Induction Cooking Table : IGBT keeping to short !

[cLx]

Hello,

A day my induction cooking table did not work anymore (an Brandt TI302BS1).
Opened it, saw a couple of IGBT in bridge configuration (two IRGP4068D), and
the bottom one was shorted. Got some spares, replaced the shorted one, power
on : OK.

Two steaks later (in fact, 1 1/2 uses), got some unsuspected shutdowns, and
sooner, the same IGBT shorts again. What I need to check before daring to
replace the transistor and to retry to power on the beast again ?

I've traced a bit the schematics, but it's obviously incomplete :
http://clx.shacknet.nu/random/IMG_5802.JPG

And a little picture of the board :
http://clx.shacknet.nu/random/IMG_5803.JPG

Thanks !

 

[isw]

In article <50aa7f6d$0$1938$426a74cc@news.free.fr>,
cLx <clx.kat@j'aimail.com.almost.invalid> wrote:

Hello,

A day my induction cooking table did not work anymore (an Brandt TI302BS1).
Opened it, saw a couple of IGBT in bridge configuration (two IRGP4068D), and
the bottom one was shorted. Got some spares, replaced the shorted one, power
on : OK.

Two steaks later (in fact, 1 1/2 uses), got some unsuspected shutdowns, and
sooner, the same IGBT shorts again. What I need to check before daring to
replace the transistor and to retry to power on the beast again ?

I'd go with the "experience tells me that many high-tech appliances are
designed by idiots" notion, and just replace the failed devices with
more robust ones.

Isaac

 

[Franc Zabkar]

On Mon, 19 Nov 2012 19:50:17 +0100, cLx
<clx.kat@j'aimail.com.almost.invalid> put finger to keyboard and
composed:

A day my induction cooking table did not work anymore (an Brandt TI302BS1).
Opened it, saw a couple of IGBT in bridge configuration (two IRGP4068D), and
the bottom one was shorted. Got some spares, replaced the shorted one, power
on : OK.

Two steaks later (in fact, 1 1/2 uses), got some unsuspected shutdowns, and
sooner, the same IGBT shorts again. What I need to check before daring to
replace the transistor and to retry to power on the beast again ?

I've traced a bit the schematics, but it's obviously incomplete :
http://clx.shacknet.nu/random/IMG_5802.JPG

I don't have any experience with these appliances, but my approach
would be to replace both IGBTs and all the capacitors, especially the
two 0.68uF film or polypropylene (?) types.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

 

[cLx]

On 20/11/2012 06:20, isw wrote:

In article <50aa7f6d$0$1938$426a74cc@news.free.fr>,
cLx <clx.kat@j'aimail.com.almost.invalid> wrote:

Hello,

A day my induction cooking table did not work anymore (an Brandt TI302BS1).
Opened it, saw a couple of IGBT in bridge configuration (two IRGP4068D), and
the bottom one was shorted. Got some spares, replaced the shorted one, power
on : OK.

Two steaks later (in fact, 1 1/2 uses), got some unsuspected shutdowns, and
sooner, the same IGBT shorts again. What I need to check before daring to
replace the transistor and to retry to power on the beast again ?

I'd go with the "experience tells me that many high-tech appliances are
designed by idiots" notion, and just replace the failed devices with
more robust ones.

I thought about that, but i'm afraid to choose something which would present
more gate capacitance than the originals IRGP4068D. I've closely inspected
the Kapton isolation, but new thermal paste under it already.

cLx

 

[cLx]

On 20/11/2012 20:24, Franc Zabkar wrote:

On Mon, 19 Nov 2012 19:50:17 +0100, cLx
clx.kat@j'aimail.com.almost.invalid> put finger to keyboard and
composed:

A day my induction cooking table did not work anymore (an Brandt TI302BS1).
Opened it, saw a couple of IGBT in bridge configuration (two IRGP4068D), and
the bottom one was shorted. Got some spares, replaced the shorted one, power
on : OK.

