CN116430100A - Weak current sensor signal processing circuit based on TMR - Google Patents
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Abstract
Description
技术领域technical field
本发明属于电流传感器领域，更具体地，涉及一种基于隧穿磁阻效应的微弱电流传感器信号处理电路。The invention belongs to the field of current sensors, and more specifically relates to a weak current sensor signal processing circuit based on the tunneling magnetoresistance effect.
背景技术Background technique
电流传感器是现代传感器产业的一个重要分支，随着科学技术的稳步快速发展，信息数据的获取在如今互联网信息化时代具有十分重要的意义。特别是对于微弱信号的获取，虽然在获取的过程中存在较大的难度，但在实际应用中具有较大的价值。近些年来，微弱电流的检测在信号处理、测量技术、通讯技术、信息技术等领域得到较为广泛的应用，并极大促进了相关领域的发展。Current sensors are an important branch of the modern sensor industry. With the steady and rapid development of science and technology, the acquisition of information data is of great significance in today's Internet information age. Especially for the acquisition of weak signals, although there is greater difficulty in the acquisition process, it has greater value in practical applications. In recent years, the detection of weak current has been widely used in signal processing, measurement technology, communication technology, information technology and other fields, and has greatly promoted the development of related fields.
电流传感器的研究可按照测量方式和测量原理去划分，其中按测量方式可分为接触式测量和非接触式测量；按测量原理可分为基于欧姆定律，基于安培环路定律和其他间接测量技术三大类。其中基于欧姆定律的分流器是唯一的一类接触式电流传感器，其他均为非接触式电流传感器。非接触式电流传感器按原理进行划分，其中基于安培环路定律的电流传感器又分为直接测量磁感应强度B和法拉第电磁感应定律测量两种方式。直接测量磁感应强度B的电流传感器有霍尔电流传感器、磁通门电流感器、磁电阻电流传感器；应用法拉第电磁感应定律的有罗氏线圈和电流互感器。其他间接测量技术电流传感器主要利用磁场与其他物理学原理或效应结合进行测量。这些电流传感器均有其各自最适合的应用场景。The research on current sensors can be divided according to the measurement method and measurement principle. According to the measurement method, it can be divided into contact measurement and non-contact measurement; according to the measurement principle, it can be divided into Ohm's law, Ampere's loop law and other indirect measurement techniques. Three categories. Among them, the shunt based on Ohm's law is the only type of contact current sensor, and the others are non-contact current sensors. The non-contact current sensor is divided according to the principle, and the current sensor based on the ampere loop law is divided into two methods: direct measurement of magnetic induction intensity B and measurement of Faraday's law of electromagnetic induction. Current sensors that directly measure the magnetic induction intensity B include Hall current sensors, fluxgate current sensors, and magnetoresistive current sensors; Rogowski coils and current transformers that apply Faraday's law of electromagnetic induction. Other indirect measurement techniques Current sensors primarily use magnetic fields in combination with other physical principles or effects for their measurements. Each of these current sensors has its own most suitable application scenarios.
基于欧姆定律的分流器属于接入式测量，其优点是成本低，应用方便；但它存在热稳定误差，并且测量时电流损耗大，无电气绝缘，存在安全问题且测量精度相对低。电流互感器分为交流电流互感器和直流电流互感器。交流电流互感器其优点是高稳定性和耐高击穿电压，但它不适合测量频率过高或过低的电流，会产生很大误差。直流电流互感器其缺点是被测电流不能过大以及结构不方便安装拆卸。罗氏线圈电流传感器不存在铁芯的饱和特性，无磁滞效应，优点是高耐击穿电压，体积小，价格低，容易安装，罗氏线圈尤其适合高频电流、大电流及瞬态电流的测量，但目前研制出的罗氏线圈电流传感器无法驱动一些常用的后继设备，同时也易受外界干扰磁场影响，这无疑限制了该传感器的应用。霍尔电流传感器开环结构的电流精度等级为1.0级，闭环结构具有更高的精度，精度等级为0.1级或更高。其限制是不适合测量过大或过小的电流，击穿电压低，并且闭环结构在测量大电流时，需要提高驱动电路的驱动能力。The shunt based on Ohm's law belongs to the access type measurement, which has the advantages of low cost and convenient application; but it has thermal stability error, and the current loss is large during measurement, there is no electrical insulation, there are safety problems and the measurement accuracy is relatively low. Current transformers are divided into AC current transformers and DC current transformers. The AC current transformer has the advantages of high stability and high breakdown voltage resistance, but it is not suitable for measuring currents with too high or too low frequency, which will cause large errors. The disadvantage of the DC current transformer is that the measured current cannot be too large and the structure is inconvenient to install and disassemble. The Rogowski coil current sensor does not have the saturation characteristic of the iron core and has no hysteresis effect. The advantages are high breakdown voltage, small size, low price, and easy installation. The Rogowski coil is especially suitable for the measurement of high-frequency current, large current and transient current. , but the currently developed Rogowski coil current sensor cannot drive some commonly used successor devices, and is also susceptible to external interference magnetic fields, which undoubtedly limits the application of the sensor. The current accuracy level of the open-loop structure of the Hall current sensor is 1.0, and the closed-loop structure has higher accuracy, and the accuracy level is 0.1 or higher. Its limitation is that it is not suitable for measuring too large or too small current, the breakdown voltage is low, and the closed-loop structure needs to improve the driving ability of the driving circuit when measuring large current.
以上电流传感器由于各自缺陷的限制，均不适用于微弱电流测量的研究。下面针对微弱电流的研究对剩下几类传感器进行说明。首先磁通门电流传感器的应用相对成熟，其在测量微弱电流的应用上也较为广泛。磁通门电流传感器是利用被磁化铁体在饱和区域内的非线性电流来测量磁场，其结构包括磁芯，励磁线圈和感应线圈，根据需求不同，磁通门的结构多种多样。其电流测量范围为mA-A级别，分辨率在10uA-100uA。相对之前提到的传感器，精度有所提高，具有零点漂移低，分辨率和灵敏度高，带宽大，响应速度快等优点，但其成本高，不便安装且制作工艺复杂。Due to the limitations of their respective defects, the above current sensors are not suitable for the research of weak current measurement. The following research on weak currents will illustrate the remaining types of sensors. First of all, the application of fluxgate current sensor is relatively mature, and its application in measuring weak current is also relatively extensive. The fluxgate current sensor uses the nonlinear current of the magnetized iron body in the saturation region to measure the magnetic field. Its structure includes a magnetic core, an excitation coil and an induction coil. According to different requirements, the structure of the fluxgate is various. Its current measurement range is mA-A level, and the resolution is 10uA-100uA. Compared with the sensors mentioned above, the accuracy has been improved, and it has the advantages of low zero drift, high resolution and sensitivity, wide bandwidth, fast response speed, etc., but its cost is high, it is inconvenient to install and the manufacturing process is complicated.
伴随着磁阻效应的发现，基于磁阻效应的电流传感器也获得广泛的应用，其中包括基于各向异性磁阻电流(AMR)传感器，巨磁阻电流传感器(GMR)，基于隧穿磁阻效应电流传感器(TMR)三种类型。基于磁阻效应的电流传感器各方面性能都较之其他传感器有很大提升，应用更为广泛，非线性度低、线性范围宽、响应快，频率范围可达DC-1000kHz，但其存在温度漂移，零点漂移，以及功耗大等限制，需要对这些问题进行优化改进。如今AMR、GMR和TMR等几种类型的元件都在实际中得到了应用，特别是应用在电流传感器中。其中AMR、GMR等元件的灵敏度相对较高，但是线性范围不够。而TMR电流传感器则在实际应用中具备更为明显的优势，灵敏度也相对更高，并且在线性度上也相对更好。然而，如何通过合理的电路设计利用TMR电流传感器去实现对微弱电流的高精度测量仍面临一定挑战。Along with the discovery of the magnetoresistance effect, current sensors based on the magnetoresistance effect have also been widely used, including sensors based on anisotropic magnetoresistance (AMR) current sensors, giant magnetoresistance current sensors (GMR), and tunneling magnetoresistance effects. There are three types of current sensors (TMR). Compared with other sensors, the performance of the current sensor based on the magnetoresistive effect has been greatly improved in all aspects, and it is more widely used, with low nonlinearity, wide linear range, fast response, and the frequency range can reach DC-1000kHz, but it has temperature drift. , zero drift, and large power consumption constraints, these issues need to be optimized and improved. Several types of components such as AMR, GMR, and TMR are used in practice today, especially in current sensors. Among them, the sensitivity of AMR, GMR and other components is relatively high, but the linear range is not enough. The TMR current sensor has more obvious advantages in practical applications, relatively higher sensitivity, and relatively better linearity. However, how to use TMR current sensors to achieve high-precision measurement of weak currents through reasonable circuit design still faces certain challenges.
