| 摘要 |
PURPOSE:To simplify the constitution of the titled drive circuit and to protect assuredly a power transistor by detecting the collector-emitter voltage by a voltage dividing circuit and leading the voltage directly to a logical circuit. CONSTITUTION:Resistances R1 and R2 detect the collector-emitter voltage of a switching transistor TR10 to be controlled. Thus a binary level of Lo or Hi is obtained. Then the binary signal which varies its level in response to the control signal supplied from a photocoupler 2 is delayed 3 by a period of time longer than the switching time of the TR10 and during which the transistor has no breakdown. Here logical circuits 4 and 5-7 flow a base current to the TR10 after a prescribed period of time elapses only when a control input is available to turn on the TR10 with the detection signal set higher than a prescribed level. While the base current is supplied to the TR10 for a prescribed period of time in case the control signal is inverted to ON from OFF with the detection signal set at a level Hi higher than the prescribed level. Then the TR10 is cut off. |