Two steaks later (in fact, 1 1/2 uses), got some unsuspected shutdowns, and
sooner, the same IGBT shorts again. What I need to check before daring to
replace the transistor and to retry to power on the beast again ?

I've traced a bit the schematics, but it's obviously incomplete :
http://clx.shacknet.nu/random/IMG_5802.JPG

I don't have any experience with these appliances, but my approach
would be to replace both IGBTs and all the capacitors, especially the
two 0.68uF film or polypropylene (?) types.

Thanks for your advice. It's polypropylene caps I guess. There is a picture :
http://clx.shacknet.nu/random/IMG_5956.JPG
Any recommended source ?

I'll also change the two "snubber like" 47nF MKP capacitors (mounted from the
common node of transistors and coil to both supply rails).

 

[Franc Zabkar]

On Tue, 20 Nov 2012 21:28:14 +0100, cLx
<clx.kat@j'aimail.com.almost.invalid> put finger to keyboard and
composed:

It's polypropylene caps I guess.

There is a picture :
http://clx.shacknet.nu/random/IMG_5956.JPG

Any recommended source ?

This appears to be the manufacturer's product page:
http://www.epcos.com/web/generator/Web/Sections/ProductCatalog/Capacitors/FilmCapacitors/MetallizedPolypropylene/Page,locale=en.html

Curiously, the construction is "MFP" which is Metallized Polypropylene
Film, but the datasheet for the type, B32669, lists it as "MKP", and
the lowest capacitance is 1uF.

I'd try Mouser, Digikey, Farnell, RS Components.

I'll also change the two "snubber like" 47nF MKP capacitors (mounted from the
common node of transistors and coil to both supply rails).

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

 

[amdx]

On 11/19/2012 12:50 PM, cLx wrote:

Hello,

A day my induction cooking table did not work anymore (an Brandt TI302BS1).
Opened it, saw a couple of IGBT in bridge configuration (two IRGP4068D), and
the bottom one was shorted. Got some spares, replaced the shorted one, power
on : OK.

Two steaks later (in fact, 1 1/2 uses), got some unsuspected shutdowns, and
sooner, the same IGBT shorts again. What I need to check before daring to
replace the transistor and to retry to power on the beast again ?

I've traced a bit the schematics, but it's obviously incomplete :
http://clx.shacknet.nu/random/IMG_5802.JPG

And a little picture of the board :
http://clx.shacknet.nu/random/IMG_5803.JPG

Thanks !

Sometimes a call to the company or the service center will get an
answer like, " oh ya, you need to replace #%&#@ or it will keep shorting
the bottom one.
Mikek

 

[Arfa Daily]

"cLx" <clx.kat@j'aimail.com.almost.invalid> wrote in message
news:50abe7e4$0$1985$426a74cc@news.free.fr...

On 20/11/2012 20:24, Franc Zabkar wrote:
On Mon, 19 Nov 2012 19:50:17 +0100, cLx
clx.kat@j'aimail.com.almost.invalid> put finger to keyboard and
composed:

A day my induction cooking table did not work anymore (an Brandt
TI302BS1).
Opened it, saw a couple of IGBT in bridge configuration (two IRGP4068D),
and
the bottom one was shorted. Got some spares, replaced the shorted one,
power
on : OK.

Two steaks later (in fact, 1 1/2 uses), got some unsuspected shutdowns,
and
sooner, the same IGBT shorts again. What I need to check before daring
to
replace the transistor and to retry to power on the beast again ?

I've traced a bit the schematics, but it's obviously incomplete :
http://clx.shacknet.nu/random/IMG_5802.JPG

I don't have any experience with these appliances, but my approach
would be to replace both IGBTs and all the capacitors, especially the
two 0.68uF film or polypropylene (?) types.

Thanks for your advice. It's polypropylene caps I guess. There is a
picture :
http://clx.shacknet.nu/random/IMG_5956.JPG
Any recommended source ?

