An ECG Readout Circuit Based On Audio Energy Harvesting

With the development of the Internet,smart home based on the Internet of things,intelligent medical care,e-commerce shopping and other fields are also on the rise.Today,the Internet of things technology has gradually become the direction and focus of future development.In the medical field,in order to enable doctors to quickly grasp patient data,the Internet and medical equipment interconnection of wearable medical monitoring system was born.Wearable medical monitoring system plays a very important role in health management and medical monitoring of children,the elderly and patients with chronic diseases.In the wearable medical monitoring system,the accuracy of analog signal acquisition and processing circuit is very important,because the accuracy of acquisition determines the diagnostic efficiency of doctors.Therefore,this puts forward the design requirements of low offset voltage,low power consumption,low noise and high common mode rejection ratio for the analog front-end instrument amplifier.Based on GF.18 um technology,an ECG readout circuit based on audio energy acquisition is designed in this paper,including charge pump structure Dixon ACDC rectifier and chopper instrument amplifier.The rectifier adopts the structure of Dixon rectifier,in which the comparator adopts the structure of unbalanced current bias to offset the offset voltage of the comparator itself,so as to reduce the reverse leakage current of the comparator and improve the energy collection efficiency of the Dixon rectifier.The rectifier can convert the AC audio energy into a stable DC voltage with low ripple and then use this voltage as the power supply for the ECG readout circuit.This design adopts chopping technology to reduce the offset voltage and equivalent input reference noise of the amplifier.At the same time,in order to further achieve the requirements of low power consumption of the instrument amplifier,the instrument amplifier structure adopted in this design is the sub-threshold current amplifier structure.The differential input of the amplifier of this structure works in the sub-threshold region,so it consumes only a small amount of static current,which meets the low power consumption requirements of the instrument amplifier.The simulation results show that the audio energy acquisition circuit can convert the AC signal of 500 m V into a stable DC signal of 1.2V.Under the supply voltage of 1.2V,the static current consumed by the chopper instrument amplifier is 200 u A,and the gain is 39.95 d B in the bandwidth range of 0.1Hz～200Hz.The common mode rejection ratio is 103 d B and the power supply rejection ratio is 74 d B.The equivalent input integral noise within the 1～200Hz bandwidth is 8.9μVrms.