Little A: “Who has a mobile phone charging cable?”
Little B: “I have a power bank, but I don’t have a Type-C charging cable…”
Little A: “……”
As we all know, although electronic products such as mobile phones and tablets have brought a lot of convenience to everyone’s lives, frequent charging problems are a headache. One charging line, one charging head; big and small, different. If you don’t take it when you go out, you are likely to fall into the awkward situation of “losing contact”.
As early as October 2017, the wireless charging mobile phone family ushered in 3 new members: iPhone 8, iPhone 8 Plus and iPhone X. With its strong influence, Apple has brought wireless charging technology into everyone’s field of vision. Wireless charging technology has an inherent advantage—convenience. It can avoid the phenomenon of “fire” when plugging in and unplugging the charging cable, and it does not damage the charging port, and it also makes mobile devices one of the earliest “users” of wireless charging technology.
However, why so long has passed, still many people choose to distrust “wireless charging technology” and insist on “love deeply and long-lasting” for charging cables that “cannot be cut and cannot be sorted out”? Here, the author wants to “rectify the name” of wireless charging technology and give you a clear and true original appearance of wireless charging technology.
From being invented to the present, the wireless charging technology, which has gone through 140 years, has silently “dipped into” our lives without knowing it: not only small electronic devices such as mobile phones, tablets, and smartwatches but also large devices such as electric cars. All have become members of the wireless charging family. So, let’s first understand how wireless charging is realized!
Three principles of wireless charging
1. Electromagnetic induction wireless charging-the transmission distance is too short
With the popularization of small electronic products such as mobile phones and the promotion of Texas Instruments, Philips, Samsung, Toshiba, and other companies, electromagnetic induction charging technology has become the most widely used wireless charging technology in small electronic products industry such as mobile phones.
As the name suggests, electromagnetic induction wireless charging technology uses the principle of electromagnetic induction. Correct! You heard it right, it’s the electromagnetic induction we learned in middle school.
This charging system is mainly composed of two coils: the primary coil and the secondary coil. First, the primary coil is energized with a certain frequency of the alternating current. Due to the effect of electromagnetic induction, a certain current will be generated in the secondary coil, so the energy is transferred from the transmitting end to the receiving end.
Applying this principle to a mobile phone, there is a primary coil in the charging base, and the mobile terminal has a built-in secondary coil. When the mobile phone is close to the charging base, based on electromagnetic induction, a certain current is generated in the mobile phone receiving coil, and the mobile phone can be charged without a charging cable.
However, electromagnetic induction wireless charging technology also has great shortcomings, one of the most troublesome is the limited transmission distance. At present, the effective charging distance of this technology is only 10mm, and if the positions of the two coils are not aligned, problems are likely to occur.
2. Magnetic resonance wireless charging-long transmission distance, high power supply efficiency, but need frequency modulation
On June 7, 2007, the MIT research team published their results in “Science”, stating that they “caught” electromagnetic waves successfully. They use a copper coil as an electromagnetic resonator. After the transmitter sends an electromagnetic wave of a specific frequency, it spreads through the electromagnetic field to the receiver and successfully powers a 60-watt light bulb two meters away.
Therefore, the use of this charging also requires two devices: an energy transmitting device and an energy receiving device. The condition for realizing energy transmission is that the two devices need to be adjusted to the same frequency. For example, two coils are used as resonators. The transmitting end vibrates at a frequency of 10MHz and emits an electromagnetic field to the surroundings, while the receiving end needs to vibrate at a frequency of 10MHz to realize energy transmission.
Magnetos are composed of large inductance coils made up of small capacitors in parallel or in series. Compared with electromagnetic induction, magnetic resonance wireless charging has a longer transmission distance, higher power supply efficiency, and supports a one-to-many power supply. But the biggest difficulty lies in: how to make two circuits get the same frequency, frequency modulation is the most core step in this technology.
3. Radio wave transmission-the transmission distance can reach 10 meters, but the efficiency is low
The principle of transmitting electricity through radio waves is: the electromagnetic waves are converted into electric current, and then the electric current is transmitted through the circuit.
