You place your phone on your bedside table, and it automatically starts charging. You place your hand-blender on the kitchen counter-top and it charges itself. You walk into a coffee shop or airport lobby, and your phones and tablets get a full power boost even as you recharge your-self with a coffee. That would really feel good, right? Well, such visions of ‘wireless charging’ are no longer a fantasy. Inductive charging or wireless charging technology is gradually stabilising, and gaining popularity.

Silicon designers and manufacturers, including IDT, Texas Instruments, Freescale Semiconductor and Intel, are focusing on wireless charging chips (transceivers and receivers).

The latest mobile phones, such as the Nokia Lumia 920 and Samsung Galaxy S4, are capable of wireless charging. There are wireless charging sleeves for the iPhone and other devices, and there are dozens of wireless chargers (charging pads) available in the market from Duracell, Energizer, etc, including those from JBL and Panasonic that double up as music players or alarm clocks. Food chains like Starbucks and McDonald’s are piloting wireless charging services at their outlets, while building material manufacturers like DuPont are thinking on the lines of embedding wireless charging chips into kitchen countertops. Car manufacturers are incorporating in-car wireless charging for mobile phones, and technologies like Qualcomm Halo promise wireless charging of electric vehicles.

On top of that, there are also signs of emerging standards. The Wireless Power Consortium (WPC) has a significant head start in this race. It has already standardised Qi, but seems to be in for serious competition as the Power Matters Alliance (PMA) and the Alliance for Wireless Power garner increasing support and work towards standardising their specifications too.

Wireless charging in action
Wireless charging in action

Here is a quick round-up of the major players, and some of the recent developments in the wireless charging space, which go to show the fast-paced developments in this area.

Qi vs Power 2.0
Power 2.0 emerging as a notable rival to Qi is perhaps the hottest topic in the wireless charging space today!

The Powermat charging mat was one of the earliest in the wireless charging space, having been launched as early as 2009. Although one of the key players in the standardisation of the Qi format, Powermat backed out from the WPC, frustrated by what it thought was a slow rate of adoption of Qi. Thereafter, Powermat, along with Procter and Gamble (P&G), founded the PMA to garner support for, and standardise a wireless charging specification (dubbe Power 2.0) based on the Powermat. Since then, Qi and Power 2.0 have become the two most aggressive competitors in the wireless charging space.


The basis of wireless charging
“Wireless charging, as the name suggests, charges the batteries of smartphones and other portable devices wirelessly. One does not need to connect any wire to the power socket and charge the device. The user can simply place a phone with wireless charging capability on a charging pad for it to recharge,” says Ravi Lakkundi, product manager, Harman India.
Wireless charging or inductive charging is based on the fundamental principles of electromagnetic coupling. This requires two coils: a transmitter (which typically resides in a charging pad or mat) and a receiver (which resides in the device or its charging sleeve). It works by passing a current through a transmitter coil to generate a magnetic field, which creates electric current in a similarly-sized and oriented receiver coil in the other device. The generated current is used to charge the device’s battery or run it directly. For inductive charging to work, the two coils have to be placed close to each other. Move them apart and the efficiency of energy transfer drops drastically.
A more recent technology, called resonant inductive coupling or electro-dynamic induction, promises to work even when there are greater distances between sender and receiver coils. That is, one would not have to rely on a charging mat, and can instead convert whole surfaces like tables and kitchen counter-tops, or even whole rooms and lounges, into wireless charging areas. Resonant inductive coupling involves the near-field wireless transmission of electrical energy between two coils that are tuned to resonate at the same frequency.
Technically, the key difference between these two methods is the coupling factor between the transmitting and the receiving coil. A high coupling factor means that both coils need to be in close proximity with good alignment. A lower coupling factor enables a wider distance and spatial freedom in receiver placement with respect to the transmitter.

