HV dc/dc...

[Tony Stewart]

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.

I learned from investigating epidemic HIPOT failures on a supplier that
moved production to Mexico I qualified them in SD. It turned out that
that grounding the isolated 48V secondary added more stress to the
primary HIPOT test with a half dozen marginal gap locations with the
slow ramp 1 second DC test that is 10% higher than 1.414x Vac level.

I modified the Sawyer HIPOT tester to reduce the probe impedance from
1uF+10mΩ to 6 x 500k=3MΩ and thus ~1uA fault current when normally it
passed near 0 when charged. Now the failures were non-destructive to the
semiconductors.

Then from my 50kV HIPOT tests on 5MVA OFAM transformers I discovered
that the variation in oil breakdown voltage was due to nano-sized
contaminants that created Partial Discharge (PD and thus) affected the
initial condition to random dielectric failure. The greater the
variation between BDIV or breakdown inception voltage was due to the
pre-breakdown with internal PD. The ideal insulation has BDIV-PDIV=0
and the contaminated insulation has a large difference which is
proportional to the BDIV standard deviation.

Increasing the HIPOT probe impedance or reducing the fault current to
1uA dc or so , limits the damage to insulation, so that it can be
repeated more often for test purposes.

Tony Stewart

 

[Tony Stewart]

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.

I learned from investigating epidemic HIPOT failures on a supplier that
moved production to Mexico I qualified them in SD. It turned out that
that grounding the isolated 48V secondary added more stress to the
primary HIPOT test with a half dozen marginal gap locations with the
slow ramp 1 second DC test that is 10% higher than 1.414x Vac level.

I modified the Sawyer HIPOT tester to reduce the probe impedance from
1uF+10mΩ to 6 x 500k=3MΩ and thus ~1uA fault current when normally it
passed near 0 when charged. Now the failures were non-destructive to the
semiconductors.

Then from my 50kV HIPOT tests on 5MVA OFAM transformers I discovered
that the variation in oil breakdown voltage was due to nano-sized
contaminants that created Partial Discharge (PD and thus) affected the
initial condition to random dielectric failure. The greater the
variation between BDIV or breakdown inception voltage was due to the
pre-breakdown with internal PD. The ideal insulation has BDIV-PDIV=0
and the contaminated insulation has a large difference which is
proportional to the BDIV standard deviation.

Increasing the HIPOT probe impedance or reducing the fault current to
1uA dc or so , limits the damage to insulation, so that it can be
repeated more often for test purposes.

Tony Stewart

 

[piglet]

On 21/07/2020 1:55 pm, legg wrote:

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

Yes, current fed push-pull can be a useful topology. I am quite fond of
the related Weinberg configuration.

Trying to make the Baxandall into a low distortion sine wave generator
is non-trivial and fraught because it relies so critically on exact
class B switching of the two transistors: if there is any non-conducting
deadtime the feed inductor makes the centre tap fly high voltage,
conversely if there is any conduction overlap the resonant LC tank is
damped and purity suffers.

piglet

 

[piglet]

On 21/07/2020 1:55 pm, legg wrote:

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

Yes, current fed push-pull can be a useful topology. I am quite fond of
the related Weinberg configuration.

Trying to make the Baxandall into a low distortion sine wave generator
is non-trivial and fraught because it relies so critically on exact
class B switching of the two transistors: if there is any non-conducting
deadtime the feed inductor makes the centre tap fly high voltage,
conversely if there is any conduction overlap the resonant LC tank is
damped and purity suffers.

piglet

 

[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.

 

[Bill Sloman]

On Tuesday, July 21, 2020 at 8:35:21 AM UTC+10, Klaus Kragelund wrote:

On Monday, July 20, 2020 at 12:59:38 PM UTC+2, Bill Sloman wrote:
On Monday, July 20, 2020 at 3:57:28 PM UTC+10, Klaus Kragelund 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:

<snip>

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

Probably not. He was working in the UK and the Royer paper was in a US trade publication - it doesn\'t show up in the literature cited in his paper..

It was a public available patent:

https://patents.google.com/patent/US2783384A/en

That didn\'t mean that Peter Baxandall would have known about it.

