Application prospect of silicon carbide devices in electric vehicles

Release date：2019-07-01   Views：4055

With the vigorous development of industry, global energy consumption is increasing year by year. In China, motor vehicle pollution has become an important source of air pollution, which is an important cause of haze and photochemical smog pollution. The urgency of vehicle pollution prevention and control is increasingly prominent. Energy saving and emission reduction has become an important issue in the development of automobile industry. Therefore, vigorously developing new energy vehicles is a strategic measure to achieve energy saving and emission reduction and promote the sustainable development of China's automobile industry.

At present, the electric drive part of EV (pure electric vehicle) and HEV (hybrid electric vehicle) is mainly composed of silicon (SI) based power devices. With the development of electric vehicles, the miniaturization and lightweight of electric drive are required. However, due to material limitations, traditional Si based power devices have approached or even reached the intrinsic limits of their materials in many aspects. Therefore, automobile manufacturers have high expectations for the new generation of silicon carbide (SIC) power devices.

Compared with traditional semiconductor materials such as single crystal silicon and gallium arsenide, the third generation semiconductor, represented by silicon carbide, has obvious advantages, such as high thermal conductivity, high breakdown field strength, high saturation electron drift rate, high bonding energy, high chemical stability, strong radiation resistance, etc., which determines that silicon carbide has an irreplaceable position in many fields. The main contents are as follows:

(1) SiC has high thermal conductivity (up to 4.9 w / cm · K), which is 3.3 times higher than that of Si. Therefore, SiC material has good heat dissipation effect. In theory, SiC power devices can work at 175 ℃ junction temperature, so the volume of radiator can be significantly reduced, which is suitable for making high temperature devices.

(2) SiC has high breakdown field strength, and its breakdown electric field is 10 times that of Si. Therefore, it is suitable for high voltage switch and has strong maximum power processing ability, which makes SiC material suitable for making high power and high current devices.

(3) SiC has a high saturation electron drift rate, which is twice as high as that of Si, and almost no attenuation occurs in high field. Therefore, SiC material is suitable for high frequency devices.

SiC single crystal is also the most mature semiconductor material in the third generation. Therefore, SiC is one of the ideal materials for high temperature, high frequency, high power and high voltage devices.

As we all know, IGBT power module with high power density, high voltage and high current is the core component of inverter. The higher its power density is, the more compact the design of electric drive system is, and it can play a greater power in the same volume. Due to the high current density of SiC devices (such as Infineon products up to 700 a / cm2), the package size of all SiC power modules is significantly smaller than that of Si IGBT power modules at the same power level, which greatly reduces the volume of power modules.

On the other hand, because all power conversion is performed by IGBT, the device itself does not have more space to dissipate heat, nor can it be cooled by adding fans or other methods, which requires that the IGBT itself has a good heat dissipation function. In theory, SiC power devices can work at 175 ℃ junction temperature, so the volume of radiator can be significantly reduced.

In addition, compared with the traditional silicon IGBT, the on resistance of SiC devices is smaller, and the on loss is reduced; especially, SiC SBDs have smaller reverse recovery current, greatly reduce the switching loss, and greatly improve the system efficiency.

In conclusion, silicon carbide devices have great potential in the application of electric vehicles. SiC devices can significantly reduce the size, weight and cost of power system. Improve power density and system efficiency. Making it an ideal device in EV and HEV electric drive devices will bring revolutionary changes to the power drive system of electric vehicles.

With the support of national policies, the sales of domestic new energy vehicles have increased rapidly. According to the data of the Ministry of industry and information technology, in 2015, 379000 new energy vehicles were produced, with a year-on-year increase of 4 times, and 331100 vehicles were sold, with a year-on-year increase of 3.4 times. In the annual sales of more than 500000 new energy vehicles in the world, China's market contributed more than half. According to the policy planning, the cumulative sales volume will reach 5 million vehicles in 2020, with a compound growth rate of more than 50%. "Energy saving and new energy vehicle industry development plan (2012-2020)" points out that the cumulative sales volume of new energy vehicles will reach 5 million in 2020; at the same time, in 2015, the State Council issued "made in China 2025" clearly pointed out that by 2020, the annual sales of new energy vehicles with independent brands in China will exceed 1 million, accounting for more than 70% of the domestic market, and the sales volume of new energy vehicles will reach more than 145.

According to the industrial research, in the field of new energy vehicles, each charging pile needs 6 SiC power devices, the unit price of power devices is 40-80 yuan, and the total value is 200-500 yuan; the new energy vehicles need about 13 SiC power devices with unit price of 40-80 yuan and total value of 500-1000 yuan.

By 2020, the annual number of new energy vehicles in China will be 5 million, and the number of distributed charging piles will be 4.8 million. By 2020, the potential SiC market space contributed by new energy vehicles alone will exceed 10 billion yuan.

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