Wireless Power Transfer (WPT) technology is an emerging charging technology, which transmits electrical energy from the transmitter device to the receiver device through the principle of electromagnetic induction, and then charges the load through the power conversion circuit, so as to achieve contactless charging. Wireless power transfer technology eliminates the limitations of traditional wired transmission, and shows significant flexibility and security, and has been widely commercialized in the field of low-power wireless charging, such as mobile phones, smart wearables, etc. In recent years, with the development of new energy vehicles in the direction of intelligence and networking, the wireless charging technology of electric vehicles has attracted much attention and is gradually moving towards commercial application. This article will focus on the application and technical advantages of silicon carbide devices in wireless charging of electric vehicles.
Overview of wireless charging technology for electric vehicles
The wireless charging technology of electric vehicles is based on the theory of magnetically coupled wireless power transmission to realize the charging of power batteries, which is the most mainstream technical route at present. Figure 1 shows a schematic diagram of the structural composition of the wireless charging system of electric vehicle, and there is no cable connection between the transmitting side and the receiving side, wherein the transmitting side comprises a wireless charging power supply, a transmitting coil, and the receiving side comprises a receiving coil and a vehicle-mounted converter.
Composition of wireless charging structure for electric vehicles
The technical advantages and applications of silicon carbide in the field of wireless charging of electric vehicles
The first task of the electric vehicle wireless charging system is to achieve efficient power transmission, so efficient and safe power conversion is the core of the electric vehicle wireless charging system. Compared with silicon (Si) materials, SiC has higher thermal conductivity, larger bandgap width, higher critical breakdown field strength and higher electron saturation drift velocity, and the physical properties of SiC materials make it more suitable for high temperature, high frequency, low loss, and high power working conditions, and its application in the field of wireless charging of electric vehicles can not only effectively improve power density and system efficiency, but also reduce system loss and the volume and weight of receiving equipment.
In terms of the power conversion circuit of the electric vehicle wireless charging system, there are mainly high-frequency inverter circuits, high-frequency rectifier circuits and PFC rectifier circuits, and Figure 2 is a typical application of the topology schematic diagram of the electric vehicle wireless charging system, with an output voltage of 800V. On the transmitting side of the wireless charging system, a high-frequency inverter circuit is composed of Q1-Q4 to provide high-frequency alternating current for power transmission for the transmitting coil; On the receiving side of wireless charging, D1-D4 form a high-frequency synchronous rectification circuit on the receiving side, which converts the high-frequency alternating current received by the receiving coil into the direct current required for charging. A total of 6 (Q1-Q4, D3, D4) 1200V SiC MOSFET devices are selected for the inverter circuit and synchronous rectification circuit as the core conversion link of the system. Due to the excellent performance of SiC MOSFETs, in actual use, the wireless charging system can generally obtain 90%~93% AC and DC conversion efficiency from AC power input to the on-board battery.
Circuit topology diagram of the wireless charging system for electric vehicles
Application of silicon carbide in wireless charging system of electric vehicles
In addition to SiC MOSFETs, silicon carbide Schottky diodes (SiC SBDs) are ideal rectifiers for wireless charging systems due to their low forward voltage drop and fast switching characteristics, which can significantly reduce rectification losses, and the excellent temperature characteristics of SiC SBDs enable them to maintain high efficiency in high-temperature environments. In addition to the use of SiC SBDs in high-frequency rectifier circuits, the PFC rectifier circuits in the pre-stage of high-frequency inverter circuits include rectifier bridges and boost circuits, and SiC SBD devices are generally used.
The world's first wireless charging system for electric vehicles on an 800V high-voltage platform
In recent years, with the rapid development of new energy vehicle technology and market, the industrialization process of wireless charging for electric vehicles at home and abroad has been fully opened, and wireless charging has been configured by major automobile manufacturers in different models. In 2021, BAIC released the ARCFOX Alpha S Huawei HI version designed with a 7.5kW wireless charging system, which is the world's first product to support 800V high-voltage charging, and in 2022, SAIC and FAW will also put into production models equipped with 11kW wireless charging systems and sell them to the market. In 2023, FAW Group will build China's first 100-meter-level dynamic wireless charging demonstration road for electric vehicles at the Changchun Science and Technology Innovation Base, equipped with a wireless power transmission system with a power level of more than 20kW. As an advanced semiconductor material, SiC has many excellent characteristics, and the comprehensive use of silicon carbide power devices in the power conversion link has become the mainstream choice of the above-mentioned wireless charging system.
Summary and afterword
Electric vehicle charging infrastructure is an important part of the new energy vehicle industry, of which power electronic materials and devices are the basic technology of the industry. As an advanced semiconductor material, silicon carbide devices have superior physical properties, and their application in the field of wireless power transmission, including wireless charging of electric vehicles, will significantly improve their performance and user experience. With the advancement and innovation of wireless power transfer technology, silicon carbide devices will continue to play a key role in driving the development of wireless power transfer technology in the direction of more efficient, smaller and more reliable.
Source: Xingan Technology
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