用于生物电阻抗检测的恒流源电路研究  

Study on Constant Current Source Characteristics Based on Bioelectrical Impedance Detection Technology

作　　者：宁可庆[1] 尹晓亮 NING Keqing;YIN Xiaoliang(College of Information Science,North China University of Technology,Beijing 100043,China)

机构地区：[1]北方工业大学信息学院,北京100043

出　　处：《通信电源技术》2022年第12期43-46,共4页Telecom Power Technology

摘　　要：生物电阻抗技术是通过电学方法测量人体水分来提取人体的生物电阻抗信息,并根据这些信息来反映人体成分。在对人体的生物电阻抗进行检测时,检测结果通常会受人体皮肤表面的温度、湿度或破损情况等多种因素的影响而出现失真。针对因接触阻抗值不稳定会影响测量结果的问题,设计检测核心环节恒流源电路时,在消除输出信号直流分量的前提下尽可能提高恒流源的输出阻抗。尤其在高频情况下,保证其具有一定的输出阻抗,以此来消除接触阻抗所带来的干扰。在恒流源的设计实现上,采用现场可编程逻辑门阵列(Field Programmable Gate Array,FPGA)生成一个直接数字式频率合成器(Direct Digital Frequency Synthesis,DDS)信号,利用数模转换器(Digital to Analog Converter,DAC)模块将其转换成电压信号接入压控电流源电路中。压控电流源电路以差分接收放大器为核心,在其差分输入端加入直流电位的补偿回路,以此消除直流分量。在输出端加入屏蔽驱动电路,来提高电路的抗干扰能力。为了满足测量人体阻抗的需求,通过对比压控电流源电路在不同输入电压下的输出电流理论值与实际值的线性度来验证电路可行性,并根据实验所测得的输出阻抗与增益电阻和频率的关系来选择合适的电路参数。经过实验验证,在放大器的反馈输入端接入AD8066运算放大器可以有效防止反馈分流,从而提高整体电路的输出阻抗。同时随着电路中增益的不同,输出阻抗值也会随着频率的变化而变化。Bioelectrical impedance technology is to extract the bioelectrical impedance information of the human body by measuring the water content of the human body by electrical methods,and reflect the body composition according to this information.When detecting the bioelectrical impedance of the human body,the detection results are usually distorted by various factors such as the temperature,humidity or damage of the human skin surface.Aiming at the problem that the unstable contact impedance value will affect the measurement results,when designing the constant current source circuit of the core link of the detection,the output impedance of the constant current source should be increased as much as possible on the premise of eliminating the DC component of the output signal.Especially in the case of high frequency,ensure that it has a certain output impedance,so as to eliminate the interference caused by the contact impedance.In the design and implementation of the constant current source,a Field Programmable Gate Array(FPGA)is used to generate a Direct Digital Frequency Synthesis(DDS)signal.Digital to Analog Converter(DAC)module converts it into a voltage signal and connects it to the voltage-controlled current source circuit.The voltage-controlled current source circuit takes the differential receiver amplifier as the core,and adds a DC potential compensation loop at the differential input end to eliminate the DC component.A shielding drive circuit is added at the output end to improve the anti-interference ability of the circuit.In order to meet the needs of measuring human body impedance,the feasibility of the circuit is verified by comparing the linearity between the theoretical value and the actual value of the output current of the voltage-controlled current source circuit under different input voltages.The appropriate circuit parameters are selected according to the relationship between the output impedance and the gain resistance and the frequenay measured in the experiment.It has been verified by experiments

关 键 词：生物电阻抗 恒流源 电压控电流源 输出阻抗 差分放大器 

分 类 号：TN402[电子电信—微电子学与固体电子学]