IEEE Power Electronics Magazine - September 2023 - 24

WBG semiconductors can operate
at higher temperatures and
across a wider range of operating
frequencies, which enables systemlevel
power density and operating
performance improvements.
Today's designers can leverage WBG
semiconductors with higher power
ratings in smaller die sizes than competing
technologies, and if similar
electrical power ratings are the goal,
they can leverage WBG semiconductors
with dramatically smaller die
sizes than competing solutions. This
downsizing not only allows designers to achieve significantly
smaller and more economical active device form
factors but also helps make green energy, distributed
power generation, micro grids, and a whole host of other
power generation, distribution, and use scenarios more
attractive and economically feasible.
To support continued advances in WBG semiconductors
and the active devices they enable, both of which
show little to no sign of slowing down, passive component
manufacturers have begun developing advanced product
solutions that are optimized to improve overall circuit
performance in systems equipped with WBG semiconductors.
Two of the most prolific such passive components
are power film capacitors and ceramic capacitors.
Power film capacitors are attractive solutions for WBG
applications for a variety of reasons. Depending on the
type, they:
■ Exhibit controlled self-healing, which makes them impervious
to short circuit failures.
■ Lack a catastrophic failure mode and continue to be
functional after the 5% decrease in capacitance defined
as failure.
Film capacitor
manufacturers have
continued to drive
improved electrode
metallization on ever
thinner film
dielectrics.
■ Are available in can and boardmount
styles and a wide range of
case sizes, voltage and current ratings,
and capacitance values to suit
to support broad application suitability.
■
Are smaller and lighter than competing
solutions, which can result
in decreased device inductance and
improved high-frequency performance.
■
Exhibit high dielectric strength and
high reliability.
■ Offer improved volumetric efficiency
and ease of use.
■ Have high pulse ratings designed to maximize breakdown
voltage.
■ Are available with extended operating temperature ranges
spanning −40 °C to +110 °C, which effectively
overcomes the biggest drawback of power film capacitor
technology.
Power Film Capacitor Advancements
Film capacitor manufacturers have continued to drive
improved electrode metallization on ever thinner film
dielectrics. Today's electrode-coated dielectrics have such
thin metallic electrode layers that if, any dielectric defects
present, the metallization will quickly evaporate and precipitate
onto the cool surrounding electrode material and
effectively isolate the defect, causing only a slight drop in
capacitance. This phenomenon is called self-healing, and
it is an exceptionally attractive feature of film capacitors
since it reliably prevents short circuit failures. A cross
section of polypropylene power film capacitors is shown
in Figure 1, along with a depiction of low- and high-energy
self-healing processes.
FIG 1 Film capacitor self-healing. From top left to bottom right: (1) the cross-sectional structure of a polypropylene power film
capacitor; (2) a dielectric defect; (3) film capacitor self-healing; (4) low-energy self-healing; and (5) high-energy self-healing.
24 IEEE POWER ELECTRONICS MAGAZINE z September 2023

IEEE Power Electronics Magazine - September 2023

Table of Contents for the Digital Edition of IEEE Power Electronics Magazine - September 2023