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Registered Member #1938
Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 699
My first SSTC is a high frequency solid state tesla coil. Complete construction details here: my blog In only uses one mosfet (IRFP 460) and runs on 50V to 100V input voltage.
Registered Member #1938
Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 699
Thank you all for the appreciation.
@raff, the IRFP460 produced better results then the IRFP260, but it is true that the coil was already tuned for the IRFP460 when I tested the 260 (without re-tweaking it for the new mosfet). However with the IRFP 260 I had no sparks, not even when touching the breakpoint with the screwdriver.
@Mads, I suspect it is ~4.6MHz, but I currently do not have the tools to measure it correctly.
Registered Member #1025
Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566
Hi, Cool - I like the simplicity.
I have few comments. How you can be sure your FET is turned on fully? I mean, this concept is originally developed for bipolar transitors. And same question from the other side - How you can be sure, that your gate is not exposed to overvoltage. I suggest as solution to use some transils or zeners to clamp the voltage at 15V. Than you could add few more turns until the diodes get hot (but not too much). Than you can be sure your FET gets what she needs. It’s just a suggestion but might be improvement for your concept.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
I have been thinking about this concept too, your design could probably be improved by putting a diode in series with the drain (to not distort the sine wave) and using a gate self-biasing circuit (so the FET conducts only a fraction of the cycle like in a VTTC). Of course the gate voltage should be always clamped by two 20V "back to back" zeners.
Registered Member #1938
Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 699
Mates, Dr. Kilovolt, thanks for the good suggestions.
Indeed, most probably, the gate is driven in overvolted mode and this might just be what it needs to fully open the mosfet but... will kill it eventually.
I was thinking of adding a zenner myself, so I'll check this and report back. I would like to know more on the purpose of "Than you could add few more turns until the diodes get hot (but not too much). " To obtain resonance, I've moved the primary+feedback coils closer or further over the secondary coil (embedded inside the visible tube).. Regarding the Mosfet.... SHE? never knew that
Dr.Kilovolt, I would need more details for the self-biasing gate circuit .
To power this coil, I'm using a 24V/10A max power source. The alternating current goes through a voltage tripler (3x3300uF caps), so I get aprox. 100V when no load is connected. The problem is that there are some high voltage spikes going back to my power source. What protection should work best?
vasil also suggested connecting small caps between he wires comming from the coil and the ground.
currently the driver circuit is not shielded, should this be of any concern? The RF field is quite strong in the close proximity of the operating coil.
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High Frequency Solid State Tesla Coil
never knew that 