Searching US patents in the late 1950\'s meant paying a patent lawyer. If I remember rightly, that sort of search cost about $100,000 dollars (in late 1950 dollars - think about $890,000 in today\'s money.

Peter Baxandall worked at the UK Royal Radar Research Establishment at Malvern at the time

https://en.wikipedia.org/wiki/Royal_Radar_Establishment

It was a pretty high-powered group, with lots of impressive academics who went off to become professors all mover the place.

Peter would have conformed to academic publication standards, but the Royer paper wouldn\'t have shown up anywhere where an academic would have run into it at that time. I ran into it when I worked at the Plessey Pacific Central Research Lab in Melbourne in 1970-71 - which had fairly close links with academic electronic engineers - but it isn\'t a particularly impressive paper.

Royer saturated his transformer to kill the base drive, which isn\'t an elegant approach. I just relied on the transistors running out of current gain, which is what everybody did at that time.

> So, yes, seems like he ripped it off. Nothing wrong with that, except if Bandaxall didn\'t credit Royer and Bright.

He probably didn\'t know about their work. Literature searching was much more tedious and expensive before the world wide web got going.

It meant going to a university library - as I did from time to time - and digging through abstracts journals. You could find stuff, but it wasn\'t all that easy, and it was easy to miss things.

The inductor on the centre-tap is the major difference from the Royer inverter, and produces very different behavior.

Yes, that was a clever addition

[snip]

--
Bill Sloman, Sydney

 

[Bill Sloman]

On Tuesday, July 21, 2020 at 8:35:21 AM UTC+10, Klaus Kragelund wrote:

On Monday, July 20, 2020 at 12:59:38 PM UTC+2, Bill Sloman wrote:
On Monday, July 20, 2020 at 3:57:28 PM UTC+10, Klaus Kragelund 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:

<snip>

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

Probably not. He was working in the UK and the Royer paper was in a US trade publication - it doesn\'t show up in the literature cited in his paper..

It was a public available patent:

https://patents.google.com/patent/US2783384A/en

That didn\'t mean that Peter Baxandall would have known about it.

Searching US patents in the late 1950\'s meant paying a patent lawyer. If I remember rightly, that sort of search cost about $100,000 dollars (in late 1950 dollars - think about $890,000 in today\'s money.

Peter Baxandall worked at the UK Royal Radar Research Establishment at Malvern at the time

https://en.wikipedia.org/wiki/Royal_Radar_Establishment

It was a pretty high-powered group, with lots of impressive academics who went off to become professors all mover the place.

Peter would have conformed to academic publication standards, but the Royer paper wouldn\'t have shown up anywhere where an academic would have run into it at that time. I ran into it when I worked at the Plessey Pacific Central Research Lab in Melbourne in 1970-71 - which had fairly close links with academic electronic engineers - but it isn\'t a particularly impressive paper.

Royer saturated his transformer to kill the base drive, which isn\'t an elegant approach. I just relied on the transistors running out of current gain, which is what everybody did at that time.

> So, yes, seems like he ripped it off. Nothing wrong with that, except if Bandaxall didn\'t credit Royer and Bright.

He probably didn\'t know about their work. Literature searching was much more tedious and expensive before the world wide web got going.

It meant going to a university library - as I did from time to time - and digging through abstracts journals. You could find stuff, but it wasn\'t all that easy, and it was easy to miss things.

The inductor on the centre-tap is the major difference from the Royer inverter, and produces very different behavior.

Yes, that was a clever addition

[snip]

--
Bill Sloman, Sydney

 

[Bill Sloman]

On Wednesday, July 22, 2020 at 2:01:45 AM UTC+10, pcdh...@gmail.com wrote:

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.

The original Baxandall paper is remarkably obscure, and it was published in a British journal. Neither gets it cited by US workers. Jim Williams didn\'t help.

It took me about a year before I worked out that I couldn\'t get a copy from any university library that I could get at, and decide that I had to pay the money to the \"U.K. Institute of Electrical Engineers, who own the copyright and have given me permission to make it accessible on my web-site\".

