WIRELESS POWER TRANSFER

A power transmitter (101) provides power to a power receiver (105) via an electromagnetic power transfer signal. The power transmitter (101) comprises an output circuit (302, 103) with a transmitter coil (103) generating the power transfer signal in response to a drive signal generated by a driver (301). A configuration controller (303) switches between power transfer configurations having different maximum power limits and voltage amplitudes for the drive signal. A transmitter (307) transmits a power configuration message to the power receiver (105) comprising data indicative of a voltage amplitude for a first power transfer configuration a receiver (305) receives a power transfer configuration change request message from the power receiver (105). The configuration controller (303) switches the power transmitter (101) to the first power transfer configuration in response to the power transfer configuration change request message. The approach allows a power transmitter and receiver to collaborate to change power transfer configurations providing different maximum power limits.