A Novel Receiver Sensing Scheme for Capacitive Power Transfer System

전계결합 무선전력전송의 수신부 감지 방법

Abstract

Wireless power transfer systems require an algorithm to determine the presence of the target object for mitigating standby power and safety issues. Although many schemes that sense various external objects have been actively proposed for inductive power transfer systems, not many studies on capacitive power transfer systems have been conducted compared with those on inductive power transfer systems. This study proposes a target object detection algorithm by monitoring the capacitance in transmitter-side electrodes without additional pressure sensors or distance sensors. The proposed algorithm determines the presence of a target object by monitoring the change in capacitance in transmitter-side electrodes using the step pulse of the microcontroller unit. The algorithm is verified by two step processes. First, the performance in capacitance measurement is compared with that of an LCR meter. Then, the verification is conducted in a 5-W capacitive power transfer hardware. Experimental result shows that the interelectrode capacitance increases by 6 times when the target object is fully aligned. Thus, the proposed scheme can successfully detect the presence of the target object.

Fig. 1. A typical CPT system converter.

Fig. 2. Detailed circuit modeling of CPT link capacitors.

Fig. 4. CPT circuit with relay switch.

Fig. 6. Receiver detection flowchart.

Fig. 7. Implemented hardware for verification.

Fig. 8. System operation waveforms.

Fig. 3. Capacitance measuring circuit.

Fig. 5. Capacitance measurement waveforms by MCU.