ZERO_CROSSING_HIGH_POWER

Published:2009/7/14 2:07:00 Author:May | From:SeekIC

AC relay uses MFC8070 zero-voltage switch to provide gate current pulses for triac under control of differential input voltages derived from output of 4N28 optoisolator. When LED is off, voltage at pins 1 and 2 of switch is positive with respect to pin 3, inhibiting switch so no current pulses go to mac gate. When LED is energized by logic input, gate current pulses are generated at zero-voltage excursions of AC power source. Transistor ensures adequate gate drive at low temperatures. For normally-on configuration,interchange input connections 3 and 1-2 of switch. Triac can be selected to handle resistive loads from 4 to 40 A.-T. Mazur, Solid-State Relays Offet New Solutions to Many Old Problems, EDN Magazine, Nov. 20, 1973, p 26-32.



Reprinted Url Of This Article:
http://www.seekic.com/circuit_diagram/Basic_Circuit/ZERO_CROSSING_HIGH_POWER.html

Print this Page | Comments | Reading(3)