Wireless charging technology standards war

Qi and A4WP are the two most important wireless charging technologies today, but what are their respective advantages and disadvantages? Who will stand out in the upcoming wireless charging technology war? Let's take a look at the analysis brought by foreign technology media Android Authority.

　　There is no doubt that wireless charging will be a development direction for future mobile devices, and it is also one of the hot technologies that major manufacturers are competing to research. In fact, with the popularity of electronic products today, I believe that each of us has several different types of chargers and charging cables on hand, which is very inconvenient to use. Wireless charging technology is created to solve this problem. On the one hand, wireless charging technology can free users from the trouble of cables, and on the other hand, it can also solve the universality problem of chargers.

　　However, as we can see, wireless charging technology has not been widely used. The main reason is that there are many different wireless charging technologies, and among them, Qi and A4WP are undoubtedly the two closest to large-scale application. Qi is a technology proposed by WPC (Wireless Power Consortium), and A4WP, which was officially finalized in January this year, is its strongest competitor. The competition between Qi and A4WP can also be seen as a global battle for wireless charging technology.

　　Compared to A4WP, WPC, the organization that formulates Qi, is currently the world's largest wireless charging standard organization, with 137 partners from 15 different countries as members, and more than 100 devices equipped with Qi technology have been launched. But at the same time, some important members including Qualcomm, Samsung and Texas Instruments are also supporters of A4WP. Samsung has previously stated that A4WP has more potential than Qi.
 

　　In order to better understand the advantages and disadvantages of these two wireless charging technologies, let us first briefly understand the principles of wireless charging and the differences between these two technologies.

　　How wireless charging works

　　No matter how different the different wireless charging technologies are, the principle behind them is the electromagnetic induction phenomenon we are familiar with. Specifically, it uses a changing electric field to generate a changing magnetic field, and then uses a changing magnetic field to generate an electric field, thereby generating current to charge the device.

　　We all know that the direction of the magnetic field generated around a current-carrying wire is perpendicular to the direction of the current, and it is usually very weak. However, if the wire is wound into a circle or a spiral, the magnetic fields in the same direction will be superimposed, thus forming a stronger magnetic field. In fact, the principle of wireless charging is similar to the common transformers in our lives, which use the current in one coil to generate current in another coil. However, unlike the way transformers conduct magnetic fields through iron cores, the induction coils in wireless charging devices have undergone some special adjustments and use air as the medium to conduct magnetic fields, thereby generating induced currents. At the same time, like the resonance of sound, the two coil inductions also need to set a resonant frequency so that the frequencies of the receiving coil and the output coil are consistent, so that a sufficiently strong induced current can be generated in the receiving coil even when the current in the output coil is very small.

　　For example, everyone must have heard the story of a group of soldiers marching on a bridge and eventually causing it to collapse. This is because the frequency of the soldiers' steps is consistent with the natural frequency of the bridge, so that energy can be transmitted to the bridge to the greatest extent, eventually leading to the collapse of the bridge. For wireless charging technology, the output coil is equivalent to the soldier, the energy output side; and the receiving coil is equivalent to the bridge, the energy receiver. If you want to maximize the efficiency of energy transmission, you must make the frequencies of the two coils consistent.

　　Practical Application of Principles

　　The principle is the principle after all, but how do the major manufacturers achieve this principle? In fact, it is very simple. It only requires an output coil that generates a magnetic field through alternating current and a receiving coil that generates current through the magnetic field. At the same time, the current in the output coil needs to be adjusted to a certain frequency using an LC circuit (composed of capacitors and inductors) so that the largest possible current can be generated in the receiving coil to ensure high energy transmission efficiency.

　　In addition, designers need to solve many practical problems such as how to manufacture the induction coil, how to determine the transmission frequency, how to optimize the charging time and energy consumption, but these problems are not discussed in this article. However, there is a very important issue, which is how to determine the size of the induction coil and how to find a balance between transmission efficiency, magnetic field strength and resonant frequency. In this regard, Qi and A4WP have different choices, which ultimately leads to Qi technology being small and efficient, while A4WP technology is powerful.

