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The over voltage/current protection circuit

2016-09-17 03:36  
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The over voltage/current protection circuit
When the voltage of the power supply is too high or the load attracts too much current, the circuit in the figure can break down the load and offer fault indication. When it is normally working, both Tr1 and Tr2 are blocked, 555 is reset, the discharging transistor in 555 is conducting, it attracts power from Tr3 basic pole, which saturates Tr3, so the 5~12V power supply is sent to the main load directly. When the load gets too much current, the voltage drop on Rsc increases, which makes Tr1 conducting, so 555 is triggered and the discharge transistor in it is blocked, then Tr3 is blocked with it, the power supply and load are separated, at the moment, 555 is in single steady state.