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This article introduces a holistic and systematic design methodology tailored to the 10 kV silicon carbide (SiC) mosfet power modules. Multiobjective optimization was achieved with enhanced electric-field (E-field) distribution, minimized common-mode (CM) parasitic capacitance, and reduced system-level parasitic inductances. The proposed approach encompasses two innovative techniques: 1) an electric-potential-oriented module-system interface to reduce system-level parasitic inductance while maximizing insulation capability; 2) stacked substrates with patterned middle layer copper to alleviate the E-field concentration at the triple-point and reduce the maximum E-field without compromising on thermal resistance. The effectiveness of these innovative approaches is substantiated through the development of a 10 kV SiC mosfet power module. The optimized layout presents well-balanced 5.6 nH power loop inductance with embedded decoupling capacitors and record-low 28 pF CM parasitic capacitance, attributed to the middle layer pattern structure. In addition, a 38.6% E-field concentration reduction at the triple-point is identified compared to conventional stacked substrates. Experimental validation showcases its robust voltage insulation capability with a leakage current of 0.87 μA at 10 kV, a 33 kV dc, and 25 kV ac surface flashover for worst-case system fault conditions. The partial discharge inception voltage of the proposed middle layer patterned stacked substrates is verified at 16.8 kVrms. Dynamic performance validation through a double-pulse test at 5 kV showcases negligible ringing and voltage overshoot. All these exceptional attributes position the packaged 10 kV SiC mosfet power module as an exemplary choice for MV power electronics applications.

LLC resonant dc/dc converters are widely applied in various scenarios, such as electronic device power supplies, vehicle chargers, etc. To improve the efficiency of the LLC converter, synchronous rectifiers (SR) are employed. However, due to various reasons, such as the hardware propagation delay, the SR gate signal can lag behind the secondary-side current particularly when the switching frequency of the LLC converter approaches the mega-Hertz level. This delay has a critical impact on the operation mode and the output characteristic of the LLC converter. Starting with the SR delay mechanism, this article comprehensively analyzes the operation of the LLC converter and derives the time-domain model under SR signal delay. The output gain and accurate power loss model of MOSFETs under different working modes are built to study the impact of SR signal delay on the LLC converter. The relationship between the SR signal delay and the LLC converter characteristics is quantified and summarized. Two new working stages of the LLC converter are revealed. Simulation and experimental studies are conducted to validate the theoretical analysis results. This article can provide the theoretical basis for optimizing the design of a high-frequency LLC converter.

Cryogenic power electronics is regarded as the next step to improve the converter efficiency and power density. It is advantageous in many different applications, including aerospace, renewable energy, transportation and so on. Among all different semiconductors, gallium nitride (GaN) was found more advantageous with significant loss reduction at cryogenic temperature. In this paper, overcurrent test is performed and analyzed for a high-efficient commercial GaN high electron mobility transistor (HEMT). The experimental results demonstrate a significant improvement of the device overcurrent capability at cryogenic temperature (from 160 A at room temperature to 250 A at cryogenic temperature). The operating mechanisms behind the overcurrent test are investigated and discussed. Finally, a 5 kW GaN HEMT based cryogenic Buck converter is built and tested. Maximum efficiency of 98.5% is achieved at 1.5 kW output power and around 1% efficiency improvement can be achieved when compared to room temperature operation. Another GaN HEMT based four-switch Buck-boost converter is evaluated at cryogenic temperature, maximum efficiency improvement of 1.5% is observed when compared to room temperature.

We report for the first time on an aluminum nitride/gallium nitride (AlN/GaN) heterostructure as a microscale Hall effect sensor for current sensing applications in extreme environments. The AlN/GaN devices demonstrated high signal linearity as a function of the magnetic field across a temperature range from -193 °C to 407 °C. The measured room temperature (RT) supply voltage-related sensitivity ( ${S}_{\text {svrs}}{)}$ and supply current-related sensitivity ( ${S}_{\text {scrs}}{)}$ are 0.055 T-1 and 32 AV-1T-1, respectively. The supply power-related sensitivity ( ${S}_{\text {sprs}}{)}$ is 1.4 VW-1T-1 above 40-mW input bias, which is higher than that of the Al0.2Ga0.8N/GaN device. The designed AlN/GaN micro-Hall sensor is further determined to have a lower power consumption and higher temperature sensitivity than equivalent Al0.2Ga0.8N/GaN Hall devices. When operated in an ac bias mode, the rise time of the Hall sensor was found to be 102 ns, corresponding to a frequency bandwidth of 9.8 MHz. We also observed a phase shift between an applied magnetic field and the Hall sensor signal, which can potentially be helpful to monitor ac line currents.