发明内容Contents of the invention
本发明的目的在于提供一种高精度、高灵敏度的基于TMR的微弱电流传感器信号处理电路。该电路包括电源电路模块、TMR电流传感器芯片、仪表放大电路、滤波电路、偏置调零电路、功率放大电路、反馈电路及采样电路等组成。待测微弱电流产生磁场，在外加聚磁环和反馈线圈的作用下，再经过电路处理部分实现闭环结构型测量，对信号进行提取、放大、滤波、采样等实现对待测电流的精确测量，同时闭环型结构也很大程度上减小了外界干扰因素对测量的影响，实现传感器对微弱电流测量的高精度和高灵敏度的测量要求。The purpose of the present invention is to provide a high-precision, high-sensitivity TMR-based weak current sensor signal processing circuit. The circuit includes a power circuit module, a TMR current sensor chip, an instrument amplifier circuit, a filter circuit, a bias zeroing circuit, a power amplifier circuit, a feedback circuit, and a sampling circuit. The weak current to be measured generates a magnetic field. Under the action of an external magnetic gathering ring and a feedback coil, the closed-loop structural measurement is realized through the circuit processing part, and the signal is extracted, amplified, filtered, and sampled to achieve accurate measurement of the current to be measured. At the same time The closed-loop structure also greatly reduces the influence of external interference factors on the measurement, and realizes the high-precision and high-sensitivity measurement requirements of the sensor for weak current measurement.
为实现上述目的，本发明的技术方案如下。To achieve the above object, the technical solution of the present invention is as follows.
一种基于TMR的微弱电流传感器信号处理电路，包括电源电路模块、偏置调零电路、TMR传感器芯片、仪表放大电路、滤波电路、功率放大电路、反馈电路及采样电路，所述电源电路模块分别与TMR传感器芯片和偏置调零电路电性连接，TMR传感器芯片和偏置调零电路均与仪表放大电路电性连接，仪表放大电路与滤波电路电性连接，滤波电路与功率放大电路电性连接，功率放大电路与反馈电路电性连接，反馈电路分别与采样电路和TMR传感器芯片电性连接；所述TMR传感器芯片用于对磁场信号进行收集与转化；所述电源电路模块能够实现从单极性电压到双极性电压的变换并满足供电稳定性；偏置调零电路是对TMR传感器芯片产生的偏置电压信号进行调零处理；仪表放大电路用于放大TMR电流传感器芯片的输出信号；滤波电路用于对信号进行滤波处理，排除杂散信号的干扰；功率放大电路用于对前端信号进行功率放大，以此来驱动反馈线圈的运行；反馈电路用于反馈电流的形成；采样电路用于对采样电阻电压的获取，间接获知反馈电流的大小。A weak current sensor signal processing circuit based on TMR, including a power circuit module, a bias zeroing circuit, a TMR sensor chip, an instrument amplifier circuit, a filter circuit, a power amplifier circuit, a feedback circuit and a sampling circuit, the power circuit modules are respectively It is electrically connected with the TMR sensor chip and the bias zero adjustment circuit, the TMR sensor chip and the bias zero adjustment circuit are electrically connected with the instrument amplifier circuit, the instrument amplifier circuit is electrically connected with the filter circuit, and the filter circuit is electrically connected with the power amplifier circuit connection, the power amplifier circuit is electrically connected with the feedback circuit, and the feedback circuit is electrically connected with the sampling circuit and the TMR sensor chip respectively; the TMR sensor chip is used to collect and transform the magnetic field signal; the power circuit module can realize The conversion of polar voltage to bipolar voltage meets the stability of power supply; the bias zeroing circuit is for zeroing the bias voltage signal generated by the TMR sensor chip; the instrument amplifier circuit is used to amplify the output signal of the TMR current sensor chip The filter circuit is used to filter the signal to eliminate the interference of stray signals; the power amplifier circuit is used to amplify the power of the front-end signal to drive the operation of the feedback coil; the feedback circuit is used to form the feedback current; the sampling circuit It is used to obtain the voltage of the sampling resistor and indirectly obtain the magnitude of the feedback current.
进一步地，电路的供电部分VCC和VEE部分均由外部电源提供，电源电路模块的集成芯片U6的1脚分别与电感L3和电容C26的一端连接，电感L3另一端分别与正电压端VCC和电容C25的一端连接，电容C25的另一端和集成芯片U6的2脚接地，电容C26的另一端与电容C27的一端连接，电容C27的另一端接地；集成芯片U6的6脚分别与电感L2和电容C21的一端连接，电容C21的另一端接地，电感L2的另一端分别与正电压端VCC和电容C22的一端连接，电容C22的另一端接地；集成芯片U6的4脚分别与电感L4和电容C23的一端连接，电容C23的另一端接地，电感L4的另一端分别与负电压端VEE和电容C24的一端连接，电容C24的另一端接地；集成芯片U6的5脚五接地。Furthermore, both the power supply part VCC and the VEE part of the circuit are provided by an external power supply,
进一步地，仪表放大电路包括前端放大电路和次级信号放大电路；滤波电路包括与前端放大电路连接的电阻R2、电容C3、电容C7、电阻R12和电容C9，以及与次级信号放大电路连接的电阻R19、电容C11、滤波电容C13、电阻R24和电容C15。Further, the instrument amplifying circuit includes a front-end amplifying circuit and a secondary signal amplifying circuit; the filter circuit includes a resistor R2 connected to the front-end amplifying circuit, a capacitor C3, a capacitor C7, a resistor R12 and a capacitor C9, and a secondary signal amplifying circuit connected Resistor R19, capacitor C11, filter capacitor C13, resistor R24 and capacitor C15.
