Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)

DOI： https://doi.org/10.1109/TED.2022.3202883

DOI： https://doi.org/10.1109/TED.2022.3202883

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

Language：English   Publishing type：Research paper (international conference proceedings)

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

Language：English   Publishing type：Research paper (scientific journal)

DOI： https://doi.org/10.1016/j.microrel.2021.114289

DOI： https://doi.org/10.1016/j.microrel.2021.114289

Language：English   Publishing type：Research paper (international conference proceedings)

DOI： https://doi.org/10.23919/ICCAS52745.2021.9650029

DOI： https://doi.org/10.23919/ICCAS52745.2021.9650029

Language：English   Publishing type：Research paper (scientific journal)

DOI： https://doi.org/10.1109/ACCESS.2021.3101207

DOI： https://doi.org/10.1109/ACCESS.2021.3101207

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.23919/ISPSD50666.2021.9452304

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.23919/ISPSD50666.2021.9452197

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.23919/ISPSD50666.2021.9452298

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.35848/1347-4065/abebc0

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.sse.2020.107884

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1109/ACCESS.2021.3101207

Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.1109/IEDM13553.2020.9371909

Language：English   Publishing type：Research paper (scientific journal)

UMOSFET on-resistances have been dramatically improved in recent decades with the miniaturization of cell size by innovations in the fabrication process. However, with miniaturization, failure in the gate oxide, large deviations in the threshold voltage and reductions in avalanche capability have emerged as design problems for mass production. In particular, threshold voltage increase have appeared with the introduction of a trench source contact. The source contact trench and MOS gate trench are fabricated next to each other with a narrow silicon mesa region, and the voltage increase appear when the silicon mesa width becomes narrower than 80 nm. So far, it appears that the P+ layer dopant in the contact sidewall diffuses toward the gate oxide and the channel doping increases, which causes the increase in the threshold voltage Vth. We analyzed the distribution of Vth at the wafer level/shot level and found for the first time that the increase in Vth is caused by the punch-through effect from the channel depletion layer to the contact P+ layer, and thus, sidewall dopant diffusion will not affect the increase in Vth. We established an analytical model for the increase in Vth. Our model showed that for the field plate type UMOSFET with a shorter gate contact length, not only is there a increase in Vth, but also it is difficult to control Vth using the conventional channel implantation method.

DOI： 10.1016/j.microrel.2020.113747

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Language：English   Publishing type：Research paper (scientific journal)

Attention has been paid to the next-generation IGBT toward CMOS compatible wafer processes, which can be driven by a 5-V logic level due to its low threshold gate voltage. This low threshold voltage makes the so-called shoot-through fault severer. Even though the switching speed of the IGBT is intentionally reduced, the shoot-through fault can happen. This paper presents shoot-through protection for an inverter consisting of the next-generation IGBTs with gate impedance reduction. Theoretical analysis reveals the criterion of the gate impedance with taking parasitic parameters of the inverter into account.

DOI： 10.1016/j.microrel.2020.113765

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Language：English   Publishing type：Research paper (international conference proceedings)

Power devices are semiconductor devices that handle high voltages and large currents, which are used in electric vehicles, televisions, and trains. Therefore, high reliability and safety are required, and to ensure this, power cycle tests are performed to analyze the breakdown process. Conventional tests are often difficult to analyze due to the influence of sparks generated during the test. Therefore, new tests are being developed by adding ultrasound to conventional methods. The new technology is capable of continuously recording structural changes inside the device during testing, which is expected to make testing much easier than conventional testing. However, the new technology still has some challenges. The main problems are the lack of a method for analyzing large amounts of image data and the extraction of small changes in image features that are difficult to distinguish with the human eye, and the establishment of such a system is required. In this paper, we use deep learning for image classification of the obtained ultrasound images. We propose a new network model with the addition of Batch normalization and Global average pooling to VGG16, which is a pre-trained model. In the experiment, accuracy=98.29%, TPR=98.96% and FPR=7.43% classification accuracy was obtained.

DOI： 10.23919/ICCAS50221.2020.9268275

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

日本   富山（新型コロナ感染拡大に伴い、現地開催中止）   2020.09.27  -  2020.09.30

Language：Japanese   Publishing type：Research paper (scientific journal)

DOI： 10.14923/transcomj.2020JBP3011

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

Language：English   Publishing type：Research paper (international conference proceedings)

Increasing the rated voltage of IGBTs is indispensable for realizing future energy transmission systems such as gigawatt-class UHVDC and high-power motor drives with reduced number of series connection or simplified circuit topology. The voltage of IGBTs, however, has stagnated for 20 years at 6.5kV because of several issues. In this paper, we investigated the feasibility of a 13kV ultra-high voltage IGBT with twice the breakdown voltage of conventional IGBTs using TCAD simulations. As a result, the use of a double gate structure proved to be practical under DC bus voltage of 6.6 kV and a switching frequency of 150 Hz.

