Definition of Wireless Charging
Wireless charging technology, also known as induction charging technology or non-contact induction charging technology, originates from wireless power transmission technology. It refers to a technology that the device with battery uses the response equipment to send and receive the induced AC signal at the receiving end and sending end without the help of conductor wire and using electromagnetic wave induction principle or other related AC induction technology.
(1)Convenience. contactless, one to many charging.Compared with the normal charger, it reduces the trouble of plugging, and also avoids unsuitable interface and poor contact. The elder people can also use it conveniently. A charger can charge multiple loads, and a member can buy a charger to meet the needs of the whole family.
(2) Universality, wide range of applications.
As long as the same wireless charging standard is used, wireless charging can be used on the different devices with different manufacturers.
(3) New trend, good user experience.
(4）It has a universal standard
The mainstream wireless charging standards are Qi standard, PMA standard and A4WP standard
Qi standard: Qi standard is a wireless charging standard launched by the world’s first standardization organization, wireless charging Alliance (WPC, established in 2008), which adopts the most mainstream electromagnetic induction technology, and has two major characteristics of compatibility and versatility. As long as the products with Qi logo can be charged with Qi wireless charger. In February 2017, apple joined WPC.
PMA standard: PMA alliance is committed to building wireless power supply standards for mobile phones and electronic devices that meet IEEE standards, and has a leading position in the field of wireless charging. PMA also uses electromagnetic induction principle to realize wireless charging. At & T, Google and Starbucks have joined PMA alliance.
A4WP：Alliance for wireless power standard, launched in 2012, aims to establish technical standards and industry dialogue mechanism for wireless charging devices of electronic products, including portable electronic products and electric vehicles. A4WP uses the principle of electromagnetic resonance to realize wireless charging.
Principle of Wireless Charging
There are four ways to realize wireless charging technology: Electromagnetic Induction, Magnetic Resonance, Radio Reception and Capacitive Coupling.
Right now the main two technologies is magnetic induction technology and magnetic resonance technology, currently the mass-produced products are basically of magnetic induction technology.
How To Choose Magnetic Materials?
As we all know, coil, magnetic material and chip are the three elements of wireless charging system. The importance of magnetic material to wireless charging efficiency can be seen. Among them, magnetic materials cost for 21% of the total wireless charging cost and more than 50% of the total material cost.
We can refer to the article application of amorphous and nanocrystalline materials in wireless charging.Application And Prospect Of Nanocrystalline soft Magnetic Alloy Materials In Wireless Charging.
The charging frequency range of Qi charging standard is 100-200khz. The effect of using Fe based or Co based amorphous and nanocrystalline materials to make magnetic shielding sheet at low power is not very different from that of ferrite. At 10-20w power, the effect of 3 materials to make magnetic sheet is obviously better than that of ferrite.
Market with wireless charging mobile phones, basic use of amorphous or nanocrystalline shielding sheet. With the increase of charging power demand and the emergence of new charging technology, the goal of wireless charging industry is to improve efficiency and lower temperature rise.
Wireless fast charging is the key to improve the user experience, so the wireless charging power needs to be improved accordingly. However, the traditional ferrite materials have serious heating problems in wireless charging, which can not meet the demand of high-power charging.
In contrast, nanocrystalline materials are known for their high energy saving and charging efficiency, which has reached more than 90% at present. Moreover, nanocrystalline and amorphous materials are relatively thin. Under the same charging efficiency (about 78%), the thickness is only half of that of ferrite magnetic sheet, and can realize multi sheet sintering. However, the magnetic sheet produced by traditional materials can only be sintered in a single layer, otherwise the adhesive sheet will deform. In addition, from the application field, the biggest feature of nanocrystalline materials is that they can realize the mutual charging between mobile phones. They have great application potential in the future wireless charging, and stand out, gradually replacing ferrite as a new choice for many wireless charging manufacturers.
According to Apple’s supply chain news, due to the better B value and higher Q value of nanocrystalline soft magnetic, the new generation of iPhone wireless charging receiver coil uses nanocrystalline soft magnetic material.
As wireless charging has been favored by more and more manufacturers around the world, it shows that nanocrystalline will become the mainstream solution of wireless charging magnetic materials.
Amorphous/nanocrystalline magnetic sheet is prepared by amorphous and nanocrystalline tape with excellent soft magnetic properties such as low loss and high permeability. It can effectively reduce energy loss in wireless charging process, reduce heating and electromagnetic interference to the surrounding environment. It is the most advanced and excellent magnetic material applied in wireless charger in the world. At present, nanocrystalline magnetic shieLding sheet is in HUAWEI, xiaomi, Samsung, Apple have been promoted and applied.
Nanocrystalline Magnetic Sheet Preparation
At present, there are many disadvantages in the production process of shielding materials, such as the disorderly shape of the fragments after traditional rolling and crushing, and the gap size is not consistent (the gap with different sizes filled by colloid leads to different dielectric constant properties of magnetic materials between layers at a certain frequency), resulting in unstable performance (permeability difference is too large).
