“The trend of vehicle electrification is accelerating. In the past two years, affected by the epidemic and the shortage of chips, the overall performance of the global auto market has been poor, but new energy vehicles have thriving, continuing the strong growth momentum of the past few years, and doubling sales in 2021. Some hesitant German and Japanese traditional car manufacturers have also launched their own pure electric products, as the main new products to promote, the development prospects of electric vehicles are bright.
Author: Doctor M
The trend of vehicle electrification is accelerating. In the past two years, affected by the epidemic and the shortage of chips, the overall performance of the global auto market has been poor, but new energy vehicles have thriving, continuing the strong growth momentum of the past few years, and doubling sales in 2021. Some hesitant German and Japanese traditional car manufacturers have also launched their own pure electric products, as the main new products to promote, the development prospects of electric vehicles are bright. However, slow charging and range anxiety have become more widespread as EV penetration increases. At present, there are two main methods to solve the problem of slow charging. One method is to replace the battery, that is, the car goes to the power exchange station to replace the already charged battery pack, which is referred to as battery replacement; the other method is to use high-power fast charging to shorten the charging time. , hoping to achieve a similar goal of “charging for five minutes and lasting 200 kilometers”.
It is faster to replace the battery, but the battery pack needs to be designed to be detachable, and a large number of replacement stations need to be built, and resources need to be invested in the unified management of the replaced batteries, which will undoubtedly greatly increase the early deployment cost. Most manufacturers have chosen the high-power fast charging route. There are also two routes for increasing the charging power, that is, a high-current route or a high-voltage route.
The advantage of increasing the current is that the current voltage architecture does not need to be modified, but high current will generate high heat dissipation, so it is easy to overheat when the battery is charging, so it is necessary to improve the thermal design of the car to match the high current mode, and the high current mode The related components, connectors and wire harnesses are required to have high current-carrying capacity. The current-carrying capacity of connectors and wire harnesses is proportional to their diameter. Large currents undoubtedly require thicker wires, which will bring higher costs. Tesla’s super fast charging solution adopts a high-current solution with a voltage of 400V and a maximum charging current of 600A, which can achieve a charging power of 250kW. Such a high charging current value poses great challenges in the thermal management technology of related modules.
The large voltage mode is another option. For example, by replacing the 400V charging voltage with 800V, the same charging power as 400V can be achieved with half the current value, which can reduce the requirements for the current carrying capacity of components, connectors and wiring harnesses, simplifying Thermal design difficulty to reduce cost and extend service life. However, using the 800V charging architecture requires redesigning the entire power supply architecture including battery packs, electric drives, vehicle chargers, etc., and the core components must have the ability to work normally under 800V DC voltage.
Silicon carbide power tube replaces IGBT
In the current mainstream 400V architecture, the electrically driven power tubes mainly use IGBT devices, but the withstand voltage of IGBTs is usually not higher than 650V, which is basically not applicable to the 800V architecture. Even the high-voltage IGBT using the super junction process has a working voltage of less than 900V, and its volume is much larger than that of ordinary IGBTs, which undoubtedly brings difficulties to the interior space layout and heat dissipation design.
At this time, the advantages of silicon carbide (SiC) power transistors are reflected. Silicon carbide is a wide bandgap device, and its breakdown field strength is ten times that of silicon material devices, so it can achieve higher resistance with smaller dimensions. The current silicon carbide power tube can support a MOSFET blocking voltage of 1700V, which is very suitable for high-voltage applications. In addition, silicon carbide devices have low on-resistance and low leakage current when turned off, which can significantly improve the efficiency of power modules; the thermal conductivity of silicon carbide devices is three times that of silicon-based devices, and can withstand higher operating temperatures, thereby reducing heat dissipation requirements. ; while the reverse recovery current of silicon carbide devices is extremely low, and the switching action can be performed at 3 to 5 times the operating frequency of the corresponding silicon-based devices, thereby reducing the performance requirements for capacitors and magnetic components, and can be used with lighter weight and lower cost. Low capacitance and inductance to realize the corresponding module, which is meaningful for electric vehicles to reduce weight and extend battery life.
According to Wolfspeed data, in electric vehicle powertrains, replacing silicon devices with silicon carbide can increase power density by up to 80%, reduce power loss by 80%, and reduce the size by half.
Figure 1: Silicon carbide devices greatly improve the performance of electric vehicle high-voltage powertrains (Source: Wolfspeed official website)
For example, the C3M0040120D sold on Mouser Electronics’ official website is a SiC MOSFET that is very suitable for 800V charging architecture. The device uses Wolfspeed’s third-generation planar MOSFET technology, which improves the Cgs/Cgd ratio and has higher hard switching performance. C3M0040120D has a blocking voltage of up to 1,200V, while the on-resistance is only 40 milliohms, and the maximum operating current can reach 66A. It has low switching loss, high energy efficiency, and low heat dissipation requirements. It adopts a small TO-247-3 package, which is very suitable for electric vehicles. High voltage applications such as motor drives, solar inverters and high voltage DC-DC power supplies.
