Every day, various companies introduce wireless charging technology into the market. And, as those products get bought up, excitement grows as the general public gets ready to “cut the cord” and try out these new products. Within the next twelve months, the market will stretch their legs, and their charging distances, offering even more options that will allow devices to be charged at an even greater distance.
The meaning of the word ‘connected’ has undergone a major change in the past year alone, with physical connections no longer being in vogue and wireless solutions taking their place.
Wireless power industry from a nascent stage and with the current acceptance of this technology by major OEMs, this industry is expected to explode in the next 18 months with wireless charging enabled products.
Charge anything, anytime, anywhere
All electronic devices are united by the necessity to be charged. Currently, wireless charging is mainly used to recharge smartphones, a market that Samsung and Apple have already begun to explore and consolidate. This is validated by industry data that states that 55% of the wireless charging market share was accounted for by consumer applications.
In addition to this, wireless charging products still function as accessories that are subsidiaries to smartphones rather than being separate products by themselves. Research has identified certain major areas where users require their phones to be charged: at home, at their work desk, at restaurants and while travelling. By pinpointing prime charging environments, companies will now be able to streamline wireless charging technology and allow a more user-friendly experience.
The coming year will also see the expansion of the charging ambit to include a variety of other devices, thereby making the technology more accessible and easier to integrate into everyday life. This integration will be supported by the evolution of wireless charging products from being mere accessories to lifestyle products in themselves, thus creating a defined space for the technology.
Today there are two established wireless charging technologies, inductive and resonant. Resonant wireless charging uses two coils tuned to resonate at the same frequency. The oscillating current generated by the primary current—in a charging pad, for example—creates an oscillating magnetic field which induces an alternating current in the secondary coil, housed in the device to be charged. Inductive charging is also based on two coils, but the transmitter and receiver are tuned to slightly different frequencies. Again, the alternating magnetic field generated by the transmitter coil is converted to electrical current by the receiver.
Both technologies have their advantages and drawbacks. Inductive charging is markedly more efficient, but the transmitter and receiver have to be more precisely aligned for charging to take place and range is limited to between 2 and 10mm. Resonant charging is much more flexible. Charging can occur over a significantly wider field up to 50mm, which enables charging through surfaces, for example. Resonant wireless charging also offers the capability to charge multiple devices simultaneously. While inductive charging’s power capability maxes out at around 5W, resonant charging power output is much higher, around 30W, which means the user could charge, for example, a smartphone, wireless mouse, tablet, or GPS watch simultaneously.
The technologies are complementary rather than competitive. The choice depends primarily on the application. The AirFuel Alliance, a wireless charging standards promoting body, supports both techniques. Nordic Semiconductor is a member of the alliance.
The primary goal in any wireless power design is to guarantee delivery of the required power under worst-case power transfer conditions. However, it is equally important to avoid thermal and electrical overstress in the receiver during best-case conditions. This is especially important when output power requirements are low. For example, when the battery is fully charged or nearly fully charged and the coils are near each other. In such scenarios, available power from the wireless system is high, but demanded power is low. This excess power typically leads to high rectified voltages or a need to dissipate the excess power as heat.
There are several ways to deal with excess power capacity when the demanded receiver power is low. The rectified voltage can be clamped with a power zener diode or transient voltage suppressor. However, this solution is typically large and generates considerable heat. The transmitter power can be reduced, but this will either limit the available received power or it will reduce the transmit distance. It is also possible to communicate received power back to the transmitter and adjust transmit power accordingly. This is the technique used by wireless power standards such as the Wireless Power Consortium Qi standard. However, it is also possible to solve this issue in a compact and efficient manner without resorting to complicated digital communication techniques. Communications techniques that communicate via small variations in the transmitted power level require a minimum amount of power transmission and may not work for systems with variable transmit distances.
What is wireless charging?
