply
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CristinaV22NajminN

Reply 20 days ago

Must find transistors rated above 2,500 volts and voltage quenched primary ( usually a high voltage spark gap). Primary will have to be above 50 turns per half,, and be ready to die if you get to confident...

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firaz.2044

Question 2 months ago on Step 7

I have Made a successful zvs driver using irf3205 but I disassembled them. After again rearranging it is not working. I don't have irfp250.now I am thinking to make a royer flyback driver.I have ttc5200 transistor. Can I use them ?I have also 2n3055 but they may be damaged.help me building a royer one with ttc5200

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CristinaV22

2 months ago on Step 5

This hot negative effect is well known in welding. The negative lead melts the rod or wire onto the cooler surface. And welding over head or vertical, reversed polarity is used to avoid this dripping but usually requires more power and shorter arc lengths.
Electrons leave a surface at a smaller point than when they return due to mutual repulsion.
This effect was used in the early days for (inefficient) rectification of high voltages, by supplying AC to a sharp point over a larger surface, before better methods were developed.
And as different as Peltier devices are from this, they to, depend on electrons losing or gaining energy between contact surfaces, as well as thermal couples.