Wireless power transmission can be divided into short-range, medium-range and long-range transmission
Wireless charging technology is derived from wireless power transmission technology. Wireless power transmission, also known as wireless energy transmission or radio energy transmission, mainly realizes non-contact power transmission by means of electromagnetic induction, electromagnetic resonance, radio frequency, microwave, laser and so on. According to the different power supply distance of wireless power transmission in space, the forms of wireless power transmission can be divided into three categories: short-range, medium-range and long-range transmission.
(1) Short range transmission. It is realized by electromagnetic induction power transmission (ICPT) technology, which is generally suitable for power supply of small portable electronic equipment. ICPT mainly takes the magnetic field as the medium, uses the separable transformer coupling, and generates current through the primary and secondary coils. The electromagnetic field can penetrate all non-metallic objects, and the electric energy can be transmitted across many non-metallic materials, so as to transfer the energy from the transmission end to the receiving end, so as to realize the electric energy transmission without electrical connection. The transmission power of electromagnetic induction is large, up to several hundred kilowatts, but the application of electromagnetic induction principle is limited by the too short distance between the power supply end and the power receiving end, and the upper limit of transmission distance is about 10 cm.
(2) Medium range transmission. Through electromagnetic coupling resonance power transmission (ERPT) technology or radio frequency power transmission (rfpt) technology, medium-range transmission can provide wireless power transmission for mobile phones, MP3 and other instruments. ERPT technology mainly uses the working principle of electromagnetic resonance and strong electromagnetic coupling when the natural frequency of receiving antenna is consistent with the electromagnetic frequency of transmitting field, and realizes the efficient transmission of electric energy through non radiating magnetic field. Compared with the electromagnetic induction type, the magnetic field adopted by the electromagnetic resonance type is much weaker, the transmission power can reach several thousand watts, and the transmission distance can reach 3-4 M. Rfpt mainly transmits RF signal through power amplifier, and obtains DC power for load after detection and high-frequency rectification. Rfpt has a long distance, up to 10 m, but the transmission power is very small, ranging from a few milliwatts to 100 milliwatts.
(3) Remote transmission. It is realized by microwave power transmission (MPT) technology or laser power transmission (LPT) technology. Long distance transmission has important strategic significance for the field of space science and technology, such as energy transmission between man-made satellites and spacecraft and the development and utilization of new energy. MPT is to convert electric energy into microwave, transmit the microwave to the target position through free space, and then convert it into DC electric energy through rectification and provide it to the load. Microwave power transmission is suitable for large-scale, long-distance power transmission that is not easily affected by the environment, such as space solar power station. LPT uses laser to carry a large amount of energy and realize long-distance electric energy transmission with small emission power. The laser has strong directivity and concentrated energy, so there is no risk of interfering with the communication satellite, but the obstacles will affect the energy exchange between the laser and the receiving device, and the beam energy will be partially lost during transmission.