A Pulsed Power Supply Based on Power Semiconductor Switches and Transmission Line Transformer

Abstract

Transmission line transformers (TLT's) as pulse transformers have received increasingly more attention due to their excellent frequency response characteristics over conventional wound transformers. This transformer basically consists of equal lengths of transmission line (normally coaxial cables are used) connected in parallel at the input side of the transformer, and in series at the output side so that the output voltage can be boosted in proportion. Because the reactance of the outer conductor increases with the rise of the frequency of the input voltage, the output voltage of each transmission line can be isolated mutually when the frequency is high enough. Then, the output voltage will be amplified through the voltage superposition. To minimize the substantial loss of voltage gain and obtain a low pulse droop rate, one stage transformer is entwined together as a unit, the number of stages of the transformer can increase easily by piling units one by one. This spiral construction makes the transmission line transformers much more compact. On the other hand, with the development of modern semiconductor technology, high voltage, fast rise time power semiconductor devices have been produced, the collector emitter breakdown voltage of one IGBT is to 1.7 kV and the rise time is 100 ns. This paper describes a kind of compact pulse power supply constructed by combining transmission line transformer and modern power semiconductor devices-IGBTs. High voltage IGBTs (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CES</sub> =1.7 kV) have been used as charge switches, short pulses can be obtained at the input port of the transformer, then the output pulse amplitude is 10 kV through a 10-stage transmission line transformer. Finally, the output voltage pulse waveforms are given in the paper.