Study Of Oscillation In High Voltage Diode At Recovery Operation

At present, switching devices such as GCT (Gate Commutated Turn-off) thyristor and HVIGBT (High Voltage IGBT) are remarkably progressing and able to switch fast at high DC operation voltage above 2.5kV. However, a freewheeling diode which should realize the recovery performance similar to the turn-on performance of switching devices is not developed. In the high voltage diode, a main problem of the recovery performance is to prevent the voltage-oscillation. The voltage-oscillation brings miss-operation of driving circuit or voltage destruction of oneself. As the diode during the recovery operation can be regarded as a combination of one capacitance and two resistances, the oscillation mechanism was studied by replacing the diode to LCR circuit. As this results, it was clear that the diode during the recovery operation made surely the oscillation. On the basis of this analysis, the diode structure to mitigate oscillation was proposed.