Wireless charger: how it works

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Alejandra Rangel
@alejandrarangel

The electromagnetic induction

Before going into the merits of the matter and explaining all the details on how a wireless charger works, it is good to briefly mention the physical concepts that dominate this mechanism: since my goal is to make you understand everything in very simple terms, I am going to start with an example that you have surely already dealt with: induction kitchen tops.

Induction kitchen hobs, those capable of cooking food without heating the cooking area at all (unlike, however, glass ceramic hobs) exploit the principle ofelectromagnetic induction, the so-called Faraday's law, for which the energy generated by the cooking area (ie the "stove"), in contact with the bottom of the pan, generates an electromagnetic field capable of activating the iron "particles" present in the pot itself. These particles heat the pan which, in this way, cooks the food contained in it.



For this reason, even if the pans are hot, the cooking zones of an induction hob are always "cold" (there is no heat transfer but energy "moved" in a field). Furthermore, to take advantage of induction, the bottoms of the pots must be made of materials that can generate electromagnetic fields in contact with the hob.

But how does energy "move" from one point to another in an electromagnetic field? The "secret" is there force. To explain this with an example, think of two people stretching a rope (which you can imagine as an electromagnetic field): if one of these gives the rope a force, moving it to generate waves, these waves will also arrive on the other side of the rope. , without the second person making any movement.

The operating criterion of a wireless charger is very, very similar to what I explained to you a little while ago: thanks to the transfer by electromagnetic induction, it is possible to send theenergy generated by the charging base (via the electricity that the base receives from the socket to which it is connected) directly to the device battery, through the appropriate sensors transmitters placed on the base e receivers residing on the device.



Clearly, the larger the electromagnetic field, the faster the energy transfer. This, however, does not mean that a larger charging base can power a battery more quickly: to avoid overload or physical damage to devices or even people, the manufacturers of chargers and smartphones limit the battery. maximum voltage. Furthermore, currently, the materials of construction of the devices constitute a limit for the speed of transfer by induction.

What does Qi mean

Now that you understand how the power transfer between the charging base and the device works, it's time to say a few more words about wireless charging. First of all, in this sector, the protagonists are two large organizations: the WPC (o Wireless Power Consortium) and the WFP (o Power Matters Alliance), both of which are committed to perfecting and improving the aforementioned technology.

In particular, the WPC deals with managing the standards with which wireless charging is implemented and implemented by manufacturers: the most common of these is the standard Qi, used by the vast majority of manufacturers who take advantage of wireless charging, including Samsung, NokiaApple. Qi uses the principle of electromagnetic induction seen a little while ago for recharging, and defines, in addition to the methods of construction of the modules and sensors dedicated to charging bases and devices, including safety regulations aimed at preserving the safety of things and people (e.g. to avoid overheating of the parts involved).

The Qi standard, for charging to be successful, requires that the charging base and the sensor placed inside the device (smartphone, smartwatch, etc.) are very close to each other, at a minimum distance of 45 millimeters and a maximum of 400 millimeters, and perfectly aligned.



Thanks to this standard, over time, wireless charging has made great strides, almost completely eliminating the risks associated with its use and significantly reducing charging times, especially on the most powerful devices. Technology too WFP, although less common, it uses electromagnetic induction to carry out wireless charging, but with different criteria and hardware than the Qi standard.

In theory, the Qi standard would be able to transfer energy also through magnetic resonance, thus eliminating the need for the devices involved to be very close and aligned. At the time of writing this in-depth analysis, Samsung would seem to be serious about pursuing this discussion. Impressive, isn't it?

How a wireless charger works

If you have read carefully what I have explained so far, the criterion behind the operation of a wireless “charger” should be quite clear to you, so it's time to finally get to the practice!

A wireless charger consists of one basis, on which the device equipped with a battery must be placed, and a power cord to be connected to electricity. The base may contain rubber strips, useful for holding the device still, and on it there are one or more charging points: marked with a symbol, these contain i energy transmitters which, upon coming into contact with the electronic device whose battery is to be recharged, generate the electromagnetic field predisposed for transfer.

But how does the charger “notice” that it has to recharge a device? The explanation is quite simple: the transmitters placed on the base, at regular intervals, send a "control signal" to check the presence of the receivers installed in the charging devices. When the devices are detected (the signal comes back with different characteristics), the transmitters create an electromagnetic field with the receivers, to start immediately after induction charging.



How to choose a wireless charger

I bet you've learned the basics of how a wireless charger works and so you can't wait to buy one. The first thing you have to do, then, is to check that the device in your possession is set up for wireless charging mode, then you have to keep in mind some parameters of choice that I am going to illustrate below.

  • Compatibility - not all wireless chargers support both charging standards seen above. So, before purchasing, check if your device is compatible with the standard Qi, with the standard WFP or with both, and choose accordingly.
  • Shape - usually, the charging surface of such a battery charger is in a horizontal position and can be round, square or any other shape. There are some chargers that, to make it more "convenient" to use the device while charging, have a charging surface that can be positioned vertically.
  • Charging points - some chargers of this type are equipped with several charging points, i.e. several areas equipped with transmitters. However, this is not a guarantee of faster recharging, nor of the possibility of recharging multiple devices at the same time (currently it is not possible to do so): the “receiver” device must be compatible with transmission from multiple recharging points. However, I advise you not to opt for chargers with multiple charging points: at the moment, you would not find the use of it.
  • Battery e additional connectivity - some wireless chargers have an “external” battery available, which makes them de facto wireless Powebanks. In addition, one or more doors can also be found on them USB, useful for charging multiple devices at the same time (one in wireless mode, the others via cable).
  • LED Indicators - on the market, there are wireless chargers equipped with indicator lights, which allow you to check if the device is being charged.

Wireless charger

If you want, below you will find a selection of wireless charger among the most interesting that you can currently find on Amazon.

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3-in-1 wireless charger

These models are very useful for charging all your compatible devices with a single charger, even at the same time. You can then use them with one or more smartphones, or even with a smartwatch or with the case of a pair of true wireless earphones, if needed. All with one device.

Below you can find a selection of the best 3-in-1 wireless charger currently on the market. Before buying one, however, check its characteristics well: some of them, in fact, are designed for charging two devices and only offer a place to insert the charger of a third device (e.g. the charger of a smartwatch).

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Cases with receivers for wireless charging

How do you say? Your device is not natively compatible with wireless charging but, given all its advantages, would you like it to be? I have the solution for you: for a few euros, you can find receivers which can be connected to your smartphone, tablet or other device via port microUSB, USB-Clightning. Once connected, you can place them directly on the wireless charger to start charging your device.

In short, depending on the characteristics most congenial to you, you can find chargers of all shapes on the market, some cheap, others a little more expensive in terms of price. If you have multiple devices compatible with wireless charging, buying a charger of this type is almost a must, don't you think?

Wireless charger: how it works

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