Physicists have long known that energy can be effectively transmitted between two objects with the same resonance frequency, while the interaction between objects with different frequencies is more

Weak. This is why singers can shatter one bottle with different water content without affecting other bottles. It's just like when we swing, just sitting on it and letting our drooping legs swing synchronously can give the swing power. Wireless charging technology makes use of this principle. Similarly, the wireless charging technology also applies the electromagnetic wave induction principle and related AC induction technology. At the sending and receiving end, the corresponding coil is used to send and receive the induced AC signal to charge. Users only need to place the charging equipment on a "flat plate" to charge. Such charging method has appeared in watches and shavings in the past. At that time, however, it was unable to effectively charge large capacity lithium-ion batteries. The technical principle of wireless charger is as shown in the figure

Originally, a British company invented a new type of wireless charger, which looks like a plastic mouse pad. The "mouse pad" is equipped with a dense array of small coils, so it can generate a magnetic field and transmit energy to the electronic equipment equipped with special receiving coils for charging. The receiving coil is magnetic.

The alloy coil is made of wires, similar in size and shape to gum, so it can be easily attached to electronic equipment. The mobile phone can be charged by putting it on the pad, and can charge multiple devices at the same time. Charging technology has appeared before, but the new invention is more convenient and practical. As long as the receiving coil is pasted on the mobile phone and other devices, it can be charged at any position on the "mouse pad", unlike some previous technologies, which need precise positioning. Several devices are placed on mats at the same time, which can be charged at the same time. The magnetic field generated by the charger is very weak, which can charge the equipment but will not affect the nearby credit card, video tape and other items that use magnetic recording data.

The wireless charging system mainly adopts the principle of electromagnetic induction, and realizes the energy transfer through the coil energy coupling. As shown in the figure, when the system is working, the input terminal converts the AC mains power into DC power through the full bridge rectifier circuit, or uses the 24V DC terminal to directly supply power to the system.

After the power management module, the output DC is converted into high frequency AC through 2m active crystal oscillator inverter to supply the primary winding. Through the coupling energy of two inductors, the output current of the secondary coil is changed into direct current to charge the battery.

The changing magnetic field will produce the changing electric field, and the changing electric field will produce the changing magnetic field. Its size is related to their change rate. The change rate of sine function is another sine function, so the electromagnetic wave can spread out, and the generation of induced voltage is related to the change of magnetic flux, so the changing magnetic field inside the coil will produce the induced voltage, so as to complete charging. Process.

Mobile phone wireless charging is a relatively new charging method, its principle is actually very simple, which is to separate the primary and secondary level of common transformer to achieve wireless purpose. Of course, the working frequency of wireless charging is relatively high, and even the role of energy transfer can be achieved by discarding the direct coil of the core.