Wireless Charging: Power without Boundaries Becomes Available to the Masses


Graham Robertson, Vice President, Corporate Marketing at Integrated Device Technology

Graham Robertson

Wireless charging has been in the wilderness, hidden in a chasm until standardisation, strategic partnerships and technology integration recently gathered pace. The market is predicted to become worth billions of dollars in the next few years - yet it has been the domain of a few Tier-1 companies as the resources and know-how needed to develop and integrate solutions were significant. The latest technology is already out-dating the cumbersome initial solutions and IDT is leading the charge in packaging and democratizing this sophisticated technology so that anyone could develop a solution in hours.

Bridging the chasm

Wires are bad. The can fray or fracture, connections can become tarnished or damaged - not to mention man’s ability to forget, lose or trip over the ever-important cable. As we try to eradicate wires, we live in an increasingly wireless society - but until now, the focus has been on wireless data, principally driven by wireless Ethernet and Bluetooth. 

Despite the substantial and somewhat obvious benefits, history shows that wireless technology takes time to be adopted. Ethernet was invented as a wireless communication technique in 1973 (hence ‘Ether’) but the early implementations were solely with cable until at least twenty years later.

The chasm in wireless power is far greater. The history of wireless power stretches back to 1831, when Michael Faraday discovered electromagnetic induction. It rose again in the late 1800s, when Nikola Tesla began conducting tests transmitting power by inductive and capacitive coupling.

Then, nothing. For the entire 20th Century. We were all too busy replacing valves with semiconductors, sending men into space and jumping onto the World Wide Web.

In 2006, researchers at the Massachusetts Institute of Technology (MIT) reported that they had discovered an efficient way to transfer power between coils separated by a few meters. The team, led by Marin Soljačić, theorized that they could extend the distance between the coils by adding resonance to the equation. 

As the 21st century dawned, mobile computing spiraled. Consumers could carry devices with computing power far beyond what they had on their desk only twenty years before. The Internet became ubiquitous, wireless connectivity matured and consumers could email, surf and communicate on the move - until the power ran out. Without power, our 21st century road-warrior became shackled to a wall outlet by their charging cable before resuming their carefree mobile life.

The market for wireless charging

If cables are not yet dead, they soon could be, at least as far as mobile device charging is concerned. Wireless charging is set to become the preferred means of charging mobile devices such as smartphones, tablets, and the ‘hybrid’ phone / tablet format referred to as ‘phablets.’

The success of wireless charging will be based on a combination of high technology and pragmatism. The challenge of transferring power without wires has been solved and is evolving rapidly - the simplicity, safety, reliability and pure convenience will ensure wide adoption approaching ubiquity once consumers understand the benefits - not least, never having to worry about forgetting their charger and cable.

Figure 1: Global Forecast of Wireless Power Transmitter and Receiver Market revenue ($M)

Early wireless charging systems have typically been novelty aftermarket items and really did not offer a viable alternative to conventional adapters and cables. The systems available were cumbersome and bulky, requiring the mobile device to be inserted in a charging sleeve before being placed on the charging mat. Retail prices were high, generally in excess of USD100 for a complete solution and consumers had to carry the charger and cradle with them. Adoption stalled as the wireless charging benefits were not realized and cables were simply easier, lighter and cheaper.

If the technology is to be successful, then elegant and inexpensive technical solutions and market adoption are key pre-requisites. Adoption brings more entrants to the market, increases innovation and ultimately drives costs down to a point where adoption becomes universal. History has shown us that in the early stages of market formation competing solutions and standards - whether formally defined or de-facto - are critical for enabling the necessary adoption. Once coherent standards exist and interoperability between manufacturers and standards is proven the market will accelerate even more rapidly.

IHS Technology, when launching its Wireless Power Report in 2014, forecast that revenue from shipments of wireless power transmitters and receivers would rise from $216 million in 2013 to $8.5 billion in 2018, an almost forty-fold increase.

The changing standards landscape

As with many other emerging markets fragmentation precedes con-solidation (remember VHS and Betamax?) and wireless power is no exception - but there are signs that alignment and consolidation are on the horizon.

Leading industry players, including software and component companies, handset manufacturers and network operators, came together to develop the standards needed to allow interoperability between charging systems and mobile devices from different manufacturers. 
In the early days, three major groups were vying for supremacy within wireless power, The Wireless Power Consortium (WPC), the Alliance for Wireless Power (A4WP) and the Power Matters Alliance (PMA). In early 2014, A4WP and PMA agreed to join forces and this was approved by a vote of the A4WP and PMA boards on June 1st, 2015. On November 12th, 2015 the new combined entity announced that it would be known as the AirFuelTM Alliance.