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

This isn\'t what they sold me - which had been scanned from a bound copy of the journal - but a rather better scan that I got sent a few years later by somebody who though that I was offering a rather poor quality image.

--
Bill Sloman, Sydney

 

[Bill Sloman]

On Wednesday, July 22, 2020 at 2:01:45 AM UTC+10, pcdh...@gmail.com wrote:

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.

The original Baxandall paper is remarkably obscure, and it was published in a British journal. Neither gets it cited by US workers. Jim Williams didn\'t help.

It took me about a year before I worked out that I couldn\'t get a copy from any university library that I could get at, and decide that I had to pay the money to the \"U.K. Institute of Electrical Engineers, who own the copyright and have given me permission to make it accessible on my web-site\".

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

This isn\'t what they sold me - which had been scanned from a bound copy of the journal - but a rather better scan that I got sent a few years later by somebody who though that I was offering a rather poor quality image.

--
Bill Sloman, Sydney

 

[Bill Sloman]

On Wednesday, July 22, 2020 at 2:01:45 AM UTC+10, pcdh...@gmail.com wrote:

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.

The original Baxandall paper is remarkably obscure, and it was published in a British journal. Neither gets it cited by US workers. Jim Williams didn\'t help.

It took me about a year before I worked out that I couldn\'t get a copy from any university library that I could get at, and decide that I had to pay the money to the \"U.K. Institute of Electrical Engineers, who own the copyright and have given me permission to make it accessible on my web-site\".

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

This isn\'t what they sold me - which had been scanned from a bound copy of the journal - but a rather better scan that I got sent a few years later by somebody who though that I was offering a rather poor quality image.

--
Bill Sloman, Sydney

 

[Bill Sloman]

On Wednesday, July 22, 2020 at 6:57:17 AM UTC+10, piglet wrote:

On 21/07/2020 1:55 pm, legg wrote:
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


Yes, current fed push-pull can be a useful topology. I am quite fond of
the related Weinberg configuration.

Trying to make the Baxandall into a low distortion sine wave generator
is non-trivial and fraught because it relies so critically on exact
class B switching of the two transistors: if there is any non-conducting
deadtime the feed inductor makes the centre tap fly high voltage,
conversely if there is any conduction overlap the resonant LC tank is
damped and purity suffers.

You can make quite a good sine wave relatively easily by replacing the inductor with a current mirror. The efficiency goes down from about 95% to about 50%, but the harmonics are about 80dB below the fundamental.

From my web-site

\"This circuit was developed as a retrofit to excite a linear variable differential transformer used to measure the progressively increasing mass of a single crystal of gallium arsenide (GaAs) being grown in the Metals Research GaAs Liquid-Encapsulated Czochralski (LEC) crystal puller. The circuit it replaced had been developed a decade earlier and used components that had become obsolete in 1986. The new circuit replaced it in new machines and was retrofitted to some older machines.

It’s quite a bit more complicated than the Class-D oscillator, and less efficient – only about 50% of the power fed into the oscillator ends up in the load, rather than the better than 90% transfer you can get with a classic Class-D oscillator – but it’s quite a lot more efficient than any of the low distortion oscillators I know about, and it lends itself to very precise control of the output amplitude. I’ve generated quite a few Spice models of various implementations of the idea, but I’ve yet to get around to building a current version of the real circuit – the 1986 version worked fine, but at that time I wasn’t aware how good the circuit could be and didn’t have any reason to check out its performance in detail.\"

--
Bill Sloman, Sydney

 

[Bill Sloman]

On Wednesday, July 22, 2020 at 6:57:17 AM UTC+10, piglet wrote:

On 21/07/2020 1:55 pm, legg wrote:
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


Yes, current fed push-pull can be a useful topology. I am quite fond of
the related Weinberg configuration.

Trying to make the Baxandall into a low distortion sine wave generator
is non-trivial and fraught because it relies so critically on exact
class B switching of the two transistors: if there is any non-conducting
deadtime the feed inductor makes the centre tap fly high voltage,
conversely if there is any conduction overlap the resonant LC tank is
damped and purity suffers.

