IR2110 gate driver issues.

[Pooh Bear]

Hi all,

I'm using an IR2110 high and low side gate driver in a smps that I
mentioned some time back in the group under the thread 'should I use a
SG3525'.

I've had some 'odd' power device failures that I didn't expect in
entirely benign situations, such as the half bridge output simply
driving the primary of my transformer.

I realised that it happened a couple of times when I wound down the
input volts ( I'm supplying the board via a variac and isolating
transfomer for development ).

The IR2110 has undervoltage lockout. Fine ! I checked it carefully today
and the UVLO for the low side and high side aren't linked. Indeed a
careful look at the data sheet does indeed show that there's no
connection. The low side drive activates at about 8V and the high side
about a volt higher.

Needless to say this creates 'issues' !

Anyone here used this part and care to comment ?


Regds, Graham

 

[Harry Dellamano]

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:42A8A682.2B3B0D5E@hotmail.com...

Hi all,

I'm using an IR2110 high and low side gate driver in a smps that I
mentioned some time back in the group under the thread 'should I use a
SG3525'.

I've had some 'odd' power device failures that I didn't expect in
entirely benign situations, such as the half bridge output simply
driving the primary of my transformer.

I realised that it happened a couple of times when I wound down the
input volts ( I'm supplying the board via a variac and isolating
transfomer for development ).

The IR2110 has undervoltage lockout. Fine ! I checked it carefully today
and the UVLO for the low side and high side aren't linked. Indeed a
careful look at the data sheet does indeed show that there's no
connection. The low side drive activates at about 8V and the high side
about a volt higher.

Needless to say this creates 'issues' !

Anyone here used this part and care to comment ?


Regds, Graham

Hey Poop,
What is this, Electronics 101! Sure these parts are old enought. You should
worry about electromigration.
The SG3525A has UVLO at about 7VDC and locks it's outputs low. Make sure it
goes down before the IR2110. YMMV with the SG3525.

Harry

 

[Pooh Bear]

Harry Dellamano wrote:

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:42A8A682.2B3B0D5E@hotmail.com...
Hi all,

I'm using an IR2110 high and low side gate driver in a smps that I
mentioned some time back in the group under the thread 'should I use a
SG3525'.

I've had some 'odd' power device failures that I didn't expect in
entirely benign situations, such as the half bridge output simply
driving the primary of my transformer.

I realised that it happened a couple of times when I wound down the
input volts ( I'm supplying the board via a variac and isolating
transfomer for development ).

The IR2110 has undervoltage lockout. Fine ! I checked it carefully today
and the UVLO for the low side and high side aren't linked. Indeed a
careful look at the data sheet does indeed show that there's no
connection. The low side drive activates at about 8V and the high side
about a volt higher.

Needless to say this creates 'issues' !

Anyone here used this part and care to comment ?


Regds, Graham

Hey Poop,
What is this, Electronics 101! Sure these parts are old enought. You should
worry about electromigration.

LOL !

The SG3525A has UVLO at about 7VDC and locks it's outputs low. Make sure it
goes down before the IR2110. YMMV with the SG3525.

The 3525 isn't the prob - it does indeed UVLO around 7V and has 300mV of
hysteresis.

The 2110 low side UVLO appears to be @ 8V and the high side @ around 8.9V. So as
the power rails sag the high side device stops conducting but the low side
doesn't. Interesting. Doesn't appear to be any hysteresis on the 2110 either.

I reckon I'm going to have to implement my own undervoltage lock out to stop the
3525 @ about 10V.

Just curious if anyone else had noticed this.

Choice of devices was partly determined / influenced by their use by the major
US manufacturer of pro-audio amplifiers in a similar application.

Graham

 

[Winfield Hill]

Pooh Bear wrote...

I'm using an IR2110 high and low side gate driver in a smps that
I mentioned some time back in the group under the thread 'should
I use a SG3525'.

I've had some 'odd' power device failures that I didn't expect in
entirely benign situations, such as the half bridge output simply
driving the primary of my transformer.

Device failure meaning damaged components, or meaning, a FET that
didn't do what you expected under a certain circumstance, but yet
wasn't actually damaged.

I realised that it happened a couple of times when I wound down the
input volts ( I'm supplying the board via a variac and isolating
transfomer for development ).

The IR2110 has undervoltage lockout. Fine! I checked it carefully
today and the UVLO for the low side and high side aren't linked.
Indeed a careful look at the data sheet does indeed show that
there's no connection. The low side drive activates at about 8V
and the high side about a volt higher.

IR has to separately detect the low-side and high-side voltages,
because the latter is the voltage across the flying capacitor.

The mismatch you observed sounds good: the high side should stop
working well before the low side, thereby preventing any shoothro
current, which could be disasterous.

Needless to say this creates 'issues'!
Anyone here used this part and care to comment?

Let's hear about your issues.

BTW, recognizing the need for low-voltage protection, and the need
for a benign response to low-voltage conditions, you could easily
add a comparator operating at lower voltages, plus shutoff gates
managing the IR2110's three logic inputs, per your special needs.


--
Thanks,
- Win

 

[Joerg]

Hello Winfield,

BTW, recognizing the need for low-voltage protection, and the need
for a benign response to low-voltage conditions, you could easily
add a comparator operating at lower voltages, plus shutoff gates
managing the IR2110's three logic inputs, per your special needs.

Or use a TLV431 for UVLO purposes. They are pretty accurate and cheap.

Regards, Joerg

http://www.analogconsultants.com

 

[Pooh Bear]

Winfield Hill wrote:

Pooh Bear wrote...

I'm using an IR2110 high and low side gate driver in a smps that
I mentioned some time back in the group under the thread 'should
I use a SG3525'.