Etching process: Although the shape and gap width can be controlled, the etching process (the same as FPC etching method) is applied to the strip with adhesive layer. The strip with adhesive layer is etched. The etching Process as follow:
Amorphous and nanocrystalline alloy strip → degreasing → washing → drying → Filming→ exposure → developing → washing → etching pattern → washing → removing film → washing → pickling → washing → drying → inspection.
The above process is complex and the process is long. The adhesive tape passes through strong acid-base solution and etching solution. The adhesive layer performance changes and the gap is not easy to dry, and the strip is easy to oxidize. The cost is high, and all of them are treated and heated by chemicals, so the performance consistency is poor and the charging efficiency is low.
How to solve the problems in Nanocrystalline Magnetic Sheet Preparation?
In order to solve the above problems, a low loss magnetic shielding sheet preparation process is provided, which further reduces eddy current loss, further improves charging efficiency, low temperature rise, simple process, low cost and environmental protection.
The improved process makes the electromagnetic performance of the magnetic shielding sheet relatively average, magnetic loss is small, quality factor is high, the shape is truly uniform, the gap size is consistent, the colloid filling is better, the surface impedance is increased, the eddy current loss is reduced, and the charging efficiency is improved, and the stability of the magnetic sheet is good.
Diagram of Nanocrystalline Sheet Application Principle
Enhance the magnetic flux and improve the charging efficiency when magnetic sheet be used. Prevent leakage of magnetic field, reducing the level of EMI.
Nano Sheet Structure
Nanocrystalline Magnetic Sheet Characteristics
1. High permeability(500-1000)—Improve charging efficiencyGood balance and temperature characteristic.
2. Ultra thin, as low as 30μ m—The size can be produced according to customers.
3. High Bs—Reduce Magnetic sheet volume and thickness
4. Low core loss—Reduce eddy current losses, improve charging efficiency
5. Flexible material—Avoid magnetic flux leakage, convenient operation
Nanocrystalline Magnetic Sheet Performance Index
FAQs For Wireless Charging
1.How far is the charging distance of wireless charging?
Wireless charging can’t transmit as far as WiFi for the time being. The mature solution can only realize wireless charging within the distance of 10 mm, generally about 3-5 mm is better. This kind of wireless charging technology adopts magnetic induction wireless charging technology.
2. Is wireless charging harmful to human body?
There must be radiation, but it’s not big. Don’t worry about it.
There are several main reasons
Firstly,The power of mobile phone is only about 5W;
Secondly, the distance is short, only within 25px, and the radiation to the surrounding area is small;
Thirdly, there are magnetic shielding sheet at both transmitter and receiver, which can reduce the radiation around;
Fourthly, the working frequency is low, the working frequency is 110k ~ 205khz, and the radiation to human body is small.
3. What about the conversion rate of wireless charging?
Conversion rate has always been a concern for many people. Research by MIT shows that the loss of wireless charging technology is lower than that of wired charging technology. Wireless charging conversion rate is several percentage points higher than wired charging. High conversion is also the key factor for Wireless charger to be applied in the world. However, wireless charging technology is also limited by distance. In the future development, it is necessary to solve the problem of accurate positioning of wave band and magnetic field range for long-distance transmission.
4. What are the main difficulties of wireless charging technology in product application?
The core chip is one of the difficulties in the application of wireless charging technology. Precise radiation range control, magnetic field frequency and other control are all realized by the chip.
Market Size Of Wireless Charging
According to HIS technology consumer survey, more than 90% of users want their next phone to offer wireless charging. It is estimated that by 2020, more than 1 billion mobile phones with wireless charging function will be equipped, with a penetration rate of 55%; and intelligent wearable devices equipped with wireless charging function are expected to exceed 200 million by 2020. This also means that the total market size of wireless charging for consumer electronics alone is expected to reach US $10 billion. According to WPC’s forecast, the number of wireless charging receivers and transmitters will reach 550 million and 200 million respectively in 2018, which is expected to reach 1 billion and 400 million in 2020.
Except Mobile Phones, Where Else Can Be Used By Wireless Charging?
The biggest market for wireless charging is the mobile phone market. Of course, in addition to the mobile phone market, there are many other application fields, such as other consumer electronics markets, tablet computers, wearable devices, etc.
Small power wireless charger products, home market, office market, wireless charging products embedded in the home tea table, desk, bedside table, and office desk.
Application of medium and small power, except the mobile phone market, the game market, the toy market, as well as the electric toothbrush, electric shaver, and even the adult products market, are a huge market.
In the future, the wireless charging products like medium power will mainly be the home appliance market, such as PC, TV, household appliances and so on.
The future high-power wireless charging product market, such as electric vehicle market, power market, industrial market and so on.
In addition, markets with high requirements for waterproof are good applications for wireless charging.