HV dc/dc...

[legg]

On Sun, 19 Jul 2020 22:57:23 -0700 (PDT), Klaus Kragelund
<klauskvik@hotmail.com> wrote:

On Sunday, July 19, 2020 at 5:33:42 PM UTC+3, Bill Sloman wrote:
On Sunday, July 19, 2020 at 12:42:42 PM UTC+10, jla...@highlandsniptechnology.com wrote:
On Sat, 18 Jul 2020 19:31:09 -0700, Joerg <ne...@analogconsultants.com
wrote:

On 2020-07-18 12:39, jla...@highlandsniptechnology.com wrote:
On Sat, 18 Jul 2020 11:27:16 -0700, Joerg <ne...@analogconsultants.com
wrote:

On 2020-07-17 09:49, jla...@highlandsniptechnology.com wrote:


I need eight isolated 150 volt DC supplies, low current, under 1 mA
average. Commercial dc/dc converters are crazy expensive:

https://www.digikey.com/products/en/power-supplies-board-mount/dc-dc-converters/922?k=&pkeyword=&sv=0&pv183=354808&pv183=354809&pv2211=i1&pv1525=100671&pv1525=114705&pv1525=140848&pv1525=157291&pv1525=182727&sf=1&FV=-8%7C922&quantity=&ColumnSort=0&page=1&pageSize=25

I guess I\'ll have to design it. Coilcraft has some nice little flyback
transformers.

I think I can use one flyback driver circuit and put all eight
primaries in parallel. Maybe regulate a little on the high sides.

The application is eight isolated high-voltage pulse outputs. My first
idea was to use grounded drivers and final pulse transformers, but the
volt-seconds get huge so the pulse transformer would be awful. Better
to float the entire output circuit.


Mostly I used CCFL inverter transformers for that. Cheap, fairly small.
Even complete modules can be had for a few dollars:

https://www.ebay.com/itm/1Pc-CCFL-inverter-board-for-LCD-screen-with-1CCFL-backlight-LCD-JN/392849295194

$3.33 with free shipping from China. We pay for that.


Yup, they\'ll make the next aircraft carrier :-(


Or course, with everything going LED and OLED these days it\'s only a
matter of years until the available selection starts to thin out.

I won\'t use ebay or Amazon stuff in my gear. Some of my customers care
about part traceability and anti-Chinese stuff.

Some of those things, ebay and Amazon, are OK for breadboards and lab
cables and such.

One customer recently elected to buy a bunch of $40 cables from us,
when Amazon has them for $6.


It was just meant as an example. On most projects where I needed a few
hundred volts I used the bare CCFL transformers and they cost just a few
bucks. Even from US sources they are often produced abroad, sometimes in
China.

Are the CCFL supplies flybacks or Royers or something? What sorts of
open-circuit voltages do they make?
It\'s probably Baxandall Class-D oscillator. Jim Williams seems to have got the circuit from England without getting the literature reference that should have come with it - Baxandall, P.J, Proc I.E.E 106, B, 748 (1959.

http://sophia-elektronica.com/0344_001_Baxandal.pdf

From my web-site.

\"The circuit is probably best known from Jim Williams’ series of application notes for Linear Technology, on high frequency inverters for driving cold cathode back-lights used in laptop computers (application notes AN45, AN49, AN51, AN55, AN61, AN65). Jim Williams describes the inverter as a current driven Royer inverter, referring back to the non-resonant inverter described by Bright, Pittman and George H. Royer in 1954 in a paper “Transistors as on-off switches in saturable core circuits” in Electrical Manufacturing.\"

The Baxandall inverter is handy for driving high-turns ratio step-up transformers which tend end up with rather low self-resonant frequencies.
But right, it\'s all LEDs now.

I like ISDN transformers, but they will be gone too.

The little DRQ-type dual inductors are great. The autotransformer
flyback and CW multiplier thing is cool.
The Cockroft-Walton multiplier isn\'t all that cool.

Or you could learn how to design your own special purpose transformers and find a shop that would wind them for you - it isn\'t all that difficult.

There are lots of variables to twiddle in a transformer design, so getting something close enough off the shelf isn\'t easy, even if you get downright sloppy about \"close enough\".

You seem to indicate Williams ripped off the Baxandall converter

Isn’t it more that Baxandall copyed and minimally improved on the 1954 Royer converter?