I've had some 'odd' power device failures that I didn't expect in
entirely benign situations, such as the half bridge output simply
driving the primary of my transformer.

Device failure meaning damaged components, or meaning, a FET that
didn't do what you expected under a certain circumstance, but yet
wasn't actually damaged.

Device going short. Either just the high side device or both. I've
established to my satisfaction that there are 2 failure scenarios.

1. Ramping the voltage down on the variac ( quickly ) . E.g. after
I've been testing @ line voltage. There's a bzzt and the high side device
goes short. I suspect a mixture of the UVLO mismatches and possible
'mis-track' of the main bus and supervisory rail. Doesn't happen if I
ramp the volts down slowly ( or so it seems ). Hence my thoughts about
the droop of the rails.

2. Both devices fail - this first happened after I'd been running the
transformer primary only for about 1/2 hour just to establish likely
practical core temp rise. It ran fine for ages - I turned my back to do
some calcs and the thing bzzt'ed at me. It was still working so I thought
I was hearing things ! Did it terminally 3 mins later. Looking closely
I'm seeing the high side drive terminate prematurely under circumstances
I have yet to exactly determine the cause of. Maybe insufficient
bootstrap C ? Was looking at this last thing today. Will investigate
further tomorrow wrt all the drive waveforms.

I realised that it happened a couple of times when I wound down the
input volts ( I'm supplying the board via a variac and isolating
transfomer for development ).

The IR2110 has undervoltage lockout. Fine! I checked it carefully
today and the UVLO for the low side and high side aren't linked.
Indeed a careful look at the data sheet does indeed show that
there's no connection. The low side drive activates at about 8V
and the high side about a volt higher.

IR has to separately detect the low-side and high-side voltages,
because the latter is the voltage across the flying capacitor.

True. I wish they'd OR the UVLOs though.

The mismatch you observed sounds good: the high side should stop
working well before the low side, thereby preventing any shoothro
current, which could be disasterous.

I'd prefer it if both terminated together !

Needless to say this creates 'issues'!
Anyone here used this part and care to comment?

Let's hear about your issues.

Well, the devices failing for one !

The 2110 UVLO is sensitive to line ripple. It appears to result in a
effect that's like weird duty cycles when it's hovering around the UVLO
threshold(s).

BTW, recognizing the need for low-voltage protection, and the need
for a benign response to low-voltage conditions, you could easily
add a comparator operating at lower voltages, plus shutoff gates
managing the IR2110's three logic inputs, per your special needs.

That's what I imagine I may indeed have to do. Or I can shutdown the
3525.

Was curious if anyone had experienced similar when using the 2110.

Cheers, Graham

p.s. I now understand why smps design has always had a reputation for
being 'tricky'. Also why when quizzed about them - some vendors go all
shy when talking about the reliability of smps versions of their audio
amps ! I have no plans to put anything into production that's marginal.

 

[Pooh Bear]

Joerg wrote:

Hello Winfield,

BTW, recognizing the need for low-voltage protection, and the need
for a benign response to low-voltage conditions, you could easily
add a comparator operating at lower voltages, plus shutoff gates
managing the IR2110's three logic inputs, per your special needs.

Or use a TLV431 for UVLO purposes. They are pretty accurate and cheap.

Regards, Joerg

Guess what I sketched late this afternoon ! With an LM393. It may be wise
to OR my own UVLO on both supervisory and main bus rails.

Graham

 

[Winfield Hill]

Pooh Bear wrote...

Joerg wrote:
Hello Winfield,

BTW, recognizing the need for low-voltage protection, and the need
for a benign response to low-voltage conditions, you could easily
add a comparator operating at lower voltages, plus shutoff gates
managing the IR2110's three logic inputs, per your special needs.

Or use a TLV431 for UVLO purposes. They are pretty accurate and cheap.

Guess what I sketched late this afternoon ! With an LM393. It may be
wise to OR my own UVLO on both supervisory and main bus rails.

Graham, you're way ahead of us. But the real issue is what the actual
operating modes are and their etiologies. We'll discuss that pursuant
to your other response.


--
Thanks,
- Win

 

[Terry Given]

Pooh Bear wrote:

Winfield Hill wrote:


Pooh Bear wrote...

I'm using an IR2110 high and low side gate driver in a smps that
I mentioned some time back in the group under the thread 'should
I use a SG3525'.

I've had some 'odd' power device failures that I didn't expect in
entirely benign situations, such as the half bridge output simply
driving the primary of my transformer.

Device failure meaning damaged components, or meaning, a FET that
didn't do what you expected under a certain circumstance, but yet
wasn't actually damaged.


Device going short. Either just the high side device or both. I've
established to my satisfaction that there are 2 failure scenarios.

1. Ramping the voltage down on the variac ( quickly ) . E.g. after
I've been testing @ line voltage. There's a bzzt and the high side device
goes short. I suspect a mixture of the UVLO mismatches and possible
'mis-track' of the main bus and supervisory rail. Doesn't happen if I
ramp the volts down slowly ( or so it seems ). Hence my thoughts about
the droop of the rails.

2. Both devices fail - this first happened after I'd been running the
transformer primary only for about 1/2 hour just to establish likely
practical core temp rise. It ran fine for ages - I turned my back to do
some calcs and the thing bzzt'ed at me. It was still working so I thought
I was hearing things ! Did it terminally 3 mins later. Looking closely
I'm seeing the high side drive terminate prematurely under circumstances
I have yet to exactly determine the cause of. Maybe insufficient
bootstrap C ? Was looking at this last thing today. Will investigate
further tomorrow wrt all the drive waveforms.



