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To guarantee safe switching of the expensive medium-voltage (MV) device with limited durability, the overcurrent protection scheme based on Rogowski coil current sensor (RCCS) is the promising method, featuring fast response and galvanic isolation. However, it is an inherent contradiction to achieve the RCCS with both high noise immunity and high-bandwidth capabilities. In addition, the nonideal dc and low-frequency characteristics of the integrator cause drift and droop errors. In this article, to address the aforementioned challenges, the broadband RCCS is developed and integrated into the overcurrent protection circuit for the MV SiC mosfet. The novel coil is designed based on the transmission line theory to overcome the constraints imposed by parasitic components on bandwidth. The proposed coil achieves an extra-high bandwidth of approximate 300 MHz with high mutual inductance and shielding layers for high noise immunity. Furthermore, the broadband integrator design method with low-frequency attenuation is proposed to eliminate drift and reduce droop errors significantly. Based on the developed RCCS, the proposed overcurrent protection circuit reacts to both the fault under load and hard switching fault rapidly and softly turns off the device within merely 200 ns. Comprehensive experiments demonstrate its exceptional potential in monitoring current and protecting the expensive MV devices.

Driven by advancements in the semiconductor technology, especially silicon carbide, numerous packaging designs have been developed to meet demands of various applications. Prior to the market release, the reliability of these power modules must be comprehensively assessed. The mechanical characterization is an essential measure to assess the reliability of the power module due to its direct relation to the power module failure. The mechanical distribution and differences, typically on the submicron scale, pose significant measurement challenges. Therefore, achieving accurate sampling of the mechanical information without compromising the functionality and integrity of the power module remains a relentless pursuit in the mechanical characterization. In this article, a comprehensive review of state-of-the-art methodologies for the mechanical characterization of the power module is presented, including both direct and noncontact methods. The deformation mechanisms and associated measurement challenges are analyzed. Various measurement techniques are systematically compared and their advantages and disadvantages are highlighted. In addition, the utilization of the mechanical data in existing applications is discussed, and potential future research directions are discussed. This review may provide insights into the future development and deployment of the power module.

The development of current sensors for wide-bandgap (WBG) applications consistently emphasizes high bandwidth, minimal invasiveness, and integration. Despite the meticulous design that enables current shunts to achieve excellent performance with high bandwidth and low parasitics, their inherent bulkiness remains a significant challenge for their integration into high-integrated applications that depend on the high switching speeds of WBG power devices. This study thoroughly investigates and uncovers the tradeoff faced by traditional current shunts in balancing miniaturization and high bandwidth. Building upon this understanding, the miniaturized current shunt (MiniShunt) concept is introduced to overcome inherent limitations and achieve both high performance and compact size. To realize this concept, a physical implementation that involves the high-density stacking of multiple coupled transmission lines is presented. Additionally, a thermal network model specifically for the proposed MiniShunt configuration is developed and a comprehensive thermal analysis methodology for the current shunts is established. By applying this methodology to finite element analysis, the thermal safe operating area for the MiniShunt can be determined, further providing valuable insights into its maximum static power dissipation and maximum energy loss. These findings contribute to the development of a highly compact 9 × 9-mm, 100-mΩ current shunt with an ultrahigh bandwidth of 3 GHz, near-zero parasitic inductance, and a maximum energy loss of 2.0 J at a reference temperature rise limit of 20 °C. Extensive experiments conducted in both the frequency and time domains serve to further validate the advantages of the MiniShunt in terms of its miniaturization, integration, ultrafast response, and low invasiveness for future high-integrated power electronics applications.

