wart overvoltage protection...

[John Larkin]

On Sat, 1 Oct 2022 19:28:19 +1000, Sylvia Else <sylvia@email.invalid>
wrote:

On 01-Oct-22 6:14 am, John Larkin wrote:
We make a gadget that\'s powered by a 12 volt wart, and sometimes a
user applies 24 and blows one up.

We have a polyfuse and a 12 volt TVS and they sometimes fry the TVS.
It\'s posssible that most any useful polyfuse+TVS combo can be teased
to destruction.

I think Phil H mentioned some gadget, a polyzorb or something, that
would be better. I can\'t find it.

We might fine-tune the polyfuse+TVS, or maybe go polyfuse and SCR
crowbar, or something.

This is all entangled with parts availabity. Ideally the box would
just work from 12 or 24, but that has separate complications.

We once used a TI electronic fuse IC, but it liked to blow up.


Crowbar circuit?

Sylvia.

That would work, with a polyfuse and a big diode for reverse voltage.
I can get a dpak SCR that will handle 50 amps for a while.

Just a zener to the gate of an SCR is probably OK for modest
short-circuit currents. Big crowbars need a fast gate driver, diac or
something.

 

[Jeroen Belleman]

On 2022-10-01 18:28, John Larkin wrote:

On Fri, 30 Sep 2022 19:08:54 -0700 (PDT), whit3rd <whit3rd@gmail.com
wrote:

On Friday, September 30, 2022 at 1:14:16 PM UTC-7, John Larkin wrote:
We make a gadget that\'s powered by a 12 volt wart, and sometimes a
user applies 24 and blows one up.

So, is the power inlet clearly laser-burn-marked
as 12V center positive? And is the supplied power
brick similarly clearly labeled?

Yes, but in a tangle of wart cords, people sometimes make mistakes. It
is prudent for instruments to be rugged. All our new stuff uses +24.

It\'s unfortunate that barrel connectors weren\'t keyed for voltages. Or
even marked.

Sigh! Many connectors, coax or otherwise, seem designed to maximize
trouble.

Jeroen Belleman

 

[Ed Lee]

On Saturday, October 1, 2022 at 9:33:19 AM UTC-7, John Larkin wrote:

On Sat, 1 Oct 2022 19:28:19 +1000, Sylvia Else <syl...@email.invalid
wrote:
On 01-Oct-22 6:14 am, John Larkin wrote:
We make a gadget that\'s powered by a 12 volt wart, and sometimes a
user applies 24 and blows one up.

We have a polyfuse and a 12 volt TVS and they sometimes fry the TVS.
It\'s posssible that most any useful polyfuse+TVS combo can be teased
to destruction.

I think Phil H mentioned some gadget, a polyzorb or something, that
would be better. I can\'t find it.

We might fine-tune the polyfuse+TVS, or maybe go polyfuse and SCR
crowbar, or something.

This is all entangled with parts availabity. Ideally the box would
just work from 12 or 24, but that has separate complications.

We once used a TI electronic fuse IC, but it liked to blow up.


Crowbar circuit?

Sylvia.
That would work, with a polyfuse and a big diode for reverse voltage.
I can get a dpak SCR that will handle 50 amps for a while.

Just a zener to the gate of an SCR is probably OK for modest
short-circuit currents. Big crowbars need a fast gate driver, diac or
something.

Does your 24V supply have short circuit protection? If so, i would use TL431 and IGBT to shunt it. RJP30E2: 200A peak in TO-220 package.

 

[Phil Hobbs]

John Larkin wrote:

On Sat, 1 Oct 2022 04:39:15 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin wrote:
On Fri, 30 Sep 2022 17:53:05 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

Martin Rid wrote:
John Larkin <jlarkin@highland_atwork_technology.com> Wrote in
message:r
We make a gadget that\'s powered by a 12 volt wart, and
sometimes auser applies 24 and blows one up.We have a polyfuse
and a 12 volt TVS and they sometimes fry the TVS.It\'s posssible
that most any useful polyfuse+TVS combo can be teasedto
destruction.I think Phil H mentioned some gadget, a polyzorb or
something, thatwould be better. I can\'t find it.We might
fine-tune the polyfuse+TVS, or maybe go polyfuse and
SCRcrowbar, or something.This is all entangled with parts
availabity. Ideally the box wouldjust work from 12 or 24, but
that has separate complications.We once used a TI electronic
fuse IC, but it liked to blow up.

