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ZVS driver not working effecitently Answered

I have recently made a ZVS flyback driver. I got it working and the sparks are relatively impressive compared to other drivers I have made, but the arcs I'm getting seem a lot lower current and colder than pretty much every video I have seen of the ZVS driver. I used the Mazzilli ZVS schematic, and everything meets the specs in the schematic accept for the inductor which I made from a torroid i found in a PSU by winding about 15 turns of 18 gauge wire around it. the torroid has about a half inch outer diameter. I have a 5 5 primary on the transformer made from 18 awg wire. As it stands The driver is able to produce 20 to 25 kv with a thirty volt input, but the sparks are for the most part purple (not the flame like orange I have seem people get). As I didn't have any lead acid batteries around I just used six lantern batteries in series. I suspect the problem is either the power supply can't provide enough current, but I have measured and it seems to draw about 4 amps when arcing, and from what I understand it should draw about 10 amps and try to do that regardless of the power supply. I also think it could be the inductor is the problem, since it is what provides the constant current to the primary. If anyone knows what the problem could be and how to fix it, I would greatly appreciate your advice?


Make life easy for me. Post a link to the circuit.

Most likely its an inductor problem.

That's what I figured since it makes the constant current to the primary. Here's the schematic I used:

Mazzilli ZVS Flyback Driver.png

You REALLY need to see the state of the current in the transformer primary leads to make much headway, if you think you're going to get more out. The inductor is there to block AC currents from escaping from the transformer.

Measure the inductor.

I measured the current across the primary to be only at most 1.2A. I don't have an LCR meter so I can't measure the inductor's inductance. I have tried three different inductors each with very different number of turns and sizes of toroids and I have gotten very similar results from the driver. Is it still possible that the inductor is what is causing the problem?

One thing I noticed is that when I measured the voltage from the batteries when the driver was running with it measured about 30v, but when I drew an arc the voltage dropped to about 10v. I have known that when you put a load on power supplies the voltage dropped, but I didn't think it would be that much. Could that be what is causing the problem?

Yes. There's a good reason why lead acid batteries are recommended.

If you are messing around with electronics, you really are getting to the point, especially with this kind of circuit, when you need to beg, borrow, buy or steal an oscilloscope. It is worth its weight in gold.

I know what you mean, There have been quite a few instances lately where an oscilloscope would have helped me fix problems a lot faster. I have tried bidding for some on ebay, but to no avail.

I will get some lead acid batteries, and That should solve the problem correct?

Even one of the teeny-tiny 50 USD jobs is worth it. I would avoid PC based scopes though, working with HT might kill your computer.


And it lives! thanks for your help. the driver works better than ever now.
My next purchase as far as tools go will most definitely be an oscilloscope. As always, thanks for your great advice.