IEEE Power Electronics Magazine - September 2021 - 100

White Hot
by Robert V. White
Will a Computer Design
Your Next Transformer?
I
nductors and transformers are
vital to most every switch mode
power converter. Inductors store
and release energy as the switching
cycle progresses. Transformers convert
voltages and currents from one
value to another. Transformers also
provide the galvanic isolation needed
to make our converters safe. Yes,
I know that switched capacitor converters
are developing rapidly (see
my column on capacitive power conversion
" Taking a Look at Capacitive
Power Conversion, " IEEE Power
Electronics Magazine, December
2017, p.90) but the best switched
capacitor converters use inductors
to create resonant transitions from
state to state. Magnetics will be at
the heart of switch mode power converters
for the foreseeable future.
The design of magnetics is a real
challenge for power electronics engineers.
To get a good design means
finding the right combination of core
material, core shape, bobbin/coil former,
winding layup, winding wire or
foil, insulation, and terminations.
This makes even a one winding
inductor a complex multidimensional
optimization problem. For a young
power electronics engineer just starting
out designing a good transformer
can be an overwhelming problem. As
we gain experience, I think we tend
to find solutions that have worked
Digital Object Identifier 10.1109/MPEL.2021.3100595
Date of current version: 13 September 2021
and use them again and again. But, I
also think that because we " get into a
rut " we tend to miss opportunities to
make significant improvements.
Given that magnetics design is a
multidimensional optimization problem,
it would seem creating a computer
algorithm to do the design would
be straight-forward. This has been
explored quite a bit. The 2020 Power
Magnetics Workshop, sponsored by
the Power Sources Manufacturers
Association (PSMA) and IEEE Power
Electronics Society (PELS), featured
several talks on automating magnetics
design. Commercial solutions
available to power electronics engineers
have been limited but there is
real progress being made.
The simplest kind of magnetics
design automation is what I call
" parts pickers " . These solutions allow
the design to enter some basic specifications
and then present one or more
off-the-shelf solutions that could
work. A good example of is Wurth
Electronics REDEXPERT. These
kinds of solutions can quickly get a
designer to a part that will work.
These kinds of tools can often provide
basic circuit design information,
such as range of duty cycles, peak and
rms currents, and the expected core
and winding losses based on the
application information. The advantage
here is that the designer can get a
part quickly from distribution and
get a circuit up and working with
minimal delay. The tradeoffs are that
100 IEEE POWER ELECTRONICS MAGAZINE z September 2021
these tools are vendor specific and
don't offer any chance for customization
or optimization.
The next level is tools that will do a
custom design. An example is Magnetics
Inc.'s online inductor design. With
this tool, one chooses core shape
(toroid or E-core) and a core material
(which requires the user to be familiar
with the various core materials
offered by Magnetics Inc.). Then the
user enters peak, ripple, and dc currents,
switching frequency, and allowable
temperature rise. With this information,
the tool returns cores that can
be used to meet the requirements.
Choosing a core then returns design
information such as the inductance at
no load, inductance at maximum current,
losses, number of turns, wire
size, dc resistance, and expected temperature
rise. The tool offers some
capability to adjust the design and the
new results. This is a useful tool if one
is designing a simple inductor.
There are tools available that go
way beyond these basic capabilities.
Ridley Engineering, SIMPLIS Technologies,
and Frenetic all gave me a
limited time evaluation license to
explore their magnetics design and
analysis capabilities. This allow -
ed me to " test drive " their offerings
myself instead of relying only on
these company's promotional literature.
None of these companies had
any input to what I wrote and will not
(continued on page 97)
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