Wireless Power Transfer and Management for Medical Applications: Wireless power

Wireless power transfer (WPT) plays an important role in medical devices that require contactless energy transfer for either direct powering or recharging their small batteries. Miniaturizing medical devices and improving their WPT link robustness against different variations (e.g., distance, alignment, and load changes) also demands an efficient and adaptive power-management IC (PMIC) to convert the incoming ac power carrier into one or multiple usable dc voltage supplies. This article summarizes the key techniques for WPT and PMIC design. It discusses different modalities for WPT, including inductive, ultrasonic, capacitive, and magnetoelectric (ME) methods, with a focus on their applicability in different types of medical devices with different dimensions, implantation depths, and power requirements. It is concluded that ultrasonic and ME modalities are suitable for WPT to deeply implanted small devices with low power consumption, while inductive and capacitive methods are more suitable for WPT to large implants with shorter depth and higher power consumption. This article also summarizes different PMIC techniques for inductive WPT, particularly conventional voltage mode and more recent current-mode (and reconfigurable) techniques, with an emphasis on their suitability for different input voltage and loading conditions.