IGBT in Linear Mode
Tim Wescott
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.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
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Jim Thompson
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.
www.irf.com/technical-info/appnotes/an-983.pdf
Since an IGBT is a 4-layer device one would think that "linear mode"
might be like tip-toeing to the edge of a cliff without a safety rope
;-)
...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.
alie...@gmail.com
Web-Site.com> wrote:
> On Tue, 31 May 2011 08:36:46 -0700, Tim Wescott <t...@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.
>
> www.irf.com/technical-info/appnotes/an-983.pdf
>
> Since an IGBT is a 4-layer device one would think that "linear mode"
> might be like tip-toeing to the edge of a cliff without a safety rope
> ;-)
Section 6:
"1. Operation in short circuit. The current in the IGBT is limited
by its gate voltage and transconductance and can reach values well in
excess of 10 times its continuous rating. The level of hole current
that flows underneath the N+ source contact can cause a drop across
r’b, large enough to turn on the NPN parasitic bipolar with possible
latching. This is normally prevented by a reduction in r’b, as
mentioned in the previous section or by a reduction of the total
device transconductance. Since this second technique increases
conduction losses and reduces switching speed, two families of IGBTs
have been made available by IR, one optimized for low conduction
losses, the other for short circuit operation, as indicated in Section
9.
"2. Inductive turn-off, sometimes referred to as "clamped IL." In
an inductive turn-off the voltage swings from a few volts to the
supply voltage with constant current and with no channel current.
These conditions are different from those described in the previous
section in so far as the load current is totally made up of holes
flowing through r’b. For this reason some manufacturers suggest the
use of gate drive resistors to slow down the turn-off dv/dt and
maintain some level of electron current, thereby avoiding a potential
"dynamic latching" condition. IGBTs from International Rectifier can
be operated at their maximum switching speed without any problem.
Reasons to limit the switching speed should be external to the device
(e.g., overshoots due to stray inductance), rather than internal.
"3. Operation as a linear amplifier. Linear operation exercises the
SOA of the IGBT in a combination of the two modes described above. No
detailed characterization of IGBTs as linear amplifiers has been
carried out by IR, given the limited use of IGBTs in this type of
application."
IOW, they didn't think it'd work so they didn't try it.
OTOH:
http://www.st.com/stonline/products/literature/an/3703.pdf
Section 3.2, "Reducing dV/dt at turn-off" et seq has some tricks to
give at least some of that cliff slightly less than infinite slope.
Hey Tim, what's the required BW and signal fidelity? Why fight
IGBTs' inability to do "real" linear operation; could PPM with
averaging in the load work in your app?
Mark L. Fergerson
John Larkin
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.
John
Tim Wescott
I've just begun the dance with the customer, so I'm not sure of the
required bandwidths, etc, although 10kHz is probably sufficient. PPM
wouldn't work in this case (alas) -- it really is something where the
pass device 'wants' to be working in linear mode.
I'm not sure why they're interested in using IGBT -- I'll have to ask
when the occasion comes up.
Tim Wescott
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?
John Larkin
wrote:
>On 05/31/2011 10:58 AM, John Larkin wrote:
>> On Tue, 31 May 2011 08:36:46 -0700, Tim Wescott<t...@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.
Most of the ones we tried exploded at well below 300 watts. Power
mosfets are apparently optimized for switchmode use, and get something
like a second breakdown effect if made to dissipate lots of power at
high voltages.
Ixys makes some parts rated for high-power linear use.
John
k...@att.bizzzzzzzzzzzz
>On 05/31/2011 10:58 AM, John Larkin wrote:
>> On Tue, 31 May 2011 08:36:46 -0700, Tim Wescott<t...@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?
Earlier, AIUI. A secondary breakdown/SOA (localized heating) sort of thing.
Joerg
> On Tue, 31 May 2011 11:06:58 -0700, Tim Wescott <t...@seemywebsite.com>
> wrote:
>
>> On 05/31/2011 10:58 AM, John Larkin wrote:
[...]
>>> 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.
>
> Most of the ones we tried exploded at well below 300 watts. Power
> mosfets are apparently optimized for switchmode use, and get something
> like a second breakdown effect if made to dissipate lots of power at
> high voltages.
>
> Ixys makes some parts rated for high-power linear use.
>
FETs should always be ok when not exceeding the SOA. Did you go outside
of the SOA? 100msec is usually the lowest run or already considered DC.
--
Regards, Joerg
http://www.analogconsultants.com/
"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
John Larkin
wrote:
Since they were rated for 300 watts continuous, we clearly weren't out
of the SOA at less than 300 watts.
I have seen some mosfet SOA curves that included voltage effects. I
recall seeing a fet whose SOA was reduced by about 4:1 at higher
voltages.
For the fets we selected, we wound up estimating a thermal model. In
the amplifier,
ftp://jjlarkin.lmi.net/Amp.jpg
we have a uP that digitizes rail voltages (up to +-200), amp output
voltage, fet currents, and heatsink temperature. It runs a realtime
simulation of junction temperatures and shuts things down at an
estimated 140C Tj. That lets us push the fets pretty hard.
But seriously, switchmode fets get fragile at higher voltages. The
SOAs probably assume they are running close to saturation. [1]
John
[1] I use "saturation" in the bipolar sense, low Vds, ohmic region.
Some people use the word to mean operating fets in the higher voltage,
constant-current region.
Robert Baer
> 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.
>
seem to have a have more than a passing interest, then: DIY.
John Larkin
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.
