Complete information on working SM style device.

[turbo]

 Take a close look at the CTC-5 chasiss

[zerotensor]

Attached is a tested print for a Spherics Type circuit.
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@all
here is a controller circuit I have designed and tested -- it works perfectly in practice --
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Looks good - just make sure you put protection diodes across the coils to prevent back-emf from destroying the AND-gates and oscillator.

[zerotensor]

Looks good - just make sure you put protection diodes across the coils to prevent back-emf from destroying the AND-gates and oscillator.

And / or OR or NOR or NAND or XOR or ... fffftttt.    The LOGIC.  Protect the logic.

[MarkSnoswell]

Looks good - just make sure you put protection diodes across the coils to prevent back-emf from destroying the AND-gates and oscillator.

The half bridge design that is not only tested and working it's got lots of protection as well... way more robust than anything I have found yet. It should even be better than any of the SSTC (Solid State Tesla Coil) drivers out there.

[MarkSnoswell]

Half Bridge switch circuit is too big to load here --  and it needs documenting. However here are some tips for getting fast switching:

1. 12 - 24 V gate drive -- faster at the higher voltage.
2. use IRF 820 or other mosfet with low gate capacitance and gate charge -- you want voltage not current.
3. Use ceramic bypass cap on the HV supply -- I use 0.1u 630V cermaic + 0.15 pulse capacitor. THese caps should be right on the mosfets.
4. Fastest driver you will get (at resonable price) is IXYX 414  use the TO 220 package if you want to drive at over 700K repetition rate.

When you do get things switching fast you will need to minimize the gate to drain capacitance and shelid any circuitry within about 50cm -- the EMI is very significant if your switching 100V + in less than 10 ns. If you dont sheild and lay things out right then you glitch your input and get spurious triggering of the switch. You will also need to isolate your logic, driver and output earth lines as much as possible.

You should have TVS's on all power rails -- logic, low side and high side drivers and HV supply. you want schottkey diodes in seris with the mosfets to prevent their body diodes ever getting reverse biased, You also need hyperfast (or SiC) flyback diodes. If you do all of this your mosfets and drivers are likely to last -- if you dont you will blow them regularly.

When testing use 10x or preferable 100x probes on a 100MHz or faster scope. For cleanest results do not touch the output -- just place the scope tip close by.