WPC’s Qi specification enables any Qi-certified device to charge on any Qi-based charging pad. The Qi standard specifies transmitter topologies and ensures backward compatibility with existing WPC receiver products. The transmitters can use one or several coils (individually or simultaneously) to generate the magnetic field. The initial transmitter topologies use close magnetic induction coupling, and rely on using between three and eight coils to enable X and Y spatial freedom. The Z distance between the transmitter and the receiver coil is typically 5 mm. Lately, the WPC has proposed a new transmitter type with 5cm Z spatial freedom using adaptive resonant magnetic principles, while maintaining backward compatibility with existing WPC induction-coupled receivers. Hence, Qi now supports both inductive and resonant charging, spatial freedom, and intelligent power management.

Qi is an open, fully-fexible standard capable of evolving its technology and features. It is backed by several leading industry players including Nokia, HTC, Samsung, Energizer, Panasonic and Sony. The Nokia Lumia 920 and Samsung Galaxy S4 are amongst the popular mobile phone models using Qi wireless charging technology. Nokia, Samsung, Energizer and others provide Qi-compatible charging pads to charge Qi-compatible devices. JBL PowerUp is one such interesting product, which doubles up as a speaker-cum-wireless mobile phone charger. “JBL PowerUp is a speaker that has a wireless charging pad built-in. You can simply rest the phone on the JBL PowerUp rubber roundel and the phone starts charging,” says Lakkundi. “The wireless charging standard, known as the Qi charging/inductive power standard, works on magnetic induction between two coils. There is a base station (JBL PowerUp) to provide inductive power and the mobile device that consumes power. The current technology helps to transfer/charge low-power devices up to 5W.”

Speaking in detail about the power ranges covered by Qi, Abhishek Kumar, business development manager, Power Management Products, Texas Instruments (India), explains, “The focus for the lower power range is up to 5W and for the medium power range is up to 15W. Some examples of low-power products are applications using a single-cell battery, mobile phones, digital cameras, toys, Bluetooth headsets, audio headsets, alarm clocks, etc. Examples of mid-power products include tablets, ultra books, high-end smartphones, two-way radios, toys, industrial and medical equipment like barcode scanners, POS systems, health monitors, etc. Apart from this, Qi is also working on kitchen appliances and is defining specifications for devices like blenders, cooktops, coffee makers and others, that can be powered wirelessly.” TI offers multi-mode wireless charging chips that support Qi as well as PMA specs.

Powermat’s technology (which is the basis of the PMA’s specifictions) is also quite similar to Qi. It, too, works using tightly-coupled inductive charging, but the main difference is that it works on the 277-357kHz band, while WPC’s Qi works on the 100-205kHz band. The PMA provides a comprehensive suite of standards and protocols covering inductive power technology, resonant power technology (in progress), digital transceiver communication, cloud-based power management services and environmental sustainability. The specifiations are available on the consortium’s website.

One stark difference between Qi and Powermat is that, while one is backed mainly by manufacturers, the other is backed mainly by users. This is evident by the fact that the most influential board members of PMA include P&G, AT&T Mobility, Starbucks and Powermat. Powerkiss, an earlier Qi ally, has also now joined forces with the PMA, bringing with it large clients like McDonalds and The Coffee Bean and Tea Leaf. Delta Airlines’ lobbies, the revamped Barclays’ Centre, New York City’s Madison Square Garden, and Starbucks outlets are some of the places where one can experience PMA charging technology first-hand.General Motors has also chosen PMA’s technology for in-car wireless charging for its future models. DuPont Building Innovation has partnered with the PMA to embed wireless charging solutions underneath everyday surfaces like kitchen countertops, tables and desks. In short, the PMA is trying to become ubiquitous by wooing the users rather than the sellers of technology.