The newly-aligned and branded AirFuelTM Alliance is currently 195 members strong and board of directors companies include AT&T, Broadcom, Duracell, Flextronics, Gill Electronics, Integrated Device Technologies, Intel, MediaTek, ON Semiconductor, Powermat Technologies, Qualcomm Inc., Samsung Electronics, Samsung Electro-Mechanics, Semtech, Starbucks and WiTricity.

The Wireless Power Consortium currently has 227 members and their Board of Management / Steering Committee comprises ConvenientPower, Delphi Automotive Systems LLC, DongYang E&P Inc., Freescale Semiconductor, Fulton Innovation, Haier, HTC, Integrated Device Technologies, Leggett & Platt, LG Electronics, Microsoft Corporation, Nokia, Panasonic, Philips, PowerbyProxi Inc., Qualcomm Inc, Rohm Co Ltd, Samsung, Sony Corporation, STMicroelectronics, Texas Instruments, Toshiba and Verizon Wireless.

A quick examination of the board members will show how the industry is split between the two camps with only a handful of organizations taking up a leadership position in both. One of these industry-leading organizations is IDT who hold a board-level position in both organizations and can be considered a significant force in this industry. 

The technology behind Magnetic Inductance (MI) charging

Essentially, the principles and technology behind MI charging are very similar to most switch-mode power supplies (SMPS) used by the billion in the world today. 

In the simplest form, the AC mains voltage enters the wireless transmitter / charger and is turned into DC via a rectifier. This is then ‘chopped’ into a high-frequency AC signal (typically between 100-200kHz for MI charging).

In a traditional SMPS this high frequency AC waveform is then passed into a magnetically-coupled transformer that changes the level of the voltage before again rectifying the voltage to supply DC to the load.

Perhaps the easiest way to understand the similarities and differences is that in an SMPS the transformer is a single component with the primary and secondary windings coupled very efficiently by a material such as Iron or Ferrite. In MI, the transformer is split. The primary winding is part of the transmitter / charger and the secondary wind-ing is embedded in the receiver - which is the mobile device being charged.

The obvious difference is that in MI air itself forms the coupling between the primary and secondary and the coupling between the two magnetic fields is much looser. However if certain basic criteria are met (spacing of charger and device, size of coils and distance between coils relative to the size of the coil) then a good coupling can be achieved and power transferred.

Figure 2: The basic principle of transfer power via Magnetic Induc-tance charging

MI charging relies on a physical charger (usually in the form of a charging mat). The device to be charged is placed on the mat, the charger detects its presence and charging commences. 

The WPC says that operating the transmitting coil of an MI charger at a frequency slightly different from the receiver’s resonant frequency ensures the highest power and efficiency. This off-resonant operation requires the transmitting and receiving coils to be in close proximity. Hence, charging can be sensitive to the alignment of the coils, meaning, in practical terms, that the device has to be carefully placed and not knocked during charging. A multi-coil transmitter reduces this sensitivity, and also allows simultaneous charging of multiple mobile devices. 

Magnetic Inductance (MI) vs Magnetic Resonance (MR) - how do they stack up?

There are two fundamental technologies emerging within wireless charging, the already described Magnetic Inductance and Magnetic Resonance. Within wireless charging there are two priorities which compete, to an extent, and the ideal solution will depend upon the application.

A simple comparison of the two approaches illustrates the key differences in an application: magnetic inductance requires close coupling and can achieve the highest levels of efficiency when x/y displacement is minimal. Meanwhile, magnetic resonance allows better spatial freedom though it cannot match the peak efficiency of inductance-based approaches. Figure 3 below illustrates this difference, showing the ‘focus’ of MI against the ‘breadth’ of MR. 

Figure 3: Magnetic inductance technology achieves greater efficiency levels when displacement is minimal. Magnetic resonance cannot achieve the same performance when transmitter and receiver are close together, but efficiency does not drop off as quickly when displacement increases.

Future outlook for wireless power

We have already seen that the market is predicted to grow rapidly. The availability and ease of use of the technology will play a key role in adoption, both with the end consumer (device user) and the original equipment manufacturers (OEM) who will incorporate this technology into furniture, cars, airports, cafes, trains and the like.

