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Triac vs MOSFETs for AC switching
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panfilero
Apr 22, 2014, 5:45:59 PM4/22/14
to
I'm designing a switch (basically a SSR) for AC 110V, 60Hz. Does anyone know if it's better to go with a pair of FETs or with a Triac? My design has to be able to withstand a short circuit current of 200A for a few msec, but normally it's running around 0-8A. I like that the FETs can open up real quick, I have to wait for zero-crossing to open my Triac.
thanks!
thanks!
haitic...@gmail.com
Apr 22, 2014, 6:02:46 PM4/22/14
to
On Tuesday, April 22, 2014 5:45:59 PM UTC-4, panfilero wrote:
> I'm designing a switch (basically a SSR) for AC 110V, 60Hz. Does anyone know if it's better to go with a pair of FETs or with a Triac? My design has to be able to withstand a short circuit current of 200A for a few msec, but normally it's running around 0-8A. I like that the FETs can open up real quick, I have to wait for zero-crossing to open my Triac.
>
>
>
> thanks!
I use those triac "bricks" you can buy on ebay for $4. You could put a 75w
> I'm designing a switch (basically a SSR) for AC 110V, 60Hz. Does anyone know if it's better to go with a pair of FETs or with a Triac? My design has to be able to withstand a short circuit current of 200A for a few msec, but normally it's running around 0-8A. I like that the FETs can open up real quick, I have to wait for zero-crossing to open my Triac.
>
>
>
> thanks!
light bulb in series with your load.
"Crude, but effective" - Old Chinese proverb
Maynard A. Philbrook Jr.
Apr 22, 2014, 6:36:09 PM4/22/14
to
In article <0b567f18-65a7-48a2...@googlegroups.com>,
panf...@gmail.com says...
don't you think?
Jamie..
panf...@gmail.com says...
>
> I'm designing a switch (basically a SSR) for AC 110V, 60Hz. Does anyone know if it's better to go with a pair of FETs or with a Triac? My design has to be able to withstand a short circuit current of 200A for a few msec, but normally it's running around 0-8A. I like that the FETs can open up real quick, I have to wait for zero-crossing to open my Triac.
>
> thanks!
They have GTO's, besides, I think it's a good idea to wait for zero,
> I'm designing a switch (basically a SSR) for AC 110V, 60Hz. Does anyone know if it's better to go with a pair of FETs or with a Triac? My design has to be able to withstand a short circuit current of 200A for a few msec, but normally it's running around 0-8A. I like that the FETs can open up real quick, I have to wait for zero-crossing to open my Triac.
>
> thanks!
don't you think?
Jamie..
panfilero
Apr 22, 2014, 7:56:49 PM4/22/14
to
On Tuesday, April 22, 2014 5:36:09 PM UTC-5, Maynard A. Philbrook Jr. wrote:
> In article <0b567f18-65a7-48a2...@googlegroups.com>,
> In article <0b567f18-65a7-48a2...@googlegroups.com>,
>
>
>
> >
>
> > I'm designing a switch (basically a SSR) for AC 110V, 60Hz. Does anyone know if it's better to go with a pair of FETs or with a Triac? My design has to be able to withstand a short circuit current of 200A for a few msec, but normally it's running around 0-8A. I like that the FETs can open up real quick, I have to wait for zero-crossing to open my Triac.
>
> >
>
> > thanks!
>
>
>
> They have GTO's, besides, I think it's a good idea to wait for zero,
>
> don't you think?
>
>
>
> Jamie..
What's a GTO? I like waiting for zero to close the switch, but if I see large current from a short circuit, I would like to open up really fast, and not wait milliseconds for the zero cross, I like that a FET can open quickly in response to something like that
>
>
> >
>
> > I'm designing a switch (basically a SSR) for AC 110V, 60Hz. Does anyone know if it's better to go with a pair of FETs or with a Triac? My design has to be able to withstand a short circuit current of 200A for a few msec, but normally it's running around 0-8A. I like that the FETs can open up real quick, I have to wait for zero-crossing to open my Triac.