I realised that it happened a couple of times when I wound down the
input volts ( I'm supplying the board via a variac and isolating
transfomer for development ).

The IR2110 has undervoltage lockout. Fine! I checked it carefully
today and the UVLO for the low side and high side aren't linked.
Indeed a careful look at the data sheet does indeed show that
there's no connection. The low side drive activates at about 8V
and the high side about a volt higher.

IR has to separately detect the low-side and high-side voltages,
because the latter is the voltage across the flying capacitor.


True. I wish they'd OR the UVLOs though.


The mismatch you observed sounds good: the high side should stop
working well before the low side, thereby preventing any shoothro
current, which could be disasterous.


I'd prefer it if both terminated together !



Needless to say this creates 'issues'!
Anyone here used this part and care to comment?

Let's hear about your issues.


Well, the devices failing for one !

The 2110 UVLO is sensitive to line ripple. It appears to result in a
effect that's like weird duty cycles when it's hovering around the UVLO
threshold(s).


BTW, recognizing the need for low-voltage protection, and the need
for a benign response to low-voltage conditions, you could easily
add a comparator operating at lower voltages, plus shutoff gates
managing the IR2110's three logic inputs, per your special needs.


That's what I imagine I may indeed have to do. Or I can shutdown the
3525.

Was curious if anyone had experienced similar when using the 2110.

Cheers, Graham

p.s. I now understand why smps design has always had a reputation for
being 'tricky'. Also why when quizzed about them - some vendors go all
shy when talking about the reliability of smps versions of their audio
amps ! I have no plans to put anything into production that's marginal.

what caps are you using for your bootstrap supplies?

Cheers
Terry

 

[Pooh Bear]

Winfield Hill wrote:

Pooh Bear wrote...

Joerg wrote:
Hello Winfield,

BTW, recognizing the need for low-voltage protection, and the need
for a benign response to low-voltage conditions, you could easily
add a comparator operating at lower voltages, plus shutoff gates
managing the IR2110's three logic inputs, per your special needs.

Or use a TLV431 for UVLO purposes. They are pretty accurate and cheap.

Guess what I sketched late this afternoon ! With an LM393. It may be
wise to OR my own UVLO on both supervisory and main bus rails.

Graham, you're way ahead of us. But the real issue is what the actual
operating modes are and their etiologies. We'll discuss that pursuant
to your other response.

Thank you for kind response.

I'm especially interested in what's causing the premature termination ( under
certain circumstances ) of the high side drive. At one point just poking the
probe of a Fluke 77 on the Vboot pin caused the effect ! At times like this 4
channel scopes ( and diff amps ) are a really attractive proposition.

The UVLO issue seems like a trivial one in comparison. Just surprised that I
haven't seen similar measures in other commercial designs I've looked at.

Graham

 

[Pooh Bear]

Terry Given wrote:

Pooh Bear wrote:
Winfield Hill wrote:


Pooh Bear wrote...

I'm using an IR2110 high and low side gate driver in a smps that
I mentioned some time back in the group under the thread 'should
I use a SG3525'.

I've had some 'odd' power device failures that I didn't expect in
entirely benign situations, such as the half bridge output simply
driving the primary of my transformer.

Device failure meaning damaged components, or meaning, a FET that
didn't do what you expected under a certain circumstance, but yet
wasn't actually damaged.


Device going short. Either just the high side device or both. I've
established to my satisfaction that there are 2 failure scenarios.

1. Ramping the voltage down on the variac ( quickly ) . E.g. after
I've been testing @ line voltage. There's a bzzt and the high side device
goes short. I suspect a mixture of the UVLO mismatches and possible
'mis-track' of the main bus and supervisory rail. Doesn't happen if I
ramp the volts down slowly ( or so it seems ). Hence my thoughts about
the droop of the rails.

2. Both devices fail - this first happened after I'd been running the
transformer primary only for about 1/2 hour just to establish likely
practical core temp rise. It ran fine for ages - I turned my back to do
some calcs and the thing bzzt'ed at me. It was still working so I thought
I was hearing things ! Did it terminally 3 mins later. Looking closely
I'm seeing the high side drive terminate prematurely under circumstances
I have yet to exactly determine the cause of. Maybe insufficient
bootstrap C ? Was looking at this last thing today. Will investigate
further tomorrow wrt all the drive waveforms.



I realised that it happened a couple of times when I wound down the
input volts ( I'm supplying the board via a variac and isolating
transfomer for development ).

The IR2110 has undervoltage lockout. Fine! I checked it carefully
today and the UVLO for the low side and high side aren't linked.
Indeed a careful look at the data sheet does indeed show that
there's no connection. The low side drive activates at about 8V
and the high side about a volt higher.

IR has to separately detect the low-side and high-side voltages,
because the latter is the voltage across the flying capacitor.


True. I wish they'd OR the UVLOs though.


The mismatch you observed sounds good: the high side should stop
working well before the low side, thereby preventing any shoothro
current, which could be disasterous.


I'd prefer it if both terminated together !



Needless to say this creates 'issues'!
Anyone here used this part and care to comment?

Let's hear about your issues.


Well, the devices failing for one !

The 2110 UVLO is sensitive to line ripple. It appears to result in a
effect that's like weird duty cycles when it's hovering around the UVLO
threshold(s).


BTW, recognizing the need for low-voltage protection, and the need
for a benign response to low-voltage conditions, you could easily
add a comparator operating at lower voltages, plus shutoff gates
managing the IR2110's three logic inputs, per your special needs.


That's what I imagine I may indeed have to do. Or I can shutdown the
3525.

Was curious if anyone had experienced similar when using the 2110.

