直流高压发生器设计中的四个关键问题

Four Key Problems in the Design of a DC High Voltage Generator

为了解决基于开关电源技术的直流高压发生器研制中的关键问题,分别介绍了系统方案设计、开关管驱动电路、缓冲电路和高频升压变压器设计4个关键技术。系统主要由功率部分和控制部分组成,前者用高频逆变和倍压整流的方案,后者采用MCU和CPLD结合的架构;开关管MOSFET驱动电路用A316J实现;RCD网络实现缓冲电路的设计;多槽排绕的方式绕制高频升压变压器。调试结果表明,开发出120kV、5mA输出的直流高压发生器可满足现场试验要求。

Four key problems of DC high voltage generator which uses the technology of switching power supply are introduced. The four key problems are listed below： design of the whole project, drive circuit for MOSFET, RCD snubber and the design of high frequency boost transformer. The whole system includes two sections： power section and controlling section. The power section is based on the technology of high frequency inverter and voltage multiplier circuit. The controlling section works with the combination of MCU and CPLD. A316J is used to design drive circuit for MOSFET. A316J , a kind of drive chips from Agilent company, can connect with MCU or CPLD conveniently. The drive circuit based on A316J has strong drive ability which can turn on or shut down MOSFET within 200 nanoseconds. It can also shut down MOSFET with negative voltage which can avoid short circuit. RCD snubber is applied to protect MOSFET and lower electro magnetic interference（EMI） The parameters of RCD snubber are calculated in detail and adjusted through experiments. Multitrough framework is used to make high frequency boost transformer in order to increase efficiency. Multitrough framework can decrease parasitic capacitance which is the main factor causing wastage of energy. The windings of the transformer are imbued with epoxy glues to enhance the capability of insulation. In the debugging process, full load test and 1.1 times output voltage test have been implemented. The debugging results shows that the 120kV/5mA high voltage generator based on the technology introduced above can work reliably now.