Have some series resistance to work at 24v, and switch the
resistance out if the voltage drops er stays under 13v?

Cheers

Or maybe an LM393 and a PFET.


That\'s an idea, a pfet current limiter that entirely shuts off if
the input goes above maybe 14 volts. At maybe a 500 mA, fet
dissipation would be OK.

Someone here suggested making our own polyzen sort of thing, but I
suspect we couldn\'t successfully transfer the heat from the TVS to
the polyfuse fast enough.

An SMB12A TVS is rated for peak power, 600 watts, but not rated for
DC power. 5 watts maybe with big pads?


I\'ve occasionally looked at the specialized OVP/power limiter chips, but
they tend to cost $$$, and for my purposes they don\'t look as good as
doing the limiting locally. (If I were controlling big motors or
something, that might be a different matter.)

At various times I\'ve used LP2951s to make small amounts of +3.3V
directly from the wall wart to run startup circuitry and so forth. An
LM393 is a 358 with different metal--the input devices are lateral PNPs,
and so will take a lot of positive voltage regardless of the supplies.

A few microseconds of delay is no problem for that job.


We tried the TPS26600 \"hot swap efuse\" and it liked to blow up. It\'s a
horrible complex expensive power-pad thing.

I might just start with an LM2576 and switch down to maybe +7, and
work from there. That will work from 10 to 40 volts. 2576 is an old,
slow, klunky, non-synch switcher that\'s available. Wonderful part.

I use a fair number of the 150-kHz ones--they\'re still nice and slow and
stupid, but use smaller and cheaper inductors.

We could assume the dpak but we might lead-form the TO220 version in a
pinch. TO220s seem to be available. Maybe nobody wants them.

The guys wanted to use the LT8603 quad switcher but we tested it and
it makes nasty 400 MHz ringy things at the switching edges. In a
\"silent switcher\" !

Yeah, and the predominant frequency changes depending on the trace
lengths you\'re got attached. We had one horrible failure on a small
board with three switchers on it--two worked fine, but the LMR23630 we
were using to make -12 from +13 produced a VHF-fest like yours.

One one trace it was mostly near 180 MHz, but on another it was 125ish.
We gave up.

We used the LTM8078 dual BGA module and had a similar problem; it
sprayed huge RF bursts all over the board. Probably the same
technology. The nasties are on both edges, so it\'s just switching too
fast, not an SRD effect.

https://www.dropbox.com/sh/ok9tn7gfgobv2nh/AADb7Muju5jRki93byL8J-_sa?dl=0

Had to redesign the big control board.

Yecch.

Cheers

Phil Hobbs



--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Phil Hobbs]

piglet wrote:

On 30/09/2022 22:53, Phil Hobbs wrote:
Martin Rid wrote:
John Larkin <jlarkin@highland_atwork_technology.com> Wrote in message:r
We make a gadget that\'s powered by a 12 volt wart, and sometimes
auser applies 24 and blows one up.We have a polyfuse and a 12 volt
TVS and they sometimes fry the TVS.It\'s posssible that most any
useful polyfuse+TVS combo can be teasedto destruction.I think Phil H
mentioned some gadget, a polyzorb or something, thatwould be better.
I can\'t find it.We might fine-tune the polyfuse+TVS, or maybe go
polyfuse and SCRcrowbar, or something.This is all entangled with
parts availabity. Ideally the box wouldjust work from 12 or 24, but
that has separate complications.We once used a TI electronic fuse
IC, but it liked to blow up.

Have some series resistance to work at 24v, and switch the
  resistance out if the voltage drops er stays under
  13v?

Cheers

Or maybe an LM393 and a PFET.

Cheers

Phil Hobbs


A few years back the late Jim Thompson of this very bazaar posted a
circuit using two TL431 and two pmos fets to provide series undervolt,
overvolt and reverse polarity protection. All jelly bean very low cost
parts in unlimited supply?

piglet

I mirror his website at
<https://electrooptical.net/News/mirror-of-wwwanalog-innovationscom-jim-thompsons-site/>.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Phil Hobbs]

Phil Hobbs wrote:

piglet wrote:
On 30/09/2022 22:53, Phil Hobbs wrote:
Martin Rid wrote:
John Larkin <jlarkin@highland_atwork_technology.com> Wrote in message:r
We make a gadget that\'s powered by a 12 volt wart, and sometimes
auser applies 24 and blows one up.We have a polyfuse and a 12 volt
TVS and they sometimes fry the TVS.It\'s posssible that most any
useful polyfuse+TVS combo can be teasedto destruction.I think Phil
H mentioned some gadget, a polyzorb or something, thatwould be
better. I can\'t find it.We might fine-tune the polyfuse+TVS, or
maybe go polyfuse and SCRcrowbar, or something.This is all
entangled with parts availabity. Ideally the box wouldjust work
from 12 or 24, but that has separate complications.We once used a
TI electronic fuse IC, but it liked to blow up.