About the Baxandall, has anyone ever used it for commercial product, or is it like for example the Cuk converter and other “Novel” PhD topologies that is really only good on paper?

I agree that custom magnetics rules. For a volume above 50k you gain a competitive advantage that designs using ready made components fails to have. In my career I have only used ready made for a converter a couple of times (not counting buck converters)

Cheers

Klaus

It has had commercial applications at medium power levels,
where multiple outputs or isolators are needed. I\'ve never
heard it seriously referred to as a Baxandall circuit -
it\'s just a current-fed inverter.

RL

 

[Klaus Kragelund]

If you go 20 years back, almost all the ATX PC supplies used a Royer followed by several buck outputs

Cheers

Klaus

 

[Klaus Kragelund]

If you go 20 years back, almost all the ATX PC supplies used a Royer followed by several buck outputs

Cheers

Klaus

 

[server]

It has had commercial applications at medium power levels,
where multiple outputs or isolators are needed. I\'ve never
heard it seriously referred to as a Baxandall circuit -
it\'s just a current-fed inverter.

\"Baxandall\" is a much tonier name though.

Cheers

Phil Hobbs

 

[Klaus Kragelund]

If you go 20 years back, almost all the ATX PC supplies used a Royer followed by several buck outputs

Cheers

Klaus

 

[server]

It has had commercial applications at medium power levels,
where multiple outputs or isolators are needed. I\'ve never
heard it seriously referred to as a Baxandall circuit -
it\'s just a current-fed inverter.

\"Baxandall\" is a much tonier name though.

Cheers

Phil Hobbs

 

[Joerg]

On 2020-07-20 10:49, John Larkin wrote:

On Sun, 19 Jul 2020 11:35:01 -0700, Joerg <news@analogconsultants.com
wrote:

On 2020-07-19 06:57, Phil Hobbs wrote:
On 2020-07-18 22:42, jlarkin@highlandsniptechnology.com wrote:
On Sat, 18 Jul 2020 19:31:09 -0700, Joerg <news@analogconsultants.com
wrote:

On 2020-07-18 12:39, jlarkin@highlandsniptechnology.com wrote:
On Sat, 18 Jul 2020 11:27:16 -0700, Joerg <news@analogconsultants.com
wrote:


[...]

Or course, with everything going LED and OLED these days it\'s only a
matter of years until the available selection starts to thin out.

I won\'t use ebay or Amazon stuff in my gear. Some of my customers care
about part traceability and anti-Chinese stuff.

Some of those things, ebay and Amazon, are OK for breadboards and lab
cables and such.

One customer recently elected to buy a bunch of $40 cables from us,
when Amazon has them for $6.


It was just meant as an example. On most projects where I needed a few
hundred volts I used the bare CCFL transformers and they cost just a few
bucks. Even from US sources they are often produced abroad, sometimes in
China.

Are the CCFL supplies flybacks or Royers or something? What sorts of
open-circuit voltages do they make?

But right, it\'s all LEDs now.

I like ISDN transformers, but they will be gone too.


Yes, and they have limits in terms of voltage.


The little DRQ-type dual inductors are great. The autotransformer
flyback and CW multiplier thing is cool.


I also love dual-winding coils. Just make sure to vet the isolation
voltage with the manufacturer.

Some have no specs. I\'ve tested some to breakdown. One DRQ127 failed
at 2250.

Just keep in mind that there can be half an order of magnitude
difference between working voltage and rated breakdown, or easily a
whole order of magnitude to where it actually breaks down.

This is why we can\'t do hipot tests for very long, because it\'s
gradually destructive to the parts.

The ones I\'ve used have been Royers, with open-circuit outputs over a
kilovolt (so they can strike the discharge).


They can generate 1200V or more but I never used them that high. I
either drive them with an externally driven Royer (from logic on my
board) or drive them directly from a gate driver.

Here\'s a 1400 volt opamp supply:

https://www.dropbox.com/s/6b0sg9j3t457zl5/28S840A.pdf?dl=0

With the Cockroft-Walton on the secondary it could be ok regarding
breakdown. If it goes into a product I\'d vet it with the coil
manufacturer though.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

On 2020-07-20 10:49, John Larkin wrote:

On Sun, 19 Jul 2020 11:35:01 -0700, Joerg <news@analogconsultants.com
wrote:

On 2020-07-19 06:57, Phil Hobbs wrote:
On 2020-07-18 22:42, jlarkin@highlandsniptechnology.com wrote:
On Sat, 18 Jul 2020 19:31:09 -0700, Joerg <news@analogconsultants.com
wrote:

On 2020-07-18 12:39, jlarkin@highlandsniptechnology.com wrote:
On Sat, 18 Jul 2020 11:27:16 -0700, Joerg <news@analogconsultants.com
wrote:


[...]