Cheers, Graham

p.s. I now understand why smps design has always had a reputation for
being 'tricky'. Also why when quizzed about them - some vendors go all
shy when talking about the reliability of smps versions of their audio
amps ! I have no plans to put anything into production that's marginal.


what caps are you using for your bootstrap supplies?

Box polyester film. You gonna say I should be using ceramic ?

Graham

 

[Pooh Bear]

Harry Dellamano wrote:

Hey Poop,
What is this, Electronics 101!

For you maybe !

Have I seen your name on any ABs I may have read btw ? I'm thinking maybe
Unitrode ?


Graham

 

[Harry Dellamano]

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:42A8FCB3.6A675129@hotmail.com...

Harry Dellamano wrote:

Hey Poop,
What is this, Electronics 101!

For you maybe !

Have I seen your name on any ABs I may have read btw ? I'm thinking maybe
Unitrode ?


Graham

Your thinking of my brother, Robert Mammano, the original designer of the

SG3525 at Silicon General. Now I believe semi retired with TI-Unitrode.
I'm still in El-101.
cheers,
Harry

 

[Pooh Bear]

Harry Dellamano wrote:

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:42A8FCB3.6A675129@hotmail.com...
Harry Dellamano wrote:

Hey Poop,
What is this, Electronics 101!

For you maybe !

Have I seen your name on any ABs I may have read btw ? I'm thinking maybe
Unitrode ?

Graham

Your thinking of my brother, Robert Mammano

Yes that rings bells.

, the original designer of the
SG3525 at Silicon General. Now I believe semi retired with TI-Unitrode.
I'm still in El-101.
cheers,
Harry

Thanks for your input Harry. It's always appreciated.

Graham

 

[Ban]

Pooh Bear wrote:

1. Ramping the voltage down on the variac ( quickly ) . E.g. after
I've been testing @ line voltage. There's a bzzt and the high side
device goes short. I suspect a mixture of the UVLO mismatches and
possible 'mis-track' of the main bus and supervisory rail. Doesn't
happen if I ramp the volts down slowly ( or so it seems ). Hence my
thoughts about the droop of the rails.

2. Both devices fail - this first happened after I'd been running
the transformer primary only for about 1/2 hour just to establish
likely practical core temp rise. It ran fine for ages - I turned my
back to do some calcs and the thing bzzt'ed at me. It was still
working so I thought I was hearing things ! Did it terminally 3 mins
later. Looking closely I'm seeing the high side drive terminate
prematurely under circumstances I have yet to exactly determine the
cause of. Maybe insufficient bootstrap C ? Was looking at this last
thing today. Will investigate further tomorrow wrt all the drive
waveforms.


I realised that it happened a couple of times when I wound down the
input volts ( I'm supplying the board via a variac and isolating
transfomer for development ).

The IR2110 has undervoltage lockout. Fine! I checked it carefully
today and the UVLO for the low side and high side aren't linked.
Indeed a careful look at the data sheet does indeed show that
there's no connection. The low side drive activates at about 8V
and the high side about a volt higher.

IR has to separately detect the low-side and high-side voltages,
because the latter is the voltage across the flying capacitor.

True. I wish they'd OR the UVLOs though.

The mismatch you observed sounds good: the high side should stop
working well before the low side, thereby preventing any shoothro
current, which could be disasterous.

I'd prefer it if both terminated together !


Needless to say this creates 'issues'!
Anyone here used this part and care to comment?

Let's hear about your issues.

Well, the devices failing for one !

The 2110 UVLO is sensitive to line ripple. It appears to result in a
effect that's like weird duty cycles when it's hovering around the
UVLO threshold(s).

BTW, recognizing the need for low-voltage protection, and the need
for a benign response to low-voltage conditions, you could easily
add a comparator operating at lower voltages, plus shutoff gates
managing the IR2110's three logic inputs, per your special needs.

That's what I imagine I may indeed have to do. Or I can shutdown the
3525.

Was curious if anyone had experienced similar when using the 2110.

Cheers, Graham

p.s. I now understand why smps design has always had a reputation for
being 'tricky'. Also why when quizzed about them - some vendors go all
shy when talking about the reliability of smps versions of their audio
amps ! I have no plans to put anything into production that's
marginal.

Pooh, you should see how the charge pump works. By conducting the low side
FET, the bootstrap capacitor gets charged, just the same happens when the
device comes on. Then, when the voltage is sufficient, the device works as
advertized. When you have it too long high, the droop will be enough to
trigger the undervoltage and the device goes low again, to allow the
charging of the cap. So it is made to work well on a full bridge. On a half
bridge a DC component will result, which is a problem with your transformer.
So either you increase the value of the cap, or you drop the chargepump all
together and aliment the upper leg with a separate floating PS, or make a
full-bridge with another driver and use lower supply voltage or a different
transformer.
Maybe your transformer is not pulled down completely because of too high
resistance of the FET or the current shunt, or the 12V auxiliary voltage is
too low?
--
ciao Ban
Bordighera, Italy

 

[Pooh Bear]

Ban wrote:

Pooh Bear wrote:

1. Ramping the voltage down on the variac ( quickly ) . E.g. after
I've been testing @ line voltage. There's a bzzt and the high side
device goes short. I suspect a mixture of the UVLO mismatches and
possible 'mis-track' of the main bus and supervisory rail. Doesn't
happen if I ramp the volts down slowly ( or so it seems ). Hence my
thoughts about the droop of the rails.