DOI： 10.1109/ISPSD46842.2020.9170034

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Language：English   Publishing type：Research paper (international conference proceedings)

According to gaining importance of power electronics systems in the society, reliability issues of power semiconductor devices are the constrains on availability of the system operations. Regular interval based maintenance for higher availability, on the other hand, increases operation cost since the lifetime of power devices have a large deviation with production lots or conditions which they are used. Condition based maintenance (CBM) of power semiconductor devices will be a promising solution for both the availability and cost of power electronics system maintenance. In this study, a high signal resolution condition monitoring system board has been demonstrated. The system monitors real time V-I curve for both switching device and diode with case temperature and the data is stored on board memory and can be monitored on-line. The board was mounted on the gate driver board being supplied power from the gate driver board and demonstrated on a commercial 60kVA inverter.

DOI： 10.1109/ISPSD46842.2020.9170059

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.12792/jiiae.8.50

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.sse.2020.107770

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.35848/1347-4065/ab7414

Language：English   Publishing type：Research paper (international conference proceedings)

An active gate driving is effective to solve the trade-off between the switching loss and the current/voltage overshoot of power transistors. The test cost in the conventional digital gate drivers with four variables, however, is high, because more than 2000 measurements are required to find an optimum gate driving vector out of 64 (~1.7 x 10 ) combinations [1]. To minimize the test cost, a stop-and-go gate drive with only one variable is proposed. The switching loss and the current/voltage overshoot in turn-on/off state of IGBT of the conventional gate drive [1] and the proposed stop-and-go gate drive are measured by using a 6-bit programmable digital gate driver IC across nine conditions including different load currents (20 A, 50 A, and 80 A) and temperatures (25 °C, 75 °C, and 125 °C), and they are compared. The performance degradation of the switching loss and the current/voltage overshoot in the proposed stop-and-go gate drive over the conventional gate drive with four variables [1] is less than 8 % and 25 % across the nine conditions in turn-on/off state respectively. 4 7

DOI： 10.1109/APEC39645.2020.9124356

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Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1109/TSM.2020.2972369

Language：English   Publishing type：Research paper (international conference proceedings)

Measuring the current of a power conversion system is imperative. So, we have developed a new method of measuring a three-phase inverter’s currents of all loads with a single current sensor. We successfully tested this method on a computer simulation and an experimental setup. Which showed that the method can be integrated into power inverters. We proposed an inexpensive analog circuit suitable for capturing current information from a tiny PCB Rogowski coil. It measures the current of the power inverter’s DC supply line and resynthesizes all load currents separately. This way it will reduce the size and cost of a power conversion system’s current measuring devices.

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Language：English   Publishing type：Research paper (international conference proceedings)

Current filamentation during the avalanche period of insulated-gate bipolar transistors (IGBTs) has been investigated using various approaches including TCAD simulations and temperature distribution measurements, since the phenomena can be an origin of chip current capability lowering with the parasitic thyristor latching-up due to the strongly localized current. This paper reports, for the first time, the current filamentation is directly measured as collector currents of segmented metallization areas of an IGBT chip. The experimental results show that the filament moves across the segmented areas with couple of micro second as the transition time and the transitions are not identical for the repeated tests even the circuit condition is the same.

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Language：English   Publishing type：Research paper (international conference proceedings)

Dynamic current balancing is a crucial factor for parallel connected devices. It has to be considered as a prominent issue concerning the high reliability and lifetime of the power module as well as the power electronic converter system. This paper presents, dynamic current balancing among the parallel-connected discrete IGBT devices using a tiny PCB sensor that can be integrated inside a power module for system miniaturization. The output of the tiny PCB sensor is used for current peak detection to perform gate delay compensation through feedback control. Moreover, the currents are also measured using Pearson current probe for authentication of measurement and system performance using PCB sensors.

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Language：English   Publishing type：Research paper (international conference proceedings)

High voltage power generation and conversion are essential considering reduced system losses, consequently, lead to better power system efficiency. Series-connected power devices are used to address and satisfy the high voltage requirement of the system. However, unbalanced voltage stress distribution among the series-connected power devices is a vital concern considering the ageing of the devices, safe-operating-area (SOA) and system reliability. This paper presents, a digital gate drive control (DGDC) method for voltage balancing of series-connected IGBT devices. The proposed method dynamically controls the gate voltage to optimize the overshoot voltage as well as the voltage-stress distribution. The DGDC method is implemented for a three series-connected IGBT system to authenticate the performance.