进一步地，前端放大电路中，运算放大器U2A的3脚分别与电阻R2的一端、电容C3的一端和电容C7的一端连接，电阻R2的另一端与信号输入点SIGNAL1+连接，电容C3的另一端接地，电容C7的另一端与运算放大器U2B的5脚连接；运算放大器U2B的5脚还分别与电阻R12的一端和电容C9的一端连接，电容C9的另一端接地，电阻R12的另一端与信号输入点SIGNAL1-连接。运算放大器U2A的2脚分别与电阻R8和电阻R5的一端连接，电阻R5的另一端与信号输出点SIGNAL2+连接，同时，电阻R5上并联连接一电容C5；电阻R8的另一端分别与电阻R9的一端和运算放大器U2B的6脚连接，电阻R9的另一端与信号输出点SIGNAL2-连接，同时，电阻R9上并联连接一电容C8。运算放大器U2A的5脚串联电阻R1后与正电压端VCC连接，运算放大器U2A的1脚与信号输出点SIGNAL2+连接；运算放大器U2B的7脚与信号输出点SIGNAL2-连接。跟随器U3A的3脚分别与电阻R4和电阻R6的一端连接，电阻R4的另一端与信号输出点SIGNAL2+连接，电阻R6的另一端与信号输出点SIGNAL2-连接；跟随器U3A的2脚分别与稳压管Q1的3脚、稳压管Q2的2脚和信号输入点SIGNAL0连接，稳压管Q1的2脚与电容C1串联后接地，稳压管Q1的1脚分别与电阻R3和电阻R7的一端连接，电阻R3的另一端与电容C1连接，电阻R7的另一端分别与稳压管Q1的3脚和电阻R10的一端连接，稳压管Q1的3脚与稳压管Q2的2脚连接，电阻R10的另一端分别与电阻R11的一端和稳压管Q2的1脚连接，电阻R11的另一端分别与稳压管Q2的3脚、电容C10的一端、电阻R15的一端和运算放大器U2A的4脚连接；电容C10的另一端接地，电阻R15的另一端与负电压端VEE连接。跟随器U3A的1脚与信号输入点SIGNAL0连接；跟随器U3A的4脚分别与负电压端VEE和电容C6的一端连接，电容C6的另一端接地；跟随器U3A的5脚分别与正电压端VCC和电容C2的一端连接，电容C2的另一端接地；运算放大器U2B的4脚与电容C10连接，运算放大器U2B的8脚与电容C1连接。Further, in the front-end amplifier circuit, the 3 pins of the operational amplifier U2A are respectively connected to one end of the resistor R2, one end of the capacitor C3 and one end of the capacitor C7, the other end of the resistor R2 is connected to the signal input point SIGNAL1+, and the other end of the capacitor C3 is grounded , the other end of capacitor C7 is connected to
进一步地，次级信号放大电路中，集成芯片U4的1脚和8脚外并联一个可调电阻R17，用于对整个电路增益的设置；集成芯片U4的2脚分别与电容C11的一端、滤波电容C13的一端和电阻R19的一端连接，电阻R19的另一端与信号输出点SIGNAL2-连接，滤波电容C13的另一端接地；集成芯片U4的3脚分别与电容C15的一端、滤波电容C13的另一端和电阻R24的一端连接，电阻R24的另一端与信号输出点SIGNAL2+连接，电容C15的另一端接地；集成芯片U4的4脚分别与电阻R26的一端和电容C16的一端连接，电阻R26的另一端与-5V电源端连接，电容C16的另一端接地；集成芯片U4的5脚作为REF1引脚，REF1引脚与电阻R27串联后接地；集成芯片U4的7脚分别与电阻R22的一端和电容C14的一端连接，电阻R22的另一端与+5V电源端连接，电容C14的另一端接地；集成芯片U4的6脚为输出vout11。Further, in the secondary signal amplifying circuit, an adjustable resistor R17 is connected in parallel with
进一步地，偏置调零电路中，运算放大器U5A的5脚分别与电阻R21的一端和电容C12的一端连接，电容C12的另一端接地，电阻R21的另一端与可调电阻R20的调节端连接，可调电阻R20一端与电阻R16串联后接正电压端VCC，可调电阻R20的另一端与电阻R28串联后接负电压端VEE；同时，可调电阻R20外并联有串联连接的电阻R18和电阻R25。运算放大器U5A的6脚和7脚均与电阻R23串联后接集成芯片U4的REF1引脚。运算放大器U5A的8脚接正电压端VCC；运算放大器U5A的4脚接负电压端VEE。Furthermore, in the bias zeroing circuit,
进一步地，功率放大电路设有一运算放大器U6A，反馈电路包含反馈线圈J1和采样电阻R32；运算放大器U6A的3脚分别与电阻R29的一端和电容C29的一端连接，电容C29的另一端接地，电阻R29的另一端接入次级信号放大电路的输出vout11；运算放大器U6A的1脚和2脚均与电阻R30的一端连接，电阻R30的另一端与反馈线圈J1一端连接，反馈线圈J1的另一端与采样电阻R32一端连接，采样电阻R32另一端接地。运算放大器U6A的8脚分别与电容C17的一端和正电压端VCC连接，电容C17的另一端接地；运算放大器U6A的4脚分别与电容C19的一端和负电压端VEE连接，电容C19的另一端接地。Further, the power amplifying circuit is provided with an operational amplifier U6A, and the feedback circuit includes a feedback coil J1 and a sampling resistor R32;
进一步地，采样电路设有一运算放大器U7A，运算放大器U7A的5脚与电容C20的一端连接，电容C20的的另一端接地；运算放大器U7A的6脚分别与电阻R33和电阻R34的一端连接，电阻R34的另一端接地，电阻R33的另一端与测试端口J2的一端连接，运算放大器U7A的7脚也与与测试端口J2的一端连接，测试端口J2的的另一端接地。运算放大器U7A的8脚与正电压端VCC连接；运算放大器U7A的4脚与负电压端VEE连接。Further, the sampling circuit is provided with an operational amplifier U7A, the 5 pins of the operational amplifier U7A are connected to one end of the capacitor C20, and the other end of the capacitor C20 is grounded; the 6 pins of the operational amplifier U7A are respectively connected to one end of the resistor R33 and the resistor R34, and the resistor The other end of R34 is grounded, the other end of resistor R33 is connected to one end of test port J2,
本发明提供的TMR微弱电流传感器电路，通过对各模块的分析以及电路的设计，最大程度上符合各模块的功能要求，并且实现各电路模块连接后功能的需求满足。待测微弱电流产生磁场，在外加聚磁环和反馈线圈的作用下，再经过电路处理部分实现闭环结构型测量，对信号进行提取、放大、滤波、采样等实现对待测电流的精确测量，闭环型结构也很大程度上减小了外界干扰因素对测量的影响，实现传感器对微弱电流测量的高精度和高灵敏度的测量要求；本发明为TMR传感器在微弱电流测量的电路结构设计以及如何通过电路设计实现低误差、高灵敏度的TMR微弱电流传感器设计提供一种解决方案。The TMR weak current sensor circuit provided by the present invention meets the functional requirements of each module to the greatest extent through the analysis of each module and the design of the circuit, and realizes that the functional requirements of each circuit module after connection are met. The weak current to be measured generates a magnetic field. Under the action of an external magnetic gathering ring and a feedback coil, the closed-loop structural measurement is realized through the circuit processing part, and the signal is extracted, amplified, filtered, and sampled to achieve accurate measurement of the current to be measured. Closed-loop The type structure also greatly reduces the influence of external interference factors on the measurement, and realizes the measurement requirements of high precision and high sensitivity of the sensor for weak current measurement; the invention is the circuit structure design of the TMR sensor for weak current measurement and how The circuit design realizes the design of TMR weak current sensor with low error and high sensitivity to provide a solution.
该TMR微弱电流传感器电路部分设计方案为解决TMR传感器在微弱电流测量上的应用提供了参考，针对闭环结构型的TMR电流传感器设计的传感器系统原理框图，通过对各模块的分析以及电路的设计，最大程度上符合各模块的功能要求，并且实现各电路模块连接后功能的需求满足。本发明关键是对电源供电模块隔离电源的应用以及仪表放大部分电路的设计，以及通过电路的设计及芯片选型尽可能满足对TMR微弱电流传感器的高灵敏度性能的设计要求。The design scheme of the TMR weak current sensor circuit part provides a reference for solving the application of TMR sensor in weak current measurement. The sensor system block diagram designed for the closed-loop structure type TMR current sensor, through the analysis of each module and the design of the circuit, The functional requirements of each module are met to the greatest extent, and the requirements for realizing the functions after connection of each circuit module are met. The key of the present invention is the application of the isolated power supply of the power supply module and the design of the circuit of the instrument amplification part, and the design requirements of the high sensitivity performance of the TMR weak current sensor can be satisfied as much as possible through the design of the circuit and the selection of the chip.
附图说明Description of drawings
图1为本发明的闭环结构型TMR微弱电流传感器信号处理系统原理框图示意图。FIG. 1 is a schematic block diagram of the signal processing system of the closed-loop structure type TMR weak current sensor of the present invention.
图2为本发明信号处理电路的电源电路模块的单极性电压转换为双极性电压电路示意图。FIG. 2 is a schematic diagram of a circuit for converting unipolar voltage to bipolar voltage in the power circuit module of the signal processing circuit of the present invention.
