Wireless charging technology originates from radio energy transmission technology and can be divided into two ways: low-power wireless charging and high-power wireless charging. Electromagnetic induction is often used for low-power wireless charging, such as Qi mode for mobile phone charging, but induction mode is used for ZTE electric vehicle wireless charging. High power wireless charging often adopts resonance type (most electric vehicles are charged in this way). The power supply equipment (charger) transmits energy to the device that uses electricity. The device uses the received energy to charge the battery and at the same time for its own operation. Since the charger and the electric device transmit energy by magnetic field, and there is no wire connection between them, the charger and the electric device can be exposed without conductive contact. The alternating 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 solution adopts electromagnetic induction. In fact, the electromagnetic induction solution does not have much mystery in the technical realization. BYD, a local company in China, used electromagnetic induction technology as early as the patent for non-contact induction charger applied in December 2005. It consists of an energy transmitting device and an energy receiving device. When the two devices are adjusted to the same frequency, or resonate at a specific frequency, they can exchange energy with each other. It is a technology currently being studied. The research team led by marinsoljacic, a physics professor at the Massachusetts Institute of Technology (MIT), used this technology to light a 60 watt bulb two meters away and named it WiTricity. The coil diameter used in this experiment reaches 1250px, which cannot be commercialized. If the coil size is to be reduced, the received power will naturally decrease.
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