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Language：English   Publishing type：Research paper (international conference proceedings)

Language：English   Publishing type：Research paper (international conference proceedings)

To optimize operation plans for storage batteries with solar power systems, it is necessary to predict solar radiation for up to one week with high accuracy. However, it is known that the further a prediction system forecasts into the future, the lower the prediction accuracy. In this paper, we report on the results of testing a method for correcting the solar radiation prediction value statistically from a numerical weather prediction model by using the tendency of past error occurrence for predicting seven days ahead.

DOI： 10.1109/ICRERA47325.2019.8997070

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Language：English   Publishing type：Research paper (international conference proceedings)

In this paper, we propose an optimized storage battery operation strategy by considering the long-term variability of the net load with photovoltaics. We derive the power energy cost reduction effects from the proposed strategy that was applied by numerical analysis. From the numerical analysis results, we report that the strategy is more advantageous than conventional strategies.

DOI： 10.1109/ICRERA47325.2019.8996953

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Language：English   Publishing type：Research paper (international conference proceedings)

In this paper, we propose an optimized storage battery operation strategy by considering the long-term variability of net loads with photovoltaics. We derive the power energy cost reduction effects in the case of applying the proposed strategy under storage parity conditions by numerical analysis. From the results, we report that the proposed strategy is more advantageous than conventional methods.

DOI： 10.1109/IFEEC47410.2019.9014973

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Language：English   Publishing type：Research paper (international conference proceedings)

In this work, the switching of 3300V IGBTs by 5V gate drive voltage has been successfully demonstrated for the first time. IGBT was designed based on a scaling principle. Comparing with conventional 15V-driven non-scaled IGBTs, the tum-off tail current of the scaled devices significantly decreased. The improvement of E-{\mathrm{off}} vs V-{\mathrm{cesat}} relationship by 35% was achieved.

DOI： 10.1109/ASICON47005.2019.8983633

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.microrel.2019.113426

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.microrel.2019.113414

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.microrel.2019.113408

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.microrel.2019.113399

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.microrel.2019.07.001

Language：English   Publishing type：Research paper (international conference proceedings)

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

Language：English   Publishing type：Research paper (international conference proceedings)

A load current and temperature dependent optimization of the active gate driving waveforms is proposed to always solve the trade-off between the switching loss and the current/voltage overshoot of power transistors under load current and temperature variations. The switching loss and the current/voltage overshoot in turn-on/off state of IGBT using optimized gate driving vectors obtained by an automatic optimization are measured by using a 6-bit programmable digital gate driver IC across nine conditions including different load currents (20 A, 50 A, and 80 A) and temperatures (25 °C, 75 °C, and 125 °C). They are compared with those with conventional single-step gate driving waveforms using an object function as a function of the normalized loss and overshoot. When the optimized gate driving vector at a typical operation point of (50 A, 25 °C) is reused in other eight conditions, the object functions at eight conditions are better or worse than those of the conventional single-step driving. In contrast, when the gate driving vector is optimized at each condition, the object functions at all eight conditions are better than those of the conventional single-step driving in both turn-on and turn-off states, which clarifies the necessity of the proposed optimization. To implement the proposed optimization, a lookup table based active gate controller, which provides a preset optimum driving vector depending on the load current and the temperature, will be effective.

DOI： 10.1109/ECCE.2019.8913103

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Language：English   Publishing type：Research paper (international conference proceedings)

Inverters used in motor-drive and grid-connected applications usually employ current sensors at the output terminal because they have to control the output current. Existing current sensors like the Hall sensor and the current transformer are a constraint to reduce the volume and cost of the inverter. This paper proposes an output-current measurement method of a PWM inverter using a tiny PCB sensor that is based on the so-called Rogowski coil and can be integrated into an IGBT module. The method utilizes the switching current of the low-side switch for reproducing the output current, which allows using the PCB sensor because the switching current consists of high-frequency components. The method uses a single PCB sensor per leg and takes the polarity of the output current into account. Experimental results using a half-bridge sinusoidal PWM inverter verify that the proposed method measures the output current including its fundamental frequency component, switching ripple one, and polarity.

DOI： 10.1109/ECCE.2019.8912662

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Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.1109/ISPSD.2019.8757665

Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.1109/ISPSD.2019.8757626

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1541/ieejjia.8.480

Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.1109/ISPSD.2019.8757658

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.1109/ISPSD.2019.8757580

Language：English   Publishing type：Research paper (international conference proceedings)

IGBTs need to be immediately turned off when a short circuit occurs [1]. This paper discusses the optimized gate control in this emergency turn-off process. The optimized gate waveform minimizes the energy loss, hence the heat generation, while keeping the maximum collector-emitter voltage overshoot within a certain allowable value. The optimized waveform is found by theoretical analysis and is verified by measurements for the first time. Analytical expressions are derived for the optimized control, which explains well the experimental results. The optimized gate waveform is realized only by a digital gate driver (DGD)whose output drivability is programmable over 64 strength levels. The DGD decreases the energy loss by 22 % compared with the conventional resistor gate driver [2]-[4].

