Mosfet stack for higher breakdown voltage

[d3x0r]

Why always so many solutions!!! Couldn't it be just one for every problem??? hahaha

Magpwr, it's for experimentation and not for productivity. But, you are right. I should start considering the cost also! By the way, heat-sinks were taken from an aluminum door rail. see in pic.

d3x0r, firefox prevents me for opening this site. I'll try to locate it thanks

Frirz i thought that ign. coils don't go over 25KV but i'll give it a try. I think that i have two transformers 220V to 12V. I'll make an isolation with them and fire it. I have used ign. coil again driving it with an IRfP460. Never thought of driving it from the main supply.

Sorry to hear that....
http://cmosedu.com/jbaker/papers/1993/RSI641993.pdf


I guess it can be simpler than the magnetically isolated system....  (attached both)

[Magluvin]

Just to throw some in from the other end of the spectrum....

I have a couple mosfets I got out of vehicle control modules and the specs are up there in amps compared to what Im used to for the size. Will have to look and see if there are others.

IRF3205s

55v max
110A   390A peak     In a TO-220 chopped into a D2 pak   
.008 ohm max        Nice

Then I also have BUK954R2 55b TO-220

55v max
75A  765A peak 10us pulse
.0035 ohm.  Nicer  Im wondering why they use relays at all anymore.

Mags

[fritz]

Why always so many solutions!!! Couldn't it be just one for every problem??? hahaha

It depends on. "Engineering" solutions are typically not the same stuff needed for experimenting.
Having fun with HV switching mosfets does not mean that you have to get a master degree in mosfet driver circuits.
But burning up entire stacks of mosfets with poor outcome is what we want to avoid.
The approach driving the gates with caps from a single driver has its drawbacks....
An "experimenting" approach could be to use a 12V battery (as used in keyrings...) for each mosfet as driving supply,
back it up with caps 10u ?, having a 4049/50 setup (for each mosfet) to get the gate pulses right - and isolate that (module) using an optocoupler.
If the voltage span exceeds the creepage of the optocoupler - make intermediate branch modules with one additional opto input and n outputs using 4049/50 and a battery as for the driver. 
Instead of the optos you could use toslink cables, toslink receivers+emitters.... if you get them cheap from somewhere.

That would be a universal setup of mosfet modules, can be stuffed with any mosfet you can find... and if the experiment is done - can be used for something else. Resistors on the HV side should be used to distribute the HV evenly over the turned-off fets (thats another safeguard to protect the fets)

Frirz i thought that ign. coils don't go over 25KV but i'll give it a try. I think that i have two transformers 220V to 12V. I'll make an isolation with them and fire it. I have used ign. coil again driving it with an IRfP460. Never thought of driving it from the main supply.

As long as you use "motor" kind of timing and "12V" - the 25kV might be right.
I remember somewhat more impressing sparks using more than 12V and few Hz timing. ;-))))

rgds.