X射线管120kV射源系统研究与设计

【作者】 张瑞；

【导师】 李思奇；

【作者基本信息】 昆明理工大学 ， 电力电子与电力传动， 2021， 硕士

【摘要】 X射线成像技术在医疗CT成像中应用十分普遍,在医学影像诊断技术中起着不可替代的作用,射源系统作为医疗CT的核心组成部分受到广泛关注,其性能好坏决定了医疗CT成像质量。为满足市场的需求,本文研究设计了一款输出电压50-120kV、输出电流2-10m A连续可调的高频化、小体积、智能化牙科医疗CT射源系统,主要包括高压直流电源、高隔离灯丝电源。首先,通过对比分析现有高压直流电源结构优缺点,本文高压直流电源前级采用单相Boost-PFC,主电路拓扑采用高压同步Buck电路和固定频率对称半桥LLC谐振变换器,最后采用高频高压变压器和倍压整流电路进行升压,输出高压直流。建立LLC谐振变换器基波等效模型,推导了输出电压与输入电压的电压增益关系,设计了固定频率下LLC谐振变换器参数,并在LTspice电路仿真软件中建立了基于对称半桥LLC谐振变换器和全桥逆变两种主电路仿真模型,分析了两种电路的工作状态,其中全桥逆变电路在电路不对称情况下会发生直流偏磁。其次,针对变压器偏磁问题,提出了一种带有低损耗阻尼电路的偏置电流传感器,阐述了偏磁电流传感器的工作原理,推导了传感器的传递函数,搭建了偏置电流传感器实验平台,进行了实验验证。接着,将双边S补偿电路的无线电能传输应用到灯丝电源中,分析了双边S补偿电路,设计了一种分离式平面变压器的120kV高隔离灯丝电源,在Maxwell仿真软件建立了分离式平面变压器仿真模型,分别进行磁场和电场仿真,搭建了灯丝电源的实验平台,实现了120kV高隔离灯丝电源基本功能。最后,设计了前级Boost-PFC参数,并对Boost-PFC样机进行了测试。针对自举供电不稳定问题,提出了一种预充电的自举驱动电路结构,设计了射源系统电路参数,搭建了高压直流电源实验平台,实现了高压直流电源稳定输出,在铅房中进行了120kV射源系统测试,X射线管可以稳定出X射线,同时进行了成像实验,成像效果较好,图像较为清晰。更多还原

【Abstract】 X-ray imaging technology is widely used in medical CT imaging and plays an irreplaceable role in medical imaging diagnosis technology.Radiation source system as the core component of medical CT has been widely concerned.The performance of the radiation source system determines the imaging quality of medical CT.To meet the market demand,this paper studies and designs a high-frequency,small volume and intelligent dental CT emitter system with continuously adjustable output voltage of 50-120 kV and output current of 2-10 m A,including high-voltage DC power supply and high isolation filament power supply.Firstly,the advantages and disadvantages of existing high-voltage DC power supply structure are compared and analyzed.In this paper,the front stage of high-voltage DC power supply adopts single-phase boost PFC and the main circuit topology adopts high-voltage synchronous buck circuit and fixed frequency symmetrical half bridge LLC resonant converter.Finally,high-frequency high-voltage transformer and voltage doubling rectifier circuit are used to boost and output high-voltage DC.The fundamental equivalent model of LLC resonant converter is established,the voltage gain relationship between output voltage and input voltage is derived,and the parameters of LLC resonant converter are designed.Two main circuit simulation models of symmetrical half bridge LLC resonant converter and full bridge inverter are established in LTspice circuit simulation software.The working state of two circuits are analyzed.DC magnetic bias will occur in full bridge inverter circuit when the circuit is not symmetrical.Secondly,aiming at the problem of transformer magnetic bias,a bias current sensor with low loss damping circuit is proposed.The working principle of the bias current sensor is described and the transfer function of the sensor is derived.The experimental platform of the bias current sensor is built for experimental verification.Then,the wireless power transmission of bilateral s compensation circuit is applied to the filament power supply and the bilateral s compensation circuit is analyzed.A 120 kV high isolation filament power supply based on the separated planar transformer is designed.The simulation model of the separated planar transformer is established in Maxwell simulation software,and the magnetic field and electric field are simulated respectively.The experimental platform of the filament power supply is built to realize the basic function of power supply of the120 kV high isolation lamp.Finally,the parameters of the previous Boost-PFC are designed and the Boost-PFC prototype is tested.Aiming at the problem of instability of bootstrap power supply,a pre-charged bootstrap drive circuit structure is proposed,the source system circuit is designed,the high-voltage DC power supply experimental platform is built,and the stable output of the high-voltage DC power supply is realized.The test of the radiation source system is carried out in the lead room.The X-ray tube can stably emit X-rays,and at the same time,imaging experiments have been carried out.The imaging effect is better and the image is clearer.更多还原