Wireless charging for a smartphone: how it works

In the first half of February this year, The New York Times reported that Apple has developed a new wireless charging technology for mobile devices that will be used in their products in the future. The new device is intended not only for existing gadgets, but also for those that are only planned to be released to the market.

In the foreseeable future, the guys from Cupertino will give their users the opportunity to experience all the benefits of wireless charging. At the same time, now, charging devices that work on the principles of magnetic induction are produced by some companies, for example Nokia (smartphones of the Lumia line) and LG (Nexus 5).

The new technology has received the generally accepted name QI, which is translated from Chinese as an “energy flow”. Developed this functional association Wireless Power Consortium, uniting more than 100 companies, including Panasonic and Sony. To date, this association – the only company that has approved the interface, with which you can use wireless charging devices

The first specifications for the new technology appeared in 2010, and a year later, the mobile operator Verizon offered smartphones that had a wireless charging function. A vivid example of such a smartphone is the Samsung Galaxy.

In the past 2013, a new technology appeared in many devices of the highest price category, working on the basis of Android. Currently, you can charge these devices in two ways. The first is traditional cords that have a microUSB or miniUSB connector. Second – special mats, which are easy enough to put the device.

Among the shortcomings is high cost. The price of a wireless charger, for example, for LG Nexus 4 starts at $ 50. At the same time, there are still no such devices on the Russian market.

According to the specifications of the new standard, the current used for charging should not exceed 5 watts. When users began to study the functionality, as well as the rules of using the device, it turned out that the standard for such “charge” does not discuss the specific methodology by which the mobile gadget will be filled with energy. Currently, manufacturers of wireless chargers use in their development induction “method.”

This method involves the use of a charger as an energy transmitter, while the smartphone acts as a receiver and must be equipped with a special induction coil. In it, under the influence of an electric current, a magnetic field with variable indices appears. If a magnetic field induced by the charger acts on the coil of the smartphone, then an electric charge will be generated in it.

or efficient energy transfer, it is necessary to have a qualitatively “channel” between the receiver and the coil (perhaps not even one). According to the QI standard, all of the above devices must be at a certain distance from each other, which varies from 3 to 8 centimeters (maximum – 10 cm). If this requirement is not met, then the transfer of energy will be ineffective.

As soon as the smartphone hits the surface of the charger or its magnetic field, the charge is formed in the latter. At the time of electricity transmission, especially in the background, the charger receives a pulse with an interval of 0.4 seconds. If the voltage in the device remains unchanged, this indicates that the “charging” is off. If the voltage decreases, the device receives an impulse informing that a smartphone has been attached to it. In this case, the smartphone responds by increasing the voltage to the operating state. Only after this, the transmission of energy begins. A special receiver informs about the efficiency of the process, which sends pulses with an interval of 32 milliseconds. As soon as the battery of the gadget has filled the energy level, the receiver sends an impulse,

Thus, QI users do not need to worry about the energy efficiency of the chargers that perform their work according to established standards.

Between charged and discharged mobile gadgets, an exchange is performed using phase modulation of the magnetic fields. According to the QI standard, the data exchange protocol between the specified devices in a different energy balance is carried out at a speed of 2 kilobits per second.

The energy efficiency of QI technology is 80%. This is a fairly high figure. For standard wired chargers, this parameter varies from 75% to 95%.