>
> >
>
> > thanks!
>
>
>
> They have GTO's, besides, I think it's a good idea to wait for zero,
>
> don't you think?
>
>
>
> Jamie..
Martin Riddle
Apr 22, 2014, 9:32:08 PM4/22/14
to
> 1KA GTO's for industry. BTW, it's big business. See DYNEX.
If you want to turn off a SCR, you can try forced communitation,
basically reversing anode and cathode voltages via a large
capacitor.
Cheers
josephkk
Apr 23, 2014, 12:32:44 AM4/23/14
to
On Tue, 22 Apr 2014 14:45:59 -0700 (PDT), panfilero <panf...@gmail.com>
wrote:
>I'm designing a switch (basically a SSR) for AC 110V, 60Hz. Does anyone know if it's better to go with a pair of FETs or with a Triac? My design has to be able to withstand a short circuit current of 200A for a few msec, but normally it's running around 0-8A. I like that the FETs can open up real quick, I have to wait for zero-crossing to open my Triac.
>
>thanks!
Well the thing is that SCRs and triacs CAN be commutated. It is just a
bit complex for SCRs and a lot complex for triacs. That said, a lot more
depends on whether or not you can control the application space of your
switch. If you cannot, triacs have a big overcurrent durability
advantage.
?-)
wrote:
>I'm designing a switch (basically a SSR) for AC 110V, 60Hz. Does anyone know if it's better to go with a pair of FETs or with a Triac? My design has to be able to withstand a short circuit current of 200A for a few msec, but normally it's running around 0-8A. I like that the FETs can open up real quick, I have to wait for zero-crossing to open my Triac.
>
>thanks!
bit complex for SCRs and a lot complex for triacs. That said, a lot more
depends on whether or not you can control the application space of your
switch. If you cannot, triacs have a big overcurrent durability
advantage.
?-)
josephkk
Apr 23, 2014, 12:39:25 AM4/23/14
to
On Tue, 22 Apr 2014 16:56:49 -0700 (PDT), panfilero <panf...@gmail.com>
wrote:
A Gate Turn Off thyristor (SCR).
?-)
wrote:
?-)
mrob...@att.net
Apr 23, 2014, 12:11:35 AM4/23/14
to
panfilero <panf...@gmail.com> wrote:
> I'm designing a switch (basically a SSR) for AC 110V, 60Hz. Does
> anyone know if it's better to go with a pair of FETs or with a Triac?
> My design has to be able to withstand a short circuit current of 200A
> for a few msec, but normally it's running around 0-8A.
Just looking at a couple of SSRs that can switch at least 8 A on Digi-
> I'm designing a switch (basically a SSR) for AC 110V, 60Hz. Does
> anyone know if it's better to go with a pair of FETs or with a Triac?
> My design has to be able to withstand a short circuit current of 200A
> for a few msec, but normally it's running around 0-8A.
Key, the single-cycle surge current rating seems to be around 10 times
the steady-state current rating. And if you *do* blow one up, it's a
few minutes with a screwdriver to change it out.
They do have a maximum turn-off time of 8.3 millisec for DC control
voltage. The turn-off time is longer (20 or 30 millisec) for AC
control voltage; I guess maybe they have a small capacitor in there or
something.
As a specific example, Panasonic AQA411VL or AQA421VL have ratings of
25 A nominal and 250 A "non-repetitive surge". $35/1, $24/100.
Standard disclaimers apply: I don't get money or other consideration
from any companies mentioned.
Matt Roberds
dalai lamah
Apr 23, 2014, 1:19:13 PM4/23/14
to
Un bel giorno panfilero digitò:
> I'm designing a switch (basically a SSR) for AC 110V, 60Hz. Does anyone
> know if it's better to go with a pair of FETs or with a Triac?
I've made a quick comparison just the other day and I've concluded that
TRIACs are still better for higher voltages applications, at least in terms
of power dissipation and robustness. But in my case I needed >200V, maybe
in the 100...150V range there is something better.