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Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.1109/ICMTS.2019.8730922

Language：English   Publishing type：Research paper (international conference proceedings)

Language：English   Publishing type：Research paper (international conference proceedings)

Language：English   Publishing type：Research paper (international conference proceedings)

Functional trench-gated 1200V-10A class Si-IGBTs, designed based on a three dimensional (3D) scaling concept, were fabricated, and 5V gate voltage switching operation has been demonstrated for the first time. 33% reduction of turn-off loss and 100mV improvement of on-state voltage were achieved, while keeping 1.2kV forward blocking voltage.

DOI： 10.1109/IEDM.2018.8614491

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Language：English   Publishing type：Research paper (international conference proceedings)

The current density of power semiconductor devices continues to increase and, carrier injection has been enhanced by several methods even though turn-off loss tends to be increased. In order to address this problem, we propose a double sided gate IGBT and optimal gate control method for lower turn-off loss. TCAD simulation numerically shows that the proposed IGBT successfully decreases turn-off loss. Furthermore, the turn-off loss is further decreased with optimal control of the double sided gate without surge voltage increase. In addition, we consider the effects of stray inductance on the performance of double sided gate IGBT.

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Language：English   Publishing type：Research paper (international conference proceedings)

Current crowding of IGBT and power diodes in a chip or among chips is a barrier to the realization of highly-reliable power modules and power electronics systems. Current crowding occurs because of stray inductance imbalance, difference of chip characteristics and temperature imbalance among chips. Although current crowding among IGBT or power diode chips has been analyzed by numerical simulation, no sensor with sufficiently high special resolution and fast measurement time has yet been developed. Therefore, we developed a 16-channel sensor array and demonstrated IGBT current distribution imaging. By using the developed simulation method for the sensor array, the accuracy of the magnetic flux signals was confirmed. In future work, we will apply the simulation method to specify the IGBT current distribution corresponding to the structure of bonding wire and other wiring.

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Language：English   Publishing type：Research paper (international conference proceedings)

We developed a printed circuit board “Rogowski coil” to improve the reliability of power modules and packages. For the design, we used a new tool for sensitivity and adopted a fishbone coil pattern to realize design sensitivity. The developed coil demonstrates flat sensitivity that is as good as that of commercialized current probes/sensors because the proposed coil pattern successfully cancels noise from an outside current with flat signal sensitivity by an inside current.

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Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.1109/ECCE.2018.8557709

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.microrel.2018.06.028

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.microrel.2018.06.030

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.microrel.2018.06.026

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.microrel.2018.06.071

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.microrel.2018.07.023

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

Czech   Prague   2018.08.29  -  2018.08.31

Language：English   Publishing type：Research paper (international conference proceedings)

日本   新潟  

DOI： 10.23919/IPEC.2018.8507885

Language：English   Publishing type：Research paper (international conference proceedings)

Field-plate trench MOSFETs (FP-MOSFETs), with the features of ultralow on-resistance and very low gate-drain charge, are currently the mainstream of high-performance applications and their advancement is continuing as low-voltage silicon power devices. However, owing to their structure, their output capacitance (C ), which leads to main power loss, remains to be a problem, especially in megahertz switching. In this study, we propose a structure-based capacitance model of FP-MOSFETs for calculating power loss easily under various conditions. Appropriate equations were modeled for C curves as three divided components. Output charge (Q ) and stored energy (E ) that were calculated using the model corresponded well to technology computer-aided design (TCAD) simulation, and we validated the accuracy of the model quantitatively. In the power loss analysis of FP-MOSFETs, turn-off loss was sufficiently suppressed, however, mainly Q loss increased depending on switching frequency. This analysis reveals that Q may become a significant issue in next-generation high-efficiency FP-MOSFETs. oss oss oss oss oss oss

DOI： 10.7567/JJAP.57.04FR14

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

Language：English   Publishing type：Research paper (international conference proceedings)

Language：English   Publishing type：Research paper (international conference proceedings)

Language：English   Publishing type：Research paper (international conference proceedings)

Destruction under unclamped inductive switching is typical, catastrophic destruction phenomena. We used our original printed circuit board Rogowski sensor and monitored current filaments in IGBT under unclamped inductive switching conditions at emitter pads of IGBT devices. The current filament varied a little by switching condition. Even with the same switching condition, the current varied a little from sample to sample. Temperature and photoemission monitoring was sufficient to analyse a major current filament under unclamped inductive switching condition from the standpoint of time resolution. The spatial resolution of current monitoring should be improved to monitor minor phenomena of current filaments.

