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

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. :-)

Comments

[Jimmeh30]

Is there a link to a schematic for this modification??

[Jimmeh30]

Virtip, has it right with regard to why the NEG terminal gets hot, the easiest way to wrap your head around (IMO) is to read up on tig welding.

The answer's regarding accelerated Ion flow are the more correct answers tho, given the HV field being generated.

Quick question tho, I built one of these with IRF450's, fired it up and got nothing. I now know that the input inductor I wound is FAR too large but, are you supposed to remove the air gap from the core of the flyback? or does it need the air gap to "fire"

cheers.

[grunff]

I built one of these, and it worked great for a few minutes at 24v, with nice 6-7cm arcs. Then both the IRFP250s failed catastrophically. Initially I thought perhaps the capacitor had gone open-circuit, causing the failure. But the capacitor is fine. Given that I was only running at 24v and ~8A, I'm puzzled as to why this happened. Any thoughts?

[Darian s]

Could you use two different MOSFET's as long they have the correct specs

[aeternusjunk]

I built and modified this circuit to get the most I could out of it. I'm using IRFP260s, I removed the zeners (any particular reason for those?), and I found that a 0.32uF cap works best for me (I tried many). I also found that placing a diode immediately before the (non-flyback) inductor increases the distance the initial spark can jump. The sparks aren't as long as when I hook the flyback to a simple square wave driver, but the spark is definitely hotter. When I simulate this circuit, it seems that once the circuit is operating, the current draw is very small, so I'm just curious how important it is to have a high current source. I'm using a 24V 0.8A ATX mod with decent results. It's almost non-functional at 12V 10A. How important are the high speed diodes? I'm using standard 1N4007s. Any suggestions for getting this thing working better?

[aeternusjunk]

Ok, I've got this thing working really well now. I determined that high speed diodes don't matter at all. There is no noticeable difference between switching diodes and standard 1N4007s at these speeds. I continue to have problems with huge current draw at startup, and I determined this is due to a lack of initial perturbations in the LC loop. The LC loop needs to have a pre-existing oscillation for the MOSFETS to drive a resonance. Shorting one of the MOSFET gates to ground briefly fixes the problem, but I need to determine a simple way of doing this automatically.

I will be making an Instructable of my modified design once I have everything nice and automatic, referencing this one of course.

http://youtu.be/tV1X7jv3oyU

[-max-]

what if you used a capacitor across the power supply that will hold whatever voltage

[aeternusjunk]

I just built a high capacitance mains rectifier circuit to go with my variac. It can handle about 8 amps continuously. I still don't have the right zeners, but as long as I don't go above 30V (maximum Vgs) it should be fine. After running it for about a minute, the copper plates I soldered onto the HV wires got so hot they desoldered. I'll be building a robust version of this soon, and I'll post my results. I'm still using the regular diodes, and still not sure if fast ones really make that much of a difference.

[Aj96]

How many turns, did you put on your transformer?

[guruji1]

I've built this with a 0.68uf cap. I would like to how much voltage and frequency is getting out? I'm using it on a 12v battery.
Any help please?
Thanks

[Inducktion]

Ehh. I built this, and for a power supply i tried using a bulky alarm system transformer. I rectified and filtered the power from the transformer, but its not working. The transformer is rated at 16 volts AC, at 26 VA, which i assume means 26 amps. When i plug it into the ZVS driver, the mosfets start to heat up, and the transformer heats up too, but nothing happens. I read the voltage going to the ZVS, and its only about 6 DC volts. I read the amps being drawn as well, and it starts at around 5.6, and slowly goes down, (not fast, slowwww).

When i dont have it plugged into the ZVS, the transformer puts out 27 volts DC. I don't get what the dealio is. I'm using a bridge rectifier and a 1500 uf 250 volt capacitor as the filter. And i know the driver works, because when i used several C and D cell batteries in series, the flyback starts working and makes tiny arcs. But when i use the transformer, the above happens, and the flyback doesnt even make any noise, at all.

Any advice, or problems with this? I even opened the transformer up, and all it is is just a vanilla transformer. Iron core. It heated up pretty quickly when i did plug it in.

[AintBigAintClever]

26VA = 26 volt-amps (the AC equivalent of watts). A 16 volt 26VA transformer is rated at approx. 1.6 amps.

I'd either use a bigger transformer or a lead-acid battery (away from the circuit, you don't want your arc igniting battery gases). If using a battery such as that, put a fuse at the battery end of the leads as they can put out HUNDREDS of amps.

[atsirogiannis]

26VA transformer means roughly 26Watts transformer... Which means that the amperage you can get from that is roughly 26w/16volt=2.16A... this kind of project needs almost 10A to be driven,so your transfrmer is definetly inadequate

[MrLWJ]

Unless my math is wrong, your not getting 26 amps, your getting 1.625 amps.
When dealing with electricity, guns, or high explosives, assuming can be dangerous. VA or Volt Amperage is the result of multilplying the amperage by the Voltage. Conversly to find amperage you simply divide the VA by the voltage to get amperage. If i am wrong I am sure it will be pointed out.

[Inducktion]

ahhhhhh. Okay. Thank you for that explanation sir. :D

[Inducktion]

Hm. Weird. I just recieved two lead acid batteries, 12 volts each, and i tried running it. Several of the traces on the board popped, and the wires get rather toasty, as well as the fets. The flyback still runs, but the sparks are rather minimal, very small. I've tried different inductors, that changes the performance alot sometimes. But, the question remains, why are my fets heating up so much, and why isnt my flyback running as well as it should be?

Do i need thicker lead wires?