2. Both devices fail - this first happened after I'd been running
the transformer primary only for about 1/2 hour just to establish
likely practical core temp rise. It ran fine for ages - I turned my
back to do some calcs and the thing bzzt'ed at me. It was still
working so I thought I was hearing things ! Did it terminally 3 mins
later. Looking closely I'm seeing the high side drive terminate
prematurely under circumstances I have yet to exactly determine the
cause of. Maybe insufficient bootstrap C ? Was looking at this last
thing today. Will investigate further tomorrow wrt all the drive
waveforms.


I realised that it happened a couple of times when I wound down the
input volts ( I'm supplying the board via a variac and isolating
transfomer for development ).

The IR2110 has undervoltage lockout. Fine! I checked it carefully
today and the UVLO for the low side and high side aren't linked.
Indeed a careful look at the data sheet does indeed show that
there's no connection. The low side drive activates at about 8V
and the high side about a volt higher.

IR has to separately detect the low-side and high-side voltages,
because the latter is the voltage across the flying capacitor.

True. I wish they'd OR the UVLOs though.

The mismatch you observed sounds good: the high side should stop
working well before the low side, thereby preventing any shoothro
current, which could be disasterous.

I'd prefer it if both terminated together !


Needless to say this creates 'issues'!
Anyone here used this part and care to comment?

Let's hear about your issues.

Well, the devices failing for one !

The 2110 UVLO is sensitive to line ripple. It appears to result in a
effect that's like weird duty cycles when it's hovering around the
UVLO threshold(s).

BTW, recognizing the need for low-voltage protection, and the need
for a benign response to low-voltage conditions, you could easily
add a comparator operating at lower voltages, plus shutoff gates
managing the IR2110's three logic inputs, per your special needs.

That's what I imagine I may indeed have to do. Or I can shutdown the
3525.

Was curious if anyone had experienced similar when using the 2110.

Cheers, Graham

p.s. I now understand why smps design has always had a reputation for
being 'tricky'. Also why when quizzed about them - some vendors go all
shy when talking about the reliability of smps versions of their audio
amps ! I have no plans to put anything into production that's
marginal.

Pooh, you should see how the charge pump works. By conducting the low side
FET, the bootstrap capacitor gets charged, just the same happens when the
device comes on.

Yes.

Then, when the voltage is sufficient, the device works as
advertized. When you have it too long high, the droop will be enough to
trigger the undervoltage and the device goes low again, to allow the
charging of the cap.

Should not happen if Cboot is large enough. This is something to be checked.

So it is made to work well on a full bridge. On a half
bridge a DC component will result, which is a problem with your transformer.

For sure !

So either you increase the value of the cap,

Agreed. Will investigate this next !

or you drop the chargepump all
together and aliment the upper leg with a separate floating PS,

IR have an app note regarding low frequency operation of the low / high side
drivers that uses a separate charge pump entirely. I am inclined to look at this
route.

or make a full-bridge with another driver and use lower supply voltage or a
different transformer.
Maybe your transformer is not pulled down completely because of too high
resistance of the FET

No. Damn good FETs or IGBTs. Vce sat = 2 V max. Lower for FETs.

or the current shunt, or the 12V auxiliary voltage is too low?

The aux supply is good - around 14V @ variac with max setting.

I suspect there's something I'm missing. I dare say it will 'come out in the
wash' ! This will be interesting !

Thanks, Graham

 

[Terry Given]

Pooh Bear wrote:

Terry Given wrote:


Pooh Bear wrote:

Winfield Hill wrote:



Pooh Bear wrote...


I'm using an IR2110 high and low side gate driver in a smps that
I mentioned some time back in the group under the thread 'should
I use a SG3525'.

I've had some 'odd' power device failures that I didn't expect in
entirely benign situations, such as the half bridge output simply
driving the primary of my transformer.

Device failure meaning damaged components, or meaning, a FET that
didn't do what you expected under a certain circumstance, but yet
wasn't actually damaged.


Device going short. Either just the high side device or both. I've
established to my satisfaction that there are 2 failure scenarios.

1. Ramping the voltage down on the variac ( quickly ) . E.g. after
I've been testing @ line voltage. There's a bzzt and the high side device
goes short. I suspect a mixture of the UVLO mismatches and possible
'mis-track' of the main bus and supervisory rail. Doesn't happen if I
ramp the volts down slowly ( or so it seems ). Hence my thoughts about
the droop of the rails.

2. Both devices fail - this first happened after I'd been running the
transformer primary only for about 1/2 hour just to establish likely
practical core temp rise. It ran fine for ages - I turned my back to do
some calcs and the thing bzzt'ed at me. It was still working so I thought
I was hearing things ! Did it terminally 3 mins later. Looking closely
I'm seeing the high side drive terminate prematurely under circumstances
I have yet to exactly determine the cause of. Maybe insufficient
bootstrap C ? Was looking at this last thing today. Will investigate
further tomorrow wrt all the drive waveforms.




I realised that it happened a couple of times when I wound down the
input volts ( I'm supplying the board via a variac and isolating
transfomer for development ).

The IR2110 has undervoltage lockout. Fine! I checked it carefully
today and the UVLO for the low side and high side aren't linked.
Indeed a careful look at the data sheet does indeed show that
there's no connection. The low side drive activates at about 8V
and the high side about a volt higher.

IR has to separately detect the low-side and high-side voltages,
because the latter is the voltage across the flying capacitor.


True. I wish they'd OR the UVLOs though.



The mismatch you observed sounds good: the high side should stop
working well before the low side, thereby preventing any shoothro
current, which could be disasterous.


I'd prefer it if both terminated together !




Needless to say this creates 'issues'!
Anyone here used this part and care to comment?

Let's hear about your issues.


Well, the devices failing for one !

The 2110 UVLO is sensitive to line ripple. It appears to result in a
effect that's like weird duty cycles when it's hovering around the UVLO
threshold(s).



