A basic wireless charging system may include a wireless power transmitter unit (PTU) and a wireless power receiving unit (PRU). For example, a PTU may include a transmit (Tx) coil, and a PRU may include receive (Rx) coil. Magnetic resonance wireless charging may employ a magnetic coupling between the Tx coil and the Rx coil. A common issue seen in these types of wireless charging systems is during an initialization phase. In an initialization phase, the PTU attempts to detect whether a valid PRU is being placed on or near the Tx coil of the PTU. For example, the PTU may be configured to sense load variations during a first predetermined beacon period indicated a device is on, or near the Tx coil. The load variations may be caused by a PRU being placed on or near the PTU, but may also be caused by a conductive metal of an object, such as a coin, or a device having a non-valid receiving coil in terms of a wireless charging protocol of the PTU.
For example, a PTU may power on during the first predetermined beacon period to detect whether a load associated with inductive coupling of the Tx coil by an object has changed. If a change in load is sensed, e.g., compared to the previous period, the PTU will power on for a second predetermined beacon period that is relatively longer than the first predetermined beacon period. For example, the first predetermined beacon period may be 30 milliseconds. The first predetermined beacon period may be relatively short in comparison to a longer second beacon period of 100 milliseconds configured to follow the short beacon. If the object causing the load change is not a valid device, the power transmitted by inductive coupling to the non-valid device during the long beacon may damage the non-valid device. Further, if the device to be charged has little or no charge, the device may not be able to load power charging operations, such as wireless data transmission related to the wireless charging operations.
The same numbers are used throughout the disclosure and the figures to reference like components and features. Numbers in the 100 series refer to features originally found in FIG. 1; numbers in the 200 series refer to features originally found in FIG. 2; and so on.