Toward establishing low carbon societies, expectations are rising significantly for diffusion of renewable energ power generation and wind power generation as well as power electronics technology, which uses such energ to meet these expectations, Fuji Electric is developing user-friendly power semiconductor products with high eefficiency and low noise for various sectors such as environment, energy, automobile, industrial machinery, so home appliances.
This special edition introduces the latest technology and products of power semiconductors, which are the key electronics technology.

To be applied to harmonize with the global environment and create secure, safe and sustainable society, power electronics technology, which supports efficient use of energy, is greatly expected. To meet these expectations, Fuji Electric is developing environmentally friendly power semiconductor products with high energy-conversion efficiency and low noise. These products are mass-produced and applied to various sectors such as environment, energy, automobile, industrial machinery, social infrastructure, and home appliances, making contributions to the world. This paper introduces the latest technologies and the current status and future outlook of power semiconductor products, mainly on power modules, power discrete devices, and power ICs, which are the key devices of power electronics technology.

Fuji Electric is working on the development of a 1,200 V withstand voltage SiC hybrid module as a power device for inverters that contribute to energy conservation. This hybrid module uses a SiC-Schottky barrier diode (SiC-SBD) chip, which has been developed jointly with the National Institute of Advanced Industrial Science and Technology and has been mass-produced by Fuji Electric. As the insulatedgate bipolar transistor (IGBT), Fuji Electric’s latest 6th-generation“ V Series”IGBT chip was adopted. For its 300A products, the generated loss has been reduced by approximately 25% compared with conventional Si modules.

An all-SiC module for mega-solar power conditioners has been developed. The structure developed for the all-SiC module has achieved a reduction in wiring inductance of approximately 80% from the existing structure that uses wire bonding. This allows for a signifi cant reduction in loss, leading to an advantage in high-speed switching of SiC devices. In addition, it has shown a higher resistance to thermal load in a power cycling test as compared with the conventional structure. We have developed an all-SiC chopper module for booster circuits by applying these technologies and integrated it in a mega-solar power conditioner, thereby achieving the world’s highest level of effi ciency of 98.8%.

Fuji Electric has developed an reverse conducting IGBT (RC-IGBT) for industrial use and it integrates an IGBT and freewheeling diode(FWD). We have combined it with a new package that achieves both low thermal resistance and high reliability to successfully realize a signifi cant miniaturization of the IGBT module and power density improvement. The RC-IGBT has reduced power loss to a level equivalent to that of the conventional IGBT+FWD and achieved a reduction in thermal resistance of 30%. The new module, combining the RC-IGBT and new package, which has a footprint 42% that of the conventional module, realizes an almost equivalent inverter loss and a signifi cant reduction in the IGBT junction temperature. A comparison based on the same IGBT junction temperature shows that it operates with a 58% larger output current.

Hybrid electric vehicles and electric vehicles are attracting attention as people’s environmental awareness is growing. Above all, mild hybrid electric vehicles, in which one motor is responsible for both driving and power generation, is expected to account for a higher proportion of vehicles. To reduce the loss and size of Insulated-gate bipolar transistor (IGBT) modules for mild hybrid electric vehicles, Fuji Electric has developed a reverse-conducting IGBT (RC-IGBT) that has a withstand voltage of 650 V, which integrates an IGBT and freewheeling diode (FWD) into one chip. The RC-IGBT has realized a lower loss and reduced package size that surpass the conventional IGBTs and FWDs.

As activities for preventing global warming and allowing for eff ective use of resources, further improvements in the fuel effi ciency of eco-friendly vehicles such as hybrid electric vehicles is called for. To that end, size and weight reduction of intelligent power modules (IPMs) for hybrid electric vehicles is required. To meet this need, Fuji Electric has developed three new packaging technologies: technology for designing a radiator with a structure capable of direct liquid cooling using aluminum, ultrasonic bonding technology and thermal resistance improvement technology that allows continuous operation at 175°C. The 2nd-generation direct liquid cooling IPM using aluminum, which applies these technologies, has achieved a volume reduction of 30% and mass reduction of 60% from the 1st-generation model.

Switching power supplies, which are widely used for electronic devices, are required to have a power factor correction (PFC) circuit to reduce harmonic current.
In order to meet the market demand for less power consumption and lower cost of power supplies, Fuji Electric has developed the thirdgeneration critical mode PFC control IC“ FA1A00 Series” intended for PFC circuits. The bottom-skip function has successfully improved the efficiency under low load and the power good signal function has reduced the number of power circuit parts. Safety has also been improved by having an overshoot suppression function and improved reference voltage accuracy.

For relatively large capacity power supplies, such as ones for large screen TVs and server devices, LLC current resonant power supplies are commonly used to meet the requirements for high effi ciency, reduced size and lower noise. An LLC current resonant power supply uses leakage inductance of a transformer for resonance and the voltage gain varies along with the switching frequency, which makes the design of a transformer more diffi cult than other control methods. Fuji Electric is working on the development and mass production of control ICs of LLC current resonant power supplies and provides technical support for customers in the area of power supply development. This paper describes the principle of operation of an LLC current resonant power supply and the design method and characteristics of transformers.

Fuji Electric has developed a high current intelligent power switch (IPS) for controlling high output motors of vehicles. The power MOSFET using a trench structure and the control IC are built into a chip-on-chip structure, thereby realizing low on-state resistance (maximum of 5 mΩ) with a compact package. To achieve high reliability, protective functions such as overcurrent/overheat detection and low voltage detection have been provided. In addition, a package with good heat dissipation properties has been adopted, and a configuration that offers well-balanced energy distribution in parallel connections is provided. This package can thereby cope with temperature rises caused by an increased current due to a low on-state resistance.