Self-Resonant Coil With High-Order Compensation Characteristics

Self-resonant (SR) coils replace lumped with distributed compensation components, enabling efficient power transfer and high integration. However, current SR coils function merely as series (S) or parallel (P) resonant tanks, thereby supporting merely four low-order compensation networks: SS, SP, PS, and PP. High-order compensation networks have demonstrated superiority over low-order counterparts, providing enhanced safety, stability, and design flexibility. Unfortunately, no SR coil currently with high-order compensation network characteristics. This paper proposes a novel SR coil with LCC compensation characteristics that integrates the required compensation components in the form of distributed structures with the main coil on a single substrate, eliminating lumped components. To verify feasibility, a pair of SR coils, incorporating a normal SR coil, are fabricated, which constitute a SR coil inductive power transfer (IPT) system with LCC-S compensation characteristics. Different with traditional LCC-S systems, the compensation inductor in the proposed SR coil participates in power transfer. Therefore, corresponding formulas for the resonant frequency, AC-AC power transfer efficiency (PTE), output voltages and power are provided. Favorablely, the proposed IPT system exhibits three advantages: a constant voltage output independent of the AC load, high AC-AC PTE over a wide range of AC load values, independence of resonant frequency from coupling coefficients, and no damage to the front-end power source during no-load operation. Experimental results demonstrate a coil-to-coil PTE of 93.2% and DC-DC efficiency of 80.5% over a 35 mm spacing gap. In addition, a LED monitor is successfully powered, indicating its potential for application in electronic devices, such as mobile phones and laptops.