It ranges from car breakdown and "brake failure" to a screw or a seat stain. Xiaomi SU7 （ parameter | picture ）Up to now, almost all of them have been noticed by magnifiers and even microscopes. The power of flow is vividly demonstrated by Xiaomi SU7. So that when Zhiji Automobile was "rubbing the flow", it mistakenly marked the front motor of Xiaomi SU7 as non SiC silicon carbide, which attracted a lot of ridicule. However, the dispute over the use of SiC silicon carbide in Xiaomi cars has not stopped. Recently, news about the low yield of SiC silicon carbide chips used by Xiaomi SU7 has been exposed, which has led to hidden dangers in vehicle safety. If so, should it be Xiaomi Motors or the supplier system that carries the blame?
The drive system is the core contradiction, and the "pot" cannot be deducted from the supplier?
From the online reports, we can find that the contradiction is more concentrated in the drive system of Xiaomi SU7. For example, in May, the Xiaomi SU7 purchased by a car user in Fujian suffered a drive system failure when the mileage was only 39 km. SiC silicon carbide has obvious advantages in breakdown voltage, switching frequency and thermal characteristics. Therefore, SiC silicon carbide chips have been popularized on the high-voltage platform of pure electric vehicles. Even if it is not an 800V high-voltage platform, in order to improve the efficiency of the drive system and reduce energy consumption, such as Xiaomi, Tesla, etc., SiC silicon carbide chips will also be used on 400V voltage platform models.
Will the "pot" come from the supplier of SiC silicon carbide chips? According to known information, Xiaomi SU7's top equipped dual motor version uses Infineon's SiC silicon carbide chip product, while the single motor version uses the solution from United Auto Electronics. Infineon is naturally one of the leading enterprises in the field of SiC silicon carbide chips. At first, it seems that the target is United Auto Electronics? The problem is that the information disclosed on the Internet is just the top dual motor version of Xiaomi SU7. As for the SiC silicon carbide chip of the single motor version, it has become a "secondary contradiction".
Of course, there is another explanation. As is known to all, the Xiaomi SU7 only has a top mounted two motor four-wheel drive version that uses a high-voltage platform. All single motor rear drive versions use a 400V voltage platform. So, is there a possibility that the high voltage will cause Infineon's SiC silicon carbide chip to be more unstable? But as mentioned above, Infineon's SiC silicon carbide chip products are in the leading position in the industry. Not only do we purchase many automobile enterprises, but also the 800V high-voltage platform is not new at present. If the product excellence rate is significantly lower than the vehicle specification level demand, the problem should not be exposed until Xiaomi SU7.
According to this logic, the contradiction of the problem returns to Xiaomi Auto itself. For example, the vehicle MCU calibration capability can also be compared to the problem of computer motherboard and BIOS calibration. In this way, it is not surprising that the chip itself comes up. But before the so-called conclusion, another case may provide more reference.
Tesla learned from the previous experience that "the root cause" is too radical in performance?
As early as 2022, Tesla has filed more than 127000 vehicles in China at one time Model 3 Recall plan of vehicle models. It covers some imported and domestic models from early 2019 to early 2022. The reason given by Tesla at that time was that there might be minor manufacturing differences in the power semiconductor components of the vehicle rear motor inverter, which caused the inverter to fail to control the current normally, which might cause the vehicle to fail to start or lose power when driving. This explanation points directly to the rear motor. At that time, Tesla's rear motor was the first to use SiC silicon carbide chips, while the front motor used conventional IGBT semiconductor components. Therefore, although Tesla did not say clearly that year, the industry still focused on the consistency of SiC silicon carbide chips.
Interestingly, Infineon involved in this round of Xiaomi Automobile is one of the two giants of Tesla SiC silicon carbide semiconductor supplier together with STF Semiconductor. Of course, this also does not mean to point the spearhead back to the Yingfeiling family. The failure to clear up this matter in those years was largely limited by the global semiconductor material production difficulties at that time. Obviously, it is not the time for Tesla to push the pot with suppliers. However, today, if there are any potential safety hazards, we have to make things clear.
The simplest logic is to control variables in reverse. Since the drive system chip supplier, voltage platform, etc. are not fixed values in the two "cases". The possibility of similar mistakes in MCU calibration between Xiaomi and Tesla after more than two years is removed. The remaining common point of the two is actually the driving motor made of SiC material. To be more specific, Tesla and Xiaomi were both the industry leaders in ultra-high speed motors during the exposure period. From this calculation, it can be summarized as a rough equation: ultra-high speed motor+SiC silicon carbide chip=unstable. We can also disassemble it further. Under the background of DC motor and relatively fixed voltage, the high speed condition can be equivalent to the high current demand. Then, the final answer should be: ultra-high speed (ultra-high current)+SiC silicon carbide chip=unstable.
OTA can alleviate, but the eradication needs the help of suppliers
How to solve this problem? We can first refer to how Tesla did it. At that time, the OTA solution adopted by Tesla was the most popular among car companies, and consumers were also relatively relieved. Optimize the motor control software through remote upgrade and monitor it, so as to replace the rear inverter after relevant faults occur. Obviously, the so-called "optimizing motor control software", to use a more familiar description, is "frequency reduction". Of course, the motor performance cannot be like that of 3C digital products. When it comes to frequency reduction, it is impossible to "wield a knife". However, it is obviously necessary to sacrifice certain limiting properties to extend the life of SiC silicon carbide chips.
If Xiaomi SU7 encounters similar problems, Tesla's OTA method can also be copied. However, if we want to eradicate this problem, we still have to return to another key factor, that is, to improve the yield and quality of SiC silicon carbide chips. After all, high speed motors are the inevitable development direction of pure electric vehicles. Including Xiaomi, the threshold has been raised to more than 20000 revolutions. The follow-up Xiaomi V8s motor can even increase the speed to 27200 rpm. Since driving technology is progressing, semiconductor technology can only choose to keep pace.
The problem is that Infineon, as a giant in the industry and a supplier of Xiaomi high-performance semiconductor materials, has never been an IDM enterprise. In fact, this is also in line with the general operation of the semiconductor food chain, but the rising star Wolfspeed is "not very law-abiding", covering the whole process from raw material substrate to chip manufacturing. Back to Infineon, as an industry giant, since it does not manufacture substrates, it is necessary to increase the procurement channels of silicon carbide wafers to ensure its own shipment volume and costs. In recent years, Infineon has enriched the background supply system, including many Chinese suppliers.
Infineon's consistent practice is to adopt black box treatment for all substrate supplies. That is to say, the purchaser cannot know his source of goods, and who is the supplier. Even if different suppliers are removed, the quality may fluctuate. When the 6-inch substrate is still the absolute mainstream at the moment, whether the SiC silicon carbide chips obtained by automobile enterprises are likely to come from the 8-inch substrate with a higher yield rate is ambiguous.
However, according to the "back door" left by Infineon, core customers are still likely to get preferential treatment for selecting the source of the background. This is obviously good news for Xiaomi V8s motor. After all, according to the loading rhythm, the motor will be launched next year (2025). However, Infineon has disclosed that the pace of the introduction of 8-inch silicon carbide wafers is almost in step with it. Backward, it is hard to say whether the two enterprises have a tacit understanding in this respect. Compared with Tesla, which ultimately chose to weaken the SiC silicon carbide application, Xiaomi Automobile seems to continue to gamble on the driving performance at higher speeds.
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