[Development] Project of an SSTC driver.

[Bambinz]

Dear all,
I am developing a new SSTC driver to drive my small teslacoil, because the current driver is not very reliable.

The characteristic will be the followings:
   - Half-bridge configuration
   - Feedback on the secondary with an current trasformer.
   - 2x Separated Board: 1 board for the driver and one board for the half bridge
   - Measure of the primary current
   - Measure of the switch frequency
   - Measure of the mosfet temperature
   - UVLO (under voltage protection)
   - Mosfet protection (Gate protection with zener, Drain-Source protection with snubber and TVS)
   - Minimized connection inductance to allow high current switching at high frequency.
   - Microcontroller STM32F103 to acquire the data, enable/disable the driver in the case of fault condition and generate the interrupt signal.
   - Wi-Fi connect with an ESP32 to send all acquired data to an computer software and to receive the Frequency and duty-cycle of the interrupter, in addition in future to stream the music

If you have any suggestion please write me!!!
I have completed the bridge schematic, tomorrow I will post them.

[oneKone]

Sounds like an interesting project. I'm assuming your going to measure the switching frequency from secondary current feedback?

[Bambinz]

Yes, I will read the switching frequency from the secondary current feedback, that will be also the driving signal for the driver.

In addition, I would try to implement a ZCS (Zero-current-switch) by reading the primary current and then by using a zero zero cross detector to enable the driver only near the zero current. But i think that will be difficult at 1MHz.

[Netzpfuscher]

If you are planning to have a PC application you can take a look at our Teslaterm: https://github.com/Netzpfuscher/Teslaterm/tree/typescript
I also have a ESP32 Interface: https://github.com/Netzpfuscher/UD3_ESP32

Teslaterm is very flexible. It's not specifically designed for UD3. You can send text to the terminal window and use the c library to send telemetry like scope data or data for the gauges. I even have simple graphics functions for sending text/lines/colors from the microcontroller to the terminal screen.

[Bambinz]

Thank you very much for the indication. The software is fantastic!
I will try to adapt the software with my data.
Eventually, I will rebuild a simplified interface with python

[Bambinz]

This is the schematic of the half-bridge:

[Bambinz]

I would like to make some changes in the driver.
I have found a 440VA 53VAC transformer that I would like to use for the next teslacoil.

Therefore VDC will be +- 75V (that can reach +-90 without load), therefore I have choosed a mosfet of 250Vds ->  IRFB4229
With a very short and semplified thermal calculation, result that can handle about 55A with the interrupter set to 20Hz and duty-cycle of 5% (Setted as worst case).

I would like to have the same carachteristic of the small coil with an high peak current and a low duty-cycle to have an low mean power and an high pulse power.

Thereticaly the small teslacoil have an peak current of about 30A, with a 24V supply and a push-pull driver will results in a 30A*24V*2= 1440W (peak power) and an average power of 40W. The results is about 7-8cm of spark.

Therefore the average current will be about: 55A * 0.05 = 2.75A with an average power of 75V*2.75 = 206W. And a Peak power of about 75V*55A =4125W

Therefore we will have a 4x power therefore I will expect a sparklength in the range of 30cm. Can be correct?

[Bambinz]

I have just ordered the board from PCBWay for the driver. I hope that all works good xD
In the next day I will post the complete schematic

[Mads Barnkob]

I would like to make some changes in the driver.
I have found a 440VA 53VAC transformer that I would like to use for the next teslacoil.

Therefore VDC will be +- 75V (that can reach +-90 without load), therefore I have choosed a mosfet of 250Vds ->  IRFB4229
With a very short and semplified thermal calculation, result that can handle about 55A with the interrupter set to 20Hz and duty-cycle of 5% (Setted as worst case).

I would like to have the same carachteristic of the small coil with an high peak current and a low duty-cycle to have an low mean power and an high pulse power.

Thereticaly the small teslacoil have an peak current of about 30A, with a 24V supply and a push-pull driver will results in a 30A*24V*2= 1440W (peak power) and an average power of 40W. The results is about 7-8cm of spark.

Therefore the average current will be about: 55A * 0.05 = 2.75A with an average power of 75V*2.75 = 206W. And a Peak power of about 75V*55A =4125W

Therefore we will have a 4x power therefore I will expect a sparklength in the range of 30cm. Can be correct?

Spark length estimation for SSTC was never really linear in my experiments, it felt more like that I could just keep adding topload capacitance to get longer arcs