How does Wireless charging work? Explained!

Hey friends, Happy Wednesday!

I’m including an extended summary of how a gadget works in my newsletter, from which you can understand the essence in less than 3 minutes.

Let’s look at how Wireless charging works this week. I aim to write my newsletter issues in a way one can follow them while traveling on a bus, having a coffee, waiting for food, etc. Let's jump in!

Tweet of the week

I’m sharing a cool fact about gadgets every day on Twitter. And here is one of them for you!

Ever wondered how your fitness watch detects your heartbeat?

It uses Photoplethysmography (PPG), which is an uncomplicated and inexpensive optical measurement method that is used to achieve the same

— Chendur Singaram (@ChendurSingaram) May 9, 2023

How does Wireless charging work?

Introduction

Wireless charging is based on the principle of transferring electrical energy from a power source to a device utilizing electromagnetic fields to transmit power wirelessly. This is made possible through a combination of two essential components: a transmitter (or charging pad) and a receiver (embedded in the device being charged).

Principle

According to Faraday’s law of electromagnetic induction, an electric current is induced in a conductor when it is exposed to a changing magnetic field. This principle forms the basis of how wireless charging operates.

Working

Figure 1: Magnetic field generated by charging pad coil going through the phone's coil and inducing current.

1. Transmitter (Charging Pad):
   The transmitter, typically a charging pad or mat, is connected to a power source through a cable. It consists of a coil of wire that carries an alternating current (AC). This alternating current generates a time-varying magnetic field around its coil.

2. Receiver (Embedded in the device like your phone):
   The device to be charged needs to have a compatible wireless charging receiver embedded within it. This receiver, usually located on the back of the device or beneath the battery cover, comprises another coil of wire.

3. Power Transfer Process:
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   a. When the charging pad is connected to a power source, an alternating current flows through the transmitter coil, generating an oscillating magnetic field around it. This magnetic field is then picked up by the receiver coil in the device.
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   b. The alternating current induced in the receiver coil is converted to direct current (DC) and regulated to the appropriate voltage and current levels required for charging the device’s battery.
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   c. The regulated DC power is then supplied to the device’s battery for charging. The charging circuitry within the device manages the charging process to ensure optimal battery performance and safety.

Limitations

The power transfer efficiency is generally lower compared to traditional wired charging, resulting in slightly slower charging times. The range between the charging pad and the device is also limited, requiring close proximity for effective power transfer.

And this is how wireless charging works. Thank you for reading!

Have a nice rest of the week, and take care!
Until next Wednesday,
Chendur