Power adaptors

An electronic impedance matching circuit incorporating an LCL resonant circuit with input terminals and output terminals with a first inductor L1, connected from a first input terminal through a common point with second inductor L2, to a first output terminal, the second input terminal being directly connected to the second output terminal, and a capacitor C1, connected between the common point between the two inductors and the direct connections between second terminals of input and output, the input terminals being driven from a high frequency inverter, the output terminals being connected to a load of apparent impedance RL, the value of the components L1, L2 and C1 being chosen such that at least one frequency, the reactances of L1, L2 and C1 are approximately similar in magnitude and that at least one frequency the apparent impedance seen at the input terminals is transformed by the LCL resonant circuit to be approximately equal to the square of the reactance of the capacitor divided by the apparent impedance of the load, RL.

A power adaptor comprising an input for connection to an AC power supply, and an LCL series-parallel resonant circuit coupled to the input that provides an output suitable for driving a load, wherein the capacitance and inductance of the resonant circuit are selected to provide a pre-determined decrease in effective voltage, and a corresponding pre-determined increase in effective current, between the input and the output of the power adaptor.