| 摘要 |
PURPOSE:To prevent breakage of semiconductor switching element by a method wherein a circuit, impressing the generating output of another polarity of a charging coil to a control pole, is opened when a current flowing through the control pole of the semiconductor switching element for ignition becomes higher than a predetermined value. CONSTITUTION:When the gate current of a thyristor 10 is increased, the voltage drop of a circuit series with a transistor 17 is increased and the voltage of a connecting point (b) is increased. When this value arrives at a set value, the thyristor 19 is conducted and short-circuits between the base emitters of the transistor 17, therefore, the transistor 17 is put OFF and the supply of the gate current from a charging coil 3 to the thyristor 10 is interrupted. According to this method, the supply of excess gate current to the thyristor 10 may be precluded and the breakage may be prevented. |
