In order to further expand the application of silicon carbide in automotive traction inverters, ON Semiconductor has launched a new 900V silicon carbide power module VE-TracdirectSic, which is packaged in six-pack and is divided into 17mΩ and 22mΩ on-resistance. In the test simulation, ON Semiconductor compared the VE-TracdirectSic with the VE-TracdirectiGBT820A, in the case of using the same battery, the silicon carbide power module can improve the efficiency by 5%, which means that the battery life can be improved by 5%.

Electric vehicles already account for the new 5% in 2021 as the trend towards vehicle electrification takes off. According to statistics, by 2030, the share of electric vehicles will exceed 30%, and the number of electric vehicles on the road will reach 15 million.

There are also many demands on the power modules in the main inverter in automotive electrified traction systems. First of all, it is naturally more power, and more power means more torque. Then there's greater efficiency. With limited battery capacity, higher efficiency means less losses, which equals longer range.

There are also higher voltages. At present, 400V battery has become the mainstream standard, but 800V models such as Porsche Taycan, Hyundai IONIQ5 ">800V model">800V model">800V model">800V model">800V model">800V model">800V model">800V model ">800V Model">800V Model">800V Model">800V Model">800V Model">800V Model">800V Model">800V Model">800V Model">800V Model">800V Model">800V System has begun to rise. With the surge in demand for fast charging, 800V fast charging solutions and 800V batteries are about to become popular, the AP1510SG-13 inverter must be able to withstand such high pressures.

Second, the weight is lower, and the reduction in weight also makes the vehicle lighter, reducing motor load, which in turn improves durability. Finally, the volume is smaller to allow for shaft insertion, providing more interior space. Given the above needs, the industry generally sees SiC as a next-generation solution to replace IGBTs.

Silicon carbide in automotive traction systems

So, what are the advantages of silicon carbide replacing IGBTs in current automotive powertrains? Silicon carbide power modules are power modules with silicon carbide semiconductors as switches, which are used to convert electric energy efficiently in automotive inverters. First, compared to silicon materials, silicon carbide is harder, more suitable for sintering processes, and has better mechanical integrity.

Another key feature of silicon carbide is its high breakdown voltage. At the transition from 400V to 800V, the breakdown voltage must be doubled. The breakdown field strength of silicon carbide is 2500kV/cm, and the silicon material is only 300kV/cm, which means that silicon carbide can achieve higher breakdown voltage at lower thicknesses.

Then there's the proverbial heat dissipation capability. The thermal conductivity of silicon carbide is more than four times that of silicon, so it dissipates heat faster, reducing the cost of cooling electric vehicles. Of course, the most important property is naturally its forbidden band width. The 3.23eV band gap of SiC brings higher electron mobility and lower losses, as well as faster switching.

In order to further expand the application of silicon carbide in automotive traction inverters, ON Semiconductor has launched a new 900V silicon carbide power module VE-TracdirectSic, which is packaged in six-pack and is divided into 1.7mΩ and 2.2mΩ on-resistance. There are not many such low resistances on the market. Probably only power modules such as WolfspedCAB760M12HM3 can compare with them, and the on-resistance reaches 1.33mΩ.

In the test simulation, ON Semiconductor compared the VE-TracdirectSic with the VE-TracdirectiGBT820A, in the case of using the same battery, the silicon carbide power module can improve the efficiency by 5%, which means that the battery life can be improved by 5%. This efficiency improvement also serves to reduce costs. If mileage is a fixed goal, the use of SiC power modules can reduce battery capacity, thereby reducing battery costs by 5%. Finally, if a low-resistance silicon carbide power module such as 1.7mΩ is used, the power can be increased by 29% compared to the 820AIGBT.

During an online session on its SiC products, ON Semiconductor product line manager Jonathan Liao gave his views on the advantages of SiC products and 800V batteries in the future. First, the higher breakdown voltage of silicon carbide will further promote the popularity of 800V batteries, achieving the same power at lower currents, thereby reducing heating, while higher voltage batteries will increase the power density of on-board inverters.

At the automotive level, silicon carbide enables higher voltages, lower currents, and fewer cross-section cables and connectors, further reducing vehicle weight. In addition, silicon carbide can achieve higher charging power, such as more than 35kW, which can achieve 80% charging power in 20 minutes. Johnny Liao also mentioned that although the trend of 800V has begun to appear, high-performance models will be the first to adopt the 800V architecture in the future.

Not only that, but in addition to the gel 6-pack modules, ON Semiconductor is also preparing to launch transfer-molded SiC modules in the future. Using advanced interconnection technology to further improve the power density, it can even reach operating temperatures above 200 degrees Celsius, expanding the usage scenarios of SiC modules.

Barriers to the Popularization of Silicon Carbide

So, with these advantages, why is the use of silicon carbide not popular in automotive inverter solutions? Jonathan Liao gives five reasons and the current state of silicon carbide. The first is cost. I believe that many people who know silicon carbide know that the price of silicon carbide is higher than that of silicon-based IGBTs. However, Jonathan Liao said that the cost of silicon carbide is currently higher, but this is mainly reflected in the cost of modules. However, if the cost of the whole vehicle is considered, the cost of the silicon carbide solution will be lower. As mentioned above, silicon carbide can reduce the cost of batteries, which are often the most expensive part of a vehicle solution.

Then there's the issue of supply. At present, only a few manufacturers provide silicon carbide materials, such as Wolfspeed, Showa Denko, GTAdvanced Technologies (GTAT) and so on. Currently, many semiconductor companies' silicon carbide products are still provided by contracts with these suppliers. With ON Semiconductor's acquisition of GTAT this year, ON Semiconductor has the ability to produce silicon carbide substrates and epitaxy, and its fabs are also starting to prepare to move from 150mm to 200mm.

The second is technology maturity. Jonny Haley pointed out that compared with IGBT, the technological maturity of silicon carbide is indeed not as good as the latter. However, from the speed of development of the technology, R&D investment and practical application, both SiC semiconductor manufacturers and automakers believe that SiC technology can already be used in automotive traction systems.

It was also difficult to implement because it was a fast switching device, so we had to challenge the original design a bit. Finally there is the packaging issue. At present, in order to popularize IGBT-like packaging solutions, with subsequent development, silicon carbide solutions will gradually turn to more advanced packaging solutions to improve service life, heat dissipation and even performance.

summary

Although there are still many challenges to replace IGBTs with silicon carbide, judging from the determination of semiconductor giants to invest firmly, this wide-bandgap semiconductor will soon become popular in the automotive market. Under the fierce competition from foreign manufacturers such as ST, Wolfspeed, Infineon, ROHM, ON Semiconductor, etc., the rise of domestic silicon carbide enterprises is not easy.