You can make quite a good sine wave relatively easily by replacing the inductor with a current mirror. The efficiency goes down from about 95% to about 50%, but the harmonics are about 80dB below the fundamental.

From my web-site

\"This circuit was developed as a retrofit to excite a linear variable differential transformer used to measure the progressively increasing mass of a single crystal of gallium arsenide (GaAs) being grown in the Metals Research GaAs Liquid-Encapsulated Czochralski (LEC) crystal puller. The circuit it replaced had been developed a decade earlier and used components that had become obsolete in 1986. The new circuit replaced it in new machines and was retrofitted to some older machines.

It’s quite a bit more complicated than the Class-D oscillator, and less efficient – only about 50% of the power fed into the oscillator ends up in the load, rather than the better than 90% transfer you can get with a classic Class-D oscillator – but it’s quite a lot more efficient than any of the low distortion oscillators I know about, and it lends itself to very precise control of the output amplitude. I’ve generated quite a few Spice models of various implementations of the idea, but I’ve yet to get around to building a current version of the real circuit – the 1986 version worked fine, but at that time I wasn’t aware how good the circuit could be and didn’t have any reason to check out its performance in detail.\"

--
Bill Sloman, Sydney

 

[Bill Sloman]

On Wednesday, July 22, 2020 at 6:57:17 AM UTC+10, piglet wrote:

On 21/07/2020 1:55 pm, legg wrote:
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


Yes, current fed push-pull can be a useful topology. I am quite fond of
the related Weinberg configuration.

Trying to make the Baxandall into a low distortion sine wave generator
is non-trivial and fraught because it relies so critically on exact
class B switching of the two transistors: if there is any non-conducting
deadtime the feed inductor makes the centre tap fly high voltage,
conversely if there is any conduction overlap the resonant LC tank is
damped and purity suffers.

You can make quite a good sine wave relatively easily by replacing the inductor with a current mirror. The efficiency goes down from about 95% to about 50%, but the harmonics are about 80dB below the fundamental.

From my web-site

\"This circuit was developed as a retrofit to excite a linear variable differential transformer used to measure the progressively increasing mass of a single crystal of gallium arsenide (GaAs) being grown in the Metals Research GaAs Liquid-Encapsulated Czochralski (LEC) crystal puller. The circuit it replaced had been developed a decade earlier and used components that had become obsolete in 1986. The new circuit replaced it in new machines and was retrofitted to some older machines.

It’s quite a bit more complicated than the Class-D oscillator, and less efficient – only about 50% of the power fed into the oscillator ends up in the load, rather than the better than 90% transfer you can get with a classic Class-D oscillator – but it’s quite a lot more efficient than any of the low distortion oscillators I know about, and it lends itself to very precise control of the output amplitude. I’ve generated quite a few Spice models of various implementations of the idea, but I’ve yet to get around to building a current version of the real circuit – the 1986 version worked fine, but at that time I wasn’t aware how good the circuit could be and didn’t have any reason to check out its performance in detail.\"

--
Bill Sloman, Sydney

 

[JM]

On 22/07/2020 05:12, Bill Sloman wrote:

On Wednesday, July 22, 2020 at 2:01:45 AM UTC+10, pcdh...@gmail.com wrote:
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.

The original Baxandall paper is remarkably obscure, and it was published in a British journal. Neither gets it cited by US workers. Jim Williams didn\'t help.

It took me about a year before I worked out that I couldn\'t get a copy from any university library that I could get at, and decide that I had to pay the money to the \"U.K. Institute of Electrical Engineers, who own the copyright and have given me permission to make it accessible on my web-site\".

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

This isn\'t what they sold me - which had been scanned from a bound copy of the journal - but a rather better scan that I got sent a few years later by somebody who though that I was offering a rather poor quality image.

That was me - the original paper you had was very difficult to read.

You should really have a link to Yarrow\'s paper as well (after all it
was submitted and published prior to Baxandall\'s). The design
guidelines in the two differ slightly, Baxandall was (as usual) aiming
to minimise distortion.

I will email a copy to you.