> My design
> has to be able to withstand a short circuit current of 200A for a few
> msec, but normally it's running around 0-8A. I like that the FETs can
> open up real quick, I have to wait for zero-crossing to open my Triac.
A fundamental parameter reported in every TRIAC datasheet is the I2t
rating, so it's pretty straightforward to choose the right fuse to protect
them.
--
Fletto i muscoli e sono nel vuoto.
> I'm designing a switch (basically a SSR) for AC 110V, 60Hz. Does anyone
> know if it's better to go with a pair of FETs or with a Triac?
TRIACs are still better for higher voltages applications, at least in terms
of power dissipation and robustness. But in my case I needed >200V, maybe
in the 100...150V range there is something better.
> My design
> has to be able to withstand a short circuit current of 200A for a few
> msec, but normally it's running around 0-8A. I like that the FETs can
> open up real quick, I have to wait for zero-crossing to open my Triac.
rating, so it's pretty straightforward to choose the right fuse to protect
them.
--
Fletto i muscoli e sono nel vuoto.
jurb...@gmail.com
Apr 23, 2014, 3:33:29 PM4/23/14
to
The only possible reason I could think of for using FETs rather than one of the wonderful thrysistor type devices out there is if it is an extremely complex, like partly highly inducive, load. Or maybe extremely non-linear to the point where you can't count on zero crossing so much.
Something like that. Even then there are ways to deal with it, it just becomes a matter of what is easier.
Something like that. Even then there are ways to deal with it, it just becomes a matter of what is easier.
Lasse Langwadt Christensen
Apr 23, 2014, 5:53:30 PM4/23/14
to
Den onsdag den 23. april 2014 21.33.29 UTC+2 skrev jurb...@gmail.com:
> The only possible reason I could think of for using FETs rather than one of the wonderful thrysistor type devices out there is if it is an extremely complex, like partly highly inducive, load. Or maybe extremely non-linear to the point where you can't count on zero crossing so much.
>
>
>
> Something like that. Even then there are ways to deal with it, it just becomes a matter of what is easier.
the advantage of a fet is that you can turn it off "instantly"
> The only possible reason I could think of for using FETs rather than one of the wonderful thrysistor type devices out there is if it is an extremely complex, like partly highly inducive, load. Or maybe extremely non-linear to the point where you can't count on zero crossing so much.
>
>
>
> Something like that. Even then there are ways to deal with it, it just becomes a matter of what is easier.
so you can make it pretty much short-circuit prof
with a triac you have to handle a whole cycle
-Lasse
Maynard A. Philbrook Jr.
Apr 23, 2014, 7:05:01 PM4/23/14
to
In article <3423ac08-c9df-4ff3...@googlegroups.com>,
panf...@gmail.com says...
That is a gate turn off thyristor..
A note, when working with thyristor switches care must be taken
driving highly inductive loads. The thyristor will likely not turn off
at the line source when it reaches 0 but up to another 90 degrees after
that. This should be fine since by the time the current near's 0 through
the thyristor, you only get the remaining hold current of the thyristor
to worry about in the collapse.
Jamie
panf...@gmail.com says...
A note, when working with thyristor switches care must be taken
driving highly inductive loads. The thyristor will likely not turn off
at the line source when it reaches 0 but up to another 90 degrees after
that. This should be fine since by the time the current near's 0 through
the thyristor, you only get the remaining hold current of the thyristor
to worry about in the collapse.
Jamie
boB
Apr 23, 2014, 7:08:55 PM4/23/14
to
crossing and so tend not to have much problem with inductive flyback
spikes. Kinda takes care of itself.
But the nice thing about FETs is their low voltage drop where you're
stuck with drop and dissipation with SCRs and triacs.
For AC control, I tend to use thyristors and also already built SSRs
with triacs in them. For the high surge currents, I just use larger
SSRs or over-design the thing.