Key technologies
• Wireless Power Consortium’s Qi
• Power Matters Alliance’s Power 2.0
• Alliance for Wireless Power A4WP specifications (based on Qualcomm’s WiPower)
• WiTricity (which will be incorporated into Power 2.0)

Another key reason why PMA is seen as giving Qi a run for its money is its focus on ‘intelligence’ and improving the user experience with cloud-based services. In February this year, for example, Duracell Powermat demonstrated wireless power surfaces that operate as a mesh network, allowing wireless charging spots across the globe to be centrally-monitored and managed. This new network topography is ideal for use in public places such as coffee shops, airports and arenas, enabling those who manage venues to monitor, upgrade and set policies for each wireless charging spot from a centralised cloud-based system. This transforms wireless power in public places from disjointed, standalone surfaces into a smart global network, allowing the implementation of new services and business models. For example, there could be apps that find the neares available wireless charging spot; service providers could control who can use their wireless power, for how long and on what terms; enterprises can monitor usage patterns, assess the health of their wireless power network and administer support and upgrades remotely, etc.

A4WP promises spatial freedom
One of the other notable contenders in this standards race is the A4WP, a consortium backed by Qualcomm and Samsung, amongst others. The focus of this group is to advance spatial freedom in wireless power. And so, the specifications they put out will take a different approach to wireless charging. The A4WP specification uses magnetic resonance to charge a device in close proximity (up to around 3.8 cm or 1.5 inches away). Thus, a tablet or smartphone can be charged when placed next to a laptop that sports resonance charging capabilities, without having to be placed directly on a charging platform.

According to an explanation by the president of A4WP in a media interview, “The specification is based on non-radiative, near-field magnetic resonance, or loosely-coupled wireless power transfer, defined in a CEA-published glossary of terms as resonant wireless transfer of power through magnetic induction between coil(s) where the coupling factor (k) can be less than 0.1, though values up to 1 may also be supported, and where the system requires (coupled) magnetic resonance. What makes the technology unique is that its application demands that the designers explicitly address impedance matching between the charger and device to be charged. In contrast, in the case of classic magnetic induction, or so-called tightly-coupled solutions, there is no need for impedance matching as the charger and device to be charged are held in extremely close proximity, where even the slightest rotational or translational shift causes power transfer and effciency to drop signifcantly. Ultimately, this difference between tightly-coupled (a first-generation wireless power transfer technology) and loosely-coupled (a second-generation technology) is the improvement in user experience owing to spatial freedom.”

Consumers will like A4WP because it supports simultaneous charging of multiple devices with widely differing power requirements such as handsets, Bluetooth headsets, MP3 players, GPS devices and mobile tablets. It also delivers spatial freedom, which means that users can drop multiple devices randomly onto the charging surface without bothering to precisely position them. It will also fitwell into next-generation home healthcare and outpatient monitoring devices where, for reasons of hygiene and ergonomics, completely-sealed devices are preferred.


A look at the wireless charging product range
• Mobile phones capable of wireless charging, such as the Nokia Lumia 920, Samsung Galaxy S4, Google Nexus 4 and HTC Droid DNA
• Wireless charging sleeves for Galaxy S3, iPhone 4S, from brands like Energizer, Phillips and Duracell
• Charging pads for mobile phones, from makers like Powermat, Samsung, LG, JBL and Nokia
• Devices that double up as charging pads, such as JBL PowerUp, Oregon Scientific Bedside Alarm
• Wireless charging video cameras, e.g., the Qi-enabled Panasonic HC-V720M, Pentax WG-3 GPS
• Low-power consumer goods like electric toothbrushes (e.g., Oral-B rechargeable toothbrushes)
• Smart watches, such as the new Agent by Secret Labs
• Electric charging in vehicles like the Nissan Leaf, Chevrolet Volt and Renault Fluence using technologies like Plugless L2, Qualcomm Halo, etc
• Wireless charging kitchen counters from DuPont
• Kitchen appliances that can be wirelessly charged, such as blender and rice cooker from Haier
• Intel proposes A4WP-based laptops, tablets, etc, in the near future
• Navigation devices, such as those demonstrated by Fulton Innovation at CES 2013

For the benefit of the consumer electronics industry, the A4WP specification goes with broadly-adopted wireless technologies, such as Bluetooth LE, which will allow manufacturers to minimise hardware requirements. For industrial designers, the A4WP specification leverages a near-field magnetic resonance technology that provides more flexibility for charging applications to be installed into automobiles, furniture and other surfaces.

