4_A_FULL_WAVE_CONTROL

Published:2009/7/14 1:42:00 Author:May | From:SeekIC

When logic input to CMOS buffer goes high, load is off. Low input logic deenergizes optoisolator; clamp formed by bridge rectifier and SCR is then removed from C1, allowing it to charge through R1. When voltage across C1 reaches triggering voltage of S1 (about 8 V), MBS4992 silicon bidirectional switch fires, allowing C1 to dump charge into gate of triac. Triac and load are then turned on.R1 and C1 are chosen to give time constant small enough to fire triac early in its conduction angle (near zero crossing), to maximize load power while minimizing EMI.-A. Pshaenich, Interface Techniques Between Industrial Logic and Power Devices, Motorola, Phoenix, AZ, 1975, AN-712A, p 17.



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