5
\$\begingroup\$

I know that kind of things could be done by thyratrons, but wikipedia says that they are being phased out by semiconductor devices.

Could anyone suggest which kind of devices can switch on that fast and pass that much current? I've checked thyristors - and all I can get seems to be 1us switch-on time...

I don't need to have 1000A for more than 0.1-1 \$\mu\$S, so I have reasonable thermal budget.

That's for not-so-simple TEA laser.

\$\endgroup\$
1
  • 2
    \$\begingroup\$ Is thyrister an alternate spelling? I've always seen it spelled thyristor. I can fix the tags if you can fix the questions! \$\endgroup\$ Commented Oct 25, 2011 at 14:05

3 Answers 3

8
\$\begingroup\$

I can't be arsed to look up the actual switching time of a real device, but the current and voltage spells IGBT to me: http://en.wikipedia.org/wiki/Insulated-gate_bipolar_transistor

I know IGBTs are used for high power converters in places like windturbines and slow switching there would mean too high switching losses.

\$\endgroup\$
2
  • \$\begingroup\$ not sure how representative this is of all IGBTs, but the ones I know of could switch in around 1 microsecond. could be there are faster ones. \$\endgroup\$
    – JustJeff
    Commented Oct 25, 2011 at 10:36
  • \$\begingroup\$ Just found and ordered IGBT with 5ns rise time and 20ns turn on delay, should be just fine for me. Peak current not 1000A though, so will need to play around. \$\endgroup\$ Commented Oct 26, 2011 at 16:38
2
\$\begingroup\$

How about a spark gap? In a gas of known pressure, temperature, and breakdown voltage, the gap can be adjusted to let go at 1kV; feed it with a HV cap. Spark duration would have to be calibrated, but, roughly, limit energy in the cap from 0.1J to 1J \$(1kV\times 1kA\times 0.1\mu s\text{ to }1\mu s = 0.1J\text{ to }1J )\$. My laser theory isn't up to snuff, but I believe input voltage and power don't have to be well regulated, right?

\$\endgroup\$
3
  • \$\begingroup\$ The problem here is that I won't be able to trigger lots of independent 'segmented' electrodes at exactly same time, +-1-2-5ns. \$\endgroup\$ Commented Oct 25, 2011 at 14:44
  • \$\begingroup\$ Isn't this essentially how the thyratron works? "When the control electrode is made slightly positive, gas between the anode and cathode ionizes and conducts current." \$\endgroup\$
    – endolith
    Commented Oct 25, 2011 at 15:05
  • \$\begingroup\$ Looks like thyratrons use the principle of glow discharge, @endolish, though its cousins, the krytron and spytron (1940s), fit this bill. Those timing constraints (±1,2,5ns) remind me of a Q-switch controller I designed in university. Jitter needs to be on that order -- lower than what I'd expect from a spark gap. I guess everything really has already been invented ;) \$\endgroup\$
    – tyblu
    Commented Oct 25, 2011 at 19:30
1
\$\begingroup\$

IGBT's have the voltage, and you would need a number of these to get the current
- shown on graphs up to 150A under pulse conditions.
BUT switching times are about an order of magnitude too high :-(
IXYS IXBX75N17

MOSFETS have the voltage and almost the switchig time but
current rating is very poor at 20A pulse :-(. IXYS again IXTX8N150


Gas discharge tube for turn on triggered with an ionising wrapper coil?

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.