Tomokazu Domon

Demonstration of 13.56-MHz class-E amplifier using a high-Voltage GaN power-HEMT

A 13.56-MHz class-E amplifier with a high-voltage GaN HEMT as the main switching device is demonstrated to show the possibility of using GaN HEMTs in high-frequency switching power applications such as RF power-supply applications. The 380-V/1.9-A GaN power HEMT was designed and fabricated for high-voltage power-electronics applications. The demonstrated circuit achieved the output power of 13.4 W and the power efficiency of 91% under a drain-peak voltage as high as 330 V. This result shows that high-voltage GaN devices are suitable for high-frequency switching applications under high dc input voltages of over 100 V.

Gallium Nitride power HEMT for high switching frequency power electronics

Very large number of power semiconductor devices (semiconductor power switches) are used in power electronics systems such as AC-DC converter for PCs, DC-DC converters for CPU, motor driver systems and induction heating systems for home appliances, and GaN device is one of a promising candidate for future power devices thanks to the wide band gap semiconductor material property. In GaN base device research, the GaN-HEMT structure is widely investigated than the other device structures specially in RF technology field. This structure also suits to high switching frequency power electronics applications because of the high breakdown voltage and the inherent high speed characteristics of HEMT device. This paper describes the possibility of GaN-HEMT for power electronics applications specially focused on high switching frequency applications comparing the limit of silicon devices such as MOSFETs and IGBTs, and also describes latest research result including demonstration of high switching frequency power electronics circuit.

High Power Density Converter using SiC-SBD

This paper reports on the possibility of a high output power density converter by demonstrating a small volume DC-DC down converter using a 600 V superjunction MOSFET (SJ-MOSFET) and silicon carbide Schottky barrier diode (SiC-SBD). The output power density of the demonstrated DC-DC down converter was 50 W/cc, which is the future target of high power density converters.

380v/1.9A GaN power-HEMT: current collapse phenomena under high applied voltage and demonstration of 27.1 MHz class-E amplifier

The current collapse phenomena in 380V/1.9A GaN power-HEMTs designed for high-voltage power electronics application is reported. The influence of these phenomena to the power-electronics circuit performance under high applied voltage is discussed using a 27.1 MHz class-E amplifier, which can be one of an industrial application candidate. It has been found that the optimized field plate structure minimizes the increase of conduction loss caused by the current collapse phenomena and thus improves the power efficiency of the circuit. The minimized device achieved the output power of 13.8 W and the power efficiency of 89.6 % for the demonstrated circuit even with the applied drain voltage of 330 V and the switching frequency of 27.1 MHz. These results show the nature possibility of a new GaN-device application with both high voltage and high frequency condition

Demonstration of resonant inverter circuit for electrodeless fluorescent lamps using high voltage GaN-HEMT

This paper reports the demonstration of the resonant inverter circuit for electrodeless fluorescent lamps using a high-voltage GaN-HEMT as a main switching device. A 620-V/1.4-A GaN-HEMT was designed and fabricated for power electronic applications. The dynamic on-resistance increased with current collapse phenomena was suppressed by the dual-FP structure and the switching operation could be realized under high applied voltage of over 350 V. As a high-voltage and high-frequency power supply application, a 13.56-MHz resonant inverter circuit for electrodeless fluorescent lamps was demonstrated using the fabricated device. The demonstrated circuit achieved high-voltage operation of 380 V, high-speed gate-switching of 4.5-7 ns, and lighting of the electrodeless lamp with an input power of 7-10 W. High-voltage operation realized a simple circuit composition for high-power efficiency and the discharge ignition of the lamp without the starting circuit. The power efficiency of the inverter circuit was over 90% with an input power of 9 W. These results show that high-voltage GaN devices are suitable for high-frequency switching applications under high-input voltages of several hundred volts.

Non-destructive current measurement for surface mounted power MOSFET on VRM board using magnetic field probing technique

This paper proposes nondestructive current measurement for surface mounted power MOSFET on VRM board using the micro-magnetic probing technique to facilitation discussion of the self-turn-on phenomenon. A notable feature of the proposed technique is that the sensor part is much smaller than that of conventional methods because this method measures the intensity of a partial magnetic field caused by wire bonding inductance, whereas the conventional method employs a loop coil structure around the current flow. The small sense part enables measurement of the VRM board itself just by setting the magnetic probe on the MOSFET package. A calibration technique is introduced to reproduce current waveform and we confirm that the obtained current waveform agrees with that obtained by the conventional Current Transformer. Using the proposed technique, we successfully detect shoot through current waveform for high-side power MOSFET during self-turn-on phenomenon in VRM board. We also sense non-uniform current flow among 3 parallel low-side power MOSFETs caused by board layout location. This study demonstrates the capability of sensing VRM board transient current and indicates the importance of board GND layout distribution behavior in determining highly accurate trade-off between switching loss and self-turn-on loss.

High Voltage and High Switching Frequency Power-Supplies using a GaN-HEMT

This paper reports 13.56 MHz and 27.1 MHz class-E amplifiers with a high voltage GaN-HEMT as the main switching device showing the possibility of GaN-HEMTs in high frequency switching power applications such as RF power-supply applications. The 380 V/1.9 A GaN power-HEMT was designed and fabricated for high-voltage power electronics applications. The demonstrated 13.56 MHz circuit achieved the output power of 13.4 W and the power efficiency of 91 % under a drain-peak voltage as high as 330 V. For a 27.1 MHz circuit, the output power was 13.8 W with the efficiency of 89.6 %. These results show that high voltage GaN-devices are suitable for high frequency switching applications under high DC input voltages of over 100 V

Electrical and mechanical package design for 4.5kV ultra high power IEGT with 6kA turn-off capability

An ultra high power MOS gate device IEGT has developed. A new pressure contact package has been designed considering the gate wiring to avoid current imbalance among chips. The Cu post is also designed to attain homogenous pressure profile in the chip surface. The new package contains 42 IEGT and demonstrates high current turn-off over 6kA under 2.7kV DC bus voltage.

A Built-in Type Amorphous Torque Sensor for an Induction Motor

To keep pace with advances in factory automation, systems for generating torque, such as for numerically controlled machinery and industrial robots, must be able to detect torques and produce corresponding detection signals for use in controlling the torque-generating system. Remarkable progress has recently been made using ac servo systems, which do not require maintenance. Controllability comparable to that of dc motors is needed even in induction motors. This report describes a built-in amorphous torque sensor for use in induction motors, employing rectangular amorphous ribbons with a field-induced magnetic anisotropy and contact-free magnetic heads.

Development of An Amorphous Torque Sensor for Induction Motors

A torque sensor employing amorphous ribbons (FeCoSiB) bonded to the rotor shaft for use in induction motors, is described. Magnetic field annealing is used to induce an anisotropy in the ribbons which were relatively Co-rich composition. By using more than one sensor head, the influence of magnetic fields generated by the motor can be suppressed. Output averaging yielded good linearity, high accuracy (±0.07 kg-m) and satisfactory sensitivity (22.4 mV/kg-m).