Page 19 - EE Times Europe Magazine | June2020

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OPINION | WIDE-BANDGAP DEVICES
rapid replacement of silicon IGBTs and
SiC Technology for MOSFETs with the new SiC alternatives.
In contrast, devices built with another
wide-bandgap semiconductor, gallium
Electric Vehicles nitride (GaN), have better results with
surface-mount–device (SMD) formats. While
SMDs are lighter and smaller, they cannot
serve as swap-in replacements, relegating
By Maurizio Di Paolo Emilio their use to new projects.

Silicon carbide devices
There is an opportunity for remarkable growth in the market
for hybrid and electric vehicles (H/EVs), but we must innovate our can help sell the driving
way past some technological barriers on the sustainable-mobility
landscape if we hope to see electrically powered vehicles become public on the efficiency of
commonplace on European roads. Much of the public still needs to electromobility and put more
be persuaded of the efficiency of electromobility. Toward that end,
several car manufacturers are working on fast-charging systems hybrids and EVs on the road.
aimed at facilitating the use of electric cars. Wide-bandgap semicon-
ductor silicon carbide (SiC) is central to those efforts.
DC fast-charging stations are an interesting field of application for SiC modules. To achieve Infineon offers a pair of power mod-
the ambitious goals on power density and system efficiency that are being set by industries ules that can be used in combination for
and governments, SiC transistors and diodes are needed. But developers must ensure a correct 50-/60-kW EV charging solutions. The
approach to the fast-charging system, with sufficient insulation and appropriate modularity. Easy 1B (F4-23MR12W1M1_B11) inte-
Battery charging is a mostly constant-current application with a low demand for dynamic grates a four-pack topology for the DC/DC
power. The main trend here is attaining the highest possible efficiency throughout the battery stage of the charging station. The Easy 2B
charge cycle. Today, 15- to 20-kW units use discrete components in 19-inch × 3U × 800-mm (F3L15MR12W2M1_B69) has a three-stage
modules with forced-air cooling. New infrastructure is targeting DC chargers exceeding 350 kW, configuration that is well suited for the
leading to the use of liquid cooling to enable a power growth increase per sub-unit to Vienna Rectifier, which is common for the
60 to 75 kW in even smaller form factors. power-factor correction (PFC) stage in this
The power supply blocks of the charger consist of an AC/DC front end followed by a DC/DC application. The modules use Infineon’s
converter to provide the charging voltage to the battery. The AC/DC section converts the power CoolSiC diodes, rugged and efficient devices
supply from the distribution network to a useful DC voltage, avoiding ripple fluctuations. The that were designed to meet requirements
DC/DC converter provides electrical isolation from the vehicle chassis for safety reasons while for use in hybrid and electric vehicles. An
providing the necessary DC-charging voltage to the vehicle. improvement on Infineon’s last-generation
By replacing silicon-based designs using IGBTs or MOSFETs in the AC/DC block of the charger Schottky diodes, the CoolSiC diodes have bet-
with SiC devices, the circuit design is simplified while the power density and, hence, the effi- ter figures of merit, minimizing power losses.
ciency are significantly increased, enabling reductions in parts count and in system size, weight, The use of SiC in the drivetrain also ensures
and cost. greater efficiency and, by extension, vehicle
With a simple change in the control software, the SiC block can also enable the bidirec- autonomy. AC Propulsion took advantage of
tionality needed to allow the vehicle battery to become part of a smart grid. Enabling such high-performance SiC FETs to hit all the sys-
bidirectionality with a silicon solution would require the use of more hardware in a far more tem power targets for an EV traction inverter
complex circuit design. design. The company designed in UnitedSiC’s
Because the TO-247 and TO-220 formats can be used for packaging, SiC devices also enable UF3SC120009K4S, a 1,200-V, 9-mΩ SiC FET
delivering improved efficiency over compet-
ing SiC devices in three-phase AC traction
inverters for EVs. The devices returned >99%
efficiency in AC Propulsion’s design, even
when switching at frequencies of >20 kHz and
at 2× the frequency of IGBTs.
The UF3SC120009K4S is packaged in the
TO-247 format, making it a cost-effective
drop-in replacement for silicon equivalents.
Its efficiency allows the use of a self-
contained heat sink.
The SiC projects and devices discussed
here demonstrate the progress being made on
IMAGE: SHUTTERSTOCK will gain consumer confidence for improving
increased efficiency. Over time, such advances

EV technology. ■
Maurizio Di Paolo Emilio is a staff
correspondent at AspenCore, editor of Power
Electronics News, and editor-in-chief of EEWeb.

www.eetimes.eu | JUNE 2020