Inductive charging of an EDLC powered wristband device for medical measurements

Electronic devices for measuring body parameters in healthcare environments generally exhibit hygienic problems. Furthermore, they require regular battery replacement or recharging. This paper presents an electronic wristband for medical measurements that can be charged wirelessly. Its power supply is equipped with a Qi compatible inductive power receiver, an Electrochemical Double-Layer Capacitor (EDLC) energy buffer and a series of voltage regulators that can be disconnected from the energy buffer by a microcontroller. Because the wireless power receiver was placed behind a display, a study was performed of the effects of the display on receiver coil characteristics and system performance. For the selection of the EDLC, a selection process is presented, making a tradeoff between device autonomy and charging time. The result is a completely sealable and thus sterilizable device that can be charged in less than 5 seconds while being worn on the wrist.