Research And Design Of Amplifier Based On Magnetic Coupling Isolation

With the development of industrial technology,in order to achieve precise control of various industrial control systems and automotive motors,it is necessary to monitor the real-time parameters of the system and dynamically adjust them.However,in these fields,sensor technology is faced with many problems such as common mode voltage fluctuations,interference noise,and transient surge voltage.In order to ensure the accuracy of signal sensing,isolation components are usually used for signal sampling.Isolation amplifiers can achieve high-precision isolation transmission of analog signals while ensuring a larger signal bandwidth,and are widely used in the above fields.This thesis systematically studies isolation amplifiers.Firstly,the advantages and disadvantages of various isolation current sensing methods are studied,and the isolation sensing system based on shunt resistance and isolation amplifier is determined.Secondly,the modulation method of digital signal isolation transmission is studied in depth,and the theoretical basis for selecting switch key-controlled modulation is discussed,and the system architecture of isolation amplifier is designed.Finally,Sigma-Delta modulation is used to solve the problem of poor accuracy of traditional analog transmission and modulation methods.In the circuit design stage,the modulator is first system-modeled using Simulink tools to determine system parameters and circuit indicators,and the entire system’s signal-to-noise ratio performance basically meets the design requirements.In order to ensure the slew rate,Class AB output stages are used in all operational amplifiers.For the design of the digital isolator encoding circuit,cross-coupled oscillators are used to achieve signal modulation.To solve the problem of low bandwidth of the traditional switch key-controlled modulation decoding circuit,the structure of the decoding circuit is modified,and current comparators are selected to obtain a larger bandwidth,and further optimization is performed.A fourth-order multi-feedback Bessel filter is designed to ensure the system’s in-band flatness and good phase-frequency characteristics.The thesis is based on on-chip transformer technology and Huahong 0.18μm process to complete the circuit design and simulation verification of the isolation amplifier.The simulation results show that at a bandwidth of 100 k Hz,the SNDR of the isolation amplifier is 96.8d B,at a bandwidth of 10 k Hz,the SNDR is 105.3d B,the rise time of the step response output signal is 3.5μs,the transmission delay of the system is about 3.5μs,and the overall power consumption is11.1mA.