拉开时序下脉冲成形网络中半导体器件的击穿与保护

为了让电磁轨道内的电枢获得均匀加速，脉冲成形网络（PFN）通常采用多个脉冲成形单元（PFU）拉开时序放电的工作模式，以输出平顶电流波形。此时，PFU内的续流二极管可能会承受很高的反向恢复电压而损坏。通过对二极管反向恢复过程以及PFN电路特性的分析，提出了一种通过避 免负载上出现反向电压的方法来消除半导体开关器件损坏的隐患，并推导出避免出现反向电压的参数匹配公式。将该匹配公式应用在一套由8个75 kJ模块组成的600 kJ储能的PFN电源参数设计中。该电源系统通过控制放电时序生成了近似平顶的电流波形，且系统工作稳定，无半导体开关器件损坏现象。实验结果表明，通过合理的负载参数匹配，可以降低甚至消除二极管上的反向过电压。

Breakdown and Protection of Semiconductor Device in a Sequentially Fired Pulse Forming Network

In military applications, pulse forming network (PFN) needs to generate a flat-top current waveform by sequentially firing pulse forming units (PFUs) for the uniform acceleration of armature. However, when PFN works under this condition, a fly-wheel diode in PFN withstands a high reverse recovery voltage which may cause the failure of the fly-wheel diode. An approach in which the damage of semiconductor device can be eliminated by preventing from the reverse voltage is proposed through the theoretical analysis of reverse recovery process of diode. The mathematical expression of the proposed approach is derived from the equations of PFN circuit. This expression is used to calculate the parameters of a 600 kJ pulse power supply (PPS) constituted of 8 individual 75 kJ PFN modules. The PPS successfully generates an approximate flat-top current waveform without device damage. The test results show that the reverse recovery voltage can be eliminated by selecting proper circuit parameter.