In recent years, the development of mobile phones has been swiftly fast. Unless you use the king iPhone, you can easily obsolete the mobile phone you have just bought two months. For the mobile phones released by various domestic manufacturers this year, your ten hands are all Can’t count. However, even with rapid development, it seems to have reached a bottleneck period, which often gives people the feeling of old wine in a new pot. In addition to the pursuit of a screen-to-body ratio, another feature has become one of the “standard features” pursued by many flagship mobile phones. : Wireless charging.
In recent years, more and more smartphones have begun to be equipped with wireless charging functions, such as iPhone Xs, Samsung S9, Xiaomi MIX 3, Huawei MATE20, etc. Many friends are no strangers to this function. There are currently four main wireless charging methods: electromagnetic induction charging, magnetic resonance charging, radio wave charging, and electric field coupling. The technical solutions for various charging methods are also different.
Electromagnetic induction charging
Electromagnetic induction wireless charging is often used for low-power wireless charging, which can also be called non-contact induction charging, and is widely used for wireless connection induction charging. For example, the use of various wireless induction power supply products such as rechargeable flashlights, electric shavers, wireless connection induction wall lamps, and electric toothbrushes that have been talked about more recently are basically used for this kind of induction charging, which is convenient to achieve the waterproof function of the product. The charging efficiency is about 80% to 95%, there is no high-frequency radiation, it meets the safety certification of various countries, and the price is low.
Compared with the prior art, the inductive wireless charging technology has a simple structure and a lighter volume. The transmitting coil is set in the charging plug, and the rubber-plastic insulation layer is wrapped around it, so that the inductive charger and the external charging device are not directly connected. There is no electrical safety problem, and it is safer and more reliable to use. It can be easily waterproof when used on some daily equipment or products.
Magnetic field resonance charging
The rise of magnetic resonance technology originated from an experiment at MIT in 2008. Researchers lit up a 60W light bulb in the air, which made the world realize that wireless charging can still be used like this for the first time.
The advantage of magnetic field resonance is that it can achieve effective energy transfer in a larger range and achieve a higher degree of spatial freedom. Therefore, it is more reliable and supports the simultaneous charging of multiple devices. When the transmitting end encounters the receiving end with the same resonance frequency, the resonance effect is used for power transmission. This charging method has a long transmission distance and a large transmission power, which is suitable for long-distance high-power charging. However, this charging method has lower efficiency and greater loss during transmission. The longer the distance, the greater the transmission power and the greater the loss. More importantly, the frequency band used must be protected from external factors.
Radio wave charging
Radio wave charging is a relatively mature wireless charging technology. The wireless charger that uses radio wave charging consists of a microwave launching device and a microwave receiving device. It can capture the radio wave energy bounced back from the wall and adjust it with the load. While maintaining a stable DC voltage. This wireless charging method is more convenient. You only need to install a transmitter on the wall plug and a receiver on the low-voltage product.
The advantage is that the transmission speed is faster in the middle of the transmission interval, but the disadvantage is that the stability and safety are relatively low, and a certain cost is required to invest in research and development.
Electric field coupling charging
This method can be regarded as an enhanced version of the resonance type, 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, which converts electrical energy into a magnetic field, forming an energy channel 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, enough energy will be gathered on the surface of the inductor, 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.
An MIT laboratory demonstrated an experiment in 2008, lighting up a 60W bulb within two meters of space. They named the technology Witricity, and the project is still in the laboratory stage. Of course, the range of this non-radiation electromagnetic field is relatively limited, and it is not suitable for long distances. The transmitting end and the receiving end are required to be within 8 times the radius of the induction coil.
Electric field coupling charging is suitable for short-distance charging, and the conversion efficiency is also high, and the position can not be fixed, but the disadvantage is that it requires large-scale equipment and low power.
Therefore, among the four current wireless charging methods, the electromagnetic induction wireless charging scheme is the most mature and the most widely used in commercial applications. For example, the various wireless chargers that our mobile phones need to use this technical scheme. As far as the current level of technology is concerned, the electromagnetic induction wireless charging scheme is the most worthy of use. It also provides a solution for the charging method of smartphones, and the advantages still outweigh the disadvantages. And while improving the convenience of charging, it also unifies all kinds of chargers to some extent, reducing the waste of resources. In the future, wireless charging will become a trend.
