2019
The electrothermal co-simulation proposed in this paper accurately reproduces the power loss and the temperature of the silicon carbide (SiC) metal-oxide-semiconductor field-effect transistor (MOSFET) dies assembled in a power module comprising a buck converter. The current-voltage characteristic of the body diode embedded in a SiC MOSFET is not like that of an ideal diode because this characteristic depends on the negative gate-source voltage of the transistor. Our device model was, therefore, created to reflect this unique feature and the temperature dependency of the drain current for predicting the power loss of the MOSFET. The simulation uses a look-up table to reduce the computation time. This yields accurate results for the power loss in a buck converter operating at switching frequencies (fsw) ranging from 50 to 350 kHz. The fsw-dependent steady-state temperature of the SiC MOSFET was reproduced well; it ranged from 60 °C to 140 °C. The maximum deviation between the measured and the simulated results was less than 3.0 W and 8 °C, respectively, for the power loss and the temperature of the dies.
This paper investigates the porosity-dependent tensile mechanical properties of porous 8-10 μm thick silver films. The silver films are fabricated by pressure press, the variety of which changes the porosity (p) ranging 5% to 25%. p is determined by use of scanning electron microscopy cross-section images of the films. Stress-strain (S-S) curves are obtained by tensile tests performed for the porous and bulk silver films. Conventional ductile plateau disappears from the porous films. Augmented ultimate tensile strength and smaller breaking strain happens at a point in p = 6 ~14%.
Presents a terahertz fibre transmission link using RTDs integrated with PC waveguides as a transmitter and a receiver. The coupling efficiency between fibre and PC waveguide is ~30% with a 50 GHz BW. Also, 10-Gbit/s transmission (4K HD) is demonstrated over 1-m fibre.
This paper presents a nonvolatile system-on-chip (NVSoC) with improved integration level, power management flexibility, and system wake-up speed. An on-chip power management subsystem is designed to minimize the number of external components while supporting versatile power policies. And a direct peripheral restore architecture is outlined, which enables a fast and parallel re-configuration of peripheral devices after the resumption of power supply. A test chip is fabricated in a 130-nm ferroelectric-CMOS process with 22.09-mm 2 area. Measurement results show 6× higher data throughput as compared with a conventional NVP when facing power failures.
2018
Through detailed theoretical analysis, a new drive circuit and output voltage control circuit have been devised, achieving a high switching frequency of 25 MHz rarely seen in power circuits. This demonstrates the effectiveness for the new system of mobile base station power supply called Envelope Tracking, which is one of applications.
Modeled external feedback effect of RTD oscillators in THz proximity wireless transmission. This model used RTD circuit model and passive structures of lens and antenna. The simulations using the model clarified origins of the bit error rate change with channel length.
A trans-linked 5kW interleaved inverter using SiC MOSFETs drastically reduced both tansistor loss and reactor loss, resulting in high efficiency over 99% and fanless operation.
2017
To achieve reverse blocking capability, a series Schotty barrier struture was introduces onto the backside of the 4H-SiC MOSFET. The MOSFET exhibits rverce blocking voltage over 3kV and onresistance of 20mΩ･cm2.
Reported a terahertz (THz) sensing system which used RTDs as compact frequency tunable signal source and detector, then high-Q photonic crystal (PC) cavity resonator as a sensitive reactor for THz.
The DC current–voltage characteristics of a semi-insulating GaN layer on a Si wafer have a threshold voltage (VTH). Band diagram simulation reveals that NT–ND determines VTH, and hence, the NT–ND in semi-insulating GaN films can be experimentally estimated by measuring VTH.
2016
An error-free wireless transmission of a 9-Gbit/s on-off-keying modulated signal (4K video) has demonstrated using resonant tunneling diodes transmitter and receiver.
Presented circuit models of terahertz RTD and passives likes transmission line. With their accuracy of the model, new devices of high power oscillators and a high sensitivity detector are designed with antenna matching circuits.
2015
(Invited) Describes continuous mmW and THz applications, with telecom-based photonics technologies. 300-GHz-band wireless link of 50 Gbit/s, precision THz CW- spectroscopy systems, direct E-field radiation measurement, and potentials for THz integrated systems.
Developed silicon photonic-crystal waveguide with low bending loss 0.1-0.2 dB/cm @ 0.3-THz band. Also, demonstrated 1.5-Gbit/s terahertz links through 50cm-long PC waveguide with 28 bends.