Or course, with everything going LED and OLED these days it\'s only a
matter of years until the available selection starts to thin out.

I won\'t use ebay or Amazon stuff in my gear. Some of my customers care
about part traceability and anti-Chinese stuff.

Some of those things, ebay and Amazon, are OK for breadboards and lab
cables and such.

One customer recently elected to buy a bunch of $40 cables from us,
when Amazon has them for $6.


It was just meant as an example. On most projects where I needed a few
hundred volts I used the bare CCFL transformers and they cost just a few
bucks. Even from US sources they are often produced abroad, sometimes in
China.

Are the CCFL supplies flybacks or Royers or something? What sorts of
open-circuit voltages do they make?

But right, it\'s all LEDs now.

I like ISDN transformers, but they will be gone too.


Yes, and they have limits in terms of voltage.


The little DRQ-type dual inductors are great. The autotransformer
flyback and CW multiplier thing is cool.


I also love dual-winding coils. Just make sure to vet the isolation
voltage with the manufacturer.

Some have no specs. I\'ve tested some to breakdown. One DRQ127 failed
at 2250.

Just keep in mind that there can be half an order of magnitude
difference between working voltage and rated breakdown, or easily a
whole order of magnitude to where it actually breaks down.

This is why we can\'t do hipot tests for very long, because it\'s
gradually destructive to the parts.

The ones I\'ve used have been Royers, with open-circuit outputs over a
kilovolt (so they can strike the discharge).


They can generate 1200V or more but I never used them that high. I
either drive them with an externally driven Royer (from logic on my
board) or drive them directly from a gate driver.

Here\'s a 1400 volt opamp supply:

https://www.dropbox.com/s/6b0sg9j3t457zl5/28S840A.pdf?dl=0

With the Cockroft-Walton on the secondary it could be ok regarding
breakdown. If it goes into a product I\'d vet it with the coil
manufacturer though.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[server]

On Tue, 21 Jul 2020 10:04:57 -0700, Joerg <news@analogconsultants.com>
wrote:

On 2020-07-20 10:49, John Larkin wrote:
On Sun, 19 Jul 2020 11:35:01 -0700, Joerg <news@analogconsultants.com
wrote:

On 2020-07-19 06:57, Phil Hobbs wrote:
On 2020-07-18 22:42, jlarkin@highlandsniptechnology.com wrote:
On Sat, 18 Jul 2020 19:31:09 -0700, Joerg <news@analogconsultants.com
wrote:

On 2020-07-18 12:39, jlarkin@highlandsniptechnology.com wrote:
On Sat, 18 Jul 2020 11:27:16 -0700, Joerg <news@analogconsultants.com
wrote:


[...]

Or course, with everything going LED and OLED these days it\'s only a
matter of years until the available selection starts to thin out.

I won\'t use ebay or Amazon stuff in my gear. Some of my customers care
about part traceability and anti-Chinese stuff.

Some of those things, ebay and Amazon, are OK for breadboards and lab
cables and such.

One customer recently elected to buy a bunch of $40 cables from us,
when Amazon has them for $6.


It was just meant as an example. On most projects where I needed a few
hundred volts I used the bare CCFL transformers and they cost just a few
bucks. Even from US sources they are often produced abroad, sometimes in
China.

Are the CCFL supplies flybacks or Royers or something? What sorts of
open-circuit voltages do they make?

But right, it\'s all LEDs now.

I like ISDN transformers, but they will be gone too.


Yes, and they have limits in terms of voltage.


The little DRQ-type dual inductors are great. The autotransformer
flyback and CW multiplier thing is cool.


I also love dual-winding coils. Just make sure to vet the isolation
voltage with the manufacturer.

Some have no specs. I\'ve tested some to breakdown. One DRQ127 failed
at 2250.


Just keep in mind that there can be half an order of magnitude
difference between working voltage and rated breakdown, or easily a
whole order of magnitude to where it actually breaks down.

