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How To Build A Simple But Powerful Flyback Driver

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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. :-)
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_Totoro_ made it!20 days 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/

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danmellow26 days ago

osum stuff mate... nailed it

i found my Fathers old TV repair stuff in the shop the other day, and i've found several caps that are in there that are in there that are around 40+/- Mfd

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dudes2 months ago
get the irfp250's from taydaelectronics.com. they are only $1:50 each. and very low shipping
dudes2 months ago
any idea on the voltage that this puts out? after the flyback.
TK1756722 months 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?

Can somebody explain me what comes out of that 3 terminals? (where the coils are attached). How much current or voltage? what kind of wave? why two different coils are needed?

is there a way to make it not lethal

Some common safety rules/procedures I have read are: Keep one hand in your pocket whenever the device is powered on. Always wear safety glasses. Place the device as far from the edge of your bench as you can and still handle it (In case it slips off the edge when powered up.) Keep an extinguisher rated for electrical fires nearby. Do NOT place the circuit anywhere near metal flashing or framing, etc. Put it on a dry insulating surface. Put yourself on similar material (Eg. rubber mat, plywood sheet.)

When possible use opto-isolators to connect low-voltage signal lines to the rest of circuitry, esp. when you are touching the low voltage controls. Separate the high and low voltage circuit components with a grounded metal cage or barrier of some sort. Obviously, the cage has to be large enough so that it's walls are not going to short out to the HV inside it. For HV outputs use wire rated for twice the voltage you are delivering with it. (All capacitors should be rated similarly; they can explode dramatically.) Take into consideration the current rating for the gauge wire you are using; you don't want the wire to melt or catch fire. Don't use cheap auto ignition wire for this purpose. Use genuine HV wire that has thick insulation. Silicone insulation should be more flexible than PVC. If you must handle the HV wires, use with rods of wood, rubber, plastic etc. Don't trust ordinary screwdrivers and pliers, no matter how much rubber coating is used on the handles. Use common sense. With these requirements in mind check everything twice before powering up.

I make no promises that this list is complete. Use common sense.

turn it off ?

no
Wow I just checked this comment and it was a long time ago. Even if it is lethal I am still going to build it as long as I have the time, money, IRFP250 MOSFET's and the inductor.
Dillon123 4 months ago

I made something similar to this schematic

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vknezevic8 months ago

I have wondered how to plug in rectified 220V without burning out gates of mosfet. Then I found solution, wich is described on http://www.joretronik.de/Oszillatoren/Oszillatoren...

somewhere on middle of page. People complaining that can't use more than 70v, and with solution on upper page cann be used any voltage

Dillon123 8 months ago

use these Infineon 17n80c3

hohenheime8 months ago
How can I tweak the circuit to avoid putting too much amps on the MOSFETs, I couldn't find better than irfp450 (14A)
I don't mean to be jumping your case, but I must advise all people who try this schematic. Any of you recall the color code provided for a 10k ohm resistor? It is listed as orange/brown/black. This is not a 10k ohm color code, as I checked it on a calculator, and looked at the color/digit significance. This color code would actually be for a 31 ohm resistor. DO NOT USE this resistor if you are seeking a 10k ohm.

The actual color code for 10k ohms is of the same colors, but it is actually supposed to be in the order of BROWN/BLACK/ORANGE!

Thankfully, I recognized this prior to taking out the resistors needed from a TV motherboard. Do not worry about the 470 ohm color code provided, as the publisher has it listed correctly.

You're welcome.

MadDoctor Whitson
I recall how you were wanting to know why the negative terminal gets hotter than the positive when arcing. I don't know if anyone has answered this for you yet, but I will provide my input according to my comprehension of current direction.

First, you must understand that all the electrons come from the negative terminal of the circuit, and the high voltage positive terminal acts much like an electron vacuum. This is because all positive wires lack electrons, and when they come in contact with a negative, or ground wire, the electrons are sucked out from its resource.

Negative/Ground wires can't shock you, as the electrons can't flow into any conductor unless it lacks electrons - like a live wire.

Due to the negative/ground terminal possessing so many electrons, and the live terminal having virtually none, the terminal with the most electrons will get the hottest, as there is more electron friction in it. The live terminal doesn't get very hot, because any electrons to make their way into it are quickly "sucked" away, thus the live terminal still lacks electrons, and this lack in electrons results in very little friction.

Seemingly, everybody thinks the current flows from the live wire, when it is actually in reverse. It somewhat bothers me why schematics aren't designed in reverse as well. Due to this, I once drew a Tesla coil schematic in reverse.
Cormaxzyz10 months ago
What is the amp hour rating on the batteries you use to power this? Also do the batteries have to match (that is, same manufacturer and same ratings)? I'm asking because I've already burnt out a 5 amp hour battery with a few high-current experiments and I don't want to burn out any more!
Techno12131 year ago
Hello! I recently took apart a microwave and i didnt get a transformer, i got this. It came with no capacitor. How do i power it?
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This Is a flyback MOT. you can use the zvs on this kind
There is a transformer on there, it's the thing with the curved black piece going over the coil. You have to take it out.

This driver will not work for your transformer, it's not a flyback and isn't designed for high frequencies.

