The rapidly evolving wireless charging market is urging manufacturers and developers to develop globally uniform wireless charging standards for interoperability between devices.
The race to build a global wireless charging technology is in full swing. New exciting wireless charging technology advances and products are emerging – some companies focus on one technology and others support multiple technologies. But the lack of interoperability between technologies is still a big problem because there is no uniform wireless charging standard.
The idea of ​​wireless power transmission has been around for many years. As early as the 1900s, Nikola Tesla began to try wireless power, but has not been completely successful. But he is very close to success - his revolutionary invention is called the Tesla coil. This system that uses no wires to transfer electrical energy has completely changed the way electricity is used (Figure 1).
Figure 1: The Tesla coil was invented by Nikola Tesla in the 1900s.
There are many techniques and methods for achieving power transmission without wires in a short distance, such as electromagnetic induction, magnetic resonance, capacitive coupling, magnetic coupling, and the like. The first two should be the most commonly used technologies on the market today.
Electromagnetic induction (inductive coupling)
This near field method uses a magnetic field established between the coils of the wires to effect wireless transmission of electrical energy. When a current flows through the transmitting coil, it generates a magnetic field that induces a voltage in the receiving coil.
The better the coil is coupled, the better the power transfer. The coupling factor k indicates the degree of coupling. The value of k depends on various factors such as the shape of the coil, the angle between them, and the distance between the inductors.
Depending on the distance between the transmitter coil and the receiver coil, such a system can be divided into loose or tight coupling.
In a tight coupling system, the transmitting coil and the receiving coil have the same diameter. They are aligned with each other, the smallest Z apart. This distance Z is much smaller than the coil diameter. This system has less heat and higher efficiency (Figure 2).
Figure 2: This is a tight coupling system with the same diameter of the transceiver coil.
The coils in the loosely coupled system can have a large distance, but the power transmission efficiency is low and the electromagnetic radiation is high (Fig. 3).
Figure 3: In a loosely coupled system, the distance between the coils is large.
Electromagnetic induction has many advantages, such as simple circuit scheme and good cost-effectiveness. The main drawbacks include limited charging distance and precise alignment between the transmitter and receiver.
Magnetic resonance (resonance inductive coupling)
This near-field method uses the resonance phenomenon to wirelessly transmit electrical energy in a certain space, and the principle is the same as that of electromagnetic induction. The transmitter and receiver coils oscillate (or resonate) at the same frequency, depending on the material and shape of the coil (Figure 4).
Figure 4: Lighting the bulb through the magnetic resonance coil.
The main advantage of magnetic resonance is the ability to transmit electrical energy over a relatively long distance, and the transmitter and receiver do not require precise alignment. However, due to the complicated circuit control, the production cost is high.
Popular products
Most of the products currently on the market rely on magnetic induction and magnetic resonance wireless charging technology. These products include:
â— Qi: Qi is created by the Wireless Charging Alliance (WPC) to charge or power a range of devices, from smartphones to cordless kitchen appliances. It combines sensing technology and resonance technology. Figure 5 shows one of the many products that support the Qi standard.
• Powerby Proxi: This WPC member provides resonant wireless solutions in many battery-powered devices, but design constraints limit their performance. They offer a variety of product solutions for industrial sites. For example, the Proxi-Point wireless connector provides power to sensors in hard-to-reach locations and charges the battery (Figure 6).
Figure 5: This is a wireless Qi charging dock developed by Samsung.
Figure 6: This Proxi-Point wireless connector is primarily designed to provide power to hard-to-reach sensors.
â— WiPower: Qualcomm is both a wireless charging alliance and a member of the Airfuel Alliance. The company's WiPower technology is based on the principle of magnetic resonance. WiPower recently announced that it can wirelessly charge devices with metal casings.
â— WiTricity: This magnetic resonance-based technology is designed for devices ranging from one centimeter to several meters. Original equipment manufacturers (OEMs) can embed this technology directly into their products and systems (Figure 7). WiTricity is an active member of the Airfuel Alliance.
â— Powermat: This is a technology based on electromagnetic induction that includes a mat that charges the electronic device. This technology is certified by the Power Matters Alliance. These devices with built-in wireless charging can be powered up immediately at the charging point. If the device is not activated, it can be wirelessly activated with the plug-in Powermat Ring (Figure 8).
Figure 7: Witricity's Prodigy can simultaneously charge two devices wirelessly with one power supply.
Figure 8: Can this Samsung device use Pow? The ermat Ring is charged by the Powermat.
When you look at these popular products, you can clearly see that magnetic resonance and electromagnetic induction are the main players from a technical point of view. Which technology to choose depends on the specific application.
Wireless charging is an emerging market that is still evolving. With the emergence of more technologies and products, consumers are expected to see interoperable products everywhere in the market.
Main player
There are two key organizations in the field of developing magnetic resonance and electromagnetic induction technologies, namely the Wireless Power Alliance (WPC) and the Airfuel Alliance. Founded in 2008, WPC is the founder of the Qi standard.
Members of the WPC Alliance have been working to develop a globally unified standard for wireless charging technology. More than 800 products from more than 200 companies currently support the Qi standard. Alliance management members include LG, Qualcomm, Samsung, TI, Toshiba and Verizon.
The Airfuel Alliance is a global ecosystem and the result of the recent merger of the PMA Alliance and the Alliance for Wireless Power (June 2015). The companies that make up the alliance board are AT&T, Intel, ON Semiconductor, Powermat, Samsung and WiTricity.
It is worth mentioning that the PMA Alliance is a global non-profit industry organization dedicated to building paradigms for wireless power technology. Its founding member is Powermat. Similarly, the A4WP Alliance is an independently operated, non-profit organization dedicated to building a global wireless charging ecosystem based on Rezence technology.
Unfortunately, this standard battle does not create any functionality, interoperability or flexibility for the WPC Alliance and the Airfuel Alliance. Some of the big companies in the manufacturing industry, such as Microsoft, Qualcomm and Samsung, are also members of the WPC and Airfuel alliances. Therefore, their products support both wireless charging standards.
Semtech is another company with dual membership. Last October, Semtech released a new wireless charging platform that supports all major standards (Qi, PMA and A4WP Rezence). The TS80K platform, which includes the TS80000 transmitter and TS81000 receiver, supports a variety of system configurations for wearable, mobile and embedded system applications (Figure 9).
Figure 9: Semtech's three-mode wireless charging platform includes the TS80K transmitter and the TS81K receiver.
The TS80K offers greater flexibility as it supports all major (both transmitter and receiver applications) wireless charging standards with multimode technology. It is also possible to quickly support new wireless charging standards with appropriate modifications. The TS80K platform supports a wide range of power supply solutions, from 100mW wearable solutions to 100W solutions for industrial processing equipment, medical equipment and "networked" furniture equipment.
The TS80K's multi-mode transmitter solution outputs power levels ranging from 100mW to over 40W. It enables embedded charging in furniture, cars and public venues to support all major wireless standards on a single, easy-to-use and cost-effective platform.
The lack of uniform standards between the WPC Alliance and the Airfuel Alliance makes it very slow for vendors to adopt these technologies in their products. Once the winners are identified in this wireless standards battle, the market will soon form a multi-billion dollar general wireless charger business. Ultimate consumers will be able to make informed choices from a wide range of products.
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