Over-voltage automatic power off device

Published:2011/9/5 21:32:00 Author:TaoXi | Keyword: Over-voltage, automatic, power off device | From:SeekIC

The circuit principle is as shown in the figure. The 220V city electricity supplies the stable 12V operating voltage to the switch integrated circuit through the C1, VD1 and DW1, the partial voltage sampling circuit is composed of the VD3, R2 and RP1. When the city electricity voltage is normal, the DW2 can not conduct, the operating voltage of the TWH8778's pin-5 is lower than 1.6V, the relay J will not close, the city electricity supplies power to the socket CZ through J－1; when the city electricity voltage is higher than the normal value, the DW2 is conducted, the electric potential of the TWH8778's pin-5 rises to 1.6V, the IC turns, the pin-3 outputs the high level, the relay closes, the power supply of the electrical appliance is cut off to avoid the damage.



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