SiC Stacked-Capacitor Converters for Pulse Applications

This paper presents a performance comparison of two wide band gap (WBG) devices, a silicon carbide (SiC) MOSFET and an enhancement mode gallium nitride (eGaN) FET in a resonant inverter operating at 6.78 MHz for wireless power transfer (WPT) applications. While SiC MOSFETs provide high breakdown voltage and good thermal characteristics, eGaN FETs can reduce gate losses due to small gate resistance and input capacitance. In this work, we compare a 1200 V SiC MOSFET in a single-ended class Φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> inverter to two 650 V eGaN FETs in a push-pull class Φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> inverter. We designed and implemented a 6.78 MHz 2.2 kW single-ended class Φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> inverter using a 1200 V customized SiC MOSFET with low-inductance package. In our experiments, the inverter has a 93% efficiency and 2.2 kW output power with input voltage of 440 V. We also implemented a push-pull class Φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> inverter using two 650 V eGaN FETs at 6.78 MHz. The push-pull class Φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> inverter reduces the input current ripple because of interleaving operation. At 200 V input voltage, the push-pull inverter with two eGaN FETs provides output power of 2 kW with 96% efficiency. In order to reduce a volume and weight of the inverter, we implemented a class Φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> inverter with 3D printed inductors.

This paper describes a comprehensive analysis of a three-phase two-level silicon carbide (SiC) MOSFET V2G inverter including the LCL filter design. The efficiency is compared between the SiC MOSFET and Si IGBT. Using a SiC device enables the inverter to operate at high switching frequency and this leads to improved efficiency up to 99.05% at 10 kHz and 97.71% at 100 kHz switching frequency. The output LCL filter is also designed based on a specific switching frequency and the filter value is most significantly reduced at the highest switching frequency. The SiC inverter and LCL filter is simulated using LTSpice and MATLAB Simulink.

In this paper, the integrated fast short-circuit protection technique with soft turn-off is proposed for SiC (silicon carbide) MOSFET. Two short-circuit faults, HSF (hard switching fault) and FOF (flashover fault), can be judged by detecting EMI (electromagnetic interference) noises of SiC MOSFET. When there are short-circuit faults for SiC MOSFET, the soft turn-off is initiated to reduce EMI noises and protect SiC MOSFET. The proposed fast short-circuit protection technique is realized on the chip and is verified in a 0.18 μm BCD (Bipolar-CMOS-DMOS) process. Simulation results show that the proposed short-circuit protection has a fast response speed and then SiC MOSFET is turned off slowly when there are HSF and FOF. Therefore, the proposed fast short-circuit protection technique can be well applied for SiC MOSFETs, making SiC MOSFETs safely used in HV (high-voltage) and high current applications.

For the same blocking voltage rating and on-state resistance, Silicon Carbide (SiC) MOSFETs die is thinner and smaller compared to Si counterpart due to SiC material's superior electric-field withstanding capability. This smaller die size improves the switching performance significantly but deteriorates the thermal performance of the device packaging. This makes thermal design more challenging when using SiC MOSFETs. When using surface-mount (SM) packaging, printed circuit board (PCB) design plays a key role in the overall thermal design. Understanding the PCB design choices is necessary to maximize the performance of SM SiC MOSFET. This paper investigates several key factors in the thermal design of FR4 PCB to reduce junction temperature (Tj) of surface-mount (SM) SiC MOSFETs in steady-state and overload transient conditions. The factors of interest include heat sinks, copper area per device, and copper thickness. In experiments, doubling PCB copper area can reduce Δ <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$T_{j}$</tex> by > 40% in steady-state operation, making it the dominant factor. Experiments are performed on a two-layer PCB with a 900 V, 20 mΩ SiC device in D2Pak-7L package. For steady-state performance, doubling PCB copper area reduced the junction temperature rise by > 40%, making it the dominant design factor for steady-state thermal performance. For transient tests, copper thickness is the most critical factor. Junction temperature rise reduced by > 30% when PCB copper thickness is increased from 2 ounces (oz) to 6 oz. Experimental data is provided at various current stress levels for nominal steady-state and overload transient conditions. The findings provide thermal design guidelines of FR4 PCB for SM SiC MOSFETs in various applications.

Silicon Carbide (SiC) MOSFETs offer high speed switching for power applications at high blocking voltage ratings, e.g. 1.2 kV, 3.3kV and more in the future. Connecting SiC MOSFETs in series is of interest to achieve AC distribution voltage levels. This paper presents experimental results of SiC MOSFETs from two different manufacturers switching independently in the series connection. The results indicate that the switching of SiC MOSFETs in the series connection is attractive, with no need for active control systems or passive snubbers to obtain an evenly distributed voltage sharing. The intrinsic characteristics of SiC MOSFETs, the nature of the ringing at turn-off and the voltage sharing at turn-on are discussed.

