The Key Technology Research Of High Voltage Pulse Power Supply For Sterilization

The demand for food safety and nutrition is becoming higher with the improvement of people’s living standard. The traditional heat treatment method of sterilization of food nutrition 、value and taste flavor can produce certain side effects, so in recent years nonthermal sterilization is gaining more and more attention. Nonthermal sterilization of high-voltage Pulsed Electric Field sterilization is a kind of new cold sterilization technology. It has good antiseptic effect due to sterilization processing of short time, low energy consumption and low temperature rise, which makes a high-voltage pulsed electric field sterilization technology becomes a hot research and promotion of food sterilization technology.High-voltage pulse generator of sterilization is mainly composed of charging circuit, discharge circuit and control circuit of three parts. This paper makes a detailed research on the key technology of high voltage pulse power supply for sterilization, such as fast charging, the forming of high voltage sterilization pulse and nanosecond high voltage trigger pulse.A resonant charging circuit, a sterilizing pulse forming network and a nanosecond high voltage trigger pulse forming circuit are designed.In this paper, a charging tube resonant charging method is proposed to charge the pulse forming network.High voltage DC power supply charging the PFN to a predetermined voltage value through the charging tube resonant, and then by controlling the conduction of the hydrogen thyratron make PFN discharge to load, as to obtain the corresponding output pulse on the load, to achieve a change in the voltage waveform and frequency. In this paper, the design method of main circuit and the parameters are calculated in detail, and through Pspice simulation to validate the rationality of the design and parameter calculation.In order to shorten the ignition time of hydrogen thyratron,which can formed the required front edge of high voltage sterilization pulse, the front rate of gate trigger pulse should be increased.This paper design the hydrogen thyratron trigger circuit based on the power MOSFET selection, circuit layout and the choice of the energy storage capacitor. It also analyzes effects of various devices and parasitic parameters on the front rate of output pulse.For linear pulse modulator output pulse width is difficult to regulate a wide range, this paper used respectively connected a hydrogen thyratron in begin and end of PFN. The hydrogen thyratron VE1 connected begining of the PFN as the main switch, hydrogen thyratronVE2 connected end of the PFN to adjust output pulse width. Adjusting the conduction delay of hydrogen thyratron VE2 relative to the VE1 is used to change the final output pulse width,which leads to negative mismatch state of the linear pulse modulator solved by inverse peak circuit.Experimental and simulation results show that the obtained high-voltage pulse which width 1μs-2μs, frequency 500Hz-1000 Hz, pulse front edge under 200 ns and meet the requirements of high pressure sterilization.