What you need to know about wireless charging

2024 Author: Malcolm Clapton | [email protected]. Last modified: 2023-12-17 03:44

On the one hand, no more cable tangle. On the other hand, there is a problem with thick cases and overheating of the smartphone.

How wireless charging appeared

In 1820, André-Marie Ampere proved that electric current creates a magnetic field, and in 1831 Michael Faraday discovered the law of induction, which became the basis of modern wireless charging.

In 1888, Heinrich Hertz confirmed the existence of an electromagnetic field. His research helped Nikola Tesla transmit energy over a distance for the first time. It happened in 1893 at the Chicago World's Fair.

Until the end of the 20th century, many scientists experimented with the transfer of energy over a distance in different ways. Research is still ongoing.

Mass interest in wireless charging only began after the boom in mobile devices in the 21st century.

Today, the Wireless Power Consortium and the AirFuel Alliance are working on this issue.

What are the wireless charging standards

To charge a smartphone wirelessly, a pair of coils is used: one in the charging station, which is connected to power, the other in the device.

When a current appears on the first coil, a magnetic field is formed around it, which transfers it to the second.

The magnetic field appears due to the use of high frequency alternating current. It is converted to persistent when sent to the device.

Depending on the frequency of the current, magnetic induction or magnetic resonance is switched on.

Magnetic induction stations

They transmit energy over a distance of about 10 mm and use an alternating current frequency of 100–357 kHz for this. To charge a smartphone using such a station, it must support a specific frequency range.

The magnetic field does not penetrate metal, so wireless charging is only possible on smartphones with a glass or plastic back panel. However, even a thick protective case can interfere with the charging process.

Wireless chargers Qi and PMA work on the principle of magnetic induction.

Qi

Since 2008, the Qi standard has been developed by the Wireless Power Consortium (WPC), which includes charger manufacturers from America, Europe and Asia. Its specifications are publicly available.

This wireless charging standard has been used in the iPhone 8 and newer Apple smartphones, as well as in all Samsung Galaxy S devices over the past five years.

The companies Xiaomi, Huawei, LG, Sony, Asus, Motorola, Nokia, HTC also work with him.

PMA

The Power Matters Alliance (PMA) was involved in the development of the PMA standard from 2012 to 2015.

It is more common in the United States. There it was promoted by the cellular operator AT&T and the Starbucks coffee chain.

Today, the Power Matters Alliance within the AirFuel Alliance is developing an alternative type of wireless charging, AirFuel. But along with Qi, this standard is still supported by Samsung smartphones, including the latest flagships Galaxy S10, S10 + and S10e.

Magnetic resonance stations

Unlike stations operating on magnetic induction, they use a current frequency increased up to 6, 78 MHz. This allows you to expand the charging radius up to 40-50 mm.

These wireless chargers also use a set of two coils. But they may not be opposite each other, so chargers do not have to be made in the form of stands or rugs.

Wireless chargers of the Rezence and AirFuel standards work on the principle of magnetic resonance.

Rezence

From 2012 to 2015, Rezence was developed by the Alliance for Wireless Power (A4WP).

By increasing the charging distance, the standard was positioned as a more convenient alternative to Qi and PMA. A4WP is now part of the AirFuel Alliance and is working on the AirFuel standard.

Rezence was promoted by component manufacturers Broadcom, Gill Electronics, Integrated Device Technology (IDT), Intel, Qualcomm, Samsung Electronics, Samsung Electro-Mechanics, and WiTricity.

AirFuel

This type of wireless charging has not yet entered mass production. Its distribution potential is not yet clear, but Huawei plans to equip all its smartphones with it.

The AirFuel Alliance has been developing the AirFuel standard, which will be a continuation of Rezence, since 2015.

In theory, AirFuel can even be hidden under a table or other surface. Through it, stations will be able to simultaneously work with several devices: smartphones, headphones, laptops.

What you need to know about the power of wireless chargers

Wireless chargers differ in input and output power: it usually ranges from 5 to 20 watts.

Its level is indicated on the body of the device, on the box, on the official website of the manufacturer. It can also be found in the reviews.

Some companies indicate voltage in volts and amperage in amperes instead of power in watts. Their values also show how quickly the device can be charged.

Charging power in watts = voltage in volts × amperage in amperes.

Wireless chargers can be supplied without a power adapter. Their input power needs to be known in order to determine which one is suitable for their full-fledged work. The power of a standard power supply unit is 5 W for the iPhone, 12 W for the iPad, and 25 W for the Galaxy S10.

If the input power is sufficient, the device should deliver the maximum output power. Charging ZMI WTX10 Wireless Charger produces 18 W, dual dock Samsung EP-P5200 - 10 W, Apple-recommended charging Belkin Boost Up Special Edition - 7.5 W.

At the same time, you need to understand with what wireless charging power your smartphone works. iPhone 8, 8 Plus and X on iOS 12 support 7.5W, iPhone XS, XR and XS Max, Galaxy S10 - 10W.

To determine the approximate charging speed in hours from 0 to 100%, you also need to know the capacity of the smartphone battery in watt-hours and take into account the efficiency (efficiency) of wireless charging - usually 75-90%.

Charging speed in hours = battery capacity in watt-hours / charging output (or smartphone, if less) in watts / efficiency in% × 100%.

It will take at least 1⅓ – 1⅔ hour to charge the iPhone XS Max battery at 12.08 Wh using the ZMI WTX10 Wireless Charger. At the same time, it can be connected to the network with a standard power supply.

What you need to know when using wireless charging

How to install a smartphone on a charging station

Place your smartphone in a wireless charging center or in the place provided by the manufacturer.

Make sure charging has started. If this does not happen, your smartphone does not support this method of energy transfer, or you are using a case that is too thick.

How to avoid overheating during wireless charging

Your smartphone gets hotter than usual during wireless charging. To avoid overheating, it can temporarily shut off the power transmission when the battery reaches 80% charge.

Do not use bulky covers that interfere with natural heat transfer. And do not place foreign objects on top of the device being charged. It is dangerous to cover it with a cloth that will restrict air circulation.

How long can a smartphone be wirelessly charged?

The smartphone can be wirelessly charged all night long. When the charge of its battery reaches 100%, the transfer of energy will stop.

Most importantly, use a quality charger, cable and power supply to avoid short circuits.

Should you buy wireless charging today?

Wireless charging will be a good gift for a colleague or business partner, it will take its rightful place on your desktop at home or in the office.

But before buying a wireless charger, be sure to weigh its advantages and disadvantages.

Advantages

• You can just put your smartphone on the charger and it will immediately begin to replenish energy.
• No need to look for a cable with a suitable connector (Lightning, microUSB, USB-C).
• Reduces wear on power cables, ports and connectors.

disadvantages

• Wireless charging is slower than wired charging due to lower efficiency.
• A charging station is rarely included in the kit, usually you have to buy it separately.
• You cannot fully use the smartphone while charging.
• If you accidentally move the smartphone lying on the docking station, charging may stop.
• Thick protective cases and cases with metal parts can interfere with wireless charging.
• Wireless charging is not always convenient to take with you.

Wireless charging has more disadvantages than advantages today. While it is at the initial stage of development, you need to clearly understand where and when it is appropriate to use it.

The wireless charger is convenient on the desktop. You can put it on the bedside table and put your smartphone on it before bed. But it is completely inconvenient to take such a charge on a trip and use it on the go.

With the development of Qi and AirFuel standards, wireless chargers will be used everywhere. But for this, manufacturers will have to expand the range, increase the charging speed and deal with the rest of the shortcomings.