| 摘要 |
PURPOSE:To control large capacity current without adding an external adding element by inserting a diode on the way of a positive feedback loop of two transistors(TRs) constituting a gate turn off thyristor. CONSTITUTION:A diode D is inserted between the base of an npn TR Q1 and the collector of a pnp TR Q2. In the figure, IA and IK show anode and casode current of the gate turn off (GTO) thyristor respectively. By connecting the diode, the TR Q1 shows high impedance at the time of turn off and about 1.4V negative bias is applied to the gate because of the voltage drop of the diode D and the TR Q1, so that branched current I2 is reduced, the gate is turned off speedily and current to be used for on and off is increased. Since a current amplification factor alphanpn is generally larger than alphapnp, it is unnecessary to make alphanpn.IK flow and the GTO thyristor can be constituted by the diode with a small current capacity as compared to the case that the diode is externally connected between the cathode side of the GTO thyristor and the earth. |
