医用X光机电源系统研究

发布时间：2018-02-23 05:20

本文关键词： 医用X光机电源 BoostAPFC 全桥逆变LLC谐振变换器软开关技术 PFM控制单周期控制　出处：《重庆大学》2014年硕士论文　论文类型：学位论文

【摘要】：X射线的发现对人类医学史的进步做出了巨大贡献，X射线被广泛应用于疾病的诊断与治疗。X射线的质量决定了成像质量并影响着人体健康，而X光机电源系统的质量决定了X射线的质量，因此研究高性能的X光机电源系统具有现实意义。目前的X光机电源的不足主要体现在：频率低，体积大，效率低，输出电压上升时间长，纹波大，将严重影响X射线的质量，增加X射线对病人的伤害。针对目前X光机电源的现状以及存在的问题，本文对X光机电源系统的高压直流电源和灯丝电源分别进行了设计，对电源系统进行了理论分析与相关公式推导，通过Saber仿真软件进行了仿真验证，搭建了实验平台进行了实验验证，仿真、实验结果与理论分析吻合，达到了预期效果。本文首先阐述了医用X光机电源的发展现状及存在的不足，以及电源系统对X射线质量的影响，对成像质量的重要意义。本文将全桥逆变LLC谐振软开关技术应用于X光机电源系统中。谐振软开关能够提高工作频率，减小电源体积，有利于电源系统的小型化；并且解决了因高频化而带来的开关损耗大的问题，提高了整体效率。对全桥逆变LLC谐振变换器进行了理论分析，建立了基波等效模型，推导了增益公式，画出增益曲线并进行分析，对谐振元件的参数进行了详细设计。采用PFM控制方式，通过调节开关频率来调节谐振槽的增益，从而实现输出电压在40kV~120kV之间的调节，比传统Buck加全桥逆变电路控制方式更为简单。设计了以MC33067芯片为核心的PFM控制电路，以及采样电路，保护电路。采用单周期控制无源无损软开关BoostAPFC电路，详细分析了单周期控原理及无源无损软开关电路，并对PFC主电路参数进行了详细设计。介绍了单周期控制芯片IR1150，并设计了以其为核心的控制电路。计算出PFC级的开环传递函数，画出其bode图进行稳定性分析。根据灯丝电源只需对灯丝加热提供足够的功率，而对电流波形没有严格要求的特点，在充分利用变压器漏感及隔离电容等参数的基础上，设计了基于LC串联谐振并采用PFM控制方式的灯丝电源。最后利用Saber仿真软件及实验进行了验证，仿真及实验结果表明，本文设计的医用X光机电源系统基本达到了预期效果，，能够满足设计要求。
[Abstract]:The discovery of X-ray has made a great contribution to the progress of human medical history. X-ray is widely used in the diagnosis and treatment of diseases. The quality of X-ray determines the quality of imaging and affects human health. The quality of the power supply system of X-ray machine determines the quality of X-ray, so it is of practical significance to study the high performance power supply system of X-ray machine. At present, the shortcomings of the power supply of X-ray machine are mainly reflected in: low frequency, large volume, low efficiency. The long rise time of output voltage and the large ripple will seriously affect the quality of X-ray and increase the injury of X-ray to the patient. Aiming at the present situation and existing problems of X-ray machine power supply, this paper designs the high voltage DC power supply and filament power supply of X-ray machine power supply system, and analyses the power supply system theoretically and deduces the relevant formula. Saber simulation software is used to verify the simulation. The experimental platform is built and the simulation results are consistent with the theoretical analysis, and the expected results are achieved. In this paper, the current situation and shortcomings of the power supply for medical X-ray machine are described, and the influence of the power system on the quality of X-ray is also discussed in this paper. In this paper, the full-bridge inverter LLC resonant soft switch technology is applied to the X-ray machine power supply system. The resonant soft switch can increase the working frequency, reduce the power supply volume, and is conducive to the miniaturization of the power supply system. The problem of high switching loss caused by high frequency is solved, and the overall efficiency is improved. The theoretical analysis of full-bridge inverter LLC resonant converter is carried out, the equivalent fundamental wave model is established, and the gain formula is derived. The gain curve is drawn and analyzed, and the parameters of the resonant element are designed in detail. The output voltage is adjusted between 40 kV and 120 kV by adjusting the switching frequency to adjust the gain of the resonant slot by using the PFM control mode. Compared with the traditional Buck and full-bridge inverter circuit, the control circuit of PFM based on MC33067 chip, sampling circuit and protection circuit are designed. The single cycle control passive lossless soft switching BoostAPFC circuit is used to analyze the single cycle control principle and passive lossless soft switch circuit in detail. The main circuit parameters of PFC are designed in detail. The single cycle control chip IR1150 is introduced, and the control circuit based on IR1150 is designed. The open loop transfer function of PFC level is calculated and its bode diagram is drawn for stability analysis. According to the characteristic that the filament power supply only need to provide enough power to the filament heating, and there is no strict requirement for the current waveform, on the basis of making full use of the parameters such as transformer leakage inductance and isolation capacitance, A filament power supply based on LC series resonance and PFM control is designed. Finally, the Saber simulation software and experimental results show that the power supply system of the medical X-ray machine designed in this paper has basically achieved the desired results, and can meet the design requirements.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM46

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