Figure 2: Wolfspeed C3M0040120D (Source: Wolfspeed Product Brochure)
Another Wolfspeed E3M0120090J is also available on Mouser Electronics’ official website. E3M0120090J also adopts the third-generation silicon carbide MOSFET technology, with low parasitic parameters, fast switching speed, and the source-drain breakdown voltage Vds reaches 900V. It is packaged in TO-263-7. The product has passed AEC-Q 101 and PPAP certification, suitable for electric vehicle charging, UPS, solar Inverter and other applications.
Figure 3: Wolfspeed E3M0120090J (Image source: Wolfspeed Product Data Sheet)
By replacing silicon-based IGBTs with silicon carbide devices, not only the overall performance of the device can be improved, the difficulty of heat dissipation design can be reduced, but also the cost of the entire vehicle can be reduced. Although silicon carbide power devices are more expensive than silicon power devices such as IGBTs, due to their low loss and light weight, they can effectively increase the battery life of the entire vehicle, thereby reducing the cost of the entire vehicle. The DC power converter in Figure 4 is implemented with 650V silicon devices, which requires more devices, a complex current sharing control circuit, and a relatively high conduction loss. Using Wolfspeed silicon carbide power transistors, the circuit is simple, and the switching frequency is high, which allows the use of smaller, lighter magnetic components.
Figure 4: Advantages of SiC devices in DC-DC power converters (Source: Wolfspeed official website)
Wolfspeed estimates that the cost of replacing IGBT devices with silicon carbide devices will increase by 75 to 150 US dollars, but after the replacement of this batch of devices, due to low loss, simple circuit and light weight, even in the 400V architecture, it can be increased by 6%-10 % of battery life, thereby saving $600 to $1,000 in battery costs, leaving manufacturers with options to reduce costs ($525 to $850 less battery capacity) or increase the battery life experience. In the 800V architecture, the advantages of silicon carbide technology will undoubtedly be more obvious.
Film capacitors are widely used
As mentioned earlier, the high-voltage architecture will affect all core components in the corresponding circuit, including passive components such as capacitors and inductors, which are mainly used for various filtering and protection functions.
Among them, film capacitors have been widely used in the power supply architecture of electric vehicles because of their advantages of high voltage resistance, high reliability, high safety, and non-polarity. As shown in Figure 5, in the high-power charging system of electric vehicles, the input filter , AC to DC conversion, DC link (DC-Link), DC voltage conversion to output filtering, film capacitors will be used.
The film capacitor adopts non-inductive winding, the current path is short, the equivalent inductance ESL and equivalent resistance ESR are relatively small, and it can withstand a large current without heating. Moreover, film capacitors have self-healing properties, that is, if a weak point in the capacitor is broken down by an instantaneous high voltage, the film capacitor can recover its normal function through the self-healing ability. From the point of view of the film capacitor processing technology, the thickness of the metal coating evaporated on the plastic film is only 20 to 50 nanometers. If it is weak somewhere, dielectric breakdown may occur when an instantaneously high voltage is passed, and the resulting high temperature will turn the insulating medium into a high-voltage plasma gas that is released and evaporated together with the metal plating near the breakdown point. Lose. The rapid expansion of the high-voltage plasma gas cools down within a few microseconds, thereby terminating the discharge phenomenon before the voltage drops significantly, restoring the insulation near the previous weak point, thereby realizing the self-healing function. This feature makes film capacitors especially suitable for scenarios with high safety requirements such as automotive, industrial, and electric power. In the 800V architecture, higher requirements are placed on the temperature resistance, voltage resistance, reliability and stability of capacitors. It is expected that the amount and unit price of film capacitors will increase to a certain extent.
Figure 5: Overview of TDK capacitor products (Source: TDK official website)
Mouser’s B2563x MKP film capacitors from manufacturers EPCOS/TDK are ideal for DC-Link applications. The B2563x MKP film capacitors have an expected life of 100,000 hours and are rated for a capacitance range of 50µF to 400µF. The DC voltage range supported by this series is 500V to 1,200V. Users can choose capacitors with corresponding withstand voltage values according to specific applications. For example, the B25631B1956K200 supports a voltage range of 1,200V.
Figure 6: EPCOS/TDK B2563x MKP film capacitors (Image credit: Mouser Electronics)
In the 800V system, there are more and more high-power applications, which puts forward higher requirements for the rated working current of the Inductor. The HPL505032F1 inductor for automotive power circuits sold by TDK from Mouser Electronics is an inductor suitable for high-power applications. The HPL505032F1 uses a low resistance frame made of high saturation flux material, and achieves high power efficiency through high permeability and low loss ferrite. The current rating of this inductor is increased to 1.5 times that of the previous generation, and can accommodate up to 40A to The 50A current, the magnetic flux cancellation effect of the proprietary structural design helps control noise, and the frame integrating the external and internal electrodes reduces the risk of open and short circuits, ensuring high reliability. The HPL505032F1 is AECQ-200 qualified and is ideal for powering camera modules in ADAS.