While battery technology is improving rapidly, users demands and reliance on their mobile devices increases so the need to charge ‘on the move’ is set to increase - mobile devices become essential when they become the primary means of paying for goods and services, for example. However, will manufacturers, retailers and service providers make charging stations available until there is a large enough installed base of devices that can take advantage of the technology? Will the device manufacturers include the charging coils in their mobile devices until consumers can easily access charging stations? Both the infrastructure and installed base of devices have to grow together for the value proposition to be realized.

Looking to recent product announcements we can see that investment and adoption is already happening - maybe more than we initially realize. Qi charging was incorporated in the Nokia Lumia 820 and 920 in September 2012. It was also present in the Nexus 4 from Google / LG as well as Motorola Mobility’s Droid 3 and 4 and HTC’s Droid DNA. The inclusion of wireless charging continued into 2013 with the Samsung Galaxy S4 as well as Google partnering with ASUS on the Nexus 7 and with LG on the Nexus 5. 
The Apple watch, set to define a new category of wearable devices also includes wireless charging and earlier this year Samsung announced that their flagship S6, S6 Edge and S6 Edge+ include technology to wirelessly charge from both Qi and PMA compatible chargers - the start of universal compatibility.

On the charging side, Samsung has incorporated a Qi-based wireless charging function into their latest LED monitor. The mobile device rests on the monitor stand and charges while you watch, work or surf.
While the progress is rapid and clearly on a trajectory that will only accelerate, the forecast exponential growth needs support from a large number of OEMs - not just the ‘Tier 1’ companies. Ideally, access to the technology will be democratized into a multitude of smaller companies and, ultimately, the consumer themselves.

Some of the major players are supporting the democratization process. IKEA is now selling furniture with the technology built-in. More interesting are the kits they are now offering where the consumer can purchase a charging pad - and the appropriate sized hole saw - and fit a charging pad almost anywhere. This fuels the democratization process as consumers are not required to commit to the expense of replacing furniture to take advantage of wireless charging. 

However, the easy availability of the modular solutions also allows low-volume furniture suppliers to integrate the technology with no technical expertise - or restaurant owners - or libraries, the list is long and the only limit to the spreading of wireless charging will be people’s imagination.

IDT has moved democratization to a truly exciting new level with the announcement of a new range of plug-and-play kits. These pre-con-figured transmitter and receiver boards are built around proven IDT wireless power semiconductors, and include easy-to-use reference boards and comprehensive support materials. The kits make integrating wireless charging easy, practical and affordable for companies without the need to invest in gaining an in-house understanding of wireless technology.

Figure 4: Plug-and-play kits

In effect, IDT has removed the barriers-to-entry by doing much of the heavy lifting themselves, embedding their know-how, expertise and market-leading technology into simple modules which can be used by almost anyone.

In order to illustrate the point, the first run of the kit prototypes arrived at IDT’s offices around 5PM one evening. Within around 200 minutes an engineer had successfully converted a set of headphones that charged through metal prongs in a cradle into a set of headphones that charged wirelessly.

Even in the early stages, it is clear that IDT’s approach is driving democratization. “These kits were developed for the mass market, and since introducing them in August, we’ve had orders and design-ins from a remarkably broad array of companies,” said Mario Montana, IDT vice president and chief sales officer.

The IDT kits make creating new applications simpler and quicker through the inclusion of instructional videos, user manuals, foreign object detection (FOD) tuning guides, layout guides, layout instantiation modules, schematics, bill-of-materials (BOM), Gerber files, and more. Beyond this, the high level of integration offered enables system designers to achieve considerable savings in terms of bill-of-materials and engineering costs, compared to earlier commercial wireless charging systems that were typically built using discrete components. Hence the latest highly integrated chipsets from IDT also enable much smaller equipment sizes and greater system reliability, which will have a major influence on widespread market adoption of wireless charging.

Key commentators in the industry are quick to endorse IDT’s initiative. David Green, research manager, Power Supplies & Wireless Power at IHS, supported this view by writing: “Integrating wireless power capabilities into existing electronics is a complex process, and one of the factors that has unquestionably slowed its adoption throughout the electronics industry. This approach of providing self-contained, ready-to-go wire- less charging kits has the potential to change the landscape for those not yet equipped.”

Clearly, the innovative approach IDT is taking to making their technology available on a plug-and-play basis to everyone will be looked back on as a tipping point on the short journey to ubiquity for wireless power.

Source: Bodo's Power Systems, January 2016