Hello,


I am thinking about building a small SSTC this year using Silicon Carbide FETs from UnitedSIC. This is the model I selected - UF3C065080K4S  (650 volt, 80 mOhm, 43 nC gate charge) and would like to drive them using the UCC21520 gate driver. In my calculations and simulations, the typical leakage of a GDT (few tens to hundred nH) would slow down the gate drive too much. The above mentioned MOSFETs are cascode configured as a SiC JFET driven by a Si MOSFET, so they can be driven like normal MOSFETs. Their specified rise/fall time is 8/20 nsec with 8.5 ohm gate resistance.


The planned specs are two of these FETs in half-bridge configuration at around 1 MHz in mains half-cycle "staccato" or filtered+interrupted mode with primary current around 20 amps RMS (which would give around 14 amps RMS per FET). Considering I am able to get ~30 (25-35 cm) sparks with my IRFP460N full bridge SSTC especially when in staccato mode with some 11-15 A RMS (there's 11 in the article but I changed it since) at 320 volts peak bus voltage, I think that half-bridge I might get sqrt((160*20)/(320*15)) times that spark length, so maybe 25 centimeters with decent reserve? With a really compact driver (aiming for ~8x8x5 cm  for ~10x5 cm secondary).


Another SiC FET, the C3M0280090D (900 volts, 280 mOhm) looks amazing for Class E HF SSTCs. That one might be pushable to upwards of 10 MHz (maybe 13.56 MHz ISM band?) as its damn crazy fast (10/7.5 ns rise/fall with 150 pF gate capacitance  and only 9.5 nC (!!!) gate charge). And isn't too expensive.


Are there any good tested (in SSTC duty) gate drivers for such high frequency applications? The well known TC44x2 or IXDD6xx are available even in a nice 5 lead TO220 package for simple heatsinking. All the more modern, fast gate drivers are either in not-so-easily solderable/heatsinkable packages or crazy expensive (IXRFDxxx).


Or is it plausible to run a driver like TC4422 or the IXDD drivers at 13.56 MHz, given that the loading capacitance is low enough and it's heatsinked decently? The propagation delay is already ~1/2 of the period...


Is there something one should watch out when using SiC FETs, except PCB layout being more critical and asymmetric gate drive for non-cascode types? The non-cascode types have no avalanche ratings, so I suppose those are more susceptible to overvoltage damage...

Hi all, I'm a student from the Czech Republic and this is my first post on this forum, in which I am going to show you my miniature Tesla coil.

I have already posted this in a few Facebook groups before, but in case anybody is interested, here it is.
This is my smallest Tesla coil, the circuit board measures 25x20 mm, the secondary coil has the following parameters: 14.3 MHz fres, 10 mm diameter, 25 mm winding height, 0.1 mm wire diameter.

It is very similar to Slayer exciters and to a self-oscillating coil another member posted here some time ago. The input stage uses extra 1N4148 diodes to decrease the capacitance of the Zener diodes and uses a simple circuit (zener, trimpot, some resistors) to slightly bias the MOSFET gate. The output stage wired in a class E like configuration, however I don't use any capacitor in parallel to the MOSFET's output, as it seems to be in tune even without it. I haven't measured the waveforms, as my scope is quite slow and its input capacitance is not negligible. The MOSFET I use here is an IRF510 - this one was chosen because of its low gate capacitance, low price, easy availability and fairly high speed (I think it would be quite challenging to get an IRFP460 to run at such frequencies  )

I built this coil to have an "improved version" to replace my previous nano Tesla coil, which got damaged and was very inefficient anyway (based on a BD139 NPN BJT in a very similar circuit to this one - it had a different bias circuit and a 150 pF tuning capacitor). I've already had this coil laying here for a few weeks or even months, but I was too lazy to write any documentation, but finally got myself to do it (full documentation is here).

This coil can run off a 12-14 volt power supply without overheating, it can momentarily tolerate higher voltages (I tested it at voltages over 24 V) as long as the input is pulsed, otherwise it will overheat fairly quickly. At voltages under approximately 15 V or so, the discharge has to be started manually with a piece of metal, etc.