A first approach to a pre-regulator based control for a contact-less power supply

In a contact-less power supply, energy is supplied to the load by means of a loosely coupled transformer. Primary and secondary windings of this transformer are physically and electrically isolated. In most applications, the relative position of the windings can change, but the load has to be supplied despite variations in the coupling coefficient. In this paper, a control strategy to provide a regulated output voltage is analysed. It is based on a DC-DC boost converter acting as a pre-regulator. In order to keep the electrical isolation between primary and secondary windings, output voltage can be estimated by measuring the peak value of the current through the primary winding and the voltage provided by the pre-regulator. Two prototypes of the contact-less power supply and the pre-regulator have been implanted to test the results. The pre-regulator is digitally controlled by an FPGA.