Have some series resistance to work at 24v, and switch the
  resistance out if the voltage drops er stays under
  13v?

Cheers

Or maybe an LM393 and a PFET.

Cheers

Phil Hobbs


A few years back the late Jim Thompson of this very bazaar posted a
circuit using two TL431 and two pmos fets to provide series undervolt,
overvolt and reverse polarity protection. All jelly bean very low cost
parts in unlimited supply?

piglet


I mirror his website at
https://electrooptical.net/News/mirror-of-wwwanalog-innovationscom-jim-thompsons-site/>.

I think the circuit you mean is at
<https://electrooptical.net/static/oldsite/www.analog-innovations.com/SED/OverAndReverseVoltageProtection.pdf>.

One could maybe save the BJT by using an LM4041 instead, but it would
depend on the threshold voltage of the second FET.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[John Larkin]

On Sat, 1 Oct 2022 14:26:17 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin wrote:
On Sat, 1 Oct 2022 04:39:15 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin wrote:
On Fri, 30 Sep 2022 17:53:05 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

Martin Rid wrote:
John Larkin <jlarkin@highland_atwork_technology.com> Wrote in
message:r
We make a gadget that\'s powered by a 12 volt wart, and
sometimes auser applies 24 and blows one up.We have a polyfuse
and a 12 volt TVS and they sometimes fry the TVS.It\'s posssible
that most any useful polyfuse+TVS combo can be teasedto
destruction.I think Phil H mentioned some gadget, a polyzorb or
something, thatwould be better. I can\'t find it.We might
fine-tune the polyfuse+TVS, or maybe go polyfuse and
SCRcrowbar, or something.This is all entangled with parts
availabity. Ideally the box wouldjust work from 12 or 24, but
that has separate complications.We once used a TI electronic
fuse IC, but it liked to blow up.

Have some series resistance to work at 24v, and switch the
resistance out if the voltage drops er stays under 13v?

Cheers

Or maybe an LM393 and a PFET.


That\'s an idea, a pfet current limiter that entirely shuts off if
the input goes above maybe 14 volts. At maybe a 500 mA, fet
dissipation would be OK.

Someone here suggested making our own polyzen sort of thing, but I
suspect we couldn\'t successfully transfer the heat from the TVS to
the polyfuse fast enough.

An SMB12A TVS is rated for peak power, 600 watts, but not rated for
DC power. 5 watts maybe with big pads?


I\'ve occasionally looked at the specialized OVP/power limiter chips, but
they tend to cost $$$, and for my purposes they don\'t look as good as
doing the limiting locally. (If I were controlling big motors or
something, that might be a different matter.)

At various times I\'ve used LP2951s to make small amounts of +3.3V
directly from the wall wart to run startup circuitry and so forth. An
LM393 is a 358 with different metal--the input devices are lateral PNPs,
and so will take a lot of positive voltage regardless of the supplies.

A few microseconds of delay is no problem for that job.


We tried the TPS26600 \"hot swap efuse\" and it liked to blow up. It\'s a
horrible complex expensive power-pad thing.

I might just start with an LM2576 and switch down to maybe +7, and
work from there. That will work from 10 to 40 volts. 2576 is an old,
slow, klunky, non-synch switcher that\'s available. Wonderful part.

I use a fair number of the 150-kHz ones--they\'re still nice and slow and
stupid, but use smaller and cheaper inductors.


We could assume the dpak but we might lead-form the TO220 version in a
pinch. TO220s seem to be available. Maybe nobody wants them.

The guys wanted to use the LT8603 quad switcher but we tested it and
it makes nasty 400 MHz ringy things at the switching edges. In a
\"silent switcher\" !

