Development trend of wireless charging: TX & ferrite for high-power RX and nanocrystalline for thin RX

Selection of soft magnetic materials for wireless charging: ferrite in parallel with amorphous and nanocrystalline. At present, the selection of soft magnetic materials in wireless charging industry, including ferrite (manganese zinc ferrite, nickel zinc ferrite), amorphous and nanocrystalline, are applied. The advantages of amorphous and nanocrystalline materials lie in high saturation magnetic induction strength. Nanocrystalline materials have higher permeability and lower magnetic loss, and can be soft and ultra-thin, which is difficult for ferrite materials. The advantage of ferrite soft magnetic lies in the cost. Especially in the selection of high-power emitter, the cost of nanocrystalline soft magnetic may be more than twice that of ferrite soft magnetic. At this time, the cost performance advantage of ferrite soft magnetic material is highlighted. In ferrite, Mn Zn is suitable for medium and low frequency, and Ni Zn is suitable for high frequency resonance.

Emitter: ferrite is the mainstream, and different types of emitter have different requirements for soft magnetic materials. At present, the choice of magnetic materials at the transmitting end in the market adopts ferrite scheme. According to the placement mode of the receiving end, the transmitting end can be divided into fixed position type, single coil free position type and multi coil free position type. Different types have different requirements for the performance of soft magnetic materials. For example, single coil free position equipment can realize high-efficiency charging by automatically detecting the placement position of terminal equipment and moving the coil to a reasonable position. Since the coil needs to be moved, the magnetic separator is required to have high reliability. Generally, the flexible magnetic sheet made by tape casting process is adopted. Multi coil free position charging equipment requires the soft magnetic material at the transmitting end to have high saturation magnetic induction and low loss. Generally, Mn Zn power ferrite can be selected.

Table 1: comparison of different magnetic materials

Receiving end: amorphous and nanocrystalline are gradually dominant in the field of mobile phones, which requires high dimensional accuracy of soft magnetic materials. In the future, it will continue to develop to high frequency, miniaturization and thin, but ferrite is absolutely dominant in high-power applications. The receiving end of wireless charging is generally built in the terminal equipment. For low-power portable electronic devices such as mobile phones and smart watches, with the development of electronic components in the direction of high stability, high reliability, light, thin, short and wide adaptability, many electronic products turn to the development of integrated module and chip technology, and soft magnetic materials continue to be high-frequency, miniaturized Thin type is developed to meet the trend of increasingly thin film, miniaturization and even integration of magnetic components. Therefore, the selection of soft magnetic chips is gradually switched from ferrite to nanocrystalline scheme. At present, the high-end models pursuing light and thin have basically switched to nanocrystalline scheme. However, ferrite is still absolutely dominant in high-power applications such as wireless charging solutions for electric vehicles.

Table 2: development of soft magnetic materials towards energy saving and miniaturization

        The structural evolution of the soft magnetic market for wireless charging in the future: the high-end lightweight receiving end is switched to nanocrystalline, and the transmitting end and high-power receiving end are dominated by ferrite. From the market evolution trend, although amorphous and nanocrystalline soft magnetic properties have obvious advantages, if the cost breakthrough cannot be achieved through technological progress, the cost performance advantage of ferrite is more significant, and the initial permeability of ferrite soft magnetic is lower than that of amorphous and nanocrystalline soft magnetic, which is more suitable for high-power applications, It is expected that ferrite will still occupy a dominant position in the application of transmitter and high-power receiver in the future.