John
dagmarg...@yahoo.com
My-Web-Site.com> wrote:
> www.irf.com/technical-info/appnotes/an-983.pdf
>
> Since an IGBT is a 4-layer device one would think that "linear mode"
> might be like tip-toeing to the edge of a cliff without a safety rope
> ;-)
Waaayyyy OT, but yes, I've done that, hung my feet over and climbed
down the wall. 5,000 feet vertical.
--
Cheers,
James Arthur
Tim Wescott
> On Tue, 31 May 2011 08:36:46 -0700, Tim Wescott<t...@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.
>
> www.irf.com/technical-info/appnotes/an-983.pdf
>
> Since an IGBT is a 4-layer device one would think that "linear mode"
> might be like tip-toeing to the edge of a cliff without a safety rope
> ;-)
I had a good friend who would dance on the edge of cliffs. I think it
was as much to hear the words "Peter, No!" as for the visceral thrill.
Somehow, I'm not inclined to do that with my customer's money unless
there are clear advantages to success, and the customer's signed up to
what I'm doing.
boB
The specified dissipation figure usually means that you are keeping
the die below its maximum temperature by keeping the case at 25 C.
When pulsing, then the transient thermal behaviour needs to be taken
into account. There's usually a derating curve for that as well.
Spice can model the die temperature for that too if the mfr. gives
you the thermal circuit.
Small die die quicker.
boB
Phil Hobbs
>>> 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.
>
> When pulsing, then the transient thermal behaviour needs to be taken
> into account. There's usually a derating curve for that as well.
> Spice can model the die temperature for that too if the mfr. gives
> you the thermal circuit.
>
> Small die die quicker.
>
> boB
>
because the heat is flowing into surroundings that are cooler than they
would be in steady-state.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
email: hobbs (atsign) electrooptical (period) net
http://electrooptical.net
John Larkin
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.
John
Jon Elson
> 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.
>
At least when I worked with them, it was STRONGLY discouraged. The
problem was that while FETs have negative thermal coefficient, so the
current tends to share over the area of the transistor, the IGBT has a
positive coefficient, so current tends to "hog" to the hottest area of
the transistor, leading to rapid damage. The only way to fight this is
to saturate the transistor quickly and hard.
Jon
Joerg
300W is most likely a marketing spec. But no matter what, a power rating
has nothing to do with SOA.
A FET can be perfectly ok at 3V/100A (300W) but explode with gusto at
50V/20A (100W). The SOA diagram will tell you. Like this one in the link
Lasse brought:
http://ixdev.ixys.com/DataSheet/DS100239%28IXTK-TX200N10L2%29.pdf
> I have seen some mosfet SOA curves that included voltage effects. I
> recall seeing a fet whose SOA was reduced by about 4:1 at higher
> voltages.
>
They all drop off in the SOA at higher voltage.
> For the fets we selected, we wound up estimating a thermal model. In
> the amplifier,
>
> ftp://jjlarkin.lmi.net/Amp.jpg
>
Nice blue theme color there :-)
> we have a uP that digitizes rail voltages (up to +-200), amp output
> voltage, fet currents, and heatsink temperature. It runs a realtime
> simulation of junction temperatures and shuts things down at an
> estimated 140C Tj. That lets us push the fets pretty hard.
>
> But seriously, switchmode fets get fragile at higher voltages. The
> SOAs probably assume they are running close to saturation. [1]
>
> John
>
> [1] I use "saturation" in the bipolar sense, low Vds, ohmic region.
> Some people use the word to mean operating fets in the higher voltage,
> constant-current region.
>
It's all spelled out in the SOA curves. Don't push you luck there or
it'll go ... tssk ... *PHOOMP*
Thing is, if you are just a wee bit into forbidden SOA turf it may all
work fine for many months until one of the FETs really gets sick of it.
Jim Thompson
wrote:
I haven't needed to do it in quite a while, but you CAN hook a
behavioral device into your simulation to automatically plot SOA
curves. I've even been known to have it also plot the spec as well
boB
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:
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
Joerg
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.
Joerg
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.
Jim Thompson
wrote:
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.
Sergey Kubushyn
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...
---
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* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************
alfredogab...@gmail.com
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.
DecadentLinux...@decadence.org
news:1bab319f-de35-4801...@googlegroups.com:
> Since the most sensible will carry the major current and become an hot
> spot who will dest5ory te junction.
any one element.
Tim Williams
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/
<alfredogab...@gmail.com> wrote in message
news:1bab319f-de35-4801...@googlegroups.com...
Tim Williams
news:paiuu1$1m0u$2...@gioia.aioe.org...
to erupt. Psst...BANG!
John Larkin
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
mexman
I am into the same thing...IGBT and SiCMOS, 500...900V.
>>See the IGBT as a several microIGBT in paralel.
semiconductores!
>>Use in linear mode at 1/4 of rated current or less.
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
---------------------------------------
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Jim Thompson
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
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
Joerg
> 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.
>
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.
https://vignette.wikia.nocookie.net/mayberry/images/5/57/GillyandGoober.png/revision/latest?cb=20110730152008
Why they use IGBT in ignition, beats me. It doesn't make much sense.
> A fixed current derating is meaningless, and misses everything about the
> problem.
>
Lasse Langwadt Christensen
> On 2018-04-10 13:52, Tim Williams wrote:
> > 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.
> >
>
> 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.
>
Joerg
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.
jurb...@gmail.com
jurb...@gmail.com
>Michael
>
So gather some solid data and report back. "
Then comes the fun part, finding he real linear SOA. Since we don't know where 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 batches 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 knows something. (hey, that could pay off)
Jim Thompson
<129087@Electronics-Related> wrote:
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?