An Accurate Frequency Tracking Method Based on Short Current Detection for Inductive Power Transfer System

Frequency drifting is a common problem in an inductive power transfer (IPT) system. Conventional autonomous oscillation method for maintaining soft switching is challenged due to the drawbacks of feedback delay and disturbance, resonant failure, and requirements of additional start-up circuit. A novel frequency tracking method based on short current detection is proposed for IPT applications. In addition, an instantaneous short current detection method utilizing cheap comparator is proposed. Furthermore, a fast and accurate tracking method is proposed to calculate the frequency mismatch and make a correction. The method can realize accurate frequency correction in several oscillation periods. Furthermore, the method is simple and economic for hardware implementation. Finally, the results of the experiment and comparison results verified the frequency tracking method.