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We propose a structure based capacitance model for output capacitance (Coss) and reverse transfer capacitance (Crss) in 60-V class source-field-plate (SFP) and gate-field-plate (GFP) MOSFETs. C-V curves obtained by the model showed good agreement with TCAD simulation. Output charge (Qoss), stored energy (Eoss) and turn-off waveforms also could be calculated very well. In assumption of 30 V, 70 A and 20 to 200 kHz switching operation, power losses related to the FP-MOSFET’s features were estimated by utilizing the model. Moreover, we compared advantages of both FP-MOSFETs for several use conditions.

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Language：Japanese   Publishing type：Research paper (scientific journal)

Language：English   Publishing type：Research paper (scientific journal)

Language：English   Publishing type：Research paper (international conference proceedings)

Language：English   Publishing type：Research paper (international conference proceedings)

Language：English   Publishing type：Research paper (scientific journal)

Language：English   Publishing type：Research paper (scientific journal)

Language：English   Publishing type：Research paper (international conference proceedings)

Three dimensionally (3D) scaled IGBTs that have a scaling factor of 3 (k=3) with respect to current commercial products (k=1) were fabricated for the first time. The scaling was applied to the lateral and vertical dimensions as well as the gate voltage. A significant decrease in ON resistance, - V reduction from 1.70 to 1.26 V - was experimentally confirmed for the 3D scaled IGBTs. ce(sat)

DOI： 10.1109/ASICON.2017.8252681

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Language：English   Publishing type：Research paper (international conference proceedings)

Language：English   Publishing type：Research paper (international conference proceedings)

Language：English   Publishing type：Research paper (international conference proceedings)

Language：English   Publishing type：Research paper (international conference proceedings)

Language：English   Publishing type：Research paper (scientific journal)

A novel diode with a unique trench shape is predicted by TCAD simulation to have high performance. The novel 600 V vertical PiN diode with hole pockets by the Bosch deep trench process shows a better trade-off curve between reverse recovery loss and forward voltage. The reverse recovery loss is reduced by half. In addition, the active chip size of the novel diode is reduced to two-thirds that of the conventional PiN diode in the same forward voltage. Thanks to the hole pockets with an electric field in the diagonal direction, the remaining hole suppresses the surge voltage with noise for high performance. In this paper, we specially focus on the analysis of phenomenon and the noise suppression mechanism during reverse recovery. The novel diode structure is a strong candidate when developing the fabrication process after silicon trench etching is established.

DOI： 10.1016/j.sse.2016.12.006

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Language：English   Publishing type：Research paper (scientific journal)

Language：English   Publishing type：Research paper (scientific journal)

This paper proposes a new output current measuring method using tiny printed-circuit-board (PCB) current sensors. The method will make it possible to install the PCB current sensors in an insulated-gate bipolar transistor (IGBT) module. The PCB sensor picks up a switching current flowing through an IGBT chip, and then a combination of a digital circuit based on field-programmable gate array and an integrator circuit reproduces the output current of an inverter from the switching current. A proof-of-concept experimental verification is carried out using a buck converter, which verifies that the proposed method detects a dc component of the output current as well as a ripple component although the PCB sensor is based on the so-called Rogowski coil.

DOI： 10.1109/TPEL.2016.2606111

Scopus

Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85027502487&origin=inward

Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)

<p>IGBT (Insulated Gate Bipolar Transistor) scaling improves device performance and reduces the gate drive voltage, resulting in an integration with advanced CMOS VLSI. Based on the concept of IGBT scaling, our target is to establish a new paradigm for power electronics, where automatic optimization is realized for power device control by using the IoT (Internet of Things) and AI (Artificial Intelligence). In this article, the research background, the basic concepts, and a portion of the research achievements are described.</p>

DOI： 10.11470/oubutsu.86.11_956

CiNii Article

Other Link： https://ci.nii.ac.jp/naid/130007715469

Language：English   Publishing type：Research paper (international conference proceedings)

High-power conversion systems are based not only on three-phase inverters but also on singlephase inverters because modular multilevel cascade converters (MMCC) consist of half- or fullbridge single-phase converters. Their DC-link capacitors are a major constraint on the improvement of power density as well as of reliability. Evaluation of dc-link capacitors in terms of power loss, ageing, and failure rate will play an important role in the next-generation power converters. This paper presents an evaluation circuit for dc-link capacitors used in a high-power single-phase PWM inverter. The evaluation circuit produces a practical ripple current waveform and a dc bias voltage into a capacitor under test with a downscaled voltage-rating inverter, which is equivalent to those of the full-scale inverter. Theoretical analysis and experimental results verify the effectiveness of the evaluation circuit.

