Tomoyuki Yokoo

Repetitive Pulsed High-Voltage Generator Using Semiconductor Opening Switch for Atmospheric Discharge

Atmospheric pulsed gas discharge requires very short duration high-voltage pulse delivered to the electrodes. Moreover, atmospheric gas discharge of very short pulse is usually a high impedance load. Pulsed power technology based on inductive energy storage (IES) is suitable for this application. In this paper, we present a repetitive pulsed high-voltage generator with IES. It uses semiconductor opening switch, combined with magnetic switches and insulated-gate bipolar transistors. Experimental tests were carried out with 30-cm-long plate-to-knife discharge load. An output voltage of ~ 50 kV with a pulse duration of ~10 ns was obtained for a gap distance of 1 cm in air. The generator has been operated at a repetition rate up to 250 Hz. Uniform discharge plasma has been identified.

Compact pulsed power and its industrial applications

Repetitive pulsed power generation by compact sources is being studied for industrial applications. The research efforts include pulse-compression concept exploration, electrical circuit design and optimization, switching device development and evaluation, and application demonstrations. The basic strategy is to take advantage of solid-state switching devices to achieve compactness, reliability, and high repetition rate of pulsed power systems operating in both capacitive and inductive energy-storage schemes. These solid-state switches include saturable inductors, saturable capacitors, photoconductive semiconductors, and other power semiconductor switching devices, such as MOSFET, IGBT, SiC-FET, and SI-Thyristor.

Repetitive Pulsed Power Based on Semiconductor Switching Devices

Static induction thyristor and silicon-carbide junction FET have been studied for applications to high-voltage modulators that are demanded by a new type of high-energy particle accelerator, the induction synchrotron. The switching characteristics of these power semiconductor devices are evaluated in order to assess their applicability to MHz level repetitive operation.

Pulsed-power switching by power semiconductor devices

Summary form only given. Repetitive pulsed high-voltage modulators have been developed for industrial applications. They have used the most up-to-date power semiconductor devices such as power MOSFETs, silicon carbide JFETs, static-induction thyristors (SIThy), and semiconductor opening switches (SOS). As a new kind of high-energy particle accelerator, induction synchrotron requires pulsed high-voltage modulators with repetition rate on the order of 1 MHz. A test unit of stacked MOSFET has been successfully developed and tested for continuous operation. In the same time, SIThy and SiC-FET are also investigated for their performance as potential substitutes to MOSFET. A pulsed high-voltage generator using SOS has been developed for applications in sterilization. It consists of a primary unit which is switched by an IGBT and a secondary unit where two magnetic switches and an SOS are used. A pulse transformer is used to multiply the voltage between the two units. The output voltage pulses are of 60 kV in peak value and 50 ns in pulse width, with continuous repetition rate of 1 kHz

MHz pulsed power by semiconductor devices

Pulsed power generators with repetition rates on the order of MHz have been developed by using semiconductor opening switch (SOS), static induction thyristor (SIThy), and silicon carbide junction field-effect-transistor (SiC-JFET). A compact SOS circuit based on inductive energy storage has been developed. It uses semiconductor switches for forward and reverse current control of the SOS diodes, instead of commonly used magnetic switch. The repetition rate has reached 500 kHz (burst) for output voltage pulse of 10 kV and pulse width of 15 ns (FWHM). A full-bridge switching unit using SIThy has been developed and tested for bipolar square voltage pulse generation of plusmn 2 kV for a 100-Omega load, at repetition rate of 1 MHz (burst). A stacked SiC-JFET switching unit consists of 4 devices (2S x 2P) has been operated for 2 kV and 20 A at repetition rate up to 5 MHz (burst). Important issues on switching characteristics, such as rise- time, heat loading, and balance between devices have been studied. The MHz-repetitive power modulators are expected to have various applications in the future, especially for high- energy accelerators and biological treatment.

Development of nanosecond repetitive pulsed high voltage generator using semiconductor opening switches for atmospheric discharge

Summary form only given. Nanosecond repetitive pulsed high voltage generator is successfully developed for atmospheric pressure pulsed discharge applications. This generator employs an inductive energy storage scheme with SOS (semiconductor opening switch) at the output of generator to sharpen and multiply the output voltage at high repetition rate. The SOS is specially designed semiconductor diode for using as an opening switch. It has a semiconductor p+-p-nn+ structure and is fabricated to obtain a super hard reverse recovery at large reverse current of what is called SOSeffect. The SOS-60-4, which is an assembly of 80 SOS diodes connected in series to obtain withstand reverse voltage of 60 kV, is used in the present systems. It is able to conduct and interrupt high reverse current (up to 4 kA) in very short time (less than 15 ns). To provide forward and reverse current to the SOS at the high repetition rate, MCP (magnetic pulse compression) circuit and IGBT (insulated gate bipolar transistor) is also employed in the present system. The forward and reverse current pulse width is set to be 400 ns and 100 ns, respectively. As a load, a copper plate-edge discharging gap is used. This discharging gap has a length of 30 cm. The gap distance is 1 cm. The tests was carried out and peak forward current of 90 A, peak reverse current of 380 A were obtained respectively. In these results, peak output voltage of 95 kV, voltage rise time of 30 ns and pulse width of 50 ns were respectively obtained at the discharging gap load at 100 Hz repetitive operation. Streamer like discharges were identified at the load