SSRs or MOCxxx drivers and discreet SCRs/triacs can also
syncronously turn ON at zero crossing which can help in some
situations, like reduced EMI.
boB
whit3rd
Apr 23, 2014, 7:38:17 PM4/23/14
to
On Tuesday, April 22, 2014 2:45:59 PM UTC-7, panfilero wrote:
> I'm designing a switch (basically a SSR) for AC 110V, 60Hz. Does anyone know if it's better to go with a pair of FETs or with a Triac?
A pair of power FETs have a pair of source-drain diodes built-in.
> I'm designing a switch (basically a SSR) for AC 110V, 60Hz. Does anyone know if it's better to go with a pair of FETs or with a Triac?
I think that solution is very complicated.
Lasse Langwadt Christensen
Apr 23, 2014, 7:58:32 PM4/23/14
to
~
|
|
||-+
||<+
(+)----+---||-+
| |
(-)----|------+
| |
+---||-+
||<+
||-+
|
|
~
-Lasse
Mike Perkins
Apr 23, 2014, 10:42:47 PM4/23/14
to
--
Mike Perkins
Video Solutions Ltd
www.videosolutions.ltd.uk
panfilero
Apr 23, 2014, 11:38:51 PM4/23/14
to
panfilero
Apr 23, 2014, 11:40:20 PM4/23/14
to
whit3rd
Apr 24, 2014, 2:40:02 AM4/24/14
to
Or, use a fullwave bridge around a single MOSFET
(losing some efficiency). Any old relay would be easier and
more efficient.
Lasse Langwadt Christensen
Apr 24, 2014, 7:35:01 AM4/24/14
to
Den torsdag den 24. april 2014 08.40.02 UTC+2 skrev whit3rd:
> On Wednesday, April 23, 2014 4:58:32 PM UTC-7, Lasse Langwadt Christensen wrote:
>
> > Den torsdag den 24. april 2014 01.38.17 UTC+2 skrev whit3rd:
>
> >
>
> > > On Tuesday, April 22, 2014 2:45:59 PM UTC-7, panfilero wrote:
>
> >
>
> > >
>
> >
>
> > > > I'm designing a switch (basically a SSR) for AC 110V, 60Hz. Does anyone know if it's better to go with a pair of FETs or with a Triac?
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > > A pair of power FETs have a pair of source-drain diodes built-in.
>
> >
>
> > >
>
> >
>
> > > I think that solution is very complicated.
>
> >
>
> >
>
> >
>
> > not really, FETs source to source, you'll need a isolated supply to drive the gates
>
> >
>
> >
>
> >
>
> >
>
> >
>
> > ~
>
> >
>
> > |
>
> >
>
> > |
>
> >
>
> > ||-+
>
> >
>
> > ||<+
>
> >
>
> > (+)----+---||-+
>
> >
>
> > | |
>
> >
>
> > (-)----|------+
>
> >
>
> > | |
>
> >
>
> > +---||-+
>
> >
>
> > ||<+
>
> >
>
> > ||-+
>
> >
>
> > |
>
> >
>
> > |
>
> >
>
> > ~
>
>
>
> Shouldn't one of those be a PMOS?
>
nope, two NMOS
> On Wednesday, April 23, 2014 4:58:32 PM UTC-7, Lasse Langwadt Christensen wrote:
>
> > Den torsdag den 24. april 2014 01.38.17 UTC+2 skrev whit3rd:
>
> >
>
> > > On Tuesday, April 22, 2014 2:45:59 PM UTC-7, panfilero wrote:
>
> >
>
> > >
>
> >
>
> > > > I'm designing a switch (basically a SSR) for AC 110V, 60Hz. Does anyone know if it's better to go with a pair of FETs or with a Triac?
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > > A pair of power FETs have a pair of source-drain diodes built-in.
>
> >
>
> > >
>
> >
>
> > > I think that solution is very complicated.
