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Hey everyone, I think it's time I start to play around with solid state coils. I've made many spark gap designs, but this is gonna be my first truly SSTC :)
I was going to go with a TL494 driver, and a half bridge of IRFP260N MOSFETs. Unfortunately my secondaries resonant frequency is way above the 300kHz capability of the TL494. So the way I see it i'm gonna have to go with one of Steve Wards designs, which seeing all the success people have with them, is no sacrifice for me. :)
After I make a basic SSTC, I wanna advance into making it a DRSSTC. I wanted to just jump right into a DRSSTC, but after a little research I'm gonna start with a basic SSTC and go from there.
What I've done so far:
Wound the secondary - around 1100 turns of AWG40 on a 33mm diameter form, 10.65cm winding length
Registered Member #2919
Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652
If this is the secondary you were talking about in the other thread with a loaded f0 of 600 KHz, be warned that the TL494 will not be able to reliably output a 600 KHz signal; they are only spec'd up to 300 KHz.
Yes it is, and yeah I seen that going through the datasheet earlier. I'm hoping to be able to get the frequency low enough on the secondary that it will be at least somewhat acceptable.
Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
For smaller SSTC systems I will always recommend using a wider secondary, you lower the frequency a great deal that way and still keep it fairly small in height.
Great job on the winding, I did it by hand, maybe that is why it took 6 days :)
Considering I have no wire left, I'll have to bear with the one I've already wound. Thanks btw, and I'm way too impatient to wind by hand so hats off to you and everyone else :)
I've also made a topload like you did, using the bottoms of 2 cans. I've done some math with your specs and found that the topload should yield a capacitance of around 1.716 pF It's a very rough guess as I just threw some numbers in to the equations to make it easier, but it's a starting point for tuning purposes :)
Sorry for the double post, but I have a quick question, if I were to use rectified mains which is 170VDC, I would definitely see a peak to peak over the voltage of my MOSFETS (200V) My question is, is can I use a zener diode and MOSFET setup to lower the voltage to around 120VDC. I've seen people using a setup using a few zener diodes, resistors, and a MOSFET to lower 270VDC to 220VDC for tube operation. Can't remember where though. O.o
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
170v is fine for a bridge of mosfets. There can be spikes, but mosfets are rated for avalanche, so they will just burn off alot of heat if the voltage gets too high. As long as this power can be dissipated fast enough to keep the die within it's SSOA, it should be ok. This is what Steve Ward did for his halfbridge and fullbridge sstcs. Also, sorry or not you can just press the edit button to update a post instead of double posting.
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My First SSTC