图3为本发明基于TMR的微弱电流传感器信号处理电路的前端放大电路示意图。FIG. 3 is a schematic diagram of the front-end amplification circuit of the TMR-based weak current sensor signal processing circuit of the present invention.
图4为本发明基于TMR的微弱电流传感器信号处理电路的次级信号放大电路示意图。FIG. 4 is a schematic diagram of a secondary signal amplification circuit of the TMR-based weak current sensor signal processing circuit of the present invention.
图5为本发明基于TMR的微弱电流传感器信号处理电路的偏置调零电路示意图。FIG. 5 is a schematic diagram of a bias zeroing circuit of the TMR-based weak current sensor signal processing circuit of the present invention.
图6为本发明基于TMR的微弱电流传感器信号处理电路的运放驱动电路和反馈电路示意图。FIG. 6 is a schematic diagram of an operational amplifier drive circuit and a feedback circuit of the TMR-based weak current sensor signal processing circuit of the present invention.
图7为本发明基于TMR的微弱电流传感器信号处理电路的采样电路示意图。FIG. 7 is a schematic diagram of a sampling circuit of the TMR-based weak current sensor signal processing circuit of the present invention.
具体实施方式Detailed ways
为了能够更清楚地理解本发明的上述目的、特征和优点，下面结合附图和具体实施方式对本发明进行进一步的详细描述。在下面的描述中阐述了很多具体细节以便于充分理解本发明，但是，本发明还可以采用其他不同于在此描述的其他方式来实施，因此，本发明并不限于下面公开的具体实施例的限制。In order to understand the above-mentioned purpose, features and advantages of the present invention more clearly, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. In the following description, many specific details are set forth in order to fully understand the present invention, but the present invention can also be implemented in other ways different from those described here, therefore, the present invention is not limited to the specific embodiments disclosed below limit.
本发明提供一种基于TMR的微弱电流传感器信号处理电路，如图1所示，该电路包括电源电路模块、TMR电流传感器芯片、仪表放大电路、滤波电路、偏置调零电路、功率放大电路、反馈电路及采样电路。电源是电路中非常重要的部分，TMR芯片的正常工作离不开供电，其他部分处理电路所需的芯片也离不开供电，而高精度测量的芯片又对供电电压的稳定性要求比较高，电源性能的优劣直接影响整个电路的性能，电源模块的设计即要考虑电源供电的稳定性，还要考虑电源端对后续处理电路的干扰问题。TMR电流传感器芯片的选择则需要结合所设计传感器对灵敏度、本底噪声和敏感轴等方面的要求去考虑，同时芯片的尺寸涉及到磁环间隙尺寸的设计，也会影响到所设计传感器的灵敏度，因此也在考虑的范畴。The present invention provides a weak current sensor signal processing circuit based on TMR. As shown in FIG. Feedback circuit and sampling circuit. The power supply is a very important part of the circuit. The normal operation of the TMR chip is inseparable from the power supply, and the chips required for other parts of the processing circuit are also inseparable from the power supply. The chip for high-precision measurement has relatively high requirements for the stability of the power supply voltage. The performance of the power supply directly affects the performance of the entire circuit. The design of the power module should not only consider the stability of the power supply, but also consider the interference of the power supply terminal to the subsequent processing circuit. The selection of the TMR current sensor chip needs to be considered in combination with the requirements of the designed sensor on sensitivity, background noise and sensitive axis. At the same time, the size of the chip involves the design of the gap size of the magnetic ring, which will also affect the sensitivity of the designed sensor. , and therefore are also considered in the category.
仪表放大电路主要起到对TMR电流传感器芯片输出信号的放大作用。滤波电路主要是对信号的滤波处理，排除杂散信号的干扰，也决定传感器频率范围和带宽的确定。由于TMR芯片内部采用电桥结构，受自身工艺限制，TMR芯片内部四个电阻初始值不可能保证完全一致，同时受周围杂散磁场等影响，TMR芯片存在固定输出偏置电压，会对输出结果会造成影响，因此本发明设计偏置调零电路，以抵消其固有偏置。功率放大电路主要是考虑到闭环型TMR电流传感器结构会涉及到反馈线圈，需要前端的输出信号能驱动线圈，同时反馈电路主要也是反馈线圈以及采样电阻的串联再接地的形式，主要涉及到线圈匝数及采样电阻阻值的选取。The instrument amplifier circuit mainly plays the role of amplifying the output signal of the TMR current sensor chip. The filter circuit is mainly to filter the signal, eliminate the interference of stray signals, and also determine the frequency range and bandwidth of the sensor. Due to the internal bridge structure of the TMR chip, limited by its own technology, the initial values of the four resistors inside the TMR chip cannot be guaranteed to be completely consistent. At the same time, due to the influence of surrounding stray magnetic fields, the TMR chip has a fixed output bias voltage, which will affect the output will cause an impact, so the present invention designs a bias zeroing circuit to offset its inherent bias. The power amplifier circuit mainly considers that the closed-loop TMR current sensor structure will involve the feedback coil, and the output signal of the front-end needs to be able to drive the coil. At the same time, the feedback circuit is mainly in the form of the feedback coil and the sampling resistor connected in series and then grounded, mainly involving the coil turns. The selection of the number and the resistance value of the sampling resistor.
图2为电源电路模块的单极性电压转换为双极性电压电路示意图，其中U6是适用于输入电源的电压比较稳定、输入输出之间要求隔离、对输出电压稳定度和纹波噪声要求不高的电路设计场合的一款集成芯片。本实施例中，集成芯片U6用到的芯片型号为A2409S-2WR3，该芯片为定电压输入，隔离非稳压正负双路输出，有可持续短路保护，功率密度高。为进一步减小输入输出纹波，在集成芯片U6的输入输出端各连接有一个合适的电容滤波网络，实现滤波减小纹波干扰，实现从单极性电压到双极性电压的变换并满足供电稳定性。Figure 2 is a schematic diagram of the unipolar voltage conversion to bipolar voltage circuit of the power circuit module, in which U6 is suitable for relatively stable input power voltage, isolation between input and output, and high requirements for output voltage stability and ripple noise. An integrated chip for high circuit design occasions. In this embodiment, the chip type used in the integrated chip U6 is A2409S-2WR3. This chip has a constant voltage input, an isolated unstabilized positive and negative dual outputs, sustainable short-circuit protection, and high power density. In order to further reduce the input and output ripple, a suitable capacitor filter network is connected to the input and output terminals of the integrated chip U6 to realize filtering and reduce ripple interference, realize the transformation from unipolar voltage to bipolar voltage and satisfy Power supply stability.
如图2所示，电路的供电部分VCC和VEE部分均由外部电源提供，电源电路模块的集成芯片U6的1脚分别与电感L3和电容C26的一端连接，电感L3另一端分别与正电压端VCC和电容C25的一端连接，电容C25的另一端和集成芯片U6的2脚接地，电容C26的另一端与电容C27的一端连接，电容C27的另一端接地；集成芯片U6的6脚分别与电感L2和电容C21的一端连接，电容C21的另一端接地，电感L2的另一端分别与正电压端VCC和电容C22的一端连接，电容C22的另一端接地；集成芯片U6的4脚分别与电感L4和电容C23的一端连接，电容C23的另一端接地，电感L4的另一端分别与负电压端VEE和电容C24的一端连接，电容C24的另一端接地；集成芯片U6的5脚接地。集成芯片U6一侧的电感L3与电容C25构成简易的滤波电路，集成芯片U6的输出端部分也设有一个滤波网络，共同滤波减小纹波干扰，提升供电稳定性。As shown in Figure 2, the power supply part of the circuit, VCC and VEE, are provided by an external power supply.