>
> >
>
> >
>
> >
>
> > not really, FETs source to source, you'll need a isolated supply to drive the gates
>
> >
>
> >
>
> >
>
> >
>
> >
>
> > ~
>
> >
>
> > |
>
> >
>
> > |
>
> >
>
> > ||-+
>
> >
>
> > ||<+
>
> >
>
> > (+)----+---||-+
>
> >
>
> > | |
>
> >
>
> > (-)----|------+
>
> >
>
> > | |
>
> >
>
> > +---||-+
>
> >
>
> > ||<+
>
> >
>
> > ||-+
>
> >
>
> > |
>
> >
>
> > |
>
> >
>
> > ~
>
>
>
> Shouldn't one of those be a PMOS?
>
>
>
> Or, use a fullwave bridge around a single MOSFET
>
> (losing some efficiency). Any old relay would be easier and
>
> more efficient.
toggle it at a few Hertz
-Lasse
Spehro Pefhany
Apr 24, 2014, 4:32:25 PM4/24/14
to
On Thu, 24 Apr 2014 03:42:47 +0100, Mike Perkins <sp...@spam.com>
wrote:
>On 22/04/2014 22:45, panfilero wrote:
>> I'm designing a switch (basically a SSR) for AC 110V, 60Hz. Does
>> anyone know if it's better to go with a pair of FETs or with a Triac?
>> My design has to be able to withstand a short circuit current of 200A
>> for a few msec, but normally it's running around 0-8A. I like that
>> the FETs can open up real quick, I have to wait for zero-crossing to
>> open my Triac.
>>
>> thanks!
>
>Have you looked at IGBTs? They are quite cheap and can be turned off PDQ.
You don't want them to turn off too too fast in a short-circuit
condition- that can ruin the part too.
wrote:
>On 22/04/2014 22:45, panfilero wrote:
>> I'm designing a switch (basically a SSR) for AC 110V, 60Hz. Does
>> anyone know if it's better to go with a pair of FETs or with a Triac?
>> My design has to be able to withstand a short circuit current of 200A
>> for a few msec, but normally it's running around 0-8A. I like that
>> the FETs can open up real quick, I have to wait for zero-crossing to
>> open my Triac.
>>
>> thanks!
>
>Have you looked at IGBTs? They are quite cheap and can be turned off PDQ.
condition- that can ruin the part too.
Robert Baer
Apr 25, 2014, 3:09:34 AM4/25/14
to
panfilero wrote:
> I'm designing a switch (basically a SSR) for AC 110V, 60Hz. Does anyone know if it's better to go with a pair of FETs or with a Triac? My design has to be able to withstand a short circuit current of 200A for a few msec, but normally it's running around 0-8A. I like that the FETs can open up real quick, I have to wait for zero-crossing to open my Triac.
>
> thanks!
...and 200A can melt silicon to a nice short.
> I'm designing a switch (basically a SSR) for AC 110V, 60Hz. Does anyone know if it's better to go with a pair of FETs or with a Triac? My design has to be able to withstand a short circuit current of 200A for a few msec, but normally it's running around 0-8A. I like that the FETs can open up real quick, I have to wait for zero-crossing to open my Triac.
>
> thanks!
Mike Perkins
Apr 25, 2014, 7:05:40 AM4/25/14
to
device for a specified length of time.
With a short circuit load and a subsequent high di/dt I can't imagine
there being any effective method of turning off one of these devices
through commutation!
haitic...@gmail.com
Apr 25, 2014, 8:38:08 AM4/25/14
to
On Tuesday, April 22, 2014 5:45:59 PM UTC-4, panfilero wrote:
> I'm designing a switch (basically a SSR) for AC 110V, 60Hz. Does anyone know if it's better to go with a pair of FETs or with a Triac? My design has to be able to withstand a short circuit current of 200A for a few msec, but normally it's running around 0-8A. I like that the FETs can open up real quick, I have to wait for zero-crossing to open my Triac.
>
>
>
> thanks!
Use a socket to plug the triac into. Supply extra triacs. Then, when the triac
>
>
>
> thanks!
blows, plug another in.
Advertise this as a breakthrough - the fast response solid state fuse.
a feature.
Mike Perkins
Apr 25, 2014, 1:35:39 PM4/25/14
to
small IGBT.
I'm only aware of di/dt limitations for TRIACs and Thyristers but not
for IGBT.
