Bluetooth Low Energy-equipped power transmitter wirelessly charges wearables and other portable electronic devices fitted with RF energy harvesting chips
Powercast’s ‘PowerSpot TX91503 wireless transmitter’ employs Nordic’s nRF51422 Bluetooth LE multiprotocol solution for wirelessly scheduling power transmissions and monitoring battery status of charging devices
Nordic Semiconductor today announces that Powercast Corporation, a Pittsburgh, PA-based RF wireless power technology company, has selected Nordic’s nRF51422 Bluetooth® Low Energy (Bluetooth LE) multiprotocol System-on-Chip (SoC) for its ‘PowerSpot® TX91503 PowerSpot wireless transmitter’, which the developer claims is the first FCC- and ISED-approved solution to provide far-field wireless power over distance for mobile consumer electronics applications.
Employing a 915-MHz RF signal, the PowerSpot wireless transmitter outputs up to 3W Effective Isotropic Radiated Power (EIRP) (and associated ID data) that can directly power or charge up to 30 portable low-power devices—including fitness bands, wireless headphones, game controllers, hearing aids, and a variety of smartcards—that are fitted with Powercast’s patented embeddable ‘Powerharvester®’ technology.
The Powerharvester solution consists of a proprietary converter chip and a boost converter chip that once integrated in end devices, harvest intentional energy from the PowerSpot wireless transmitter as well as anticipated and ambient RF energy from other RF sources. The chips then convert that energy to DC power that can then be used to charge batteries or directly power the enabled devices.
Acting as the main ‘brain’ of the PowerSpot TX91503 wireless transmitter, the 32-bit Arm® Cortex® M0 CPU-powered Nordic nRF51422 SoC makes the transmitter ‘smart’, configurable, and controllable. For example, it configures and controls the transmitter’s 915MHz oscillator/PA subsection that feeds the power antenna and turns off the transmitter when wirelessly-connected devices are fully charged. The nRF51422 SoC also provides Bluetooth LE wireless connectivity for communication between the user’s end devices and the transmitter to monitor the battery staus of connected devices. This Bluetooth LE wireless connectvity also allows the user to employ a Bluetooth 4.0 (and later) smartphone or tablet to remotely monitor device charge levels and set timers for the transmitter to charge devices during certain periods, for example overnight, via Powercast’s iOS or Android companion app.
“We leveraged Nordic’s highly-integrated hardware and SoftDevice to do everything in a single chip for a much simpler design”
The PowerSpot wireless transmitter automatically powers enabled devices it detects within its charging zone and stops charging when no devices are within range. According to the company, the wireless transmitter can charge and power smaller, less power hungry devices—such as smart cards and basic sensors—at distances up to 24 meters while for more power hungry devices like game controllers, headphones, and smartwatches, the most suitable charging range is typically within 30cm. The transmitter itself can be mains- or USB-powered, so the ultra low power consumption of the nRF51422 SoC was important to keep the temperature of the 915-MHz subcircuit low, and enhance the efficiency of wireless power transmission.
Nordic’s nRF51422 SoC is a powerful, highly flexible multiprotocol SoC ideally suited for ANT™ and Bluetooth LE ultra low power wireless applications. The nRF51422 is built around the Arm CPU and includes 256kB/128kB Flash + 32kB/16kB RAM. The SoC is supplied with Nordic’s S310 SoftDevice, an ANT and Bluetooth LE RF protocol software ‘stack’ for building concurrent ANT and Bluetooth LE solutions.
“Rather than needing a separate microcontroller and Bluetooth LE radio, we leveraged Nordic’s highly-integrated hardware and SoftDevice to do everything in a single chip for a much simpler design with elegant circuitry,” says Eric Biel, Principal Engineer at Powercast. “We also needed low power consumption, and here again the Nordic SoC excelled.
“Finally, the pricing and availability of the nRF51422, along with Nordic’s hardware and software support, allowed us to accelerate the development schedule.”