PROBLEM TO BE SOLVED: To provide a photo coupler interface circuit capable of being protected from the over-voltage applied from outside, with simple structure.;SOLUTION: When a short-circuit malfunction is generated on a signal line L1 connecting a first terminal T1 and a second terminal T2 and the over-voltage is applied to the signal line L1, a protecting diode DB connected between the second terminal T2 and a photo-coupler C in a driven side circuit B prevents the generation of a reverse voltage in the photo-coupler C. When the driving transistor SW of a driving side circuit A is turned off, current does not flow onto a ground G from the signal line L1 through the driving transistor SW. When the driving transistor SW is turned on, the short-circuit current ILA flows onto the ground G through the driving transistor SW, the short-circuit current ILA being limited by the protecting resistor R2 connected in series between the first terminal T1 and the driving transistor SW.;COPYRIGHT: (C)2007,JPO&INPIT
展开▼
