Wireless charging, say goodbye to the "wired" life!

Wireless charging form

There are three types of wireless charging, namely electromagnetic induction, magnetic field resonance and radio wave. The most common wireless charging method is electromagnetic induction represented by Qi wireless charging. If there is a Qi logo on an electronic product, it means that it can be charged wirelessly. The magnetic charging of the second generation of Apple Pencel and the reverse charging of Huawei Matepad Pro all use Qi wireless charging technology.

Let me tell you a secret: China's BYD company applied for a patent for a contactless inductive charger using electromagnetic induction technology as early as December 2005.

How much do you know about charging principles ?

Electromagnetic induction

Due to the magnetic effect of electric current, a magnetic field is generated around the current-carrying wire. If the wire is wound into a spiral coil as shown in the figure, the direction of the magnetic field will change from surrounding the wire to radially passing through the wire. Such spiral coils are placed in the charging base and the electrical appliance. The alternating current generates a changing magnetic field through the power transmission coil of the charging base. When the electrical appliance is placed on the charging base, the changing magnetic field passes through the power receiving coil in the electrical appliance, thereby generating current, transferring energy from the transmitting end to the receiving end, and the battery begins to charge.

Magnetic field resonance

The energy transmitter and receiver of the resonator are composed of a small capacitor connected in parallel or in series with a large inductor coil. When the two are adjusted to the same frequency, magnetic resonance will occur [1], and energy will be exchanged between them. This is a technology currently under research. The research team led by Marin Soljacic, a physics professor at the Massachusetts Institute of Technology (MIT), used this technology to light up a 60-watt light bulb two meters away and named it WiTricity. However, the diameter of the coil used in the experiment reached 50 cm. If the coil size is reduced, the receiving power will decrease, so it has not yet been commercialized.

Radio wave

The principle is to convert ambient electromagnetic waves into electric current and transmit the electric current through the circuit.

This wireless charging method has a transmission distance of more than 10 meters, which is suitable for long-distance low-power charging, and can also realize automatic charging anytime and anywhere. However, due to the low conversion efficiency, if this method is used, the charging time will be relatively long.

Keep pace with the times:

The wireless charging innovation team of the Digital Institute of the Shenzhen Institute of Advanced Technology of the Chinese Academy of Sciences has also conducted research on the technical development and product customization of magnetic resonance wireless charging low-power application scenarios.

At present, the team has completed the research and development of key technologies and equipment for magnetic field resonance coupling and produced a prototype of a wireless charging system. Simply by bringing an object close to the magnetic resonance coil, "wireless charging" can be achieved.

Simulation diagram of multiple devices charging at the same time

Compared with electromagnetic induction, magnetic resonance wireless charging can achieve long-distance (ranging from a few centimeters to a few meters) and efficient (some transmission efficiency reaches more than 80%) power supply, and even one-to-many power supply.

Without further ado, let's summarize:

The way to charge a shared electric vehicle is to manually replace the battery. You can know the remaining power of any nearby vehicle and the remaining mileage on the APP interface. The difference between shared electric vehicles and shared bicycles is that they must be parked at a "fixed point". The parking place is fixed and planned. Most communities and shopping malls and supermarkets have parking spots.

The editor has something to say:
I never expected that the emerging shared electric vehicle industry would use manual battery replacement. If shared electric vehicles also use wireless charging or solar charging, we would no longer have to worry about the exposed charging port or running out of power on the way.

Image source: Pixabay

If wireless charging technology can be widely used, perhaps the power supply problems of medical devices implanted in the body such as pacemakers, sensors, defibrillators, etc. can be effectively solved.

Contributors: Southwest University Popular Science Space Station, Chongqing Physics Society, Beibei District Science and Technology Association

Audit expert: Zhang Qiaoming

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