DOI： 10.1109/SBMicro.2017.7990846

Scopus

Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85040555124&origin=inward

Language：English   Publishing type：Research paper (international conference proceedings)

This paper proposes a new power module concept that integrates output current measurement function to make inverters compact. The current measurement function is realized by tiny printed-circuit-board (PCB) Rogowski coils. The PCB Rogowski coil picks up a switching current flowing through an IGBT chip, and then a combination of a digital circuit based on a field-programmable-gate-array (FPGA) and an integrator circuit reproduces the output current of the inverter from the switching current. A major concern of the new power module is the effect of reverse recovery current of free-wheeling diodes because the reverse recovery current is superimposed on the switching current. This paper proposes a mitigating method of the reverse recovery current.

DOI： 10.23919/ISPSD.2017.7988911

Scopus

Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85028518704&origin=inward

Language：English   Publishing type：Research paper (international conference proceedings)

Single-Event Burnout (SEB) is a catastrophic failure in the high voltage devices that is initiated by the passage of particles during turn-off state. Previous papers reported that SEB failure rate increases sharply when applied voltage exceeds a certain threshold voltage. On the other hand, the high voltage devices for the artificial satellite have been increasing. In space, due to increase flux of particle, it is predicted that SEB failure rate will be higher. In this paper, we proposed the failure rate calculation method for high voltage devices based on SEB cross section and flux of particles. This formula can calculate the failure rate at space level and terrestrial level depending on the applied voltage of the high voltage devices.

DOI： 10.23919/ISPSD.2017.7988937

Scopus

Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85028501090&origin=inward

Language：English   Publishing type：Research paper (international conference proceedings)

We developed a screening equipment for ceramic substrate level power module of IGBT. The equipment realizes a new screening test with current distribution. The equipment acquires magnetic field signals over bonding wires and finally classifies to normal/abnormal module automatically. We established statistics based normal/abnormal classification with image processing. It is expected to be applied for screening in a production line and analysis to prevent the failure of power modules.

DOI： 10.23919/ISPSD.2017.7988970

Scopus

Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85028510316&origin=inward

Language：English   Publishing type：Research paper (scientific journal)

Language：English   Publishing type：Research paper (international conference proceedings)

Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.1109/IEDM.2016.7838390

Language：English   Publishing type：Research paper (scientific journal)

USA   Milwaukee  

Language：English   Publishing type：Research paper (scientific journal)

Language：English   Publishing type：Research paper (scientific journal)

Language：English   Publishing type：Research paper (scientific journal)

Language：English   Publishing type：Research paper (international conference proceedings)

Current filamentaion effect with dynamic avalanche during turn-off transient in IGBT has been discussed for years. In the prior papers, the possibility of device failure has been reported based on TCAD simulation and simulation results have shown that variety of filamentation phenomena exist for conditions assumed in each simulation. It is discussed in this paper, for the first time, that the relationship of filamentation current concentration strength to device design parameters and categorizes filamentation phenomena, introducing current filamentation ratio (CFR). In the paper, guidelines for appropriate mesh pattern selection are also described to ensure the validity of simulation results.

DOI： 10.1109/ISPSD.2016.7520847

Scopus

Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84982182689&origin=inward

Language：English   Publishing type：Research paper (international conference proceedings)

The performance of a novel diode with characteristic trench shape is predicted by TCAD simulation. A novel 600 V vertical PiN diode with hole pockets by the Bosch deep trench process is proposed for a better trade-off curve between reverse recovery loss and forward voltage. The reverse recovery loss is reduced to a half. In addition, the active chip size of the novel diode is reduced to two-thirds that of the conventional PiN diode in the same forward voltage. The novel diode structure is a strong candidate when the simple fabrication process under development is established.

DOI： 10.1109/ISPSD.2016.7520836

Scopus

Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84982170348&origin=inward

Language：English   Publishing type：Research paper (scientific journal)

Czech Republic   Prague  

Language：English   Publishing type：Research paper (scientific journal)

Language：English   Publishing type：Research paper (international conference proceedings)

A general-purpose clocked gate driver (CGD) IC to generate an arbitrary gate waveform is proposed to provide a universal platform for fine-grained gate waveform optimization handling various power transistors. The fabricated IC with 0.18μm BCD process has 63 PMOS and 63 NMOS driver transistors on a chip whose activation patterns are controlled by 6-bit digital signals and 25-MHz clock (= 40-ns time step control). In the 500-V switching measurements, the proposed CGD reduces the IC overshoot by 25% and 41% and the energy loss by 38% and 55% for Si-IGBT and SiC-MOSFET, respectively.