I've looked up a couple of IGBTs and as an example STGP8NC60 cites a
di/dt turn-on as a feature rather than a limitation. It's description
says "short circuit withstand time 10us" and has a helpful Turn-off SOA
graph to suggest it can handle 300A at 400V at turn off.
http://www.st.com/web/en/resource/technical/document/datasheet/CD00171973.pdf
in DigKey for not very much!
Spehro Pefhany
Apr 25, 2014, 2:02:02 PM4/25/14
to
On Fri, 25 Apr 2014 18:35:39 +0100, the renowned Mike Perkins
Here's a bit on it (soft shut down):
http://www.irf.com/technical-info/whitepaper/apec11igbt.pdf
AFAIUI, the problem is more what happens to the energy in the external
inductance than di/dt on the device itself.
Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
sp...@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
http://www.irf.com/technical-info/whitepaper/apec11igbt.pdf
AFAIUI, the problem is more what happens to the energy in the external
inductance than di/dt on the device itself.
Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
sp...@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
Mike Perkins
Apr 25, 2014, 3:42:15 PM4/25/14
to
by a fast di/dt alone, but from other circuit consideration such as from
a turn off HV spike.
Whereas a SCR or TRIAC will themselves have a overriding di/dt
specification without any further circuit considerations complicating
the issue.
Tim Williams
Apr 25, 2014, 5:48:14 PM4/25/14
to
"Mike Perkins" <sp...@spam.com> wrote in message
news:1KqdnUMxCooIJ8fO...@bt.com...
forward-biasing the parasitic BJT structure (same idea as thyristor dV/dt,
but much less sensitive).
I don't think I've ever heard it explained why that's a bad thing --
surely it just manifests as excessive Miller effect at high rates.
Presumably, the minority carriers also stick around for a while, with an
effect similar to body diode recovery (taking on the order of ~200ns in
power devices), which will cause excess dissipation, but not outright
destruction. Dunno.
Thyristor dI/dt, of course, is bad because of hot spots, and dV/dt because
of re-latching.
Tim
--
Seven Transistor Labs
Electrical Engineering Consultation
Website: http://seventransistorlabs.com
news:1KqdnUMxCooIJ8fO...@bt.com...
> Whereas a SCR or TRIAC will themselves have a overriding di/dt
> specification without any further circuit considerations complicating
> the issue.
Yeah, AFAIK it's just dV/dt for FET structures. Something about
> specification without any further circuit considerations complicating
> the issue.
forward-biasing the parasitic BJT structure (same idea as thyristor dV/dt,
but much less sensitive).
I don't think I've ever heard it explained why that's a bad thing --
surely it just manifests as excessive Miller effect at high rates.
Presumably, the minority carriers also stick around for a while, with an
effect similar to body diode recovery (taking on the order of ~200ns in
power devices), which will cause excess dissipation, but not outright
destruction. Dunno.
Thyristor dI/dt, of course, is bad because of hot spots, and dV/dt because
of re-latching.
Tim
--
Seven Transistor Labs
Electrical Engineering Consultation
Website: http://seventransistorlabs.com
josephkk
Apr 26, 2014, 4:18:09 AM4/26/14
to
of normal operation. Like horizontal output drive in some (now older)
TVs, but different purpose. IIRC in case of failure fuses were supposed
to blow before damage to more valuable equipment occurred.
?-)
josephkk
Apr 26, 2014, 4:25:49 AM4/26/14
to
resumed conduction in SCRs. It is often specified (or at least used to
be).
?-)
Mike Perkins
Apr 26, 2014, 7:08:11 AM4/26/14
to
Sony had this idea of having 2 GTOs in series to share the flyback
voltage. Not something I would recommend!
Fred Bartoli
Apr 26, 2014, 7:21:58 AM4/26/14
to
Le Fri, 25 Apr 2014 16:48:14 -0500, Tim Williams a écrit:
> "Mike Perkins" <sp...@spam.com> wrote in message
> news:1KqdnUMxCooIJ8fO...@bt.com...
