Inductive/Wireless Charging
Have you ever charged your smartphone by simply placing it on the charging pad? That’s wireless charging, which makes it easy and expedient to charge your phone without the need for unwieldy charging cables or annoying plugging. But how does wireless charging actually work and what are its possible applications? Read on to find out.
What are Wireless Charging Coils?
Wireless charging coils produce an alternating electromagnetic field (EMF) used to transfer energy via induction to another coil that is placed parallel and nearby. You can use this power to operate the gadget getting the energy or to charge a battery.
What is Inductive Charging?
Wireless charging occurs through a process called inductive charging. It is a kind of wireless energy transfer that uses electromagnetic induction to provide power to portable devices.
Electromagnetic induction basically occurs through inductive coupling. Here's how it works:
• Alternating current (AC) passing through an induction coil in the charging station creates a magnetic field.
• This field fluctuates in strength because of the fluctuating amplitude of the electric current.
• The varying magnetic field generates an AC in your smartphone's induction coil, which in turn flows through a rectifier to convert it to direct current (DC).
• Lastly, the DC charges the battery of your phone.
What are Wireless Charging Coils Made of?
Wireless charging basically involves a coil and ferrite assembly. The first layer is a coil made up of copper and wound in the shape. Its primary function is to act as an antenna to transmit or receive wireless energy.
Under the coil is a layer of ferrite, whose main function is to concentrate the magnetic flux from the transmitter to the receiver. It directs the field in the proper direction to have good coupling and is secondary to have electromagnetic interference (EMI) shielding.
How Wireless Charging Works
Wireless charging doesn’t work entirely without cables. You still have to connect the charging station with the socket through a power cable and it stays connected continuously. However, your phone is charged wirelessly. You only have to place it on the charging pad.
The alternating current flowing through the coil encompassed in the charging pad creates an electromagnetic field. When a phone is within this electromagnetic field, the coil present in its receiver part is charged inductively.
As explained earlier, inductive charging means that a varying electromagnetic field in a nearby metal piece produces an electric current. In a smartphone, the rapidly fluctuating current is transformed into a steady current with the corresponding circuitry. This current then charges the battery of your smartphone.
Wireless charging can only be used over very short distances as the coils in the receiving and transmitting devices are small. Many everyday use products like shaving razors, induction stoves, and electric toothbrushes have already been using this inductive charging mechanism for several years.
Main Industries That Use Wireless Charging
Several industries rely on wireless charging coils, however, the three industries most heavily focused are the automotive, medical, and industrial sectors. That’s because this technology offers the potential of better mobility and improvements that could allow small internet of things (IoT) devices to receive energy several feet away from a charger. Some other industries that are leveraging wireless charging include telecommunications, consumer electronics, 5G wireless, and datacenters.
Benefits of Wireless Charging
The biggest benefit of wireless charging is to make it easier for electronic products to charge without needing a charging cable or plugging into a socket. This makes it much easier and more convenient to charge your devices – whether you are at home or out and about.
If the charging station always stays in the same place (like in your office or at home), you do not have to look for charging cables. Plus, many fast food and coffee outlets have also installed publicly accessible charging stations on their tables that allow you to charge your phone battery while you are on the go.
Another great benefit of wireless charging is that the charging socket of your smartphone is not frequently used and, consequently, experiences less wear and tear. This also decreases the risk of moisture and dust penetrating into the phone, as such damage is often caused by the charging sockets. Moreover, if you’re an iPhone user, it also frees up the headphone port on your phone.
For some medical applications (such as embedded devices inside a human's body), wireless / contactless power is a must.
Wireless charging has also helped enhance safety levels when driving, keeping driver’s focus on the road without drawing their attention to handling wired charging cables.
Applications of Wireless Charging
Apart from charging smartphones, this technology is being used increasingly for several other devices such as:
• Electric vehicles
• Scanners
• Medical devices
• Smartwatches, Bluetooth headphones, and other wearables
• Power tools such as cordless screwdrivers
• Smart kitchen gadgets
• Notebooks and tablets
• Service robots such as vacuum cleaners and lawnmowers
• Electronic toys and drones
Wireless Charging vs. Wired Charging
Energy Consumption & Efficiency
According to a case study presented by Wireless Power Consortium (WPC), assuming that the average charging power is 2W, the total energy used by the wireless charger in a year is 2.62 kWh. On the other hand, the total energy used by the wired power adapter in a year is 2.19 kWh. Moreover, the average system efficiency of a wireless charger is 50%, whereas the average system efficiency of a wired charger is 72%.
