Design Challenges of SiC Devices for Low- and Medium-Voltage DC-DC Converters

Abstract

Silicon carbide (SiC) devices are considered as key enablers for the development of highly efficient and compact dc-dc converters for low-and medium-voltage applications. Besides their high temperature capability and low conduction losses, they provide superior switching characteristics. This paper emphasizes the design challenges of SiC devices in the low-and medium-voltage ranges arising from their fast switching speeds. First, detailed measurement results on the switching characteristics of 1200 V SiC devices and the different leakage inductances are presented. The results are assessed with regard to the switching losses as well as the transient voltage and current overshoots. The impact on the switching behavior as a function of leakage inductances is shown. The leakage inductances also influence the resonance frequency of the power module and dc-dc converters. The determination of the size of the EMI filters is a crucial design aspect. Its significance is demonstrated using an 800 V dc-dc converter with commercially available SiC MOSFETs. In addition, zero-voltage switching is emphasized to reduce the impact of the parasitic elements of the module on the switching behavior. However, the performance of 10 kV SiC MOSFETs in a medium-voltage dc-dc converter shows that a significant amount of commutation energy is required to ensure a successful soft-switching transition.

Simulation Study of the Small-Signal Characteristics of Single-Phase Common-Mode Inductors with Capacitance Cancellation

“…Lately, power semiconductor devices made from silicon carbide (SiC) have entered the market and are being utilized in numerous applications [1][2][3][4]. These SiC-based power devices can complete switching operations ten times faster than their traditional silicon-based counterparts.…”

“…As a result, by enhancing the switching frequency of power converters, there is the potential to minimize the size of passive components. Conversely, the significant dv/dt and di/dt associated with SiC devices contribute to a rise in high-frequency electromagnetic interference (EMI) in power converters [4][5][6][7]. Consequently, implementing EMI filters is essential to achieve substantial noise reduction across a broad frequency range.…”

Experimental Study of Radiated Emission Due to Secondary Common-Mode Current in Buck Converters

“…Stateof-the-art wide-bandgap power semiconductor devices realize high power density because their fast-switching speed can increase the switching frequency of power converters [3]. However, as a side effect of using wide-bandgap semiconductors such as silicon carbide and gallium nitride, electromagnetic emission increases significantly even above several tens of MHz [4][5][6][7]. Thus, the practical use of wide-bandgap power devices raises concern about increased radiated emissions in power converters.…”

Design of an Integrated Air Coil for Current Sensing

“…According to [10], the current sensors used for overcurrent protection require a short propagation time delay and high current sensor density (A/m 3 ). Such current sensors require at least 100-MHz bandwidth because the frequency components of the bus-bar current are up to dozens of MHz [11]- [13]. However, it is difficult to use conventional current sensors [14] in recent power converter circuits because the power circuit layout should be modified and stray inductance increases significantly, which is undesirable for WBG devices.…”