IEEE Power Electronics Magazine - June 2022 - 70

quadrant switch: SiC BiDFET (Figure 2), characterization of
SiC BiDFET, applications of BiDFET for vehicle electrification,
and experimental results of SiC BiDFET enabled gridconnected
PV converter. This paper indicated that the SiC
BiDFET was a monolithic device (1200 V, 20 A) that offered
lower conduction voltage drop and higher switching frequency
for CSI and direct ac-ac matrix or cyclo converter
based power conversion systems. A 2.1 kW, 1-phase grid connected
converter prototype enabled by 1200 V, 20 A SiC BiDFET
was discussed in this paper.
In a joint paper (#S09) titled " Wide-Bandgap Bidirectional
Switches and Their Impact on Future AC Power Converters
and Applications, " researchers from NCSU, ETH Zurich, and
WEMPEC University of Wisconsin-Madison, presented WBG
based technology of monolithic bidirectional (M-BD) switches
and the performance improvement they bring to matrix converters
and CSIs, including CSI based integrated motor drives
(see " The Incredible Shrinking Motor Drive " by Thomas M.
Jahns and Bulent Sarlioglu, IEEE Power Electronics Magazine,
September 2020, p.18). Similarly, Transphorm is also
developing a 600 V GaN based four-quadrant M-BD switch.
Preliminary details were presented in a paper titled " GaN Four
Quadrant Switches: Ready for Prime Time? " This paper was
presented in the Industry Session (IS02.3) by Dr. Rakesh Lal,
Technical Fellow and principal scientist at Transphorm.
GaN FETs and Technologies
Soon after the plenary session, the exposition was officially
opened to attendees, and about 198 companies demonstrated
their cutting-edge products and technologies for a wide range
of applications over the next two days. Wide bandgap (WBG)
Four-Terminal Monolithic BiDFET Circuit Schematic
G2
G1
JBSFET-2
JBSFET-1
devices dominated the show and it was evident that both gallium
nitride (GaN) and silicon carbide (SiC) based power
transistors were making rapid progress in terms of adoption
in mainstream applications. Although, consumer electronics,
datacenters, automotive, industrial, medical and renewable
energy applications were initial targets for WBG devices,
space is the next frontier for them.
In the wide bandgap arena, several new entrants demonstrated
their respective capabilities in GaN technologies.
U.K. based fabless semiconductor company Cambridge GaN
Devices Ltd (CGD) was one of them to launch the 650 V ICeGaN
HEMTs with the ability to operate like a MOSFET. As
a partner in the European GaNext project, consisting of 13
companies, it will be supplying its 650 V GaN devices to create
an intelligent power module (IPM) comprising the controller,
driver and protection circuits, all co-packaged with the power
GaN devices. (Figure 3)
T2
T1
FIG 2 SiC-based bidirectional FET schematic. Source: IEEE
APEC 2022.
dc-Link
High-Side
GaN HEMT
Gate
Driver
RISC-V
Placeholder
FIG 3 A photo of GaNext's IPM before encapsulation. It comprises
controller, driver, protection circuit, and 650 V GaN HEMTs.
70 IEEE POWER ELECTRONICS MAGAZINE z June 2022
Capacitors
According to CGD, the first GaNext IPM is assembled and
ready for testing and encapsulation. It contains the half-bridge
power stage with ICeGaN 650 V HEMTs and employs individual
heat spreaders on top of the transistors to improve power
dissipation. Also, the GaN transistors are driven by Infineon's
silicon-on-insulator (SOI) gate drivers at high switching frequencies,
while the controller is RISC-V from Fraunhofer.
Likewise, Tagore Technology demonstrated several reference
designs using its 650 V GaN HEMT with integrated driver.
They include 65 W active clamp flyback (ACF) ac-dc converter,
65 W quasi-resonant flyback (QRF) ac-dc converter, and 240 W
totem-pole PFC (TPFC) + LLC ac-dc converter.
Unlike others using lateral structure, NexGen Power systems
is betting on vertical technology. Utilizing its patented
vertical GaN-on-GaN technology, the company has developed
a 1200 V GaN HEMT with robust avalanche capability
and >10 µs short-circuit protection rating. In addition,
based on its vertical GaN FET, it has also crafted a power
platform for developing power systems for a variety of
applications. Called Merlin Power Engine, it incorporates
novel power management algorithm, including software
controllable proprietary controller, advanced magnetics
and thermal management. The platform allows vertical GaN
devices to switch at frequencies above 1 MHz. Utilizing its
vertical GaN FET, NexGen Power Systems demonstrated
a 240 W gaming power supply with unprecedented power
density and efficiency.
Another GaN supplier readying 1200 V FETs is Transphorm.
The manufacturer claims that the 1200 V GaN device
delivers greater than 99% efficiency and performs well
against a leading SiC MOSFET of similar on-resistance. Partially
funded by the ARPA-E CIRCUITS program, the company
is developing the technology for EV mobility and infrastructure
power systems as well as industrial and renewable
energy systems. The initial 1200 V GaN device in a TO-247
package offers an RDS(on) of 70 mΩ and easily scales to lower
resistance and higher power levels, said the supplier. Transphorm
said the 1200 V GaN FET will be sampled in 2023, and
will be in direct competition with SiC MOSFETs.
IEEE Power Electronics Magazine - June 2022

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