| 摘要 |
PURPOSE:To protect a power transistor with good reponse by utilizing a control signal for periodically turning the transistor ON and OFF and performing a function of a protecting circuit only during the period while the transistor is controlled to ON. CONSTITUTION:When an inverter is normally operated, the output of a comparator CP2 is ''high'', while the output of a comparator CP1 is ''low'', and a thyristor SCR is interrupted. A power transistor Q1 is controlled to be ON and OFF in accordance with the ON the OFF of an auxiliary transistor q1 in this state. When an over current flows with the transistor Q1 being ON so that the terminal voltage of a resistor R exceeds the set value, the output of the comparator CP1 becomes ''high'', and the thyristor SCR is conducted. Accordingly, the transistor Q1 is turned OFF This protecting state is connected while a control signal S1 applied to the base of the transistor q1 is ON control time. |