This paper report that a three-phase, 5-kW LLC series resonant dc/dc converter utilizing SiC MOSFETs. The high-break down voltage of SiC MOSFETs, enables increasing the input voltage up to 600 V. Around 200kHz switchig frequency successfully reduces the volume of isolation transformers. Current-balancing transformers among each phases effectively suppress a peak current from arising in the circuit and contributed that miniaturizes the input and output capacitances. The conversion efficiency of the converter reaches 97.6% at 5-kW operation.
2019
Demonstrate the dynamic on-state resistance of GaN-HEMT and estimate inpact of loss of devices.
This study report that high speed switching gate drive circuit for SiC MOSFETs. The provided gate drive circuit adapted subsidery capacitor in order to add gate voltage, enables increase gate current. This allows fast charge and discharge and reduced switching losses. This study confirmed that the provided gate drive circuit reduce switching loss compared to conventional one.
A novel measurement method to extract high voltage and high current I-V characteristics (HVHC I-V)of SiC MOSFET is proposed in this paper. The method could extract the HVHC I-V with extremely reduced self heating of the device. By using the method, we can measure higher voltage and current I-V characteristics than those extracted by the conventional method. It is possible for us to measure the HVHC I-V of the next generation SiC MOSFET, whose rated volatge and current is more than those of the conventional device.
The internal gate resistance of SiC MOSFET effects its switching behavior larger than Si devices because it can switch at high speed with low external gate resistance. However, the convention mesurement method of internal gate resistance is not accurate. Then, we devised the new measurement method of it at switching operation by the switching waveforms.
銀焼成は、空孔率がその引張り機械特性に影響することがわかっている。ところが、銀焼成の疲労機械特性について未だ不明である。今回我々は多孔質銀焼成の薄膜試験片と銀膜の疲労試験を実施した。銀焼成膜は、高加圧条件(60MPa)で成膜し、空孔率は5％であった。疲労試験結果から、焼成膜の引張疲労強度は銀膜と比較して低下しやすいことが分かった。
ロームの高度な分析・解析技術により、PZT薄膜のドライエッチング中に起こる形態変化がPZTの結晶方位が変動する現象に起因することを突き止めた。
SiC,GaNのパワーデバイスを開発するだけでなく、それらを使いこなすための技術も伴わないと社会貢献することはできない。本講演では、アプリケーションの実例、それを支える設計技術、ノイズの予測について紹介する
The precise modeling of SiC MOSFETs are difficult by means of conventional modeling method of Si devices because of the device characteristics. Then, we invented the new modeling method for SiC MOSFETs which can reproduce its switching behavior precisely.
A 3-phase15kW using SiC MOSFETs and trans-linked topology achieved maximum efficiency of 99.2%, and verified the benefit of combining SiC MOSFET with trans-linked technology.
IoT社会では、モノやヒトの状態や変化をセンシングして得られるデータを収集し、生産性や環境の改善、安全や安心の向上、セキュリティの強化等のアプリケーションで活用している。本講演では、デバイスにフォーカスし、IoTアプリケーション事例を述べ、将来技術としてのエネルギーハーベスティングについても述べた。
電流形と電圧形を組み合わせたSiC-MOSFET用ハイブリッド形ゲート駆動回路の実機実験により、ターンオン損失が50%、ターンオフ損失が35%低減できることを実証した。
SiC-MOSFETを高速に駆動できるゲート駆動回路についての報告。本ゲート駆動回路は補助キャパシタを用いており、この補助キャパシタを介してゲートに通常よりも高い電圧を印加することができ、ゲート電流を増加させることができる。これにより高速にゲートを充放電し、スイッチング損失を低減できる。実測でもこの効果を確認し、本回路の優位性を実証した。
2018
This paper investigates the porosity-dependent tensile mechanical properties of porous 8-10 μm thick silver films. The silver films are fabricated by pressure press, the variety of which changes the porosity (p) ranging 5% to 25%. p is determined by use of scanning electron microscopy cross-section images of the films. Stress-strain (S-S) curves are obtained by tensile tests performed for the porous and bulk silver films.Breaking strain and Ultimate tensile strengh decrease almost linearly with increase of p.
SiC,GaNのパワーデバイスを開発するだけでなく、それらを使いこなすための技術も伴わないと社会貢献することはできない。本講演では、アプリケーションの実例、それを支える設計技術について紹介する
Workshop: Introduced RTD devices for THz communication and sensing. With comparison with other terahertz device, RTDs are compact and power-efficient.
