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LLC with an explicit discrete Lm
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Piotr Wyderski
Nov 24, 2019, 12:22:10 PM11/24/19
to
I need a number (~20) of fixed voltages in the range of 4-20V.
Isolated and non-isolated, for SIC MOSFET gate drivers, 20V for a small
D class audio amplifier, 3.3V and 5V for logic and 10V for some
auxiliary circuits. The input voltage is in the range of 10.8-15V,
maybe 40W in total.
Due to the number of output rails the complexity of the secondary sides
does matter. This basically kills all the PWM forward-derived
topologies, as they need output inductors. A flyback might be an option,
but I am considering a different aapproch: a stiff LLC "pump" propelling
several way-too-good toroidal transformers (primary Lm in the millihenry
range), connected in parallel. This will allow me to optimize their
properties to match the requirements of a given rail and keep the number
of windings within the sane range. Lower inter-winding capacitace of
unrelated secondaries would be a benefit too. I'll try to make the
effective primary inductance match the LLC design requirements, but if
it is too high, I plan to compensate with a parallel choke. Something
along the lines of the ideal transformer model of an LLC converter, but
this time the equivalent circuit is taken literally.
Has anybody seen anything like that before? Does it make sense?
Best regards, Piotr
Isolated and non-isolated, for SIC MOSFET gate drivers, 20V for a small
D class audio amplifier, 3.3V and 5V for logic and 10V for some
auxiliary circuits. The input voltage is in the range of 10.8-15V,
maybe 40W in total.
Due to the number of output rails the complexity of the secondary sides
does matter. This basically kills all the PWM forward-derived
topologies, as they need output inductors. A flyback might be an option,
but I am considering a different aapproch: a stiff LLC "pump" propelling
several way-too-good toroidal transformers (primary Lm in the millihenry
range), connected in parallel. This will allow me to optimize their
properties to match the requirements of a given rail and keep the number
of windings within the sane range. Lower inter-winding capacitace of
unrelated secondaries would be a benefit too. I'll try to make the
effective primary inductance match the LLC design requirements, but if
it is too high, I plan to compensate with a parallel choke. Something
along the lines of the ideal transformer model of an LLC converter, but
this time the equivalent circuit is taken literally.
Has anybody seen anything like that before? Does it make sense?
Best regards, Piotr
jla...@highlandsniptechnology.com
Nov 24, 2019, 1:13:57 PM11/24/19
to
On Sun, 24 Nov 2019 18:22:03 +0100, Piotr Wyderski
<pete...@neverland.mil> wrote:
>I need a number (~20) of fixed voltages in the range of 4-20V.
>Isolated and non-isolated, for SIC MOSFET gate drivers, 20V for a small
>D class audio amplifier, 3.3V and 5V for logic and 10V for some
>auxiliary circuits. The input voltage is in the range of 10.8-15V,
>maybe 40W in total.
>
>Due to the number of output rails the complexity of the secondary sides
>does matter. This basically kills all the PWM forward-derived
>topologies, as they need output inductors.
A multi-output forward doesn't need inductors and has decent
<pete...@neverland.mil> wrote:
>I need a number (~20) of fixed voltages in the range of 4-20V.
>Isolated and non-isolated, for SIC MOSFET gate drivers, 20V for a small
>D class audio amplifier, 3.3V and 5V for logic and 10V for some
>auxiliary circuits. The input voltage is in the range of 10.8-15V,
>maybe 40W in total.
>
>Due to the number of output rails the complexity of the secondary sides
>does matter. This basically kills all the PWM forward-derived
>topologies, as they need output inductors.
cross-regulation, but you can't PWM regulate. How about a buck
switcher ahead of the forward?
Or no regulation ahead but low-drop linear or switching regs after, as
needed. I've done that a few times.
Power supply design is often a giant puzzle.
--
John Larkin Highland Technology, Inc
lunatic fringe electronics
Piotr Wyderski
Nov 24, 2019, 1:34:56 PM11/24/19
to
jla...@highlandsniptechnology.com wrote:
> A multi-output forward doesn't need inductors and has decent
> cross-regulation, but you can't PWM regulate. How about a buck
> switcher ahead of the forward?
This reminds me the buck-pre-regulated push-pull and indeed is a viable
> A multi-output forward doesn't need inductors and has decent
> cross-regulation, but you can't PWM regulate. How about a buck
> switcher ahead of the forward?
option. An unregulated Baxandall driving the trafos through a magnetic
amplifier is another.
> Or no regulation ahead but low-drop linear or switching regs after, as
> needed. I've done that a few times.
approach: make the transmitting side overly complex for the beneft of
simplified receivers. Can have a big net gain, given the number of
secondaries.
> Power supply design is often a giant puzzle.
power train turned out to be pretty straightforward, even if pretty
advanced: a totem-pole PFC powering a high-voltage LLC converter.
