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555 overvoltage, undervoltage delay automatical protection c

2016-09-23 10:33  
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555 overvoltage, undervoltage delay automatical protection circuit
As shown in Figure 10-3, IC1 and R1 ~ R3, RP1 ~ RP3 form overvoltage, undervoltage sampling and R-S trigger circuit, when the mains voltage is below 170V or above 240V, it will be protected in time, IC1's pin 3 output is in low level, IC2 is forced to reset, J releases, power is cut off. When power is restored, pin 3 of IC1 is in high level, C3 is charged through R5, after td = 1.1R5C3, which is about 6 minutes, pin 2is lower than the potential of 1/3 VDD, IC2 sets , J pulls in, the device gets power.