A New High Speed Pulse Generators for Automotive Gas Treatment Application

This paper proposes two new structures of high speed pulse generators for automotive gas treatment application. The rising time of output voltage waveform is important factor to increase NOx removal efficiency in pulsed corona discharge method and in the automotive application, the manufacturing cost and compactness of the pulse power generator should be satisfied. Type I uses one pulse transformer with one turn in primary side and several turns in secondary side for high voltage. This type is compact but because of its high leakage inductance, the rising time of pulse waveform is a little slower compared to type II. Type II has one turn transformer at the primary and the secondary side. Since the number of turns of the pulse transformer is only one, the leakage inductance is very low. This type gets very fast rising time. For high voltage output in type II, the modules are stacked in series at output side. The switches used in the type I are thyristors and in the type II are MOSFETs. The system efficiency of the type II is higher than that of type I pulse generator. In the all types, the characteristics of the high speed opening switch is achieved using general commercial diodes not using special switches like SOS diodes, thyratron, etc. In the type I, with 200 resistor load, the experiment results show that the output voltage is 21 kV, the rising time is about 21 ns, and the pulse width (FWHM) is about 42 ns. In the type II, the output voltage is 2.35 kV with rising time of 7.5 ns with charging voltage of 700 V and 8.6 Omega load. In four modules which have series connected outputs with the same input voltage and 13 Omega load, The output voltage is obtained 8.17 kV with rising time of 7.7 ns. The repetition frequency is 1000 pps