What is the working principle of the series DC regulated power supply protection circuit?
Second, the cut-off
????? The cut-off type can be improved on the above protection circuit.
????? In the protection of the base of the transistor preset a voltage, such as 0.5 volts, at this time, the protection transistor will be turned on. And then the voltage across the detection resistor is superimposed on the B pole, when the detection resistor detects a voltage higher than 0.2 volts, the two voltages are added, the transistor is fully turned on, the CE is short, the regulator is shorted and the output voltage is approximately 0 , Protection is complete.
???? The cut-off benefit is that you can use a smaller sense resistor to reduce the power loss on this resistor.
First, the current limit
?????? In the circuit back in the middle of a small resistor, such as 1 ohm.
?????? Connect the BE pole of the transistor 9014 at both ends of the resistor. The transistor of the C pole connected to the regulator at the Department.
When the current is greater than the design value (such as 800MA), then the resistance at both ends of the detection voltage of 0.8 volts, higher than 0.7 volts, the protection transistor fully conductive, CE short-circuit, the voltage drop to the transistor saturation voltage drop, The At this point, the regulator is shorted and the output voltage drops to near 0 volts. Protection is successful.
