H-bridge of 40N60 mini-brick IGBTs

Posted on Feb 6, 2014

This first DRSSTC of mine evolved from the ISSTC work I had been doing at the time. Talking with Jimmy Hynes, who built the first DRSSTC, I decided I would give it a try, though with some changes from his design. Jimmy`s DRSSTC used an oscillator to generate the high frequency signal that drives the coil (about 66khz for his coil, I believe). Sinc

H-bridge of 40N60 mini-brick IGBTs
Click here to download the full size of the above Circuit.

e I`m not a big fan of using VCOs to tune tesla coils, I would use feedback from the secondary coil itself, ensuring that my driver was always in tune. I would then have to tune the primary circuit to this operating frequency. My feedback design started out very simple, and is seen below: The first schematic was what I originally used for my DRSSTCs. The second schematic is just a standard H-bridge, nothing too special there. I eventually made an important change to this very basic controller. The change was the addition of a JK flip flop, which would synchronize the interrupter turn off to the feedback zero crossing. This is important because with out this, the interrupter can disable the gate drivers during an RF half-cycle, where current could be very high. DRSSTCs rely on soft-switching, due to the resonant load. We try to avoid hard switching the several hundreds of amps that may be flowing through the primary circuit, as this is very hard on the IGBTs. Anyway, the flip flop ensures that this should not happen. Below is the schematic (updated 3/17/05): I still use the same basic schematic for the H-bridge, except now I use a voltage doubler at 140VAC, using a pair of 22000uf 200VDC electrolytic capacitors. These capacitors are much larger than needed, but they are what I had on hand. Here is how I make my GDTs. I take some cat-5 networking cable, and wrap 10 turns of it around a ferrite core. I then parallel all of the...

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