Tesla coil driver revisited.

[Exidor]

 

[Exidor]

The above circuit is a working Tesla coil driver. It could use being optimized though. I am trying to choose the best mosfet for maximum output. My schematic editor is limited and that’s the best I was able to do. Any comments?

 

[duke37]

Tell us how it works!

You have three or four diodes near the fet which seem to be surplus to requirements.
The potentiometer could be of much higher resistance, using less power and not getting as hot
Obviously, the fet should be capable of switching 1kV, this is outside my area of knowledge.

Does it rely on a spark for feedback?

 

[Exidor]

The extra diodes are to protect the transistor and reduce its heating. The potentiometer and feeding resistor are low to allow the transistor gate to discharge better because of the gates capacitance (~ 5000pF), something I had read about. Positive feedback from the Tesla secondary coil makes it go into oscillation. It will arc an inch or two.

 

[duke37]

The diodes are connected across zener diodes. Are the zeners adequate to the task on their own?
There is no limit to the fet current. A self oscillating junction transistor will have a very low gain at very high currents so will turn off. The fet not so.
Consider using a separate oscillator (555?) driving a fet driver capable of amps based at zero volts and only raised when an output is required. The fet will then have lower disipation and the pulse frequency and duration can be set so that the fet is not damaged. An oscilloscope or a big bag of transistors will be required.