基于PFM的高频高压发生器高压控制的研究  

Study of the High Voltage Control of High Frequency High Voltage Generator Based on PFM

作　　者：张广鹏[1] 周凌宏[1] 骆毅斌[1] 

机构地区：[1]南方医科大学生物医学工程学院,广东广州510515

出　　处：《中国医学物理学杂志》2013年第4期4294-4298,共5页Chinese Journal of Medical Physics

基　　金：广东省战略性新兴产业核心技术攻关(2011A081402003);广州市重大科技专项计划(2011Y1-00019)

摘　　要：目的:在医用诊断X射线设备中,单色X射线产生的投影数据,更有利于对图像进行处理,X射线管阳极和阴极间的直流电场决定了X射线的能量谱,为了产生能量集中的X射线,就需要给X射线管提供平稳的直流电压,本文研究设计并实现了一种用于精确控制口腔CBCT的X射线球管电压的控制策略及其硬件实现。方法:设置好X射线管需要的电压,微控制器(MCU)从存储器中读取与设置的输出电压相关的参数,然后控制数模转换器(DAC)的输出电压,将DAC的输出电压作为控制逆变频率的预置参考电压值,通过改变参考电压值来调整脉冲频率调制(PFM)控制芯片MC33067输出脉冲的频率。结果:通过控制逆变全桥输出脉冲的频率,改变了变压器初级的输入电压,实现了对经过变压器升压后进行倍压整流滤波输出的直流电压的自动控制和调整,使实际输出电压值与设置的输出电压值吻合,输出电压误差小于3%。结论:通过实验验证,观测输出电压的反馈波形,证明通过该控制方法输出的直流电压稳定,纹波小,可以为X射线球管提供直流高压。Objective： In medical diagnostic X-Ray equipment, projection data generated by Monochromatic X-Ray is more conducive to the image processing. The X-Ray energy spectrum is determined by the DC electric field between the anode and the cathode of X-Ray tube. In order to produce the X-Ray which energy is concentrated, the X-Ray tube needs to provide a smooth DC voltage. This study designed a controlling strategy to control Dental CBCT X-Ray tube voltage precisely, and completed the implementation of hardware. Methods： Set the voltage required for the X-ray tube, microcontrollers （MCU） read from the memory and set the relevant parameters of the output voltage, and then it is used to control the output voltage of the digital-to-analog converter （DAC）,and the DAC output voltage is used to preset reference voltage value of the control inverter frequency, and adjust the pulse frequency modulation （PFM） control by changing the reference voltage value chip MC33067 of the output pulse frequency by controlling the inverter bridge output pulses frequency. Results： Though controlling the output pulse frequency of full-bridge inverter, the primary input voltage of the transformer is changed, the output voltage＇s automatic control and adjustment through transformer boost DC voltage double rectifier is achieved, actual output voltage matches with the output voltage value set, the Output voltage error less than 3%. Conclusions： By observing the waveform of the output voltage feedback experiments can prove that through this control method, the output voltage obtained is stable with low ripple, so it can provide the DC high voltage for X-Ray tube.

关 键 词：X线球管电压控制 全桥逆变 脉冲频率调制 自动调整 

分 类 号：R318.6[医药卫生—生物医学工程]