Yeah, and the predominant frequency changes depending on the trace
lengths you\'re got attached. We had one horrible failure on a small
board with three switchers on it--two worked fine, but the LMR23630 we
were using to make -12 from +13 produced a VHF-fest like yours.

One one trace it was mostly near 180 MHz, but on another it was 125ish.
We gave up.

We used the LTM8078 dual BGA module and had a similar problem; it
sprayed huge RF bursts all over the board. Probably the same
technology. The nasties are on both edges, so it\'s just switching too
fast, not an SRD effect.

https://www.dropbox.com/sh/ok9tn7gfgobv2nh/AADb7Muju5jRki93byL8J-_sa?dl=0

Had to redesign the big control board.

Yecch.

Cheers

Phil Hobbs

This is one of my favorite waveforms:

https://www.dropbox.com/s/wxorqqhj5u899bc/LM3102_SwitcherRise.JPG?raw=1

I think the scope limited the rise time.

 

[John Larkin]

On Sat, 1 Oct 2022 10:48:28 -0700 (PDT), Ed Lee
<edward.ming.lee@gmail.com> wrote:

On Saturday, October 1, 2022 at 9:33:19 AM UTC-7, John Larkin wrote:
On Sat, 1 Oct 2022 19:28:19 +1000, Sylvia Else <syl...@email.invalid
wrote:
On 01-Oct-22 6:14 am, John Larkin wrote:
We make a gadget that\'s powered by a 12 volt wart, and sometimes a
user applies 24 and blows one up.

We have a polyfuse and a 12 volt TVS and they sometimes fry the TVS.
It\'s posssible that most any useful polyfuse+TVS combo can be teased
to destruction.

I think Phil H mentioned some gadget, a polyzorb or something, that
would be better. I can\'t find it.

We might fine-tune the polyfuse+TVS, or maybe go polyfuse and SCR
crowbar, or something.

This is all entangled with parts availabity. Ideally the box would
just work from 12 or 24, but that has separate complications.

We once used a TI electronic fuse IC, but it liked to blow up.


Crowbar circuit?

Sylvia.
That would work, with a polyfuse and a big diode for reverse voltage.
I can get a dpak SCR that will handle 50 amps for a while.

Just a zener to the gate of an SCR is probably OK for modest
short-circuit currents. Big crowbars need a fast gate driver, diac or
something.

Does your 24V supply have short circuit protection? If so, i would use TL431 and IGBT to shunt it. RJP30E2: 200A peak in TO-220 package.

We ship this particular box with a small 12 volt wart, but a customer
might use some other supply in a system application. They do sometimes
apply 24 and blow up the TVS.

The ideal product handles up to +-48 at zero source impedance and
behaves gracefully for any combination of brownouts and
fumble-fingers.

 

[Ed Lee]

On Saturday, October 1, 2022 at 12:23:38 PM UTC-7, John Larkin wrote:

On Sat, 1 Oct 2022 10:48:28 -0700 (PDT), Ed Lee
edward....@gmail.com> wrote:

On Saturday, October 1, 2022 at 9:33:19 AM UTC-7, John Larkin wrote:
On Sat, 1 Oct 2022 19:28:19 +1000, Sylvia Else <syl...@email.invalid
wrote:
On 01-Oct-22 6:14 am, John Larkin wrote:
We make a gadget that\'s powered by a 12 volt wart, and sometimes a
user applies 24 and blows one up.

We have a polyfuse and a 12 volt TVS and they sometimes fry the TVS.
It\'s posssible that most any useful polyfuse+TVS combo can be teased
to destruction.

I think Phil H mentioned some gadget, a polyzorb or something, that
would be better. I can\'t find it.

We might fine-tune the polyfuse+TVS, or maybe go polyfuse and SCR
crowbar, or something.

This is all entangled with parts availabity. Ideally the box would
just work from 12 or 24, but that has separate complications.

We once used a TI electronic fuse IC, but it liked to blow up.


Crowbar circuit?

Sylvia.
That would work, with a polyfuse and a big diode for reverse voltage.
I can get a dpak SCR that will handle 50 amps for a while.

Just a zener to the gate of an SCR is probably OK for modest
short-circuit currents. Big crowbars need a fast gate driver, diac or
something.

Does your 24V supply have short circuit protection? If so, i would use TL431 and IGBT to shunt it. RJP30E2: 200A peak in TO-220 package.
We ship this particular box with a small 12 volt wart, but a customer
might use some other supply in a system application. They do sometimes
apply 24 and blow up the TVS.

