Wireless charging: just one charge, no extra action required

Wireless charging is gradually becoming a part of daily electronic device charging, from electric toothbrushes to smart bracelets and mobile phones, the application scenarios of wireless charging are increasing day by day. It not only simplifies the charging process, but also frees us from the constraints of charging cables. What is the principle of charging with just one sticker?

Wireless charging, also known as induction charging or wireless energy transfer, is actually a technology that can charge devices without connecting charging cables between electronic devices and charging platforms.

The wireless charging application of electronic devices is mainly based on the principle of electromagnetic induction, which means that in a closed circuit, when the magnetic flux passing through the circuit changes, induced current will be generated in the circuit.

The implementation of wireless charging usually requires two coils, one is the transmitting coil placed in the charging platform, and the other is the receiving coil placed inside the electronic device. When a changing current passes through the transmitting coil of the charging platform, a changing magnetic field is generated inside the coil. After the electronic device approaches the charging platform, the receiving coil will generate induced current, which will be converted into direct current through the circuit system to charge the device.

Although wireless charging can replenish power without the need for a power cord, the transmitting and receiving ends need to meet the requirements of location and distance. The transmission distance of electromagnetic induction is usually between a few millimeters and a few centimeters, and it is also affected by the alignment of the coil. So when performing wireless charging, the closer and more aligned the coils are, the faster the charging speed.

In 2007, a research team from the Massachusetts Institute of Technology published a study in the journal Science, which showed that under the strong coupling state of a self resonant coil, a copper coil with a diameter of 25 centimeters can achieve energy transmission of over 2 meters, with a transmission power of 60 watts, enough to light a light bulb.

Some people may think that "sticking a sticker" for charging is not very convenient. Can it be charged without sticking it?

[Long distance wireless charging]

Electromagnetic resonance is another principle of wireless charging applications that allows for energy transfer over longer distances. Electromagnetic resonance also requires two sets of coils. The transmitting end generates a changing magnetic field through an oscillator and a transmitting coil. Since the receiving coil and the transmitting coil at the receiving end have the same resonant frequency, strong coupling occurs between them, converting the magnetic field energy into electrical energy and achieving wireless transmission of electrical energy.