Fuji Electric regards energy and the environment as key fields in its business strategy. We offer a wide range of products that can contribute to the development of renewable energy and to protection of the global environment through reduced CO2 emissions. Fuji Electric puts a lot of effort into the advanced power semiconductors, which are the core components in power electronics. Power semiconductors from Fuji Electric offer low loss, low noise, compact size, high reliability, and low price. This report introduces current and future trends in power semiconductor technology, focusing on power modules such as IGBT modules for advanced NPC (neutral-point-clamped) inverters and the IGBT modules for hybrid and electric vehicles, discrete power devices with superjunction MOSFETs, and quasi-resonant control ICs.

A series of IGBT (insulated gate bipolar transistor) modules has been developed to enable A-NPC (advanced neutral-point-clamped) inverters. Modules in this series integrate A-NPC circuits for three phases with thermistors in a single package. Loss is minimized by the adoption of 6th-generation IGBT, FWD (free wheeling diode) and RB-IGBT (reverse blocking IGBT) devices. Loss is reduced by 51% compared to conventional two-level inverters and by 33% compared to conventional NPC three-level inverters. Two types of pin configuration are available, and selectable according to customer requirements.

Fuji Electric has developed a new 1,200 V RB-IGBT (reverse blocking insulated gate bipolar transistor) and used it to form bi-directional switches in A-NPC (advanced neutral-point-clamped) 3-level modules. The new chip features a hybrid through-silicon isolation structure combining wafer front-side boron deep diffusion with back-side V-groove etching. The new RB-IGBT delivers significantly lower loss compared to the conventional combination of diode and IGBT. Use of 1,200 V RB-IGBTs as bidirectional switches and 1,700 V IGBTs and FWDs as main switches achieves power conversion efficiency as high as 98.57%. Power loss in A-NPC inverters has been reduced by 31% compared to 2-level inverters, and by 15% compared to conventional NPC 3-level inverters.

This is a compact IGBT(insulated gate bipolar transistor) module with low thermal resistance for direct liquid cooling, developed to contribute to reducing the size of user systems. Thermal liquid simulations were used to optimize the liquid cooling fin shape. Square pin fins were selected because of their overall outstanding performance, including heat dissipation performance, cooling liquid flow velocity, and pressure loss. Under optimized liquid flow conditions, measurements of chip temperatures were within 2% of simulation values, confirming the reliability of the simulations. From these results, this IGBT module for direct liquid cooling delivers a 30% reduction in thermal resistance and allows a 40% reduction in size compared to the conventional configuration.

Due to various limitations that apply to terrestrial sites, there is a trend toward locating wind power generation systems mainly at sea, spurring the development of higher capacity systems. Fuji Electric is studying a multi-level wind power generation system in a joint research project with China’s Tsinghua University. Under this method, the secondary winding of the generator has the multi-windings design and converter modules are connected in series to obtain high-voltage output. Application of 3,300 V IGBT (insulated gate bipolar transistor) modules in a full-scale system showed that it was possible to realize low loss, high heat dissipation, high reliability, and long system life. Application of this module to multi-level wind power generation systems can enable higher capacity output.

To respond to growing demand in the renewable energy sector, including wind and solar power, Fuji Electric has expanded the lineup of modules in its high-power IGBT （insulated gate bipolar transistor） module families. These new high-power modules feature 6th-generation “V-Series” IGBTs. Operation is guaranteed at maximum junction temperatures up to 175 °C, and the modules deliver industry leading low on-voltage and low switching loss. Reliability is higher than conventional products due to the application of the latest packaging technology, including ultrasonic welded terminals and highly reliable lead-free solder.

To meet the diversifying needs for power control, Fuji Electric has developed a family of large-capacity intelligent power modules (IPMs). These products with high-performance, new-generation IGBT chips, new control ICs and lower package inductance are able to reduce total power loss and radiated noise, and increase current capacity. A new solder material and divided direct copper bonding (DCB) are employed to enable a ΔTc power cycle tolerance signifi cantly enhanced. Terminals and screw hole positions are compatible with existing products, allowing existing products to be replaced with the new products without major design changes.

With the emergence of large-scale renewable energy systems, such as wind and solar power generation systems, there is a need for high-voltage, high-current IGBT modules with high reliability and outstanding electrical characteristics. To meet this need, Fuji Electric has developed the 6th generation 1,700 V“ V-Series” IGBT, featuring a micro p-base structure and a field stop structure optimized for high voltage tolerance. Compared to the previous 1,700 V “U-Series” IGBT, the tradeoff between turn-off loss and on-voltage has been improved by 0.2 V. The newly developed field stop structure has succeeded in raising the thermal runaway temperature, making it possible to raise a chip muximum junction temperature T_jmax to 175 °C.

Fuji Electric has developed hybrid modules that combine Si-IGBT (silicon-insulated gate bipolar transistor) and SiC-SBD (silicon carbide-Schottky barrier diode) for high-efficiency inverter applications that contribute to energy savings. The SiC-SBD chip was developed jointly with the National Institute of Advanced Industrial Science and Technology, a public research institute, and the Si-IGBT chips are the latest 6th-generation “V-Series” IGBTs from Fuji Electric. The product lineup are 600 V class rated at 50/75/100 A, and 1,200 V class rated at 35/50 A. Loss in the 1,200 V 50 A class has been reduced by 23% compared to the previous model.

Wide bandgap materials such as silicon carbide (SiC) and gallium nitride (GaN) are attracting attention as materials for next-generation power semiconductor devices. Fuji Electric is currently developing new packaging technologies to take full advantage of SiC devices. Compact and highly reliable power modules with low thermal impedance and high-temperature operating capability can be realized by replacing aluminium wire bonding, solder joints and silicone gel encapsulating structures with copper pin connections, silver sintering joints and epoxy resin molding structures. Improved performances of trial all-SiC modules and SiC diode modules with the new packaging technologies have been evaluated.

Fuji Electric has developed superjunction MOSFETs with an optimized surface design that delivers lower switching loss. In these “Super-JMOS”chips, gate length and channel density were adjusted to optimize the gate-to-drain capacitance and threshold voltage, thus achieving lower turn-off loss. For devices rated at 600 V/20 A/0.19 Ω, an extremely low turn-off loss of 160 μJ at the turn-off dV/dt of 10 kV/μs was realized. Power efficiency is over 94.0%, enabling compliance with the 80 PLUS certification.

Fuji Electric has added a family of p-channel power MOSFETs to its lineup of power MOSFETs for space applications. Depending on the application, designers can now choose between the existing n-channel power MOSFETs and the new chips, allowing them to reduce the system part count and achieve higher system reliability. Like the n-channel power MOSFETs, the new chips use quasi-plane junction technology to lower the resistance of the drift layer, thus lowering the on-resistance. A low-temperature process is used to form gate oxide films in all diffusion layers, achieving high total ionizing dose (TID) tolerance.

The FA5640 Series of 4th-generation quasi-resonant control ICs have been developed for power supply control ICs of LCD TVs, which can deliver low standby power while also preventing audible noise. Audible noise in switched mode power supplies occurs because of irregularities in the bottom-skip function that adjusts switching frequency. To prevent it, these ICs introduce hysteresis in the detection of load levels under light load conditions. A further optimization adjusts burst operation under light load standby conditions so that burst operation is performed at low power where audible noise is not produced. This eliminates the need for external circuits, making these chips easy to use.