The ideal product handles up to +-48 at zero source impedance and
behaves gracefully for any combination of brownouts and
fumble-fingers.

Any decent power supply should be able to handle half-short circuit. Put in a big heat sink and it might just work with 24V supply, shunt to 12V.

 

[Lasse Langwadt Christensen]

lørdag den 1. oktober 2022 kl. 21.23.38 UTC+2 skrev John Larkin:

On Sat, 1 Oct 2022 10:48:28 -0700 (PDT), Ed Lee
edward....@gmail.com> wrote:

On Saturday, October 1, 2022 at 9:33:19 AM UTC-7, John Larkin wrote:
On Sat, 1 Oct 2022 19:28:19 +1000, Sylvia Else <syl...@email.invalid
wrote:
On 01-Oct-22 6:14 am, John Larkin wrote:
We make a gadget that\'s powered by a 12 volt wart, and sometimes a
user applies 24 and blows one up.

We have a polyfuse and a 12 volt TVS and they sometimes fry the TVS..
It\'s posssible that most any useful polyfuse+TVS combo can be teased
to destruction.

I think Phil H mentioned some gadget, a polyzorb or something, that
would be better. I can\'t find it.

We might fine-tune the polyfuse+TVS, or maybe go polyfuse and SCR
crowbar, or something.

This is all entangled with parts availabity. Ideally the box would
just work from 12 or 24, but that has separate complications.

We once used a TI electronic fuse IC, but it liked to blow up.


Crowbar circuit?

Sylvia.
That would work, with a polyfuse and a big diode for reverse voltage.
I can get a dpak SCR that will handle 50 amps for a while.

Just a zener to the gate of an SCR is probably OK for modest
short-circuit currents. Big crowbars need a fast gate driver, diac or
something.

Does your 24V supply have short circuit protection? If so, i would use TL431 and IGBT to shunt it. RJP30E2: 200A peak in TO-220 package.
We ship this particular box with a small 12 volt wart, but a customer
might use some other supply in a system application. They do sometimes
apply 24 and blow up the TVS.

The ideal product handles up to +-48 at zero source impedance and
behaves gracefully for any combination of brownouts and
fumble-fingers.

TPS2400 add PFET for reverse voltage protection

 

[Ed Lee]

On Saturday, October 1, 2022 at 3:01:24 PM UTC-7, lang...@fonz.dk wrote:

lørdag den 1. oktober 2022 kl. 21.23.38 UTC+2 skrev John Larkin:
On Sat, 1 Oct 2022 10:48:28 -0700 (PDT), Ed Lee
edward....@gmail.com> wrote:

On Saturday, October 1, 2022 at 9:33:19 AM UTC-7, John Larkin wrote:
On Sat, 1 Oct 2022 19:28:19 +1000, Sylvia Else <syl...@email.invalid
wrote:
On 01-Oct-22 6:14 am, John Larkin wrote:
We make a gadget that\'s powered by a 12 volt wart, and sometimes a
user applies 24 and blows one up.

We have a polyfuse and a 12 volt TVS and they sometimes fry the TVS.
It\'s posssible that most any useful polyfuse+TVS combo can be teased
to destruction.

I think Phil H mentioned some gadget, a polyzorb or something, that
would be better. I can\'t find it.

We might fine-tune the polyfuse+TVS, or maybe go polyfuse and SCR
crowbar, or something.

This is all entangled with parts availabity. Ideally the box would
just work from 12 or 24, but that has separate complications.

We once used a TI electronic fuse IC, but it liked to blow up.


Crowbar circuit?

Sylvia.
That would work, with a polyfuse and a big diode for reverse voltage..
I can get a dpak SCR that will handle 50 amps for a while.

Just a zener to the gate of an SCR is probably OK for modest
short-circuit currents. Big crowbars need a fast gate driver, diac or
something.

Does your 24V supply have short circuit protection? If so, i would use TL431 and IGBT to shunt it. RJP30E2: 200A peak in TO-220 package.
We ship this particular box with a small 12 volt wart, but a customer
might use some other supply in a system application. They do sometimes
apply 24 and blow up the TVS.

The ideal product handles up to +-48 at zero source impedance and
behaves gracefully for any combination of brownouts and
fumble-fingers.
TPS2400 add PFET for reverse voltage protection

TPS2400 has Vin max of 6.8V. TL431 can go up to 30V.

