The charging methods of charging piles are mainly divided into AC charging and DC charging. (1) The essence of the AC charging pile is a socket with control, which mainly includes AC ammeter, control board, display screen, emergency stop knob, AC contactor, charging cable and other structures. Transformer rectification hardly involves power devices. (2) The structure of DC charging piles is more complex, including charging modules, main controllers, insulation detection modules, communication modules, main relays and other parts. Among them, charging modules, also known as power modules, are core components with technical thresholds in the charging pile industry , accounting for about 50% of the total cost of charging piles. At present, consumers are most interested in the DC fast charging mode, but the charging piles in the DC fast charging mode require very large charging power and very high charging efficiency, which need to be realized through high voltage.
The charging module is the core component of the DC charging pile. A charging pile is usually formed by connecting multiple charging modules in parallel. For example, a 120kW charging pile can be composed of eight 15kW charging modules, or four 30kW charging modules. The greater the output power of a single charging module, the higher the power density, which can effectively optimize the space in the pile. The components of the charging module include semiconductor power devices, integrated circuits, magnetic components, PCBs, capacitors, chassis fans, etc. Among them, the cost of semiconductor power devices accounts for about 30% of the total cost of the charging module, which is a key component of the charging module and an electronic device. The core of power conversion and circuit control in China.
The main part where SiC is currently applied to charging piles is the power device in the charging module, especially the AC/DC converter and DC-DC converter. According to Wolfspeed data, a 25kW charging pile module needs about 16-20 1200V silicon carbide MOSFET single tubes. The mainstream 15kW charging pile modules on the market generally use 4 or 8 silicon carbide MOSFETs, and the specific number depends on the on-resistance value and output current of the selected device. An urgent problem to be solved in the new energy vehicle industry is "mileage anxiety". To increase the charging speed, the output power of the charging pile needs to be increased, and the charging voltage or current needs to be increased. According to Wolfspeed data, the current commercial mainstream fast charging piles in my country have a power of 100-150KW, and it takes 40-27 minutes for an electric vehicle to charge a 400KM mileage. If the charging pile adopts a 350KW high-power fast charging system, the charging time required for a 400KM mileage can be greatly shortened to 12-15 minutes. Increasing the charging power can be achieved by increasing the current or voltage. However, if the charging power is increased by increasing the current, many problems will be caused. Therefore, increasing the voltage to achieve high-power fast charging has become the industry's most choice.
In order to increase the charging speed of electric vehicles and alleviate mileage anxiety, more and more OEMs are deploying 800V high-voltage platforms. The 800V high-voltage system usually refers to the system whose voltage range of the high-voltage electrical system of the whole vehicle reaches 550-930V, collectively referred to as the 800V system. Porsche Taycan is the world's first mass-produced 800V high-voltage platform model, and has increased the maximum charging power to 350KW. In addition, the Audi e-tronGT, Hyundai Ioniq5 and Kia EV6 all use the 800V high-voltage platform. At the same time, domestic car companies are also moving towards the 800V high-voltage platform. In 2021, BYD, Geely, Jihu, GAC, Xiaopeng, etc. will successively release models equipped with 800V platforms.
For DC fast charging piles, upgrading the charging voltage to 800V will greatly increase the demand for SiC power devices in charging piles. The reason is that the use of SiC modules can increase the power of the charging module to more than 60KW, while the design of MOSFET/IGBT single tube is still at the level of 15-30kW. At the same time, compared with silicon-based power devices, SiC power devices can greatly reduce the number of modules. Therefore, the small size advantage of SiC has unique advantages in the application scenarios of urban high-power charging stations and charging piles. With the increase in demand for supercharging and fast charging, full SiC modules have begun to be widely used in charging piles. According to the official website parameters of various companies, most high-performance charging piles with 800V architecture use full SiC modules. At present, the penetration rate of SiC in charging piles is not high. Taking DC charging piles as an example, according to CASA calculations, the average penetration rate of SiC power devices in electric vehicle charging piles only reached 10% in 2018. However, with the advent of the 800V voltage era, the penetration rate of SiC will continue to rise. The China Charging Alliance predicts that by 2025, the penetration rate of SiC in China's charging pile industry will reach 35%.