>> Whereas a SCR or TRIAC will themselves have a overriding di/dt
>> specification without any further circuit considerations complicating
>> the issue.
>
> Yeah, AFAIK it's just dV/dt for FET structures. Something about
> forward-biasing the parasitic BJT structure (same idea as thyristor
> dV/dt,
> but much less sensitive).
>
> I don't think I've ever heard it explained why that's a bad thing --
> surely it just manifests as excessive Miller effect at high rates.
> Presumably, the minority carriers also stick around for a while, with an
> effect similar to body diode recovery (taking on the order of ~200ns in
> power devices), which will cause excess dissipation, but not outright
> destruction. Dunno.
>
It's no pb in a flyback-like structure. The FU occurs with bridge-like
> "Mike Perkins" <sp...@spam.com> wrote in message
> news:1KqdnUMxCooIJ8fO...@bt.com...
>> Whereas a SCR or TRIAC will themselves have a overriding di/dt
>> specification without any further circuit considerations complicating
>> the issue.
>
> Yeah, AFAIK it's just dV/dt for FET structures. Something about
> forward-biasing the parasitic BJT structure (same idea as thyristor
> dV/dt,
> but much less sensitive).
>
> I don't think I've ever heard it explained why that's a bad thing --
> surely it just manifests as excessive Miller effect at high rates.
> Presumably, the minority carriers also stick around for a while, with an
> effect similar to body diode recovery (taking on the order of ~200ns in
> power devices), which will cause excess dissipation, but not outright
> destruction. Dunno.
>
ones when you hard turn on one device of the branch. The other device
excess current can't lower the VDS/VCE rise rate and that leads to
destruction (can't use Joerg's copyrighted noises here).
--
Thanks,
Fred.
josephkk
Apr 28, 2014, 7:52:51 AM4/28/14
to
?-)
Mike Perkins
Apr 28, 2014, 8:40:19 AM4/28/14
to
Controlled Switch (GCS).
It's quite easy to find articles of these 70's TVs:
http://www.vintage-radio.net/forum/showthread.php?t=67455
Maynard A. Philbrook Jr.
Apr 28, 2014, 8:33:55 PM4/28/14
to
In article <b5OdnY-7C76o0cPO...@bt.com>, sp...@spam.com
says...
It seems that in many cases there were some sort of
break down issue that you could use to calculate life
expectancy.
Jamie
says...
> > This was not GTOs. They weren't around back then.
> >
> > ?-)
>
> In part you are correct. In those days they were called a Gate
> Controlled Switch (GCS).
>
> It's quite easy to find articles of these 70's TVs:
> http://www.vintage-radio.net/forum/showthread.php?t=67455
>
> --
> Mike Perkins
> Video Solutions Ltd
> www.videosolutions.ltd.uk
>
>
Yes, and they failed very often!
> >
> > ?-)
>
> In part you are correct. In those days they were called a Gate
> Controlled Switch (GCS).
>
> It's quite easy to find articles of these 70's TVs:
> http://www.vintage-radio.net/forum/showthread.php?t=67455
>
> --
> Mike Perkins
> Video Solutions Ltd
> www.videosolutions.ltd.uk
>
>
It seems that in many cases there were some sort of
break down issue that you could use to calculate life
expectancy.
Jamie
Jan Panteltje
Apr 29, 2014, 1:49:41 AM4/29/14
to
On a sunny day (Mon, 28 Apr 2014 20:33:55 -0400) it happened "Maynard A.
Philbrook Jr." <jamie_...@charter.net> wrote in
<MPG.2dc8bd82f...@news.eternal-september.org>:
The ones in the Sony TVs failed mainly becaue bad soldered PCBs.
The drive would be intermittent, and the swith would stay on.
With a normal transistor switch you would just get some irregular scan.
Philbrook Jr." <jamie_...@charter.net> wrote in
<MPG.2dc8bd82f...@news.eternal-september.org>:
The drive would be intermittent, and the swith would stay on.
With a normal transistor switch you would just get some irregular scan.
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