本实施例中，仪表放大电路包括前端放大电路和次级信号放大电路。滤波电路包括与前端放大电路连接的电阻R2、电容C3、电容C7、电阻R12和电容C9，以及与次级信号放大电路连接的电阻R19、电容C11、滤波电容C13、电阻R24和电容C15。In this embodiment, the instrument amplifying circuit includes a front-end amplifying circuit and a secondary signal amplifying circuit. The filter circuit includes resistor R2, capacitor C3, capacitor C7, resistor R12 and capacitor C9 connected to the front-end amplifier circuit, and resistor R19, capacitor C11, filter capacitor C13, resistor R24 and capacitor C15 connected to the secondary signal amplifier circuit.
图3为前端放大电路示意图，前端放大电路包括运算放大器U2A、运算放大器U2B、跟随器U3A。采用浮地共模自举设计，目的是提高共模抑制比。如果运算放大器U2A、运算放大器U2B的正负电源的公共参考点不接地，而把它接到与共模电压等电位点，这样对于运算放大器U2A、运算放大器U2B而言，输出的共模信号就为零，从而消除共模干扰。根据这一思路，本实施例中，两端输入信号SIGNAL1+和SIGNAL1-分别通过电阻R2、电容C3组成简易的滤波电路和电阻R12、电容C9组成的简易滤波电路进行滤波后，通过运算放大器U2A和U2B进行信号放大，在此基础上，运算放大器U2A、运算放大器U2B的电源分别由稳压管Q1、稳压管Q2获取提供供电，将公共参考点进行浮置处理，与跟随器U3A的输出点连接。输入信号在SIGNAL1+、SIGNAL1-两点上产生的共模电压经跟随器U3A接到浮动电源中心点，使电源电压随共模电压一起变化，从而抵消共模信号，加大了电路的共模信号抑制比。同时将Shield0信号作为输入电极线的屏蔽层，达到共模驱动的目的。其中，运算放大器U2A、运算放大器U2B、跟随器U3A均采用TLC2272芯片。FIG. 3 is a schematic diagram of a front-end amplification circuit, which includes an operational amplifier U2A, an operational amplifier U2B, and a follower U3A. The floating common-mode bootstrap design is adopted to improve the common-mode rejection ratio. If the common reference point of the positive and negative power supplies of operational amplifier U2A and operational amplifier U2B is not grounded, but connected to the same potential point as the common-mode voltage, then for operational amplifier U2A and operational amplifier U2B, the output common-mode signal is zero, thereby eliminating common-mode interference. According to this idea, in this embodiment, the input signals SIGNAL1+ and SIGNAL1- at both ends are respectively filtered through a simple filter circuit composed of a resistor R2 and a capacitor C3 and a simple filter circuit composed of a resistor R12 and a capacitor C9, and then passed through the operational amplifier U2A and U2B performs signal amplification. On this basis, the power supply of the operational amplifier U2A and operational amplifier U2B is respectively obtained by the voltage regulator tube Q1 and the voltage regulator tube Q2 to provide power supply, and the common reference point is floated, and the output point of the follower U3A connect. The common-mode voltage generated by the input signal at SIGNAL1+ and SIGNAL1- is connected to the center point of the floating power supply through the follower U3A, so that the power supply voltage changes with the common-mode voltage, thereby canceling the common-mode signal and increasing the common-mode signal of the circuit Inhibition ratio. At the same time, the Shield0 signal is used as the shielding layer of the input electrode line to achieve the purpose of common mode driving. Among them, operational amplifier U2A, operational amplifier U2B, and follower U3A all adopt TLC2272 chip.
如图3所示，前端放大电路中，运算放大器U2A的3脚分别与电阻R2的一端、电容C3的一端和电容C7的一端连接，电阻R2的另一端与信号输入点SIGNAL1+连接，电容C3的另一端接地，电容C7的另一端与运算放大器U2B的5脚连接；运算放大器U2B的5脚还分别与电阻R12的一端和电容C9的一端连接，电容C9的另一端接地，电阻R12的另一端与信号输入点SIGNAL1-连接。运算放大器U2A的2脚分别与电阻R8和电阻R5的一端连接，电阻R5的另一端与信号输出点SIGNAL2+连接，同时，电阻R5上并联连接一电容C5；电阻R8的另一端分别与电阻R9的一端和运算放大器U2B的6脚连接，电阻R9的另一端与信号输出点SIGNAL2-连接，同时，电阻R9上并联连接一电容C8。运算放大器U2A的5脚串联电阻R1后与正电压端VCC连接，运算放大器U2A的1脚与信号输出点SIGNAL2+连接；运算放大器U2B的7脚与信号输出点SIGNAL2-连接。跟随器U3A的3脚分别与电阻R4和电阻R6的一端连接，电阻R4的另一端与信号输出点SIGNAL2+连接，电阻R6的另一端与信号输出点SIGNAL2-连接；跟随器U3A的2脚分别与稳压管Q1的3脚、稳压管Q2的2脚和信号输入点SIGNAL0连接，稳压管Q1的2脚与电容C1串联后接地，稳压管Q1的1脚分别与电阻R3和电阻R7的一端连接，电阻R3的另一端与电容C1连接，电阻R7的另一端分别与稳压管Q1的3脚和电阻R10的一端连接，稳压管Q1的3脚与稳压管Q2的2脚连接，电阻R10的另一端分别与电阻R11的一端和稳压管Q2的1脚连接，电阻R11的另一端分别与稳压管Q2的3脚、电容C10的一端、电阻R15的一端和运算放大器U2A的4脚连接；电容C10的另一端接地，电阻R15的另一端与负电压端VEE连接。跟随器U3A的1脚与信号输入点SIGNAL0连接；跟随器U3A的4脚分别与负电压端VEE和电容C6的一端连接，电容C6的另一端接地；跟随器U3A的5脚分别与正电压端VCC和电容C2的一端连接，电容C2的另一端接地。运算放大器U2B的4脚与电容C10连接，运算放大器U2B的8脚与电容C1连接。其中，SIGNAL1+、SIGNAL1-均为与TMR传感器芯片输出差分电压信号的接入点，SIGNAL0为与屏蔽线相连接的接入点。As shown in Figure 3, in the front-end amplifier circuit, the 3 pins of the operational amplifier U2A are respectively connected to one end of the resistor R2, one end of the capacitor C3 and one end of the capacitor C7, the other end of the resistor R2 is connected to the signal input point SIGNAL1+, and the capacitor C3 The other end is grounded, the other end of capacitor C7 is connected to pin 5 of operational amplifier U2B; pin 5 of operational amplifier U2B is also connected to one end of resistor R12 and one end of capacitor C9, the other end of capacitor C9 is grounded, and the other end of resistor R12 Connect with the signal input point SIGNAL1-. The 2 pins of the operational amplifier U2A are respectively connected to one end of the resistor R8 and the resistor R5, the other end of the resistor R5 is connected to the signal output point SIGNAL2+, and at the same time, a capacitor C5 is connected in parallel to the resistor R5; the other end of the resistor R8 is respectively connected to the resistor R9 One end is connected to pin 6 of the operational amplifier U2B, the other end of the resistor R9 is connected to the signal output point SIGNAL2-, and at the same time, a capacitor C8 is connected in parallel to the resistor R9. The 5-pin of the operational amplifier U2A is connected in series with the resistor R1 to the positive voltage terminal VCC, the 1-pin of the operational amplifier U2A is connected to the signal output point SIGNAL2+; the 7-pin of the operational amplifier U2B is connected to the signal output point SIGNAL2-. The 3 pins of the follower U3A are respectively connected to one end of the resistor R4 and the resistor R6, the other end of the resistor R4 is connected to the signal output point SIGNAL2+, and the other end of the resistor R6 is connected to the signal output point SIGNAL2-; the 2 pins of the follower U3A are respectively connected to Pin 3 of voltage regulator tube Q1, pin 2 of voltage regulator tube Q2 are connected to signal input point SIGNAL0, pin 2 of voltage regulator tube Q1 is connected in series with capacitor C1 and then grounded, pin 1 of voltage regulator tube Q1 is connected to resistor R3 and resistor R7 respectively One end of the resistor R3 is connected to the capacitor C1, the other end of the resistor R7 is respectively connected to the pin 3 of the regulator tube Q1 and one end of the resistor R10, and the pin 3 of the regulator tube Q1 is connected to the pin 2 of the regulator tube Q2 Connection, the other end of the resistor R10 is respectively connected with one end of the resistor R11 and pin 1 of the voltage regulator tube Q2, and the other end of the resistor R11 is connected with the pin 3 of the voltage regulator tube Q2, one end of the capacitor C10, one end of the resistor R15 and the operational amplifier The 4 pins of U2A are connected; the other end of the capacitor C10 is grounded, and the other end of the resistor R15 is connected to the negative voltage terminal VEE.
