Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Topics - tefatronix

Pages: [1]
1

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...

2
Vacuum Tube Tesla Coils (VTTC) / Small VTTC project, PL500 based
« on: January 02, 2020, 01:14:38 AM »
Hello. Here is my small VTTC project based on the PL500 tube. I have built a few SSTCs and played with VTTCs before, but this is the first VTTC I finished and properly documented.

The Tesla coil runs directly from 230 V~ mains through a voltage doubler. It consumes 15-16 watts idle (filament only) or 40-80 watts depending on the power level set. The sparks are ~4 cm long. The secondary coil is about 8 cm tall, 3.2 cm thick and resonates at ~2.4 MHz.

Here is the schematic diagram:


It is a classic Class C  Armstrong-style oscillator.  Both L1 and L2 are wound on a 5 cm diameter PP pipe. L1 has 15 turns with several taps between turns 10 and 15. L2 has about 8 turns. C8 is built from three WIMA FKP1 1 nF/2 kV= capacitors in series (333 pF, 6 kV). Another 33 pF 3 kV capacitor is connected in parallel, giving a total capacitance around 370 pF.  I used a 13 V transformer with a voltage doubler (measured voltage 26-28 V with load) as I didn't have a proper reasonably sized 27 volt transformer.

The MOSFET circuit regulates the power. It's regulated by (dis)connecting the cathode. The mains voltage is half-wave rectified by D1. R5, R6, RV1 form an adjustable divider. If the voltage on the output of this divider gets high enough, neon lamps X1, X2 (strike voltage around 80 V per lamp) turn on and their voltage drop decreases, increasing G-S voltage of Q1, turning it on. If the voltage on the divider output drops, the lamps turn off and Q1 also turns off. This limits the operating duty cycle, decreasing heating while maintaining spark length.

Here is the entire device:


It is mounted on a pertinax (phenolic resin filled, I think) board. The circuit board is uncovered (a bit of a safety hazard). The PCB was designed and laid out by hand with an etch-resistant marker, as I was too lazy to make KiCad footprints for several parts that weren't there.

And here it's operating:


Bigger sparks could probably be achieved with a more powerful (PL504) or less worn tube, but it works OK.  Hopefully I'll get hold of some 6P45S or PL509 tubes for my next VTTC project (maybe) to be able to push the power higher without damaging the tube.
Video link: https://www.youtube.com/watch?v=BtGX9NkrPT8[/attachment]

3
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  ;D )

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.

Pages: [1]