Wireless charging uses electromagnetic induction wherein power is transmitted to the receiving device without the need for physical cables. As complicated as it may sound, the functioning is pretty simple. You just place your smartphone on the charging mat and the device starts charging. For devices like smartphones and wearables, the Qi standard of wireless charging is used.
Wireless charging market
Tony Armstrong, Marketing Director, Power Products, Analog Devices Inc.
Lots of products use a battery as their primary power source. However, there are plenty of less glamorous products that serve equally deserving applications that also use batteries. Commonplace examples include: portable medical devices, industrial sensors and even rotating or moving equipment. However, unlike the benign consumer environment, these applications have more stringent requirements, such as the need for sterilization and even the potentially explosive surroundings like those commonly found in oil refineries and chemical processing facilities.
In many of these applications, a connector for charging purposes is difficult or impossible to use. For example, some products require sealed enclosures to protect sensitive electronics from harsh environments. Other products may simply be too small to include a connector, and in products where the battery-powered application includes movement or rotation, then it is virtually impossible to have charging with wires.
As a result, wireless charging is being adopted as an alternative method for charging batteries since this type of solution adds value, reliability and robustness in these applications where connectors cannot.
Of course, wireless charging has be commonly used in many handheld products for many years. These include cell phones, portable GPS systems and even hearing aids. On a larger scale, wireless charging has been adopted by the automotive industry for the charging of large banks of batteries commonly used in all-electric and/or hybrid-electric vehicles. A good example of this is BMW’s inductive wireless charging system for its BMWi8 automobile.
Sebastien Mackaie-Blanchi, FAE & Customer Engineering Manager – APAC, Nordic Semiconductor
The interest in wireless charging is largely being driven by consumers, and specifically by demand for an easy, convenient, and wireless way to keep electronic devices readily powered. With smartphones, laptops, tablets, smartwatches, and other wearables increasingly essential to both our personal and working lives, the need for an effective and efficient charging solution for these devices is apparent.
The AirFuel Alliance recently conducted a consumer survey which found 71 percent of consumers wanted wireless charging in their next device, with smartphones, tablets, and laptops predictably being cited as the most important devices requiring a wireless charging solution. And, according to the survey, consumers are prepared to pay for it too. Given this, consumer electronics will almost certainly dominate the push to develop wireless charging applications in the short term. However, the technology is making inroads in healthcare, automotive, and manufacturing industries because it offers the promise of Internet of Things (IoT) devices receiving power when remote from a charger.
Why it’s still a niche?
The current wireless charging technology still has drawbacks and limitations. For instance, the wireless charging mats don’t provide the maximum power of 15W. Although eliminating the need of cables, wireless charging is still not efficient enough. The latest iPhone series started with wireless charging speeds of up to 5W and later increased to 7.5W. As fancy and exciting this technology may sound, the output is still mediocre.
OnePlus’ Pete Lau made a fair point while announcing that the OnePlus 5T will not have wireless charging. Lau mentions the limitations of not being able to use your device when charging, and not receiving the maximum theoretical power of 15W either.
While smartphone makers struggle to improve wireless charging, there is a growing culture for achieving “true” wireless technology. Over the years, people have been working on devices which can transmit energy to multiple other devices at the same time without the need of a power mat.
Here’s a look at some of the tech firms driving the next generation of wireless charging.
Ossia’s Cota wireless charging
Ossia’s Cota wireless technology uses radio frequency to transfer energy and charge devices similar to how Wi-Fi connectivity works. This platform requires a Cota transmitter which first receives signals and sends power back through the same path. A small silicon chip which acts as a Cota receiver is built into the product and sends a beacon signal to receive power. You can manage and control “mobility, visibility, and flexibility” through Cota Cloud.
Energous’ WattUp wireless charging transmitter
Energous’ WattUp wireless charging transmitter works similarly using radio frequencies to charge devices up to a distance of 15 feet. WattUp, however, comes with energy-saving optimizations as it will only charge devices lacking power.
