Continuous Wave DRSSTC circuit as Plasma Speaker

lostengineer, Thu Sept 21 2017, 07:09PM

Ok guys, I've been playing around with Plasma Speaker circuits for a while now. I have a standard design that works ok based on TL494 to UCC37322 to GDT to MOSFET H-BRIDGE topology. Output transformer is a Flyback. My schematic and PCB design for this Plasma Speaker is attached. The problem with this circuit is the extreme heat it generates in the FETs. I believe this is caused by resistive losses due to hard switching the FETs but I'm not positive. I occasionally blow a couple FETs if I turn the power up too much (operating around 40VDC @ ~10A).

My new idea is to make a small DRSSTC circuit and use it to drive a Flyback transformer primary in Continuous Wave mode but at very low power levels. The "interrupter signal" for the mini DRSSTC will be the same TL494 modulator so I can feed the system music the same way as my previous Plasma Speaker designs. I'm hoping that my making this into a DRSSTC style circuit with primary current feedback the FETs won't heat up nearly as much and the circuit will be much more efficient overall.

I plan to find the resonant frequency of the Flyback transformer with my current plasma speaker design. I'll simply adjust frequency until I get the largest arc. I'll record this frequency and save for later. I'll measure the inductance of the flyback primary coil. I'll then calculate the needed series capacitance to achieve a tank circuit that resonates at my previously chosen flyback freq. In this manner, it's not really a DRSSTC - It's just singularly resonant in the primary circuit.

The controller for this Plasma Speaker is a direct copy of the oneTesla control circuit with my TL494 modulator added on board.

If this design works, I'll make a nicer complete pcb with all SMD components. Maybe I'll even add bluetooth audio module.

Images of all board designs and schematics are on imgur in the links below. Sorry the attachment feature was not working for me. Do you think this will work?

original design:
https://imgur.com/ZuwMoHj

https://imgur.com/FcnTp6J


new design:
https://imgur.com/WEJgX86

https://imgur.com/9pTMJtV

Trying again with the pictures:

original design:










new design: