6. Summary

This chapter delves into the fundamental principles and circuit modeling of wireless power transfer (WPT) systems, with a particular focus on inductive links. It explores magnetic flux phenomena, key parameters like coupling coefficient and mutual inductance, and presents equivalent circuit models for optimizing power transfer efficiency and power delivered to the load. The chapter also introduces multi-coil systems for enhanced efficiency and flexibility in weak coupling conditions. Additionally, it analyzes essential DC-AC and AC-DC converters, their principles, design considerations, and various configurations. Advancements in rectifier and energy receiver design are also highlighted, focusing on improving power conversion efficiency and system integration. The chapter discusses passive and active rectifiers, voltage doublers, and multipliers, as well as multi-output resonant regulating rectifiers for efficient power distribution. Furthermore, it explores adaptive and resonant-mode energy receivers for improved efficiency in long-distance and high-frequency applications. The chapter also covers efficient wireless power and data transmission techniques in inductive link-based systems, categorizing data telemetry by transmission methods and modulation techniques. It addresses challenges in power and size-constrained applications and discusses recent WPDT systems that integrate power supply with bidirectional data telemetry. Lastly, the chapter presents system-level approaches for optimizing wireless energy management in secure and biomedical applications, including energy backup receivers, optimal energy-reuse receivers, and adaptive wireless power systems for deep brain stimulation. Collectively, these innovations provide a foundation for efficient, compact, and adaptable power management in modern WPT systems.