DOI： 10.1109/APEC.2016.7468086

Scopus

Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84973620738&origin=inward

Language：English   Publishing type：Research paper (scientific journal)

Language：English   Publishing type：Research paper (international conference proceedings)

USA   Long Beach, CA   2016.03.20  -  2016.03.24

DOI： 10.1109/APEC.2016.7468295

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)

Garmany   Nurnberg   2016.03.08  -  2016.03.10

Language：English   Publishing type：Research paper (international conference proceedings)

Garmany   Nurnberg   2016.03.08  -  2016.03.10

Language：English   Publishing type：Research paper (international conference proceedings)

Garmany   Nurnberg   2016.03.08  -  2016.03.10

Language：English   Publishing type：Research paper (international conference proceedings)

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)

DOI： 10.1299/jsmemecj.2016.F012002

CiNii Article

Other Link： https://ci.nii.ac.jp/naid/130007063655

Language：English   Publishing type：Research paper (international conference proceedings)

Stray inductance inside power device package will be a constraint on improvement of power density as well as switching frequency in power converters because the converters will suffer from electromagnetic interference (EMI)-related problems. This paper proposes a measurement method of mutual inductance for power device packages using time domain reflectometry. The method is characterized by introducing four-terminal measurement that distinguishes self and mutual inductances among collector, emitter, and gate terminals. A measurement fixture for a discrete IGBT is designed, constructed, and tested to ensure repeatability of the proposed method. Experimental results verifies the viability of the proposed method.

DOI： 10.1109/ECCE.2016.7855285

Scopus

Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85015442646&origin=inward

Language：English   Publishing type：Research paper (international conference proceedings)

Recently, the necessity of environmental regulation, low fuel consumption, and natural energy development is proposed by environmental issues. So the demands of power transistor devices are increased. But measurement technique of the current distribution is not keeping up with further miniaturized and integrated were needed in present condition. Now, therefore, ensuring security attended high functionalization is a subject. IGBT (Insulated Gate Bipolar Transistor) is the device that used for wide range of power devices. So we are developing imaging system used non-contact sensor arrays aimed to IGBT production line. In this paper, we propose a development of a supporting system for visual inspection of IGBT device based on statistical feature and complex multi-resolution analysis. First, this performs signal de-noising after entering well-known good data and measured data. Second, the statistical feature is expressed the difference between good data and measured data are calculated. Last, classifying of good and inferiority is performed based on the result of threshold processing. In the paper, we applied our algorithm to 28 sample data including 20 good data and 8 inferiority data.

DOI： 10.1109/ICCAS.2015.7364603

Scopus

Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84966269121&origin=inward

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.microrel.2015.06.045

Scopus

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.microrel.2015.06.128

Scopus

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.microrel.2015.06.016

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)

CPU load model including on-chip wiring and package interconnection has been required for printed circuit board (PCB) design of digital products according to the improvement in the speed of CPU operation in recent years. Especially, accurate power delivery network (PDN) information inside CPU is indispensable for PCB design according to requirement of low-impedance and the broadband (from DC to GHz) from the inside of CPU to DC-DC converter. While the detailed impedance information inside CPUs is not disclosed to PCB board designers with the complicated back-end and front-end production design for CPU chip and package. This paper aims to establish new methodology to extract CPU load model with combination of measurement and simulation. The method is simple yet powerful for high-end CPU board design.

DOI： 10.1109/ICPE.2015.7168125

Scopus

Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84961904009&origin=inward

Language：English   Publishing type：Research paper (international conference proceedings)

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

Hong Kong   2015.05.10  -  2015.05.14

DOI： 10.1109/ISPSD.2015.7123407

Scopus

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.sse.2014.11.011

Scopus

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.microrel.2014.07.083

Scopus

Language：English   Publishing type：Research paper (scientific journal)

Language：English   Publishing type：Research paper (international conference proceedings)

Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.1109/ISPSD.2014.6855968

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)

Language：English   Publishing type：Research paper (international conference proceedings)

Language：English   Publishing type：Research paper (international conference proceedings)

Language：English   Publishing type：Research paper (international conference proceedings)

High-throughput DBC-assembled IGBT screening equipment for a production line is under development in order to prevent early failure of power modules. The equipment has been planning to have automatic GO/NO GO judgment technology by high-throughput measurement of current signal distribution with non-contact sensor arrays with small coils over the bonding wires of IGBT chips. Basic technology and Prototypes of a sensor, an analog amplifier, digital compensation technology, a test head and power circuit have been almost completed. The authors will fabricate the sensor arrays and develop GO/NO GO judgement technology with the integration of a basic technology.

