VOLTAGE DETECTION CIRCUIT, DRIVE CIRCUIT AND FAILURE DETECTION CIRCUIT FOR THYRISTOR

摘要

PURPOSE: To reduce the cost by decreasing the number of light emitting elements and optical fibers. ;CONSTITUTION: When forward voltages higher than the clamp voltages of Zener diodes 70, 71 is applied to thyristors 10, 11, a current depending on the clamp voltage flow into an LED 20 which produces light in proportion to the current. The light is transmitted on a signal optical fiber 30 to an optoelectronic converter (O/E) 40 which produces a voltage detection signal. A level decision circuit 80 compares the voltage detection signal with two kinds of decision level 1, 2. When only one thyristor is applied with a forward voltage, only a voltage presence signal 1 goes high but when two thyristors are applied with forward voltage, a voltage presence signal 2 goes high. Consequently, a failure detection circuit 61 can decide whether the thyristor 10 or 11 is faulty based on the voltage presence signals 1 and 2.;COPYRIGHT: (C)1996,JPO