Visualization of dynamic noise current distribution from Si and SiC power devices based on time-synchronized near magnetic field scanning

T. Ibuchi and T. Funaki, "Visualization of dynamic noise current distribution from Si and SiC power devices based on time-synchronized near magnetic field scanning," 2020 International Symposium on Electromagnetic Compatibility - EMC EUROPE, Rome, Italy, 2020, pp. 1-6, doi: 10.1109/EMCEUROPE48519.2020.9245654

Long-term stability of nickel-based ohmic contacts with n-type and p-type 4H-SiC in a high-temperature environment

This is the Accepted Manuscript version of an article accepted for publication in Japanese Journal of Applied Physics. IOP Publishing Ltd are not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.35848/1347-4065/abbb1f

Measuring Terminal Capacitance and Its Voltage Dependency for High-Voltage Power Devices

The switching behavior of semiconductor devices responds to charge/discharge phenomenon of terminal capacitance in the device. The differential capacitance in a semiconductor device varies with the applied voltage in accordance with the depleted region thickness. This study develops a C - V characterization system for high-voltage power transistors (e.g., MOSFET, insulated gate bipolar transistor, and JFET), which realizes the selective measurement of a specified capacitance from among several capacitances integrated in one device. Three capacitances between terminals are evaluated to specify device characteristics-the capacitance for gate-source, gate-drain, and drain-source. The input, output, and reverse transfer capacitance are also evaluated to assess the switching behavior of the power transistor in the circuit. Thus, this paper discusses the five specifications of a C -V characterization system and its measurement results. Moreover, the developed C -V characterization system enables measurement of the transistor capacitances from its blocking condition to the conducting condition with a varying gate bias voltage. The measured C -V characteristics show intricate changes in the low-bias-voltage region, which reflect the device structure. The monotonic capacitance change in the high-voltage region is attributable to the expansion of the depletion region in the drift region. These results help to understand the dynamic behavior of high-power devices during switching operation

A study on EMI noise source modeling with voltage source in synchronous DC-DC buck converter

Y. Saito, T. Ibuchi, T. Funaki, K. Kawai and T. Tsuda, "A study on EMI noise source modeling with voltage source in synchronous DC-DC buck converter," 2020 IEEE 11th International Symposium on Power Electronics for Distributed Generation Systems (PEDG), Dubrovnik, Croatia, 2020, pp. 470-475, doi: 10.1109/PEDG48541.2020.9244423

A Study on Equivalent Circuit Modeling of Wiring Inductance in SiC Power Module for Predicting Conducted EMI of Power Converter

C. Kyotani, I. Takaaki, T. Funaki, T. Miyazaki, Y. Okawauchi and K. Nakahara, "A Study on Equivalent Circuit Modeling of Wiring Inductance in SiC Power Module for Predicting Conducted EMI of Power Converter," 2020 IEEE 11th International Symposium on Power Electronics for Distributed Generation Systems (PEDG), Dubrovnik, Croatia, 2020, pp. 435-440, doi: 10.1109/PEDG48541.2020.9244460

A modular approach to large-signal modeling of an interconnected AC/MTDC system

Y. Susuki, N. Kawamoto, Y. Ohashi, A. Ishigame, T. Funaki and S. D’Arco, "A Modular Approach to Large-Signal Modeling of an Interconnected AC/MTDC System," 2020 IEEE PES Innovative Smart Grid Technologies Europe (ISGT-Europe), The Hague, Netherlands, 2020, pp. 945-949, doi: 10.1109/ISGT-Europe47291.2020.9248890

Evaluation of High Frequency Switching Capability of SiC Schottky Barrier Diode, Based on Junction Capacitance Model

An SiC power device possesses features like high breakdown voltage, fast switching capability, and high temperature operation, and is expected to be superior to conventional Si power devices. This paper clarifies the switching capability of an SiC Schottky barrier diode (SBD) in rectification of high frequency ac voltage. The dynamic behavior of the SiC SBD for switching operation is modeled based on semiconductor physics and device structure, and is characterized by its dc current-voltage (I-V) and ac capacitance-voltage (C-V) characteristics. A C-V characterization system, which measures capacitance using a dc bias voltage corresponding to the maximum rated voltage of the SiC SBD, is developed. The C-V characteristics are evaluated through experiments over the rated voltage range. These results explain the punch-through structure and device parameters. The dynamic behavior of the proposed model is validated through experiments on half-wave rectification of ac voltages over a wide frequency range. As a relational expression of voltage, current, and frequency of an applied ac sinusoidal voltage, the performance criterion of the device is established for rectification. The model also quantitatively assesses the switching capability of SiC SBDs. The model and performance criteria are beneficial for circuit design and device evaluation

The Origin of Nonlinear Phenomena in TCR-SVC Associated With Parametric Excitation of Intrinsic Oscillation and External Excitation

This paper focuses on anomalous nonlinear phenomena in a thyristor controlled reactor-static var compensator (TCR-SVC) system, called switching time bifurcation, and clarifies the relationship between the occurrence of nonlinear phenomenon and the intrinsic characteristics of the circuit equation with switching function. The occurrence of nonlinear phenomenon in a TCR-SVC system cannot be predicted when the dynamics of the circuit related to the switching action is neglected. Therefore, this paper considers the dynamics related to the switching operations in the analysis of nonlinear phenomena. The parametric excitation of circuit is discussed in relation to the homogeneous expression of the circuit equation. This paper indicates that the homogeneous equation of the TCR-SVC system results in Hill's equation, and it can be approximated as Mathieu's equation. The occurrence of nonlinear phenomena in the system is evaluated using the characteristics of Mathieu's equation. The anomalous nonlinear phenomena occur when the natural frequency of Mathieu's equation coincides with the frequency of the ac voltage in a TCR-SVC system. The parametric excitation is also confirmed through the characteristics of Hill's equation. This study clarified the interaction between the switching dynamics of the circuit and its external excitation, and clued the occurrence of nonlinear phenomena in the circuit. The proposed procedure can also be applied to the analysis for other switching converter circuits with periodic excitation source

Study on Factors for Accurate Open Circuit Voltage Characterizations in Mn-Type Li-Ion Batteries

Open circuit voltage (OCV) of lithium batteries has been of interest since the battery management system (BMS) requires an accurate knowledge of the voltage characteristics of any Li-ion batteries. This article presents an OCV characteristic for lithium manganese oxide (LMO) batteries under several experimental operating conditions, and discusses factors for accurate OCV determination. A test system is developed for OCV characterization based on the OCV pulse test method. Various factors for the OCV behavior, such as resting period, step-size of the pulse test, testing current amplitude, hysteresis phenomena, and terminal voltage relationship, are investigated and evaluated. To this end, a general OCV model based on state of charge (SOC) tracking is developed and validated with satisfactory results