Figure 7: TDK HPL505032F1 Inductor for Automotive Power Circuits (Image source: Mouser Electronics)
As a leading manufacturer of inductor products, TDK provides a variety of automotive-grade inductors for users to choose from. The BCL power circuit inductor sold on Mouser Electronics’ official website is a wire-wound power inductor. The coil is completely sealed with magnetic materials. Magnetic leakage can be minimized. The inductor adopts TDK’s proprietary material technology and structural design, uses metal magnetic material as the core material, and reduces the size by about 35% compared with products using traditional ferrite materials with similar properties, achieving high performance in a small size. Inductance, the maximum inductance value of the existing model is 47uH, and the maximum inductance of the new model that will be launched this year is 101uH. The connection structure design between the BCL series winding wire and the external electrode reduces the risk of open circuit and ensures high reliability. The operating temperature range is -55 to +155°C. The rated voltage of the BCL series is 40V, suitable for ADAS and various ECU applications low-voltage power supply circuit.
Figure 8: Inductors for TDK BCL power circuits (Image source: Mouser Electronics)
The TDK SPM-VT-D automotive inductors, available from Mouser Electronics, are another family of metal-composite wirewound inductors that use metallic magnetic materials, so they also feature miniaturization and low DC resistance (Rdc). VT-D automotive inductors also meet the AEC-Q200 standard and are suitable for power circuit applications of automotive modules such as engine control modules, LEDs, ADAS, and BCMs.
Figure 9: TDK SPM-VT-D automotive inductors (Image source: Mouser Electronics)
Wire Harnesses, Isolators and Contactors
One of the main reasons for adopting the high-voltage architecture is that the high-current mode is close to the upper limit of the current carrying capacity of the vehicle wiring harness (500 to 600A). The high-voltage architecture can reduce the current-carrying requirements of the wiring harness, but it is still necessary to pay attention to whether the wiring harness insulation layer meets the high-voltage requirements. Electric vehicles generally have two voltage levels: A-level voltage does not exceed 60V (DC) or 30V (AC RMS value), B-level voltage range is 60V to 1,500V (DC) or 30V to 1,000V (AC RMS value), Therefore, high-voltage wiring harnesses are usually in the B-level voltage range, but the insulation performance of some high-voltage wiring harnesses only supports 600V, which meets the requirements of 400V voltage system, but if it is used in 800V system, it is obviously necessary to choose a wiring harness with a higher withstand voltage. Similarly, connectors and isolators should also pay attention to changes in withstand voltage requirements.
Contactors are also products worth paying attention to. Electric vehicles require fast and reliable switching of high-voltage, high-current DC circuits in many places. The switching of high-voltage and high-current DC circuits will generate arcs, and arcs will lead to the reduction of the contactor’s cutting ability and electrical life. Therefore, high-voltage contactors that can quickly cut off current are required to have good arc-extinguishing ability to ensure the reliability of the application.
Figure 10: TDK high-voltage contactor switching circuit has better performance and is safer (Source: TDK official website)
The EPCOS / TDK HVC series of high-voltage contactors sold on Mouser Electronics’ official website meet the requirements of electric vehicle high-voltage DC switching applications. The contactors are designed with ceramic seals for excellent reliability in harsh environments and high-speed arc suppression. Supporting continuous operating current up to 500A, this series can be used in a variety of applications in electric vehicles that require fast and reliable switching operation. Among them, the B88269X3340C011 in the new HVC43 series supports voltages up to 1,000V and rated currents up to 250A. It adopts non-polar design, small size and light weight. It is designed to quickly shut down lithium-ion batteries in vehicles, charging stations or energy storage systems. High DC current, ideal for EV 800V architecture.
Figure 11: Outline drawing of EPCOS/TDK B88269X3340C011 product (Image source: Mouser Electronics)
Since Porsche launched the Taycan, the first mass-produced electric vehicle model with 800V architecture, many manufacturers including BYD, Xiaopeng, Weilai, Ideal, Great Wall, BAIC, GAC and other manufacturers have announced their 800V architecture plans. The 800V architecture products of these manufacturers are planned to be Coming to market in 2022 or 2023, the popularity of 800V architecture will definitely change the development trend of most automotive power supply architecture component technologies including battery packs, power tubes, capacitors, inductors, contactors, isolators and wiring harnesses, Wolfspeed Manufacturers that have done a good job in technology accumulation with TDK and other companies have undoubtedly taken the lead in this technological change.
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