接合層の機械特性を取得することが、信頼性システムを設計する上で非常に重要な要因となる。次世代接合材として注目される銀焼成は多孔質体でその機械特性が不明であった。今回我々は多孔質銀焼成の薄膜試験片と銀膜を用意した。また銀焼成膜は、加圧力を変化させて作成している。引張試験結果から、銀焼成は銀膜と異なって伸びずに破壊し、高加圧力条件で高強度を示した。
A number of IoT applications are rapidly growing. Among others, smart factory, smart infrastructure and digital medicine/health are major IoT markets. ROHM also succeeded in demonstration of healthcare monitoring utilizing non-volatile PZT devices. The essentials for IoT society and ROHM’s device applications of PZT thin film were described.
A trans-linked 5kW interleaved inverter using SiC MOSFETs drastically reduced both tansistor loss and reactor losses, resulting in high efficiency over 99% and fanless operation.
The accurate electro-thermal simulation is presented by using a new SiC die model to predict the power loss and temperature of SiC MOSFET dies in a power module. The new model incorporates a temperature dependent I-V model and body diode model which is dependent on the gate-voltage. The simulation using the model yields an accurate power loss and temperature estimate of the SiC module in a buck converter.
S-parameter based simulation model for power module (PM) except for the semiconductor chips was created with electromagnetic simulation. This PM model was combined with the chip model in order to build the model of the whole structure. As a result of verifying the model by the double pulse test, the simulation waveforms which reproduce the measurement results well were obtained.
ROHM has developed PZT thin film devices, such as non-volatile ferroelectric memory, highly-sensitive sensors, highly-accurate actuators, high-speed space light modulators and ultra-low-power-consumption non-volatile flip-flop devices so far. ROHM also succeeded in demonstration of healthcare monitoring utilizing non-volatile PZT devices (memory and logic). In this presentation, ROHM’s device applications of PZT thin film were described.
We have proposed a new hybrid structure of the PZT film which we made by sol-gel method of construction on the PbTiO3 seed layer made by rf magnetron sputtering. These hybrid PZT films showed high (100)/(001) orientation and had high breakdown voltage.
電流形と電圧形を組み合わせたSiC-MOSFET用ハイブリッド形ゲート駆動回路を提案し、シミュレーションにてゲート電圧の安定性とスイッチング損失の低減ができることを確認した。
The high speed switching of SiC MOSFET is affected by the parasitic elements of circuit board. Therefore, we analyzed the impact of stray capacitance in circuit board on the switching behavior and tried circuit simulation of the effect by use of precise model and electromagnetic simulation results of circuit board.
2017
Present the recent advance of RTD-based terahertz devices. Based on a well-defined equivalent circuit model, circuits like mixer, detector, and oscillators have been integrated.
IoT社会におけるPZTデバイスの位置付けについて述べ、ロームのPZTデバイス技術（メモリからセンサ/アクチュエータ）を概観した。最近の取組み事例として、「不揮発ロジックデバイス」と「ピエゾMEMSデバイス」を紹介した。
This study report that a three-phase, 5-kW LLC series resonant dc/dc converter utilizing SiC MOSFETs. The high-break down voltage of SiC MOSFETs, enables increasing the input voltage up to 800 V. Around 160kHz switchig frequency successfully reduces the volume of isolation transformers. Current-balancing transformers among each phases effectively suppress a peak current from arising in the circuit and contributed that miniaturizes the input and output capacitances. The proposed power supply weighs 1.55 kg with dimensions including a width of 18 cm, a length of 12 cm, and a height of 12.5cm. The conversion efficiency of the converter reaches 98.1% at 5-kW operation.
2016
本講演では、IoTにおけるセンサの重要性を示し、MEMSセンサ、及びIoT/ワイヤレスセンサネットワークについて述べ、更にはアプリケーション開拓に向けた検証としてのセンサソリューションについても述べた。
Progress In Electromagnetics Research Symposium 2016 China
IoT世界においては、トリリオンセンサに代表されるように大量のセンサがネットワークでつながり、暮らしの省エネから快適性・安全性を高めていく。本講演では、各種センサとセンサネットワークへの取り組み、ヘルスケアに必要な常時モニタリングについて紹介した。
2015
The self-sustained oscillations are sometimes obserbed when SiC MOSFETs switch at high speed in the half bridge configuration. The oscillation is regard as nonlinear self-excited oscillation as a result of its device characteristics. We tried to analyze it from the aspects of device characteristics of MOSFET and trajectory of the oscillation in the I-V plane.