BTW, recognizing the need for low-voltage protection, and the need
for a benign response to low-voltage conditions, you could easily
add a comparator operating at lower voltages, plus shutoff gates
managing the IR2110's three logic inputs, per your special needs.


That's what I imagine I may indeed have to do. Or I can shutdown the
3525.

Was curious if anyone had experienced similar when using the 2110.

Cheers, Graham

p.s. I now understand why smps design has always had a reputation for
being 'tricky'. Also why when quizzed about them - some vendors go all
shy when talking about the reliability of smps versions of their audio
amps ! I have no plans to put anything into production that's marginal.


what caps are you using for your bootstrap supplies?


Box polyester film. You gonna say I should be using ceramic ?

Graham

not until I read the datasheet. But I would caution against Z5U/Y5V,
they are a path to temperature-related auto-self-destruct features.

make sure there isnt too much ESR, the capacitance is stable with
voltage & temperature, its happy with the peak current (maybe as high as
Vboost/Rgate) and there is fuck all inductance in the gatedrive loops.

it can be a good idea with bootstrap supplies to use a couple of volts
more than the lower supply, because of the load-dependant voltage drop
across the lower switch (and, of course, the diode).

I presume your diode is a fast HV diode.

I was once involved on the periphery with a cost-down of a small AC
drive, 1% to 10% parts, that sort of thing. Changing the charge-pump
gatedrive 100nF rectangular blue plastic film caps to cheap ceramic ones
resulted in a 100% fatality rate on all 10 prototype units, about 20
minutes into a thermal test. That change never made it to production.

Cheers
Terry

 

[Pooh Bear]

Terry Given wrote:

Pooh Bear wrote:
Terry Given wrote:

Pooh Bear wrote:

Winfield Hill wrote:

Pooh Bear wrote...

I'm using an IR2110 high and low side gate driver in a smps that
I mentioned some time back in the group under the thread 'should
I use a SG3525'.

I've had some 'odd' power device failures that I didn't expect in
entirely benign situations, such as the half bridge output simply
driving the primary of my transformer.

Device failure meaning damaged components, or meaning, a FET that
didn't do what you expected under a certain circumstance, but yet
wasn't actually damaged.


Device going short. Either just the high side device or both. I've
established to my satisfaction that there are 2 failure scenarios.

1. Ramping the voltage down on the variac ( quickly ) . E.g. after
I've been testing @ line voltage. There's a bzzt and the high side device
goes short. I suspect a mixture of the UVLO mismatches and possible
'mis-track' of the main bus and supervisory rail. Doesn't happen if I
ramp the volts down slowly ( or so it seems ). Hence my thoughts about
the droop of the rails.

2. Both devices fail - this first happened after I'd been running the
transformer primary only for about 1/2 hour just to establish likely
practical core temp rise. It ran fine for ages - I turned my back to do
some calcs and the thing bzzt'ed at me. It was still working so I thought
I was hearing things ! Did it terminally 3 mins later. Looking closely
I'm seeing the high side drive terminate prematurely under circumstances
I have yet to exactly determine the cause of. Maybe insufficient
bootstrap C ? Was looking at this last thing today. Will investigate
further tomorrow wrt all the drive waveforms.


I realised that it happened a couple of times when I wound down the
input volts ( I'm supplying the board via a variac and isolating
transfomer for development ).

The IR2110 has undervoltage lockout. Fine! I checked it carefully
today and the UVLO for the low side and high side aren't linked.
Indeed a careful look at the data sheet does indeed show that
there's no connection. The low side drive activates at about 8V
and the high side about a volt higher.

IR has to separately detect the low-side and high-side voltages,
because the latter is the voltage across the flying capacitor.


True. I wish they'd OR the UVLOs though.


The mismatch you observed sounds good: the high side should stop
working well before the low side, thereby preventing any shoothro
current, which could be disasterous.


I'd prefer it if both terminated together !


Needless to say this creates 'issues'!
Anyone here used this part and care to comment?

Let's hear about your issues.


Well, the devices failing for one !

The 2110 UVLO is sensitive to line ripple. It appears to result in a
effect that's like weird duty cycles when it's hovering around the UVLO
threshold(s).



BTW, recognizing the need for low-voltage protection, and the need
for a benign response to low-voltage conditions, you could easily
add a comparator operating at lower voltages, plus shutoff gates
managing the IR2110's three logic inputs, per your special needs.


That's what I imagine I may indeed have to do. Or I can shutdown the
3525.

Was curious if anyone had experienced similar when using the 2110.

Cheers, Graham

p.s. I now understand why smps design has always had a reputation for
being 'tricky'. Also why when quizzed about them - some vendors go all
shy when talking about the reliability of smps versions of their audio
amps ! I have no plans to put anything into production that's marginal.


what caps are you using for your bootstrap supplies?


Box polyester film. You gonna say I should be using ceramic ?

Graham

not until I read the datasheet. But I would caution against Z5U/Y5V,
they are a path to temperature-related auto-self-destruct features.

No chance of me using shitty dielectrics !

make sure there isnt too much ESR, the capacitance is stable with
voltage & temperature, its happy with the peak current (maybe as high as
Vboost/Rgate) and there is fuck all inductance in the gatedrive loops.

Tried to minimise the gate drive tracks and indeed all fast tracks but I reckon
my layout man could have done a little better.

it can be a good idea with bootstrap supplies to use a couple of volts
more than the lower supply, because of the load-dependant voltage drop
across the lower switch (and, of course, the diode).

Hmmm........ typical bootstrap operation results in a diode drop plus device Vce
or Vds drop.

I'm erring towards local bootstrap supply now.

