Publications & Presentations
Electrothermal Co-simulation for Predicting the Power Loss and Temperature of SiC MOSFET Dies Assembled in a Power Module
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%.
Terahertz fibre transmission link using resonant tunnelling diodes integrated with photonic-crystal waveguides
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.
A 130-nm Ferroelectric Nonvolatile System-on-Chip With Direct Peripheral Restore Architecture for Transient Computing System
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.
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 Fanless Operating Trans-Linked Interleaved 5 kW Inverter Using SiC MOSFETs to Achieve 99% Power Conversion Efficiency
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.
High-Temperature Characteristics of 3-kV 4H-SiC Reverse Blocking MOSFET for High-Performance Bidirectional Switch
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.
Extraction of net acceptor type trap density in semi-insulating GaN layers grown on Si substrate by DC I-V measurement
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.
High-speed error-free wireless data transmission using a terahertz resonant tunneling diode transmitter and receiver
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.
(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.
Three Phase LLC Series Resonant DC/DC Converter Using SiC MOSFETs to Realize High Voltage and High Frequency Operation
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.