The Design Of Excitation Power Supply And Control System For Medical Low-temperature Plasma

In the recent years, the researches on plasma technique have developed rapidly and it is proved that the low-temperature plasma has an excellent sterilizing effect. Because of the advantages such as the short sterilizing time and high sterilizing efficiency without pollution and residue, the low-temperature plasma technology has gradually become the new-generation disinfecting and sterilizing technology. In addition, it has a great application prospect to the areas such as modern food sanitation and biomedical treatment. There are extensive domestic and overseas researches on the production of low-temperature plasma. And the high-voltage pulse power supply is utilized to conduct the dielectric barrier discharge (DBD), which is a typical low-temperature plasma technology produced by the gas discharge in the barometric pressure.The thesis firstly discussed briefly the production mechanism of plasma and then introduced several kinds of regular gas discharge forms. Meanwhile, the paper focused on the discussion of principles and the plasma production methods of DBD in the barometric pressure. Based on the principles of DBD, the paper designed a medical low-temperature plasma excitation power supply. The thesis emphasized the hardware circuit design of excitation power supply and respectively introduced the designs of rectifier and filter, half-bridge inverter structure circuit, PWM control circuit, opto-isolator and driver circuit as well as over-current or over-voltage protection circuit. The series-parallel resonant soft-switching technology was adopted to reduce efficiently the losses in the switching process and improve the energy utilization ratio. Meanwhile, the thesis discussed the basic theories of high-frequency pulse transformer and designed a high-voltage pulse transformer with good performance according to the requirements of the paper.The emphasis of the thesis is the research design of the medical low-temperature plasma excitation power supply. According to the power requirements, the thesis used the isolated half-bridge inverter structure with the excellent symmetrical and easily driven features. Adopting the SG3525 as the master control chip for the PWM, the scheme where the rapid opto-isolator and integrated IC drive the MOS switching tube realized the adjustable feature for the frequency of 10 kHz-25 kHz and for the pulse width of 2 us-25 us in the excitation power supply.Finally, by the experimental examination, the low-temperature plasma excitation power supply can basically meet the design standards and it is stable for DBD. However, the effect related to the production of low-temperature plasma jet flow is not ideal. The scheme of power circuit and control system still needs some improvements. At the last part, the thesis made the prospect for the effect after the improvements.