The research on the principles of wireless charging technology can be traced back to the 1830s. Scientist Michael Faraday first discovered the principle of electromagnetic induction, that is, changes in the surrounding magnetic field will generate current in wires. By the 1890s, Nikola Tesla, an assistant on Edison's spectroscopic radiant energy research project and later a scientist, demonstrated the possibility of transmitting radio waves wirelessly and filed for the first patent. Currently, there are four different commercial technologies for wireless charging, including electromagnetic induction technology, radio wave technology, electromagnetic vibration technology, and electric field coupling technology. Each of these technologies has its own characteristics. Wireless charging refers to a device that uses the principle of electromagnetic wave induction to charge. The principle is similar to a transformer. There is a coil at each of the sending and receiving ends. The sending end coil is connected to a wired power supply to generate an electromagnetic signal. The receiving end coil senses the electromagnetic signal at the sending end and generates current to charge the battery. There are four main ways to realize wireless charging technology: electromagnetic induction, magnetic field vibration, radio wave, and electric field coupling.
Electromagnetic induction charging: AC current of a certain frequency in the primary coil generates a certain current in the secondary coil through electromagnetic induction, thereby transferring energy from the transmission end to the receiving end. At present, the most common charging pad solution uses electromagnetic induction. In fact, there is not much mystery in the technical implementation of electromagnetic induction solutions. China's local BYD Company applied for a non-contact induction type as early as December 2005. The patented charger uses electromagnetic induction technology. Magnetic field vibration charging: It consists of an energy sending device and an energy receiving device. When the two devices are adjusted to the same frequency, or vibrate at a specific frequency, they can exchange each other's energy, which is currently the One technology being studied, a research team led by MIT physics professor Marin Soljacic, used the technology to light up a 60-watt light bulb two meters away and named it WiTricity. The diameter of the coil used in this experiment reaches 50cm, which cannot be commercialized yet. If the size of the coil is reduced, the received power will naturally decrease. Compared with electromagnetic induction, the transmission distance can be extended by using vibration. The magnetic vibration method is different from the electromagnetic induction method, and there is no need to completely match the positions of the coils.