Optimized NFC Circuit and Coil Design for Wireless Power Transfer with 2D Free-Positioning and Low Load Sensibility

Area of Science:

• Electrical Engineering
• Electromagnetics
• Wireless Power Transfer

Background:

• Near Field Communication (NFC) technology is evolving to include wireless charging capabilities.
• Designing efficient wireless power transfer (WPT) systems for NFC requires specialized coil optimization and circuit design.
• Existing coil design methods often focus on square shapes, limiting flexibility for emerging applications.

Purpose of the Study:

• To propose an optimization method for designing transmitter and receiver coils for 13.56 MHz NFC wireless charging.
• To develop guidelines for creating rectangular coils that maximize efficiency across diverse receiver placements.
• To analyze and select an optimal receiver circuit topology for stable performance under varying loads.

Main Methods:

• An optimization procedure was developed to determine optimal dimensions for rectangular transmitter and receiver coils.
• A circuit analysis identified the series-parallel compensation network as suitable for receiver design.
• A prototype system with optimized coils was constructed and experimentally validated.

Main Results:

• The optimized rectangular coils achieved high efficiency (80-88.3%) for NFC wireless charging.
• The system demonstrated consistent performance with receiver movement over an 8 cm x 12 cm surface.
• Efficiency remained robust despite load variations from 36 Ω to 300 Ω.

Conclusions:

• The proposed optimization method effectively facilitates the design of efficient rectangular coils for 13.56 MHz wireless power transfer.
• The series-parallel compensation network is a viable topology for NFC wireless chargers, ensuring low efficiency sensitivity to load changes.
• Experimental results confirm the theoretical predictions, validating the design approach for practical NFC charging solutions.