It’s like Betamax and VHS. The United States and the Soviet Union. Tom and Jerry. The furious tussle between direct induction and resonant magnetic induction played out at the 2014 Applied Power and Electronics Conference (APEC). And while the glitzy booths and beguiling exhibits may have obscured the cold steel, bayonets, and gunpowder, make no mistake — this is a desperate fight that’ll determine the future of wireless power.
For years, the swanky halls of Sin City — and the Consumer Electronics Show — served as the wireless charging battleground, and inductive charging won the day. Consumer-friendly widgets like Powermat proved that inductive charging was a mature technology (and cheap). But the battle has shifted to the Southwest quadrant — Fort Worth, TX to be exact — and the unofficial theme of APEC this year was definitely wireless power.
Nearly every vendor I met with showcased their take on wireless power — specifically, wireless charging — and several more outspoken reps even gave their opinion on the battle of the standards. The consensus seemed to be that, while direct induction is an established, mature standard, with several notable applications for the end-user, resonant induction is the future. And while kitschy displays demoing charging techniques for smartphones might be great fodder for trade shows, the real potential lies in wireless power. And cool standards with cryptic titles like “Qi.”
We’re all familiar with the Qi (pronounced “Chi”) inductive charging standard, whether we realize it or not. Developed by the Wireless Power Consortium, this interface standard relies on a transmission pad and a compatible receiver, and power can then be transferred up to 4 cm via resonant inductive coupling.
Compared to direct induction, resonant induction is relatively inefficient (around 80%) versus 90-95%. But resonant charging affords more flexibility — the primary coil generates a magnetic field, and you don’t necessarily need alignment. This allows for spatial freedom and farther distances than with direct induction (or inductive coupling), where the two coils are very close together.
Direct induction is a fine standard — and like Betamax, it could win the day — but only resonant coupling will allow for cool applications like wireless electric vehicle charging or powering light bulbs without the cord.
And for tech journalists like me who’re forever looking toward the future, resonant coupling — with all its potential — is the sexier choice.