With the improvement of people's life convenience and the rapid advancement of technology, wireless charging technology is becoming more and more popular among people. Especially with the vigorous promotion and use of new energy vehicles, the convenience and timeliness of charging has become more and more obvious. How to overcome these problems has become a high wall in front of wireless charging technology and an important step in realizing green energy and sustainable development.
Wireless charging technology can be divided into low-power wireless charging and high-power wireless charging. Low-power wireless charging often uses electromagnetic induction, such as mobile phone charging. High-power wireless charging often uses resonance, such as charging electric vehicles. Currently, there are four main ways to realize wireless power transmission:
Magnetic field induction
A certain frequency of alternating current is passed in the primary coil, and a certain current is generated in the secondary coil through electromagnetic induction, thereby transferring energy from the transmitting end to the receiving end. This principle is similar to the principle of transformers commonly used in power systems. Alternating current is applied to the primary side (primary coil) of the transformer, and the secondary side (secondary coil) will induce electromotive force due to the principle of electromagnetic induction. If the secondary circuit is connected, that is Induced current can occur, so that wireless transmission of electrical energy from the transmitter coil to the receiver coil can be achieved. At present, the way of using this method to transfer electric energy has been widely used in the low-power, short-distance wireless charging market, such as electric toothbrushes, mobile phones, cameras and other small portable electronic devices, which are generally wirelessly charged by the charging base. The power transmitting coil is installed in the charging base, and the receiving coil is installed in the electronic device.
Resonance
This kind of wireless power transmission method is similar to the principle of wireless communication. The electromagnetic wave of the resonant circuit at the transmitting end diffuses openly throughout the entire space, and the circuit at the receiving end resonates at the specific frequency, thereby realizing energy transfer. This kind of power transmission method can get higher transmission efficiency when the output power of the receiving end is relatively small. However, there are problems such as electromagnetic radiation, the greater the transmission power, the longer the distance, the lower the efficiency, and the more serious the radiation.
Magnetic coupling resonance
This method can be regarded as an enhanced version of resonance, which requires two resonance systems for transmitting and receiving, which can be made of induction coils respectively. By adjusting the transmitting frequency to make the transmitting end vibrate at a certain frequency, what it produces is not an ordinary electromagnetic wave that diffuses everywhere, but a non-radiative magnetic field. That is, the electric energy is converted into a magnetic field, and an energy channel is formed between the two coils. The natural frequency of the receiving end is the same as the frequency of the transmitting end, so resonance occurs. With each resonance, more voltage will be generated in the sensor at the receiving end. After generating multiple resonances, the surface of the inductor will gather enough energy, so that the receiving end receives energy in this non-radiative magnetic field, thus completing the conversion of magnetic energy to electrical energy and realizing wireless transmission of electrical energy. The range of this non-radiative electromagnetic field is relatively limited, and it is not suitable for long distances. The transmitter and receiver are required to be within 8 times the radius of the induction coil.
Radio wave
Electromagnetic waves can be used to transmit information. In theory, as long as the frequency is high enough, energy can also be transmitted. An electromagnetic wave generator is installed at the power source, and the energy is transmitted to the receiving antenna through the transmitting antenna, and then the electromagnetic wave signal is converted into electrical energy for the equipment to use. However, this kind of power transmission method also has obvious weaknesses, such as large interference from electromagnetic waves, low transmission efficiency, and radiation to the human body.
