Samsung's Galaxy S4 requires an accessory case in order to charge wirelessly. When Samsung's new Galaxy S4 smartphone went on sale this month, lost among the fourth-generation phone's new features was its ability to charge wirelessly through the use of a special accessory case.
Samsung's wireless charging capability is based on the popular Qi (pronounced "chee") standard that's the basis for most of today's wireless charging products. But this week, Samsung also made it clear that Qi-based charging is not its future. Instead, the company plans to release products with native wireless charging capability based on a specification that offers multiple-device charging.
The spec, WiPower, is based on magnetic resonance charging, which offers a larger charging field.
"That's where the future is headed," said Michael Lin, a principal engineer at Samsung Electronics. "The use cases are just more compelling. That's why we've invested so much in developing it. We think it will address the charging needs of a much wider audience."
Samsung Electronics and Qualcomm partnered a year ago to form the Alliance for Wireless Power (A4WP), which developed and is promoting the WiPower specification.
Unlike the Qi specification, which is based on magnetic induction technology, WiPower offers a larger charging field. That means multiple devices, such as a tablet or smartphone, can be placed on the same pad and charged at the same time.
To date, most products in the market have been built around magnetic induction charging techniques, which require that the device be in contact with a charging surface, such as a charging pad. The device cannot be moved more than a couple of millimeters before the magnetic power connection is broken.
The leading charging pad supplier to date has been Duracell's Powermat technology, which uses magnetic induction.
While resonance charging is based on the same transmitter/receiver coil technology as magnetic induction, it transmits power at a greater distance. Other companies, such as WiTricity or Power By Proxi, offer devices based on other specifications that can charge from feet away or can be charged simultaneously by dropping them into a box.
Fady Mishriki, of Power by Proxi, shows how distance charging works.
"From Samsung's standpoint, with as many phones as we sell, we can increase [adoption] of the standard and really create an ecosystem for wireless power ... and create interoperability across the industry," Lin said.
Samsung reportedly also plans to release a wireless charging Pad for the Galaxy S4. Samsung declined to comment on those reports.
"Our basic use case would be someone with a tablet and a smartphone who would like to have an easy drop-and-go experience for their wireless charging experience," said Kamil Grajsky, vice president of engineering at Qualcomm and president of the A4WP.
The WiPower specification, released in January, defines several categories or classes of charger. The categories include charging pads that are the size of a single smartphone and larger pads that are about the size of a half-sheet of letter-sized paper.
Critics of magnetic resonance charging have said that as multiple devices are added to a pad or charging box, the wattage being supplied to each mobile device decreases as the power is shared.
Grajsky said chargers will likely be rated for multiple devices.
"If you put a tablet and a smart phone on a system rated for 5 watts, yeah, the system will try to share that 5 watts across those two devices," he said. "But, if you put two devices on a charger rated for 22 watts, then the tablet and the smart phone will get a full charge."
Grajsky also argued that magnetic induction charging carries with it not only its restricted charging field, but also the drawback that it tends to heat foreign metal objects that come into contact with the charging surface.
"The frequencies at which tightly coupled solutions operate are not that far from the frequencies that are used for conductive cooking," he said. "The tightly coupled solutions today have a problem where they can heat the metal surfaces in the smart phone & or metal objects. The result is that a lot of times [with] the tightly coupled solutions, the foreign object detection either dials back the power or simply turns the power off."
Smartphone manufacturers won't begin shipping WiPower enabled phones and charging pads until next year, Lin said, assuming equipment manufacturers begin production in the second half of this year.
"Our interoperability spec was formalised in January. We're working now to finalise the certification programs that manufacturers will go through in order to create a certified product," Grajsky said.