Research On High Power Solid State Pulse Modulator Based On IGBT

This paper aims at the increasing demand for power supply system,i.e.high-power pulse modulator,in the fields of radar transmitter,klystron and gyrotron,vacuum electron tube,metallurgical chemical industry,high-voltage dust removal and medical application,a high-power pulse modulator based on IGBT with asynchronous signal trigger and gate discharge circuit is designed.Traditional high-power pulse modulators usually adopt linear direct series mode and use hydrogen thyratron as switch.They have the shortcomings of serious heating,huge volume,high synchronization requirement of modulation signal,long delay of pulse front and back edge,serious overshoot and weak fault tolerance.With the continuous development of electronic technology,the research direction of high-power pulse modulator is toward the direction of small size,high efficiency,steep front and back edge of pulse waveform,flat bottom of waveform and so on.Therefore,this paper studies the high power modulator as follows:A new IGBT solid-state switching device is used to replace the huge hydrogen thyratron.The parameters of IGBT are analyzed and spice model is established for simulation.In view of the serious shortcomings of traditional modulator HVDC power supply,UC3875 control signal circuit and drive circuit are designed.Phase-shifted full-bridge zero-voltage switching pulse width modulation technology is used to control full-bridge power supply conversion circuit with auxiliary current network to reduce switching losses and improve efficiency.Selecting 20 kHz switching signal to avoid the use of power frequency transformer leading to larger modulator volume.The modulator designs a low frequency to high frequency signal processing circuit to convert the long pulse modulation signal to high frequency signal,which is suitable for transformer isolation transmission and modulation switch driving gate circuit.A pulse forming circuit with superposition structure is used to increase the fault tolerance of the circuit.Because of the independent working characteristics of the switch,a modulation signal delay circuit is designed,which consists of 25 signals,divided into five groups.The opening time delay between each group of signals can effectively reduce the pulse front overshoot.Pulse forming circuit switch driver gate circuit adds gate truncation pulse discharge circuit,which makes the gate charge release quickly when the switch is off,and the switch switch switch is switched off quickly,which makes the back edge of the pulse steep.The high-power pulse modulator based on IGBT described in this paper has been optimized by simulation and verified by experiments.The final design parameters are: output voltage 0~-20 kV continuously adjustable,current 0~2A,pulse width 25us~400us adjustable,repetition frequency up to 200 Hz.Its output waveform is steep in front and back,no obvious overshoot and flat in bottom.It is completely suitable for high power pulse modulation power supply used in electronic vacuum tube.