Audio Modulated Solid State Tesla Coil

Yes, although you won't want to use a voltage doubler, and you'll need to use higher voltage rated FETs/IGBTs. Are you going for an SSTC or a DRSSTC?

Unfortunately, when I tried raising the voltage to 120VAC, all my MOSFETs started popping, I need to get some better ones.... Did you try building a coil with your ZVS driver? I've seen quite a few impressive ones on youtube.

To answer your question about the GDT, I used 16 turns of 22 AWG wire (22 or 23 SWG) on a 1.5" diameter ferrite core. The GDT is one of those components that you will need to experiment with. I do not have an oscilloscope ( D= ), so I have not tested the output waveform, I just tried it and it happened to work. If you get a nice square wave signal on the secondary side, then you are fine. Use larger components rather than smaller ones, most gate drivers can handle quite a bit of current, and it's better to have a beefier GDT than to have one that won't provide enough current to turn the MOSFETs all the way on. Good luck!

-Xellers

What MOSFETs are you using? My IRFP260s were good for 80VAC, but my IRFP460s (high voltage rating, lower current rating) were useless even at that voltage. All of the schematics I've seen use a variac to bring the voltage up slowly, so it's definitely worth a shot, but I'm not sure why, since the dV/dt is still the same when the device turns on and that's my guess as to what's killing it. It could also be my GDT, my signal might not be a square wave or it might not be strong enough, either one could prevent the gates from saturating properly.

Just out of curiosity, are you using one of the CD4046 feedback/VCO designs for your SSTC? Unfortunately, I never managed to get my PLL version working, and I'd like to see what you are able to come up with.

I'm planning on buying a variac and some new MOSFETs and IGBTs for experimentation - I'll try to post something new soon. As a sidenote, if you're afraid of killing transistors but want to experiment, I'd suggest something like Steve Ward's Class E SSTC. I assembled a small, single transistor Class E in about an afternoon and it worked great (until I tried to run it in CW - hint: don't do that =P ). However, be warned that if you don't add some sort of GDT, his schematic has the tendency to kill gate drive chips...

Actually, I managed to get it working pretty decently, the maximum spark length was about an inch in CW with 45V or 90V input (can't remember which it was). The original reason I switched to a GDT-based design was that my UCCs kept dying without one!

Thank you for your comment =] The Tesla Coil I built here closely resembles Steve Ward's Mini SSTC - I found that his feedback driven oscillator design was the simplest and (in my opinion) the most elegant way to built my first coil. In essence, a signal from an antenna is amplified by a 74HC14 inverter chip (two inverters are in series to make a buffer) and then sent through a gate drive transformer after further amplification by push-pull arrangement of two gate driver chips (one is inverting and the other isn't - I used the UCC37322 and UCC37321 because they are available as free samples from TI). The signal from the gate drive transformer then siwtches a half bridge of IRFP260 MOSFETs. Additionally, an astable 555 timer chip with variable frequency and pulse width switches the gate drive chips on and off through their enable pins. One interesting feature about this circuit is that no startup circuitry is required as the 74HC14 chip will send a short pulse to the UCC gate drivers on startup (at least that is my theory).

Yes, a ZVS driver will work well with this type of coil and can be made even with almost any modern flyback. However, before you go to more power, try tuning your secondary circuit. After I tuned by coil a bit, I managed to get 5" to 6" long sparks with a 24VDC 555 timer driver and transistor from an old TV. Also, try winding a larger coil and adding a topload, such as toroid made by wrapping AL foil around a circular fluorescent tube.

Are we talking about the same thing? I'm not talking about my SSTC, I'm talking about my LOPT-powered DC SGTC. Also, a 555 timer should still be used for starting up any SSTC because if the coil stops oscillating from feedback (which can happen when you draw a spark to a grounded probe), then the timer will compensate and the SSTC will not turn off.

Driving the FETs directly is always a possible, however, the GDT is there to protect and isolate the logic components from the power components. Just in case of any sort of unwanted feedback or high voltage spike, the GDT keeps the driver chips (more or less) safe and keeps the logic power supply safe. It also serves to isolate transistors that may be driven by the same signal. Driving the coil without the GDT might work for a few short runs, but don't expect much before a driver chip blows. Usually, the GDT is the one thing that keeps people away from SSTCs, but it is not a difficult component to fabricate and even a sloppy-wound transformer will work (albeit not a well as one wound wound rightly with trifler wire).

With this particular Tesla Coil, it is safe to touch the sparks because the current is very low. However, just because it "works on AC [sic]" that doesn't mean it is safe! Try shorting out a microwave oven transformer (also "works on AC [sic]") with your body and then telling me it's safe! In fact, you probably won't be able to say much at all afterward, that is, if you survive.

I'm just posting this as a preview to what is coming; I am building a larger PLL SSTC and will be sure to make an instructable when it is finished =]

Actually, this coil produces surprisingly little ozone; the sparks are long, hot, and VTTC-like unlike this SGTC-type sparks that produce copious amounts of ozone.