Research And Design Of Magnetic Field Measurement System And Power Management

As one of the earliest recognized physical phenomena,magnetic phenomenon is universal and diverse.In order to understand and explain many common physical phenomena in life,it is necessary to consider magnetism as an important factor.Therefore,as the primary technique for studying magnetic phenomenon,magnetic field measurement technology has been widely used in a long history of development.Among the most commonly used magnetic field measurement systems,Hall effect-based magnetic field measurement system is more popular in national defense technologies,automotive electronics,industrial control systems and consumer electronics due to its excellent overall performance in cost,power consumption,linearity range and integration.However,with the rapid development of semiconductor technology,more applications are putting forward higher requirements in terms of electromagnetic interference(EMI),reliability,and accuracy.Therefore,this dissertation focus on the power management module —— buck DC-DC converter and magnetic field measurement module —— linear Hall sensor in the Hall effect-based magnetic field measurement system,analyzes in detail how the performance is limited in the above three aspects,and proposes specific solutions.The main research and innovation results of this dissertation are as follows.1.The conventional buck DC-DC converter with constant on-time(COT)architecture suffers from two issues: a)the switching frequency varies greatly with the load current;and b)the output capacitor with low equivalent series resistance(ESR)destabilizes the system.To address these two problems,a control technique based on the reference and frequency compensation(RFC)is proposed in this dissertation.Without additional external components,the RFC is able to stabilize the converter and eliminate its switching frequency variation issue with low ESR output capacitor.The proposed converter with RFC technique was fabricated using a standard 0.25μm BCD process.With low ESR ceramic output capacitors,the experimental results show that the converter functions properly and stably in the load range up to 6A,and the switching frequency variation with load current is constrained to 3.8KHz/A.Thus,the capability of the converter to suppress EMI is greatly improved.This research has been published in the academic journal of IEEE Transactions on Industrial Electronics.2.In the conventional peak current-mode(PCM)buck DC-DC converter,two sensed inductor current signals are processed in three separate comparators to regulate the converter under various load conditions.These independent sensing currents and comparators not only consume large quiescent current and silicon area,but also cannot guarantee the accuracy of current limit threshold.To address this problem,a control technique based on multiplex pulse width modulation(MPWM)comparator is proposed in this dissertation.Through MPWM comparator,only one sensing current and one comparator are required to process the inductor current information and complete the regulation of converter under various load conditions,while greatly improving the accuracy of the current limit threshold.The proposed converter with MPWM comparator was fabricated using a standard 0.18μm BCD process,and the experimental results show that the converter works properly in the 5A load range and the current limit threshold only varies by 8.1% in the temperature range of-40 to 125℃ and the input voltage range up to 60 V.Thus,the reliability of the converter has been significantly enhanced.This research has been published in the academic journal of IEEE Transactions on Industrial Electronics.3.The accuracy of sensitivity and quiescent output voltage in conventional linear Hall sensors is mainly limited by the following two points: a)the characteristics of the Hall plate are affected by the offset voltage and temperature;and b)the characteristics of the signal conditioning circuit are affected by the offset voltage and noise.To address these two issues,the whole signal conditioning circuit is processed with low-offset and low-noise optimization by spinning current technique and chopper stabilization technique based on integrated demodulator operational amplifier(IDOP)in this dissertation.Moreover,a digital temperature compensation(DTC)technique is presented to further reduce the quiescent output voltage and sensitivity variation caused by temperature.The proposed linear Hall sensor was fabricated using a standard 0.18μm BCD process,and the experimental results show that the variation of quiescent output voltage is reduced to 5.6m V and the sensor sensitivity is controlled within 1.34% in the temperature range of-40 to 150℃.Thus,the accuracy of sensitivity and quiescent output voltage in the proposed linear Hall sensor is greatly improved.In general,the main innovative work of this dissertation is to propose the compensation of reference and frequency based control technique,the MPWM comparator based control technique,and the integrated demodulator operational amplifier with digital temperature compensation based control technique.The experimental results show that they can play a significant role in suppressing EMI,enhancing reliability and improving accuracy in Hall effect-based magnetic field measurement system.