In this article, a high-temperature optical galvanic isolator was developed. Details on the packaging layout, LED to emitter configuration, mathematical models, and device integration in the circuit are discussed. Evaluation of other optical isolation techniques is characterized and compared. The designed package for the low-temperature cofired ceramic-based (LTCC-based) optocoupler results in a higher electrical performance showing better signal stability and current transfer ratio. The optocouplers were stressed over a range of temperatures up to 250°C. Due to the new packaging implementation, the isolators exhibit higher output at elevated temperatures. DC characterization, transient characterization, isolation voltage, and the common mode transient immunity characteristics of the isolators were performed at 25°C and up to 250°C. The optocouplers were integrated into a gate driver circuit that utilizes LTCC as a substrate to understand the integration capabilities. The double pulse test results of the gate driver show reliable and consistent switching capabilities from 25°C to 250°C. As a result, an LTCC-based gate driver circuit is achieved to be integrated into a high-density power module.

In the field of electric mobility, in particular heavy-duty electric vehicles and long-haul trucks, the energy systems are susceptible to transients with different amplitudes and dynamics due to the high power demand. With the combination of high power and long distances, the available battery technologies become insufficient as a single energy source for such a system. Thus, the integration of hybrid energy storage systems (HESSs) with different energy capabilities, such as fuel cells, battery packs, and supercapacitors, is highly required. In this context, for leveraging HESSs in an efficient way, a resonant multiwinding transformer-based converter is proposed to interconnect these different energy storage systems (ESSs) since the resonant converters are able to operate at a wider range of switching frequencies and, hence, a wider soft-switching range. However, due to the multiple resonant circuits and possible parameter deviations, the control capability might be compromised. Thus, a multiport resonant dc/dc converter embedded with variable inductors is proposed to enhance the power flow management among these different ESSs with reduced conversion stages. Further, the proposed concept can also improve the immunity to parameter deviations on the resonant by compensating for possible variations at the resonant frequencies. Finally, simulations and experimental results of a $\text{20} \;\text{kW}$ four-port resonant dc/dc converter embedded with variable inductors are shown to prove the effectiveness of the proposed concept.

In this article, the static and dynamic characterizations for semiconductors with different materials, including silicon (Si), silicon carbide (SiC), and gallium nitride (GaN), are evaluated and compared at room temperature and cryogenic temperature (liquid nitrogen temperature). For static characterizations, the on-state resistance and threshold voltage are evaluated. For dynamic characterizations, the turn-on switching loss, turn-off switching loss, and dynamic on-state resistance (Rds(on)) are evaluated. The results demonstrate that Si and GaN based semiconductors have improved performances with lower on-state resistance and faster switching speed at low temperature operations. For SiC based semiconductors, the on-state resistance increases significantly at cryogenic temperature. The switching speed is reduced dramatically for the evaluated 1.2 kV SiC metal oxide semiconductor field effect transistors (MOSFETs) at cryogenic temperature. This makes it less attractive for cryogenic applications. For the evaluated 650 V and 900 V SiC MOSFETs, the switching speed remains almost unchanged at low temperature. GaN high electron mobility transistor (HEMT) demonstrates a fast turn-on switching speed at low temperature, where the device's dv/dt and di/dt are almost doubled when compared with room temperature. In addition, the dynamic Rds(on) of the evaluated GaN HEMTs also decreases at low temperatures. The evaluation results can serve as guidelines for cryogenic power electronics applications. Meanwhile, the future work for semiconductors cryogenic characterizations is discussed.