Driver circuits for emitter switch gate turn-off SCR devices

An isolated driver circuit for a transistor driven emitter switch including a gate turn-off thyristor (GTO) in series with a bipolar emitter switching transistor, said driver circuit comprising:

• first controllable switch means coupled between the base of the emitter switching transistor and the anode of the GTO, for biasing the emitter switching transistor into conduction and maintaining said emitter switching transistor in a conductive state when said controllable switch means is conducting;
• second controllable switch means coupled across the base emitter terminals of said emitter switching transistor for biasing said emitter switching transistor out of conduction to turn off said GTO;
• third controllable switch means coupled to said first controllable switch means for biasing said first controllable switch means out of conduction when said emitter switch means is biased out of conduction;
• clamp means coupled to the gate of said GTO for clamping the gate of said GTO to a predetermined voltage sufficiently low to protect the emitter switched transistor when said emitter switched transistor is biased out of conduction and said GTO turns off, said clamp means coupled to an external power source;
• isolated switch means coupled to an external control for biasing said first controllable switch into conduction when said isolated switch is energized;
• fourth controllable switch means responsive to said isolated switch for providing a gate pulse to said GTO to turn said GTO on;
• and
• fifth controllable switch means responsive to said isolated switch and coupled to said second and third controllable switch means, said sixth controllable switch means preventing said second controllable switch means from biasing said emitter switching transistor out of conduction and preventing said third controllable switch means from biasing said first controllable switch means out of conduction only when said isolated switch means is conducting.

An isolated driver circuit for a transistor driven power switch including a gate turn-off thyristor (GTO) in series with a bipolar emitter switching transistor, said driver circuit comprising:

• first controllable switch means coupled between the base of the emitter switching transistor and the anode of the GTO, for biasing the emitter switching transistor into conduction and maintaining said emitter switching transistor in a conductive state when said controllable switch means is conducting;
• second controllable switch means coupled to the gate of said GTO for providing a gate pulse to said GTO to turn said GTO on;
• third controllable switch means coupled across the base emitter terminals of said emitter switching transistor for biasing said emitter switching transistor out of conduction to turn said GTO off ;
• fourth controllable switch means coupled to said first controllable switch means for biasing said first controllable switch means out of conduction when said emitter switch means is biased out of conduction;
• clamp means coupled to the gate of said GTO for clamping the gate of said GTO to a predetermined voltage sufficiently low to protect the emitter switched transistor when said emitter switched transistor is biased out of conduction and said GTO turns off;
• an isolated switch;
• fifth controllable switch means coupled to said first and second controllable switch means and responsive to said isolated switch for biasing said first and second controllable switch means into conduction for biasing said emitter switching transistor and said GTO into conduction;
• and
• sixth controllable switch means coupled to said fifth controllable switch means and responsive to said isolated switch for preventing said third controllable switch means from biasing said emitter switching transistor out of conduction and for preventing said fourth controllable switch means from biasing said first controllable switch means out of conduction only when said isolated switch is conducting.