The A4WP specifcation also features a simpler transmitter antenna design, a simpler wireless power control system, and the ability to transfer power through non-metallic surfaces at greater distances, without the need for costly multi-coil repeaters. Besides, A4WP promises that the specification will only freeze the requirements for the transmitter and receiver, mutual coupling and mutual inductance, leaving most options open to members’ designers. Designers can specify and source their own out-of-band radios, power amplifiers, DC-to-DC converters, rectifiers and microprocessors—discrete or integrated—and assemble them as they require. As long as the components conform to the specification, they can be of any topology.

Nokia announces JBL PowerUp wireless charging speaker for Nokia Lumia
Nokia announces JBL PowerUp wireless charging speaker for Nokia Lumia

It is believed that A4WP’s specifiction is based on WiPower, Qualcomm’s wireless charging specification, which was approved by the A4WP in January. A4WP is supported by other industry leaders including Intel, IDT, TI, Broadcom, Samsung, LG, Haier, Denso, and so on.

Charge anywhere in a room with WiTricity
The PMA recently formed a technical working group to add a resonant implementation to the Power 2.0 group of specifications. WiTricity, an MIT spin-off and the exclusive patentee for MIT’s wireless energy transfer technology, was appointed vice-chair of this working group, with the immediate task of creating a specification for smartphone-ready highly-resonant wireless power. This specification, expected to be available by the end of this year, will be fully compatible with the PMA’s existing inductive wireless power specification and products.

WiTricity’s wireless charging technology tops the benefit of spatial freedom, by offering distanced wireless charging using tuned electromagnetic resonators that effciently transfer power over large distances via the magnetic near field. So, you just need to walk into a WiTricity powered location, and your devices will start charging. Although it might seem that WiTricity’s technology is similar to traditional magnetic induction, it is not. In traditional systems, the efficiency of the power exchange drops by orders of magnitude when the distance between the coils becomes larger than their sizes. As we have seen earlier in this feature, the power exchange efficiency of some induction systems is improved using resonant circuits. However, the technical literature on WiTricity’s website claims that, “…to the best of our knowledge, WiTricity’s founding technical team was the first to discover that by specially designing the magnetic resonators, one could achieve strong coupling and highly-efficient energy exchange over distances much larger than the size of the resonator coils, distances very large compared to traditional schemes.”

WiTricity’s mode of wireless power transfer can work over distances ranging from centimetres to several metres—and that too with a very high efficiency, often exceeding 90 per cent. Another interesting aspect is that WiTricity sources only transfer energy when it is needed. When a WiTricity powered device no longer needs to capture additional energy, the WiTricity power source will automatically reduce its power consumption to a power-saving state.

WiTricity’s method of energy transfer can penetrate and wrap around obstacles, as it uses magnetic near field. I is also a zero-radiation, safe method of energy transfer. WiTricity also features a scalable design that enables solutions from milli-watts to kilo-watts.

Putting the technology into your devices
So, how does all this technology translate into products? Well, we already have wireless charging phones and dozens of mats and pads. There are also wireless charging sleeves for various older phone models. Most of these wireless charging products are also smart to a certain extent—for example, they can automatically switch off power transfer once the device is fully charged.

IDTP9030/9020: IDT introduced wireless power transmitter / receiver solution
Chip industry leaders, including TI, Freescale, IDT and Intel, are getting deeply involved in wireless power, enabling OEMs to easily fit in such capabilities into their products. Multi-mode chips from TI, Freescale, IDT, etc, support WPC and PMA standards, and are promising A4WP support as well. Intel apparently favours A4WP because it extends the capabilities of wireless charging beyond mobile phones to laptops and ultra-books too.