This is why we can\'t do hipot tests for very long, because it\'s
gradually destructive to the parts.



The ones I\'ve used have been Royers, with open-circuit outputs over a
kilovolt (so they can strike the discharge).


They can generate 1200V or more but I never used them that high. I
either drive them with an externally driven Royer (from logic on my
board) or drive them directly from a gate driver.

Here\'s a 1400 volt opamp supply:

https://www.dropbox.com/s/6b0sg9j3t457zl5/28S840A.pdf?dl=0


With the Cockroft-Walton on the secondary it could be ok regarding
breakdown. If it goes into a product I\'d vet it with the coil
manufacturer though.

It\'s in a product and seems OK so far. 350 volts peak is pretty far
from the 2250 breakdown.

It\'s impressive how much voltage tiny magnet wire can stand. A twisted
pair of #40 arced at about 1200 volts.

The more interesting part of that project was the 1400 volt opamps.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[server]

On Tue, 21 Jul 2020 10:04:57 -0700, Joerg <news@analogconsultants.com>
wrote:

On 2020-07-20 10:49, John Larkin wrote:
On Sun, 19 Jul 2020 11:35:01 -0700, Joerg <news@analogconsultants.com
wrote:

On 2020-07-19 06:57, Phil Hobbs wrote:
On 2020-07-18 22:42, jlarkin@highlandsniptechnology.com wrote:
On Sat, 18 Jul 2020 19:31:09 -0700, Joerg <news@analogconsultants.com
wrote:

On 2020-07-18 12:39, jlarkin@highlandsniptechnology.com wrote:
On Sat, 18 Jul 2020 11:27:16 -0700, Joerg <news@analogconsultants.com
wrote:


[...]

Or course, with everything going LED and OLED these days it\'s only a
matter of years until the available selection starts to thin out.

I won\'t use ebay or Amazon stuff in my gear. Some of my customers care
about part traceability and anti-Chinese stuff.

Some of those things, ebay and Amazon, are OK for breadboards and lab
cables and such.

One customer recently elected to buy a bunch of $40 cables from us,
when Amazon has them for $6.


It was just meant as an example. On most projects where I needed a few
hundred volts I used the bare CCFL transformers and they cost just a few
bucks. Even from US sources they are often produced abroad, sometimes in
China.

Are the CCFL supplies flybacks or Royers or something? What sorts of
open-circuit voltages do they make?

But right, it\'s all LEDs now.

I like ISDN transformers, but they will be gone too.


Yes, and they have limits in terms of voltage.


The little DRQ-type dual inductors are great. The autotransformer
flyback and CW multiplier thing is cool.


I also love dual-winding coils. Just make sure to vet the isolation
voltage with the manufacturer.

Some have no specs. I\'ve tested some to breakdown. One DRQ127 failed
at 2250.


Just keep in mind that there can be half an order of magnitude
difference between working voltage and rated breakdown, or easily a
whole order of magnitude to where it actually breaks down.

This is why we can\'t do hipot tests for very long, because it\'s
gradually destructive to the parts.



The ones I\'ve used have been Royers, with open-circuit outputs over a
kilovolt (so they can strike the discharge).


They can generate 1200V or more but I never used them that high. I
either drive them with an externally driven Royer (from logic on my
board) or drive them directly from a gate driver.

Here\'s a 1400 volt opamp supply:

https://www.dropbox.com/s/6b0sg9j3t457zl5/28S840A.pdf?dl=0


With the Cockroft-Walton on the secondary it could be ok regarding
breakdown. If it goes into a product I\'d vet it with the coil
manufacturer though.

It\'s in a product and seems OK so far. 350 volts peak is pretty far
from the 2250 breakdown.

It\'s impressive how much voltage tiny magnet wire can stand. A twisted
pair of #40 arced at about 1200 volts.

The more interesting part of that project was the 1400 volt opamps.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[server]

On Tue, 21 Jul 2020 10:04:57 -0700, Joerg <news@analogconsultants.com>
wrote:

On 2020-07-20 10:49, John Larkin wrote:
On Sun, 19 Jul 2020 11:35:01 -0700, Joerg <news@analogconsultants.com
wrote:

On 2020-07-19 06:57, Phil Hobbs wrote:
On 2020-07-18 22:42, jlarkin@highlandsniptechnology.com wrote:
On Sat, 18 Jul 2020 19:31:09 -0700, Joerg <news@analogconsultants.com
wrote:

On 2020-07-18 12:39, jlarkin@highlandsniptechnology.com wrote:
On Sat, 18 Jul 2020 11:27:16 -0700, Joerg <news@analogconsultants.com
wrote:


[...]

