Generic block diagram of an inductive wireless power system, in which power is transferred between wire coils by a magnetic fields . (Image courtesy of Chetvorno via Wikimedia Commons).
Each wireless power frequency has its unique restrictions and benefits. At lower frequencies, the antennas can be thinner, more durable, and easier to integrate with printed circuit boards (PCBs). On the other hand, NuCurrent’s antennas also have to account for the so-called “skin effect” that occurs in conductive wires at high frequencies. At such frequencies, the alternating current (AC) in a standard wire is focused around the edges, wasting the center part of the wire and raising the resistance.
NuCurrent’s core technology is multi-layer (ML) wire, which splits the AC current over multiple smaller-diameter wires. The ML wires provide more available surface area for the current to flow, a characteristic that lends itself to higher efficiency, thinner form factor, and better durability. The design allows for different shapes of multi-layer, multi-turn (MLMT) wire. The other benefit is that the wires can be integrated directly onto a PBC or other substrate without any soldering.
The benefit of using ML wire is that it gives NuCurrent antennas an extremely high quality (Q) factor, or the ratio of apparent power to the power losses in a device. The Q factor can have a value between 0 and infinity, but it has been difficult for engineers to reach values higher than 1,000 for antenna coils. For mass production, values around 100 are typical.
The company’s website says that, when compared to a standard Qi-based PCB A6 coil at 100 kHz, NuCurrent’s printed coils have a quality factor greater than 20% (which Texas Instruments apparently confirmed in separate tests). When compared to printed coils using the A4WP standard, NuCurrent has recorded a 60% higher quality factor.
NuCurrent has long been involved in the wireless charging industry. The company started a strategic partnership with Molex and has been selected as the reference antenna for the systems of other wireless power manufacturers. These include Broadcom, with its BCM59350 chip, and Efficient Power Conversion Corp. NuCurrent’s resonators were selected for the first commercially available, Rezence-certified (the A4WP’s standard) products and the WPC’s standard antenna for in-vehicle charging.
