Power Electronics Laboratory

GaN (Gallium Nitride) power devices and SiC (Silicon Carbide) power devices are attracting attention as the following generation devices. Our laboratory successfully reproduce the mechanism of GaN FET switching in a circuit simulator.

Power converter structure and passive elements are designed optimally to take full advantage of GaN power devices. We have built:

• A converter with the world highest level power density

• An Inverter with 99% efficiency in all output range

• A converter operated in 13.56 MHz

and so on.

   Φ2 class inverter operated in 13.56MHz

Input voltage: 75 [V]

Outputpower:200 [W]

Switching frequency: 13.56 [MHz]

Conventional semiconductor devices such as Silicon power devices and vertical SiC power devices hardly achieve the operation in very high frequency like 13.56MHz. This inverter fully utilizes high frequency characteristics of GaN power semiconductor devices and achieves switching operation in 13.56MHz. The gate driver contains its original technologies and it is differentiated from other inverters at the point of availability to the load fluctuation

We also conduct researches on SiC power semiconductor device applications. The full SiC inverter created in our lab achieves higher efficiency than that of existing IGBT inverters. An experimental unit has successfully driven a 2.2kW inductive motor.

In our laboratory, comprehensive research topics are picked up from both microscopic perspective and macroscopic perspective, such as:

• A module technology to drive full SiC invereter stably.

• Energy saving effect of highly efficient conversion on a hybrid vehicle system.

and so on.

  Power Module Design for CM Noise Attenuation

Power rating: 15 [kW]

Voltage－current rating: 400 [V]－50 [A]

Two SiC MOSFET in parallel

A specific area of bottom copper of DBC is etched to reduce CM capacitance without compromising the size of the power module, top copper pattern, thermal performance, and mechanical reliability. The proposed power module design is not limited to power modules with higher power, numerous switching devices or double-sided cooling.

Wireless power transfer technology was first put into use for mobile device chargers. Application of electric vehicle charger is now studied around the world.

In our laboratory, on-board wireless charger technologies for automobiles, vessels and aircrafts are studied. A basic study on a new wireless power transfer method is conducted.

A power electronics circuit needs magnetic components such as transformers or inductors. We propose new magnetic core structure or winding structure and study methods to accomplish higher and higher energy density.

Integration of magnetic cores allows inductors to share magnetic flux and this change results in reduction of the total volume and weight. Aiming at improvement of power characteristics or frequency characteristics, integration of magnetic cores made of different materials are investigated.

In photovoltaic power generation, an output voltage changes frequently depending on the weather. Therefore, a power conditioner circuit is necessary to supply energy in stable voltage. We use the following generation devices and integrated magnetic components to achieve a high efficiency and small power conditioner

To bring out a maximum potential of GaNpower semiconductor device, we built φ2 inverter operated in 27.12 MHz.This hundred times higher operating frequency than that of conventional inverter enables a very thin, paper-like converters. We named this converter structure with excellent heat dissipation “Paper converter” and we are trying to expand its application.

Electrical aircraft is attracting attentions in the environmental point of view. Due to increasing needs of new mobilities and improvement in auto-driving technology, “flying automobile” is getting more and more sense of reality. For these aircrafts, high power motor driver circuit plays a significant roll. We study optimization of converters and inverters and motor control suitable for those applications.