Best regards, Piotr
jla...@highlandsniptechnology.com
Nov 24, 2019, 2:00:22 PM11/24/19
to
So it can make sense to keep the power parts, especially the
transformer, simple and regulate on the secondary. Really small stuff
can use linear regs.
If your main converter has to make a lot of AC anyway, maybe you can
couple that into some small transformers to get the low power stuff.
Jan Panteltje
Nov 24, 2019, 2:12:45 PM11/24/19
to
On a sunny day (Sun, 24 Nov 2019 18:22:03 +0100) it happened Piotr Wyderski
<pete...@neverland.mil> wrote in <qree7q$a6k$1...@gioia.aioe.org>:
>I need a number (~20) of fixed voltages in the range of 4-20V.
>Isolated and non-isolated, for SIC MOSFET gate drivers, 20V for a small
>D class audio amplifier, 3.3V and 5V for logic and 10V for some
>auxiliary circuits. The input voltage is in the range of 10.8-15V,
>maybe 40W in total.
For the boost converter I have this:
https://www.ebay.com/itm/18345275960
cannot make it for 2$28 free shipping, works very well here.
For the lower voltages up to 5A a switcher with LM2596 only takes a few cm^2,
cost very little, even for 20 pieces., using those in several projects.
For isolated gate drive probably with not much current wind some E I core
using good insulated wire .. use a flat cable for multi-turns, 1V/turn.
?
<pete...@neverland.mil> wrote in <qree7q$a6k$1...@gioia.aioe.org>:
>I need a number (~20) of fixed voltages in the range of 4-20V.
>Isolated and non-isolated, for SIC MOSFET gate drivers, 20V for a small
>D class audio amplifier, 3.3V and 5V for logic and 10V for some
>auxiliary circuits. The input voltage is in the range of 10.8-15V,
>maybe 40W in total.
https://www.ebay.com/itm/18345275960
cannot make it for 2$28 free shipping, works very well here.
For the lower voltages up to 5A a switcher with LM2596 only takes a few cm^2,
cost very little, even for 20 pieces., using those in several projects.
For isolated gate drive probably with not much current wind some E I core
using good insulated wire .. use a flat cable for multi-turns, 1V/turn.
?
Piotr Wyderski
Nov 24, 2019, 2:22:05 PM11/24/19
to
jla...@highlandsniptechnology.com wrote:
> Small switchers, like TPS54302, with a cheap stock inductor, are easy.
I like this part, but it solves only the easier part of the problem.
> Small switchers, like TPS54302, with a cheap stock inductor, are easy.
> If your main converter has to make a lot of AC anyway, maybe you can
> couple that into some small transformers to get the low power stuff.
power, using battery backup. So it is simpler to power the smaller
converter from the secondary end of the main LLC.
Best regards, Piotr
Tim Williams
Nov 24, 2019, 4:28:21 PM11/24/19
to
Consider planar -- the resonant thing I showed earlier has pretty good cross
regulation. There's about 10nH between the secondaries.
Toroids are fine too, just a pain to wind. If you're farming them out then
do it however you like. ;D
To get comparable leakage, you will need short winding lengths, and
preferably use twisted pairs or even quads for each winding to keep the
impedance low. Also, TLT techniques don't mind what the core is, it just
needs to up the magnetizing impedance.
Also, don't mind adding LDOs to clean up [cross]regulation, it's just one
more part, not a huge burden.
Also also, you can save some diodes if you use CT windings, which would be a
pain for a hand wound transformer, but is almost free in planar. Just a
PITA to design them...
Tim
--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/
"Piotr Wyderski" <pete...@neverland.mil> wrote in message
news:qree7q$a6k$1...@gioia.aioe.org...
regulation. There's about 10nH between the secondaries.
Toroids are fine too, just a pain to wind. If you're farming them out then
do it however you like. ;D
To get comparable leakage, you will need short winding lengths, and
preferably use twisted pairs or even quads for each winding to keep the
impedance low. Also, TLT techniques don't mind what the core is, it just
needs to up the magnetizing impedance.
Also, don't mind adding LDOs to clean up [cross]regulation, it's just one
more part, not a huge burden.
Also also, you can save some diodes if you use CT windings, which would be a
pain for a hand wound transformer, but is almost free in planar. Just a
PITA to design them...
Tim
--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/
"Piotr Wyderski" <pete...@neverland.mil> wrote in message
news:qree7q$a6k$1...@gioia.aioe.org...
Klaus Kragelund
Nov 24, 2019, 6:38:31 PM11/24/19
to
Hi Tim
Can you post a link to the planar thingie?
Cheers
Klaus
Can you post a link to the planar thingie?
