Tesla coil is a type of resonant transformer, where the voltage output from the secondary turn is not dependent on the turns ratio between primary and secondary turns, but dependent on the square root of the ratio between primary inductance and secondary inductance.
Here is my first attempt on building a mini Tesla coil. The secondary coil (where the sparks will be observed) is a 500-turn winding, wound around a kitchen naptkin's cardboard roll of 5cm outer diameter and of 20cm length. The primary coil is 8-turn winding, wound around a big glue tape roller of about 9cm outer diameter. I drive this coil using ZVS power oscillator (see schematic here) but using different type of capacitor (1uF, non polar). Like no other configuration of the ZVS, this new configuration of ZVS i ve been using rendered the MOSFETs very hot after 1 minute running time, forcing me to put heatsinks on each MOSFET.
Here is the schematic of the tesla coil from the high voltage output. The diode is already in the flyback transformer that receives oscilated current from the ZVS circuit.
I m still improving the design to get larger spark and less hot transistors. See ya later.