Hanyang University Team Develops High-Efficiency Wireless Charging IC for Medical Devices

Researchers at Hanyang University have developed a groundbreaking single-stage wireless pulse charging integrated circuit (IC) designed to significantly improve battery charging for implantable medical devices and wearable technology. Led by Professor Lee Byung-hoon of the Department of Electrical and Biomedical Engineering, the team's innovation addresses key limitations of current wireless charging systems.

Existing wireless charging circuits often require multiple power stages, leading to reduced efficiency and increased complexity. Furthermore, conventional constant current-constant voltage (CC-CV) charging methods struggle with accurate charge termination due to battery internal resistance, risking overcharging or incomplete charging and prolonging charging times. This is particularly problematic for implantable devices, where battery replacement necessitates additional surgical procedures.

The Hanyang University team's proposed 'single-stage wireless pulse charger' integrates AC-DC conversion and battery charging control into a single stage. It directly converts wirelessly transmitted power into a pulsed charging current, alternating between charging and non-charging intervals. Crucially, during the non-charging intervals, the circuit can directly sense the actual battery cell voltage without the voltage drop caused by internal resistance. This bypasses the need for complex analog-to-digital converters or intricate digital processing circuits.

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This research is significant because it integrates wireless power transfer circuit and battery charging control functions into a single power stage, while simultaneously implementing battery internal resistance compensation and accurate charge termination.

This novel approach not only compensates for battery internal resistance but also reduces charging time and enables more precise charge termination. The pulse charging method also helps mitigate lithium plating by allowing ion diffusion time within the battery electrodes. Tested using a 180nm BCD process, the IC achieved a high reception efficiency of 92.6% under a 6.78MHz wireless power transfer environment. In an in-vitro experiment simulating biological conditions with 5mm of pork tissue between the coils, it demonstrated a remarkable overall wireless power transfer efficiency of 44.4%, proving its stability in challenging environments.

Professor Lee Byung-hoon highlighted the significance of integrating wireless power transfer and battery charging control into a single stage while achieving robust internal resistance compensation and accurate charge termination. He anticipates the technology's broad application in areas requiring stable and efficient charging, such as implantable medical devices, wearable healthcare devices, and small wireless sensors, potentially enhancing patient care and device longevity.

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In the future, it is expected to be utilized in various application fields where battery stability and charging efficiency are important, such as implantable medical devices, wearable healthcare devices, and small wireless sensors.