Wireless charging technology originates from wireless energy transmission technology. Low-power wireless charging often uses electromagnetic induction (such as the charging method of the mobile phone, but ZTE's inductive type of wireless charging using electric vehicles). High-power wireless charging often uses resonance. The type (most electric cars use this method) is the power supply device (charger) to transfer energy to the power device, which uses the received energy to charge the battery, and at the same time for its own use. Since the energy is transferred between the charger and the power device in a magnetic field, there is no wire connection between the charger and the power device, so that the charger and the power device can be exposed without any conductive contacts.