High-repetition-frequency Mosfet Pulse Modulation Techniques

Solid state modulator with multi-pulse burst capability in mega Hertz, fast rise and fall times and width agility is the hotspot of pulse power technology. In this paper, the base principle and designing method of the solid state modulator based on power MOSFET devices are introduced. The prototype of the modulator is introduced and the experimental results are given.The whole solid state modulator was composed of control system, power supply supplemental system, switch circuits, and the load. The kernel hardware of control system was composed of Micro Control Unit (MCU) and Complex Program Logic Device (CPLD). It could generate trigger signal with shortest pulse width of 12.5ns for the driver circuit of power MOSFET, and it also had good performance in multi pulses situation. Optical association circuits were used to protect the control system against the high voltage of the switch circuits.Two types of driver circuits were designed according to the principle of power MOSFET. One was designed by separated components and the other was by integrated driver chip. Circuit simulations were used to help to analyze the experiment results. The reasons of cross talk in print circuit board were analyzed and improving ways were given. Power supply for driver circuits was designed by DC/DC modules which could work in series connection mode.After the experiments of Single MOSFET switch, the switch with six MOSFETs parallel connecting and switch with four MOSFETs serial connecting were separated tested. Circuit simulations were also done to improve the experimental results.The adder configuration was chosen to set up the prototype modulator for the adder topology had many advantages than the direct serial method. The adder transformers were designed and tested.The modulator finally designed composed of three adder modules. The single pulse with shortest pulse width of 33.8ns, rise time of 13.9ns, amplitude of 2.2kV was obtained under charging voltage of 800V. Good experiment results were also got in multi pulses output mode.