Enhanced insulation and superior thermal characteristics are crucial in advanced packaging for medium voltage (MV) silicon carbide (SiC) power modules. Nonetheless, the reduction in thermal resistance typically compromises insulation level due to the decreased number of insulation layers. In this paper, the forced fluorinated liquid cooling is proposed, whereby fluorinated liquid (3M FC-40) is directed into the power module, substituting silicone gel and diminishing thermal resistance. Through the utilization of forced fluorinated liquid cooling, a reduction of 21°C in junction temperature at full load is demonstrated in the experiment, compared to traditional water cooled power modules. Furthermore, there is a 35.6% reduction observed in the maximum temperature rise ΔTj. As dissipation power is transferred from the topside of the chip to the fluorinated liquid, the possibility of unlimited stacking of direct bonded copper (DBC) is enabled to lower the electrical field, thereby facilitating insulation at the chip bottom side without any worries regarding heightened thermal resistance. Forced fluorinated liquid cooling resulted in a 39°C reduction in the double-stacked DBC power module. Moreover, partial discharge (PD) detection under square wave revealed that the DBC immersed in the fluorinated liquid remains free from PD at 10 kV, a significantly higher threshold than observed with silicone gel. A higher partial discharge inception voltage (PDIV) is anticipated for double-stacked DBC when immersed in 3M FC-40. Thus, the forced fluorinated liquid cooling can be considered a promising solution for the next generation of MV SiC power modules.

Due to the inherent parasitic inductance and high switching speed, the SiC mosfet generally experience significant overvoltage and oscillation, reducing the voltage margin and causing substantial electromagnetic interference. To mitigate these challenges, a novel auxiliary circuit using the gate charge injection (GCI) concept is proposed in this article. The GCI circuit, assembled across the drain-gate of the SiC mosfet, injects charges into the gate during the overvoltage stage of the turn-off process, effectively reducing overvoltage and oscillation without affecting the turn-off speed. The mechanism of the proposed GCI circuit is meticulously analyzed interval by interval based on the cell structure of the SiC mosfet, and its parameters are designed and validated through the circuit simulation. Additionally, the proposed GCI circuit, comprising Si-RC and PiN diode die, is integrated into the SiC power module and assessed by the double pulse test and power cycling test. Experimental results show a 70% reduction in the transient overvoltage at 600 V/30 A and complete the oscillation elimination, with only a 3.4% increase in the switching loss. The GCI circuit does not affect the turn-on process, making it an effective and cost-competitive solution for suppressing the overvoltage and oscillation in the SiC power module.

For a more secure, anti-interference characterization of high-speed wide-bandgap (WBG) power devices, there is a growing need for galvanically isolated measurement methods with higher bandwidth and wider dynamic range. Among these techniques, the differential sensing method has gained attention due to its simplicity, cost-effectiveness, wide dynamic range, and floating measurement capability. Nevertheless, the limited bandwidth of the differential method remains a significant obstacle for characterizing ultrafast switching transients of WBG devices. This article highlights the significant bandwidth limitations encountered in the front-end high-voltage attenuation of the differential method, i.e., the parasitic effects of capacitive networks and the overlooked high-frequency transmission line effects. To address these limitations, the concept of transmission line voltage divider (TL-VD) is introduced, enabling the extension of the operating frequency range of the front-end high-voltage attenuation into the GHz level. To achieve this, four underlying matching principles regarding resistance, capacitance, inductance, and wave impedance are established, which are further simplified to three decoupled, mutually independent, and easily implementable matching objectives of resistance, wave impedance, and transmission line length. These contributions collectively result in the successful development of a ±2.0-kV differential voltage sensing system (DVSS) with an ultrahigh measurement bandwidth of 1.3 GHz and a common-mode rejection ratio of 48 dB at 100 MHz. The experimental comparisons with state-of-the-art commercial galvanically isolated products in both the frequency and time domains confirm the superior performance of the developed TL-VD-based DVSS.

Reducing the thermal resistance is vital for power modules. Thermal conducting paths are formed by heterogeneous layers for insulation, causing inevitably high thermal resistance. In this article, with the aid of direct metallization technology, a direct bonded copper (DBC)-free power module concept is proposed to achieve near-junction water cooling. A 55% reduction of thermal resistance is achieved by using a DBC-free power module instead of a DBC interface. Reliability analysis indicates that the DBC-free power module is sufficiently reliable in terms of mechanical stress, fatigue, and peel strength. The junction temperature of the DBC-free power module is experimentally compared to indirectly and directly water-cooled power modules with the DBC interface. The proposed near-junction water cooling method has effectively achieved reductions of 28 °C and 11 °C in junction temperature, respectively, under full load conditions when compared to the designs of indirectly and directly water-cooled power modules. The maximum junction temperature rise ΔTj of the indirectly water-cooled power module is reduced from 50 °C to 21 °C. The unlimited promise of direct metallization technology in 3-D packaging is also highlighted.