TECHNICAL FIELD

The disclosure relates to wireless charging systems, and more particularly to multi-coil wireless charging systems.

BACKGROUND

With growing popularity of wireless devices, efficient wireless charging system for simultaneously charging a variety of wireless devices (e.g., cellphone, tablet, speaker, watch, headphones, IoT device) is useful. Having a single wireless charging system that can simultaneously charge multiple devices eliminates the inconvenience of managing multiple chargers.

A wireless charging system may be configured to charge multiple wireless devices simultaneously. The wireless charging system may include a charging surface on which wireless devices are placed to be charged. The wireless charging system may provide high degree of flexibility in the positioning of the devices on the charging surface by allowing devices to be placed at any location on the charging surface instead of restricting it to a specific location. However, because devices may be placed at different locations on the charging surface, it is challenging to determine how to drive the wireless charging system efficiently for all possible device placements. Additionally, some users cover their devices with protective cases or attach accessories such as phone stands or card holders to the back of their devices, which increases the distance between the charging surface of the wireless charging system and the receiver coils in the devices. Inductive charging used by wireless charging systems is based on distance between transmission coils and receiver coils, and the increase in distance between the transmission coils and the receiver coils adds another challenge for wireless charging systems because the coupling between the coils grows weaker with distance.

SUMMARY

A wireless charging system with multiple transmission coils allows for simultaneous charging of receiver devices by independently controlling each of the multiple transmission coils. The multiple transmission coils may be arranged in an array within the wireless charging system and each coil may be independently controlled by a coil drive system that outputs a driving signal to the coil. The driving signal may be selected based on target characteristics of the coil determined using a feedback system that includes one or more feedback channels. In some embodiment, a first feedback channel may be high precision measurements of voltage across the coils or current through the coils, and a second feedback channel may be communication signals from the receiver devices. Based on the first feedback channel and the second feedback channel, the wireless charging system determines how to drive a subset of the transmission coils for charging one or more receiver devices on the wireless charging system. The wireless charging system may detect the one or more receiver devices to be charged and select the subset of transmission coils for charging the detected one or more receiver devices, for example, using a machine learning algorithm.

