Application Research Of High Frequency High Voltage Technology In CO₂ Laser

Repeated charge-discharge of high voltage capacitor bank is core work processes in electric excitation CO2 laser, high voltage capacitor charging power supply and switch trigger system are two core high-voltage subsystems. Industrial frequency L-C resonant power supply whose output voltage dropped after increased working frequency, was used in CO2 laser. The dropped output voltage affectted the stability and quality of laser. Meanwhile, it had huge size and weight what was disadvantageous to small size and weight of the device. Single-pulse trigger mode was adopted for the traditional switch trigger system, whose breakdown probability decreasesed after increased working frequency and switch gas pressure; otherwise, the trigger system had low efficiency, large loss and severe fever. Dveloping the study of high frequency high voltage technology and applying the technology in CO2 laser with the development of high frequency high voltage switching devices, magnetic materials and high voltage insulation materials, have important practical value to improve the reliability and stability, reduce the size and weight and develop high-power high-repetition frequency laser. That was significant to enhance the overall technological level of CO2 laser.The analysis based on particularity of high frequency high voltage charging power supply, pointing out that series resonant converter working in discontinuous current mode was suitable for charging power. As the project coming from Science and Technology Bureau named as “36k V/10 k W high frequency high voltage charging power supply” an example, various circuits design process, design ideas, key device selection was telled about, based on the theoretical analysis, Pspice software simulation and engineering application. Designing a high voltage discharging detection circuit which solved high voltage discharging detection problem of 100 ns. The method of increasing the turn ratio of transformer to weaken the impact of distributed capacitance and to improve the charging speed was put forward. Continuous charge-discharge test was carried on, when resonant capacitor was 1.16 u F and resonant inductor was 15 u H. High-voltage capacitor of 0.286 u F was charged to 37 k V using 15 ms, peak output power of the charging power supply was 13.05 k W, efficiency of the charging power supply was 0.82,discharge frequency was 25 Hz. The results showed that: high frequency high voltage charging power supply could be applyed for charging power supply of CO2 lasers, establishing foundation of high frequency high voltage technology applyed in CO2 lasers; the design method was reliable and technical foundation for the development of high power charging power supply was established.According to the status that there had no consistent conclusions for core selection and winding design of high power high frequency high voltage transformer, three kinds of cores composed by two materials, two shapes, were choosed for designing theoretical transformer. The conclusion that nanocrystalline core was suitable for high power high frequency high voltage transformer core was obtained by calculating distributed parameter and power loss. C-type nanocrystalline cores was suitable for applications in 20 k W charging power supply; ring nanocrystalline core was suitable for applications in 30 k W charging power supply; high power high voltage winding was not divided more than 4 sections, distributed capacitance was reduced by increasing insulation distance of the winding. A dry-type transformer and a oil-immersed transformer were maked for experimental research, the results showed that: the oil-immersed casting method was more easier to implement under current conditions.Two methods for improving the breakdown probability and efficiency, reducing the loss of trigger system, were put forward through the study of the basic theory of gas discharge, traditional test data and high frequency high voltage technology. Two prototypes based on multi-pulse with narrow width trigger mode and resonant charging trigger mode were developed for testing. Test results showed that: two trigger systems increased breakdown probability of 2.7%; with respect to traditional switch trigger system, the efficiency of multi-pulse rigger system was improved by 0.12, the loss was reduced 1.152 k W; with respect to multi-pulse trigger system, the efficiency of resonant charging trigger system was improved by 0.6, the loss was reduced 0.7k W. The test results demonstrated the feasibility of the two trigger systems.