The radio wave power transmission system is mainly composed of a microwave transmitting device and a microwave receiving device. The microwave transmitting device emits radio waves, and the microwave receiving device captures the energy of the radio waves and makes adjustments with the load to obtain a stable direct current.
In theory, the transmission distance of this wireless charging method is farther than that of electromagnetic induction and magnetic resonance, which can reach more than 10 meters; and it can also be automatically charged anytime and anywhere. However, this method also has a big disadvantage, that is, relatively low transmission efficiency.
It’s 2021, why hasn’t wireless charging technology been popularized yet?
Although wireless charging technology for mobile phones was proposed a long time ago, it is puzzling: After so many years, this technology is still advancing slowly. Why?
Reason 1: Charging distance limitation
Ordinary mobile phone chargers need to have a charging cable and a suitable charging head or power bank; while wireless charging has been developed for so many years, it has only achieved wireless charging within a distance of tens of millimeters, which means that when we go out Still need to bring a power bank or charging head.
Reason 2: It is difficult to have both the stability and high efficiency of wireless charging
Taking Apple’s 5W wireless charger as an example, taking into account the transmission efficiency, it takes about 3 hours to fully charge the iPhone X; charging with a 7.5W wireless charger also takes nearly 2.5 hours. Although 20W wireless chargers and wireless power banks have appeared on the market in 2019, their stability and charging efficiency are still major issues that linger in the minds of consumers.
Reason 3: The impact of wireless charging on battery life
Although wireless charging technology has been developed for many years, the mobile phone sector currently has the largest market share. Therefore, we have to consider: Will wireless charging shorten the service life of mobile phone batteries?
For the method of extending battery life, refer to the method of Apple’s official website:
The iPhone’s battery is designed to retain up to 80% of the original battery capacity after 500 full charge cycles. The full charge cycle means that after 100% of the power is used up, the charge will be counted once, not every time the charge is plugged in. Suppose you use half of the battery (50%) today, plug in the charging cable, and use half of the battery (50%) the next day, and then fully charge it again. At this time, the number of charging cycles will only be counted as 1 (50%). +50%) instead of plugging in and charging twice.
Recently, the editor of foreign media ZDNet has also wondered because the battery power storage capacity of his iPhone 8 Plus has dropped too fast: Will wireless charging affect the battery life of mobile phones? Therefore, by recording the battery power and the number of charging cycles of the iPhone 8 Plus, he proved that “wireless charging does have an impact on the battery life of the phone, and the battery aging speed will even accelerate by 50%”.
This curiosity editor analyzed the reasons for the decline in battery life and found out: maybe it is because, in wireless charging mode, the phone is still powered by battery for consumption; while in non-wired charging mode, the phone is externally charged The line-powered mode is for the mobile phone to consume. Therefore, in the wireless charging mode, the full charge cycle of the mobile phone battery will be more.
Of course, there are also some people who deny the results of this experiment, thinking that the length of battery life is mainly a manufacturer’s problem and has nothing to do with wireless charging. The author believes that because the wireless charging method uses a wireless charging module, it will cause the internal consumption of the mobile phone to increase during charging. In addition, more heat will be generated compared to the wired charging mode, and heat accumulation will also lead to a reduction in the service life of the mobile phone device.
However, because of wireless charging, we are free from the trouble of miscellaneous charging cables. Wireless charging treasures can give your mobile phone “power” anytime, anywhere, so wireless charging can greatly facilitate our lives. Perhaps there are still some drawbacks in wireless charging of mobile phones at this stage, but we believe in the power of technology, which will allow us to efficiently charge mobile phones and computers anytime, anywhere in the near future.
Finally, in view of the current situation, the author gives a suggestion: The best way to charge a mobile phone is-line charging is the main and wireless is the auxiliary. However, for the question of “Whether wired charging is convenient and fast, or wireless charging better”, there is a special group that does not need to consider it, that is, the local tyrants. do not understand? Will local tyrants care about the speed of battery damage?