SoftCharge: Software Defined Multi-Device Wireless Charging Over Large Surfaces

This paper proposes a method for converting a large existing surface into a programmable wireless charger, capable of distributing energy efficiently at multiple locations on demand and charge different types of devices. The key innovation here is to combine magnetic resonance-based energy transfer with the so called concept of 'energy hopping' across wireless inter-connected coils, where the magnetic fields are carefully shaped on the fly. The overall framework, called SoftCharge, has three components: (i) energy tiles (ETs), which are individual programmable coil units that can be attached underneath an existing table with AC mains supply only to the master tile, (ii) energy shaping algorithm executed by the master tile, that shapes the flow of energy over tiles through real-time impedance adjustment combined with selective power blocking, creating optimal energy paths to specific tiles where a device needs to be charged, and (iii) a resonance sensing architecture design and method executed in each given tile that detects the type of device to be charged and its location without any direct feedback. We build a prototype of energy tiles and provide experimental results on SoftCharge charging multiple COTS devices like mobile phones, laptops, tablets, and drones, resulting in a maximum charging rate of 23 W up-to 20 cm over a larger surface.