Power electronics: core components for a more sustainable world
Power electronics is playing an increasingly important role in the generation, distribution and use of electrical energy. As a result, it makes a significant contribution to the efficiency of increasingly sustainable societies.
Power semiconductors are irreplaceable for the transition to a climate-neutral and digital society. In particular, the industrial, renewable energy and automotive sectors are currently generating increasing demand and will continue to do so in the future. All with the goal of reducing CO2 emissions, increasing system efficiency and driving digitalization. Not surprisingly, the focus is on applications such as electric cars, photovoltaics and wind turbines.
Analysts at the Yole Group expect annual growth rates of just under seven percent between 2021 and 2027. Europe is the global market leader in this segment with a thirty percent share. And companies are continuing to invest, including here in Germany. Infineon, for example, is building a 300mm Smart Power Fab for analog/mixed-signal technologies and power semiconductors at its Dresden site. Vishay Intertechnology is building a 300mm fab for automotive MOSFETs in Itzehoe. U.S. company Wolfspeed is investing 2.75 billion euros in the world's largest factory for SiC power chips in Saarland, Germany. And Bosch plans to expand its wafer fab for SiC chips in Reutlingen by another 3,000 square meters by the end of 2023.
Silicon carbide and gallium nitride—examples for future power semiconductor elements
Gallium nitride (GaN) and silicon carbide (SiC) power electronic devices are increasingly being used alongside silicon-based technologies. These wide-bandgap semiconductors enable faster and lower-loss devices for inverters with efficiencies up to 99 percent. They can switch higher voltages at higher frequencies than is possible with silicon—and with less cooling. Shorter switching times significantly reduce energy losses and allow for more compact passive components such as inductors or capacitors.
Efficiency is therefore not limited to the electrical framework, but also includes a reduction in mass and volume. For electric vehicles, this means more range per charge.
Silicon carbide and gallium nitride chips are still much more expensive than their silicon-based counterparts. This is because they are more difficult to manufacture. For example, the cost of a SiC wafer is approximately 20 times higher than that of a silicon wafer due to the much more complex and lengthy manufacturing processes. Manufacturers hope to reduce costs by using 300mm wafer technology.
In addition, SiC and GaN power electronics are still in their infancy as a pacemaker technology. Improvements in stability and reliability, especially in long-duration applications, are still under development.
The four types of power semiconductors
Wide bandgap semiconductors are therefore not always the better solution. In addition to energy efficiency, cost, lifetime, power range and other constraints determine the design. Currently, there are four main types of power semiconductors available, in addition to hybrid technologies.
- Silicon-based IGBT
Silicon-based solutions continue to offer an competitive price/performance ratio and high reliability. In addition, new generations of Si IGBTs continue to reduce power losses and form factors while maintaining ruggedness. And with the advent of 300mm wafer technology, the industry is poised for significant volume growth.
Si-IGBTs are used in electric cars as control chips in the ECU, MCU, VCU, or as control elements in electrical components from power batteries to steering. Silicon IGBTs are also used in energy-intensive devices such as refrigerators, air conditioners, high-speed trains and electric vehicle charging stations. - Silicon-based MOSFETS
While IGBTs have established themselves as power switches for line voltage and drive applications, MOSFETs (Metal Oxide Semiconductor Field-Effect Transistors) are best suited for high frequencies and typically lower voltages. Here, switching power supplies with conventional Si MOSFETs continue to show efficiency improvements.
According to the Yole Group, the automotive industry in particular is demanding low-voltage MOSFETs for auxiliary units and high-voltage MOSFETs for DC-DC converters and on-board chargers as part of its electrification efforts. - Silicon carbide-based MOSFETs
Despite rapidly growing demand, discrete SiC MOSFETs are significantly more expensive than equivalent silicon devices. However, the advantages are increasingly offsetting the cost disadvantages. For example, they block voltages up to ten times higher than silicon structures and switch about ten times faster. The priority now is to improve the cost competitiveness of silicon carbide (SiC). Potential applications range from inverters for plug-in hybrid electric vehicles (PHEVs) and pure electric vehicles (EVs) to charging stations, servo drives and on-board chargers. - GaN semiconductors
GaN is emerging as a critical material for power semiconductors, along with silicon and silicon carbide. Like SiC, the wide-bandgap material offers higher power densities and efficiencies, especially at higher switching frequencies.
GaN semiconductors are used in components, parts and circuits of 5G base stations, but will also find a place in automotive electronics in the future. The material is currently being used in very specific, efficiency-driven applications such as wireless charging of e-cars, in 5G amplifier modules, or in converters for integrating microgrids into a smart grid.
