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I'm new in SSTC building. On my last experiment my Tesla Coil was working only about 10 seconds and mosfets were exploded. SSTC is Half-bridge. How i can protect the mosfets ? Across mosfet's Drain and Source are connected ultrafast diode and schottky diode connected to mosfet's drain. Will it be better, if I’ll connect TVSs between mosfet's Drain and Source? Or I connect bipolar capacitors across diode bridge output? What can You advice for me?
Registered Member #1025
Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566
10s is a good start. It looks you pumping to much of amps over your transistors. You should enhance the coupling by adding more turns on your primary. Proper cooling is also important.
TVS are always good part of any HV circuit, I even prefer paralleling of minimum two per transistor.
It's also important to have long and sharp breakout point and also tune your coil on lower volatge properly before you go on the mains.
More help you can get after you post your scheme... Don't give up!
I used UCC's signal "amplifier", because I think UCCs haven't enough power to drive GDT and mosfets normally. Signal comes from UCC to this driver, and then it goes to GDT.
Half-Bridge (but I haven’t used gate resistors; my mosfets have internal zener diodes):
GDT form coilcraft - SD250-3L.
Now I'm going to use CT for the PLL feedback. Would it will be better than antenna?
Thanks, Mates. My mosfets are 29A, 500V. Secondary is 11 cm diameter and 38 cm height. Wire – 0,25 mm. Primary is form 3 mm wire, 6 turns. I’ll add TVSs across the mosfets.
Registered Member #618
Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628
The UCC chips are the chips of choice, I'm sure everyone else here would agree with me. The standard 322 and 321 pump out 9A max each....more then enough to drive a GDT.
UCCs are only 350mW, when my driver is more than 20W.
First of all, I have tried connecting my SSTC to 12V power supply. Sparks was less than 0,5cm and UCC were heating. When I soldered that amplifier and connected it, sparks were more than 1cm. Now UCCs only switching 4 amplifier’s mosfets. And that mosfets aren’t heating.
Registered Member #1025
Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566
In case your UCC's are heating up than add more turns on your gate transformer...They should stay cold. Also six turns of primary could be your problem, since your fets exploded it looks like overcurrent problem...
I can’t add more turns, because my GDT is form coilcraft (SD250-3L) or will be better, if I make my own GDT? But with that amplifier UCCs stay cold and mosfets on amplifier too. It look works perfect, but I don’t now, what are on and off times, because I haven’t oscilloscope.
1. How power and voltage TVS I need for 500V and 29A diode ? Power supply for SSTC is 220V. 2. TVS connecting across mosfet drain and source with no more components ?
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Need help with my SSTC
