GTO turn-off circuit providing turn-off gate current pulse proportional to anode current

Claim 2

A solid state circuit including a semiconductor device with a gate turn-off circuit comprising a gate turn-off thyristor semiconductor device having an anode and a cathode and a gate terminal for controlling switching of said device between a conducting state in which anode current flows and a nonconducting state, said gate turn-off thyristor being coupled to a pair of unidirectional input voltage supply lines between which is applied an energizing voltage, and turn-off circuit means for selectively generating a ramped turn-off gate current pulse with a peak magnitude which increases and decreases as said anode current increases and decreases, said turn-off circuit means being comprised by a transformer having a primary winding connected in series with a controlled solid state switch device between said gate terminal and a negative unidirectional gate voltage supply line, and means for rendering conductive said controlled solid state switch for a selected interval to initiate generation of said gate turn-off current pulse, said transformer having a secondary winding connected in series with a diode and comprising means for returning excess energy stored in said primary winding to a selected voltage supply.

Claim 3

A solid state circuit according to claim 1 wherein the selected voltage supply to which the excess energy is returned is the gate voltage supply, and said transformer secondary winding and series-connected diode are connected between said negative gate voltage supply line and one input voltage supply line coupled to the cathode of said device.

Claim 4

A solid state circuit according to claim 2 further including means for supplying turn-on pulses to the gate terminal of said device.

Claim 5

A solid state circuit including a semiconductor device with a turn-off circuit comprising a gate turn-off thyristor semiconductor device having an anode and a cathode and a gate terminal for controlling switching of said device between a conducting state in which anode current flows and a nonconducting state, said gate turn-off thyristor being coupled between a pair of input voltage supply lines between which is applied an energizing voltage, and turn-off circuit means for selectively generating a ramped turn-off gate current pulse with a peak magnitude which increases and decreases as said anode current increases and decreases, said turn-off circuit means being energized by a pair of constant unidirectional gate voltage supply lines and including a first transformer having a primary winding connected in series with a controlled solid state switch and the primary winding of a second transformer between said gate voltage supply lines, and means for rendering conductive said controlled solid state switch for a preselected interval to initiate generation of said turn-off current pulse, said second transformer having a secondary winding connected between said gate terminal and cathode to couple said turn-off current pulse to said gate terminal, said first transformer having a secondary winding connected in series with a diode and comprising means for returning excess energy stored in said first transformer primary winding to a selected voltage supply.

Claim 6

A solid state circuit including a semiconductor device with a turn-off circuit comprising a gate turn-off thyristor semiconductor device having an anode and a cathode and a gate terminal for controlling switching of said device between a conducting state in which anode current flows and a nonconducting state, said gate turn-off thyristor being coupled between a pair of input voltage supply lines between which is applied an energizing voltage, and turn-off circuit means for selectively generating a ramped turn-off gate current pulse with a peak magnitude which increases and decreases as said anode current increases and decreases, said turn-off circuit means being energized by a pair of constant unidirectional gate voltage supply lines and including a first transformer having a primary winding connected in series with a controlled solid state switch and the primary winding of a second transformer between said gate voltage supply lines, and means for rendering conductive said controlled solid state switch for a preselected interval to initiate generation of said turn-off current pulse, said second transformer having a secondary winding connected between said gate terminal and cathode to couple said turn-off current pulse to said gate terminal, said first transformer having a secondary winding connected in series with a diode and comprising means for returning excess energy stored in said first transformer primary winding to a selected voltage supply.

Claim 7

A solid state circuit according to claim 4 wherein the selected voltage supply to which excess energy is returned is the gate voltage supply, and said first transformer secondary winding and series-connected diode are connected between said gate voltage supply lines.