CMOS High-Efficiency Wireless Battery Charging System With Global Power Control Through Backward Data Telemetry for Implantable Medical Devices

A high-efficiency CMOS wireless battery charging system with battery voltage tracking and global power control through the proposed pulsed load-shift keying (PLSK) backward data telemetry technique is designed. The power transmitted from the adaptively controlled power transmitter (ACPT) for battery charging is automatically adjusted with the battery voltage tracking through the PLSK backward data telemetry. Therefore, the generated rectifier output voltage is only slightly larger than battery voltage and tracks with battery voltage during the charging time of linear battery charger. Experimental result shows that the average receiver efficiency with battery voltage tracking from 3.3 V to 4.2 V and global power control is 90.9% which is 14.9% higher than that without these techniques and 28.9% higher than that in the prior work. The measured power loss is 8 mW (4.44%) under the maximum output power of 180 mW and with the PLSK data rate of 211 kbps. The proposed wireless battery charging system with a single pair of coils at the resonant frequency of 13.56 MHz is suitable for the applications of implantable medical devices.