On Wed, 01 Jun 2011 08:10:46 -0700, John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:>On 1 Jun 2011 02:40:01 -0500, boB wrote: > >>On Tue, 31 May 2011 15:37:58 -0700, John Larkin >><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >> >>>On Tue, 31 May 2011 11:06:58 -0700, Tim Wescott <tim@seemywebsite.com> >>>wrote: >>> >>>>On 05/31/2011 10:58 AM, John Larkin wrote: >>>>> On Tue, 31 May 2011 08:36:46 -0700, Tim Wescott<tim@seemywebsite.com> >>>>> wrote: >>>>> >>>>>> Any good articles in using IGBTs in linear mode? >>>>>> >>>>>> With all due respect for the uselessness of SPICE when you can't do the >>>>>> work on paper -- does anyone know how good a SPICE model designed for an >>>>>> IGBT in switched service might work in linear mode? Who tends to have >>>>>> better models for linear service? Whether anyone has models >>>>>> specifically for IGBTs in linear mode? >>>>>> >>>>>> TIA -- IGBTs seem to be enough of a corner case in the semiconductor >>>>>> world that it's hard to find definitive data about their operation >>>>>> beyond a cross-section of a generic chip, and some hand-waving arguments >>>>>> about how it works just like a MOSFET/BJT Darlington-ish pair. >>>>> >>>>> Don't know about IGBTs, but lots of high-power-rated mosfets will blow >>>>> up at relatively low power dissipations in linear mode. We had to test >>>>> a lot of them. >>>>> >>>>> ftp://66.117.156.8/ExFets.jpg >>>> >>>>The risk is undoubtedly there for IGBTs, as well. They're designed for >>>>high voltage * low current, or high current * low voltage, not middle^2. >>>> >>>>Were they blowing up at the expected power dissipation, or do they tend >>>>to blow up earlier than their maximum junction temperature & thermal >>>>conductivity would indicate? >>> >>>We tested a bunch of mosfets rated for 300 watts continuous >>>dissipation. They were bolted to a copper block, and pulsed at various >>>power dissipations for 0.1 seconds at very low duty cycle. The >>>application is small-bore MRI gradient drivers. I think we tested them >>>at 200 volts D-S, can't recall exactly. >> >> >>The specified dissipation figure usually means that you are keeping >>the die below its maximum temperature by keeping the case at 25 C. > >Sure. A copper block does that pretty well, for a tenth of a second. > >But the point I was making is that most power mosfets are designed to >work in switchmode, and can blow up at way under rated power >dissipation when used in linear applications, namely dissipating power >with higher Vds. > >We were blowing up "300 watt" mosfets at 150 watts, in 50 >milliseconds, bolted to a copper block. >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> >John
IGBT in Linear Mode
Started by ●May 31, 2011
Reply by ●June 2, 20112011-06-02
Reply by ●June 4, 20112011-06-04
John Larkin wrote:> On 1 Jun 2011 02:40:01 -0500, boB wrote: > >> On Tue, 31 May 2011 15:37:58 -0700, John Larkin >> <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >> >>> On Tue, 31 May 2011 11:06:58 -0700, Tim Wescott <tim@seemywebsite.com> >>> wrote: >>> >>>> On 05/31/2011 10:58 AM, John Larkin wrote: >>>>> On Tue, 31 May 2011 08:36:46 -0700, Tim Wescott<tim@seemywebsite.com> >>>>> wrote: >>>>> >>>>>> Any good articles in using IGBTs in linear mode? >>>>>> >>>>>> With all due respect for the uselessness of SPICE when you can't do the >>>>>> work on paper -- does anyone know how good a SPICE model designed for an >>>>>> IGBT in switched service might work in linear mode? Who tends to have >>>>>> better models for linear service? Whether anyone has models >>>>>> specifically for IGBTs in linear mode? >>>>>> >>>>>> TIA -- IGBTs seem to be enough of a corner case in the semiconductor >>>>>> world that it's hard to find definitive data about their operation >>>>>> beyond a cross-section of a generic chip, and some hand-waving arguments >>>>>> about how it works just like a MOSFET/BJT Darlington-ish pair. >>>>> Don't know about IGBTs, but lots of high-power-rated mosfets will blow >>>>> up at relatively low power dissipations in linear mode. We had to test >>>>> a lot of them. >>>>> >>>>> ftp://66.117.156.8/ExFets.jpg >>>> The risk is undoubtedly there for IGBTs, as well. They're designed for >>>> high voltage * low current, or high current * low voltage, not middle^2. >>>> >>>> Were they blowing up at the expected power dissipation, or do they tend >>>> to blow up earlier than their maximum junction temperature & thermal >>>> conductivity would indicate? >>> We tested a bunch of mosfets rated for 300 watts continuous >>> dissipation. They were bolted to a copper block, and pulsed at various >>> power dissipations for 0.1 seconds at very low duty cycle. The >>> application is small-bore MRI gradient drivers. I think we tested them >>> at 200 volts D-S, can't recall exactly. >> >> The specified dissipation figure usually means that you are keeping >> the die below its maximum temperature by keeping the case at 25 C. > > Sure. A copper block does that pretty well, for a tenth of a second. > > But the point I was making is that most power mosfets are designed to > work in switchmode, and can blow up at way under rated power > dissipation when used in linear applications, namely dissipating power > with higher Vds. > > We were blowing up "300 watt" mosfets at 150 watts, in 50 > milliseconds, bolted to a copper block. >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.
