The role of soft magnetic shielding materials in the wireless charging

- Jul 15, 2019-

Wireless charging has become popular in mobile phones, and samsung and apple have become standard devices. There are also a lot of products in the wearable space. In the future, wireless charging will be widely used in homes, offices, public places, transportation tools and transportation. There will also be widespread use of electric cars in the future.


I. wireless energy transmission (WPT) : smart phone, smart wear (small power)

The structure of wireless charging is similar to that of a transformer, which consists of a transmitter and a receiver, both of which are composed of coils and magnetic materials. There are different kinds of magnetic materials, such as ferrite, amorphous and nanocrystalline.


The role of soft magnetic shielding material in wireless charging

Magnetic shielding: provides a low impedance path for magnetic flux, reduces the magnetic field lines emitted to the outside, reduces the impact on the surrounding metal objects, and prevents eddy current and signal interference.

Magnetic resistance reduction: improve coupling coefficient, improve magneto-electric conversion efficiency, use fewer turns to achieve higher inductance coil, reduce coil resistance, reduce the efficiency reduction caused by heat (more turns, higher resistance).

Iv. Comparison of charging efficiency of nanocrystalline magnetic conducting tablets:

In order to simulate the real situation and conduct comparative test under the same conditions, the charging efficiency of nanocrystalline magnetizers with different thickness and ferrites with different permeability and thickness are compared. With the increase of the thickness, the charging efficiency is improving, but the nanocrystalline is not thicker, and it is basically saturated at 0.1mm. Therefore, when designing the wireless charging module, the nanocrystalline magnetic conducting plate does not need to be too thick, which will increase the material cost. The rule of ferrite is similar to that of nanocrystalline. The higher the permeability, the higher the charging efficiency, and the thicker the thickness, the higher the charging efficiency. However, at the same charging efficiency, the thickness of nanocrystalline magnetic sheet is only half of that of ferrite.

Fifth, the development of wireless charging of smart phones

In 2012, nokia introduced the Lumia 920, a wireless phone charged with a hard ferrite. HiKe 868, a mobile phone sold overseas in 2013, is designed to integrate wireless charging and NFC, with magnetic materials wpc-ferrite (rigid) and nfc-ferrite (flexible). 2015 landmark changes have taken place in mobile phone wireless charging, samsung launched the first wireless charging flagship model Galaxy S6, not only compatible with two kinds of wireless charging standard, WPC and PMA, also configure two NFC payment standard and MST, matching with the soft magnetic shielding materials besides ferrite, using amorphous magnetic piece for the first time, makes mobile phones do not only thin and elegant, but also improved the wireless charging efficiency. In 2016, samsung made further improvements, replacing all the magnetic materials with more advanced nanocrystalline magnetic conductivity sheets, leading the transformation of wireless charging technology and always taking the leading position. In terms of functions, NFC and MST near-field communication functions are added from the simple wireless charging. Magnetic materials gradually transition from ferrite to nanocrystalline.

6. Application cases

Nanocrystalline applications for wireless charging began with S7, a material that does all the work, replacing a combination of amorphous and ferrite. It is generally believed that used in the NFC soft magnetic materials, ferrite is the best, and that nanocrystalline doesn't fit, because in high frequency, the wastage of the nanocrystalline outweigh the ferrite, but samsung made a breakthrough, the successful application of S7 proved nanocrystals can be used in the NFC, then the S8 / N8 / A7 / J5 / J7 many models such as products, to expand the application of nanocrystalline from WPC to NFC and MST.

We have also made some attempts at the transmitter end. We have made several wireless charger products with nanocrystalline magnetic conductivity tablets, which are featured by multi-station and multi-function products, without any performance problems. The only problem is that the cost of magnetic conductivity tablets is higher than ferrite.

Vii. Mobile phone wireless charging development trend:

Function: the WPC - WPC + NFC - WPC/Airfule + NFC

Wireless charging -- wireless charging + -- charging at will

Power: the 5 W - 7.5 W - > 10 W - 15 W

Slow charge -- universal charge -- quick charge -- flash charge

Viii. Development trend of magnetic conductive film

Receiving end: absorbing material → ferrite → amorphous + ferrite → nanocrystalline

Nanocrystalline magnetic guide sheet:

Thin -- ultra-thin: 0.14→0.12→0.11 →0.10

High permeability, low loss -- high Q

Ix. Application and popularization

Low power: mobile phone, smart wear, etc

Medium power: computer, kitchen appliances, etc

High power: electric vehicles, roads and other infrastructure

The future, will be the wireless world, change life, change the world.