* Recent Topics and Posts

post Re: Tesla coil Toroid Aluminium tape benefit
[Spark Gap Tesla Coils (SGTC)]
Jun
Today at 12:35:06 PM
post Re: FPS4000
[High Speed Filming]
Mads Barnkob
Today at 11:29:58 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
Today at 08:28:28 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ritaismyconscience
Today at 06:27:40 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
Today at 06:20:04 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ritaismyconscience
Today at 04:23:50 AM
post Re: Tesla coil Toroid Aluminium tape benefit
[Spark Gap Tesla Coils (SGTC)]
Mads Barnkob
February 24, 2020, 02:53:13 PM
post Tesla coil Toroid Aluminium tape benefit
[Spark Gap Tesla Coils (SGTC)]
Jun
February 24, 2020, 02:38:29 PM
post Re: NST
[Spark Gap Tesla Coils (SGTC)]
Jun
February 24, 2020, 02:30:28 PM
post FPS4000
[High Speed Filming]
Hoser415
February 24, 2020, 02:21:50 PM
post Re: HP T620 thin to plus conversion....
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
Mads Barnkob
February 24, 2020, 09:09:33 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ritaismyconscience
February 24, 2020, 07:08:30 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
February 24, 2020, 04:37:33 AM
post Re: DIY 250W LED Flood Light for High Speed Filming
[Light, Lasers and Optics]
Mads Barnkob
February 23, 2020, 09:04:34 PM
post HP T620 thin to plus conversion....
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
spacecabbie
February 23, 2020, 02:03:15 PM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ritaismyconscience
February 23, 2020, 05:43:17 AM
post Re: 230 volts spark gap
[Spark Gap Tesla Coils (SGTC)]
klugesmith
February 23, 2020, 04:07:51 AM
post Finding accelerometer location inside a phone
[Smart Phones]
haversin
February 22, 2020, 07:23:28 PM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
dj.cosmo.esq
February 22, 2020, 07:41:18 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ritaismyconscience
February 22, 2020, 06:49:22 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
February 22, 2020, 03:39:10 AM
post Re: 230 volts spark gap
[Spark Gap Tesla Coils (SGTC)]
Quentief
February 22, 2020, 02:32:55 AM
post Re: 230 volts spark gap
[Spark Gap Tesla Coils (SGTC)]
klugesmith
February 22, 2020, 02:10:34 AM
post Re: 230 volts spark gap
[Spark Gap Tesla Coils (SGTC)]
Quentief
February 22, 2020, 01:27:41 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Hydron
February 21, 2020, 08:00:10 PM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
February 21, 2020, 02:44:44 PM
post Re: 230 volts spark gap
[Spark Gap Tesla Coils (SGTC)]
klugesmith
February 21, 2020, 07:21:13 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ritaismyconscience
February 21, 2020, 06:11:32 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
February 21, 2020, 04:42:34 AM
post Re: 230 volts spark gap
[Spark Gap Tesla Coils (SGTC)]
davekni
February 21, 2020, 04:37:53 AM
post Re: UV-cured cyanoacrylate glues?
[Light, Lasers and Optics]
Twospoons
February 21, 2020, 04:28:33 AM
post Re: UV-cured cyanoacrylate glues?
[Light, Lasers and Optics]
klugesmith
February 21, 2020, 04:21:31 AM
post GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ritaismyconscience
February 21, 2020, 02:41:03 AM
post Re: 230 volts spark gap
[Spark Gap Tesla Coils (SGTC)]
Quentief
February 21, 2020, 12:28:20 AM
post Re: UV-cured cyanoacrylate glues?
[Light, Lasers and Optics]
Twospoons
February 20, 2020, 09:45:21 PM
post Re: UV-cured cyanoacrylate glues?
[Light, Lasers and Optics]
klugesmith
February 20, 2020, 07:28:01 PM
post Re: Help!Capacitor that burns out after a while!
[Voltage Multipliers]
Uspring
February 20, 2020, 02:06:26 PM
post Re: UV-cured cyanoacrylate glues?
[Light, Lasers and Optics]
shrad
February 20, 2020, 10:38:01 AM
post Re: Help!Capacitor that burns out after a while!
[Voltage Multipliers]
davekni
February 20, 2020, 05:14:43 AM
post Re: Is this flyback OK for my Plasma ball ?
[Transformer (Ferrite Core)]
davekni
February 20, 2020, 05:04:50 AM
post Re: Help!Capacitor that burns out after a while!
[Voltage Multipliers]
klugesmith
February 20, 2020, 04:47:41 AM
post Re: Help!Capacitor that burns out after a while!
[Voltage Multipliers]
Peregrine
February 19, 2020, 07:29:23 PM
post Re: Help!Capacitor that burns out after a while!
[Voltage Multipliers]
Peregrine
February 19, 2020, 06:47:55 PM
post Re: Help!Capacitor that burns out after a while!
[Voltage Multipliers]
Peregrine
February 19, 2020, 06:45:23 PM
post Re: Help!Capacitor that burns out after a while!
[Voltage Multipliers]
Teravolt
February 19, 2020, 06:41:42 PM
post Re: Is this flyback OK for my Plasma ball ?
[Transformer (Ferrite Core)]
John123
February 19, 2020, 06:10:34 PM
post Re: Help!Capacitor that burns out after a while!
[Voltage Multipliers]
MRMILSTAR
February 19, 2020, 05:52:20 PM
post Re: Is this flyback OK for my Plasma ball ?
[Transformer (Ferrite Core)]
ElectroXa
February 19, 2020, 05:05:50 PM
post Re: Is this flyback OK for my Plasma ball ?
[Transformer (Ferrite Core)]
John123
February 19, 2020, 04:11:22 PM
post Re: Help!Capacitor that burns out after a while!
[Voltage Multipliers]
Uspring
February 19, 2020, 02:03:12 PM

SimplePortal 2.3.6 © 2008-2014, SimplePortal