Claims:1. An apparatus for a wireless power transmitter, the apparatus comprising:
a coil; and
control circuitry to:
apply a first signal to the coil and measure a change in a current in the coil to discover presence of an object;
provide a second signal to the coil, subsequent to discovering presence of the object;
detect whether the object is a Power Receiver based on whether a load modulated signal is received from the object subsequent to providing the second signal; and
perform power transfer to the object subsequent to detection that the object is a Power Receiver.
, Description:Technical Field
This disclosure relates generally to techniques for wireless charging. Specifically, this disclosure relates to load modulation during initialization phases of wireless charging.
Background Art
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.