I'll also change the two "snubber like" 47nF MKP capacitors (mounted from
the
common node of transistors and coil to both supply rails).

I'm with Franc on this. Replace both devices and all caps near them.

IGBTs are my least favourite power switching devices. I've always found them
hugely over-priced compared to FETs, and extremely fussy about their
operating conditions. I have also been told by a friend of mine that works
with them a lot, that they are *extremely* intolerant of having their gate
terminal touched when they are not in-circuit. He says that they can be
damaged as a result, so that's maybe something else that could have been a
contributory factor in the device re-failing.

Arfa

 

[Robert Macy]

On Nov 19, 11:50 am, cLx <clx.kat@j'aimail.com.almost.invalid> wrote:

Hello,

A day my induction cooking table did not work anymore (an Brandt TI302BS1).
Opened it, saw a couple of IGBT in bridge configuration (two IRGP4068D), and
the bottom one was shorted. Got some spares, replaced the shorted one, power
on : OK.

Two steaks later (in fact, 1 1/2 uses), got some unsuspected shutdowns, and
sooner, the same IGBT shorts again. What I need to check before daring to
replace the transistor and to retry to power on the beast again ?

I've traced a bit the schematics, but it's obviously incomplete :http://clx.shacknet.nu/random/IMG_5802.JPG

And a little picture of the board :http://clx.shacknet.nu/random/IMG_5803..JPG

Thanks !

From memory, shorting a bipolar structure has significance. Like, over
current blows the 'emitter' wire off - OPEN. And, over voltage
avalanches between the collector and the emitter, welding a small
nonsemiconductor material connection - SHORT. Anything that makes you
have an overvoltage, like a snubber circuit, or ?? might be 'killing'
your part. If the esr goes way up on your DC filter cap...?

Plus, I've had too many designers count on the two components to be
somewhat matched, come from the same lot, have similar switching
characteristics. Thus, replace both, each time.

Don't forget proper handling of the component when you replace. Static
discharges, especially during winter months, can be pretty robust May
not kill the part today, just weaken it enough to die tomorrow.

 

[Jon Elson]

Arfa Daily wrote:

IGBTs are my least favourite power switching devices. I've always found
them hugely over-priced compared to FETs, and extremely fussy about their
operating conditions.

The big problem with IGBTs is they are a parallel structure of many
bipolar transistors, with POSITIVE temperature coefficient. So, they
do not balance current across the die well. When driven hard into
saturation, they balance better. So, the secret an IR app engineer
told me years ago is you have to drive them hard into saturation,
and never allow them to stay in the linear region for more than
a few ns, if possible. (You can only do so much of this during
turnoff, however.)

Jon

 

[Arfa Daily]

"Jon Elson" <jmelson@wustl.edu> wrote in message
news:-OCdnSJfR6rY3DDNnZ2dnUVZ_rSdnZ2d@giganews.com...

Arfa Daily wrote:


IGBTs are my least favourite power switching devices. I've always found
them hugely over-priced compared to FETs, and extremely fussy about their
operating conditions.

The big problem with IGBTs is they are a parallel structure of many
bipolar transistors, with POSITIVE temperature coefficient. So, they
do not balance current across the die well. When driven hard into
saturation, they balance better. So, the secret an IR app engineer
told me years ago is you have to drive them hard into saturation,
and never allow them to stay in the linear region for more than
a few ns, if possible. (You can only do so much of this during
turnoff, however.)

Jon

What I've never really understood, is what supposed advantages IGBTs have
over FETs. A while ago, I had the misfortune to work on a switcher that was
in a Yammy powered speaker. It used a pair of IGBTs that were about eight
quid apiece from memory. Much like the OP's induction heater, it would run
fine for a while, and then the stupid things would just destroy themselves
again - and I mean violently, legs actually blown off, and all that good
stuff. I mend a lot of switch mode power supplies, and for the most part,
their failure modes and what needs to be done to obtain a reliable fix, hold
no mysteries for me. But after about the fourth set of devices that I put in
the Yammy, along with just about every other component in the surrounding
area, I gave up on it. Many switchers of similar size and ratings, use an
almost identical topology, but with a pair of FETs. Typically a couple of
quid apiece, and in my estimation, *much* more robust. So with power FETs
rated to 800 volts and staggering amounts of amps being readily available
almost for pence, why would anyone actually design with IGBTs ?

