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555 DC regulated power supply protection device circuit

2015-01-31 20:07  
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555 DC regulated power supply protection device circuit
The protector consists of depressurization regulated power supply, VDD=+(5~12)V, it depends on which voltage stablizing unit is adopted by IC1. The controllable monostable delay circuit is composed of IC2(555) and C4, R3. Ordinarily, due to J1-1 is short connected, when the load is normal, 4 foot level is higher than 1V; when it is short circuit, 4 foot is low level(<0.6V), 555 is in forced reset state, 3 foot is low level, J pulls in, J1-1 is cut off quickly, the short circuit's load is turned off. At the same, J3-3, J2-2 contacts are turned on, the audio frequency feedback type oscillator which is made of VT1, VT2, C6, C7, R6 obtains electricity and oscillates, it sends out about 1000Hz audio. J3-3 is connected, C4 is charged, then 555's 2 foot level is lower than 1/3 VDD, 555 is set, J releases, J1-1 normally closed contact is turned on again.