Last summer I encountered some videos of the ZVS driver online. I had derped around with single transistor flyback drivers, but it wasn’t anything too serious. The ZVS on the other hand was promised to be the most efficient driver around, and the videos of it only supported this. I had kind of forgotten about this driver until I was browsing Mouser one day looking for some Mosfets, and thought I recognized them from somewhere. After a few google searches I found that I had indeed seen them before, on the Mazzilli ZVS driver schematic. I quickly looked around to find the other necessary components and found that I could get enough components to make two of the drivers for under $30! After knowing that I couldn’t possibly keep myself from this wonder of electrical engineering any longer. I ordered the parts and got building. Before long I had my own ZVS driver.
I made sure to use thick wire for all the connections because up to 10A could be going through the circuit. I wound the 5+5 primary with 18awg enameled wire and it has worked fine. I also put a rubber pad between the wood and the bored as well as adding a power switch and some 12 awg wire for connection to the batteries on the power input terminals. I also replaced the inductor, but I have no idea of the value of either inductor that I used. Everything else has stayed pretty much the same and matches the specs recommended on the schematic.
The ZVS is a push pull oscillator. In its purist sense it would consist of nothing more than two mosfets a capacitor and an inductor. The driver relies on the fact that no two components are exactly alike and uses small differences in the mosfets’ internal resistances and other properties to start the oscillation. The capacitor prevents the current at the primary from rising to the point where the core saturates, and the inductor prevents AC from getting back the the batteries. Other components are used as you can see though. The fast diodes prevent the fets from turning on when they shouldn’t and going suicidal. The rest of the additional components act as gate protection to make sure excessive voltage does not reach the gate of the mosfets and kill them.
In operation the capacitor and primaries form an LC circuit, so you can easily change the frequency that the driver opperates at by changing the value of the capacitor and/or the number of turns on the primary.
To power the thing, I tried to use 6v lantern batteries at first, but these are not at all designed to handle a 10A current draw. I found that with 6 of them in series the voltage would drop from about 36v to about 8v! This fact made them absolutely useless for this driver.
what you really need is a few sealed lead acid batteries. Although big and relatively expensive they can pump out some serious amps without any trouble, and are absolutely perfect for the ZVS. I started out by ordering two 12v SLABs from ebay, though I plan to get one or two more when I have some more money.
Despite running at only 24 volts, this driver was putting out some very impressive results. I estimate the voltage is 20kv-25kv, which is decent, but the current had to have been at least 100ma! I was able to draw the arcs which started at a little over an inch to 5-6inches!
The ZVS is a truly marvelous device, and I can already think of a lot of projects I would like to include it in. The only problem I have had with it so far is that it has a tendency to destroy every capacitor I use with it after a while. I originally had an MKP cap on it, but it inexplicably failed on my second day of using the driver. I bought a mica cap with the necessary ratings as a back up, but it over heated and eventually failed as well. I found another random film cap in an ATX power supply a while ago with pretty good specs so I tried it. It worked surprisingly well for about a week before it too over heated and failed. As it stands I am still looking for a suitable capacitor, but I’ll update you when I find one.
If you attempt to build the ZVS driver, always keep it on an insulating surface, and use a chicken stick! a 2 foot long piece of white (black colored pipe can indicate carbon which can become conductive) PVC should work well. Never touch a live wire of the ZVS while it is on even if it has insulation! Also make sure you always disconnect the driver from the batteries if you are going to touch anything on the driver. Power switches are convenient, but you shouldn’t entrust your life with them as it is easy for them to get turned on by mistake. Also it is just a good idea in general to have multiple checks to make sure a high voltage device is off so you don’t loose your life.