There have been a couple of developments in the wireless power world over the last couple months, both involving the new Rezence standard. You may recall that this is the new high-frequency resonant approach, as contrasted with the established lower-frequency Qi approach. We’ve reviewed the differences and proliferating standards before.
While Rezence beat out Qi in terms of establishing a resonant (as opposed to inductive, which is what legacy Qi is) standard, Qi (a resonant version of which is in the works) benefits from established infrastructure and channels. And standards aren’t product. So the Rezence allies have been trying to spin up infrastructure and design enablement so that they can get products on the market. Only then can they say that their approach has been truly proven and validated.
Late last year, they took another step in that direction. WiTricity released a development kit, the WiT-5000C3, to make it easier for designers to leverage the Rezence standard. The kit contains:
- A full-on reference design for a Class 3 charger (up to 2 smartphones or 1 tablet);
- Sample PTUs (power transfer units, aka chargers) and PRUs (power receive units, or chargees);
- Engineering eval tools; and
- A full set of documents.
(Image courtesy WiTricity)
One thing I noticed in the release was a reference to “classes” and “categories.” As in, this design is for a Class 3 charger, compatible with Category 3 devices and with tablets.
I inquired further into what this meant, and WiTricity sent the following tables. You can tell the standards folks had a task of choosing similar but different words for PTUs and PRUs. PTUs come in “classes”; PRUs come in “categories.” There’s no rule linking a particular class number to a category number – not in terms of what mates with what, nor in terms of power level.
As a Class 3 charger, then, it should be able to charge, at a minimum, one Category 4 device (tablet or phablet) and must support the maximum number of devices, two Category 3 units (smartphones). Just so happens that, from a power standpoint, 2x(Category 3) = Category 4…
Meanwhile, the expected merger between the Alliance for Wireless Power (A4WP) and the Power Matters Alliance (PMA) organizations was announced: a letter of intent has been signed, and the deal should complete mid-year.
While this was touted as proving that a “standards war” isn’t necessary, it also represents a blending of two relatively similar approaches. There’s a much bigger gap between the remaining two organizations. And, as far as I can tell, there’s little chance of further diplomacy. Both remaining sides – high- and low-frequency charging – remain firmly committed to their approaches.