An Improved Pulse Density Modulation of High-Frequency Inverter in ICPT System

Pulse density modulation (PDM) is often applied in inductively coupled power transfer (ICPT) systems to improve high-frequency inverter (HFI) efficiency. However, the PDM may cause the inverter output current fluctuation, even interruption for light load or low-quality factor system. This may result in the difficulty for the implementation of soft switching in ICPT. In this article, an improved PDM (IPDM) strategy is proposed by optimizing the distribution of switch sequences. Through the current fluctuation numerical analysis and Fourier decomposition, IPDM can reduce the current fluctuation and improve the system efficiency. The experimental results on a 20 kW ICPT system prototype show that the proposed IPDM strategy reduces the HFI output current ripple coefficient is 40% to 65% lower than PDM, and the efficiency is also improved.