Mazilli ZVS flyback driver
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Introduction
The Mazilli ZVS flyback driver is wellknown throughout the high voltage community for its simplicity and ability to deliver 20-50kV at high currents for a flyback transformer.
I build this circuit almost a year ago on a veroboard, but it kept blowing the thin traces due to high currents flowing. I eventually put the project in a box and forgot all about it.
Inspired by the point to point soldered designs Myke from the 4hv.org forums often uses, I tried to make something in that manner, not as pretty as his work though.
Considerations
The MOSFETs used need a voltage rating about 4 times higher than the supply voltage and a on-resistance below 150mΩ
5 + 5 primary windings are suitable for voltages between 10 to 40 VDC, at higher voltages additional windings will be needed. Experiment with the number of windings to improve performance. Too few windings will result in excessive heating and too many will result in reduced power output.
A MMC is made from 6 capacitors to avoid excessive heating in a single capacitor.
This driver will push as much power as it can, so be sure to use flybacks that can handle the abuse if you want it to live.
Specifications
| Voltage supply | 35 VDC from a rewound microwave oven transformer. |
| MMC | 0.66 uF from series string of 3x 2 275VAC MKP X2 capacitors in parallel . |
| Power consumption | 400 W. |
| Longest arc | 100 – 110 mm long white arcs |
Schematic
Construction
15th may 2009
I have now rebuild the driver using 2.5mm² / 14AWG wire for a good current ability, larger heat sinks and a MMC to avoid as much heating as possible.
Sparks
16th may 2009
I found 4 different flybacks from my collection, among these are a 1980’s Bang & Ollufsen television flyback. A small flyback from a photocopier. A flyback from a 1990′s portable television, it is without screen and focus resistor networks. A flyback with rectifier tube from a black & white 1950′s television.
The pictures with long arcs about the size of 100 – 110 mm was made with the 1980′s Bang & Ollufsen flyback transformer.
Conclusion
It was well worth it to rebuild this driver. It can now handle long runtimes with little heating despite pushing out around 400 W of power!
Demonstration
Posted October 23, 2009 by Mads Barnkob | Log in
hi,
I am a physics student with some experience with electronics. I have ordered parts for the ZVS
driver you are using.
I have a question about the toroidal inductor. I have some ferrite toroids laying around I pulled from computer
monitors while getting their flybacks. I don’t know how to look up their characteristics to calculate the inductance. In the past I tried using a bridge and Oscope, but that has not worked well for me.
Is there a rule of thumb that will get me moderate enough accuracy to make a good circuit ?
The flyback I have choosen puts out a strong arc with my 555 driver. More so than another larger looking FB.
My MMC kinda sucks since I didn’t figure what to buy until after I spent some money, so I need to break (use) what I have first; 50, 2KV ceramic 0.01uF caps, 10 series = 1nF with a max of 5nF.
As well, I don’t have 2W resistors but do have 1W resistor….hoping that will work enough to get started
especially since I can only draw 5 A from my supply.
I’d love to make my own power supply. I have tried to make a small one for practice but the loading is confusing me. I started with 35 Vpp and by the time it as rectified and had a large cap in parallel, it was down to 3 VDC. I would prefer to make it regulated. I had an electronics lab which built a Wilson mirror and a BJT voltage. Do you have a link to a good schematic or can I use yours ?
thanks for reading all this…
cheers,
wbg
Hey wbg
I would advice you to get one of those real cheap LCR meters off of Ebay, they have a good accuracy compared to their very low cost. A LCR meter in invaluable in electronics anyway, you need it!
Salvage some MKP X2 capacitors from a pc power supply or anything else that uses them for input filtering, if you have no money to spend on these very common and cheap capacitors, your MMC is far from enough with only 1nF.
Get a variac for a “cheap” variable supply, a variac will take any abuse up to 300% of its current rating for short runs of a few minutes, with a nice lab power supply you will risc damaging it powering up circuits like these that can have some heavily back EMF through the circuit.
Kind regards
Mads