Page 20 - EE Times Europe Magazine | June2020

20 EE|Times EUROPE

WIDE-BANDGAP DEVICES
SiC MOSFETs for the Next Generation of EVs

By Maurizio Di Paolo Emilio

n their efforts to maximize energy efficiency in electric
and hybrid vehicles, designers are focusing on devices in
compact packaging and on assembly of high-thermal–
Ireliability, low-switching–loss power electronics modules.
Design parameters take into account the power level, con-
version efficiency, and operating temperature of the vehicle
powertrain system; thermal energy dissipation capacity; and
the system package.

SiC VERSUS GaN
The bandgap of a semiconductor material refers to the
energy needed to knock an electron of the material from the
valence band to the conduction band. Silicon carbide (SiC)
and gallium nitride (GaN) are wide-bandgap (WBG) semi-
conductors, meaning this energy level is higher for those
materials than it is for silicon vice president and general manager of Power at Cree. “Global OEMs
SiC power electronics (Si): Si’s bandgap is have announced more than US$300 billion in EV investments, and we
for EVs meet the design 1.1 eV, compared with 3.3 eV expect a projected 20% of all model types manufactured to be electri-
fied within the next 10 years.”
for SiC and 3.4 eV for GaN.
Despite the similar
GaN performance and reliability are related to temperature and
requirements for high- bandgaps of SiC and GaN, the Joule heating effect on the channel. Substrates such as SiC and
power applications, components based on those diamond integrated into GaN can improve heat management, making it
thus contributing materials are not inter- possible to lower the operating temperature of the device.
GaN-on-SiC works very well for very high-frequency (RF) applica-
changeable, and a designer’s
significantly to system choice of material will differ tions and thus is expected to serve future devices that will work with
5G. GaN-on-Si, meanwhile, maintains its place in low-voltage (<200-V)
according to the parame-
performance and long- ters of use for the systems products such as compact USB Power Delivery (PD) chargers. In the
term reliability. in which the devices will range between 600 V and 650 V, both technologies work very well in
operate.
sub-2-kW applications.
SiC-enriched power elec- Because of its excellent performance in minimizing switching losses,
tronics for electric vehicles (EVs) meet the design parameters required GaN can be the right solution when switching frequencies in the mega-
in high-power applications and thus contribute significantly to sys- hertz range are required. But at increased switching frequency and
tem performance and long-term reliability. “The adoption rate in the current values, GaN’s weak resistance (2× to 3× greater than SiC’s) can
electric-vehicle industry has been tremendous,” said Jay Cameron, limit GaN’s application at high temperatures in terms of both device
and system cost.
“Due to the massive adoption of silicon carbide in the automotive
industry, we see a path for silicon carbide to become the most cost-
effective solution in an even wider variety of power supply designs,”
said Cameron. “Silicon carbide is a key solution for on-board chargers
[OBCs]. The power-density and -efficiency improvements over silicon
implementations enable a strong reduction in terms of volume and
weight [Figure 1].”
Cree’s products “enable bidirectional OBC designs that support the
V2x [vehicle-to-vehicle or vehicle-to-grid] trend,” Cameron added.
“With our portfolio of devices at 1,200 V and 650 V, we are able to
meet the requirements for both 800-V and 400-V electric vehicle
architectures.”
CREE’S SOLUTIONS
With the release of its Wolfspeed 650-V silicon carbide MOSFETs, Cree
is targeting a broader range of industrial applications. Target markets
include EVs, data centers, and renewable energy.
“There is an array of applications that can benefit from Cree’s new
650-V MOSFETs,” Cameron said. “Electric vehicles and data centers are
two areas that can see huge benefits from the technology that primarily IMAGE: SHUTTERSTOCK
stem from its high-efficiency, high-power-density traits. Compared
Figure 1: Reducing total system cost in a 6.6-kW bidirectional with silicon alternatives, you can see half the conduction losses,
on-board charger design (Image: Cree/Wolfspeed) 75% lower switching losses, and 70% greater power density [Figure 2].

JUNE 2020 | www.eetimes.eu