How To Build A Simple But Powerful Flyback Driver


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. 
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XTL11 months 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.
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!
a2262632 years ago
How do I find which pins are the inputs to the primary coil on the flyback?
This site ( 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
aadz931 year ago
Hey I have some stw88n65m5 mosfets which are rated at 650v at 84 A max will these work?
Lol yes, those are more then enough, as long as they are mounted on a heat sink & are N-channel fets as the schematic calls for, it will work lol. I had used many different kinds of fets before. The worst that will happen, is they'll pop into smoke... ( witch in that case, you'd better have a fuse, or a PC power supply. or you're asking for an electrical fire lmao )
Say I want to drive this at 100V, would two STY34NB50's work? and what other components would I need to change to accompany them?
Darian s2 years ago
Could you use two different MOSFET's as long they have the correct specs
Aj962 years ago
How many turns, did you put on your transformer?
how much does it cost to build?????????????????????????
jzhan2 years ago
How do the IRFP260N transistors fare?
Umniscient2 years ago
Will the IRF510 work instead?
Does it matter which way I wrap the wire on the inductor?
jhutton2 years ago
if i use a power adaptor, what kind of amps range should i be aiming for?
could i use a IRFP450.
p8ntball373 years ago
will this work well for the capacitor?
z0tx3 years ago
I'm trying to build one of these, and this tutorial is excellent, I have one question: Will a couple of batteries in series be suitable for the power supply?
noctres4 years ago
would FQA32N20C work for the MOSFET's?
kencbk4 years ago
Nice work :) btw, will a irf740 mosfet 400v @ 10a? I'll be using 45v MOT power supply to run it
Plasmana (author)  kencbk4 years ago
They should do, though I recommend you give them large heat sinks as they will most likely generate an considerable amount of heat.
kencbk Plasmana4 years ago
thanks, your article helps alot. :) btw, i found this interesting video in youtube homebrew transistor ( ) nice video good explanation, worth trying it out thanks again
will this work with AC power which of these capacitors would be better for the 68uf 250v+
Plasmana (author)  HazzWold19934 years ago
The MKP capacitor ( )

Any MKP or MMC type capacitpors will work, other types of capacitor may blow. :)
luudvig4 years ago
I got a bunch of "IRF640" MOSFET's lying around.. Would they work with this circuit?
Plasmana (author)  luudvig4 years ago
They will work for this driver, however, it will not work the best.