sstc drive method

[oneKone]

hey,

every now and then when i run my "big" sstc and occasionally blow some igbts, other times it works flawlessly. the problem is the breakout point and antenna needs to be positioned perfectly or else i start to have drive issues, essentially cutting out. 

so it got me thinking.... would it just be better to convert it to a pll driver and still interrupt it using the enable pins of the ucc3732x drivers.

any help is highly appreciated.

cheers.

[Laci]

I have a PLL driver circuit and it works great with my coil.The best thing about it in my opinion is that it can be audio modulated easily and makes great sounding CW arcs.This is the schematic: https://cdn.instructables.com/FXU/AK63/GRFN8J90/FXUAK63GRFN8J90.LARGE.gif

The IGBTs die due to overcurrent?I had the same problem with MOSFETs,but the problem was not the driving circuit,instead the long mains rectified power cable to the bridge.

[oneKone]

Cheers for the reply Laci. I messed around with a pll circuit but it had troubles staying in tune for some reason. I ended up making a circuit (nothing new about the design) that I'll post up. It's basically Steve wards sstc 5 driver, the design with a 555 to start the oscillation.

[Laci]

I am currently using the Kaizer SSTC I driver circuit and no need to start the oscillations.Maybe try a secondary base CT as feedback.

[Mads Barnkob]

I am not sure that a PLL controlled driver would like to be cut on and off like that, I do not know, I never made a PLL controlled coil. But it needs a few cycles to lock on the frequency, so maybe it could get bad, hopefully someone knows better?

I also had stuttering behaviour on the SSTC when spark length became too long, like it can be seen in this video from 0:50

[oneKone]

I've noticed your sstc ii had a metal enclosure, was it grounded?  My idea was to have the new driver enclosed for more reliable operation.

Laci, tbh I'm not sure why the driver is cutting out. I've tried both antenna and secondary CT feedback. I think it's due to emf or something along those lines.... But that's a big guess on my behalf

[Mads Barnkob]

I've noticed your sstc ii had a metal enclosure, was it grounded?  My idea was to have the new driver enclosed for more reliable operation.

Laci, tbh I'm not sure why the driver is cutting out. I've tried both antenna and secondary CT feedback. I think it's due to emf or something along those lines.... But that's a big guess on my behalf

Yes the shielding was grounded and that is crucial! It is a strong EMF to be in for this little driver, when I did the audio modulation, I also had to shield the cable to the driver enclosure and all the way to keyboard, but even then it would still lock up from time to time.

The only thing getting outside the enclosure is the antenna and GDT wires.