Inductive Power Transfer Systems With Digital Switch-Controlled Capacitor for Maximum Efficiency Point Tracking

Inductor-capacitor-capacitor-series (LCC-S) compensation topology has been widely used in inductive power transfer (IPT) systems due to its constant coil current regardless of the load and the coupling coefficient. Usually, the inductance of transmitter coil is sensitive to misalignments of the magnetic coupler when the asymmetrical coil structure with a smaller size receiver coil is adopted. The fluctuation of the inductance of transmitter coil will increase the power losses in the primary inverter. To compensate the fluctuation of the transmitter coil inductance, a digital switch-controlled capacitor (D-SCC) for maximum efficiency point tracking (MEPT) of LCC-S compensated IPT system is proposed. Consequently, the proposed LCC-S compensated IPT system can achieve high efficiency against the fluctuation of transmitter coil inductance. In traditional switch-controlled capacitor, high- frequency current sensor is required for the synchronization between the transmitter coil current and the driver signals of the switch-controlled capacitor. Nevertheless, the drive signals of D-SCC can be generated directly by the DSP controller in the primary side without detecting zero-cross points of the transmitter coil current, which can improve the system reliability and reduce the cost. Furthermore, the MEPT based on D-SCC is easy to be implemented because only the input dc current measurement is required. A 3.3-kW prototype is presented to verify the validity of the proposed D-SCC-based MEPT.

Automated summary

The paper introduces a novel digital switch-controlled capacitor (D-SCC) for maximum efficiency point tracking in an inductor-capacitor-capacitor-series (LCC-S) compensated inductive power transfer system. The system achieves high efficiency power transfer against fluctuations in transmitter coil inductance, reducing power losses and costs.