Smart phones are becoming an integral part of vehicle infotainment options, but this integration is putting a strain on the phone’s battery. In-vehicle wireless charging is increasingly seen as a preferred solution, and the normally-reticent auto industry is moving quickly to bring the technology to market.
“The auto industry has been an early adopter,” said John Perzow, the Wireless Power Consortium’s (WPC) Vice President of Market Development. “They’ve been faster than other infrastructure fields like hotels and restaurants.”
Wireless charging has been around for years, but only recently has the technology started gaining acceptance. Two standards are currently seeing use in automotive applications. The WPC’s Qi has strong automotive support. Many dual-technology applications include the PMA standard created by the Power Matters Alliance, which is now part of the AirFuel Alliance. Many analysts feel that the growth curve is pointing upward.
“Despite limited OEM implementation of wireless charging between 2012 and 2014, Strategy Analytics forecasts strong growth of 75.3% CAGR between 2014 and 2022, growing to 20.3 million units by 2022,” said Mark Fitzgerald, Associate Director for Strategy Analytics’ Automotive Practice. “Currently, dual-standard, AirFuel/Qi systems are the preferred solution.”
Researchers at IHS said consumer awareness of wireless charging technology doubled in 2015, reaching 76% of consumers in the U.S., U.K. and China. Mobile phones with wireless power receivers surpassed 120 M units in 2015.
Some studies have suggested that drivers are more likely to set phones on a wireless charging platform than to plug phones in, especially on short trips. Battery life is becoming more of an issue as drivers use features like near-field communication, Bluetooth and navigation.
Auto industry chipmakers are gearing up. NXP Semiconductor recently released the industry’s first 15W multi-standard wireless charging solution. It supports the new 15W version of Qi, which will shorten charging times compared to the existing 5W technology, as well as the 5W PMA standard. Though no phones currently offer the 15W technology, it’s expected to see implementation during vehicle lifetimes.
“By the time this goes into production in cars, there will be a proliferation of 15W devices in the field,” said Denis Cabrol, NXP's Marketing and Systems Director. “This gives automakers staying power for the long term.”
Standards battle and EMI challenges
While there’s optimism surrounding wireless charging, there are also hurdles. Some cell phone providers have dropped the technology after using it, raising questions about its role. The standards battle between Qi and PMA, which are primarily inductive technologies, is exacerbated by a resonant charging standard also managed by the AirFuel Alliance.
“Multiple standards slow down progress,” said Geoff Gordon, Co-chair of the AirFuel Alliance Marketing Committee. “That’s why we merged [with the Alliance for Wireless Power] and brought the Rezence resonant charging technology in. We’re very open to a grand alliance merger to bring all the wireless standards together.”
He noted that there aren’t any formal discussions to merge the two standards organizations. That means developers will have to work with two technologies, which impacts price and complexity.
“Due to the difference in the technical specification and compliance requirement, it is difficult to support multiple wireless power standards with one solution.” said Pearl Cao, Systems Engineer at Texas Instruments. “It also may not be as cost effective, efficient, and size optimized compared to a single standard solution.”
There are a few design concerns in automotive applications. Qi and PMA both operate around 100-200 MHz, so care must be taken to avoid interference with AM radios. Electromagnetic interference is a key factor in designs.
“A tightly coupled system, like the Qi magnetic induction, does not radiate much overall, as the magnetic flux is contained between the transmit and receiver coils and a ferrite screen is placed behind them,” said Paolo Battezzato, Applications Engineering Manager at STMicroelectonics. “However, as all systems based on switching regulators, proper design and layout are key to keep EMI below the limits.”
Charging platforms housed in center consoles will also have to account for objects that move about. If metal objects like coins or keys are on the charging station, systems could overheat, making foreign object detection a requirement. Thermal issues will also be an important factor.
“The intrinsic losses in the transmit and receive coils can be minimized up to a point,” said Max Cortiana, STMicroelectronics Product Marketing Manager. “Therefore, it is critical to reduce losses in the IC and other electronic components and use proper layout techniques, to minimize power waste and assure proper heat dissipation.”