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Semiconductors Semiconductors
Figure 1: Forward characteristics of SiC Mosfet and IGBT. SiC
Mosfet behaves similarly to a resistor while an IGBT has a Figure 2: Switching current characteristics of an IGBT Figure 3: Three phase totem pole PFC followed by a full bridge CLLC for bi-directional OBC enabled by SiC Mosfet technology.
fixed 0.7V P-N junction voltage drop. changes with temperature while a SiC Mosfet is constant.
of a similarly sized SiC Mosfet. Figure 2 illustrates frequency rectifiers from the design. This topol-
For almost 20 years, silicon based IGBTs have a typical 0.7V constant voltage drop across the de- current transitions behavior of a SiC Mosfet and ogy also lends itself very well to requirements
been the device of choice in medium voltage vice regardless of the current passing through it. IGBT which shows increasing switching time and for bi-directional power flow where the vehicle
automotive applications between 300V to 1000V. peak current of an IGBT while these two quanti- is required to deliver energy back to the grid in
SiC technology addresses the same automotive In addition, the switching characteristics and ties remain constant for a SiC Mosfet. the future for some regions and municipalities.
applications as IGBTs with benefits such as lower losses of a SiC Mosfet are independent of its chip The converter downstream from the PFC is a
conduction, lower switching losses and higher temperature. As the junction temperature of a The second most important improvement that CLLC DC/DC converter which the vehicle pro-
thermal conductivity compared to IGBT tech- SiC Mosfet increases, its switching loss remains can be gained from SiC technology is on the On pulsion battery is connected. Here, both primary
nology. Figure 1 shows forward characteristics constant allowing a SiC Mosfet to have higher Board Charger (OBC) application of an electrified and secondary sides of the DC/DC converter can
comparison of IGBT and SiC Mosfet. A SiC Mosfet operating current capability than that of an IGBT. vehicle. Here SiC Mosfets will allow for the most benefit greatly from SiC devices. Figure 3 illus-
behaves similarly to a resistor with its voltage For an IGBT increase in junction temperature efficient totem pole Power Factor Correction trates a bi-directional OBC topology enabled by
drop proportional to the current through the will slow down the device which will increase (PFC) topology by eliminating conventional line the introduction of SiC Mosfets.
device. An IGBT is a minority carrier device with a its switching loss further. These phenomena will
P-N junction like behavior similar to a diode with limit IGBT operating current to be lower than that
Figure 4: Infineon innovative packages for OBC application.
24 MAY 2021 | www.powerelectronicsnews.com MAY 2021 | www.powerelectronicsnews.com 25