 

[Lasse Langwadt Christensen]

søndag den 2. oktober 2022 kl. 01.09.37 UTC+2 skrev Ed Lee:

On Saturday, October 1, 2022 at 3:01:24 PM UTC-7, lang...@fonz.dk wrote:
lørdag den 1. oktober 2022 kl. 21.23.38 UTC+2 skrev John Larkin:
On Sat, 1 Oct 2022 10:48:28 -0700 (PDT), Ed Lee
edward....@gmail.com> wrote:

On Saturday, October 1, 2022 at 9:33:19 AM UTC-7, John Larkin wrote:
On Sat, 1 Oct 2022 19:28:19 +1000, Sylvia Else <syl...@email.invalid
wrote:
On 01-Oct-22 6:14 am, John Larkin wrote:
We make a gadget that\'s powered by a 12 volt wart, and sometimes a
user applies 24 and blows one up.

We have a polyfuse and a 12 volt TVS and they sometimes fry the TVS.
It\'s posssible that most any useful polyfuse+TVS combo can be teased
to destruction.

I think Phil H mentioned some gadget, a polyzorb or something, that
would be better. I can\'t find it.

We might fine-tune the polyfuse+TVS, or maybe go polyfuse and SCR
crowbar, or something.

This is all entangled with parts availabity. Ideally the box would
just work from 12 or 24, but that has separate complications.

We once used a TI electronic fuse IC, but it liked to blow up.


Crowbar circuit?

Sylvia.
That would work, with a polyfuse and a big diode for reverse voltage.
I can get a dpak SCR that will handle 50 amps for a while.

Just a zener to the gate of an SCR is probably OK for modest
short-circuit currents. Big crowbars need a fast gate driver, diac or
something.

Does your 24V supply have short circuit protection? If so, i would use TL431 and IGBT to shunt it. RJP30E2: 200A peak in TO-220 package.
We ship this particular box with a small 12 volt wart, but a customer
might use some other supply in a system application. They do sometimes
apply 24 and blow up the TVS.

The ideal product handles up to +-48 at zero source impedance and
behaves gracefully for any combination of brownouts and
fumble-fingers.
TPS2400 add PFET for reverse voltage protection
TPS2400 has Vin max of 6.8V. TL431 can go up to 30V.

https://www.ti.com/lit/an/slva163/slva163.pdf

 

[Mike Monett VE3BTI]

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

I think the circuit you mean is at
https://electrooptical.net/static/oldsite/www.analog-innovations.com/SED
/OverAndReverseVoltageProtection.pdf>.

One could maybe save the BJT by using an LM4041 instead, but it would
depend on the threshold voltage of the second FET.

Cheers

Phil Hobbs

Resistor R3 of 100 Ohms may be a typo. This requires the TL431 to sink 246
mA at an input of 30V, which is typical of an unregulated 24V wall wart
with little or no load. This is well over the limit of 100 mA of the TL431.
Changing R3 to 1K gives a much more reasonable 27.8 mA max at 30V.

Also, the GS voltage of M1 limits the maximum input voltage to +-8V. I know
JL has reached 70V or so without damage, but I tend to be sceptical of
exceeding voltage ratings. However, the input of 24V that JL asked for far
exceeds this limit.

IRLML6401 datasheet
blob:https://octopart.com/ae343064-0e3c-4114-ba6c-a0e939789b63




--
MRM

 

[Lasse Langwadt Christensen]

søndag den 2. oktober 2022 kl. 01.40.48 UTC+2 skrev Mike Monett VE3BTI:

Phil Hobbs <pcdhSpamM...@electrooptical.net> wrote:

I think the circuit you mean is at
https://electrooptical.net/static/oldsite/www.analog-innovations.com/SED
/OverAndReverseVoltageProtection.pdf>.

One could maybe save the BJT by using an LM4041 instead, but it would
depend on the threshold voltage of the second FET.

Cheers

Phil Hobbs
Resistor R3 of 100 Ohms may be a typo. This requires the TL431 to sink 246
mA at an input of 30V, which is typical of an unregulated 24V wall wart
with little or no load. This is well over the limit of 100 mA of the TL431.
Changing R3 to 1K gives a much more reasonable 27.8 mA max at 30V.