Arfa

 

[N_Cook]

Arfa Daily <arfa.daily@ntlworld.com> wrote in message
news:nMArs.896789$ti6.38587@fx20.am4...

"Jon Elson" <jmelson@wustl.edu> wrote in message
news:-OCdnSJfR6rY3DDNnZ2dnUVZ_rSdnZ2d@giganews.com...
Arfa Daily wrote:


IGBTs are my least favourite power switching devices. I've always found
them hugely over-priced compared to FETs, and extremely fussy about
their
operating conditions.

The big problem with IGBTs is they are a parallel structure of many
bipolar transistors, with POSITIVE temperature coefficient. So, they
do not balance current across the die well. When driven hard into
saturation, they balance better. So, the secret an IR app engineer
told me years ago is you have to drive them hard into saturation,
and never allow them to stay in the linear region for more than
a few ns, if possible. (You can only do so much of this during
turnoff, however.)

Jon



What I've never really understood, is what supposed advantages IGBTs have
over FETs. A while ago, I had the misfortune to work on a switcher that
was
in a Yammy powered speaker. It used a pair of IGBTs that were about eight
quid apiece from memory. Much like the OP's induction heater, it would run
fine for a while, and then the stupid things would just destroy themselves
again - and I mean violently, legs actually blown off, and all that good
stuff. I mend a lot of switch mode power supplies, and for the most part,
their failure modes and what needs to be done to obtain a reliable fix,
hold
no mysteries for me. But after about the fourth set of devices that I put
in
the Yammy, along with just about every other component in the surrounding
area, I gave up on it. Many switchers of similar size and ratings, use an
almost identical topology, but with a pair of FETs. Typically a couple of
quid apiece, and in my estimation, *much* more robust. So with power FETs
rated to 800 volts and staggering amounts of amps being readily available
almost for pence, why would anyone actually design with IGBTs ?

Arfa

Is there any rules for substituting powerFETs for IGBTs in such situations
that you had there, assuming you are not averse to going against the
designer's wishes?

 

[N_Cook]

Jon Elson <jmelson@wustl.edu> wrote in message
news:-OCdnSJfR6rY3DDNnZ2dnUVZ_rSdnZ2d@giganews.com...

Arfa Daily wrote:


IGBTs are my least favourite power switching devices. I've always found
them hugely over-priced compared to FETs, and extremely fussy about
their
operating conditions.

The big problem with IGBTs is they are a parallel structure of many
bipolar transistors, with POSITIVE temperature coefficient. So, they
do not balance current across the die well. When driven hard into
saturation, they balance better. So, the secret an IR app engineer
told me years ago is you have to drive them hard into saturation,
and never allow them to stay in the linear region for more than
a few ns, if possible. (You can only do so much of this during
turnoff, however.)

Jon

Thanks for the insight, I'll try to remember the warning

 

[cLx]

On 21/11/2012 22:10, Jon Elson wrote:

Arfa Daily wrote:


IGBTs are my least favourite power switching devices. I've always found
them hugely over-priced compared to FETs, and extremely fussy about their
operating conditions.

The big problem with IGBTs is they are a parallel structure of many
bipolar transistors, with POSITIVE temperature coefficient. So, they
do not balance current across the die well. When driven hard into
saturation, they balance better. So, the secret an IR app engineer
told me years ago is you have to drive them hard into saturation,
and never allow them to stay in the linear region for more than
a few ns, if possible. (You can only do so much of this during
turnoff, however.)

Jon

I did not designed the gate control circuit on that applicance... I hope
there is no problem there.

