1890, physicist and electrical engineer nikola tesla did wireless transmission experiment. The international system of units of magnetic induction intensity is also named after him.
Tesla's wireless power transmission's idea is to use the earth as the inner conductor and the earth's ionosphere as the outer conductor, to establish a low-frequency vibration of about 8Hz between the earth and the ionosphere through a transmitter that amplifies the radial electromagnetic wave oscillation mode, and then use the surface electromagnetic waves around the earth to transmit energy.
Extended data:
Wireless charging function appeared on mobile phone devices as early as six or seven years ago. But only one or two mobile phones were installed at that time. After 20 15 Samsung launched S6, and 20 17 Apple iPhone 8 and iPhone X officially supported the wireless charging function, domestic brand models began to support this function one after another.
In 20 18, Xiaomi, OPPO, vivo and Huawei all released mobile phones supporting wireless charging, and all of them were mainly mid-to high-end models; Three iPhone launched last year also support wireless charging.
At present, most smartphones supporting wireless charging adopt Qi wireless charging standard technology. This technology uses electromagnetic induction technology to convert current into electromagnetism, and the mobile phone converts electromagnetism into current through the built-in coil for charging.
The industry believes that this is a relatively mature, safe and convenient technology. However, the disadvantage of this technology is that it will make the equipment hot, so users should be careful not to choose products that are too cheap and inferior when purchasing wireless chargers.
Users who have used wireless charging will find that the charging time of the former is slower than that of the traditional wired plug. This is also one of the shortcomings of wireless charging at present. Be patient if you need to recharge your mobile phone.
There are some devices on the market that support fast wireless charging. Simply put, the power is higher, reaching 75,000 power, but the price will be higher. The power of the ordinary price wireless charging board is generally 5 watts.
However, compared with wired charging, wireless charging is a bit slow, because many domestic models now support fast charging. For example, iQOO, which has just launched the market, uses a 44-watt fast charge. According to the official data of the manufacturer, it can complete 100% charging in about 46 minutes. If you use a wireless charger, even if the power is 7.5 watts, there is still a big gap in charging time.
Moreover, Qi wireless charging requires a distance, and the maximum charging distance is only 10 mm ... This is a bit "difficult" for Chinese mobile phone users who like to use mobile phone cases. Although it is not necessary to remove the mobile phone case, the thickness of the mobile phone case is required. Some charging plates indicate that the thickness of the protective shell cannot exceed 3 mm.
Baidu Encyclopedia-Wireless Charging Technology