Give Qi to each bedside table! Or why wireless charging is the future.

    Hi, Giktayms! Technology is now developing so fast that it is difficult to keep track of them. It seems that recently they were surprised at devices with touch displays, and here they are announcing a frameless smartphone . We use many of the fruits of modern smartphone construction every day and often do not even think about how it all works. Today we will talk about wireless charging (iPhone owners are not advised to leave, at the end there will be a surprise for them).



    As everything happens from the user's point of view, the owners of mobile devices are well aware: they came home or to work, put the device on a special stand or nightstand (yes, IKEA last year pleased geeks with furniture with an integrated charging device) - and the cherished interest right there rush up. For everything to be so simple, manufacturers, including Qualcomm, Intel, NXP and many others, took a lot of time and effort to introduce commercially attractive wireless chargers to the market.

    A dispute is widespread among experts: is it possible to consider charging wireless if, in fact, a cable is used for it, even if it is connected not to a smartphone, but to another device? Since in this case the wireless method of energy transfer is still involved, quite. There are several ways to do this, but in electrical engineering the most common are solutions that use the phenomenon of electromagnetic induction for wireless transmission of electricity.

    Little about technology


    We will analyze the method of electromagnetic induction in more detail, for now let's talk about other methods of contactless transmission of electricity. One of them is ultrasound. In this case, the transmitter emits ultrasound, and the receiver performs the conversion to electricity. The ultrasonic method was presented to the public in 2011, and at the presentation it could already transmit electricity at a distance of 7-10 meters, although the direct visibility of the receiver and transmitter was still necessary. The transmitted voltage reaches 8 volts.


    Demo technology at the 2011 D9 exhibition

    Microwave radiation is familiar to everyone. But for the reverse conversion of microwave energy into electricity, rectenna with a conversion efficiency of at least 95% is required. In addition, the transmitting antenna and rectenna should be large in size (about 1 km and 10 km, respectively), which makes such a method of energy transfer only relevant for space purposes. Experimentally, wireless transmission of energy using microwaves has been confirmed, but has not received practical application, especially among consumer devices.

    If the wavelength of electromagnetic radiation is from 10 μm to 10 nm, that is, close to the visible spectrum, it becomes possible to transfer energy by converting it into a laser beam, which is then directed to the photocell of the receiver. The small angle of divergence of the monochromatic light wave increases the efficiency of energy transfer over long distances, the compact size is convenient for small devices, and the laser does not create radio frequency interference for cell phones. Nevertheless, in smartphones, it was abandoned for an obvious reason - the inefficiency of converting low-frequency electromagnetic radiation into light and light into electricity (photoelectric cells with efficiency of 40-50%), high losses in the atmosphere. Therefore, basically the transfer of energy by laser is tested in space.


    For commercial purposes, only one technology of wireless transmission of electricity is used: by means of electromagnetic induction.

    Thanks to Tesla and Faraday



    Thanks to these great scientists, research in the direction of the transmission of electricity through the air by electromagnetic induction was obtained. Back in 1831, Michael Faraday discovered an important basic law of electromagnetism, the law of induction, and in 1893 Nikola Tesla demonstrated wireless lighting with fluorescent lamps in a project for the Columbian World Exhibition in Chicago. Now wireless charging is used in the whole arsenal of devices - from toothbrushes to smartphones and cars.

    Speaking more or less simple language, the work of wireless charging is based on the properties of an induction coil to transmit electric current. When it is connected to a power source, a magnetic field arises in it, which is perpendicular to the turns of the coil itself. So if you connect the power to one coil and place the second one in the range of its magnetic field, voltage will appear in it. In this case, under no circumstances should the two induction coils be in contact with each other.


    One of the coils must necessarily act as a source, that is, electricity must be connected to it, and the second must be a receiver, so it’s impossible to completely abandon the wires. The two coils form a system with inductive coupling, as in the figure above. In the winding of the source (first coil) alternating current flows, which creates a magnetic field. The latter induces a voltage in the coil-receiver: it can be used both to power the device and to charge the battery. If the secondary coil is far away from the primary coil, the magnetic field is dissipated because it cannot reach it. Therefore, upon removal, the inductive coupling becomes ineffective.

