Using SiC/GaN power semiconductors to improve power conversion efficiency, technological progress in passive components is very important!

Governments around the world and businesses across all industries are working together to advance initiatives towards carbon neutrality. Decarbonization measures are being implemented from every conceivable angle, such as using renewable energy sources such as solar power generation, electrifying equipment that has hitherto burned fossil fuels, and reducing the power consumption of existing equipment such as home appliances, IT equipment, and industrial motors. etc. As more decarbonization initiatives are implemented, there is one area of ​​semiconductors where technological innovation is rapidly accelerating. It is a power semiconductor .

Power semiconductors have various component structures such as MOSFETs, IGBTs, and diodes, and are used separately depending on the application. in,

That is, a metal oxide semiconductor field effect transistor is a field effect transistor that functions as an electrical switch. It is composed of 3 layers: metal, oxide and semiconductor, and performs the action of turning current on and off by applying voltage to an electrode called a gate.

That is, an insulated gate bipolar transistor is a transistor having a structure that combines a MOSFET and a bipolar transistor. Its characteristic is that it has the characteristics of high-speed operation of MOSFET and high withstand voltage and low on-resistance of bipolar transistor.

Despite its different structures, silicon (Si) has been used as a component material for more than half a century. This is because Si has good electrical properties and is easy to process into a variety of component structures .

However, current Si-based power semiconductors are no longer able to meet the high-level technical requirements required to further reduce the power consumption of various electrical and electronic devices. In order to overcome this bottleneck, the use of new materials such as silicon carbide (SiC) and gallium nitride (GaN), which are more suitable than Si as power semiconductor materials, is expanding.

As a key device for realizing a sustainable society, power semiconductors have begun a complete paradigm change after half a century.

SiC and GaN have characteristics suitable for power semiconductors in terms of multiple physical properties such as breakdown electric field strength (affecting withstand voltage), mobility (affecting operating speed), and thermal conductivity (affecting reliability). If devices can be developed that take advantage of their outstanding characteristics, power semiconductors with higher performance can be produced.

Today, SiC-based MOSFETs and diodes have been commercialized and used in DC/AC converters in electric vehicle motor drive inverters and solar power regulators.

GaN-based HEMT (High Electron Mobility Transistor) has also been commercialized. HEMT is a high electron mobility field effect transistor that can achieve high-speed switching by connecting semiconductors of different properties and inducing high mobility electrons. Currently, gallium nitride HEMTs are used in AC converters for ultra-small PCs and smartphone chargers.

However, to fully realize the potential of SiC/GaN, it is inseparable from the simultaneous development of passive components such as capacitors and inductors.

AC/DC converter (for data center servers, etc.) circuit example using GaN-based power semiconductors

For example, in an AC/DC converter circuit using GaN HEMTs, which were introduced to reduce power consumption in data center servers, multiple GaN HEMTs are used (above).

Utilizing GaN HEMT's characteristic of high-speed switching at high voltages, the switching frequency (operating frequency) of power electronic circuits can be increased. In a circuit with a high operating frequency, the reactance value of the capacitor and reactor built into the circuit and the inductor in the signal processing circuit can be very small. Generally, low-reactance components are smaller in size, allowing for smaller circuit boards and increased power density. Similarly, in inverter circuits that drive motors in electric vehicles, etc., SiC MOSFETs can be introduced to achieve miniaturization of peripheral components , thereby achieving miniaturization and weight reduction of the entire inverter circuit.

On the other hand, power supplies that perform high-speed switching at high voltages generate high levels of noise, which may adversely affect the operation of peripheral devices. Power supplies built with SiC or GaN power semiconductors switch at higher frequencies, further increasing the risk. Therefore, stricter noise countermeasures are required than when using conventional power electronic circuits. In this case, it is necessary to use noise-suppression components designed for high-voltage, high-current, and high-frequency circuits rather than those used in previous circuits.

In addition, for transformers, which are particularly bulky components among passive components, there is also a need for small transformers that operate at higher frequencies. Thin planar transformers based on power semiconductors based on SiC and GaN have been developed and put on the market.