WattUp transmitters can also adjust the amount of charge needed for each device. In the month of January 2018, the FCC certified the WattUp Mid Field transimtter which can charge devices up to 3 feet. This makes it the first commercial true wirless charging device.
WiTricity takes wireless charging to another level as it is integrated for electric and autonomous vehicles. Electric vehicles are charged through gigantic cables which are indeed a hassle and an inconvenience as well.
WiTricity’s technology can wirelessly charge your vehicle by parking it just above a resonator on the ground which uses magnetic field to transfer energy. WiTricty hopes to increase the adoption of electric vehicles by making its most crucial point of power through wireless charging.
Pi wireless charger for smartphones
The next best thing to wireless charging mats would be the Pi wireless charger. Shaped as a cone, the Pi wireless charger changes “the angle of a magnetic field to perfectly match the angle of your device”. Pi can charge up to four or more devices at once giving up to 10W of power per device.
Pi is capable with iPhones and Samsung’s Galaxy smartphones fitted with a magnetic charging case, TechCrunch reports. However, smartphones with a wireless charging compatible body do not require the case.
Wireless charging solutions
Designing the wireless charging products using discrete components is tricky and requires considerable experimentation so it’s not for designers with limited experience and tight time constraints. However, that doesn’t exclude the novice from developing wireless charging products. The key to success is to base the design around one of several chipsets which integrate much of the control and compensation functionality demanded by a wireless charging system into a single chip.
Growing semiconductor industry is one of the major driving factor of this market. The global semiconductor industry is estimated to be at market size of more than USD 400 billion in the year 2017 and this is one of the major factor which is supporting the market of wireless charging. Semiconductor industry is very wide and consist thousands of products. Components which are essential for wireless charging receivers or transmitters are manufactured and developed by companies who are playing major role in the semiconductor industry. High development and high investment in R&D for the new product development is leading to the growth of both, Wireless Charging Market as well as overall semiconductor industry.
Companies such as Qualcomm, Samsung, Texas Instruments who are driving the industry growth of semiconductor are working in advanced environment for the development of wireless charging solutions.
Tony Armstrong, Marketing Director, Power Products, Analog Devices Inc.
A recent product introduction to expand our offerings in the wireless battery charging arena is our LTC4123. The LTC4123 combines a 30mW wireless receiver with a constant-current/constant-voltage linear charger for NiMH batteries, such as Varta’s power one ACCU plus series. An external resonant LC tank connected to the LTC4123 enables the IC to receive power wirelessly from an alternating magnetic field generated by a transmit coil. Integrated power management circuitry converts the coupled AC current into the DC current required to charge the battery.
Wireless charging with the LTC4123 allows for a completely sealed product and eliminates the need to constantly replace primary batteries. Zn-Air (Zinc-Air) detection allows applications to work interchangeably with both rechargeable NiMH batteries and primary Zn-Air batteries with the same application circuit. Both battery types can directly power a hearing aid ASIC without the need for additional voltage conversion. By contrast, a 3.7V Li-Ion battery requires a step-down regulator in addition to the LTC4123’s functionality to power the ASIC. The LTC4123 rectifies AC power from the receive coil, and can also accept a 2.2V to 5V input to power a full-featured constant-current/constant-voltage battery charger.
Features of the charger include programmable charge current up to 25mA, a single-cell 1.5V battery charge voltage with ±0.5% accuracy, charge status indication and an onboard safety charge termination timer. A temperature-compensated charge voltage protects the NiMH battery and prevents overcharging. The LTC4123 prevents charging when batteries are inserted with reverse polarity and pauses charging if the temperature becomes too hot or too cold. The LTC4123 is housed in a highly compact, low profile (0.75mm) 6-pin 2mm x 2mm DFN package with backside metal pad for excellent thermal performance.
