WIRELESS POWER TRANSFER

A power receiver () comprises an input circuit () with a receiver coil () extracting power from a power transfer signal generated by a power transmitter (). A variable load () applies a modulation loading to the input circuit () and a data transmitter () transmit data symbols to the power transmitter () by load modulating the power transfer signal during communication time intervals interspersed by non-communication time intervals during which no data symbols are transmitted. The data symbols are represented by modulation loading patterns and the data transmitter () is arranged to control the variable load () to repeatedly change the modulation loading during non-communication time intervals. The approach may provide improved communication and power transfer operation, and may in particular reduce transients, e.g. in the supply voltage provided to a load of the power receiver ().