At present, there are four different commercial technologies for wireless charging: electromagnetic induction technology, radio wave technology, electromagnetic resonance technology, and electric field coupling technology. The technology mainly used in mobile phone wireless charging is electromagnetic induction technology and electromagnetic resonance technology. The mobile wireless charging standard at this stage has two main mobile wireless charging standards alliances, one is WPC and the other is Airfuel.
The Samsung Galaxy S8 is equipped with a folding wireless charger. With wireless charging, the Samsung Galaxy S8 can be fully charged. But the embarrassing fact is that wireless charging is still only a few manufacturers' insistence. However, while Samsung insisted, Apple also exposed the ambition of deploying wireless charging. The two giants coincided, and it is likely to fight again in this area that has not yet been valued. As far as the current status of the mobile phone industry is concerned, wireless charging has not been widely popular. The reason for the lack of fire is not because wireless charging is not necessary, but there are still many shortcomings in the technology at this stage.
Samsung's wireless charging solution has reached the front-end level of mobile wireless charging, but still needs a qualitative leap in technology. It is reported that the Samsung Galaxy S8 wireless charging supports both Qi and PMA protocols. There are still two shortcomings in these two protocols that have not yet been resolved - the transmission distance is short and the placement requirements are strict, which is also a technology that hinders wireless charging. threshold. Why the technical difficulties are difficult to overcome, we must first talk about the principle of wireless charging. Principle of wireless charging of mobile phones The principle of wireless charging is to use electromagnetic wave induction. The process is similar to that of transformers. There is one coil at the transmitting and receiving ends, the transmitting end coil is connected to the wired power supply to generate electromagnetic signals, and the receiving end coil senses the electromagnetic signal of the transmitting end to generate Current charges the battery.
The principle of wireless charging technology can be traced back to the 1930s. Scientist Michael Faraday first discovered the principle of electromagnetic induction, that is, changes in the surrounding magnetic field will cause current in the wire. In the 1890s, an assistant to the Edison Spectrum Radiation Energy Research Project, the great scientist Nikola Tesla confirmed the possibility of wirelessly transmitting radio waves.
Of course, wireless power supply has a broader prospect in the future of home appliances, as well as the development of electric vehicles with strong momentum. Once wireless charging breaks through technical barriers, while ensuring conversion, security, and ease of use, efficient and fast charging will bring further productivity to humans as described in the science fiction "Three-body." Here, we will talk about electromagnetic induction and electromagnetic resonance related to mobile phone charging.
1 electromagnetic induction charging
The primary coil has a certain frequency of alternating current, and a certain current is generated in the secondary coil by electromagnetic induction, thereby transferring energy from the transmitting end to the receiving end. At present, the most common mobile phone wireless charging solution uses electromagnetic induction. The charging stand and the terminal used for wireless charging of the mobile phone respectively have built-in coils, and the two begin to supply power from the charging stand to the terminal. In order to improve the power supply efficiency, it is necessary to align the positions between the coils without causing an offset.
At present, electromagnetic induction wireless charging has a higher conversion rate than magnetic field resonance charging, and the charging conversion rate can reach about 80%. At present, the technology is widely used in the field of mobile phone wireless charging. However, this type of wireless charging technology also has obvious drawbacks - short transmission distance and strict location requirements. The wireless charging mobile phones that are currently on the market require mobile phones to be in contact with the charging pad for wireless charging, and have extremely demanding requirements for placement. The wireless charging transmission distance in this way is difficult to improve, so the manufacturer has improved the situation where the placement position is demanding.
In August 2011, Japan's Oar Corporation, which is engaged in the smartphone peripheral business, launched a charging stand called “Wireless Charging Boardâ€. Built-in magnets can attract the terminal to the designated position; Panasonic's coil in the "contactless charging board" introduced in June 2011 has a drive that can move in the plane. By automatically detecting the position of the terminal and moving to the position, the positions of the coils are aligned, so that the terminal can be charged anywhere on the charging board; the wireless charger that Hitachi Maxell launched in April 2011 " AIR VOLTAGE" has 14 coils built in to increase the probability of positional alignment. But obviously such improvements require higher costs to support.
2 magnetic field resonance charging
The system consists of an energy transmitting device and an energy receiving device. When the two devices are adjusted to the same frequency or resonate at a specific frequency, they can exchange energy with each other. For example, two copper coils are used as resonators, the transmitting end vibrates at a frequency of 10 MHz, and an electromagnetic field is radiated around the receiving end, and the receiving end needs to vibrate at the same frequency of 10 MHz to receive the transmitted energy. On June 7, 007, the research team at the Massachusetts Institute of Technology published their research on the website of Science. The research team applied resonance to the transmission of electromagnetic waves to successfully "catch" the electromagnetic waves. They use copper coils as electromagnetic resonators, with one coil attached to the transmitting power and the other receiving the power. The technology, which they call "wireless power", has been successfully tested for a 60-watt bulb that is two meters away. At present, the farthest transmission distance of this technology can only reach 2.7 meters. If you want to reduce the size of the coil, the receiving power will naturally drop. Compared with the electromagnetic induction method, the magnetic field resonance can be used to extend the transmission distance. Another advantage of the magnetic field resonance method different from the electromagnetic induction method is that it can achieve more efficient power supply without completely matching the positions between the coils.
Since the magnetic field resonant charging can be free from the strict limitation of the position and can realize one-to-many charging, this method will become the development direction of wireless power supply for mobile phones and even electric vehicles and home appliances in the future. However, the technical barrier that needs to be solved at present is that the conversion rate is low and cannot solve this problem. If you want to make this method widely popular, it will be as described in the "Three-body": "Even two centuries ago, this is also a The very common technology, which was not commonly used at the time, was because the power supply was too much loss, and only a small part of the power that was transmitted into the space was received, and most of it was lost. In this era, Due to the maturity of controlled nuclear fusion technology, energy has been greatly enriched, and the losses caused by wireless power supply have become acceptable."
Another problem that needs to be solved is electromagnetic radiation. Of course, there is no need to worry about charging the mobile phone with such low-power electromagnetic radiation. However, in order to meet the high power requirements such as electric vehicle charging, the transmitting end must increase the voltage and frequency to generate high-power electromagnetic waves. It is a consensus of the scientific community to suffer from the magnetic field radiation of the power line for a long time. The damage of the high-power magnetic field to the body is more serious, and it will cause interference to the electrical appliances. Therefore, in order to promote high-power wireless charging, it is necessary to change or circumvent these radiations.
On December 17, 2008, several companies including Philips Electronics, Texas Instruments, and National Semiconductor formed a wireless charging alliance WPC to jointly develop a wireless charging standard Qi to improve compatibility of different products. Qi is by far the most widely distributed and most popular wireless charging standard in the world. Because the unified wireless charging standard is adopted, as long as it is a Qi protocol, the wireless charging function of products from different manufacturers can also be used. Qi wireless charging standard uses electromagnetic induction technology, so the biggest problem of this wireless charging standard is the one just mentioned. The technical implementation requires the user to align the terminal with the wireless charging base, and the transmitting end and the receiving end can be precisely aligned. Charging, and the transmission distance limit is more stringent. The PMA wireless charging standard was initiated by Duracell Powermat, which is a joint venture between P&G and wireless charging technology company Powermat, with a relatively comprehensive strength. The driving force for PMA is to pull the strategy of manufacturing consumer demand through enterprise support. Starbucks supports this charging technology in chain stores as an example.
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