　　Qi wireless charging technology - magnetic induction charging

　　Qi wireless charging technology has been widely used. Nokia Lumia 920, Samsung Galaxy S4 and Google Nexus 4 all support this technology. Compared with A4WP, Qi uses a smaller induction coil, which can easily transmit energy at a higher frequency. However, its disadvantage is also obvious, that is, the charging distance is relatively short, only a few centimeters at most. Therefore, wireless charging devices using Qi need to place mobile phones and other devices on the charging base, which usually has a magnetic fixing device. Another major disadvantage of Qi is that it does not support charging multiple devices at the same time.

　　In order to improve these shortcomings, some people have proposed placing multiple sets of small coils in the charging output device to increase the charging range, but power consumption will undoubtedly increase, and users still need to place mobile phones and other devices precisely in the area with the induced magnetic field when charging to maintain a strong connection with the charging base. In order to further solve the problem of increased power consumption, WPC has added a communication protocol to Qi technology. Through this protocol, the charging device will "tell" the charging base the required power or that charging is complete, and the charging base can adjust the output power according to the needs of the charging device or switch to energy-saving mode after charging is completed.

　　In addition, another criticized issue of Qi is that it may heat the conductive materials inside devices such as mobile phones when charging, causing heat.

　　In general, Qi is a relatively conservative wireless charging technology. Although its energy transmission efficiency is high, it is not flexible enough in actual use and has high requirements for users.

Wireless charging technology A4WP——Magnetic resonance charging#e#

　　A4WP wireless charging technology——magnetic resonance charging

　　When it comes to improving energy transmission efficiency, A4WP's solution is completely different from Qi. Compared to Qi, A4WP uses a larger output coil and can charge multiple devices at the same time. At the same time, due to the precise resonant frequency, even a weak induced magnetic field can charge the device, which means that the charging range of A4WP will be much larger than Qi. However, the principle of the magnetic resonance wireless charging technology used by A4WP is the same as Qi, which is essentially electromagnetic induction, but the way electromagnetic induction is used is different.

　　Although the principle is the same, the effect of using A4WP is completely different from Qi. A4WP has a larger charging range. In theory, it can be charged through objects, and it does not need to be placed accurately on the charging base. Previously, a New Zealand company called Power by Proxi launched a wireless charging box that can automatically charge batteries, mobile phones, cameras, etc. by placing them in the box. Although this wireless charging box does not adopt the A4WP standard, the principle is the same.

　　Like Qi, A4WP can also automatically adjust the energy distribution plan according to the number of charging devices and power shortage conditions to achieve energy saving.

　　Judging from its features, A4WP is much more convenient than Qi. Users no longer need to place their phones carefully like when using Qi wireless charging devices. And because A4WP has a larger charging range, it will support some devices with complex shapes, such as cameras.

　　The disadvantage of A4WP may be that its power cannot meet the requirements when charging multiple devices. For example, when a 10W A4WP wireless charger charges three 5W charging devices, the charging power of each device will be insufficient and the charging time will be longer. So the real problem for A4WP is its charging speed and efficiency.

　　Qi vs A4WP: Who will win?

　　Because there are no devices using A4WP technology on the market yet, it is still unknown which technology is better in terms of charging efficiency and power consumption. However, we can imagine the actual application of the two technologies. For home users, device compatibility and efficiency are the two factors they care about most. From this perspective, the difference between the two is not big, but A4WP has a slight advantage. For public places such as cafes, the A4WP wireless charger that can charge multiple devices at the same time is obviously more practical.

　　However, the factor that is most likely to determine who will win is the application rate of the two technologies. In this regard, Qi, which has many partners and more than 100 devices on the market, is far ahead. However, important partners such as Qualcomm, Samsung, and Texas Instruments have also shown great interest in A4WP. A Samsung spokesperson once said that Samsung is optimistic about A4WP technology and is willing to build a corresponding ecosystem for A4WP. The participation of these mobile device industry giants will undoubtedly accelerate the popularization of A4WP.

　　Like all new technologies, it will take some time for the market to accept A4WP. Although Samsung is optimistic about A4WP, its latest flagship model Galaxy S4 still uses Qi wireless charging technology. Perhaps Samsung will support A4WP devices next year. It can be seen that A4WP still needs some time to finally perfect the technology and become well-known. Therefore, Qi should continue to sit firmly at the top of wireless charging technology for some time to come.

　　Although A4WP has various advantages, if A4WP and Qi eventually form a two-way competition, the incompatibility between the two will bring inconvenience to users. However, we still hope that devices using A4WP can be available soon.