Maybe a spice transient thermal analysis would show the die temperature with that pulsed power, if you are keeping the case at say, 25 C and if you have a thermal RC time constant model for that part. We used to do that years ago and was pretty informative.
boB
At what Vds? And was that beyond the SOA limit? 50msec is a long time, that's usually right before the lowest dotted line in the SOA graph array. If you went much above that line it wouldn't make a whole lot of difference whether you had it on a copper block, in air, or liquid-cooled.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
But the data could be compromised by the fact that some local damage has occurred already. The first time I learned that semiconductors are not digital in terms of *PHUT* was an RF bipolar. A big one that gets bolted on. Being a highschool student I could only afford this one transistor, no spare. Suddenly the collector current ratcheted down, almost like a tectonic shift. So I eased off, tried not to push it as hard. A Motorola RF engineer (the guys that made it) told me that I likely blew out one of the emitter paths. It lived happily ever after, just delivered less RF power than spec.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
I've not personally used an IGBT, but, in a read of their data sheets, I wouldn't operate them in linear mode, they are, after all, a 4-layer device. ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
There were some designed for linear operation. Among many wonderful Toshiba devices was a complementary pair, GT20D101 and GT20D201. They were used in famous Alexander Amplifier. I don't think anybody makes something like this these days. Nobody even makes any P-Channel IGBTs...
-- ****************************************************************** * KSI@home KOI8 Net < > The impossible we do immediately. * * Las Vegas NV, USA < > Miracles require 24-hour notice. * ******************************************************************
See the IGBT as a several microIGBT in paralel. They will be similar but not identical. Diference in transconductance and gate treshold dont affect on switching, but in analogs. Since the most sensible will carry the major current and become an hot spot who will dest5ory te junction. Use in linear mode at 1/4 of rated current or less.
snipped-for-privacy@gmail.com wrote in news: snipped-for-privacy@googlegroups.com:
They attach them all to the same die base so there is no thermal runaway of any one element.
Well, the bigger problem is that transconductance, and therefore power density, is so many times higher than MOSFETs.
As it is, many MOSFETs suffer from 2nd breakdown. RTFDS, find one that behaves.
IGBTs simply aren't intended to be used in linear mode, at all. On the rare occasion that an SOA is provided, they rarely plot durations over 100us, and the SOA is quite narrow by then already. I've never seen a DC SOA on one.
A fixed current derating is meaningless, and misses everything about the problem.
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website:
Right, a small cluster of elements will be in the middle of wherever happens to erupt. Psst...BANG!
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: https://www.seventransistorlabs.com/
Same problem, probably, as using switching mosfets in linear mode; they tend to blow up at fairly low power dissipations. It's the voltage that kills them, not the current; local hot spots get hotter at high voltage, and equalizing resistance helps less.
Presumably there is a SOAR graph that gives some guidance. Otherwise, blow some up.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Hi guys....GREAT THREAD! Thanks. I am into the same thing...IGBT and SiCMOS, 500...900V.
This is the exact issue: Cell paralleling in high current and/or low R semiconductores!
1/4? I am trying to get a GO from a manufacturer....trying to use a SiCMOS in linear mode at 0.1% of rated current: NO approval.@Mark: "IOW, they didn't think it'd work so they didn't try it."
That's exactly it. NO manufacturer actually gives you any data for continuous operation. Even for us, who are one of the bigger customers. We are even doing common development with the biggest manufacturers but regarding linear mode, they just did not test and don´t have the guts to give you ANY hint.
Lately there are too many requests from customers like us who are big players in electromobility (500...800V) so they are just starting to test. But this is still no part of the normal semicondictor certification process. Will change drastically in about two years time!
Meanwhile just think logically and do an accelerated life time test! Then release the parts on your own.
Regards Michael
--------------------------------------- Posted through
So gather some solid data and report back. ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
Thinking outside the box... producing elegant solutions,
by understanding what nature is hiding.
"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie
Many have to do that for milliseconds. An example are ignition coil drivers. If the voltage after opening gets too high there is (at least there is supposed to be) some circuitry that then begins to pull the gate up again and dissipate the energy. That feature is to prevent overvoltage breakdown of the IGBT or the coil in case a spark plug has failed, the distributor has let go or a cable has come off. Or when Gomer Pyle forgot to put it back on.
Why they use IGBT in ignition, beats me. It doesn't make much sense.
?-- Regards, Joerg http://www.analogconsultants.com/
I've seen some driver for ignition IGBTs that also seems have a feature to "abort" an ignition by slowly turning off the IGBT
Same thing, that is the way it's typically done. The primary voltage reaches a certain threshold and the IGBT is held in a linear range until that voltage starts to drop down. Then the conductive path slowly opens.
-- Regards, Joerg http://www.analogconsultants.com/
From what I've gleaned about these things that won't work. This is because even as cells , in thermal equilibrium, each cell does not have the same thermal characteristics except for near saturation or cutoff. The gain has gamma.
So gather some solid data and report back. "
Must be nice to think that is so easy. (I am not being sarcastic) The way I see it first you have to get a bunch of these things, disposable. Then yo u match them well tot heir on and off stats just to be sure of that.
Then comes the fun part, finding he real linear SOA. Since we don't know wh ere to start, if we got 10 amp jobs then start with 50 mA. Keep doubling it until the failures happen. Then we do a couple of more tests with other ba tches of the SAME IGBT. Note their discrepancy level and then test.
I don't want to do it. Go to an electronics school and pay some kid that kn ows something. (hey, that could pay off)
I've got some GREAT IGBT _amplifier_ schematics, along with some seaport property in Yuma to show you >:-}
Doesn't anyone here stop and think, for at least a microsecond, before they plunge into such idiocy? ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
Thinking outside the box... producing elegant solutions,
by understanding what nature is hiding.
"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.