Or course, with everything going LED and OLED these days it\'s only a
matter of years until the available selection starts to thin out.

I won\'t use ebay or Amazon stuff in my gear. Some of my customers care
about part traceability and anti-Chinese stuff.

Some of those things, ebay and Amazon, are OK for breadboards and lab
cables and such.

One customer recently elected to buy a bunch of $40 cables from us,
when Amazon has them for $6.


It was just meant as an example. On most projects where I needed a few
hundred volts I used the bare CCFL transformers and they cost just a few
bucks. Even from US sources they are often produced abroad, sometimes in
China.

Are the CCFL supplies flybacks or Royers or something? What sorts of
open-circuit voltages do they make?

But right, it\'s all LEDs now.

I like ISDN transformers, but they will be gone too.


Yes, and they have limits in terms of voltage.


The little DRQ-type dual inductors are great. The autotransformer
flyback and CW multiplier thing is cool.


I also love dual-winding coils. Just make sure to vet the isolation
voltage with the manufacturer.

Some have no specs. I\'ve tested some to breakdown. One DRQ127 failed
at 2250.


Just keep in mind that there can be half an order of magnitude
difference between working voltage and rated breakdown, or easily a
whole order of magnitude to where it actually breaks down.

This is why we can\'t do hipot tests for very long, because it\'s
gradually destructive to the parts.



The ones I\'ve used have been Royers, with open-circuit outputs over a
kilovolt (so they can strike the discharge).


They can generate 1200V or more but I never used them that high. I
either drive them with an externally driven Royer (from logic on my
board) or drive them directly from a gate driver.

Here\'s a 1400 volt opamp supply:

https://www.dropbox.com/s/6b0sg9j3t457zl5/28S840A.pdf?dl=0


With the Cockroft-Walton on the secondary it could be ok regarding
breakdown. If it goes into a product I\'d vet it with the coil
manufacturer though.

It\'s in a product and seems OK so far. 350 volts peak is pretty far
from the 2250 breakdown.

It\'s impressive how much voltage tiny magnet wire can stand. A twisted
pair of #40 arced at about 1200 volts.

The more interesting part of that project was the 1400 volt opamps.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[Piotr Wyderski]

jlarkin@highlandsniptechnology.com wrote:

It\'s impressive how much voltage tiny magnet wire can stand. A twisted
pair of #40 arced at about 1200 volts.

Use TIW and enjoy arcing at about 7kV.

Best regards, Piotr

 

[Piotr Wyderski]

jlarkin@highlandsniptechnology.com wrote:

It\'s impressive how much voltage tiny magnet wire can stand. A twisted
pair of #40 arced at about 1200 volts.

Use TIW and enjoy arcing at about 7kV.

Best regards, Piotr

 

[Piotr Wyderski]

jlarkin@highlandsniptechnology.com wrote:

It\'s impressive how much voltage tiny magnet wire can stand. A twisted
pair of #40 arced at about 1200 volts.

Use TIW and enjoy arcing at about 7kV.

Best regards, Piotr

 

[Joerg]

On 2020-07-21 10:38, jlarkin@highlandsniptechnology.com wrote:

On Tue, 21 Jul 2020 10:04:57 -0700, Joerg <news@analogconsultants.com
wrote:

On 2020-07-20 10:49, John Larkin wrote:
On Sun, 19 Jul 2020 11:35:01 -0700, Joerg <news@analogconsultants.com
wrote:

On 2020-07-19 06:57, Phil Hobbs wrote:

[...]

The ones I\'ve used have been Royers, with open-circuit outputs over a
kilovolt (so they can strike the discharge).


They can generate 1200V or more but I never used them that high. I
either drive them with an externally driven Royer (from logic on my
board) or drive them directly from a gate driver.

Here\'s a 1400 volt opamp supply:

https://www.dropbox.com/s/6b0sg9j3t457zl5/28S840A.pdf?dl=0


With the Cockroft-Walton on the secondary it could be ok regarding
breakdown. If it goes into a product I\'d vet it with the coil
manufacturer though.

