【作者】 杨伟军；

【导师】 赵立宏； 陈海辉；

【作者基本信息】 南华大学 ， 核能与核技术工程， 2010， 硕士

【摘要】 X射线管经历了离子X射线管、电子X射线管、旋转阳极X射线管三个阶段。随着电力电子技术和微机技术的发展,X射线机正朝着高性能、低成本化的方向发展：高压发生电路从传统的工频(50Hz)向中频、高频的方向发展,减少了球管体积；控制电路采用了单片机技术,可实现高精度闭环控制管电流、管电压,精确控制曝光时间；采用高频逆变可输出直流管电压,减少软X射线对人体的伤害。本文提出一种基于MC34067的串并联谐振零电压软开关IGBT全桥拓扑电路。该高压直流发生器运用IGBT逆变模块和脉冲频率PFM调制技术,在准谐振模式下实现零电压软开关功能,在大范围负载下能完全获得稳定的零电压软开关换流。提出一种快速补偿空间电荷效应以精确控制管电流方法：利用了TL494的死区时间控制端,以补偿阳极高压对阳极电流的影响。阳极电流反馈信号与设定电流比较进行误差放大后,送入PWM集成电路TL494的比较器,通过灯丝的电流控制来达到闭环控制管电流。实验结果表明这种IGBT串并准谐振VZS-PFW可适应X线机负载大范围变化,控制策略切实可行。本文自主研制了高频直流牙科X射线机,高压发生电路频率20 KHz,瞬时功率1600W,输出管电压可在50～100kV范围内调整,输出管电流可在3～8mA范围内调整,功率因数不小于0.92,整机效率不低于90%,球管尺寸小(50×120×125mm)。该机高频逆变电源采用先进的IGBT开关器件和高频谐振逆变器技术,输出直流管电压,效率及可靠性极高,阳极高压稳定。采用微处理器调频控制管电流、管电压。保护措施完善,具有过过管输入电压、过管电流、过灯丝电流、过功率保护；能自我诊断系统各部分的连接状态,并显示状态。人机界面友好,采用超大汉字或英文液晶显示。多点曝光按键选择,最大限度保证操作者的人身安全与方便。可以采用球管曝光按键近距离曝光、可以采用有线远距离曝光、可以采用远距离红外曝光。共研制了2套样机,进行了电路老化试验、抗干扰试验、介电强度试验,实验结果表明性能优良。样机以每3分钟曝光1次,进行了1000小时的连续实验之后,依然可以正常工作。用CCD成像系统可以清晰地看到约20微米的单片机内部线路,可以清晰地看到牙齿髓腔。用牙科胶片也可以清晰地看到牙齿髓腔。高频逆变技术、微机控制技术的引入使国内牙科X线机的整体水平将会有很大提高。更多还原

【Abstract】 X-ray tube has experienced three stages, the ion X-ray tube, the electronic X-ray tube, the rotating anode X-ray tube. Along with the electric & electronic technology and the microcomputer technology’s development, the X-ray machine toward the high performance, low cost’s direction is developing. Power-frequency (50Hz) transformer has been taken over in whole or in part by intermediate frequency, high frequency invertor in the high voltage circuit, which can reduce the bulb volume; MCU technology has used in the control circuit to realize the high accuracy closed loop control for the tube electric current, the tube voltage and X-ray exposure time; High frequency invertor can output DC high voltage for the X-ray tube, that reduces the soft X-ray to human body’s injury.Based on microchip MC34067, One kind of IGBT full bridge circuit topology with Series and Parallel Quasi-resonant Zero-Voltage Swith (ZVS) is proposed in this paper.IGBT converter and Pulse Frequency Modulation (PFM) have been utilized in the high voltage DC circiut, in which the stable current convert in the wide range of load could be completely realized by Series and Parallel Quasi-resonant Zero Voltage Switch.one kind method of fast compensation space-charge effect is propsed to accurately control the tube current. This way uses the TL494 dead time control pattern to compensate the anode high voltage to the anode current influence. After the error amplification between the feedback signal of anode current and the hypothesis electric current, the comparison value is then sent to the PWM comparator of the integrated microchip TL494, the closed loop control of tube electric current is achieved by the filament current control. The experimental result indicates that this kind of IGBT series and parallel quasi-resonant VZS-PFW is suitable to X machine wide range load request, and the control policy is practical and feasible.High frequency DC dental X-ray machine has independently been developed, in which invertor frequency 20 KHz, instantaneous power more than 1600W, the tube voltage may be adjusted in the 50-100kV scope, the tube electric current may be adjusted in the 3-8mA scope, the power factor is not smaller than 0.92, the complete machine efficiency is more than 90% slightly, the bulb size (50X120X125mm).This dental X-ray machine adopts IGBT component as high frequency switch, serires and parallel quasi-resonant technology, outputs the DC tube voltage. So the efficiency and the reliability is extremely high, the anode high voltage is stable. Pulse Frequency Modulation is realized by microprocessor to control tube current, tube voltage. The protective measures are perfect, includes input voltage, tube current, filament current and overpower protection; The diagnosis system can detect connection condition of the various parts, then display these status. The man-machine contact surface is friendly, uses the ultra big Chinese character or English liquid crystal display. The multi-spot pressed keys of X-ray exposure, short-distance bulb exposure key, long-distance wired exposure key, long-distance infrared exposure key, maximumly assures operator’s personal safety and convenient.2 sets of dental X-ray prototypes has been manufactured, carried on the electric circuit degradation testing, the antijamming experiment, the dielectrical strength experiment. The experimental result indicates that the performance is fine. After 100 hour continual experiment which one time exposures per 3 minutes, the prototypes still good work. The approximately 20 micron wide integrated circuit interior line, or tooth medulla cavity can clearly be recorded by CCD imaging system. Tooth medulla cavity may also clearly be recorded by dental film.The high frequency contravariant and microcomputer control technology is introducted to domestic dental X-ray machine, which very greatly impetus the technology progresses.Author:Yang Wei-JunDirected by Zhao Li-Hong, Chen Hai-Hui更多还原