Semiconductor switch device

A semiconductor switch device comprising:

• a power source;
• a load;
• a semiconductor switch serially disposed in a current path between the power source and the load, the semiconductor switch having a pair of main current electrodes and a control electrode, the semiconductor switch becoming conductive across the main current electrodes when a forward control current is applied to the control electrode;
• a current transformer having a core, a primary conductor serially disposed in the current path and a secondary winding connected to the control electrode whereby a current responding to the current passed through the current path is supplied to the conrol electrode;
• and
• an auxiliary power pulse supply means connected in series with the secondary winding of the current transformer for resetting the flux in the core of said transformer set by said primary conductor by applying a forward polarity pulse to the control electrode to turn on the semiconductor switch and thereby reverse the core flux, the auxiliary power pulse supply means comprising a second power source and a pulse supply switch which is controlled by a control signal to supply the forward polarity pulse through the secondary winding of the current transformer to the control electrode;
• the forward polarity pulse being applied from said auxiliary power pulse souce means through said secondary winding to said control electrode whereby the forward control current is fed to said control electrode and magnetic flux of the core of said transformer is reset by the forward polarity pulse.