Good Transformer Design primer

[Martin Riddle]

Can anyone point me in the right direction to either a web site or text for transformer design?
I have some experiance, but there are a few things that still stump me.
(low freq, and high freq, pulse would be good too)

TIA,

Martin

 

[Allen Windhorn]

Can anyone point me in the right direction to either a web site or
text for transformer design? I have some experiance, but there are
a few things that still stump me. (low freq, and high freq, pulse
would be good too)

"Electronic Transformers and Circuits," Reuben Lee
"Transformers for Electronic Circuits," Nathan Grossner

(for smaller transformers)

Regards,
Allen

 

[Fritz Schlunder]

Can anyone point me in the right direction to either a web site or text for transformer design?
I have some experiance, but there are a few things that still stump me.
(low freq, and high freq, pulse would be good too)

TIA,

Martin

Texas Instruments' "Magnetics Design Handbook" is pretty comprehensive.
They have both a PDF version of all the info as well as narrated slides
available using TI's online training service (both are free).

Go here to get the goods:

http://focus.ti.com/docs/training/catalog/events/event.jhtml?sku=SEM401014

The single most important formula to know (IMO) is the following:

(Winding Turns)=(Volts Applied)/[2*(Frequency)*(Core cross sectional
area)*(delta B max)]

All units in SI quantities, and this formula applies to transformers that
will be seeing squarewaves (it is ever so slightly different for sinusoids,
the factor "2" appearing in the denominator is slightly larger). This
formula tells you basically how many turns a given winding will need on your
core to prevent core saturation. Delta B max is the maximum flux density
swing your convertor will be operated with. For half bridges and full
bridges this can be as much as 2X the saturation flux density of your core
(although in real applications it is often beneficial to use a much smaller
limit). For forward converters this is at most only 1X the saturation flux
density of the core. This formula does not apply for flyback transformers.

 

[Winfield Hill]

Allen Windhorn wrote...

"Electronic Transformers and Circuits," Reuben Lee
"Transformers for Electronic Circuits," Nathan Grossner
(for smaller transformers)

I'd add the classic book: "Soft Ferrites," by E.C. Snelling

There're a few good tutorials on the web for designing PWM
SMPS switcher power-supply transformers, such as the TI web
site, where fine stuff from the classic Unitrode Seminars
collection is online. There you can find two Dixon articles
on magnetic-core models in slup109 and slup128 (the latter
also has other articles). I have a 12MB file in my computer
called sem_magnetics_design.zip, which contains Lloyd H.
Dixon's lengthy article: Magnetics Design for Switching Power
Supplies (in slup123 through slup127), plus slup 128.

Thanks,
- Win

whill_at_picovolt-dot-com

 

[Martin Riddle]

Thanks all.
I had heard Unitrode had great tech info, didnt know magnetics was among it.
I'll check the TI web site.
You mentioned Flux Density, I allways had difficulty understanding where this number came from.
I was told to use 3kgause for Ferrite ( if I remember right) and this number could change as
personal perference dictated.
I guess this should be in some text somewhere.


Cheers

Can anyone point me in the right direction to either a web site or text for transformer design?
I have some experiance, but there are a few things that still stump me.
(low freq, and high freq, pulse would be good too)

TIA,

Martin

Texas Instruments' "Magnetics Design Handbook" is pretty comprehensive.
They have both a PDF version of all the info as well as narrated slides
available using TI's online training service (both are free).

Go here to get the goods:

http://focus.ti.com/docs/training/catalog/events/event.jhtml?sku=SEM401014

The single most important formula to know (IMO) is the following:

(Winding Turns)=(Volts Applied)/[2*(Frequency)*(Core cross sectional
area)*(delta B max)]

All units in SI quantities, and this formula applies to transformers that
will be seeing squarewaves (it is ever so slightly different for sinusoids,
the factor "2" appearing in the denominator is slightly larger). This
formula tells you basically how many turns a given winding will need on your
core to prevent core saturation. Delta B max is the maximum flux density
swing your convertor will be operated with. For half bridges and full
bridges this can be as much as 2X the saturation flux density of your core
(although in real applications it is often beneficial to use a much smaller
limit). For forward converters this is at most only 1X the saturation flux
density of the core. This formula does not apply for flyback transformers.