Also, the GS voltage of M1 limits the maximum input voltage to +-8V. I know
JL has reached 70V or so without damage, but I tend to be sceptical of
exceeding voltage ratings. However, the input of 24V that JL asked for far
exceeds this limit.

the gates just need a zener and a series resistor

 

[Sylvia Else]

On 02-Oct-22 3:33 am, John Larkin wrote:

On Sat, 1 Oct 2022 19:28:19 +1000, Sylvia Else <sylvia@email.invalid
wrote:

On 01-Oct-22 6:14 am, John Larkin wrote:
We make a gadget that\'s powered by a 12 volt wart, and sometimes a
user applies 24 and blows one up.

We have a polyfuse and a 12 volt TVS and they sometimes fry the TVS.
It\'s posssible that most any useful polyfuse+TVS combo can be teased
to destruction.

I think Phil H mentioned some gadget, a polyzorb or something, that
would be better. I can\'t find it.

We might fine-tune the polyfuse+TVS, or maybe go polyfuse and SCR
crowbar, or something.

This is all entangled with parts availabity. Ideally the box would
just work from 12 or 24, but that has separate complications.

We once used a TI electronic fuse IC, but it liked to blow up.


Crowbar circuit?

Sylvia.

That would work, with a polyfuse and a big diode for reverse voltage.
I can get a dpak SCR that will handle 50 amps for a while.

Just a zener to the gate of an SCR is probably OK for modest
short-circuit currents. Big crowbars need a fast gate driver, diac or
something.

I thought the usual go was to short circuit the current long enough to
blow a conventional fuse. Of course, you have to handle the case where
the PS cannot supply enough current to blow the fuse, but sits there and
fizzles instead.

Or is even fuse replacement beyond the customer\'s competence? Would you
need to confiscate everything conductive and fuse sized first?

Sylvia.

 

[Jan Panteltje]

On a sunny day (Sat, 01 Oct 2022 12:23:27 -0700) it happened John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote in
<qk4hjhtnek9nievrbc26g6g2oip5mbpal0@4ax.com>:

The ideal product handles up to +-48 at zero source impedance and
behaves gracefully for any combination of brownouts and
fumble-fingers.

From datasheet quote:
LM2576/LM2576HV Series
SIMPLE SWITCHER ® 3A Step-Down Voltage Regulator
General Description Features
The LM2576 series of regulators are monolithic integrated n 3.3V, 5V, 12V, 15V, and adjustable output versions
circuits that provide all the active functions for a step-down n Adjustable version output voltage range,
(buck) switching regulator, capable of driving 3A load with 1.23V to 37V (57V for HV version) ± 4% max over
excellent line and load regulation. These devices are avail- line and load conditions
able in fixed output voltages of 3.3V, 5V, 12V, 15V, and an n Guaranteed 3A output current
adjustable output version. n Wide input voltage range, 40V up to 60V for
Requiring a minimum number of external components, these HV version

So HV version, preceded by bridge rectifier and insulated wart input.
Used this chip, did not see ultra short spikes
but I have no femtosecond capable scope...
10 to 12 GHz sat reception was still OK though.

 

[Mike Monett VE3BTI]

Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:

søndag den 2. oktober 2022 kl. 01.40.48 UTC+2 skrev Mike Monett VE3BTI:
Phil Hobbs <pcdhSpamM...@electrooptical.net> wrote:

I think the circuit you mean is at
https://electrooptical.net/static/oldsite/www.analog-innovations.com/
S ED /OverAndReverseVoltageProtection.pdf>.

One could maybe save the BJT by using an LM4041 instead, but it would

depend on the threshold voltage of the second FET.

Cheers

Phil Hobbs

Resistor R3 of 100 Ohms may be a typo. This requires the TL431 to sink
246 mA at an input of 30V, which is typical of an unregulated 24V wall
wart with little or no load.
This is well over the limit of 100 mA of the
TL431. Changing R3 to 1K gives a much more reasonable 27.8 mA max at
30V.

Also, the GS voltage of M1 limits the maximum input voltage to +-8V. I
know JL has reached 70V or so without damage, but I tend to be
sceptical of exceeding voltage ratings.
However, the input of 24V that JL asked for far exceeds this limit.

the gates just need a zener and a series resistor

Obviously. However, there is a much more serious problem. Jim\'s circuit
does not protect against reverse polarity due to the body diode of the
mosfet. Neither does the SLVA163. JL had requested this feature.

