Experimental result on wireless power management microsystem for endoscopic capsule robot

This paper presents a customized wireless power management microsystem for endoscopic capsule robot. The microsystem is composed of a rectifier, a regulator, a battery charger and a low dropout (LDO) regulator. The electromagnetic energy signal received from a self-resonant coil is rectified and then regulated to generate a stable DC voltage for charging the Li-ion battery. Stable DC voltage is provided for driving the capsule robot using the LDO regulator. The microsystem was fabricated in 0.18-μm CMOS high voltage process with a die size of 2.4mm*1mm. The microsystem was evaluated in details, and the test results suggest that the microsystem works as intended. The rectifier achieves the peak voltage conversion efficiency of 79.3% with a input of 4.48V sinusoidal voltage@3MHz. The charger circuit can charge the battery with a constant current of 10mA, and auto-control the switching of charge and discharge state. The regulator and LDO provide accurate output voltage in spite of the variations of input voltage and load current.