I presume your diode is a fast HV diode.

MUR 460 in parallel with the switch. ~50ns

I was once involved on the periphery with a cost-down of a small AC
drive, 1% to 10% parts, that sort of thing. Changing the charge-pump
gatedrive 100nF rectangular blue plastic film caps to cheap ceramic ones
resulted in a 100% fatality rate on all 10 prototype units, about 20
minutes into a thermal test. That change never made it to production.

I'm not gonna use cheap bits for this !


Regds, Graham

 

[Winfield Hill]

Pooh Bear wrote...

Winfield Hill wrote:

Pooh Bear wrote...

I'm using an IR2110 high and low side gate driver in a smps that
I mentioned some time back in the group under the thread 'should
I use a SG3525'.

I've had some 'odd' power device failures that I didn't expect in
entirely benign situations, such as the half bridge output simply
driving the primary of my transformer.

Device failure meaning damaged components, or meaning, a FET that
didn't do what you expected under a certain circumstance, but yet
wasn't actually damaged.

Device going short. Either just the high side device or both. I've
established to my satisfaction that there are 2 failure scenarios.

1. Ramping the voltage down on the variac (quickly). E.g. after I've
been testing @ line voltage. There's a bzzt and the high side device
goes short. I suspect a mixture of the UVLO mismatches and possible
'mis-track' of the main bus and supervisory rail. Doesn't happen if I
ramp the volts down slowly (or so it seems). Hence my thoughts about
the droop of the rails.

2. Both devices fail - this first happened after I'd been running the
transformer primary only for about 1/2 hour just to establish likely
practical core temp rise. It ran fine for ages - I turned my back to
do some calcs and the thing bzzt'ed at me. It was still working so I
thought I was hearing things! Did it terminally 3 mins later. Looking
closely I'm seeing the high side drive terminate prematurely under
circumstances I have yet to exactly determine the cause of. Maybe
insufficient bootstrap C? Was looking at this last thing today.
Will investigate further tomorrow wrt all the drive waveforms.

I realised that it happened a couple of times when I wound down the
input volts (I'm supplying the board via a variac and isolating
transfomer for development).

The IR2110 has undervoltage lockout. Fine! I checked it carefully
today and the UVLO for the low side and high side aren't linked.
Indeed a careful look at the data sheet does indeed show that
there's no connection. The low side drive activates at about 8V
and the high side about a volt higher.

IR has to separately detect the low-side and high-side voltages,
because the latter is the voltage across the flying capacitor.

True. I wish they'd OR the UVLOs though.

The mismatch you observed sounds good: the high side should stop
working well before the low side, thereby preventing any shoothro
current, which could be disasterous.

I'd prefer it if both terminated together !

Needless to say this creates 'issues'!
Anyone here used this part and care to comment?

I think you're going down the wrong track. If a FET fails to turn
on because of an activated UV lockout, this should not be the cause
of a MOSFET short. What would be the mechanism for that? Yes, the
desired switching function is interrupted, but benignly so.

I suspect you have a different common and deadly problem, namely
fast MOSFET source-voltage spikes from reverse-recovery-time
snapoff. This occurs if the FET's intrinsic body diode conducts,
and the ns spikes can damage the FET's delicate gate insulation.
V = L di/dt where L is your FET's source-lead inductance, and the
di/dt is high because dt can be under 1ns during t_rr snapoff.

The FET diode's will clamp the flyback from your transformer's
leakage inductance if during the delay after the other FET turns
off the flyback voltage swing is high enough. This clamping with
the resultant spike will happen if you have an inadequate snubbing
network across the FETs to prevent the flyback from swinging across
your entire raw dc voltage supply. The snubber network can simply
be a drain-source capacitor, to absorb the leakage-inductance energy
or it can be more complex. But whatever your choice, don't ever let
the FET's body diodes conduct!!!

Note, the transformer's leakage-inductance energy is proportional
to current, which means it's flyback effect is minimal under no
load, and worst under full load. Carefully examine your switching
waveforms to see how they change as you increase the load on the
transformer output.

Let's hear about your issues.

Well, the devices failing for one !

The 2110 UVLO is sensitive to line ripple. It appears to result in
a effect that's like weird duty cycles when it's hovering around the
UVLO threshold(s).

As I said, while disconcerting, it shouldn't take out MOSFETs.

BTW, did you tell us what FETs you're using? And tell us more
about your transformer and the operating voltages and currents.
Did you measure the transformer's leakage inductance?

BTW, recognizing the need for low-voltage protection, and the need
for a benign response to low-voltage conditions, you could easily
add a comparator operating at lower voltages, plus shutoff gates
managing the IR2110's three logic inputs, per your special needs.

That's what I imagine I may indeed have to do. Or I can shutdown the
3525.

Was curious if anyone had experienced similar when using the 2110.

Cheers, Graham

p.s. I now understand why smps design has always had a reputation for
being 'tricky'. Also why when quizzed about them - some vendors go all
shy when talking about the reliability of smps versions of their audio
amps! I have no plans to put anything into production that's marginal.

It takes an experienced designer to make a reliable switcher.


--
Thanks,
- Win

 

[Terry Given]

Pooh Bear wrote:

Terry Given wrote:


Pooh Bear wrote:

Terry Given wrote:


Pooh Bear wrote:


Winfield Hill wrote:


Pooh Bear wrote...


I'm using an IR2110 high and low side gate driver in a smps that
I mentioned some time back in the group under the thread 'should
I use a SG3525'.

I've had some 'odd' power device failures that I didn't expect in
entirely benign situations, such as the half bridge output simply
driving the primary of my transformer.