Cheers
Klaus
Tim Williams
Nov 24, 2019, 7:17:49 PM11/24/19
to
"Klaus Kragelund" <klau...@hotmail.com> wrote in message
news:00339865-04e4-43f3...@googlegroups.com...
https://www.seventransistorlabs.com/Images/ResonantSupplySch.png
(mind, proto testing changes not included)
news:00339865-04e4-43f3...@googlegroups.com...
> Hi Tim
>
> Can you post a link to the planar thingie?
https://www.seventransistorlabs.com/Images/ResonantGateDriver.jpg
>
> Can you post a link to the planar thingie?
https://www.seventransistorlabs.com/Images/ResonantSupplySch.png
(mind, proto testing changes not included)
Piotr Wyderski
Nov 25, 2019, 1:45:13 AM11/25/19
to
Tim Williams wrote:
> Consider planar -- the resonant thing I showed earlier has pretty good
> cross regulation. There's about 10nH between the secondaries.
That's really impressive, but I don't see how a planar could host that
> Consider planar -- the resonant thing I showed earlier has pretty good
> cross regulation. There's about 10nH between the secondaries.
many windings.
> Toroids are fine too, just a pain to wind. If you're farming them out
> then do it however you like. ;D
Now it is for a proto, so the winding complexity is not a big issue.
> Also, don't mind adding LDOs to clean up [cross]regulation, it's just
> one more part, not a huge burden.
be regulated).
The plan for this week: grab an LM5041, extract the full glory of it in
the cascaded configuration and see if it suits my needs. Unfortunately,
the built-in drivers are not particularly strong, so MOSFET selection
will be a PITA. It looks promising and I can have SR drive for free
(well, at the cost of even more windings...).
Best regards, Piotr
Piotr Wyderski
Nov 26, 2019, 11:55:13 AM11/26/19
to
Piotr Wyderski wrote:
> but I am considering a different aapproch: a stiff LLC "pump" propelling
> several way-too-good toroidal transformers (primary Lm in the millihenry
> range), connected in parallel. This will allow me to optimize their
> properties to match the requirements of a given rail and keep the number
> of windings within the sane range. Lower inter-winding capacitace of
> unrelated secondaries would be a benefit too. I'll try to make the
> effective primary inductance match the LLC design requirements, but if
> it is too high, I plan to compensate with a parallel choke. Something
> along the lines of the ideal transformer model of an LLC converter, but
> this time the equivalent circuit is taken literally.
>
> Has anybody seen anything like that before? Does it make sense?
Apparently it does make sense, but I wasn't the first who invented
> but I am considering a different aapproch: a stiff LLC "pump" propelling
> several way-too-good toroidal transformers (primary Lm in the millihenry
> range), connected in parallel. This will allow me to optimize their
> properties to match the requirements of a given rail and keep the number
> of windings within the sane range. Lower inter-winding capacitace of
> unrelated secondaries would be a benefit too. I'll try to make the
> effective primary inductance match the LLC design requirements, but if
> it is too high, I plan to compensate with a parallel choke. Something
> along the lines of the ideal transformer model of an LLC converter, but
> this time the equivalent circuit is taken literally.
>
> Has anybody seen anything like that before? Does it make sense?
exactly this combo:
https://patents.google.com/patent/EP3166217A1/zh
LOL! :-)
Best regards, Piotr
Lasse Langwadt Christensen
Nov 26, 2019, 3:57:59 PM11/26/19
to
https://lcsc.com/product-detail/Diodes-General-Purpose_DK5V45R20_C94728.html
Klaus Kragelund
Nov 27, 2019, 6:09:42 PM11/27/19
to
English datasheet:
https://p.globalsources.com/IMAGES/PDT/SPEC/915/K1144395915.pdf
Klaus Kragelund
Nov 27, 2019, 6:11:41 PM11/27/19
to
Jan Panteltje
Nov 28, 2019, 3:06:08 AM11/28/19
to
On a sunny day (Wed, 27 Nov 2019 15:09:36 -0800 (PST)) it happened Klaus
Kragelund <klau...@hotmail.com> wrote in
<930d9eef-b3f9-4ef0...@googlegroups.com>:
>English datasheet:
>
>https://p.globalsources.com/IMAGES/PDT/SPEC/915/K1144395915.pdf
Interesting, always a RC network needed across it?
Kragelund <klau...@hotmail.com> wrote in
<930d9eef-b3f9-4ef0...@googlegroups.com>:
>English datasheet:
>
>https://p.globalsources.com/IMAGES/PDT/SPEC/915/K1144395915.pdf
Interesting, always a RC network needed across it?
Piotr Wyderski
Nov 28, 2019, 4:46:32 AM11/28/19
to
Jan Panteltje wrote:
> Interesting, always a RC network needed across it?
This is a typical RC snubber, often found in synchronously rectified
> Interesting, always a RC network needed across it?
flybacks in order to make the life of the MOSFET bearable.
Best regards, Pior
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