Wireless charging methods include electromagnetic induction, magnetic resonance, electric field coupling, and radio wave transmission. Most of the wireless charging of mobile phones uses the principle of electromagnetic induction. Electromagnetic induction wireless charging, such as the wireless charging of mobile phones, when the power current passes through the coil (the transmitting coil of the wireless charger), a magnetic field will be generated, and other unpowered coils (the receiving coil of the mobile phone) will generate current when close to the magnetic field. To charge the phone.
What are the types of wireless charging
▼Magnetic field induction
Give the primary coil a certain frequency of the alternating current, and generate a certain current in the secondary coil through electromagnetic induction, thereby transferring energy from the transmitting end to the receiving end. This principle is similar to the principle of transformers commonly used in power systems. Alternating current is applied to the primary side (primary coil) of the transformer, and the secondary side (secondary coil) will induce electromotive force due to the principle of electromagnetic induction. If the secondary side circuit is connected, that is Inductive current can occur, so that wireless transmission of electrical energy from the transmitter coil to the receiver coil can be achieved.
This kind of wireless power transmission method is similar to the principle of wireless communication. The electromagnetic wave of the resonant circuit at the transmitting end diffuses openly throughout the entire space, and the circuit at the receiving end resonates at the specific frequency to realize energy transfer. This kind of transmission method can get higher transmission efficiency when the output power of the receiving end is relatively small. But there is electromagnetic radiation. The greater the transmission power, the farther the distance and the lower the efficiency, the more serious the radiation.
▼Magnetic coupling resonance
This method can be regarded as an enhanced version of the resonance type. It requires two resonance systems for transmitting and receiving, which can be made of induction coils. By adjusting the transmitting frequency to make the transmitting end vibrate at a certain frequency, what it produces is not ordinary electromagnetic waves that diffuse everywhere, but a non-radiative magnetic field, which converts electric energy into a magnetic field, forming an energy channel between two coils . The natural frequency of the receiving end is the same as the frequency of the transmitting end, so resonance occurs. With each resonance, more voltage will be generated in the receiver sensor. After multiple resonances are generated, enough energy will be gathered on the surface of the inductor, so that the receiving end receives energy in this non-radiative magnetic field, thus completing the conversion of magnetic energy to electrical energy and realizing wireless transmission of electrical energy.
We all know that electromagnetic waves can be used to transmit information. In theory, as long as the frequency is high enough, energy can also be transmitted. This wireless charging method may be the closest to what people think of wireless charging. An electromagnetic wave generator is installed at the power source, and then the energy is transmitted to the receiving antenna through the transmitting antenna, and then the electromagnetic wave signal is converted into electrical energy for use by the device. However, this kind of power transmission method also has obvious weaknesses, such as large interference from electromagnetic waves, low transmission efficiency, and radiation to the human body.
Wireless charging used in mobile phones
Qi standard is the world’s first standardization organization to promote wireless charging technology-the “wireless charging” standard launched by the Wireless Charging Alliance, with two major characteristics of convenience and versatility. First of all, products of different brands can be charged with Qi wireless chargers as long as they have a Qi logo. Secondly, it overcomes the technical bottleneck of wireless charging “university”. In the near future, mobile phones, cameras, computers, and other products can be charged with Qi wireless chargers, providing the possibility for large-scale applications of wireless charging. The icon “Qi” is the pinyin (Qi) of “qi” in Chinese, which means “representing “vital energy” in Asian philosophy-an invisible energy.
Qi transmits electricity based on the principle of electromagnetic induction. The basic principle of inductively coupled power transmission system. This system consists of the transmitter coil L1 and the receiver coil L2, and the two coils together form an electromagnetic coupling inductor. The alternating current carried by the transmitter coil generates a magnetic field and induces the receiver coil to generate a voltage. This voltage can be used to power mobile devices or charge batteries.
The advantages and disadvantages of wireless charging
▼Advantages of wireless charging
Safety: No energized contact design can avoid the risk of electric shock.
Durable: The power transmission components are not exposed, so they will not be corroded by moisture, oxygen, etc. in the air; there are no contacts, so there will be no loss caused by mechanical wear and flashover during connection and separation.
Convenience: There is no need to connect with wires when charging, just put it near the charger, no need to occupy multiple power sockets, and there is no trouble of entanglement of multiple wires.
▼Disadvantages of wireless charging
Slightly low efficiency: General chargers also have transformers, but the wireless charging transformers composed of transmitter coils and receiver coils have structural limitations, so the energy transfer efficiency is theoretically slightly lower than that of general chargers.
Charging speed is slow: Because the current receiving devices such as mobile phones mostly limit the input power, the charging speed is slow.
High cost: The charger needs to have an electronic circuit to push the coil, and the power receiving device needs to have an electronic device for power conversion, both of which need a coil, and a high-frequency filter circuit is required to meet electromagnetic compatibility, so the cost is more direct Charge higher.