| 摘要 |
PURPOSE:To supply a hold current by cascading a transistor (TR) to which a diodes is connected reversely in parallel and a thyristor, performing switching between the base and gate terminals by utilizing the leak current at the base, and forming a thyristor loop. CONSTITUTION:The electric power from a power source AC is rectified on full- wave basis by a diode bridge BR and smoothed by a capacitor C1. Then, a TR- cascaded thyristors TR to which the diode is connected reversely in parallel, a TC, and a switch SW are connected so as to interrupt the smoothed DC voltage passed through a load L. A capacitor C9 and a connection resistance R9 are connected to the SW to constitute the capacitor thyristor loop. When the SW is turned on and off, a rush current is generated by utilizing the charging and discharging currents of the C9. This current is limited by the R9 and pulse transformer M. Thus, the capacitor thyristor loop utilizing the leak current of the base of the TR is formed and a bias voltage is applied to a terminal T2 and terminal G to trigger and turn on the thyristor TC. |