It\'s in a product and seems OK so far. 350 volts peak is pretty far
from the 2250 breakdown.

IME that can bee too close. Gradual degradation sets in early.

It\'s impressive how much voltage tiny magnet wire can stand. A twisted
pair of #40 arced at about 1200 volts.

Sure, but even at 100V manufacturers often avoid direct layer-on-layer.

The more interesting part of that project was the 1400 volt opamps.

Oh yeah

I am working on a project with 400V right now and yesterday the almost
inevitable happened. I unhooked a scope probe clip from the source of a
big FET and it briefly touched the drain ... tsst *BAM* ... and now I am
down one scope hook. The hook part in it had evaporated instantly. The
scope set at 50mV/div came through unscathed.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

On 2020-07-21 10:38, jlarkin@highlandsniptechnology.com wrote:

On Tue, 21 Jul 2020 10:04:57 -0700, Joerg <news@analogconsultants.com
wrote:

On 2020-07-20 10:49, John Larkin wrote:
On Sun, 19 Jul 2020 11:35:01 -0700, Joerg <news@analogconsultants.com
wrote:

On 2020-07-19 06:57, Phil Hobbs wrote:

[...]

The ones I\'ve used have been Royers, with open-circuit outputs over a
kilovolt (so they can strike the discharge).


They can generate 1200V or more but I never used them that high. I
either drive them with an externally driven Royer (from logic on my
board) or drive them directly from a gate driver.

Here\'s a 1400 volt opamp supply:

https://www.dropbox.com/s/6b0sg9j3t457zl5/28S840A.pdf?dl=0


With the Cockroft-Walton on the secondary it could be ok regarding
breakdown. If it goes into a product I\'d vet it with the coil
manufacturer though.

It\'s in a product and seems OK so far. 350 volts peak is pretty far
from the 2250 breakdown.

IME that can bee too close. Gradual degradation sets in early.

It\'s impressive how much voltage tiny magnet wire can stand. A twisted
pair of #40 arced at about 1200 volts.

Sure, but even at 100V manufacturers often avoid direct layer-on-layer.

The more interesting part of that project was the 1400 volt opamps.

Oh yeah

I am working on a project with 400V right now and yesterday the almost
inevitable happened. I unhooked a scope probe clip from the source of a
big FET and it briefly touched the drain ... tsst *BAM* ... and now I am
down one scope hook. The hook part in it had evaporated instantly. The
scope set at 50mV/div came through unscathed.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

On 2020-07-21 10:38, jlarkin@highlandsniptechnology.com wrote:

On Tue, 21 Jul 2020 10:04:57 -0700, Joerg <news@analogconsultants.com
wrote:

On 2020-07-20 10:49, John Larkin wrote:
On Sun, 19 Jul 2020 11:35:01 -0700, Joerg <news@analogconsultants.com
wrote:

On 2020-07-19 06:57, Phil Hobbs wrote:

[...]

The ones I\'ve used have been Royers, with open-circuit outputs over a
kilovolt (so they can strike the discharge).


They can generate 1200V or more but I never used them that high. I
either drive them with an externally driven Royer (from logic on my
board) or drive them directly from a gate driver.

Here\'s a 1400 volt opamp supply:

https://www.dropbox.com/s/6b0sg9j3t457zl5/28S840A.pdf?dl=0


With the Cockroft-Walton on the secondary it could be ok regarding
breakdown. If it goes into a product I\'d vet it with the coil
manufacturer though.

It\'s in a product and seems OK so far. 350 volts peak is pretty far
from the 2250 breakdown.

IME that can bee too close. Gradual degradation sets in early.

It\'s impressive how much voltage tiny magnet wire can stand. A twisted
pair of #40 arced at about 1200 volts.

Sure, but even at 100V manufacturers often avoid direct layer-on-layer.

The more interesting part of that project was the 1400 volt opamps.

Oh yeah

I am working on a project with 400V right now and yesterday the almost
inevitable happened. I unhooked a scope probe clip from the source of a
big FET and it briefly touched the drain ... tsst *BAM* ... and now I am
down one scope hook. The hook part in it had evaporated instantly. The
scope set at 50mV/div came through unscathed.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[John Larkin]

On Tue, 21 Jul 2020 11:17:10 -0700, Joerg <news@analogconsultants.com>
wrote:

On 2020-07-21 10:38, jlarkin@highlandsniptechnology.com wrote:
On Tue, 21 Jul 2020 10:04:57 -0700, Joerg <news@analogconsultants.com
wrote:

On 2020-07-20 10:49, John Larkin wrote:
On Sun, 19 Jul 2020 11:35:01 -0700, Joerg <news@analogconsultants.com
wrote:

On 2020-07-19 06:57, Phil Hobbs wrote:

[...]


