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Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
Pinky's Brain wrote ... Can electrolytics really not do fast rise times BTW? The affordable ones are obviously no good for complete pulse discharge, but looking around people seem to be getting pretty good rise times out of electrolytic fed IGBTs with small amounts of discharge.
Current risetime is all about ESL. People use combinations of different capacitors in parallel to get low Z across a wide frequency band.
You asked for solid-state solutions, but I'm going to point out a thread about krytrons in another forum. They have been used in laser systems, not just exploding systems. John Futter's response in that thread gives part numbers for HV solid state devices that switch in 4 ns.
Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837
That kinda defeats the cheap aim though.
As far as bucks per Watt is concerned the SGP15N120 and HGT1S10N120BNST look the most efficient ... both should do a couple 100 KWatt peak power in pulses if the sheets are to be believed. Which is pretty amazing compared to BJT/JFET/MOSFET (assuming the same ratio between continuous rated current and short circuit limits it's even cheaper than a big stack of those 6 cent 2n5551s in avalanche mode!). Pretty unimpressive compared to spark gaps of course, but you don't need hearing protection with the IGBTs.
Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
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Posts: 837
Okay, going to order some parts for a small solid state Marx based on Thyristors ... won't do fast pulses, because Thyristors aren't fast, but if I can manage a pulse a few microseconds long there might be ways to compress it without an air gap. In the mean time I'll just try to draw some sparks.
I was thinking 5 MPM-150N22/1000 150nf polypropylene caps per stage, with TYN616RG as a switch, for 1000 Volt per stage. Resistor charging for now. A small iron core toroid 1:1 transformer per thyristor with one wire looping through all of them for primary driven by an IGBT.
Anyone ever done anything like this? Don't see too many DIY solid state Marx out there except for a small two stage one.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Pinky's Brain wrote ...
Okay, going to order some parts for a small solid state Marx based on Thyristors ... won't do fast pulses, because Thyristors aren't fast, but if I can manage a pulse a few microseconds long there might be ways to compress it without an air gap. In the mean time I'll just try to draw some sparks.
I was thinking 5 MPM-150N22/1000 150nf polypropylene caps per stage, with TYN616RG as a switch, for 1000 Volt per stage. Resistor charging for now. A small iron core toroid 1:1 transformer per thyristor with one wire looping through all of them for primary driven by an IGBT.
Anyone ever done anything like this? Don't see too many DIY solid state Marx out there except for a small two stage one.
There's a circuit diagram for a thyristor-based MG here, Pinko - you could just scale it down.
Solid State Marx Generator Steven C. Glidden and Howard D. Sanders
Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837
My 75 cent thyristor doesn't exactly behave like the monsters in that paper though (also it's not a good circuit, putting a free wheeling diode across the cap+thyristor is a the easiest way to protect against a stage not firing).
Those things have specially shaped gates which can take a lot of current to get better rise times ... I don't know how small thyristors behave in that regard, they are certainly not specced for it.
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Looking for a low power fast solid state pulser design