There are plenty of MOT tutorials out there.
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Yes, it can be, i have a .56µF and a .22µF in parallel combining, .78 µF.
And it works fine.
jasshopper1 year ago
could i use irf460 instead of irf250?
astrikos1 year ago
this is a graph from the same circuit but now the 1microfarad MKP capacitor is replaced by a ceramic 10nanofarad trying to achieve higher frequencies

as you can see the half cycle is 1microsecond which means 500khz frequency

the problem now is that I do not get high voltage on the flyback

as far as I know the ferrite core goes up to 2MHz, may the problem be the capacitor which can not handle big currents so I will try a more powerfull capacitor

the diode may be another problem because it's not ultrafast

the FET is ok according to the datasheet for this frequency
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XTL astrikos1 year ago
Its a resonant tank you are making with the coil inductance and capacitor. You are searching for the resonant frequency so just driving it faster doesn't mean it wil be more efficient. You need to balance the two out and drive it a frequency where the coil becomes resonant. Efficiency means the power will get through.
astrikos XTL1 year ago
I wanted to get high frequency and high voltage, not necessarily high power. I found out that this magnetic core works up to 160khz which is the frequency of the modern flybacks for big screens.
Mattef1 year ago
I think the reason why the negative terminal gets so hot, is that positive charged ions (Nitrogene+ and Oxygen+) are accelerated to it. The positive terminal gets bombed with electrons, but because they are less heavier, they don't generate much heat. Nitrogene and Oxygen are much heavier, so the "friction" (cross section) between the metal is even greater.
XTL1 year ago
The same driver can be used to heat any metal you put in the red wire loop (replacing the ferrite core flyback transformer). The cap value and number of turns (less) will need tuning to get the metal to heat up . The metal acts as a poor transformer core and resists the change in energy flow thereby disspating the wasted energy as heat. Generally a bad idea unless you want to heat metal up in an induction furnace.
XTL1 year ago
IRFP250 = 250V, 23Amps, RDS=140mOhm, Gatecharge(GC)=140nC
IRFP254 = 200V, 30Amps, RDS=85mOhm, GC=140nC
IRF540=100V, 33 Amps, RDS=44mOhm, GC=71nC
The 540 has a much lower voltage and might have had a problem switching, but its also likely the the Gatecharge (which is much lower) means you need a different tuned network. Try diff cap values.
arai101 year ago
Hey! thanks for this tutorial.i have almost completed the flyback circuit.But i don't have a suitable 15V,10A PSU.Can i get 15V,10A from the mains only by using a transformer ,bridge rectifier and smoothing capacitor,please suggest me the circuit.Your help would be highly appreciated.
Use a computer power supply. They have over current protection, short-circuit protection & various other things. they can be easy to come by. don't bother with transformers for your power supply... cause you need at least 10 amps for this circuit. I have yet to come across a wall transformer that's rated at 12V @ 10amps. PC power supplies easily have at least 20 amps... not to mention various voltages... ( +3.3, +5, +12, -12V )
qwertyboy4 years ago
You can get the MOSFET's from Digikey for $2 each. Doesn't sound like that much money.

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=IRFP250NPBF-ND
You could also consider going to texas instruments for samples. Don't order a crazy load of them tho. I've ordered many samples from TI & they're awesome. Priority shipping. Best of all, it's free!
Plasmana (author)  qwertyboy4 years ago
If you are going to make them go pop a lot, then it can get pricey.. :)
LOL, yeah, just be careful not to let the magic smoke out
Plasmana (author)  qwertyboy4 years ago
Yes, it is hard not to.. :)
a2262632 years ago
How do I find which pins are the inputs to the primary coil on the flyback?
This site (http://lifters.online.fr/lifters/labhvps/tht.htm) says "With a simple ohmeter this is very simple, you will find easily the primary inputs because the coil resistance is about 1 ohm"

I bought a new flyback a couple of weeks ago. My flyback has 10 pins. I got these results:

Pins ..... Resistance
1 + 5 .... 2 ohms
1 + 9 .... 1.8 ohms
5 + 9 .... 0.9 ohms

2 + 8 .... 0.9 ohms

3 + 4 .... 0.8 ohms
3 + 6 .... 0.8 ohms
4 + 6 .... 0.6 ohms
All the other combinations (i.e; pins 1 + 3) produced no resistance, so that means that pins 1 + 3 are not connected. Conversely, this means that pins 1+5+9 are connected; pins 2+8 are connected; pins 3+4+6 are connected; and pin 7 and pin 10 are not connected to any other pins.

The first problem is that many of these gave me a resistance close to 1 ohm, so I still don't know which pins to use for the primary coil.
The second problem is that a flyback should have two sets of connected pins; pins that connect to the primary coil, and pins the connect to the secondary coil. However, I seem to have 3 sets of connected pins (or five sets, depending on how you count). Does this mean something is disconnected inside my flyback?

I didn't know what to do, so I just went ahead and connected it to the CFL circuit. I tried pins 5+9, 2+8, and 3+4 as the pins to the primary coil, along with every combination of the 4 pins on the CFL circuit, but did not get a single arc for any of them. Does this mean that my brand-new flyback is bad?
I had the same issue... IMO. don't bother with the flyback primaries. Just wind your own primary coils onto the ferrite core. once you have your ZVS circuit build & connected to your newly wound primaries, very carefully sweep your HV lead by all the other pins... you'll know when you found the pin for the secondary. You'll see a nice stream of HV. I like to solder a wire onto the secondary pin & do what ever then... Just be sure you discharge the coils!! being zapped by HV isn't fun lmao
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