Small Solid State Tesla Coil

Solid State Tesla Coil (SSTC) is a variation of Tesla Coil in which primary winding of the resonance transformer is continuously or semi-continuously driven with high frequency by semiconductor based inverter instead of classical spark-gap pulse drive. This setup is much safer and more controllable than "classical" Tesla Coil making it an ideal high voltage toy . My SSTC consists a half-wave rectifier (I'm using half-wave rectifier instead of full-wave because i wanted my coil to produce 50Hz humming noise ) , ballast resistor , filtering capacitor and a half-bridge inverter built with four BUZ90A MOSFETs. Ballast resistor is needed because the primary winding of the Tesla is driven in resonance and needs some kind of current limiting . Details of the circuit can be seen on the schametic below.

Here are some pictures of entrails of the generator . On the first you can see controller board with drive transformer wound on small ferrite core. The second and third one show the halfbridge board mounted on heatsink with fan and the ballast resistor made from cheap hairdryer.

On the next pictures you can see completed coil and some results obtained with it. The topload of the coil is made from two aluminium plates and a wooden cyllinder wrapped with aluminium foil.

And finally two videos of experiments with the coil :