 

[JM]

On 20/07/2020 06:57, Klaus Kragelund 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

(Sorry Klaus I emailed this reply to you by accident).

Oscillators where the switching event id determined by core saturation
were common in the UK in the 30\'s (probably much earlier) and Baxandall,
Yarrow et.all will have been familiar with them. The current fed tuned
oscillator is a completely different design and is not a minimally
improved Royer.

A \"tuned Royer\" is a misnomer.

 

[Bill Sloman]

On Sunday, July 26, 2020 at 7:56:35 AM UTC+10, JM wrote:

On 22/07/2020 05:12, Bill Sloman wrote:
On Wednesday, July 22, 2020 at 2:01:45 AM UTC+10, pcdh...@gmail.com wrote:
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.

The original Baxandall paper is remarkably obscure, and it was published in a British journal. Neither gets it cited by US workers. Jim Williams didn\'t help.

It took me about a year before I worked out that I couldn\'t get a copy from any university library that I could get at, and decide that I had to pay the money to the \"U.K. Institute of Electrical Engineers, who own the copyright and have given me permission to make it accessible on my web-site\".

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

This isn\'t what they sold me - which had been scanned from a bound copy of the journal - but a rather better scan that I got sent a few years later by somebody who though that I was offering a rather poor quality image.

That was me - the original paper you had was very difficult to read.

You should really have a link to Yarrow\'s paper as well (after all it
was submitted and published prior to Baxandall\'s). The design
guidelines in the two differ slightly, Baxandall was (as usual) aiming
to minimise distortion.

I will email a copy to you.

Thanks for the copy. Yarrow\'s paper was actually published at the same time as Baxandall\'s - both papers were presented at the same conference (with Yarrow presenting his two days after Baxandall). I read Baxandall\'s paper as a more general exposition about inductor-capacitor oscillators, if aimed mainly as putting his class-D oscillator into context with more traditional schemes.

My suspicion is that Peter Baxandall - at the Royal Radar Research Establishment (RRE) at Malvern - had been working out how to get a better inverter, and that he\'d been talking to Yarrow to get him to build a few for some specific application that RRE had wanted to pursue.

Publishing theory and practice at the same conference would have suited both of them. Making an explicit link probably wouldn\'t have - the British idea that engineers had grease under their fingernails still hadn\'t entirely gone when I started working in the UK in 1971.

I\'m still trying to get my web-site sorted out to include a reference to Yarrow\'s paper - Libre Office isn\'t a great editor for .htm documents, and getting the hyperlinks to work isn\'t as easy now as I remember from a few years ago. Presumably it has been \"improved\" recently.

--
Bill Sloman, Sydney

 

[Bill Sloman]

On Monday, July 27, 2020 at 11:30:39 PM UTC+10, Bill Sloman wrote:

On Sunday, July 26, 2020 at 7:56:35 AM UTC+10, JM wrote:
On 22/07/2020 05:12, Bill Sloman wrote:
On Wednesday, July 22, 2020 at 2:01:45 AM UTC+10, pcdh...@gmail.com wrote:

<snip>

> I\'m still trying to get my web-site sorted out to include a reference to Yarrow\'s paper - Libre Office isn\'t a great editor for .htm documents, and getting the hyperlinks to work isn\'t as easy now as I remember from a few years ago. Presumably it has been \"improved\" recently.

The more I dug into it, the worse it got. I ended up using Notepad to change the nuts and bolts of the .htm code, and when I open the .htm file with Firefox on my own computer everything seemed to work, but when I up-loaded the same file to my web-site, and look at the page there over the web all the hyperlinks start pointing the web-site I had when I lived in the Netherlands, which hasn\'t existed for some ten years now.

I\'ve asked for support from my current (Australian information provider) and I fully expect to get told that I\'ve missed something that should have been obvious to me. The last time I talked to them the problem turned out to be that I\'d swapped one space in a file name reference for the under-score that should have been there, and I won\'t be in the least surprised to find that this comes from the same kind of trivial error.