 

[Arfa Daily]

"N_Cook" <diverse@tcp.co.uk> wrote in message
news:k8ndaa$f6c$1@dont-email.me...

Arfa Daily <arfa.daily@ntlworld.com> wrote in message
news:nMArs.896789$ti6.38587@fx20.am4...


"Jon Elson" <jmelson@wustl.edu> wrote in message
news:-OCdnSJfR6rY3DDNnZ2dnUVZ_rSdnZ2d@giganews.com...
Arfa Daily wrote:


IGBTs are my least favourite power switching devices. I've always
found
them hugely over-priced compared to FETs, and extremely fussy about
their
operating conditions.

The big problem with IGBTs is they are a parallel structure of many
bipolar transistors, with POSITIVE temperature coefficient. So, they
do not balance current across the die well. When driven hard into
saturation, they balance better. So, the secret an IR app engineer
told me years ago is you have to drive them hard into saturation,
and never allow them to stay in the linear region for more than
a few ns, if possible. (You can only do so much of this during
turnoff, however.)

Jon



What I've never really understood, is what supposed advantages IGBTs have
over FETs. A while ago, I had the misfortune to work on a switcher that
was
in a Yammy powered speaker. It used a pair of IGBTs that were about eight
quid apiece from memory. Much like the OP's induction heater, it would
run
fine for a while, and then the stupid things would just destroy
themselves
again - and I mean violently, legs actually blown off, and all that good
stuff. I mend a lot of switch mode power supplies, and for the most part,
their failure modes and what needs to be done to obtain a reliable fix,
hold
no mysteries for me. But after about the fourth set of devices that I put
in
the Yammy, along with just about every other component in the surrounding
area, I gave up on it. Many switchers of similar size and ratings, use an
almost identical topology, but with a pair of FETs. Typically a couple of
quid apiece, and in my estimation, *much* more robust. So with power FETs
rated to 800 volts and staggering amounts of amps being readily available
almost for pence, why would anyone actually design with IGBTs ?

Arfa



Is there any rules for substituting powerFETs for IGBTs in such situations
that you had there, assuming you are not averse to going against the
designer's wishes?

I don't know. I must admit that at the time, I *did* consider trying exactly
that, but you know what it's like when you get one of these soul-destroying
jobs. I wrestled for several days with the idea of giving it one more go
with FETs in place of the IGBTs, but in the end, the owner said that if it
was going to be a lot of trouble, and absolute future reliability couldn't
be reasonably guaranteed, then he would just scrap it. I must admit that I
then drew a deep breath of relief, bundled it back together, and cheerfully
gave him it back. Next time, maybe ...

Arfa

 

[Spehro Pefhany]

On Fri, 23 Nov 2012 01:59:45 -0000, the renowned "Arfa Daily"
<arfa.daily@ntlworld.com> wrote:

So with power FETs
rated to 800 volts and staggering amounts of amps being readily available
almost for pence, why would anyone actually design with IGBTs ?

The main reason is that they're considerably cheaper when you need
both high voltage rating _and_ high current rating. That's because
they use less silicon die area. On consumer products the cheapest
component that will do the job acceptably well usually gets designed
in. Try pricing a 30A 800V MOSFET vs. a similar rating in a IGBT.. the
MOSFET will probably be 5x the price.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

 

[N_Cook]

Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> wrote in message
news:kr63b8prd6sisedo1g9sqihbek45jifv05@4ax.com...

On Fri, 23 Nov 2012 01:59:45 -0000, the renowned "Arfa Daily"
arfa.daily@ntlworld.com> wrote:

So with power FETs
rated to 800 volts and staggering amounts of amps being readily available
almost for pence, why would anyone actually design with IGBTs ?

