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Applications of silicon carbide devices in electric vehicles

2019-04-09
Applications of silicon carbide devices in electric vehicles
 
With the vigorous development of industry, global energy consumption increases year by year.In China, motor vehicle pollution has become an important source of air pollution and an important cause of haze and photochemical smog pollution.Energy conservation and emission reduction has become an important subject in the development of automobile industry.Therefore, vigorously developing new energy vehicles is a strategic measure to achieve energy conservation 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 put forward higher requirements.However, due to material limitations, traditional si-based power devices have approached or even reached the intrinsic limit of their materials in many aspects. Therefore, automobile manufacturers have high hopes for the new generation of silicon carbide power devices.
 
With silicon carbide as a representative of the third generation of semiconductor, and single crystal silicon compared with conventional semiconductor materials such as gallium arsenide, has obvious advantages, such as high heat conductivity, high breakdown voltage, high saturated electron drift velocity, high bonding, Gao Huaxue stability, strong resistance to radiation, etc., determine the silicon carbide has an irreplaceable position in many fields.Mainly as follows:
 
(1) SiC has a high thermal conductivity (up to 4.9W/cm•K), 3.3 times higher than Si.SiC materials, therefore, the cooling effect is good, in theory, SiC power devices can work under 175 ℃ junction temperature, so the radiator can significantly reduce the volume, suitable for making high temperature device.
 
(2) SiC has a high breakdown field strength, its breakdown field is 10 times of Si, so it is suitable for high voltage switches, the maximum power processing capacity is strong, making SiC materials suitable for making high-power, high-current devices.
 
(3) SiC has a high saturation electron drift rate, which is twice the value of Si, almost no attenuation at high field, and its high field processing ability is strong, therefore, SiC materials are suitable for high-frequency devices.
 
SiC single crystal is also the most mature third-generation semiconductor material in preparation technology.SiC is therefore one of the ideal materials for making high temperature, high frequency, high power and high voltage devices.
 
As we all know, the IGBT power module with high power density, high voltage and large current is the most core component in the inverter. The higher the power density is, the more compact the design of the electric drive system will be, and the greater the power will be under the same volume.Due to the high current density of SiC devices (such as Infineon products up to 700 A/cm2), at the same power level, the package size of all SiC power modules is significantly smaller than that of Si IGBT power modules, greatly reducing the volume of power modules.
 
On the other hand, since all power conversion is performed by IGBT, the device itself does not have more space to dissipate heat, nor can it dissipate heat by adding fans or other means, which requires IGBT itself to have a good cooling function.Theoretically, SiC power devices can work under 175 ℃ junction temperature, so the volume of the radiator can be significantly reduced.
 
In addition, compared with conventional silicon IGBT, the conduction resistance of SiC devices is smaller, and the conduction loss decreases.In particular, SiC SBDs has a small reverse recovery current, a large reduction in switching loss and a large improvement in system efficiency.
 
To sum up, silicon carbide devices have great potential applications in electric vehicles.SiC devices can significantly reduce the size, weight and cost of power systems.Improve power density and system efficiency.Making it an ideal component in EV and HEV electric drive devices will also revolutionize the power drive system of electric vehicles.
 
With the support of national policies, the sales of domestic new energy vehicles are growing rapidly.According to data from the ministry of industry and information technology, 379,900 new energy vehicles were produced in 2015, a four-fold increase year-on-year, while 331,100 new energy vehicles were sold, a 3.4-fold increase year-on-year. Among the global annual sales of over 500,000 new energy vehicles, China's market contributed more than half.It is planned that the accumulative sales volume will reach 5 million in 2020, with a compound growth rate of more than 50%."Energy conservation and new energy vehicle industry development plan (2012-2020)" points out that the accumulative sales volume of new energy vehicles will reach 5 million in 2020.

At the same time, in the made in China 2025 issued by the state council in 2015, it is clearly proposed that by 2020, the annual sales volume of China's self-owned brand new energy vehicles 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.