Sebastien Mackaie-Blanchi, FAE & Customer Engineering Manager – APAC, Nordic Semiconductor
Nordic Semiconductor specialises in RF technology, including Bluetooth Low Energy (Bluetooth LE) wireless solutions. Its involvement in wireless charging systems is therefore limited to bringing wireless connectivity to wireless charging systems. For example, power transmitting units (PTU) in resonant wireless charging systems are equipped with Bluetooth LE wireless connectivity to periodically check if a device is present, what that device is, what its power requirements are, and if it needs charging. The bidirectional wireless link between the transmitter and receiver coils allows the PTU to ‘advertise’ for a power receiving unit (PRU), such as a smartphone or tablet. When detected, the PTU communicates the with the PRU over the Bluetooth LE wireless link. In this way, the PTU engages the charging sequence, and determines how much charge is required. Bluetooth LE wireless connectivity also controls the charge. The PRU can signal when, for example, it is 80 percent charged, allowing the remainder of the charge to be scaled down to avoid overcharging, which is critical considering the dangers of overcharging the fragile Lithium-ion batteries at the heart of today’s consumer electronics devices.
Nordic Semiconductor, for example, offers the nRF5 Software Development Kit (SDK) for AirFuel wireless technology product developers. The SDK can be used with both Nordic’s nRF51 and nRF52 Series Bluetooth LE SoCs and supports the development of AirFuel Alliance-compliant wireless charging applications for both charging pads that supply the wireless power, and for personal devices where wireless charging can eliminate the USB cable.
The SDK has examples for both sides of an AirFuel application – PTUs and PRUs. Nordic’s S132 SoftDevice, an RF software protocol stack for building advanced Bluetooth LE applications, supports Central, Peripheral, Broadcaster and Observer Bluetooth LE roles, and supports up to twenty connections and concurrent role operation. For AirFuel Alliance-compliant wireless charging applications, this enables a PTU to independently supervise up to twenty charging devices.
STMicroelectronics is powering up wireless charging for mobile devices by introducing one of the world’s first chips to support the latest industry standard for faster charging.
One of the market’s first wireless-charging controllers to support Qi Extended Power, ST’s STWBC-EP combines best-in-class energy efficiency, consuming just 16mW in standby and able to wirelessly transfer more than 80% of the total input power, with unique features created by ST to enhance the user experience. These include a patented solution enhancing active presence detection to wake the system quickly when a compatible object is presented for charging. The patented technology also enhances the performance of Foreign Object Detection (FOD), to cut power and prevent overheating if objects containing metals are brought too close to the charger. Other unique innovations enhance power control and energy transfer to maximize efficiency and ease of use.
The STWBC-EP provides the level of integration allowing to simplify charger design while providing the flexibility to work with supply voltages ranging from 5V USB power up to 12V.
To help accelerate time to market for product developers, ST has created an associated reference design with a Qi 15W ready-built transmitter board and documentation to get started. ST also has a 15W receiver chip (STWLC33) for use in high-speed chargeable devices, which developers can use to complete their applications.
Infineon is offering wireless charging for smartphones, wearables, medical and industrial devices with its AURIX and XMC microcontrollers including software IP and reference designs for both inductive and resonant wireless charging solutions in cars, at home or in public places.
It supports the current 15 W charging standards, including fast charge smartphones, and can support future changes through a software update.
An enhanced power stage architecture improves Electro Magnetic Interference (EMI) performance 10-15 dB over existing solutions on the market
A supplemental Foreign Object Detection system provides enhanced detection accuracy.
The scalable architecture can support everything from a fast charge smartphone, to a 20 W robot, up to a 60 W drone and beyond.
Paired with power products, like MOSFETs and Driver ICs, this system can provide full power wireless charging without complicated thermal management, often achieving charging rates equivalent to wired charging.
The XMC based 2.5 W low-power solution from Infineon is the industry’s lowest cost resonant wireless charger. It supports both one-to-one and multi-device charging on a single transmitter. By using a higher frequency, very small coils can be employed in a variety of form factors, with no regard to nearby metallic objects.