| 摘要 |
PURPOSE:To prevent destruction of a conduction modulation type self turn-off element by controlling a gate current so that a gate current waveform is not crossing an anode current waveform while an anode current or the like is detected when the element is turned off. CONSTITUTION:A gate bias controller 3 devises that a gate current waveform at turn-off is not in crossing with a tail current waveform based on data obtained from an anode current detector 4, a gate current detector 5, a gate voltage detector 6 and an anode voltage detector 7 or the like. That is, the gate current controller 3 uses the result of detection of the detectors 4, 5 to compare a gate current with an anode current Io being a multiple of a prescribed ratio (k) and controls a gate bias power supply 2 so that the gate current is not less than kIo or below. Thus, the crossing of the gate current waveform with the tail current waveform is prevented and destruction of a GTO thyristor 1 is prevented. |
