Stabilising the output voltage of wireless power pickup through parallel tuned DC-voltage controlled variable capacitor

A new method to regulate the output voltage of the secondary side of an inductive power transfer (IPT) system through a DC-voltage controlled variable capacitor (DCVC) is proposed. As the equivalent capacitance of the DCVC can be controlled by a DC voltage, when it is used as a parallel tuning capacitor at secondary side of an IPT system, the output voltage can be controlled by this DC voltage through the effect of tuning and detuning. Further, a simple proportional plus integral control (PI) controller can be employed to generate the controlling DC voltage conveniently to make the output voltage constant. As there is no active switch used in the DCVC, it has no switch driving problems such as a high up to 20 V voltage source which is of particular advantage for its application at the secondary side of an IPT system. The DCVC also has the potential to be used at much higher frequencies than traditional switch mode capacitors because of the smoothness of the adjustment of its equivalent capacitance through a DC voltage.