其中电阻R2和电容C3以及电阻R12和电容C9都起着简易滤波小电路的作用，对信号作初步滤波处理；电容C7主要用来消除差模信号干扰；运算放大器U2A和运算放大器U2B构成对信号的放大的作用；稳压管Q1,稳压管Q2与电阻R3,电阻R7,电阻R10,电阻R11组成的结构主要是用来向运算放大器U2A和运算放大器U2B两运放提供稳定的电压输入；电阻R1和电容C1、以及电阻R15和电容C10是对外接供电电源作滤波处理；跟随器U3A外加电容C2,电容C6构成电压跟随电路，用以信号的传输。Among them, the resistor R2 and the capacitor C3, as well as the resistor R12 and the capacitor C9 all play the role of a simple filter circuit, and perform preliminary filter processing on the signal; the capacitor C7 is mainly used to eliminate the interference of the differential mode signal; the operational amplifier U2A and the operational amplifier U2B form a pair of signal The function of amplification; the structure composed of voltage regulator tube Q1, voltage regulator tube Q2 and resistor R3, resistor R7, resistor R10, and resistor R11 is mainly used to provide stable voltage input to the operational amplifier U2A and operational amplifier U2B; Resistor R1 and capacitor C1, as well as resistor R15 and capacitor C10 are used for filtering the external power supply; follower U3A adds capacitor C2 and capacitor C6 to form a voltage follower circuit for signal transmission.
图4为次级信号放大电路示意图，由于前端放大电路中的信号放大倍数不宜设置得过大，因此需对信号再次放大。其中U4为集成芯片，REF1引脚为基准引脚，用来进行偏置调零电路的设计的预留接口。根据运放的虚断、虚短原则，电路的增益G由R16和R27两电阻共同决定，可根据实际需要调节信号放大倍数。前端外围电路中的电阻R19、电容C11与电阻R24、电容C15为针对两端共模信号干扰的滤波电路，而滤波电容C13则可有效抑制差模信号的干扰。集成芯片U4选用AD620AR集成芯片，供电电压设定为±5V，其中REF1引脚为基准引脚，用来预留偏置调零电路的接入。电路增益G由可调电阻R17决定，G＝49.4K/R17+1，放大倍数据需求而调。前端外围电路中的电阻R19和电容C11与电阻R24和电容C15组成的滤波电路能够滤除次级信号放大电路两端的共模信号干扰，而滤波电容C13则可有效抑制差模信号的干扰。Figure 4 is a schematic diagram of the secondary signal amplification circuit. Since the signal amplification factor in the front-end amplification circuit should not be set too large, the signal needs to be amplified again. Among them, U4 is an integrated chip, and the REF1 pin is a reference pin, which is a reserved interface for designing a bias zeroing circuit. According to the principle of virtual break and virtual short of the operational amplifier, the gain G of the circuit is jointly determined by the two resistors R16 and R27, and the signal amplification factor can be adjusted according to actual needs. The resistor R19, capacitor C11, resistor R24, and capacitor C15 in the front-end peripheral circuit are filter circuits for common-mode signal interference at both ends, and the filter capacitor C13 can effectively suppress the interference of differential-mode signals. The integrated chip U4 is AD620AR integrated chip, the power supply voltage is set to ±5V, and the REF1 pin is the reference pin, which is used to reserve the access of the bias zeroing circuit. The circuit gain G is determined by the adjustable resistor R17, G=49.4K/
如图4所示，次级信号放大电路中的集成芯片U4的1脚和8脚外并联一个可调电阻R17，用于对整个电路增益的设置；集成芯片U4的2脚分别与电容C11的一端、滤波电容C13的一端和电阻R19的一端连接，电阻R19的另一端与前端放大电路的信号输出点SIGNAL2-连接，滤波电容C13的另一端接地；集成芯片U4的3脚分别与电容C15的一端、滤波电容C13的另一端和电阻R24的一端连接，电阻R24的另一端与前端放大电路的信号输出点SIGNAL2+连接，电容C15的另一端接地；集成芯片U4的4脚分别与电阻R26的一端和电容C16的一端连接，电阻R26的另一端与-5V电源端连接，电容C16的另一端接地；集成芯片U4的5脚作为REF1引脚，REF1引脚与电阻R27串联后接地；集成芯片U4的7脚分别与电阻R22的一端和电容C14的一端连接，电阻R22的另一端与+5V电源端连接，电容C14的另一端接地；集成芯片U4的6脚为输出vout11。其中电阻R19和电容C11,电阻R24和电容C15为两端信号的滤波电路，用于消除共模信号干扰；滤波电容C13用于消除差模信号干扰；电阻R26和电容C16起滤波作用，电阻R22和电容C14起滤波作用；REF1引脚作为增设引脚，用以电路调零的设计。As shown in Figure 4, an adjustable resistor R17 is connected in parallel with pin 1 and pin 8 of the integrated chip U4 in the secondary signal amplifying circuit for setting the gain of the entire circuit; One end, one end of the filter capacitor C13 is connected to one end of the resistor R19, the other end of the resistor R19 is connected to the signal output point SIGNAL2- of the front-end amplifier circuit, and the other end of the filter capacitor C13 is grounded; the 3 pins of the integrated chip U4 are respectively connected to the capacitor C15 One end, the other end of the filter capacitor C13 is connected to one end of the resistor R24, the other end of the resistor R24 is connected to the signal output point SIGNAL2+ of the front-end amplifier circuit, and the other end of the capacitor C15 is grounded; the 4 pins of the integrated chip U4 are respectively connected to one end of the resistor R26 Connect with one end of the capacitor C16, the other end of the resistor R26 is connected to the -5V power supply end, and the other end of the capacitor C16 is grounded; pin 5 of the integrated chip U4 is used as the REF1 pin, and the REF1 pin is connected in series with the resistor R27 and grounded; the integrated chip U4 The 7 pins of the integrated chip U4 are respectively connected to one end of the resistor R22 and one end of the capacitor C14, the other end of the resistor R22 is connected to the +5V power supply end, and the other end of the capacitor C14 is grounded; the 6 pins of the integrated chip U4 are output vout11. Among them, resistor R19 and capacitor C11, resistor R24 and capacitor C15 are filter circuits for signals at both ends, which are used to eliminate common-mode signal interference; filter capacitor C13 is used to eliminate differential-mode signal interference; resistor R26 and capacitor C16 act as filters, and resistor R22 And the capacitor C14 acts as a filter; the REF1 pin is used as an additional pin for the design of circuit zeroing.
