4 wireless charger charging methods that wireless charger manufacturers tell you
4 wireless charger charging methods that wireless charger manufacturers tell you
It has been a while since wireless chargers started to rise. Do you know any charging methods for wireless chargers? Let Yixin Chuangyan tell you! At this stage, there are four different ways of wireless charging: electromagnetic induction, electromagnetic resonance, electric field coupling, and radio wave. Among them, the technologies used in the wireless charging of mobile phones are mainly electromagnetic induction technology and electromagnetic resonance technology. Of course, once wireless charging breaks through technical barriers, it will also have very broad prospects in future home appliances and electric vehicles that are developing rapidly.
1. Electromagnetic induction method of wireless charger
Most of the various wireless charging technologies we see today use electromagnetic induction technology. We can regard this technology as a separate transformer.
We know that the widely used transformer now consists of a magnetic core and two coils (primary coil, secondary coil); when an alternating voltage is applied to both ends of the primary coil, an alternating magnetic field will be generated in the core. As a result, an AC voltage of the same frequency is induced on the secondary coil, and electrical energy is transferred from the input circuit to the output circuit.
If the transmitter coil and the receiver coil are placed in two separate devices, when electrical energy is input to the transmitter coil, a magnetic field will be generated. The magnetic field induces the coil at the receiver to generate current, so we build A wireless power transmission system.
The main drawback of this system is that the magnetic field weakens rapidly as the distance increases. Generally, it can only work in the range of a few millimeters to 10 centimeters. In addition, the energy is divergent in all directions, so the induced current is much smaller than the input current. , Energy efficiency is not high. But there is no problem for objects in close contact.
The first wireless charging product to use this principle is an electric toothbrush. Because electric toothbrushes are often in contact with water, they use a contactless charging method, which can make the charging contacts not exposed, enhance the waterproofness of the product, and can also be washed as a whole.
There is a coil in the charging socket and the toothbrush. When the toothbrush is placed on the charging stand, there is a magnetic coupling. The principle of electromagnetic induction is used to transmit power. After the induced voltage is rectified, the rechargeable battery inside the toothbrush can be charged.
The electromagnetic induction method is characterized by short transmission distance and relatively fixed use position, but has high energy efficiency and simple technology, which is very suitable for use as a wireless charging technology.
2. Electromagnetic resonance mode of wireless charger
Compared with electromagnetic induction, electromagnetic resonance technology has a certain tolerance in distance, it can support wireless charging from several centimeters to several meters, and it is more flexible in use.
Electromagnetic resonance also uses two coils with perfectly matched specifications. One coil generates a magnetic field when it is energized, and the other coil resonates and the current generated can light a bulb or charge a device.
In addition to the long distance, the electromagnetic resonance method can also charge multiple devices at the same time, and there are no strict restrictions on the location of the devices, and the flexibility of use ranks first among various technologies.
In terms of transmission efficiency, the electromagnetic resonance method can reach 40% to 60%. Although it is relatively low, it can be commercialized without any problems.
The electromagnetic resonance method transmits electric energy in the form of electromagnetic wave "radio frequency" or non-radiative resonance "magnetic resonance". It has high efficiency and very good flexibility, and is the current development focus of the industry.
Mobile phone wireless charger
3. Electromagnetic coupling method of wireless charger
Compared with the traditional electromagnetic induction method, the electric field coupling method has three advantages: the position of the device has a certain degree of freedom during charging; the electrode can be made thinner and easier to embed; the temperature of the electrode will not rise significantly, which is also quite advantageous for embedding .
First of all, in terms of location, although its distance cannot reach a length of several meters like MRI, it is also free in the horizontal direction. The user can charge the terminal freely on the charging platform.
We can see the comparison result of electric field coupling and electromagnetic induction. The misalignment between electrodes or coils is represented by the dz/D (center point distance/diameter) parameter. When this parameter is 0, it means that the two are completely overlapped. At this time, the energy efficiency In the highest state.