--
Bill Sloman, Sydney

 

[Bill Sloman]

On Wednesday, July 29, 2020 at 12:27:26 PM UTC+10, Bill Sloman wrote:

On Monday, July 27, 2020 at 11:30:39 PM UTC+10, Bill Sloman wrote:
On Sunday, July 26, 2020 at 7:56:35 AM UTC+10, JM wrote:
On 22/07/2020 05:12, Bill Sloman wrote:
On Wednesday, July 22, 2020 at 2:01:45 AM UTC+10, pcdh...@gmail.com wrote:
snip
I\'m still trying to get my web-site sorted out to include a reference to Yarrow\'s paper - Libre Office isn\'t a great editor for .htm documents, and getting the hyperlinks to work isn\'t as easy now as I remember from a few years ago. Presumably it has been \"improved\" recently.
The more I dug into it, the worse it got. I ended up using Notepad to change the nuts and bolts of the .htm code, and when I open the .htm file with Firefox on my own computer everything seemed to work, but when I up-loaded the same file to my web-site, and look at the page there over the web all the hyperlinks start pointing the web-site I had when I lived in the Netherlands, which hasn\'t existed for some ten years now.

I\'ve asked for support from my current (Australian) information provider and I fully expect to get told that I\'ve missed something that should have been obvious to me. The last time I talked to them the problem turned out to be that I\'d swapped one space in a file name reference for the under-score that should have been there, and I won\'t be in the least surprised to find that this comes from the same kind of trivial error.

Well. it didn\'t. They are as baffled as I am. And they don\'t see quite the same error, which is even odder.

When I used the \"Firefox\" inspect-element tool to find out what it sees on my website, it turns out not to be the same as Notepad finds in the file that I uploaded to web-site. What I see with my copy of Firefox is perfectly consistent with the error message I get (from my old information provider in the Netherlands) but clearly that\'s not the error message they get.

--
Bill Sloman, Sydney

 

[Bill Sloman]

On Thursday, July 30, 2020 at 3:33:58 PM UTC+10, Bill Sloman wrote:

On Wednesday, July 29, 2020 at 12:27:26 PM UTC+10, Bill Sloman wrote:
On Monday, July 27, 2020 at 11:30:39 PM UTC+10, Bill Sloman wrote:
On Sunday, July 26, 2020 at 7:56:35 AM UTC+10, JM wrote:
On 22/07/2020 05:12, Bill Sloman wrote:
On Wednesday, July 22, 2020 at 2:01:45 AM UTC+10, pcdh...@gmail.com wrote:
snip
I\'m still trying to get my web-site sorted out to include a reference to Yarrow\'s paper - Libre Office isn\'t a great editor for .htm documents, and getting the hyperlinks to work isn\'t as easy now as I remember from a few years ago. Presumably it has been \"improved\" recently.
The more I dug into it, the worse it got. I ended up using Notepad to change the nuts and bolts of the .htm code, and when I open the .htm file with Firefox on my own computer everything seemed to work, but when I up-loaded the same file to my web-site, and look at the page there over the web all the hyperlinks start pointing the web-site I had when I lived in the Netherlands, which hasn\'t existed for some ten years now.

I\'ve asked for support from my current (Australian) information provider and I fully expect to get told that I\'ve missed something that should have been obvious to me. The last time I talked to them the problem turned out to be that I\'d swapped one space in a file name reference for the under-score that should have been there, and I won\'t be in the least surprised to find that this comes from the same kind of trivial error.

Well. it didn\'t. They are as baffled as I am. And they don\'t see quite the same error, which is even odder.

When I used the \"Firefox\" inspect-element tool to find out what it sees on my website, it turns out not to be the same as Notepad finds in the file that I uploaded to web-site. What I see with my copy of Firefox is perfectly consistent with the error message I get (from my old information provider in the Netherlands) but clearly that\'s not the error message they get.

Well, my web-site seems to be working again. I\'m not quite sure what I did to fix it, but it is now displaying what I want it to display, or at least the bit that was giving me trouble looks okay now. Having a bad link to the first image may have prompted the display software to get silly about the first hyperlink (which precedes it) but this is pure guesswork.
--
Bill Sloman, Sydney