Some of the firms providing wireless power chipsets
Texas Instruments
Toshiba Freescale Semiconductor
ON Semiconductor
NXP Semiconductor

According to Kumar from Texas Instruments, “TI’s wireless power transmitter and receiver products are used in more than 80 per cent of wireless power products released in the market. For example, currently all Nokia Lumia phones and chargers supporting wireless power are designed using TI products. Our portfolio of transceivers include innovative technologies, a broad range for all applications, comprehensive design support and reference designs, app notes, and complete solutions. It helps design engineers to develop innovative, efficient wireless charging capabilities for smartphones, tablets and other portable electronics, and design wireless power charging sources, ranging from pads to sources used in cars and furniture. Moreover, TI is an industry leader with the first WPC 1.1 ICs.

Asked about the merits of specific products, he replies, “Specifically, TI’s bq5101x integrated receivers provide a regulated DC output and digital-control feedback to the transmitter, while TI’s bq500xx family of wireless power transmitters efficiently manages the power transfer to the receiver.”

TI also offers development aids, and support to engineers working in this emerging field. Whether implementing wireless charging within an existing design or adding this functionality to a new one, engineers can make their own kit by selecting a transmitter/receiver evaluation module. TI has evaluation modules for bq500410AEVM-085, bq500211EVM-045 and bq51013EVM-725. Along with development tools, TI also provides a large selection of support collateral including technical documentation, reference designs, application expertise, customer support, and third-party and university programmes. “Our design experts on the E2E community give engineers an interactive platform to get their questions addressed. Also, as mentioned, the extensive network of third-parties consists of recommended companies, RF consultants, and independent design houses that provide a series of hardware module products and design services,” adds Kumar.

Most component makers and solution providers are betting big on the wireless charging market, and trying to include all leading technologies in their product range. “We predict rapid growth of wireless charging technology in many applications over the next five years. We’d like to expand the market shares of our coils by manufacturing solutions for all major wireless power standards, including WPC, A4WP and PMA in the near future,” says Yasunori Terajima, head of new business promotion group of the electronic components sales & marketing group at TDK Corporation, a leading provider of wireless power transfer coil units for use in smart phones and other mobile devices.

Who will win the race?
It is evident that there is a lot of work happening in this space and a lot of competition too. Apart from the standards race, there is a lot of enthusiasm in developing new products too. There are several mind-boggling technologies, including Eurobalise (a wireless charging system between trains), Duracell Powermat’s WiCC (an after-market memory card-like insert with a next-generation wireless power receiver, coupled with NFC technology), WiMat (a wireless charger for phones that takes standard USB power input) and Qualcomm Halo (for wireless electric vehicle charging).

“According to IHS, about 5 million wireless charging units were shipped in 2012, and they estimate that 100 million wireless power devices could be in use by 2015. We find that the market today is focused primarily on products for mobile phones, but is expected to include products for industrial, automotive and other consumer goods in the future,” says Kumar, adding, “One significant development that will impact the adoption of wireless charging technology is the technical standards. Currently, there are three standards consortiums—WPC, PMA and A4WP. Consensus on a universal standard is important to the development/evolution of this technology as it will drive wider adoption of wireless charging, and ensure customer satisfaction and backward-compatibility as the technology evolves.”

We will have to wait and see who wins this race. Daniel Schreiber, president of Powermat, stated in an interview with ‘The Verge’ that standards are ultimately set in a coffee shop and not in a conference room. He reminded readers of the case of Wi-Fi versus HomeRF, where Starbucks’ endorsement of Wi-Fi in 2001 gave the technology irreversible momentum. So, will Starbucks’ backing do the magic for PMA too?

The author is a technically-qualified freelance writer, editor and hands-on mom based in Chennai.


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