Investigation of Emerging Power Electronics Technologies in EV Applications

Due to the reduced fuel usage and greenhouse emission advantage, the sales of electric vehicles (EV) have risen dramatically in recent years. Generally speaking, the EVs are pursuing higher power and lighter weight, which requires higher power density for all the power electronics converters in the EVs. To design higher density power converters, three key emerging power electronics technologies are investigated in this study. First, the PCB-based magnetics are beneficial for improving the power density due to their low-profile structure. However, the high winding capacitance is considered one of the significant drawbacks of PCB-based magnetics. In this study, a novel winding structure is proposed to cut down the winding capacitance by 75% with little compromise of the winding loss. Second, the synchronous rectifiers (SR) are usually utilized to improve the system efficiency and power density compared with the conventional diode bridge rectifiers for the AC/DC stage in the power converters. The SRs are desired to be turned off at current zero-crossing to generate a minimal loss. However, the precise current zero-crossing detection is very challenging in high-frequency and high-power-density converters. In this study, a high-dv/dt-immune and parameter-adaptive SR driving scheme is proposed to guarantee the zero-current switching (ZCS) of SRs in various operating conditions and improve the system efficiency by 1.23%. Finally, Gallium Nitride (GaN) semiconductors are considered less lossy than Silicon (Si) semiconductors. However, the voltage rating of the commercial GaN HEMTs is limited to 600/650 V due to the lateral structure, which is not suitable for the 800 V or higher dc-link voltage EV systems. Stacking the low-voltage rating devices is a straightforward approach to sustain higher dc-link voltage. However, unbalanced voltage sharing can occur, which can damage the low-voltage rating devices in the stack. In this study, a novel active current source gate driver is proposed to suppress the over-voltage of the stacking devices below 10% for all operating conditions without sacrificing switching speed or switching energy. The above emerging power electronics technologies are investigated thoroughly in the dissertation. The proposed approaches are practical for improving power converters’ density in future EV applications.