Is there room for growth in the development of electric vehicles?
Bigger battery? A denser charging network? Start with a little faster ejection? Or all of them?
The biggest pain point around electric vehicles is actually the anxiety and helplessness of people's hearts about electricity itself. Why the pain? Car companies are constantly exploring around this core and confused topic. Power change, large battery, high-density ternary lithium, these technologies are not how difficult it is to implement, nor how bad the effect is, but after landing, I always feel that I am almost something. People will still be worried, or will be anxious, and will give up buying electric cars that look good already. I can't tell what the pain is, I don't even know if it's pain, but it's uncomfortable everywhere. This is the last hurdle of the electric car's "hundred steps, ninety and a half".
Now it can be answered: what makes up for this is high-voltage electrical technology. From photovoltaic energy, future power stations, transmission networks, to user-side charging systems, electric vehicle control systems, fully stepped into the ranks of high voltage. How high is the high pressure? The current mainstream high-end pure electric platform is still dominated by 400V. The Porsche Taycan Turbo S premiered in April 2019, bringing with it the actual first 800V high-voltage electric platform. Two years later, the 800V platform is basically mentioned in the new generation of platforms of mainstream car companies. Compared to 400V, 800V brings higher efficiency and faster charging time. The charging time greatly increases the power under the blessing of 800V, and realizes 15 minutes of fast charging and replenishment.
A key shift is that the car and the battery it carries are not just judged by range, a new parameter, "the number of miles traveled per minute of charging", has become a new key to solving user pain points. This shows that the electric vehicle market must not only consider the size of the battery, the efficiency of the vehicle architecture, the charging efficiency, and even the upstream charging network must be upgraded to the same strategic height, in order to completely solve the so-called pain points of pure electric vehicles "no pain and no itch" embarrassing situation.
Then, if you want to achieve the convenience of electric vehicles like refueling in the future, the comprehensive ecology of high-voltage electrical technology is the only way. The ecological high-voltage technology not only greatly reduces the transmission loss, but also greatly shortens the transmission time, realizing the real super fast charging. For the electronic architecture of the car itself, the pressure based on the thermal management of the whole vehicle will be smaller, and the electronic response will be faster, which is equivalent to opening up the "second pulse of Ren Dou" for the whole body of the pure electric car. From the perspective of the source of electricity, the high-voltage leadership of photovoltaic + energy storage is not only the field of cars, but the real human energy revolution.
The soul that builds this "superpower" is the innovation of materials. A new controller MOSFET (Gold-Oxygen Half-Field Effect Transistor) based on silicon carbide (SiC) will lead this wave of high-voltage technology revolution.
▲ The key factor of electric vehicles: how far can you travel on a 1-minute charge?
Full ecological electrical system: a vast world, promising.
Without rushing to discuss the advantages of this critical component, let's return to the grand idea of all-ecological high-voltage electrification. When we discuss the new generation of electrified models, whether it is a pure electric car or plug-in hybrid, the car has become a part of the electrical ecology, electrification has broadened from power generation to electricity consumption and even electrical recycling, and the transformation of this industrial chain has brought huge imagination space to the top giant technology companies.
▲The electrification ecology covering multiple production and life application scenarios
One of the most critical components of electric vehicles is the inverter. In addition to motors and batteries, it is one of the largest label products for electrification. This vital unit converts direct current (DC) from the battery pack into alternating current (AC) to power the vehicle. The number of inverters generally required depends on the number of motors used on the vehicle (usually one per motor), and the highly intelligent architecture does not exclude a variety of more inverters. In addition, around the vehicle electrical architecture, a large number of key power supplies are served by each system, and suppliers of different systems actively deploy in different production and development processes.
▲Key power supply components for vehicles
▲Vehicle SiC module layout enterprises
▲Automobiles have become the largest application scenario of consumer-side high-voltage technology and lead technological change
Since Tesla first began to introduce SiC in large quantities in 2018, this "high-end technology" has gradually become the "standard" of major car companies' platforms. BYD Tang, Audi, etc., will gradually be listed explosively in 2023-2024. Audi's first 800V SiC SOP will be installed on the PPE platform. Mercedes-Benz's MMA platform will follow up in 2024-2025, in addition, volvo is also in the process of mass production of 800V. It is foreseeable that the 800V will be the standard for the main competitors in the future.
In addition, it is important to note that as another key pole in the ecology, photovoltaic power plants, as a larger-scale electric conversion infrastructure, can be said to be part of the future as part of the electric vehicle to consider the energy efficiency and operation of the entire life cycle. Power generation terminals of various sizes are very similar to energy storage terminals of high-voltage electric vehicles in some ways, and their inherent logic is not much different, with solar cells connected in series to obtain high voltage and parallel connections to obtain higher current/power. A major trend is to increase the voltage on the module string to take advantage of the correspondingly lower current to reduce power losses in connectors and wiring. Modules have typical nominal voltages around 500 to 1000 V, reaching 1500 V more and more frequently. Each string typically has its own relatively low-power inverter rather than a single central inverter, ensuring scalability, economy, and fault tolerance. At this time, the semiconductor components used in DC/DC boost converters and inverters are not less affected than in the whole vehicle, so if we look at it from an overall point of view, it seems that this switch connects the entire electric power, from the sun to the various vehicle facilities that we can drive, use and entertain, which is the most important "meridian" outside the battery.