However, the case study also revealed that using a single wireless charger with a multiple-load charging feature has distinct benefits over using discrete one-to-one wired chargers. This benefit becomes more important when the wireless charger can substitute two or more wired chargers.
The energy-saving benefits of replacing multiple wired chargers arise from the decrease in standby power as well as the decrease in manufacturing and transportation energy of redundant wired chargers.
Apart from the energy savings aspects, the possible decrease in the amount of electronic waste occurring from the decrease in the number of traditional wired chargers also adds significantly to environmental security in the long term.
Speed
In terms of the speed of charging, a 5W wireless power adapter typically takes around 3 to 4 hours to charge fully. On the other hand, a 5W wired power adapter takes roughly 2.5 hours.
This occurs even though many latest smartphones include fast-charging technology that lets them draw more energy when being charged. Therefore, if you have an older smartphone model, it may charge even more slowly.
One way smartphone manufacturers can increase wireless charging speeds is by updating their operating systems accordingly. However, the speed of charging is still dependent on several other aspects including:
• the temperature of the air
• the age of the smartphone and battery
• the smartphone’s battery level when you place it to charge
• where the smartphone is placed on the charging station
Is Wireless Charging Safe?
Generally speaking, wireless charging is quite safe as the charging stations have shielding so the range of the electromagnetic field is very limited or is targeted in a particular direction. Moreover, in the case of smartphones, the electromagnetic field is weak and exists only when you are charging the device.
There is a risk with foreign metal items. For instance, induction stoves can become exceedingly hot when they get into the electromagnetic field of the charging coil. However, we now have smart charging stations that identify when a foreign item is between the smartphone and the charging pad, thereby stopping the charging process.
What is a Qi Charger?
To wirelessly charge your smartphone, you need a Qi Charger.
Qi standard is established for inductive charging so that users don’t have to switch to different chargers for different smartphones. For instance, you can use a Samsung wireless charger with an iPhone.
Introduced in 2009, Qi (meaning ‘life force’ in Chinese) is an internationally accepted wireless charging standard for providing 5W to 15W of power to small personal electronic devices. It is a wireless charging method from the Wireless Power Consortium that’s based on closely coupled electromagnetic induction, necessitating the device to be aligned on top of the coil on the charging station.
Even though the standard is mainly used to charge smartphones, it can also be used to provide power for an increasing number of consumer devices.
Do Qi Chargers Draw Power When Not in Use?
Qi Chargers have a standby mode, i.e. when a product is not placed on the charging pad, they will use very small amounts of power (typically less than 0.01W, according to NXP that manufactures the Qi chips). This is similar to a wired charger.
What Phones are Compatible with Qi Chargers?
Qi charging already has compatibility with the latest smartphone models, such as Apple iPhone (8, 8Plus, XR, XS), Blackberry (Evolve X, Evolve, Priv, Q20, Z30), and the Samsung Galaxy (S10, S10+, S10E, Note 9, etc). Newer models will also have a built-in wireless charging functionality, as they become available.
If your smartphone is an older model that doesn’t support built-in wireless charging, you’ll need a wireless adapter or receiver. You can plug it into the Lightning/Micro USB port of your smartphone before you place the device on your wireless charging pad.
What Makes Laird Wireless Charging Coils Stand Out?
Unlike competitors that typically only focus on the coil, Laird Performance Materials does a lot more.
Laird Performance Materials offers complete and reliable solutions to customers, including thermal interface material solutions and EMI shielding. The additional features we offer help customers reduce the total cost ownership and launch new products quickly.
Our engineers understand how poor communication between devices or an accumulation and ultimate overload of energy within a device's internal battery can decrease the efficiency of wireless charging technology. That’s why we have developed exceptionally effective, reliable wireless charging coils using carefully selected ferrite materials.
The high Q factor of our coils creates maximum wireless power charging efficiency while reducing electromagnetic interference – all within the strict size restrictions of electronics applications. Whether you need wireless charging coils for automotive applications, 5G devices, wearables, medical devices, or other applications, we ensure that our ferrite material and the coil module design are compliant with WPC’s Qi specification.
We can also integrate multifunctional materials into a single design to achieve high quality, reliability, and performance. That’s why our wireless charging coils are approved by automotive standard AECQ-200 (reliability specification) and extensively selected by strategic automotive partners.
Laird also offers innovative and differentiated connecting features to make customer installation on PCBA more easily, more reliably and more environmental friendly, reduce customer assembly fails and improve reliability.
Laird Performance Materials power transmitter design provides up to 15 W, and even higher power designs are available upon request. Get in touch to learn more about our wireless charging coils.