Voltage control of inductive contactless power transfer system with coaxial coreless transformer for DC power distribution

Application of an inductive contactless power transfer system to electric plug and outlet dc power distribution has been proposed. The proposed system consists of two solenoids which function as a coaxial coreless transformer, a half bridge inverter on a primary side and a diode rectifier on a secondary side. This system can be arcless, small-size and voltage-convertible. However, the rise of output voltage under light load condition was observed in the experiments. In this paper, to suppress the rise of the output voltage, employment of a cascade half bridge inverter and an output voltage estimator is proposed. Voltage control of the proposed system was verified through experiments using a 1 kW class prototype. Additionally, a high efficiency of 93.6% was achieved.