ZVS Flyback Driver

Well, on route to one of my many other projects I needed a form of ignitor, couldn't get my hands on any neon sign transformers (the three local sign places either didn't have any, or wanted $100 a piece), and MOT's were too low voltage for my needs. My attempts at winding a step up transformer also resulted in a step down transformer due to lack of wire. Here's how I managed to create a ZVS driver and not electrocute myself in the process!


As a result, I decided I would try a Mazzilli ZVS flyback driver. From my Electronic Goldmine order, I received the two MOSFET's I needed being IRF640's, as well as the fast diodes. These IRF640's were a bit of a just buy them and hope they work, as I didn't intend to spend the extra dollar on each to get the IRF250's, stupid decision really. The ones I received are rated at 200V, and 18A, with a slightly high RDS(on) of 0.18Ω.

The following pictures detail the build and progress:

 Driver almost finished.

 Testing setup, running 24V as 12V didn't seem to work overly well.

 The arcs are decent, with the current setup, I was getting ignition at 1.5cm on power up, it appears to drop to a lower operating voltage once it's running (won't start the arc until the electrodes are much closer). I'm not sure what this is a result of. Pulling about 100W from the 24V supply.

 The arcs do have a nice look to them when they're about to break.

Finished driver, added an extra cap as I assumed this could help.

Specs:
Based on the Mazzilli ZVS driver

My driver consisted of:

• 2 x IRF640's (RDS(on) of 0.18Ω
• 2 x 330nF capacitors in parallel with an extra 220nF added.
• 2 x 5W 470Ω resistors to pull the gates high.
• 2 x 12V 1W zener diodes.
• 2 x MUR160 fast diodes
• 2 x 1/8W 10K carbon film resistors
• A soon to be measured inductor

The power consumption on 24V appears to hang around the 100W figure, pulling around 4A. As can be seen in the above pictures, I'm under the assumption that the not so great arcs are due to the higher RDS(on) of the MOSFET's I am using, but for its intended use, only a little bit of tweaking will be needed to "tune" it so it's perfect. Some modifications I am thinking of trying are winding larger/smaller inductors (once I get my cheap inductance meter), as well as changing the number of turns on the FBT. I may also up the size of the capacitor array.

Either way, it should run well as an ignition source for my soon to be oil burner.

Thanks for the read!