When this parameter is 1, it means that the two do not overlap at all. We can see that at this time, the electric field coupling method only reduces the energy input by 20%, and the device can still be charged normally, but the electromagnetic induction type has a slight error, and the energy efficiency drops rapidly. When the misalignment exceeds 0.5, it will not work properly. Therefore, the electromagnetic induction type always needs very accurate position matching.
The second feature of the electric field coupling method is that the electrode can be very thin. For example, it can use copper or aluminum foil with a thickness of only 5 microns. In addition, the shape and material of the material are not required. Transparent electrodes and thin-film electrodes can be used. In addition to square, it can also be made into any other unconventional shapes.
These characteristics determine that the electric field coupling technology can be easily integrated into thin and demanding smart phone products, which is also the most significant advantage of this technology over other solutions. Obviously, if the electric field coupling technology is adopted, smartphone manufacturers have a very loose degree of freedom when designing products, and will not suffer elbows in the design of charging modules.
The third advantage is that the temperature of the electrode part does not rise-a problem that plagues wireless charging technology is that the high temperature during charging will cause the battery pack close to the electrode or coil to be heated and deteriorate, which will affect the life of the battery.
The electric field coupling method does not have this problem, and the temperature of the electrode part will not rise, so there is no need to be too deliberate in the internal design. The non-heating of the electrode part is mainly due to the increased voltage. For example, when the voltage is increased to about 1.5kv during charging, the current intensity flowing through the electrode is only a few milliamperes, and the heat generation of the electrode can be controlled ideally.
However, the fly in the ointment is that the power circuits of the power transmitting module and the power receiving module will still generate a certain amount of heat, which generally causes the internal temperature to increase by about 10 to 20°C. However, the circuit system can be configured at a remote location to avoid damage. The internal battery is affected.
The electric field coupling method has the advantages of small size, low heat generation and high efficiency. The disadvantage is that there are fewer developers and supporters, which is not conducive to popularization.
Four, wireless charger microwave resonance mode
Intel is a proponent of the microwave resonance method. This technology uses microwave as the energy transmission signal. After the receiver receives the energy wave, it is restored to the DC power available for the device through the resonance circuit and the rectifier circuit.
This method is equivalent to our commonly used Wi-Fi wireless network. Both the sender and receiver each have a dedicated antenna. The difference is that this time it is not a signal but electric energy.
The frequency of microwave is between 300MHz and 300GHz, and the wavelength is in the millimeter-decimeter-meter level. The ability of microwave to transmit energy is very powerful. The microwave oven in our family uses its thermal effect, and Intel’s microwave wireless charging technology, It converts microwave energy back to electrical signals.
The shortcomings of the microwave resonance method are quite obvious, that is, the energy is divergent in all directions, resulting in surprisingly low energy utilization efficiency. For example, Intel's solution provides power supply as low as 1 watt, which at first glance seems rather limited in practicality. And its advantage is that the location is highly flexible, as long as the device is placed near the charging device, the location requirements are very low, and it is the most natural charging method.
We can see that when the transmitter and receiver of the device are completely overlapped, the energy efficiency of electromagnetic induction and microwave resonance methods both reach their peaks, but electromagnetic induction is obviously superior. However, as the displacement occurs in the X-Y direction, the electromagnetic induction method has a rapid attenuation, while the microwave resonance is much gentler, and it is quite usable even if the displacement is large.
Although energy and efficiency are at a low level, and practical value is relatively limited at first glance, as a giant in the PC industry, Intel has the ability to turn corruption into magic, and its approach is quite clever: Intel designed ultrabooks as wireless The sending end of charging, the mobile phone as the receiving end, so as long as the mobile phone is placed next to the ultrabook, it can be charged unconsciously and continuously-I believe that most users put their mobile phones on the desktop when they are at work The habit of charging, charging can begin in the background.
Even though the microwave resonance method used by Intel can only be charged with a very low power, the power of smart phone products will almost never be exhausted under long-term charging, at least from the user's point of view, because as long as he carries a laptop Computers no longer need to pay attention to charging issues at all.
Although the wireless microwave method has low energy efficiency, it is the most convenient to use. The emergence of mobile phone wireless chargers has greatly improved people's lifestyles, making mobile phone charging more convenient and smart.