    In modern times, two technologies of wireless charging using electromagnetic induction are common. One uses strongly coupled coils (MI is magnetic inductive), and the other is weakly coupled (MR is magnetic resonance). The WPC Wireless Electromagnetic Energy Consortium is based on MI technology, A4WP recommends using MR. MR systems require higher Q values ​​(from 50 or more) than in MI systems, whereas for existing wireless charging systems, the Q value is 30 to 50.

    Therefore, now the basis of wireless chargers is MI technology - the specification itself (standard), in accordance with which devices are created, is called Qi. In the Russian transcription, it is pronounced "Qi", which means the flow of energy. The first version of the standard allows you to charge devices at low power (5 watts), and the second - at high (120 watts). If the first is used to charge the batteries of smartphones and tablets, then using high power you can even charge the laptop. True, high-power Qi has never come to commercial use.


    Manufacturers are actively storming the Qi standard, using it in their smartphones and tablets. In the novelties of this year, the Xiaomi Mi5 ( in white too ), the Xiaomi Mi4s and the Blackview R7 Qi are not, but there is the Quick Charge technology, with which smartphones will charge much faster. The charging module can be placed anywhere, at home and at work, and if you combine it with a piece of furniture (the same lamp from IKEA), you can minimize the number of wires.


    Circular and rectangular transmitters, also called transmitters, are common among users. It should be noted that the magnetic field is capable of transmitting not only electric current, but also data on bytes and bits, which they used to create the Qi standard. The coils will not interact with each other if the gadget with the built-in transmitter is not located near the transmitter. As soon as the smartphone battery is charged, it will give the desired signal, and the transmitter will start working in the background. When the accessory functions in the background, the pulse sent every 0.4 seconds by the transmitter will not change the voltage in the coil built into the transmitter. However, by reducing the distance between the smartphone and the accessory to the desired distance, the device will go into active mode,

    Although charging smartphones and tablets with Qi and the corresponding accessories is slower than using a cable, the technology is still in noticeable demand among users. Agree, it is much more convenient once to create a small “pad” near the bed to charge all the devices than to unravel 4-5 cables every evening - from your smartphone, your wife’s phone, smart watches, and if you also decided to charge the external battery, so it’s a disaster.

    Isn't that bad?



    Many ask this question before using Qi, because the magnetic field has radiation. Nevertheless, magnetic radiation is not ionizing - it affects the human body no more than Wi-Fi or a mobile signal. In addition, the electromagnetic radiation disappears immediately, as the battery of the device is charged, and the power of 5 watts is not enough to have a negative impact. No wonder wireless charging is used even in razors and toothbrushes.

    What if the Android smartphone does not support Qi? Do not worry, in this case, manufacturers produce a whole range of special accessories, and the cost of many does not exceed five dollars. They consist of a transmitter and a special receiver that plugs into a standard charging port — the same micro USB. The receiver can be fixed, for example, with the help of a cover, and in fact get a smartphone with Qi.


    iPhone in the span?


    Although Apple threatens to make a wireless charging with the ability to remove the device from the transmitter to a distance of one meter (for keyboard and mouse), while Qi is not even in iPhone 7 and iPhone 7 Plus. But the way out, as we promised at the beginning, is - as is the case with Android devices, craftsmen from China have created special accessories . The receiver connects to the smartphone using Lightning, after which it can be used with any Qi accessories for charging. Yes, even with furniture and transmitters for Android devices. So everything is in your hands!


    Future without wires



    Over the past few years, many have joined the elements of Qi, including automotive manufacturers. They also understand that technology is gradually moving away from the wires, and the extra cables in the car do not need anything at all. Of course, a small radius of action still remains the main obstacle, but it will be overcome, moreover, in the near future.

    Also popular now: