Study And Development Of High Frequency X-ray Source For Security Inspection Equipment

X-ray has been widely used in industry and medicine since it was found in 1895, such as nondestructive detection of cavities in objects using X-ray's property of penetration, trace element analysis using X-ray's property of fluorescence , and so on. However, the low-frequency transformer and multiple voltage rectifiers were used to generate the DC high-voltage for X-ray tube from 50Hz-AC utility system. These conventional types of X-ray sources were bulky in physical size and heavy in weight and the control accuracies of the output voltages were not always satisfactory. The development of a high-frequency X-ray source using switching power-supply technology and digital control technology is discussed in the paper.The introduction outlines structure of X-ray source and points out the topic origin. In chapter 2, characteristics of voltage gain versus frequency and operating principle of the resonant inverter are analyzed. Strategy of adjusts output voltage for high-voltage generator is studied. According to the characteristics of high-voltage generator, a topology structure was developed including a BUCK circuit, parallel-loaded resonant inverter, high-voltage transformer and voltage multiplier. In chapter 3, the parameter design for the main circuit of X-ray source is presented. Main circuit design includes six units: rectifier filter, BUCK circuit, parallel-loaded resonant inverter, high-voltage transformer, voltage multiplier, filament power supply. The parameters of circuit are given and simulation and experiment studies are carried out. In chapter 4, the close-loop feedback control model of high-voltage generator is constructed. According to the characteristics of high-voltage generator, a proportional-integral (PI) controller topology and parameters are presented. Simulation and experiment results are given in the end. In chapter 5, the hardware and software design of digital control system based on microcontroller for X-ray source are presented.At last, the operational characteristics of this X-ray source have been proved by experiments to be fully agreed with the designing targets.