Research On High Repetition Rate Solid-State Rectangular Pulse Modulator Technology

High repetition rate is a research hotspot in the field of the pulsed power system technology. In the recent years, high repetition rate pulse power has obtained vast applications in radiographic, high power laser, electromagnetic pulse and shoot, particle beam weapon and other areas and so on.The limiting device in a Pulsed Power System is often the switch, which limits the pulse peak power, rise and fall time, and the repetition rate. The conventional approach in Pulsed Power designs is to use a gas switch such as a thyratron, ignitron or spark gap. However these devices have limited lifetime, high cost, low repetition rate and high losses. Thanks to the continued improvement of the high power semiconductors in switching speed, voltage and current rating, solid-state semiconductors have become the device of choice for pulsed power systems. MOSFET, IGBT, SOS, SIThy, PCSS are the often used solid-state switches. They can be applied to different situation lied on their disparate performances.Since each MOSFET device that has an opening capability is relatively low voltage and low current, inductive voltage adder (IVA) layouts is adopted to take advantage of their capabilities and to achieve high voltage and high current output. The system includes trigger single generator subsystem, multi-channel simultaneous fiber isolation subsystem and IVA subsystem.MCU and FPGA is the logic control core in the generator. The clock frequency of the FPGA is 100MHz, so the minimum logic cycle is just 10ns. The generator can export six simultaneous trigger signal maximum. It can provide 240 simultaneous signals to the adder at most, after transfer by the fiber isolation subsystem.Test has been done under every possible condition about the power MOSFET driver and the power MOSFET itself, eight power MOSFETs parallel connection,1×16 cells inductive adder module.Finally, the modulator is designed composed of four adder modules, and every module has 16 parallel MOSFETs. The device obtains a pulse output of 179.6ns width, rise time of 29.04ns, fall time of 42.67ns, and 3.26kV peak voltage.