Scopus

Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85084019987&origin=inward

Language：English   Publishing type：Research paper (international conference proceedings)

Real-time failure monitoring system for IGBT module was demonstrated under 500 A power cycling test. The system successfully captured internal phenomena occurred in interface regions of the device under test. Moreover, we proposed realtime failure analysis method by combining the real-time monitoring and image processing techniques. This failure analysis method enables to distinguish the place where degradation occurs in DUT and also trace internal degradation process to failure. © 2014 IEEE.

DOI： 10.1109/ISPSD.2014.6856045

Scopus

Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84905457043&origin=inward

Language：English   Publishing type：Research paper (international conference proceedings)

We investigated the effect of ion-beam irradiation of the 3C-SiC(111) surface on the growth of graphene by the SiC surface-decomposition method. When a 3C-SiC(111) surface was irradiated by 1 keV Ar ions at a dose of 4.5 × 10 cm in an ultra-high-vacuum chamber and then annealed at 1200 °C for 1 min, the formation of graphene layers was promoted in comparison with that in the absence of ion-beam irradiation. X-ray photoelectron spectroscopy studies showed that Ar ion bombardment of the 3C-SiC(111) caused breakage of surface bonds and helped Si atoms to desorb from the surface. © (2014) Trans Tech Publications, Switzerland. + 15 -2

DOI： 10.4028/www.scientific.net/MSF.778-780.1170

Scopus

Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84896064430&origin=inward

Language：English   Publishing type：Research paper (international conference proceedings)

A technique to monitor internal degradation to failure of power devices in real time was proposed. Required components for this technique are (1) non-destructive inside imaging, (2) power stress control and (3) device cooling. We constructed the system with scanning acoustic tomography (SAT), DC power supply controlled by own made program and water cooling system, respectively. In the case of a TO-3P packaged MOSFET, propagation of internal degradations to failure was successfully recorded as time series data by using this system. At the present time, the system is modified for high power and large size IGBT modules.

Scopus

Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85084020110&origin=inward

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.microrel.2013.07.084

Scopus

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.1109/ISPSD.2013.6694419

Scopus

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.1109/ISPSD.2013.6694441

Scopus

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1109/TED.2012.2228272

Scopus

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.sse.2012.10.020

Scopus

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.microrel.2012.06.090

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)

Belgium   Bruges  

DOI： 10.1109/ISPSD.2012.6229079

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)

Belgium   Bruges  

DOI： 10.1109/ISPSD.2012.6229053

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)

Belgium   Bruges  

DOI： 10.1109/ISPSD.2012.6229052

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)

Belgium   Bruges  

DOI： 10.1109/ISPSD.2012.6229048

Scopus

Language：English   Publishing type：Research paper (scientific journal)

フランス   ボルドー   2011.10.03  -  2011.10.07

DOI： 10.1016/j.microrel.2011.06.015

Scopus

Other Link： https://www.journals.elsevier.com/microelectronics-reliability

Language：English   Publishing type：Research paper (scientific journal)

フランス   ボルドー   2011.10.03  -  2011.10.07

Other Link： http://www.elsevier.com/locate/microrel

Language：English   Publishing type：Research paper (scientific journal)

フランス   ボルドー   2011.10.03  -  2011.10.07

Other Link： http://www.elsevier.com/locate/microrel

Language：English   Publishing type：Research paper (scientific journal)

アメリカ   サンディエゴ   2011.05.23  -  2011.05.26

DOI： 10.1109/ISPSD.2011.5890790

Scopus

Language：English   Publishing type：Research paper (scientific journal)

アメリカ   サンディエゴ   2011.05.23  -  2011.05.26

DOI： 10.1109/ISPSD.2011.5890796

Scopus

Language：English   Publishing type：Research paper (other academic)

広島   2010.04  -  2010.04

Language：English   Publishing type：Research paper (other academic)

広島   2010.04  -  2010.04

Language：English   Publishing type：Research paper (other academic)

広島   2010.04  -  2010.04

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広島   2010.04  -  2010.04

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2008.04  -  2008.04

Language：English   Publishing type：Research paper (other academic)

2008.04  -  2008.04

Language：English   Publishing type：Research paper (other academic)

2008.04  -  2008.04

DOI： 10.1541/ieejeiss.130.961

Scopus

CiNii Article

Language：English   Publishing type：Research paper (other academic)

Language：English   Publishing type：Research paper (other academic)

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2005.04  -  2005.04

Event date： 2021.01.25   Language：Japanese  

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CiNii Article

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