Wireless power transmission is used for battery charging of mobile devices, but equally for that of electric vehicles.
As for mobile devices, methods based on magnetic induction( MI), magnetic resonance( MR) and radio frequency transmission are used for power transmission. Wireless charging technology for electric vehicles relies on magnetic resonance because this technology can transfer a relatively large amount of energy.
In all methods, the energy transfer is between the stationary PTU unit, which generates the energy, and the PRU unit. In mobile device charging techniques, the PTU unit is located in the charging mat; in electric vehicle charging, it is located in the garage floor. The PRU unit is the energy receiving unit. It is located in the mobile device or in the floor of the electric vehicle. In magnetic resonance, the PRU unit consists of the resonant circuit, the downstream rectifier that rectifies the high-frequency energy signal, and a DC/DC converter to raise the DC voltage to the correct value.
In mobile devices, the PRU units are divided into several classes in terms of power, for powers between 3.5 W and 50 W.