SHORT CIRCUITE DETECTION AND DISPLAY CIRCUIT

摘要

PROBLEM TO BE SOLVED: To solve a problem of display misinterpretation caused by blinking of a short circuit display element in normal time by a ripple voltage of a D.C. power supply while stably securing an original short circuit display function. SOLUTION: This short circuit detection and display circuit is so structured that the output of a zero-phase current transformer 2 interlaid in a main circuit 1 is inputted to a ground leakage detection circuit 2 and the short circuit display element 14 is lit by its output signal. The circuit comprises: an output circuit 7 including a switching element 9 turned on by the output signal of the short circuit detection circuit; a snubber circuit 10 connected in parallel with the switching element; and a short circuit display circuit 13 composed by connecting a current limit resistor 18 in series to the display element 14; and is supplied with D.C. output obtained from an A.C. power source 4 through a rectifying circuit 5 and a smoothing capacitor 6. A zener diode 18 having a zener voltage corresponding to a ripple voltage superimposed on the D.C. output is connected in series to the short circuit display element to reduce a current flowing through the short circuit display element in a normal time, so that its blink is prevented from being viewed. COPYRIGHT: (C)2005,JPO&NCIPI