Loss Modeling and System Optimization of Smartwatch Wireless Charging Application

Wireless charging is increasingly popular in smartwatch applications due to its seamless user experience and premium product design. However, the heat generated during wireless charging can be a safety concern. This paper presents a comprehensive loss model of the smartwatch wireless charging system, which includes not only the wireless charging circuitry loss but also the metallic material losses around the system. Two system optimizations are proposed in this paper for the smartwatch application to improve the charging and thermal performance. Two system optimizations are proposed in this paper for the smartwatch application to improve the charging and thermal performance: 1) a magnet optimized solution that reduces the metallic material loss in the smartwatch; 2) a V
rect
optimized solution that shifts heat from the receiver coil to the transmitter side, reducing the hot spot temperature. Both theoretical analysis and experimental results using a form factor device validate the effectiveness of these optimizations.