Improved AC Pickups for IPT Systems

This paper presents two inductive power transfer (IPT) pickups capable of individually delivering 1.2 kW. The first circuit is a parallel-tuned ac-ac pickup and the second a series-tuned ac-ac pickup. Both circuits regulate the output power by creating a high-frequency ac source in a form suited to various applications requiring a controlled ac output but particularly stage lighting. These circuit topologies build on previous work by significantly improving the loading capability, reducing output noise and harmonic generation, and lowering the required switch ratings. This is achieved through the addition of a second resonant section within each pickup and the relocation of the soft-controlled ac switch. The addition moves the harmonics away from the load path and pickup while still providing full control of the output power. It enables a sinusoidal output waveform with low total harmonic distortion to be created, while placing less stress on the ac switch, which is no longer required to carry the load current. The steady-state operation of both circuits is analyzed herein and circuit waveforms have been verified by experimental results. Both the parallel and series circuits are used to drive a 1.2-kW load with a maximum pickup efficiency of 95% and 94%, respectively.