Kinya Nakatsu

A novel direct water and double-sided cooled power module and a compact inverter for electrified vehicles

Direct Water and Double-Sided Cooled Power Modules (DWDSCPM) are especially attractive due to high thermal performances. The DWDSCPM was able to reduce the thermal resistance by 50% and increase power density of the traction inverter by 70% in comparison with a conventional power module.

The next-generation high power density inverter technology for vehicle

Realizing a sustainable society will require a reduction in CO2 emissions, and many different sectors of the economy are being encouraged to be energy efficient, including the electric power business, industry, and consumer and transportation businesses. In the transportation sector in particular, environmentally conscious vehicles that use power electronics will be essential as replacements for conventional vehicles powered by internal combustion engines. The main components used in power electronics include inverters, batteries, and electric motors, and we are working on the development of specific technologies intended to make these components even smaller and more efficient than before. In this article, we describe the physical circuit designs needed to make the inverters used for controlling large electric power systems more efficient and techniques that achieve a high level of reliability, including cooling and vibration resistance.

Compact gate drive printed circuit board for uninterruptible power system

A gate drive printed circuit board (PCB) was developed for a 50-mm-wide modular-design thin power unit that uses two double-sided cooled power modules in an uninterruptible power system (UPS). A conventional gate drive PCB has a concentrated gate power supply circuit that uses a large transformer and has a conventional pulse open-phase detection circuit that occupies a large mounting area. Thus, the gate drive PCB had to be downsized to make it as narrow as the thin power unit. Consequently, two circuit configurations were proposed to reduce mounting area: one was to decentralizes a gate power supply circuit using a pre-driver with a built-in DC/DC controller and a small distributed transformer, and the other was to downsize the pulse open-phase detection circuit. As a result, the gate drive PCB was downsized to 50 mm × 220 mm, 56 % smaller than the conventional one. Thus, a very thin power unit using a 50-mm-wide PCB was accomplished, and a UPS was developed that is 30 % smaller in volume than the conventional one.

Insulated metal substrate for power modules using anodic oxide film of aluminum

To improve the insulation reliability of insulated metal substrates for power modules, we propose an insulated metal substrate that has a porous alumina anodic oxide film along the interface between an aluminum base and resin insulating layer. By having two anodic oxide films, i.e., inorganic and organic acids, compared with conventional substrates, the proposed substrate improves the adhesiveness with the resin insulating layer, resulting in 160% improvement in insulation resistance after 2400 h under atmospheric condition in which the temperature was 85°C and relative humidity was 85%, and 30% improvement in breakdown voltage compared with conventional substrates.