PHASE MODULATED WIRELESS CHARGER

Systems, methods and apparatus for wireless charging are disclosed. A charging device has a resonant circuit comprising one or more transmitting coils, a driver circuit configured to provide a charging current to the resonant circuit, a zero-crossing detector configured to provide a zero-crossing signal that includes edges corresponding to transitions of a voltage measured across the resonant circuit through a zero volt level or corresponding to transitions of a current in the resonant circuit through a zero ampere level and a controller. The controller may be configured to cause the driver circuit to provide the charging current to the resonant circuit when a receiving device is present on a surface of the charging device, and control a level of power that is wirelessly transferred to the receiving device by phase-aligning the charging current with a phase-modulation signal generated from the zero-crossing signal.