Application of magnetic materials in wireless charging technology

The main magnetic materials used in wireless chargers are NdFeB permanent magnet, NiZn ferrite thin magnetic sheet, MnZn ferrite thin magnetic sheet, flexible ferrite magnetic sheet; As the main components of wireless charging technology, the magnetic separator made of soft magnetic ferrite plays a role in increasing the induced magnetic field and shielding the interference of the coil in wireless charging equipment.

The wireless charger has higher requirements on the performance, size, and reliability of soft magnetic ferrite material, and the receiving end has higher requirements on it. According to the placement of the receiver, the wireless charging transmitter is divided into fixed position type, single-coil free position type, and multi-coil free position type. These transmitters have different requirements for ferrite products. Fixed position chargers are positioned with NdFeB permanent magnet chips. Terminals need to be placed in a fixed position for charging and maximum charging efficiency.

The Qi standard stipulates that the operating frequency of such a design is 110kHz~205kHz. The fixed position charger has a high resonant frequency and generally uses NiZn ferrite thin section with small loss and good high-frequency magnetic shielding effect as the magnetic separator. A single-coil-free position charging device has a drive inside the coil to move on a flat surface.

By automatically detecting the placement position of the terminal equipment, the coil is moved to this position, so that the position of the coil is consistent with the receiving position of the terminal. To realize charging and improve the charging efficiency, such a design can allow the terminal to be placed on the charging pad at any position for charging. Qi standard stipulates that the working frequency of this kind of charger is 140kHz. Because the coil needs to move, the magnetic separator is required to have high reliability, so the magnetic separator is generally used in the casting process of flexible magnetic sheets.

Multi-coil position chargers charge multiple terminals at the same time and are lined with multiple coils that cover most of the charging dock area. Thus, the terminal can be placed relatively freely on the charging base, and the charger will automatically select several efficient transmission coils to supply power. According to the Qi standard, the working frequency of a multi-coil free-position charger is 105kHz~113kHz, and MnZn power material with high Bs and low loss characteristics is generally selected for the magnetic separator.

Permanent magnet materials used in wireless charging systems can enhance the magnetic flux between transmitting and receiving coils and improve transmission efficiency. On the other hand, as a positioning device between transmitting and receiving, it facilitates the rapid and accurate positioning of terminal equipment. Small wireless charging equipment with NdFeB permanent magnet material; Permanent magnet ferrite material can be used to replace NdFeB permanent magnet material for large wireless charging equipment to reduce the cost.

For example, the University of British Columbia (UBC) uses contactless dynamic magnetic coupling, or MDC, to charge EVs wirelessly at a distance of 102mm to 152mm, using the magnetic field interaction of two permanent rotating magnets.