1. What is the situation of wireless charging and how to realize wireless charging?
What is going on with wireless charging? Just as the name suggests, don't plug in the cable. Similar to WiFi, it is very convenient. In theory, it can power mobile phones and other electronic devices anytime and anywhere.
However, wireless charging cannot be transmitted as far as WiFi for the time being. The current mature solution can only achieve wireless charging within a distance of 10mm. Generally, a distance of about 3~5mm is better. This type of wireless charging technology uses Magnetic induction wireless charging technology.
With the maturity of technology, it is expected that in the next 2 to 3 years, the charging distance of wireless charging can reach about 10~30cm, which can basically meet the demand for free and unfettered charging anytime and anywhere.
To realize wireless charging, a transmitter and a receiver are required.
The transmitter is a Wireless Charger, and the receiver is a mobile phone. There is a coil at the transmitting end, and a coil is also needed at the receiving end. The transmitting end transmits energy through the control board and the coil, and the receiving end receives energy through the control board and the coil, so that wireless charging can be realized.
The wireless charging situation of the Nokia mobile phone is shown in the figure below. The mobile phone can be charged on the wireless charger without connecting to the USB port for charging.
As long as there is a wireless charger and a mobile phone with wireless charging, it can be charged. The wireless charger can work normally if it is connected to an ordinary charger or laptop via MicroUSB, and the mobile phone with wireless charging can be charged on it. As shown in the figure below, you can charge by connecting the wireless charger via USB.
2. Why is wireless charging required?
Wireless charging has several advantages compared with traditional wired charging:
a. There is no thread winding, simple and beautiful, it looks comfortable, and the quality of life is higher;
b. Don't need to plug and unplug frequently, just put it and charge it, convenient and fast, so that your mobile phone will never run out of power;
c. Don't worry about the incompatibility of Samsung and Apple connectors, wireless chargers that support Qi and other standards can be charged;
d. There is no risk of electric shock when answering the phone when charging, completely avoiding the safety problem, and you can answer the phone at any time;
e. Make the battery work longer, because it can be charged immediately, so that the battery is not short of electricity, and the battery life is longer;
f. No wired interface is required, and many products can be made into fully enclosed waterproof products.
3. What is the principle and what technology? 
The principle of mobile phone wireless charging in the general sense is the process in which electrical energy is converted into a magnetic field, the magnetic field is transmitted through the air, and the magnetic field is then converted into electrical energy.
The principle of wireless charging is similar to that of a transformer in a popular sense. The magnetic field coupling loop of the transformer is a magnetic conductor, and the magnetic field coupling loop of the wireless charging is air, and the magnetic medium is different.
There are generally four technologies for wireless charging in the industry: magnetic induction technology, magnetic resonance technology, microwave technology and electric field coupling technology. The two major technologies that I have come into contact with are magnetic induction technology and magnetic resonance technology. Now the mass-produced products are basically products of magnetic induction technology.
The mainstream technologies are magnetic induction technology and magnetic resonance technology. Let’s review basic physics, electric and magnetic fields.
Magnetic induction wireless charging technology
That is, when an alternating electrical signal is passed to the transmitting coil, the alternating electric field will produce a changing magnetic field through the transmitting coil, and the changing magnetic field will have a magnetic coupling effect on the coils around it. According to Faraday’s law of electromagnetic induction, the changing magnetic field will produce electric field.
Therefore, the magnetic field generated by the transmitting coil will pass through the receiving coil, and the receiving coil will generate an electric field. If a load is connected to the receiving coil, a current will be generated.
4. What is the wireless charging efficiency, how fast is the charging, and is there radiation?
Charging efficiency generally refers to the overall efficiency of the receiver and transmitter, but does not include the efficiency of the adapter (5V adapter efficiency is generally about 90%).
In fact, the charging speed is not directly related to the wireless charger and the wired charger. Wireless chargers can also charge fast, and wired chargers can also charge slowly.
The charging speed is determined by the charging current when the constant current charging is provided. It is generally determined by the specifications of the wireless charger. Some wireless chargers provide a large current, while some wireless chargers provide a small current.
We don’t have a quantitative indicator for the radiation level. We will find a professional structure test and compare a data analysis for everyone in the future.
Just give you a general idea. There must be radiation, but the radiation is not big, so don't worry. There are several reasons: first, the charging power of the mobile phone is only about 5W, which is low power; second, the distance is short, only within 25px, and the radiation to the surroundings is small; third, the transmitting and receiving ends have magnetic isolation plates, which are small to the surrounding radiation. ; Fourth, the working frequency is low, the working frequency is 110K~205KHz, and the radiation to the human body is small.
5. What is the composition of the wireless charger? 
The wireless charger is mainly composed of three parts: the main board, the coil and the shell. The main board directly determines the function and performance of the wireless charger, and is the core module of the wireless charger. The main board is mainly composed of a main control chip, a driving chip, a power device (MOS), a resistance capacitor, and a PCB board. The coil is generally a standard module, and related wireless charging standards strictly stipulate its structure and size parameters.
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