[jhutton]

you didnt hook up the batteries backwards did you? :P
also, try a 10 and 5 turn on the flyback instead of 5 and 5

[aclark17]

OK So I used 560 ohm resistors because thats all I have.. Not sure it would make this not work. But I spent forever putting it all together, and I hit the switch and nothing!!

However, my power supply makes a faint high frequency sound, and when I move the wires wrapped around the flyback core it changes the frequency. Also these wires get warm, almost hot, (not too hot), I suspect it may be working just fine, but my flyback is damaged from earlier experiments. Does this sound about right?

Im obviously getting the field effect going, but the flyback is just not responding. Perhaps I blew an internal diode? I have only one other flyback at the moment, but I thought I would ask anyway, in case someone has the same opinion :)

[aclark17]

OK nevermind, I tested the flyback (duh) and it seems like its busted, Infinite resistance between the input pins when it should be reading about 0.8 ohms.

Tested my other flyback and got 0.8 ohms. I can confirm at least that the flyback driver circuit is working, however it doesnt seem much better than others I have built, but that could be because of the inductor (I switched to troubleshoot) or because of the windings on the flyback (theyre not wound 5+5, its an old setup) so when I correct these issues Ill try again, but this flyback is odd, it has a second smaller flyback (maybe a step down?) looking thing attached and it functions as the 0v pin, and theres about 8 pins on it. So Im also going to get another or several other flybacks and see whats up with that as well!

[somebody12345]

how much does it cost to build?????????????????????????

[aclark17]

Well if youre getting your flybacks from TV sets, probably nothing. I found almost all the components for this from the same TV, flyback, capacitors of all varieties, many higher wattage resistors, they even have some transistors and mosfets, but youre better off buying those, I found them at the Tayda electronics website for $1.16 a piece.

All wires, inductors, and that stuff can also be found in the TV, as well as heatsinks for your FETs

[kougsmotors454]

i replaced each 470 ohm resitstor with two 270 ohm ones and it runs fine at 48 v

i found that most flybacks from CRT displays only last 5 - 10 min before failing
so i bought a DIODELESS flyback from amazing1.com , i used "PVM400" , i removed the stock primary and replaced it with the one described in the zvs plan and it worked perfectly , created 6-7 inch flaming arcs and nothing was overheating or complaining, and since it was diodeless it made lots of corona , a great alternative to traditional tesla coil

thanks plasmana for posting these plans :)

[moris_zen]

At last I managed to get it going ... two issues
1. U cant connect a low rising PS (I connected it to a lab PS but the rise of voltage is too slow to get it started so had to switch in series)
2. I get sparks on the flyback internal legs many times until I manage to get the real HC on the output .. need to isolate them or something ...

I alos placed a very good heat sink on the two FETs with a fan but .. lol ... they don't heat up at all , even with fan off.
Any suggestions ?
Thanks

[kougsmotors454]

nice circuit it worked great!
i just thought i might add that you can buy flybacks from www.amazing1.com
" FLYMIS" 3 miscellaneous FBT's $14.99
But more importantly they sell high quality, high power flybacks ( much more durable than the t.v ones) WITHOUT the hv output diode , so you can do more interesting stuff with them like power plasma displays

i just ordered "FLYPVM400" and will connect it to this circuit
other sizes and voltages are available

[Umniscient]

Will the IRF510 work instead?

[Alex1M6]

No. The D-S voltage and max current rating is too low on them. Use 200v and 15amp minimum MOSFET's.

[jzhan]

How do the IRFP260N transistors fare?

[Alex1M6]

They work fine.

[adamdwaldrop]

What is the model number of this flyback you are using? thanks!

[solysol5]

Hey I followed this tutorial but for some reason, mine cuts off after about 1 minute of operation. Any ideas? P.S. I'm running it from an old PSP-1000 Charger giving 5Volts at 2 Amps. Thanks

[edalgetty]

actually i use a 18v 5 amp laptop charger, use chargers for tvs and laptops and things they usually have some good wattage

[shuhia]

XD man you need at least 12 volt and 10amperage to run the Zvs. Tips, modify a microwave transformer or use your car battery charger !

[R.A.T.M]

what is the poupus of feed back

[skrubol]

Are you rectifying the output? As this is a transformer, it's output should be pure AC, therefore no positive or negative.
Normally on a DC arc the positive will get much hotter than the negative (at least 4x more heat I believe.) Plasma cutters always have the work piece at + polarity, and tig as well. Arc (Stic, SMAW) can run either way depending on what you're doing (whether you want to melt the base more, or add more filler,) and I believe Mig/wirefeed is usually workpiece - (electrode positive.)

[shuhia]

Today, I managed to get my zvs working, with a washing machine capacitor: rated at

6uf , 360vac

I dont know what role the capacitor is playing but it works :)

I get super arcs with two irfp260 and if you guys can help me with rectifying I can run it with 41 amps...

[shuhia]

I forgot to mention that im going to use a Toroid transformer, rated at 12vac 500va.

Any tips how to rectife it to dc since its a sine wave?

[shuhia]

Is the capacitor optional? Becuase I they are expensive in Sweden!

[shuhia]

Guys, I managed to get same arcs with a 555 timer circuit with pots. The only thing you need is to get 10 turns on the ferrite core with thick copper wire and a powerful car battery!

[Alex1M6]

What MOSFET did you use? All of my 555 drivers don't last long before either the MOSFET or 555 chip dies and I never got arcs like I do with my ZVS driver.

This is the type of arcs I get from my 555 drivers; BTW it is audio modulated.

[shuhia]

I use à Irfp260 mosfet, feeding it With 6 amps and 12v. The 555 timers circuit r1 is rated 10k and r2 1k. The arcs gives the worst sound you ever can imagine.