图5为偏置调零电路示意图，为保证集成芯片的最优性能，次级信号放大电路中集成芯片U4的REF1基准引脚上的源阻抗应尽可能低。电压跟随电路具备输入阻抗高，输出阻抗低，前后隔离，且能提高带负载能力，在电路中起到阻抗变换的作用，因此能满足REF1引脚上源阻抗小的要求。实现REF1引脚上的电压可调，可满足在不同外界环境下抵消TMR传感器的偏置电压的需求。因此，本实施例中的偏置调零电路如图5所示，采用型号为TLC2272的芯片作为运算放大器搭建电压跟随电路，运算放大器U5A的5脚分别与电阻R21的一端和电容C12的一端连接，电容C12的另一端接地，电阻R21的另一端与可调电阻R20的调节端连接，可调电阻R20一端与电阻R16串联后接正电压端VCC，可调电阻R20的另一端与电阻R28串联后接负电压端VEE；同时，可调电阻R20外并联有串联连接的电阻R18和电阻R25。运算放大器U5A的6脚和7脚均与电阻R23串联后接集成芯片U4的REF1引脚。运算放大器U5A的8脚接正电压端VCC；运算放大器U5A的4脚接负电压端VEE。运算放大器U5A与电阻R21和电容C12构成的滤波电路及电阻R23构成一个电压跟随电路，用以对信号的提取传输；可调电阻R20和电阻R16和电阻R28主要是对电压的分配获取作用，用以获取电压作为电压跟随电路的输入；电阻R18和电阻R25同样是参与电压的分配，REF1引脚作为集成芯片U4的基准引脚。Figure 5 is a schematic diagram of the bias zeroing circuit. In order to ensure the optimal performance of the integrated chip, the source impedance on the REF1 reference pin of the integrated chip U4 in the secondary signal amplification circuit should be as low as possible. The voltage follower circuit has high input impedance, low output impedance, front and rear isolation, and can improve the load carrying capacity, and plays the role of impedance transformation in the circuit, so it can meet the requirement of small source impedance on the REF1 pin. The adjustable voltage on the REF1 pin can meet the requirement of offsetting the bias voltage of the TMR sensor under different external environments. Therefore, the bias zeroing circuit in this embodiment is shown in Figure 5, using a chip of type TLC2272 as an operational amplifier to build a voltage follower circuit, and
图6为功率放大电路(即运放驱动电路)和反馈电路示意图，由于研究的是微弱电流传感器研究，理论上芯片输出的差分电压经过放大电路后是可以驱动线圈的运作的，因此对于功率放大部分的设计仅采用简单运放驱动反馈线圈。其中J1模块为反馈线圈，R32为采样电阻，将二者串接在前端电路后再接地，通过测量采样电阻R32上的电压，可间接反映载流导线内部的电流。如图6所示，运放驱动电路设有一运算放大器U6A，型号为TLC2272，反馈电路包含反馈线圈J1和采样电阻R32；运算放大器U6A的3脚分别与电阻R29的一端和电容C29的一端连接，电容C29的另一端接地，电阻R29的另一端接入次级信号放大电路的输出vout11；运算放大器U6A的1脚和2脚均与电阻R30的一端连接，电阻R30的另一端与反馈线圈J1一端连接，反馈线圈J1的另一端与采样电阻R32一端连接，采样电阻R32另一端接地。运算放大器U6A的8脚分别与电容C17的一端和正电压端VCC连接，电容C17的另一端接地；运算放大器U6A的4脚分别与电容C19的一端和负电压端VEE连接，电容C19的另一端接地。电阻R29和电容C29构成滤波作用，电容C17和电容C19也是滤波作用，电阻R30分担电压作用；J1用来进行反馈线圈两端的接入；采样电阻R32用来配合采样电路实现电压采集。Figure 6 is a schematic diagram of the power amplifier circuit (that is, the operational amplifier drive circuit) and the feedback circuit. Since the research is on a weak current sensor, theoretically the differential voltage output by the chip can drive the operation of the coil after passing through the amplifier circuit. Therefore, for power amplifier Some designs use only a simple op amp to drive the feedback coil. The J1 module is the feedback coil, and R32 is the sampling resistor. Connect the two in series to the front-end circuit and then ground them. By measuring the voltage on the sampling resistor R32, it can indirectly reflect the current inside the current-carrying wire. As shown in Figure 6, the operational amplifier driving circuit is provided with an operational amplifier U6A, the model is TLC2272, and the feedback circuit includes a feedback coil J1 and a sampling resistor R32; pin 3 of the operational amplifier U6A is respectively connected to one end of the resistor R29 and one end of the capacitor C29, The other end of the capacitor C29 is grounded, the other end of the resistor R29 is connected to the output vout11 of the secondary signal amplifying circuit; both
图7为采样电路示意图，利用运放简单实现对采样电阻R32上电压的提取。如图7所示，采样电路设有一运算放大器U7A，型号为TLC2272，运算放大器U7A的5脚与电容C20的一端连接，电容C20的的另一端接地；运算放大器U7A的6脚分别与电阻R33和电阻R34的一端连接，电阻R34的另一端接地，电阻R33的另一端与测试端口J2的一端连接，运算放大器U7A的7脚也与与测试端口J2的一端连接，测试端口J2的的另一端接地。运算放大器U7A的8脚与正电压端VCC连接；运算放大器U7A的4脚与负电压端VEE连接。电容C20起滤波电路，电阻R34起缓冲作用，电阻R33用于运放输入与输出的信号传输通道；J2为预留的测试端口，用来对电压值的获取。J2为外接万用表或其他测试仪器，预留的测试，用来对电压值的获取。FIG. 7 is a schematic diagram of a sampling circuit, which simply realizes the extraction of the voltage on the sampling resistor R32 by using an operational amplifier. As shown in Figure 7, the sampling circuit is provided with an operational amplifier U7A, the model is TLC2272, the 5 pins of the operational amplifier U7A are connected to one end of the capacitor C20, and the other end of the capacitor C20 is grounded; the 6 pins of the operational amplifier U7A are respectively connected to the resistors R33 and One end of resistor R34 is connected, the other end of resistor R34 is grounded, the other end of resistor R33 is connected to one end of test port J2,
本发明基于TMR的微弱电流传感器信号处理电路的工作原理为：The working principle of the weak current sensor signal processing circuit based on TMR of the present invention is:
接通工作电源后，本发明的信号处理电路中涉及到的供电均由外部电源供电，图2中电源电路模块首先完成对外部电源的转化及稳压处理。通过TMR芯片将待测电流产生的磁场强度信号转化为差分电压输出信号，经由图3中信号输入点SIGNAL1+和信号输入点SIGNALl-两端信号输入，后经运算放大器U2A和运算放大器U2B进行信号放大，通过信号输出点SIGNAL2+和信号输出点SIGNAL2-两端把信号输出。再通过图4中前端外围电路电阻R19和电容C11与电阻R24和电容C15组成的滤波电路滤除两端共模信号干扰，滤波电容C13有效抑制差模信号的干扰。后信号进入集成芯片U4，通过调节可调电阻R17大小，再对信号进行放大，输出电压信号通过vout11输出，其中REF1引脚与图五偏置调零电路相连，通过调节可调电阻R20大小可改变REF1引脚的输入电压，从而对vout11的输出进行调节。vout11经过图6的运放驱动电路后接反馈线圈J1后再串接采样电阻R32后接地。通过在采样电阻上接入图7采样电路，获取其两端电压，通过电压与电阻比值求得反馈电流Is大小，再根据系统达到平衡时一二次侧安匝数关系比N1Ip＝N2Is，间接求得一次侧电流Ip大小，实现对待测电流大小的检测。After the working power supply is turned on, the power supply involved in the signal processing circuit of the present invention is powered by the external power supply. The power supply circuit module in FIG. 2 first completes the conversion and voltage stabilization of the external power supply. Through the TMR chip, the magnetic field strength signal generated by the current to be measured is converted into a differential voltage output signal, and the signal is input through the signal input point SIGNAL1+ and the signal input point SIGNALl- in Figure 3, and then the signal is amplified by the operational amplifier U2A and the operational amplifier U2B , output the signal through the signal output point SIGNAL2+ and the signal output point SIGNAL2-. Then, through the filter circuit composed of the front-end peripheral circuit resistor R19 and capacitor C11, resistor R24 and capacitor C15 in Figure 4, the common-mode signal interference at both ends is filtered out, and the filter capacitor C13 effectively suppresses the interference of the differential-mode signal. After the signal enters the integrated chip U4, the signal is amplified by adjusting the size of the adjustable resistor R17, and the output voltage signal is output through vout11, where the REF1 pin is connected to the bias zeroing circuit in Figure 5, and can be adjusted by adjusting the size of the adjustable resistor R20. Change the input voltage of the REF1 pin to regulate the output of vout11. Vout11 is connected to the feedback coil J1 after passing through the operational amplifier drive circuit in Figure 6, and then connected to the sampling resistor R32 in series, and then grounded. By connecting the sampling circuit in Figure 7 to the sampling resistor, the voltage at both ends is obtained, and the feedback current I s is obtained through the ratio of the voltage to the resistance, and then according to the relationship ratio N 1 I p between the ampere-turns of the primary and secondary sides when the system reaches equilibrium =N 2 I s , to obtain the magnitude of the primary side current I p indirectly, and realize the detection of the magnitude of the current to be measured.
