A 200-kHz/6.78-MHz wireless power transmitter featuring concurrent dual-band operation

A wireless power transfer (WPT) transmitter is presented that can simultaneously power devices operating at 200 kHz and 6.78 MHz, enabling a true multi-standard WPT transmitter. To achieve this, the proposed design utilizes two coils, each optimized for efficient power transfer when operating alone. By placing the coils co-axially on a single charging stand, concurrent power transfer is possible. However, nominally doing this invokes significant eddy current losses, degrading WPT efficiency. To combat this, an eddy-current filter is included in the 200 kHz path. The proposed design is built into a 12.5 × 8.9 cm
²
charging pad area, and at 25 mm separation, the system is able to concurrently power two smartphone-sized receiving devices at 25 mm separation. The system achieves a total power delivery of 9 W and 7.4 W with efficiencies of 78% and 70.6% at 6.78 MHz and 200 kHz, respectively.