IEEE Power Electronics Magazine - September 2022 - 96

White Hot
by Robert V. White
Which Came First? Part I
he dilemma of which came
first, the chicken or the egg,
has been debated for millennia.
A more recent debate among
power electronics engineers is which
comes first-innovations in devices
or innovations in circuits? This was,
as I recall, even the topic of a rap at
session at an IEEE Applied Power
Electronics Conference and Exposition
(APEC) a few years back. Semiconductor
device engineers argue
that without advances in new and
improved devices advances in circuits
and topologies would not be
possible. Circuit engineers argue that
the basic nature of the switching
devices has never changed and that
advances in power electronics are all
due to innovations in circuits and
topologies.
So which is it? Are advances in
devices the key to new and improved
power electronics? Or are circuit
advances the key? Even though I am
a circuits, and not a semiconductor
device, engineer I give a slight nod to
the arguments that it has been new
switching devices that have been the
key enabler in the advancement of
power electronics. But the story is
not all that simple. There are other
contributions including advancements
in controls and packaging.
In this column, I will be discussing
the history of power electronics
Digital Object Identifier 10.1109/MPEL.2022.3193858
Date of publication: 28 September 2022
T
with an emphasis on the effect of
each major advance in devices. I am
not going to be real fussy about the
details of who or when. For example,
there are ongoing differences of opinion
over exactly who invented the
IGBT. I won't be worrying about
exactly who published an idea first or
exactly when it was published. I am
more interested in when a particular
advance was actually making a difference
in the world. With most leaps
forward in technology it was rarely a
single person who had some singularly
brilliant idea. Almost universally, it
was contributions of several people
that brought ideas from some initial
seed to widely available and useful
commercial products.
While not strictly power " electronics, "
switch-mode power conversion
using mechanical switches was
developed in the early 19th century
and continued in important commercial
applications into the 1990s. In an
APEC Plenary Session talk several
years ago Rudy Severns described a
French patent from the 1830s. In this
patent was a wooden (insulating)
disc with spokes. As the disc turned,
the spokes caused electrical contacts
to close and then open. When the
contacts opened, inductance in the
wiring would cause an arc that
degraded the contacts. To prevent an
arc, a capacitor was placed across
the contacts making a snubber or as
Rudy described it, the first known
soft switching device.
96 IEEE POWER ELECTRONICS MAGAZINE z September 2022
Electromechanical switching
devices were used starting in the
early 1900s with induction coils to
make a flyback converter. The
switching devices, called vibrators,
were used to increase battery voltages
to the high B+ supply voltages
needed by vacuum tubes. The typical
application for this was radios, either
portable or in automobiles. Such
vibrator-based converters were used
in automobiles until about 1960 when
transistorized radios became widely
used. I still have on my bookshelf a
data book for Mallory vibrators.
Another flyback converter with an
electromechanical switch was used
in vehicle ignition systems. The
switch (the " points " ) was closed and
opened by a cam on a shaft driven
from the engine crankshaft. When
the points closed, the primary of a
flyback inductor (the " ignition coil " )
was connected from the battery to
return. When the points opened, the
secondary of the ignition coil delivered
a high voltage pulse to a spark
plug via a rotary mechanical switch
(the " distributor " ). To prevent arcing
across when the points opened there
was a capacitor (the " condenser " )
connected across the points just as
described in the 1830s French patent.
The duty cycle of the switch closure
( " dwell time " ) was adjusted by varying
the position of the switch assembly
to vary the amount of time the
(continued on page 93)
IEEE Power Electronics Magazine - September 2022

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