So for my first real flyback driver, I built a dual 2n3055 transistor based flyback driver. The gist of it is that while one 2n3055 overheats very quickly, 2 paralleled 2n3055s will be able to split the current load and avoid overheating too rapidly.
I used a long terminal strip to arrange the resistor components, had a fan on the heatsink to cool it down, and used some alligator clip leads to make a chicken stick for the HV side.
Once I had the driver setup I was able to push up to 30V at 3-4A into the driver with only moderate heating of the transistors. Short hot arcs or long-duration arcs cause the transistors to heat up significantly, and a short cooldown time is required for the heat to transfer over to the heatsink where it is quickly dissipated. After I figured this out, I was able to push up to 5A (max capabilities of my PSU), where arc over of the flyback pins started to occur, melting charring one of the alligator clip insulating boots slightly.
After I solved the arcover problem with some extra plastic insulation, the fun began, I strung together 3, then 4 disposable camera flash tubes. When you connect a flash tube directly to the flyback, it has a dim arc inside the tube, but I suppose the slight capacitance of the wiring creates a much brighter flash whenever a momentary arc forms.
Another interesting discovery I made was that at these voltages, everything behaves differently, particularly electrostatic attraction/repulsion, and magnetism. At HV, tissue paper flies away from the negative lead, and camera flash tubes roll away, you’ll have noticed that I had to tape down the tubes earlier because they continued to roll away. Whenever an arc formed, the HV leads would jump slightly as the arc formed too, I can only imagine that this would be even more near a magnet.
The schematic (source: wiki.4hv.org) of the driver is fairly straightforward, the only issue I had was remembering that the feedback coil had to be reversed. The basis for this circuit is that there is always current flowing into the base of the 2n3055, and that when the primary coil energizes, the magnetic field of the transformer core cancels out the voltage in the feedback coil, turning off the transistor, which allows the feedback coil to come back up to voltage, and the cycle repeats. A similar driver exists where 2 2n3055’s are set in a push-pull configuration for full-wave AC input, which is my next step, followed by a Mazilli ZVS driver with IRFP250’s. Until then, this driver should be useful, right up until I burn out the secondary that is 😀