Device failure meaning damaged components, or meaning, a FET that
didn't do what you expected under a certain circumstance, but yet
wasn't actually damaged.


Device going short. Either just the high side device or both. I've
established to my satisfaction that there are 2 failure scenarios.

1. Ramping the voltage down on the variac ( quickly ) . E.g. after
I've been testing @ line voltage. There's a bzzt and the high side device
goes short. I suspect a mixture of the UVLO mismatches and possible
'mis-track' of the main bus and supervisory rail. Doesn't happen if I
ramp the volts down slowly ( or so it seems ). Hence my thoughts about
the droop of the rails.

2. Both devices fail - this first happened after I'd been running the
transformer primary only for about 1/2 hour just to establish likely
practical core temp rise. It ran fine for ages - I turned my back to do
some calcs and the thing bzzt'ed at me. It was still working so I thought
I was hearing things ! Did it terminally 3 mins later. Looking closely
I'm seeing the high side drive terminate prematurely under circumstances
I have yet to exactly determine the cause of. Maybe insufficient
bootstrap C ? Was looking at this last thing today. Will investigate
further tomorrow wrt all the drive waveforms.



I realised that it happened a couple of times when I wound down the
input volts ( I'm supplying the board via a variac and isolating
transfomer for development ).

The IR2110 has undervoltage lockout. Fine! I checked it carefully
today and the UVLO for the low side and high side aren't linked.
Indeed a careful look at the data sheet does indeed show that
there's no connection. The low side drive activates at about 8V
and the high side about a volt higher.

IR has to separately detect the low-side and high-side voltages,
because the latter is the voltage across the flying capacitor.


True. I wish they'd OR the UVLOs though.



The mismatch you observed sounds good: the high side should stop
working well before the low side, thereby preventing any shoothro
current, which could be disasterous.


I'd prefer it if both terminated together !



Needless to say this creates 'issues'!
Anyone here used this part and care to comment?

Let's hear about your issues.


Well, the devices failing for one !

The 2110 UVLO is sensitive to line ripple. It appears to result in a
effect that's like weird duty cycles when it's hovering around the UVLO
threshold(s).




BTW, recognizing the need for low-voltage protection, and the need
for a benign response to low-voltage conditions, you could easily
add a comparator operating at lower voltages, plus shutoff gates
managing the IR2110's three logic inputs, per your special needs.


That's what I imagine I may indeed have to do. Or I can shutdown the
3525.

Was curious if anyone had experienced similar when using the 2110.

Cheers, Graham

p.s. I now understand why smps design has always had a reputation for
being 'tricky'. Also why when quizzed about them - some vendors go all
shy when talking about the reliability of smps versions of their audio
amps ! I have no plans to put anything into production that's marginal.


what caps are you using for your bootstrap supplies?


Box polyester film. You gonna say I should be using ceramic ?

Graham

not until I read the datasheet. But I would caution against Z5U/Y5V,
they are a path to temperature-related auto-self-destruct features.


No chance of me using shitty dielectrics !

didnt think so. I should have replaced "But" with "if you said ceramic"

I asked this question a while back, but no-one rose to the challenge: is
there *any* application in which its worth using Z5U/Y5V? every time I
check, the voltage and temperature coefficients mean an X7R cap provides
far more capacitance in the same footprint, at the same cost.

make sure there isnt too much ESR, the capacitance is stable with
voltage & temperature, its happy with the peak current (maybe as high as
Vboost/Rgate) and there is fuck all inductance in the gatedrive loops.


Tried to minimise the gate drive tracks and indeed all fast tracks but I reckon
my layout man could have done a little better.

I do the layouts myself. far easier.

it can be a good idea with bootstrap supplies to use a couple of volts
more than the lower supply, because of the load-dependant voltage drop
across the lower switch (and, of course, the diode).


Hmmm........ typical bootstrap operation results in a diode drop plus device Vce
or Vds drop.

yep. dont forget to check your diode forward recovery time as well. that
can bite a chunk off your supply.

I had to solve a non-regulating flyback supply once (with TL431 + opto
feedback) that in large part was due to the use of a seriously shit
diode for a rectifier (I forget which diode, almost 1N400x type, Trr was
a us or two). I had worked on some of the designers other stuff, didnt
recognise the part number so just assumed he would use a suitable part.
there were other serious problems too, but the diode made me waste a few
days. both forward and reverse recovery were problematic.

It became a production problem because the output voltage just happened
to be right (ish, calibrate on test) when fed from 115Vac. problem was
it was a universal ac input ups battery charger, and batteries started
dying.....

I'm erring towards local bootstrap supply now.


I presume your diode is a fast HV diode.


MUR 460 in parallel with the switch. ~50ns

que? bootstrap diode (havent read IR2110 data sheet, it may include
them) from -Vdc bias supply to flating supply, cap to E, current
flows when lower switch turns on.

I was once involved on the periphery with a cost-down of a small AC
drive, 1% to 10% parts, that sort of thing. Changing the charge-pump
gatedrive 100nF rectangular blue plastic film caps to cheap ceramic ones
resulted in a 100% fatality rate on all 10 prototype units, about 20
minutes into a thermal test. That change never made it to production.


I'm not gonna use cheap bits for this !

I later designed the gatedrive for the replacement product, used a
similar idea but with a much better gatedrive circuit, and X7R caps. It
was then that I really learned my dielectrics, when a supply drooped
about 20x faster than it ought to (20V bias on 25V Z5U cap). At that
point I also answered the "why did the last product die" question, which
was never really investigated at the time - those involved simply went
"ok, dont change them" and moved on. We did a quick test with the old
product using X7R caps, and it worked like a charm.

Regds, Graham

Cheers
Terry