Silicon Carbide (SiC) MOSFET devices exhibiting several advantages, including high blocking voltage, lower conduction losses, and lower switching losses, when compared to silicon-based devices have become commercially available, enabling their adoption into power supply products. This paper presents a novel approach to designing a cycloconverter using SiC MOSFETs as opposed to the conventional usage of IGBT. A comparative study is attempted between the two with respect to distortion and system efficiency. MATLAB/Simulink models and simulations are used to analyze the results for the above.

Silicon Carbide (SiC) MOSFETs, as wide-bandgap semiconductor device, has capability to switch at much higher frequency in comparison with their silicon (Si) counterparts. Industrial motor drive is usually connected to induction motor with long shielded cable. This long shielded cable introduces parasitics such as stray inductance and capacitance to the system, which affects SiC MOSFETs performance for inverter side and reflected wave transient overvoltage on motor terminals. In this paper, switching performance of SiC MOSFETs is systematically studied under different length of cables with both inductor load and induction motor load. Compared with standard DPT, turn on and turn off current ringing decays slower with longer cable which leads to 20% higher switching loss. Long cable also contributes to longer turn off time at low current. Furthermore, a theoretical reflected wave model with SiC MOSFETs based inverter is presented to estimate motor terminal voltage. A much higher dv/dt caused by SiC MOSFETs fast switching results in more strict requirements for both motor and cable selection. The test shows motor transient voltage achieved twice DC bus voltage with 100ft cable under single pulse condition. If pulse width modulation (PWM) is not adjusted properly, motor voltage may shoot up to 3∼4 times DC bus voltage. The potential solutions for switching performance improvement and reflected wave are also discussed and provided in this paper.

The utilization of wide bandgap devices such as silicon carbide (SiC) devices can significantly reduce the switching losses due to its fast switching speed. However, it cannot be widely used because of its high cost. Thus, SiC+Si hybrid topology is proposed. It only replaces a part of devices with SiC devices, thus the total cost is lower than that of the all-SiC-devices-based topology. Furthermore, the efficiency of the hybrid topology can be improved by applying suitable modulation strategies. Among all of the studies on hybrid applications, few attentions have been paid to reducing the conduction losses. This paper proposes an improved modulation strategy based on SiC+Si hybrid five-level active neutral point clamped inverter (FL-ANPC) topology, which can not only reduce the switching losses, but also reduce the conduction losses. In addition, as only two SiC MOSFETs are used, the cost is greatly reduced compared with the all-SiC-MOSFETs-based topology. Experimental results are presented to confirm the benefits of this proposed modulation strategy of FL-ANPC inverter.

Silicon carbide (SiC) MOSFET features low switching loss and it is advantageous in high switching frequency application, but the manufacture per Ampere cost is approximately five times higher than the silicon (Si) IGBT. Therefore, by paralleling Si IGBT and SiC MOSFET together, a trade-off between cost and loss is achieved. In this paper, a four control freedoms active gate driver (AGD) including turn-on delay, turn-off delay, and two independent gate voltages, is proposed to optimize the performance of the paralleled device. By adjusting these four control freedoms, optimal operation for paralleled device can be obtained. Moreover, the proposed AGD can dynamically adjust the current ratio between two paralleled devices, which can help achieve thermal balance between two devices and improve system reliability. Double pulse test (DPT) experimental results are presented and analyzed to validate the effectiveness of the proposed AGD for paralleled Si IGBT and SiC MOSFET application.

This paper presents a comprehensive evaluation and experimental comparison of silicon carbide power MOSFETs through double pulse test. First, a universal hardware platform is designed and developed to test power semiconductor devices with various device packages and measuring requirements. Using the developed platform, the static characteristics and switching performance of the two types of SiC MOSFETs (one planar and one trench type) are evaluated under different case temperatures from 25 oC to 175 oC. Based on the evaluation data, a comparison of both SiC MOSFETs is conducted in terms of their on-state resistance, switching loss, and temperature dependent behavior. It is found that the latest trench SiC MOSFETs present similar switching loss while much lower conduction loss compared to existing commercial planar SiC MOSFETs. Moreover, the trench devices show a nearly temperature independent switching loss, which is beneficial to suppress the potential thermal runaway issue under high temperature continuous operation.