▲ From 2018, when Tesla first began to introduce SiC in large quantities, this technological revolution will gradually penetrate rapidly from cars to the entire electric transportation travel ecology
Silicon carbide SiC, no doubt the trend
Different suppliers/developers around the world will have their own product vision for future voltages and standard final solutions, and interestingly, from that point of view, the end of high-frequency high voltage is SiC. That is to say, the best solution available is the SiC module, in every way. Depending on how the switch is applied in the future, higher frequencies and higher voltages, even if the conduction power consumption of The SiC is actually higher than that of IGBT (more on this article), it will not stop the application-side burst drive history from finally choosing the SiC.
▲The end point of high-frequency high-pressure materials at different angles is SiC
As can be seen from the 2020-2026 market forecast report released by Yole, SiC has clearly become a dual consensus between technology and the market, and the proportion is constantly increasing, with a compound annual growth rate of more than 25%.
▲The explosive growth of the SiC market and the forecast of various growth areas
Advantages and disadvantages of IGBT and SiC modules
IGBT is undoubtedly the key to the core technology of today's automobiles. Compared to SiC MOSFETs, the two differ significantly in several ways: IGBTs are limited to the low frequency range due to their dynamic losses, but emit a constant saturation voltage at on, resulting in power dissipation proportional to the current. SiC MOSFETs can switch at frequencies of hundreds of kHz with low dynamic losses, but exhibit constant resistance at on. This results in power dissipation proportional to the square of the current. As the power throughput increases, the power consumption of SiC MOSFETs increases significantly, which is also a significant drawback. The figure shows the voltage drop of the 50A rated IGBT PIM and the 38A SiC PIM proportional to the conduction loss. The conversion point for optimal efficiency is approximately 25A (125°C). That is to say, for the conduction loss of 25A, or even below 30A, the loss disadvantages of SiC MOSFETs can be perfectly avoided, and from another point of view, high voltage (low current) is the perfect partner for SiC.
Pressure drop at 125 °C for IGBT PIM and SiC MOSFET PIM
When comparing dynamic switching operations, the advantages of SiC MOSFETs are highlighted. Dynamic loss is directly related to frequency. That is to say, one turn on and one off will also bring losses. For example, when the IGBT and SiC MOSFETs switch at the same low frequency (e.g. 16 kHz) in the range of 20 to 30 A, the conduction losses are similar, but the dynamic losses are very different. In the "on" process, the conduction loss of the two devices is not much different, and the IGBT is relatively slightly worse, but the absolute value is still not very large. But the energy loss of the "off" is much higher (a few carriers, which must be extracted from the n-drift region of the component when shut down, but are present when the collector voltage rises, thus creating transient power losses).
Comparison of Dynamic Losses of IGBTs and SiC MOSFETs at 16 kHz (On Semi)
In PV boost converters that provide 500V/25A input and 800V DC output at 95°C case temperature and 16kHz, the overall power dissipation is significantly reduced when using SiC semiconductors, with a total loss of about one-third of that of an IGBT circuit, in addition to higher reliability at lower junction temperatures.
▲At the same boundary temperature, the loss of SiC-based MOSFET components is significantly reduced
Taking hybrid vehicles as an example, the IGBT module specifications are generally 600V ~ 1200V/200A ~ 800A, its own heat generation is larger, and its motor, engine, etc. are in the front compartment of the car, the space is closed, the heat is concentrated, if the temperature exceeds the junction temperature of IGBT 125 ° C, it will cause the module to overheat and burn. Therefore, heat dissipation has always been a top priority in IGBT design, especially in the management of high-frequency dynamic switches. SiC directly reduces the temperature from the heat source, on the one hand, it can reduce the complex layout and pressure of thermal management, and on the other hand, it can also be equipped with a more high-frequency compact controller to improve the function.
Therefore, from this idea, in addition to energy saving, the higher efficiency of SiC can also achieve a smaller, cheaper radiator arrangement, the same radiator has a lower temperature rise, or the same radiator and temperature rise have a higher power throughput. Compared to the 16 kHz IGBT, the 40 kHz SiC MOSFET shown in the table has almost the same temperature rise, but the power consumption is still reduced by 40%. Although the system size is smaller, efficiency is increased by more than 50%. In addition, increasing the frequency can also reduce the boost inductance by about three times. This saves cost, size and weight.
