Abstract: A power adaptor including an input for connection to an AC power supply, an output for connection to a load, and a resonant circuit coupled to the input that provides power to the output suitable for driving the load, is provided. The resonant circuit has two or more resonant frequencies, which are not harmonics of each other. The power adaptor includes a controller adapted to drive the resonant circuit at, or near, each of the two or more resonant frequencies to select different characteristics of the current drawn from the AC power supply, in use.