Pulse Generator with an Individual Power Supply per Stage

High-voltage pulses with a stepwise arbitrary waveform can be generated by switching the stages of a pulse generator individually according to a pre-defined switching
sequence for each stage. Thereby, the individual stage voltages depend on the initial charging voltage and the discharge rates of the stage capacitors, which vary with the on-time of the stage switches and the related discharge currents. While a parallel configuration of the stage capacitors during charging results in the stage capacitors to be charged to an almost equal voltage at the beginning of the pulse, the individual control of the charging voltage at each stage allows for a more precise adaptation of the
voltage steps and, hence, the generator's output voltage. For initial tests, a four-stage pulse generator featuring an individual power supply per stage has been set up. The energy is transferred to the stages via transformers. Its primary windings are connected in series configuration to form a loop, which is powered by an AC current source at a frequency of approximately 100 kHz. The energy flow to the stages is controlled by means of a shunt regulator. Each stage is equipped with a pulse capacitor of 55 μF,
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which can be charged individually up to a voltage of 800 V per stage. The stages are designed to generate a pulse current of up to 90 A. Thereby, a pulse generated by a single stage connected to a resistive load has a rise time of less than 5 ns. The pulse switch of each stage features three SiC-MOSFETs in parallel configuration operated under gate-boosting conditions in order to achieve a fast rise time. The stages are controlled via a fiber-optic link. In the contribution selected design details and measurement results from tests of generating pulses having a rectangular voltage shape will be presented.