所述TMR微弱电流传感器电路部分设计方案步骤如下：The design steps of the TMR weak current sensor circuit part are as follows:
(1)根据待测电流的大小及范围，通过仿真模拟产生磁场的大小，进而选择合适的TMR传感器芯片；在结合前端磁环间隙的尺寸，同时考虑传感器芯片的敏感轴方向，选择合适的/芯片封装，这样先确定好传感器芯片的型号及封装。(1) According to the size and range of the current to be measured, the size of the magnetic field generated by simulation is selected, and then the appropriate TMR sensor chip is selected; combined with the size of the front-end magnetic ring gap and the direction of the sensitive axis of the sensor chip, select the appropriate / Chip packaging, so first determine the model and packaging of the sensor chip.
(2)根据确定的传感器设计的电源条件，设计电源电路模块，其中涉及到正负电压的转换以及稳压部分的设计，需要结合传感器芯片的供电电压以及后续运放供电电压考虑。(2) According to the determined power supply conditions of the sensor design, design the power circuit module, which involves the conversion of positive and negative voltages and the design of the voltage stabilization part, which needs to be considered in conjunction with the power supply voltage of the sensor chip and the power supply voltage of the subsequent operational amplifier.
(3)根据传感器芯片灵敏度结合仿真待测电流产生磁场信号的大小，大致计算出TMR传感器芯片的输出差分电压信号，以此作为放大电路部分增益的一个参考；这部分主要通过comsol仿真软件求算出对应气隙部分磁场强度大小，比如对应一个值2oe，而芯片灵敏度假设为5mV/V/oe,其中灵敏度为1oe磁场强度下，每1V供电电压对应输出为5mV，这样通过简单计算就可以获知在芯片供电电压为1V时，芯片输出差分电压值为10mV。同时根据所设计传感器的频率范围或带宽要求，设计合适的滤波电路。(3) According to the sensitivity of the sensor chip combined with the magnitude of the magnetic field signal generated by simulating the current to be measured, roughly calculate the output differential voltage signal of the TMR sensor chip as a reference for the gain of the amplifier circuit; this part is mainly calculated by comsol simulation software Corresponding to the magnetic field strength of the air gap part, for example, corresponding to a value of 2oe, and the chip sensitivity is assumed to be 5mV/V/oe, where the sensitivity is 1oe magnetic field strength, the corresponding output of each 1V supply voltage is 5mV, so through simple calculations. When the chip power supply voltage is 1V, the chip output differential voltage value is 10mV. At the same time, design a suitable filter circuit according to the frequency range or bandwidth requirements of the designed sensor.
(4)依据闭环结构型TMR电流传感器的电流测量原理，即安匝数关系比，结合设计电流传感器的测量量程，确定好合适的线圈匝数，大致推算出实现磁平衡时反馈电路中电流的大小；公式为N1Ip＝N2Is，Ip为一次侧待测电流，把载流导体看作是匝数为1的线圈，即初级线圈匝数为N1为1；Is为反馈电流，N2为反馈线圈J1的匝数；进而据此对放大电路部分的增益与采样电阻的大小进行综合考虑确定，最后进行对采样电阻电压信号提取的采样电路的简单设计。(4) According to the current measurement principle of the closed-loop structure type TMR current sensor, that is, the relationship ratio of the ampere-turns, combined with the measurement range of the designed current sensor, determine the appropriate number of coil turns, and roughly calculate the current in the feedback circuit when the magnetic balance is achieved. Size; the formula is N 1 I p = N 2 I s , I p is the current to be measured on the primary side, and the current-carrying conductor is regarded as a coil with a turn number of 1, that is, the number of turns of the primary coil is N 1 is 1; I s is the feedback current, and N2 is the number of turns of the feedback coil J1; then, based on this, the gain of the amplifying circuit part and the size of the sampling resistor are comprehensively considered and determined, and finally a simple design of the sampling circuit for extracting the voltage signal of the sampling resistor is carried out.
以下为本发明专利的一个具体实施例：The following is a specific embodiment of the patent of the present invention:
以对0-10mA的微弱电流作为检测对象，展开对TMR电流传感器电路的设计。依据测量范围TMR传感器芯片的型号选取TMR2901芯片，敏感轴为y轴，供电电压设定为5V。其中图2中所设计的隔离电源原理图所用到的芯片U6选择型号为A2409S-2WR3的集成芯片，该芯片为2W定电压输入，隔离非稳压正负双路输出，该芯片有可持续短路保护，功率密度高，空载输入电流低至8mA，工作温度范围为-40℃～-105℃，效率高达86％，增设如图中外围电路，实现从24V电压到正负9V电压的变换。图3中运算放大器U2A、运算放大器U2B、跟随器U3A的型号均选取双通道运算放大器TLC2272，总的电路增益设置为2倍。双通道运算放大器用同一偏置电路来支持所有放大器，从而降低复杂性、芯片面积和成本。由于这些放大器共处同一芯片，因此它们具有非常高的一致性，也会减小传感器误差。Taking the weak current of 0-10mA as the detection object, the design of the TMR current sensor circuit is launched. Select the TMR2901 chip according to the model of the TMR sensor chip in the measurement range, the sensitive axis is the y-axis, and the power supply voltage is set to 5V. Among them, the chip U6 used in the schematic diagram of the isolated power supply designed in Figure 2 is an integrated chip of the model A2409S-2WR3. The chip is a 2W constant voltage input, and the isolated unregulated positive and negative dual outputs. The chip has a sustainable short circuit Protection, high power density, no-load input current as low as 8mA, operating temperature range from -40°C to -105°C, and efficiency as high as 86%. Add peripheral circuits as shown in the figure to realize the conversion from 24V voltage to positive and negative 9V voltage. In Figure 3, the models of operational amplifier U2A, operational amplifier U2B, and follower U3A all select dual-channel operational amplifier TLC2272, and the total circuit gain is set to 2 times. Dual op amps use the same biasing circuitry to support all amplifiers, reducing complexity, die area, and cost. Since these amplifiers are co-located on the same die, they are very coherent and also reduce sensor errors.
图4中次级信号放大电路的芯片U4选用AD620AR集成芯片，供电电压设定为±5V,REF1引脚为基准引脚，用来进行偏置调零电路的设计。电路的增益G由电阻R16和电阻R27共同决定，G＝49.4K/Rg+1，根据实际需要调节信号放大倍数。图5中偏置调零电路利用运放TLC2272搭建电压跟随电路，实现REF引脚上的电压可调。图6中J1模块为反馈线圈，R32为采样电阻，实际设计中反馈线圈J1使用的材料为漆包线，将其均匀缠绕在聚磁环上，反馈线圈的匝数不宜过大，设定为100匝。通过测量电阻R32上的电压，可间接反映载流导线内部的电流。应保证采样电阻R32足够大，以获得良好的输出电压分辨率，经过大致计算在次级放大电路增益为10的情况下，采样电阻大小设置为750Ω的精密电阻。The chip U4 of the secondary signal amplifying circuit in Figure 4 selects the AD620AR integrated chip, the power supply voltage is set to ±5V, and the REF1 pin is used as the reference pin for the design of the bias zeroing circuit. The gain G of the circuit is jointly determined by the resistor R16 and the resistor R27, G=49.4K/
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