 

[Active8]

Thanks all.
I had heard Unitrode had great tech info, didnt know magnetics was among it.
I'll check the TI web site.
You mentioned Flux Density, I allways had difficulty understanding where this number came from.
I was told to use 3kgause for Ferrite ( if I remember right) and this number could change as
personal perference dictated.
I guess this should be in some text somewhere.

you mean saturation flux density.

if you google on "Producing wound components", you'll find a site that
may explain this. i e-mailed the author and he zipped that part of the
site up for me (possibly the whole "ESU advisor" site - you can search
on that, too), but he didn't put the link up. he mentioned that he might
leave it up if more requests came in. i'd post it to binaries group but
it's not my site to do that with.

anyway... this will help explain things. i think you'll find an
explaination of how AsubL values are computed for cores. then you can
check the amidon (or whoever) site for AsubL values and saturation flux
densities. IIRC the latter is in graph form. you have your work cut out
for you AFAIC, but you'll learn a lot. theres info on mfg sites for
switchers and magnetics companies.

hope this helps,
mike

Cheers

Can anyone point me in the right direction to either a web site or text for transformer design?
I have some experiance, but there are a few things that still stump me.
(low freq, and high freq, pulse would be good too)

TIA,

Martin

Texas Instruments' "Magnetics Design Handbook" is pretty comprehensive.
They have both a PDF version of all the info as well as narrated slides
available using TI's online training service (both are free).

Go here to get the goods:

http://focus.ti.com/docs/training/catalog/events/event.jhtml?sku=SEM401014

The single most important formula to know (IMO) is the following:

(Winding Turns)=(Volts Applied)/[2*(Frequency)*(Core cross sectional
area)*(delta B max)]

All units in SI quantities, and this formula applies to transformers that
will be seeing squarewaves (it is ever so slightly different for sinusoids,
the factor "2" appearing in the denominator is slightly larger). This
formula tells you basically how many turns a given winding will need on your
core to prevent core saturation. Delta B max is the maximum flux density
swing your convertor will be operated with. For half bridges and full
bridges this can be as much as 2X the saturation flux density of your core
(although in real applications it is often beneficial to use a much smaller
limit). For forward converters this is at most only 1X the saturation flux
density of the core. This formula does not apply for flyback transformers.

 

[Martin Riddle]

Thanks, Thats a great site. lots of info, all in one place.


Cheers

Thanks all.
I had heard Unitrode had great tech info, didnt know magnetics was among it.
I'll check the TI web site.
You mentioned Flux Density, I allways had difficulty understanding where this number came from.
I was told to use 3kgause for Ferrite ( if I remember right) and this number could change as
personal perference dictated.
I guess this should be in some text somewhere.

you mean saturation flux density.

if you google on "Producing wound components", you'll find a site that
may explain this. i e-mailed the author and he zipped that part of the
site up for me (possibly the whole "ESU advisor" site - you can search
on that, too), but he didn't put the link up. he mentioned that he might
leave it up if more requests came in. i'd post it to binaries group but
it's not my site to do that with.

anyway... this will help explain things. i think you'll find an
explaination of how AsubL values are computed for cores. then you can
check the amidon (or whoever) site for AsubL values and saturation flux
densities. IIRC the latter is in graph form. you have your work cut out
for you AFAIC, but you'll learn a lot. theres info on mfg sites for
switchers and magnetics companies.

hope this helps,
mike

Cheers

Can anyone point me in the right direction to either a web site or text
for transformer design?
I have some experiance, but there are a few things that still stump me.
(low freq, and high freq, pulse would be good too)

TIA,

Martin


Texas Instruments' "Magnetics Design Handbook" is pretty comprehensive.
They have both a PDF version of all the info as well as narrated slides
available using TI's online training service (both are free).

Go here to get the goods:

http://focus.ti.com/docs/training/catalog/events/event.jhtml?sku=SEM401014

The single most important formula to know (IMO) is the following:

(Winding Turns)=(Volts Applied)/[2*(Frequency)*(Core cross sectional
area)*(delta B max)]

All units in SI quantities, and this formula applies to transformers that
will be seeing squarewaves (it is ever so slightly different for sinusoids,
the factor "2" appearing in the denominator is slightly larger). This
formula tells you basically how many turns a given winding will need on your
core to prevent core saturation. Delta B max is the maximum flux density
swing your convertor will be operated with. For half bridges and full
bridges this can be as much as 2X the saturation flux density of your core
(although in real applications it is often beneficial to use a much smaller
limit). For forward converters this is at most only 1X the saturation flux
density of the core. This formula does not apply for flyback transformers.