Increasing concern about the environmental impact of ships has made Shore-to-Ship (STS) power an attractive solution for ship owners and port authorities worldwide in reducing emissions at ports. Existing shore-to-ship solutions for 0.1 MVA to 5 MVA applications employ silicon (Si) IGBT based static frequency converters. Recent developments in high voltage silicon carbide (SiC) devices have facilitated improvement in efficiency and power density of medium voltage (MV) converters in various applications. This paper proposes an MV STS system enabled by series connection of three 3.3 kV SiC MOSFETs, which shows the potential for improved power density and efficiency compared to existing Si IGBT based solutions. A 100 kVA 3-phase two-level voltage source converter (VSC) with series connected 3.3 kV SiC MOSFETs is designed and demonstrated. Experimental results for the series connected 3.3kV SiC MOSFET based converter is shown at 6 kV dc link voltage to validate the design and operation of such a system. Successful demonstration of a MV converter system enabled by series connection of high voltage SiC MOSFETs can open up opportunities to replace conventional Si IGBT based converters with SiC MOSFET based converters in applications interfacing with medium voltage grid.

In this study, a silicon carbide (SiC) MOSFET driving circuit and its protection circuit applied to high temperature (HT) environment are designed by using commercial off‐the‐shelf discrete components. The proposed driving circuit can work at C with a low driving dissipation. An isolation structure with a transformer is utilised to prevent the control circuits from being disturbed by the power circuit. The high value of output driving voltage is 19 V to ensure the low on‐resistance of SiC MOSFET, while the low value of is V to ensure the SiC MOSFET not be turned on mistakenly. The driving circuit also solves the the contradiction between the BJT switch speed and power dissipation of conventional HT SiC MOSFET driving circuit. The rising time and falling time of the output are reduced greatly, which can increase the performance of SiC MOSFET in high frequency application at a HT.

The short-circuit capability of Silicon Carbide (SiC) MOSFETs is much worse than the Si IGBT counterparts. There are two kinds of commercially available SiC MOSFET devices (trench MOSFETs and planar MOSFETs), and their short-circuit capability is not exactly the same. At present, there is a lack of comparative study on the short-circuit capability of these two kinds of devices. To solve this problem, this paper carries out a comparative study of the short-circuit capability of the two devices. Experiment results show that in the case of short circuit tests, it takes more time for planar MOSFETs to reach their peak currents because of their lower channel mobility and higher trap density. The DC voltage has little impact on the peak current which is mainly affected by the gate voltage. At the low DC voltage, such as 400V, 500V and 600V, planar MOSFETs have better short-circuit indexes no matter the short circuit withstand time (SCWT) or the short-circuit energy. However, at 800V DC voltage, trench MOSFETs have a better performance in short-circuit tests. Considering the factor of different areas, the short-circuit energy density of trench MOSFETs is higher than that of planar devices, especially under the condition of 800V high DC voltage.

Transformerless inverters are widely employed in PV grid-tied inverter due to their capability of reducing power losses and enhancing the system efficiency. Several multilevel transformerless topologies are investigated to increase power quality and system efficiency. Wide bandgap power devices such as SiC MOSFETs can increase the system performance and reduce the total losses due to their superior features over Si switching devices. In this paper, a three level transformerless inverter based on H6 topology is proposed. The proposed topology is implemented with a silicon carbide (SiC) MOSFETs and a modulation approach is adopted to reduce the number of conducting switches. Simulation results show that total conduction and switching losses are reduced by about 50% and the efficiency of the system is increased by 3% at a high switching frequency of 100 kHz.

Silicon carbide (SiC) MOSFETs are fundamental to the advance of high-efficiency, high-power-density electronic systems, owing to their superior material properties compared to conventional silicon (Si) devices. However, their widespread adoption is hindered by their relatively weak short-circuit withstand capability, which stems from smaller chip sizes and higher current densities. This paper provides a comprehensive review and analysis of the failure modes, underlying physical mechanisms, and protection strategies pertinent to SiC MOSFETs under short-circuit conditions. The second section of the main body in this paper reveals two primary failure modes: gate interlayer dielectric breakdown (Mode I) and thermal runaway (Mode II), which are driven by thermomechanical stresses and parasitic BJT activation, respectively. Furthermore, threshold voltage instability, caused by oxide trap charging and activation, is identified as a significant factor degrading long-term reliability. In the third section, a critical evaluation of short-circuit protection (SCP) methods is presented, categorizing them based on the monitored parameters (VDS, IDS, or gate characteristics). The analysis reveals that while traditional desaturation detection is common, it is often too slow for SiC devices. Advanced methods using Rogowski coils or two-dimensional monitoring offer the requisite ultra-fast detection times (&lt;100 ns) but increase complexity. The necessity of implementing Soft Turn-Off (STO) strategies to safely mitigate destructive voltage overshoots post-detection is also established. This paper synthesizes these findings to offer a holistic understanding of SiC MOSFET short-circuit reliability and provides a crucial guide for designing robust and effective protection systems.