The obvious solution is to add a diode in series with the input. This will
add a slight voltage drop, which can be accommodated in a number of ways,
or simply ignored.

Here is the complete TL431 OVP circuit including reverse polarity
protection:

https://tinyurl.com/z8d5secn




--
MRM

 

[Phil Allison]

Sylvia Else wrote:
=============

Crowbar circuit?


** See JL\'s first post, forth para.


Yes.

I like crowbars. No finesse required.

** A 16amp triac with a 12v zener provides full protection.

Will trip at 13V with normal polarity and about 1.5V reverse.
Anyone stupid enough to use the wrong voltage/ polarity wall wart deserves to see it die.


...... Phil

 

[John Walliker]

On Sunday, 2 October 2022 at 06:09:19 UTC+1, Mike Monett VE3BTI wrote:

Lasse Langwadt Christensen <lang...@fonz.dk> wrote:

søndag den 2. oktober 2022 kl. 01.40.48 UTC+2 skrev Mike Monett VE3BTI:
Phil Hobbs <pcdhSpamM...@electrooptical.net> wrote:

I think the circuit you mean is at
https://electrooptical.net/static/oldsite/www.analog-innovations.com/
S ED /OverAndReverseVoltageProtection.pdf>.

One could maybe save the BJT by using an LM4041 instead, but it would

depend on the threshold voltage of the second FET.

Cheers

Phil Hobbs

Resistor R3 of 100 Ohms may be a typo. This requires the TL431 to sink
246 mA at an input of 30V, which is typical of an unregulated 24V wall
wart with little or no load.
This is well over the limit of 100 mA of the
TL431. Changing R3 to 1K gives a much more reasonable 27.8 mA max at
30V.

Also, the GS voltage of M1 limits the maximum input voltage to +-8V. I
know JL has reached 70V or so without damage, but I tend to be
sceptical of exceeding voltage ratings.
However, the input of 24V that JL asked for far exceeds this limit.

the gates just need a zener and a series resistor
Obviously. However, there is a much more serious problem. Jim\'s circuit
does not protect against reverse polarity due to the body diode of the
mosfet. Neither does the SLVA163. JL had requested this feature.

The obvious solution is to add a diode in series with the input. This will
add a slight voltage drop, which can be accommodated in a number of ways,
or simply ignored.

Here is the complete TL431 OVP circuit including reverse polarity
protection:

https://tinyurl.com/z8d5secn

I don\'t see a problem with the body diode in Jim\'s circuit. I do agree that
R3 must be a typo though.

John

 

[Lasse Langwadt Christensen]

søndag den 2. oktober 2022 kl. 07.09.19 UTC+2 skrev Mike Monett VE3BTI:

Lasse Langwadt Christensen <lang...@fonz.dk> wrote:

søndag den 2. oktober 2022 kl. 01.40.48 UTC+2 skrev Mike Monett VE3BTI:
Phil Hobbs <pcdhSpamM...@electrooptical.net> wrote:

I think the circuit you mean is at
https://electrooptical.net/static/oldsite/www.analog-innovations.com/
S ED /OverAndReverseVoltageProtection.pdf>.

One could maybe save the BJT by using an LM4041 instead, but it would

depend on the threshold voltage of the second FET.

Cheers

Phil Hobbs

Resistor R3 of 100 Ohms may be a typo. This requires the TL431 to sink
246 mA at an input of 30V, which is typical of an unregulated 24V wall
wart with little or no load.
This is well over the limit of 100 mA of the
TL431. Changing R3 to 1K gives a much more reasonable 27.8 mA max at
30V.

Also, the GS voltage of M1 limits the maximum input voltage to +-8V. I
know JL has reached 70V or so without damage, but I tend to be
sceptical of exceeding voltage ratings.
However, the input of 24V that JL asked for far exceeds this limit.

the gates just need a zener and a series resistor
Obviously. However, there is a much more serious problem. Jim\'s circuit
does not protect against reverse polarity due to the body diode of the
mosfet. Neither does the SLVA163. JL had requested this feature.

The obvious solution is to add a diode in series with the input. This will
add a slight voltage drop, which can be accommodated in a number of ways,
or simply ignored.

look closer at the schematic, the reverse protection does work

the first FET is reverse so initially the body diode will work as a
series diode and when the FET turns on so there is no voltage drop