| 摘要 |
PROBLEM TO BE SOLVED: To generate a turn-off pulse with only one UJT by connecting a R-C circuit of the UJT to the cathode of a thyristor and connecting the base to a turn-off commutation circuit of the thyristor. SOLUTION: In a R-C circuit of a turn-off UJT 26 of a thyristor 13, a variable resistor 24 is used. A contact 29 between the variable resistor 24 and a capacitor 30 is connected to the emitter of the UJT 26, and the other terminal of the capacitor 30 is connected to a minus side 7 of a power supply. The base 27 of the UJT 26 is connected to the minus side 7 of the power supply through a resistor and the base is connected to a terminal 23 of the variable resistor 24 through a resistor and then to the cathode 15 of the thyristor, The base 31 of a turn-off UJT 1 for general use is connected to a transistor 12 of a turning-off transistor circuit, and the base 27 of the UJT 26 is connected to a transistor 20 of a turn-off commutation circuit of the thyristor, Due to this structure, a turning-off operation can be conducted with only one UJT. |
