Discrete silicon carbide (SiC) MOSFETs are usually connected in parallel to increase their current carrying capacity. However, unequal switching losses and unequal transient current overshoot can limit the maximum switching frequency and maximum current carrying capacity of the paralleled unit. In this paper, a paralleled half-bridge unit is proposed to improve transient current sharing performance, which is characterized by a distributed arrangement of dc capacitors. Firstly, the main causes of transient current imbalance in traditional power layout are analyzed theoretically for the first time. Then, the traditional power layout is optimized by the AnsysEM co-simulation techniques to improve transient current sharing performance. The layout of gate driver is also optimized to reduce the transmission delay of gate drive signal. The double pulse tests are carried out to verify the current sharing performance under normal and short circuit operating conditions. Compared with traditional power layout, the difference in transient current overshoot of the low-side paralleled SiC MOSFETs is decreased significantly from 10.22% to 2.78% and the difference in switching losses is also reduced. A boost converter is constructed based on the paralleled half-bridge unit. A more uniform temperature distribution indicates the improved current sharing performance by optimizing the power layout.

This paper investigates the conducted electromagnetic interference (EMI) characteristics of an on-board multiplexing converter that utilizes paralleled silicon carbide (SiC) devices to achieve high efficiency and high-power density for the application in electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs). The multiplexing converter can operate as a three-phase interleaved DC/DC converter with a peak output power of 60 kW or an integrated two-stage non-isolated on-board charger (OBC) with an output power of 6.6 kW. The novelty of this paper is that it reveals that in the DC/DC mode the series resonance between the input negative lead parasitic inductance and the high frequency transmission line effects of the input power inductor will increase the conducted EMI levels, which can be mitigated by optimizing the winding methods of the power inductor or by adding a small capacitor, and reveals that in the non-isolated OBC mode the shielded cable on the battery-side will increase the grid-side EMI in the low frequency ranges, which can be suppressed by integrated installation of EMI filters without affecting the system power density. Firstly, parasitic parameters of the components of the multiplexing converter, such as the power inductors, the SiC MOSFETs and the shielded cables, are extracted and validated with impedance measurements, and the corresponding equivalent circuit models are established. Then, the conducted EMI simulation models of the multiplexing converter in different working modes are established. The influence of different interference sources and different parasitic parameters on the system EMI characteristics are analyzed, and the effective EMI suppression measures are given without affecting the system power density. Finally, the conducted EMI characteristics of the multiplexing converter and the effectiveness of the proposed EMI suppression measures are tested and verified through experiments.