Wide-bandgap semiconductor technology, information technology and AI are jointly revolutionizing power electronics. Soon, cognitive power electronics could react independently to incidents.
A new class of intelligent power electronics with additional AI functionality, known as cognitive power electronics, is currently under development.
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Power electronics is undergoing a fundamental transformation. Two extremely dynamic sectors are currently automotive electronics and energy technology, as Fraunhofer IISB, Fraunhofer ISIT and Fraunhofer IMS explain. In both areas of application, there is "a race for ever more efficient, powerful and cost-effective power electronics systems", according to the institutes. In addition, there are increased demands on the reliability and service life of electronic parts and components.
"Power electronics deals with the low-loss conversion of electrical energy using switching semiconductor components," explain the Springer authors led by Rik W. De Doncker in the German chapter on Power Electronics. Their fields of application range from smartphone chargers and high-voltage direct current (HVDC) transmission systems to battery-powered electric vehicles. Low-loss and cost-effective power electronic converters play a key role for electromobility in particular. "Power electronic converters are the links between the electrical energy sources, consumers and storage systems in electric vehicles. Among other things, they control all power flows, convert DC and AC voltages into each other, adjust voltage levels or drive electric motors," say the Springer authors.
Classic Silicon Components Reach Their Limits
With drive outputs of up to 1,000 kW and ranges of over 1,000 km, electric powertrains for electric cars have reached a new level, according to the Fraunhofer Institutes. The electrical converters would be in the megawatt class. This means that vehicle electronics are making strong inroads into the area of larger drives and opening up further fields of application. These include the emerging electrification of ships and aviation.
According to the Fraunhofer researchers, hybridization, i.e. the combination of combustion engines or jet drives with fuel cell technology and battery storage, promises major savings in fuel consumption and emissions. In addition to batteries, hydrogen is also becoming an interesting energy source. "Hydrogen technology in turn opens up its own technological possibilities, such as the design of cryogenic converters or the use of superconducting cables and motor windings," they say. However, classic silicon components are reaching their physical limits, making the use of semiconductors with a wide band gap such as silicon carbide or gallium nitride necessary.
WBG Promote Power Efficiency
Semiconductor components with a wide bandgap (WBG) promote power efficiency. As the Fraunhofer Institutes explain, WBG-based power components offer low passband losses, enable higher switching frequencies and can process high currents at high operating voltages. They also have very good thermal properties and are suitable for operation in a wide temperature range. "Customized device and process technologies such as VDMOS pave the way to fully exploit the potential of WBG semiconductors for power electronics," it says.
In terms of industrial applications, WBG semiconductor technologies SiC (silicon carbide) and GaN (gallium nitride) have made a significant impact on the market. "GaN and SiC offer different strengths. However, their advantages depend on the specific application. The benefits of SiC are due to its band gap. In addition to its electron mobility, the critical breakdown voltage is also high compared to silicon. GaN has an even larger band gap and much higher electron mobility", says Infineon Technologies in the article Drivetrain and Semiconductor Technologies in Future EVs from ATZelektronics worldwide 3-4-2023.
Another option is hybrid converters that combine both silicon and silicon carbide. As Aly Mashaly from Rohm Semiconductor emphasizes in the ATZelektronics worldwide interview, these architectures would make it possible to "allow the strengths of both technologies to be used optimally according to the operational requirements". Mashaly predicts "that the SiC market will reach the level of 8 billion US dollars before 2030", according to the expert for power electronic systems. The automotive sector in particular will account for the majority of this demand. He estimates that 70 % of global SiC demand will be accounted for by electromobility.
1200 V GaN HEMTs for the Energy Transition
However, as the Fraunhofer Institutes emphasize, there are still untapped advantages at system level in terms of cost, efficiency and construction volume. Current research activities are focused on gaining an in-depth understanding of component and material properties. As expert Mashaly points out, "the physical limits of wide-bandgap SiC and GaN technologies are far from being reached".
Researchers at Fraunhofer IAF, for example, are currently working on the realization of GaN-based HEMT technologies with reverse voltages up to and above 1,200 V, which could be used forCO2 reduction measures as part of the energy transition, such as bidirectional charging of electric vehicles. GaN HEMTs are intended to be an alternative to already available metal oxide semiconductor field-effect transistors (MOSFETs) made of SiC, which are very cost-intensive. And Hofer Powertrain and ETH Zurich are developing a three-stage GaN inverter that uses adaptive gate drivers and should enable even lower switching losses than before. This is intended to improve the performance and efficiency of drive systems for electrified vehicles.
Integration of ICT
Another trend in system development is the progressive integration of information and communication technology (ICT). Additional functions for monitoring, control and communication as well as intelligent capabilities are being implemented in the grids: on-board grids are developing into smart grids. According to the Fraunhofer researchers, this change has already been observed for some time in stationary grid technology, particularly in smart grids or local DC grids, as well as in battery systems for battery management.
The merging with data processing requires an increasing integration of digital technology components. "Microcontrollers and system-on-chips have long been used in drivers and control circuits for electronic circuit breakers," they say. Approaches from classic signal processing are also being used, for example to shape the alternating current waveform in order to save space and material-intensive passive filter components. Another example of this is modular multilevel converters, which consist of a large number of freely configurable inverter cells and can therefore cover a very wide range of applications and performance.
New class: Cognitive Power Electronics
A new class of intelligent power electronics with additional AI functionality is also currently being developed, known as cognitive power electronics, as the Fraunhofer Institutes explain. "These 'perceiving systems' are equipped with sensors to record various physical parameters and embedded electronics to record and analyze data in real time. This turns electric drives into integrated intelligent systems that are aware of their current operating status," they say. Based on machine learning methods, cognitive power electronic systems could make predictions and react independently to internal and external influences and events.
According to the researchers, it is already becoming apparent that the required performance characteristics of the new type of power electronics can no longer be achieved with existing semiconductor components and system properties. Power semiconductors based on materials with an extremely wide band gap and other innovative components, such as integrated attenuators or active circuit breakers, are in the pipeline. The Fraunhofer Institutes summarize: "The integrated power electronic system – the symbiosis of innovative power semiconductor technologies, microelectronics and artificial intelligence – is becoming a reality."
This is a partly automated translation of this German article.
