Design of High-Voltage Square Pulse Generator Based on Cascade Switches and Time-Delay Driver

Abstract

In the application of pulsed-power technology, capacitive loads require that high-voltage pulses have fast front and back edges. Using multiple semiconductor switches, insulated gate bipolar transistors (IGBTs) in series with discharge high-voltage capacitors can generate high-voltage pulses. By adding a group of truncation switches, square pulses with fast back edges can be obtained. A novel drive circuit using many transformers with their primary windings in series is proposed to generate two groups of reverse driving signals by changing the dotted terminals on the secondary sides. The dead time between these signals is realized by adding some time-delay circuits. In terms of drive control, both the discharging switches and the truncation switches are triggered synchronously since the primary windings of all transformers are connected in series, which ensures the synchronism of driving signals. Time-delay drive circuits are added to the secondary sides of transformers to ensure a proper dead time between the two groups of driving signals for both discharging and truncation switches. Moreover, all driving power is provided from the single driver on the primary side, greatly simplifying the drive circuit. The voltage balancing of cascade IGBTs is realized by using resistor–capacitor–diode (RCD) snubber circuits. Experiments were carried out over resistive and capacitive loads. Square pulses with a voltage amplitude of 10 kV, a pulsewidth of $8~\mu \text{s}$ , a rising time of 157 ns, and a falling time of 78 ns were obtained on a 20- $\text{k}\Omega $ resistive load. The voltage amplitude, pulsewidth, and frequency are continuously adjustable.