The ones I\'ve used have been Royers, with open-circuit outputs over a
kilovolt (so they can strike the discharge).


They can generate 1200V or more but I never used them that high. I
either drive them with an externally driven Royer (from logic on my
board) or drive them directly from a gate driver.

Here\'s a 1400 volt opamp supply:

https://www.dropbox.com/s/6b0sg9j3t457zl5/28S840A.pdf?dl=0


With the Cockroft-Walton on the secondary it could be ok regarding
breakdown. If it goes into a product I\'d vet it with the coil
manufacturer though.

It\'s in a product and seems OK so far. 350 volts peak is pretty far
from the 2250 breakdown.


IME that can bee too close. Gradual degradation sets in early.


It\'s impressive how much voltage tiny magnet wire can stand. A twisted
pair of #40 arced at about 1200 volts.


Sure, but even at 100V manufacturers often avoid direct layer-on-layer.


The more interesting part of that project was the 1400 volt opamps.


Oh yeah

I am working on a project with 400V right now and yesterday the almost
inevitable happened. I unhooked a scope probe clip from the source of a
big FET and it briefly touched the drain ... tsst *BAM* ... and now I am
down one scope hook. The hook part in it had evaporated instantly. The
scope set at 50mV/div came through unscathed.

We have one of the fully isolated Tek scopes. You can clip the probe
\"ground\" thing anywhere. That\'s fabulous.

 

[legg]

On Tue, 21 Jul 2020 08:53:36 -0700 (PDT), Klaus Kragelund
<klauskvik@hotmail.com> wrote:

If you go 20 years back, almost all the ATX PC supplies used a Royer followed by several buck outputs

Cheers

Klaus

Boschert had an (almost) current fed inverter, using a 723 to
control the buck section, nonlinearly, synced to the self-oscillating
Jensen inverter.

That\'s one step up from the Royer - using a second small saturable
(proportional-base-drive) transformer to set the operating frequency.

The inverter stage might be push-pull or half-bridge (Harada) without
major changes to component count or drive transformer, depending upon
the power level (130 - 400W).

Anyways, must have been hundreds of thousands of these in the market,
at one time - being custom built into IBM, Burroughs and NCR hardware.
So, mainframes, not PCs.

At 50W or less (ATX), it would have been a single-switch
self-oscillating two-transformer flyback, using television
semiconductors, until optocouplers bumped the second transformer
out.

There were were always IC-control-switched types of all conventional
topologies, with 60Hz housekeeping control power, though some novel
magnetically regulated versions showed up in Europe for a while.

G.H.Royer; \"A Switching Transistor DC to AC Converter having an Output
Frequency Proportional to the dc Input Voltage\",
AIEE Transactions on Communications and Electronics, 74,
pp 322-326, 1955

J.L.Jensen; \"An Improved Square-wave Oscillator Circuit\",
IRE Transactions on Circuit Theory, CT-4
pp 276-279, September 1957.

 

[Joerg]

On 2020-07-21 11:46, John Larkin wrote:

On Tue, 21 Jul 2020 11:17:10 -0700, Joerg <news@analogconsultants.com
wrote:

On 2020-07-21 10:38, jlarkin@highlandsniptechnology.com wrote:

[...]

The more interesting part of that project was the 1400 volt opamps.


Oh yeah

I am working on a project with 400V right now and yesterday the almost
inevitable happened. I unhooked a scope probe clip from the source of a
big FET and it briefly touched the drain ... tsst *BAM* ... and now I am
down one scope hook. The hook part in it had evaporated instantly. The
scope set at 50mV/div came through unscathed.

We have one of the fully isolated Tek scopes. You can clip the probe
\"ground\" thing anywhere. That\'s fabulous.

That would have been really helpful in this case. I am measuring 100mV
signals across a shunt in the presence of huge magnetic spikes. It
barely works with CH1 minus Ch2 and very careful cable routing. But,
almost done now.

--
Regards, Joerg

http://www.analogconsultants.com/