The main reason is that they're considerably cheaper when you need
both high voltage rating _and_ high current rating. That's because
they use less silicon die area. On consumer products the cheapest
component that will do the job acceptably well usually gets designed
in. Try pricing a 30A 800V MOSFET vs. a similar rating in a IGBT.. the
MOSFET will probably be 5x the price.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers:
http://www.trexon.com
Embedded software/hardware/analog Info for designers:
http://www.speff.com

Assuming there is space to put 2x powerFETs in place and the switching f is
not beyond sensible powerFET territory, other than adjusting the gate drive
, any other considerations ?

 

[josephkk]

On Sun, 25 Nov 2012 08:46:48 -0000, "N_Cook" <diverse@tcp.co.uk> wrote:

Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> wrote in message
news:kr63b8prd6sisedo1g9sqihbek45jifv05@4ax.com...
On Fri, 23 Nov 2012 01:59:45 -0000, the renowned "Arfa Daily"
arfa.daily@ntlworld.com> wrote:

So with power FETs
rated to 800 volts and staggering amounts of amps being readily available
almost for pence, why would anyone actually design with IGBTs ?

The main reason is that they're considerably cheaper when you need
both high voltage rating _and_ high current rating. That's because
they use less silicon die area. On consumer products the cheapest
component that will do the job acceptably well usually gets designed
in. Try pricing a 30A 800V MOSFET vs. a similar rating in a IGBT.. the
MOSFET will probably be 5x the price.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers:
http://www.trexon.com
Embedded software/hardware/analog Info for designers:
http://www.speff.com


Assuming there is space to put 2x powerFETs in place and the switching f is
not beyond sensible powerFET territory, other than adjusting the gate drive
, any other considerations ?

Since IGBTs tend to be rather slow, power fet speed is not normally the
issue. Just the same IGBTs almost may be called IG-GTOs.

?-)

 

[Jon Elson]

Arfa Daily wrote:

What I've never really understood, is what supposed advantages IGBTs have
over FETs. A while ago, I had the misfortune to work on a switcher that
was in a Yammy powered speaker. It used a pair of IGBTs that were about
eight quid apiece from memory. Much like the OP's induction heater, it
would run fine for a while, and then the stupid things would just destroy
themselves again - and I mean violently, legs actually blown off, and all
that good stuff. I mend a lot of switch mode power supplies, and for the
most part, their failure modes and what needs to be done to obtain a
reliable fix, hold no mysteries for me. But after about the fourth set of
devices that I put in the Yammy, along with just about every other
component in the surrounding area, I gave up on it. Many switchers of
similar size and ratings, use an almost identical topology, but with a
pair of FETs. Typically a couple of quid apiece, and in my estimation,
*much* more robust. So with power FETs rated to 800 volts and staggering
amounts of amps being readily available almost for pence, why would anyone
actually design with IGBTs ?
Below 400 V there is probably no benefit to an IGBT. At 400 V and above,

MOSFETs start to show a higher on-resistance. The higher the breakdown
voltage, the higher the on resistance. IGBTs have a constant Vce drop of
about 2V or better, up to several times continuous rated current. That
starts to look real good in serious power devices like motor drives.

IGBTs in an audio amp sounds really odd to me, I'll bet a set of
FETs could have been dropped into it perfectly.

Jon

 

[Phil Allison]

"Jon Elson"

Below 400 V there is probably no benefit to an IGBT. At 400 V and above,
MOSFETs start to show a higher on-resistance. The higher the breakdown
voltage, the higher the on resistance. IGBTs have a constant Vce drop of
about 2V or better, up to several times continuous rated current. That
starts to look real good in serious power devices like motor drives.

IGBTs in an audio amp sounds really odd to me, I'll bet a set of
FETs could have been dropped into it perfectly.

** Switching PSUs in many high powered audio amps use IGBTs - often in
parallel groups. The topology is a driven, square wave inverter - no
feedback or regulation is needed.

The dodgiest time is at first switch on, when the filter electros present a
dead short to the DC output. Usually, the drive wave begins with a very low
duty cycle ramping slowly up to full square wave. Drive frequencies are in
the order of 100kHz to 150kHz.

Readily available, low cost mosfets are not in the game.



..... Phil