▲The same temperature rise shows that even under the original temperature control strategy, SiC has a very considerable energy-saving effect
In the low current region, the on-state voltage of the MOSFET is lower than that of the IGBT. However, in the high current region, the on-voltage of the IGBT is lower than that of the MOSFET, especially at high temperatures. Because they have higher switching losses than unipolar MOSFETs, IGBTs are typically used at switching frequencies below 20 kHz, and the application of hybrid controllers is not excluded based on this feature, and control strategies are targeted to achieve optimal efficiency and optimal utilization of cost processes.
▲Si IGBT and SiC MOSFETs have their own advantages in different regions
Loss is not the only difference between IGBTs and SiC MOSFETs. Unlike IGBTs, body diodes are integrated in MOSFETs. This can be an advantage in power converters that switch in reverse mode or in third quadrant operation. In the case of IGBTs, in this case an additional shunt diode will be required to encapsulate in the module.
In addition, because the on-resistance of SiC MOSFETs decreases as a new generation of devices are introduced, the advantages are infinitely amplified in high-power applications in a growing number of applications, which is also urgently needed for high-voltage electrification and complex vehicle control circuits.
▲The main structure and parameter characteristics of different transistors
However, SiC needs to be carefully designed to get the most out of it, not simply changing materials. For example, the gate drive of IGBTs and SiC MOSFETs seems to be similar, but the drive of SiC is more critical for low conduction loss, such as the need to be as close as possible to the absolute maximum of 25V in the design process, developers often use 20V voltage, leaving a certain safety margin, and so on. In addition, the final technical threshold is the packaging process and thermal management structure design, which directly distinguishes the application level of different enterprises.
BorgWarner technology: double-sided water cooling + advanced packaging process
BorgWarner (Delphi Technologies) is the first company in the industry to mass-produce an 800 V silicon carbide (SiC) inverter, one of the key components of an efficient next-generation electric and hybrid vehicle that significantly extends the range of electric vehicles (EVs) and halves charging time. The reason for this is the new SiC inverter operating at 800 V. Automotive engineers can now more flexibly optimize other powertrains: larger ranges or smaller batteries; ultra-fast charging or smaller, lighter, cheaper wiring harnesses; and more vehicle kinetic energy when braking, further expanding vehicle range.
▲BorgWarner inverter
▲ Viper technology concept - advanced packaging process
The new package structure, named Viper, is centered on the integration of multiple switches into a unified enclosure and centralized thermal management. Double-sided cooling is a patented technology that directly reduces heat in the power module and provides better reliability in a more compact design. Viper's improved reliability and compact size also allow the inverter to be integrated into other components, even mounted directly on an electric motor or transmission, while being small enough to be packaged with other power electronics. What's more, Viper's unique semiconductor chip size and heat sink material allow the inverter to quickly expand and adapt to different power levels. As a result, it can be used for multiple voltage and current levels required for complete and plug-in hybrids and electric vehicles.
▲Double-sided cooling concept
The new SiC Viper power switch is mounted in the same inverter package as the current silicon switch and simplifies the design of multiple vehicle performance options. The integrated DC/DC converter and inverter provide significant cost savings for OEMs. The core technological innovation of this inverter is its patented Viper power switch, which also combines SiC with high integration and unique double-sided cooling, using the combination of the advantages of the two to greatly reduce heat generation, cooling water temperature can be controlled at about 65 °C, to achieve high-frequency high-power applications.
▲ BorgWarner SiC Viper
Viper's process requirements are higher, and whether it can achieve a certain yield rate is a key issue for the company's production considerations. In general, the transformation of single-sided to double-sided is the most direct solution to the problem of heat dissipation, so that derivative problems such as volume and design methods can be optimized, which ultimately affects the efficiency and compactness of the overall architecture. At present, improvements in this technology alone can optimize up to half of the volume.
▲Viper double-sided cooling design and compact packaging process are fully optimized in terms of volume, weight, efficiency and so on
From the perspective of the production and design of car companies and customers, Haodu parts give engineers more imagination space and more production space in the factory. The technology simultaneously reduces the amount of silicon carbide required per switch, thereby significantly reducing costs. Viper's design reduces power loss by up to 70% while increasing power density, which is not only effective for a single model, but also depends on the driving cycle. That said, customers are good or bad, but manufacturers can use these increased efficiencies when designing powertrains to increase vehicle range, improve overall performance, or reduce battery costs, so that this flexibility allows more options to uniquely match consumers, or offer different models—including the ability to weigh battery size, cost, and vehicle range; and to match more varied marketing methods at multiple prices. The 800 V SiC inverter for electric vehicles can be expanded and adapted to lower and higher voltage systems, providing manufacturers with multiple voltage and current levels required for PHEV and BEV, covering multiple powertrain technology routes in the future.
800v is just a number, not the end
800v electrical system will definitely not be the end of high-voltage electrical technology, 900-1200V technology is already on the way, more innovative technologies will continue to build a new electrical society. But it is undeniable that from now on, the important switch of the fully electrified ecology from power generation to electricity consumption has been turned on.
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