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Sustainability Power electronics in the fight against climate change Prof Dr -Ing Thomas Basler Power Electronics Faculty of Electrical Engineering and Information Technology Chemnitz University of Technology The first step in meeting all our energy needs from renewable sources is in the saving of electrical energy Power semiconductors are already contributing here from LED lighting to variable speed drives for pumps motors and industry Advances in power electronics have achieved efficiencies which mean that despite strong increases in electrified applications overall electricity consumption did not increase Some studies state a further potential saving of 22% of atmospheric emissions through the application of power electronics Improving priceperformance points Meeting the high demand on both sides of the supply and demand equation starts with improving the performance of the chips Lower conduction and switching losses – such as with the improved RDS ON of the second generation of trench gate SiC MOSFETs – helps increase the number of chips per wafer This enables delivering more devices from the fabrication plants and ultimately reduces priceperformance points There are exciting developments in packaging where new housings and materials are coming into play And also new frontside interconnection technologies such as for the frontsideonly connection required for lateral GaN devices or clips Foils and copper bond wires also offer interesting perspectives for getting the current out of even smaller chips One trend is an increase in the variety of moulded discrete devices such as small and larger halfbridge housings or the many new solutions using topside cooling These use less material are cheaper than the corresponding frame modules and can be used in modular selfdesigned parallel configurations as is the case in Tesla EVs Other drivers come from increasing the range of applications for wide bandgap devices For example its low switching losses influenced the choice of SiC for achieving new levels of efficiency for solar inverters But now we are seeing interesting possibilities for wind turbine applications and traction applications where SiC MOSFETs in the 3 3 kV power module class could be used significantly increasing efficiencies over today’s IGBT solutions The ever improving reliability is also important In the case of traction applications these systems are in use all day over a 30-to 40-year lifespan This for example has been achieved using sintering on the back of the chips and copperbased interconnection technologies on the front Challenges for testing One of the biggest challenges is proving the reliability of the combinations of new chip new packaging and new interconnection technologies Power cycling tests are most important but this means improving the testing methodologies or using innovative testing procedures such as including new temperaturesensitive electrical parameters as part of the power cycling test of GaN HEMTs New tests are also needed particularly dielectric testing in the form of a gate switching stress test for SiC devices to gauge the gate oxide stability This was not a mode that needed to be qualified for silicon devices but in the meantime it is mentioned in the ECPE’s AQG-324 testing standard for automotive power modules Often this is driven by the needs of the demanding applications and not least by time pressure to get a solution to market This has led to the theoretical understanding of SiC and GaN lagging behind Sibased counterparts and the need to standardise tests for SiC and GaN to get reliable comparable results Tradeoff between effort and performance Of course new is not always better in all respects The much smaller chip sizes and active thicknesses of SiC devices for example mean they reach very high temperatures and their failure limits much faster than IGBTs under short circuit conditions And despite all the hype around SiC and GaN it is often silicon IGBTs that are available to meet the immediate demand for energy transition and electrification Obviously this will change as the capacity of SiC and GaN fabs increase in the coming years IGBTs are also likely to remain dominant in high voltage and high current applications like DC energy transmission Or for applications where cost rather than space and losses are the main driver such as in variable speed The fight against climate change needs a strong growth of sources like wind turbines and photovoltaics For example reaching the official German target of 80% renewable energy by 2030 – though the target should be 100% by this date to avert climate disaster – means installing 8 GW of wind and 19 GW of solar a year As part of this power electronics is a key element for generation for feeding energy into the public grid and for transmission from the producing regions to where it is needed by industrial and private users – not least in the transition to high and medium voltage DC transmission and distribution – as well as to control the stability of those grids At the same time society is electrifying more from heat pumps and electric vehicles to the exploding energy demands of the IT systems running AI 14 PCIM Magazine 01 2024