Reply by ●June 4, 20112011-06-04
John Larkin wrote:> On Tue, 31 May 2011 20:38:48 -0700, Robert Baer > <robertbaer@localnet.com> wrote: > >> Tim Wescott wrote: >>> Any good articles in using IGBTs in linear mode? >>> >>> With all due respect for the uselessness of SPICE when you can't do the >>> work on paper -- does anyone know how good a SPICE model designed for an >>> IGBT in switched service might work in linear mode? Who tends to have >>> better models for linear service? Whether anyone has models >>> specifically for IGBTs in linear mode? >>> >>> TIA -- IGBTs seem to be enough of a corner case in the semiconductor >>> world that it's hard to find definitive data about their operation >>> beyond a cross-section of a generic chip, and some hand-waving arguments >>> about how it works just like a MOSFET/BJT Darlington-ish pair. >>> >> Well,since there is an abundant lack of that information, and you >> seem to have a have more than a passing interest, then: DIY. > > Testing semiconductors to destruction is tedious and expensive. > Especially so for big semiconductors. > > I was doing that on some Claire mosfet SSRs and discovered that I > could tease them to just-before-destruction, by looking at > accelerating drain current, probably the thermal precursor to some > second breakdown sort of thing. Once I got that sort of calibrated, I > could take a lot of data without incinerating a lot of chips. >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.
Reply by ●June 4, 20112011-06-04
On Sat, 04 Jun 2011 13:07:48 -0700, Joerg <invalid@invalid.invalid> wrote:>John Larkin wrote: >> On Tue, 31 May 2011 20:38:48 -0700, Robert Baer >> <robertbaer@localnet.com> wrote: >> >>> Tim Wescott wrote: >>>> Any good articles in using IGBTs in linear mode? >>>> >>>> With all due respect for the uselessness of SPICE when you can't do the >>>> work on paper -- does anyone know how good a SPICE model designed for an >>>> IGBT in switched service might work in linear mode? Who tends to have >>>> better models for linear service? Whether anyone has models >>>> specifically for IGBTs in linear mode? >>>> >>>> TIA -- IGBTs seem to be enough of a corner case in the semiconductor >>>> world that it's hard to find definitive data about their operation >>>> beyond a cross-section of a generic chip, and some hand-waving arguments >>>> about how it works just like a MOSFET/BJT Darlington-ish pair. >>>> >>> Well,since there is an abundant lack of that information, and you >>> seem to have a have more than a passing interest, then: DIY. >> >> Testing semiconductors to destruction is tedious and expensive. >> Especially so for big semiconductors. >> >> I was doing that on some Claire mosfet SSRs and discovered that I >> could tease them to just-before-destruction, by looking at >> accelerating drain current, probably the thermal precursor to some >> second breakdown sort of thing. Once I got that sort of calibrated, I >> could take a lot of data without incinerating a lot of chips. >> > >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.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.
Reply by ●June 4, 20112011-06-04
Jim Thompson <To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote:> On Sat, 04 Jun 2011 13:07:48 -0700, Joerg <invalid@invalid.invalid> > wrote: > >>John Larkin wrote: >>> On Tue, 31 May 2011 20:38:48 -0700, Robert Baer >>> <robertbaer@localnet.com> wrote: >>> >>>> Tim Wescott wrote: >>>>> Any good articles in using IGBTs in linear mode? >>>>> >>>>> With all due respect for the uselessness of SPICE when you can't do the >>>>> work on paper -- does anyone know how good a SPICE model designed for an >>>>> IGBT in switched service might work in linear mode? Who tends to have >>>>> better models for linear service? Whether anyone has models >>>>> specifically for IGBTs in linear mode? >>>>> >>>>> TIA -- IGBTs seem to be enough of a corner case in the semiconductor >>>>> world that it's hard to find definitive data about their operation >>>>> beyond a cross-section of a generic chip, and some hand-waving arguments >>>>> about how it works just like a MOSFET/BJT Darlington-ish pair. >>>>> >>>> Well,since there is an abundant lack of that information, and you >>>> seem to have a have more than a passing interest, then: DIY. >>> >>> Testing semiconductors to destruction is tedious and expensive. >>> Especially so for big semiconductors. >>> >>> I was doing that on some Claire mosfet SSRs and discovered that I >>> could tease them to just-before-destruction, by looking at >>> accelerating drain current, probably the thermal precursor to some >>> second breakdown sort of thing. Once I got that sort of calibrated, I >>> could take a lot of data without incinerating a lot of chips. >>> >> >>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. > > 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.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. * ******************************************************************
Reply by ●April 10, 20182018-04-10
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.
Reply by ●April 10, 20182018-04-10
alfredogabrielmendez@gmail.com wrote in news:1bab319f-de35-4801-abed-12010777f151@googlegroups.com:> Since the most sensible will carry the major current and become an hot > spot who will dest5ory te junction.They attach them all to the same die base so there is no thermal runaway of any one element.
Reply by ●April 10, 20182018-04-10
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: https://www.seventransistorlabs.com/ <alfredogabrielmendez@gmail.com> wrote in message news:1bab319f-de35-4801-abed-12010777f151@googlegroups.com...> 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.
Reply by ●April 10, 20182018-04-10
<DecadentLinuxUserNumeroUno@decadence.org> wrote in message news:paiuu1$1m0u$2@gioia.aioe.org...> alfredogabrielmendez@gmail.com wrote in > news:1bab319f-de35-4801-abed-12010777f151@googlegroups.com: > >> Since the most sensible will carry the major current and become an hot >> spot who will dest5ory te junction. > > They attach them all to the same die base so there is no thermal runaway > of > any one element.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/
Reply by ●April 10, 20182018-04-10
On Tue, 10 Apr 2018 11:08:01 -0700 (PDT), alfredogabrielmendez@gmail.com wrote:>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.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. https://www.dropbox.com/s/4x34e1kisggy4de/ExFets.jpg?raw=1 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
