Study Of Wireless Energy Management Microsystem Of Active Capsule Endoscopy For Medical Application

With the change of people's diet structure and living rhythm, the probability of gastrointestinal diseases has significantly increased. Nowadays, inspection and therapy of these diseases are more inclined to non-invasive or minimally invasive ways, forcing us to improve medical instruments. This thesis introduces our research results on the energy management microsystem for active capsule endoscopy, an important part of autonomous driving and control technology for gastrointestinal capsule robot supported by a "863" project. Our aim is to solve the problem of inadequate energy supply for active capsule endoscopy.This research status and trend of the capsule endoscope technology are briefly reviewed at the beginning of this thesis, following an analysis of the bottleneck obstructing the progress of capsule endoscope. The research aim of this thesis is then introduced, namely, study of an energy management microsystem for active capsule endoscope based on the wireless energy transmission technology. A custom-made small Li-ion rechargeable battery is adopted since the outside-provided energy cannot satisfy the driving-control system. The driving and control of capsule endoscope can be realized by charging and discharging the battery using the energy management system. Based on the testing and a full understanding of the battery's charging and discharging characteristics, we propose the design aim and performance parameters of the wireless energy management microsystem and its components (including rectifier circuit, two LDOs and charging management circuit). According to these parameters, various unit circuits are designed and simulated at the transistor level. The layout and further validation of each circuit module are then discussed by Cadence Virtuoso and Calibre.The microsystem chip designed under SMIC 0.18μm 3.3V CMOS lp6M process has an area of 1000μm×2400μm, and successfully passes the joint testing of the energy coil and the control-driving system of capsule robot. Testing results indicate that the designed energy management microsystem can fulfill AC to DC conversion. Under a current load of 12 mA and an output voltage of 4.5 V, the voltage conversion efficiency of the rectifier filter circuit reaches 77.8%. The charging circuit can realize the voltage control from 3.175 V to 4.275 V for charge-discharge switch, showing quite good charging and discharging management. Circuit testing results of two LDOs prove that they can meet the specific application requirements. The capsule can realize two-direction acceleration during testing when LDO2 is connected to the driving system of capsule endoscopy, suggesting that the power provided by the LDO should be feasible in practical applications.