Everything You Should Know about Wireless Charging

Table of Contents

Wireless charging technology is an “old man” with over 130 years old. However, it becomes prevalent after the iPhone supports it.

Today I’m going to share the information related to wireless charging. It covers what wireless charging is, why wireless charging is needed, how it works, and more.

What is Wireless Charging?

As the name implies, wireless charging is charging without a cord. Like WIFI, wireless charging gives you the freedom to power your phone and other electronic devices anywhere, anytime.

However, temporarily wireless charging cannot do the distance like WIFI. And the mature solution can work for mobile devices in 10mm only. Generally, 3-5mm is a distance to work better. 

With the development of technology, the distance of wireless charging is expected to reach 10-30cm in 2-3 years. Then it will meet the daily demand of unrestrained charging anytime and anywhere.

To achieve wireless charging, it needs a transmitter and a receiver. Usually, the transmitter is a wireless charger, and the receiver is a mobile phone. And it requires a coil each to connect. When the transmitter transfers the energy via the control board and coil, the receiver receives the power through the control board and coil. 

Why Do You Need Wireless Charging?

Compared to traditional wired charging, here are some advantages here.

1. No wire winding, beautiful, and straightforward.

2. No need to plug and unplug frequently. Just put the mobile phone on the charger. It is convenient and lets your phone never run out of power.

3. No need to worry about the incompatibility of mobile phone interfaces.

4. No risk of electric shock when charging and answering phone calls, avoiding the safety problem.

P20w Wireless Power Bank

How Does Wireless Charging Work?

In general, the mobile phone wireless charging principle is like this. Firstly, electric energy converts into a magnetic field. Then it transmits through the air and converts into electric power again. 

There are 4 wireless charging types: electromagnetic induction, electromagnetic resonance, radio reception, and capacitive coupling. But only the first 2 types are the mainstream, so let’s dive into them.

Electromagnetic Induction Wireless Charging

It works with 4 steps below. 

1. The transmitter coil in the charging base sends out an electric signal.

2. When the receiver coil touches it, the electric signal is received.

3.The electricity inside the transmitter coil starts to move around and generates a magnetic field.

4.The magnetic field transfers to an electric field through the receiver coil and powers the devices.

Electromagnetic induction wireless charging can only support 1-to-1 wireless charging. It has defects such as low charging power and short charging distance.

Electromagnetic Resonance Wireless Charging

It is the particular condition of electromagnetic induction wireless charging. Like the resonance of our voice, resonance occurs if the resonant frequency of the receiving coil is the same as the one of the transmitting coil. And when the resonance occurs, the energy transferred from the transmitting end to the receiving end.

Electromagnetic resonance wireless charging can support high charging power, long-distance, and 1 to many charging methods. However, it needs the same resonance frequency in the transmitting end and the receiving end. For now, this problem is still hard to solve.

Charging Efficiency of Wireless Charging

The current efficiency of wireless charging is about 70% (mostly 65% to 75%). There will be some differences according to the quality of different chargers and transmitters. If you look at the transmitter and receiver separately, the transmitter efficiency is about 80%; the receiver efficiency is about 90%. And the overall efficiency is about 70%. 

The efficiency of wireless charging is related to many factors. In addition to the wireless charging base and receiver, it also has some relationship with the adapter’s quality and the load situation.

Wp101 Wireless Powe Bank

Wireless Charging Radiation

Some people said wireless charging is dangerous because it is with radiation. 

Yes, it is. But do not worry about it. It is not enough to be of any serious concern.

Here are the 4 seasons.

1. The max wireless charging power is 15W. It is just a little power.

2.The distance is limited to 25px only.

3.Both the transmitting and receiving ends have magnetic isolation pieces, which have little radiation to the surroundings.

4.The working frequency is low (110K~205KHz), and the radiation to the human body is small.

Wireless Charging Standard

The wireless charging industry used to have 3 significant standards organizations (WP, PMA, and A4WP). But in 2015, PMA and A4WP were merged and rebranded as AirFuel Alliance.

WPC is the earliest established standard organization, and its certified brand is the familiar “Qi” logo.

Powermat initiated PMA. Its certified brand is Power2.0, and it also uses magnetic induction wireless charging technology.

In North America, PMA standard products have layouts in McDonald’s and Starbucks. Now there are more than 70 members, mainly in Europe and America.

A4WP is the latest to be established, initiated by Qualcomm and Samsung. Its certified brand “Rezence” was only released at the end of 2013. Still, many major international manufacturers have joined in and started to promote A4WP standard products. A4WP uses magnetic resonance wireless charging technology. The charging distance can reach 5cm. And supports one-to-many (a transmitter can charge multiple receiving electronic devices simultaneously) also does not require precise alignment.

The comparison between WPC’s Qi standard and A4WP’s Rezence standard is as follows.

WPC’s Qi standard

Advantages: early establishment, many members, mature products, complete ecosystem, and tremendous industry influence. The cost of the solution is cheap, and the penetration rate is high. The charging efficiency is high, which can reach over 70%. The radiation is small, and the safety is good.

Disadvantages: The charging distance is small, and precise alignment is required. Only one-to-one charging is possible, but the gap is not big after subsequent upgrades.

Rezence standard for A4WP

Advantages: The charging distance is longer, the moving range is broader, and it can be charged one-to-many.

Disadvantages: The development is late, the market is not mature enough, and the ecosystem is still lacking. The cost is high, and the short-term popularization pressure is high. The charging efficiency is slightly lower, and there is radiation also related to risks.

Composition of Wireless Charger

The wireless charger is mainly composed of 3 parts: mainboard, coil, and shell. And the mainboard is the core part; it directly determines the function and performance. The mainboard is built in the main control chip, a driving chip, a power device (MOS), a resistance capacitor, and a PCB board. The coil is a standard module; the related wireless charging standards strictly stipulate its structure and size parameters. 

Cost Breakdown of Wireless Charger

Knowing the composition of the wireless charger, you can roughly get the cost of the wireless charger. However, due to the difference in function and performance requirements, wireless chargers’ prices will vary greatly. In particular, the products that have passed certification are much higher than those that have not.

Here is the rough cost breakdown.



So, I hope you get the value out of this post.

The world is rapidly changing. So does Morui. 

Now Morui has some wireless power banks, which can support you free of charge on the go.

If you are interested in or have any questions, please let us know. We will try our best to do the solution with our passion.

Hi, I’m Ryan Gao, a father of 2 kids, also the content manager of MoruiPower.com. I’ve been working on consumer electronics for 8 years now. On this site, I like to share with you the knowledge related to power banks, wireless headphones, and portable power stations from a Chinese supplier’s perspective.

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