Analysis and Design of Self-Oscillating Magnetic Coupling Wireless Power Transfer Systems

Self-oscillating mechanism is of particular interest for wireless power transfer (WPT) systems because it guarantees optimal power transfer without needing any active tunings. However, this mechanism currently is only applicable to structures with capacitor parallel connection, and most of the WPT structures are connected in series with capacitors; then, the application field is very limited. To address this issue, the physical interpretation of self-oscillating WPT system is investigated, and the corresponding criteria are constructed: 1) impedance criterion: it can quickly and accurately determine which WPT topology can achieve self-oscillating and the parameter conditions the topology needs to meet; 2) general stability criteria: it can quickly and accurately determine negative resistance structures corresponding to different WPT topologies; and 3) startup criteria: it is used to determine the amplitude-stabilization link structure. With these criteria, these mechanisms have been successfully applied to the system with capacitor in series connection, greatly expanding the application field. These criteria can guide the design of any topologies system, which are not only the key to system structure and parameter design but also the basis for subsequent performance optimization.