The current trend of “smartening” our devices is not dying down; nay, we find even more new areas for automation and connectivity. Smart solutions are everywhere, invading our everyday life, even our homes. In our households more and more devices are being connected to the Internet, providing real-time data about the condition of our property, enabling us to set up a well-optimized system. The overall objective is to level up our quality of life and convenience in our homes. We have devices in a continuously growing number that have constant connection to the Internet, consuming more energy due to the persistent hard work of the processor in the background. For those that are battery-powered, battery charging is essential. However, the more machines, gadgets we have, the more cables we need to connect them to the grid. Or not? With wireless charging you can easily get rid of tangled charging cables that have become a real issue in our life in the past couple of years.

In this article we will provide an overview of wireless charging solutions. We give a special attention to the two wireless charging technologies, their most common design criteria and the benefits they offer compered to wired technology.

Energy efficiency, shorter charging time and higher power density have been on the agenda for engineers for a while and significant improvement has been made in recent years. The overall wireless charging market is growing at a rapid pace. It is expected to have a CAGR (compound annual growth rate) of more than 25 percent for receiver and transmitter during the period 2018-2023. The various benefits like convenience, integration with multiple devices, mobility and flexibility drive the market. Meanwhile, the technology is moving from transmitters that charge single devices to transmitters that can charge several devices simultaneously. Current solutions rely on either inductive or resonant power transfer. Infineon’s array of wireless charging solutions range from low-power support, using very small coils and multi-device charging, to a flexible high-power offering that is backward compatible for lower-power products such as smartphones.

Wireless charging pays off in comfort

Smart home denotes the use of technical systems, automated processes and connected, remote-controlled devices in apartments and houses. The main objective of the functions is to improve the quality of life and convenience in the home. Other goals are greater security and more efficient use of energy thanks to connected, remote-controllable devices. Therefore, wireless charging is not just about charging phones. As people mostly charge at home, there is a plenty of devices that can utilize wireless power transfer technology, so you can easily eliminate the cable jungle in your living space.

But of course, it is about more than making your home beautiful. It is for your comfort and flexibility to charge anywhere and everywhere. You can charge your service robot (e.g., vacuum cleaner or lawn mower), laptops, desk phones, drones, security cameras, portable Bluetooth speakers, kitchen appliances, wearables, headphones, gaming controllers, chargers integrated into lamps or furniture, power tools - the list is almost endless. Wireless charging removes the need for grid connection, thus eliminating plug compatibility issues, damaged cables with a risk of electric shock. As the devices can also be powered through their surface, there is no need of drilling holes into them, which makes them hermetically sealed enabling a higher level of safety.

Innovative and cost-effective wireless charging designs

Achieving high efficiency, a superior user experience, and safety - all at the same time - requires a deep level of system knowledge and expertise as well as the use of excellent components. The designer must understand antennas and interaction with surrounding structures, and how to implement precise control of power delivery. In the inductive, the main challenges are FOD (foreign object detection), stable in-band communication and authentication to protect the Qi ecosystem from non-certified and potentially dangerous solutions. FOD needs reliable components and enhanced methods to provide a good and safe user experience. Quality components also play a key role in stable in-band communication. Resonant is all about capacitances and advanced FET technology (silicon MOSFET and GaN eMode HEMTs). To master the efficiency challenge, high performance driver ICs play an important role.

Infineon helps designers to master all these challenges and develops dedicated reference designs, for both technologies, which support many of the current and next-generation wireless charging applications for consumer, industrial and automotive sectors (e.g., in-cabin smartphone charging). These reference designs include the hardware design, bill of materials, example PCB layout and all the documentation required to integrate wireless charging into the end products. The transmitter architecture is software-based, which can be updated as standards evolve or new products are introduced to the market. The flexible transmitter architecture supports standard or custom coils, either in single-coil or multi-coil applications. For selected applications, Infineon offers also receiver solutions, and has a broad variety of semiconductors for the power supply unit. With these new designs and supreme components, Infineon meets and exceeds even the most rigorous design expectations.

Infineon wireless-charging

(Source: Infineon Technologies)

Flexible software-based architecture

Rather than rely on an application specific IC for protocol and power delivery, the strength of the Infineon wireless charging solution lies in its modular software-based architecture. Wireless charging is continually evolving, as standards mature, and new products and applications are introduced to the market. The high software content of the solution allows a common hardware architecture to be used across several reference designs, with each reference design flexible enough to support several types of applications. In addition, future changes to the wireless charging standards can be supported by a software upgrade, which creates a future-proof product design that can span multiple generations.

The software is responsible for directing all major wireless charging functions in the system. A fully digital demodulation scheme provides greater sensitivity for decoding communication in times of weak coil coupling due to misalignment, and also ensures the highest level of interoperability with legacy receivers. Next-generation parameter measurement techniques ensure the highest accuracy for optimal power delivery and FOD. Precise control of frequency, duty cycle and voltage provides the correct level of rectified power at the receiver. In some systems, two-way communication enables smart charging with two-way authentication. Underneath the higher-level functions, a real-time engine keeps track of every aspect of the transmitter operation from input supply, trough efficiency, to thermal performance, and makes adjustments as required. Finally, a self-calibration step during initial transmitter power-up provides a predictable baseline performance ensuring each product meets the requirements of the application.

Efficient and easy-to-use wireless charging for smartphones, wearables, medical and industrial devices is supported by the XMC™ microcontroller families. For automotive qualified solutions, such as charging your smartphone in your car, the AURIX™ is the perfect product to choose. Flexible chip sets for high performance, including software IP for smart and safe wireless charging applications, are available. Working with a systems solution partner, Infineon provides reference designs for both inductive and resonant wireless charging solutions: for on-the-go charging - in the car, at home or in public places.

Infineon’s wireless power controller based on the ARM® Cortex®-M0 core, works seamlessly with Infineon’s power devices in a scalable and cost-effective architecture to provide a complete charging solution for everything ranging from a fastcharge smartphone, through a 20 W robot, to a 60 W drone and beyond. Paired with related power products, like MOSFETs and driver ICs, this system can provide full wireless power without complicated thermal management, often achieving charging rates equivalent to wired charging. Complete solutions support future changes with a software update. Enhanced power stage architecture improves EMI performance 10-15 dB over existing solutions on the market. A newly developed supplemental FOD system provides enhanced detection accuracy to meet critical manufacturer safety requirements. Infineon’s microcontrollers provide a powerful and cost-effective platform.

Summary

The market for wireless charging will grow quite strong in the next years. Independent from the preferred technology (inductive or resonant), there are several key design requirements to be considered. Modern engineering designs stress how important it is to have efficient and easy-to-use transmitter solutions.

Engineers also have their arrow-eye on smart heat management that keeps the surface and transmitter at a comfortable temperature, and avoids heating the battery of the device that is being charged. A small footprint is highly valued, especially for devices that are small in size like wearables. Fitting designs with a high power rating results in faster charging speed for end users’ convenience.

Take a look at Infineon’s supreme portfolio of wireless power offerings and solutions, visit www.infineon.com/wirelesscharging