Protection power circuit diagram

LC03-3.3 SOP8 TVS Static Protection 3.3V

Protection power circuit

As shown in the figure, when the circuit works normally, the seventh pin of NE555 outputs low level, VT3 turns on saturation, and the power supply supplies power to the load through VT3. Both VTl and VT2 are off.
When the power supply voltage exceeds the allowable range, the voltage divider DW breaks down through the voltage division of R5 and RP. At this time, VT2 is turned on, and the output low level is applied to the second pin of NE555, so that the seventh pin of NE555 is made. The output is high, VT3 is cut off, the power supply is cut off, and the load stops working.
When the load current exceeds the allowable value, the current flowing through R7 forms a large voltage drop. At this time, VTl will be turned on, and the low level of the collector output is applied to the second pin, so that the output of the seventh pin of the NE555 is high. Level, VT3 cutoff stops supplying power to the load. Capacitor C3 acts as a delay. When VTl or VT2 is turned on, the circuit does not start up immediately. Instead, it is first discharged by C3 through the conducting tube until the voltage on C3 is lower than Voo /3. Only to control.